HomeMy WebLinkAboutRS_Technical Information Report_251208_APPROVED.
Solera Phase 2:
Block C & D
Site Plan Review
Technical Information Report
December 2025
condition of approval:
provide declaration of covenant (doc) under separate cover for on-site bmps
draft shall submitted to development engineering project manager for review
and approval prior to project closeout
DEVELOPMENT ENGINEERING
HBray 12/31/2025
Surface Water Enginering
jfarah 12/31/2025
Solera Phase 2: Block C and Block D – New Home Co.
i
Drainage Report
December 2025
Prepared for:
New Home Co.
1700 NW Gilman Blvd, Suite 220
Issaquah, WA 98027
Prepared by:
Jeremy Febus, PE
KPFF Consulting Engineers
1601 Fifth Avenue, Suite 1600
Seattle, WA 98101
(206) 622-5822
KPFF Project No. 2400283
12/09/2025
KPFF Consulting Engineers
ii
Table of Contents
1. Project Overview .......................................................................................................................................... 1
2. Existing Conditions and Drainage ............................................................................................................. 1
3. Proposed Conditions and Requirements Summary ................................................................................. 2
Core Requirement No. 1: Discharge at the Natural Location ....................................................................... 3
Core Requirement No. 2: Offsite Analysis .................................................................................................... 3
Core Requirement No. 3: Flow Control ......................................................................................................... 3
Core Requirement No. 4: Conveyance System ............................................................................................ 3
Core Requirement No. 5: Construction Stormwater Pollution prevention .................................................... 3
Core Requirement No. 6: Maintenance and Operations ............................................................................... 3
Core Requirement No. 7: Financial Guarantees and Liability....................................................................... 3
Core Requirement No. 8: Water Quality ....................................................................................................... 4
Core Requirement No. 9: On-Site BMPs ...................................................................................................... 4
Special Requirement No. 1: Other Adopted Area-Specific Requirements ................................................... 4
Special Requirement No. 2: Flood Hazard Area Delineation ........................................................................ 4
Special Requirement No. 3: Flood Protection Facilities ................................................................................ 4
Special Requirement No. 4: Source Control ................................................................................................. 4
Special Requirement No. 5: Oil Control ........................................................................................................ 4
Special Requirement No. 6: Aquifer Protection Areas .................................................................................. 4
4. Off-Site Analysis .......................................................................................................................................... 5
Upstream Analysis ......................................................................................................................................... 5
Downstream Analysis ..................................................................................................................................... 5
5. Flow Control Analysis and Design ............................................................................................................. 5
6. Water Quality Analysis and Design ............................................................................................................ 5
7. On-site BMPs ................................................................................................................................................ 7
8. Conveyance System Analysis and Design ................................................................................................ 7
9. ESC Analysis and Design............................................................................................................................ 7
10. Special Reports and Studies ...................................................................................................................... 7
11. Bond Quantities and Declaration of Covenant ......................................................................................... 8
List of Figures
Figure 1-1: Site Map ............................................................................................................................................ 1
Figure 2-1: TDA Map ........................................................................................................................................... 2
List of Tables
Table 5-1: On-Site Area Summary ...................................................................................................................... 5
Table 5-2: MGSFlood Peak Flow Rate with 15-Minute Time Step ...................................................................... 5
Solera Phase 2: Block C and Block D – New Home Co.
iii
Appendices
Appendix A – TIR Worksheet
Appendix B – Existing Conditions Map
Appendix C – Proposed Conditions Map
Appendix D – Peak Flow Control Application Map
Appendix E – Water Quality and On-Site BMP MGS Flood Bioretention Calculations
Appendix F – Pipe Conveyance
Appendix G – Erosion Control Plan and Details
Appendix H – SWPPP
Appendix I – Bond Quantity Worksheet
Appendix J – Operation and Maintenance Manual
Appendix K – Geotechnical Report
Appendix L – Infiltration Test Report
Appendix M – Infiltration Test Report Memorandum
Appendix N – Preliminary Plat Drainage Report
Solera Phase 2: Block C and Block D – New Home Co.
1
1. Project Overview
This report has been prepared in support of the Civil Construction Permit for development of the final 2 blocks
of the Solera Short Subdivision. Throughout the history of the project, these blocks have been referred to as
“Block C” and “Block D”, and for the purposes of this report and in communication with the City, we will
continue to refer to the development areas by these names. On the recorded final plat, these blocks are
referred to as “Parcel 4” and “Parcel 3”, respectively. This scope of work includes construction of townhomes
on Block C and Block D, driveway access, grading, utilities, and stormwater mitigation facilities. All off-site and
public right-of-way work was completed for the plat under separate permit prior to plat recording. This
proposal is limited to work entirely within the subject blocks. For preliminary plat and master plan approval, the
area including all 4 blocks and affected right-of-way was subject to full drainage review according to the
requirements of the 2017 Renton Surface Water Design Manual (RSWDM). The current townhome plan has
minor modifications to the layout approved by preliminary plat, and a site plan approval and master plan
modification were approved in 2024. This subsequent land use approval requires the development to comply
with the requirements of the 2022 RSWDM, but it does not alter the cumulative impact thresholds review
required for preliminary plat and master plan approval.
Figure 1-1: Site Map
2. Existing Conditions and Drainage
Block C and Block D have been rough graded under separate permit. Block C is approximately 2.58-acres
and is currently a grass field. Parcel D is approximately 1.28-acres and is currently in use as a temporary
parking lot for construction of the adjacent Block A and B apartment buildings. Plans call for Block D to also be
planted with grass once apartment construction is complete.
KPFF Consulting Engineers
2
Both Block C and D generally slope from northeast to southwest at slopes of 2 to 5%. Surface water runoff
from Block C leaves the site as sheet flow and is collected by a series of municipal pipes and catch basins in
Jefferson Ave NE and NE 10th Street. Surface water runoff from Block D similarly exits the site as sheet flow,
but is collected by a series of municipal pipes and catch basins in Harrington Ave NE and NE 11th Street. The
two flow paths do not combine until approximately ½-mile downstream. Therefore Blocks C and D are two
separate threshold discharge areas (TDAs). The flow paths converge in NE Sunset Blvd and ultimately outfall
to Lake Washington approximately 1.3 miles downstream from the site.
Figure 2-1: TDA Map
According to Geotechnical Engineering Study prepared by Earth Solutions NW, LCC (ESNW), dated
September 28, 2020, soil largely consisting of fill deposits underlain by medium dense to dense sand and silty
sand native soils (Appendix K). Therefore, we model pervious surfaces on the site as Type C soils in the
predeveloped and developed conditions.
3. Proposed Conditions and Requirements Summary
The project proposes 61 townhome units on Block C and 29 on Block D along with associated alleys,
landscape areas, open space, and requisite utilities. The development must comply with all nine core
requirements and six special requirements of the RSWDM.
Solera Phase 2: Block C and Block D – New Home Co.
3
CORE REQUIREMENT NO. 1: DISCHARGE AT THE NATURAL LOCATION
The development will utilize the pre-existing topography and drainage patterns of the site as described above
in Section 2 of this report. The proposed development will utilize the storm drainage stubs approved for this
purpose by the Solera Preliminary Plat and Civil Construction Permit.
CORE REQUIREMENT NO. 2: OFFSITE ANALYSIS
An off-site analysis was completed as part of the approved Solera Preliminary Plat.
CORE REQUIREMENT NO. 3: FLOW CONTROL
The preliminary plat was subject to full drainage review. The hearing examiner’s decision confirms, “The
project is exempt from flow control as the proposed project meets the exception criteria outlined in RSWDM
Section 1.2.3.1.A.”, and further, “The proposal provides for adequate drainage that is in conformance with
applicable City drainage standards as determined in Finding of Fact No. 6.” “The project” referred to in the
Hearing Examiner’s decision was the total plat includinposed townhome development on Blocks C & D.As is
required, Section 5 of this report confirms that the final proposal (this permit) is consistent with the scope of
work described in the preliminary approval and therefore staff findings and conclusions for this final permit
should also be consistent with the previous approval.
CORE REQUIREMENT NO. 4: CONVEYANCE S YSTEM
The development is required to convey the 25-year, 24-hour peak flow without overtopping. Pipe system
structures may overtop for runoff events exceeding the 25-year design capacity, provided overflow runoff from
a 100-year event does not create or aggravate a severe erosion or flooding problem downstream.
The proposed conveyance system has been designed to convey the 25-year peak flow without overtopping.
Refer to Section 7 for additional information.
CORE REQUIREMENT NO. 5: CONSTRUCTION STORMWATER POLLUTION
PREVENTION
Sediment-laden runoff is prohibited from entering adjacent right-of-way and downstream conveyance systems.
Temporary Erosion and Sediment Control (TESC) best management practices (BMPs) will be implemented
during construction. TESC BMPs are anticipated to include silt fences, conveyance channels, check dams,
sediment tanks, and catch basin inserts. Refer to Section 8 for additional information.
CORE REQUIREMENT NO. 6: MAINTENANCE AND OPERATIONS
All public improvements necessary to support this development were completed under separate permit and
are already accepted by the City. This project is entirely on private property where the owner has maintenance
responsibilities for all infrastructure except for sewer and water conveyance and distribution which are
maintained by the city of Renton. Refer to Section 10 for additional information.
CORE REQUIREMENT NO. 7: FINANCIAL GUARANTEES AND LIABILITY
Bond quantities for site improvements are provided in Section 10.
KPFF Consulting Engineers
4
CORE REQUIREMENT NO. 8: WATER QUALITY
Runoff from all pollution-generating surfaces within the development area must be treated for water quality
prior to discharge from the site. More than 50% of runoff draining to proposed water quality facilities is from
multifamily land uses, so this development is subject to Enhanced Basic Water Quality treatment, per the
RSWDM. Enhanced Basic Water Quality treatment requires 80 percent total suspended solids (TSS), more
than 30 percent dissolved copper removal, and more than 60 percent dissolved zinc removal. The project
proposes bioretention facilities to satisfy the requirement. Water quality measures are further described in
Section 6 of this report.
CORE REQUIREMENT NO. 9: ON-SITE BMPS
The project is required to meet the On-Site BMP requirements for target new impervious surfaces, new
pervious surfaces, and any replaced impervious surfaces. The City of Renton does not require including
existing impervious surfaces added on or after January 8, 2001 as target impervious surfaces.
The project will meet the Low Impact Development (LID) Performance Standard for the entire site. Projects
that achieve the LID Performance Standard are required to match developed discharge durations to the pre-
developed durations for the pre-developed discharge rates from 8 percent of the 2-year peak flow to 50
percent of the 2-year peak flow per RSMW Section 1.2.9.1.B. Pre-developed conditions must be modeled as
historic site conditions.
The project will implement the use of bioretention planters to the maximum extent feasible to meet the On-Site
BMP requirements. BMP measures are further detailed in Section 7 of this report.
SPECIAL REQUIREMENT NO. 1: OTHER ADOPTED AREA -SPECIFIC
REQUIREMENTS
There are no adopted area-specific requirements.
SPECIAL REQUIREMENT NO. 2: FLOOD HAZARD AREA DELINEATION
This project is not located in a flood hazard area.
SPECIAL REQUIREMENT NO. 3: FLOOD PROTECTION FACILITIES
This project does not modify or use a flood protection facility.
SPECIAL REQUIREMENT NO. 4: SOURCE CONTROL
There are no proposed commercial uses for Block C and Block D.
SPECIAL REQUIREMENT NO. 5: O IL CONTROL
The project does not classify as a high use site and is thus exempt from the Special Requirement #5.
SPECIAL REQUIREMENT NO. 6: AQUIFER PROTECTION AREAS
Under current revised delineations of aquifer protection areas within the city, the project site is not located
within any aquifer protection area or wellhead protection zone.
Solera Phase 2: Block C and Block D – New Home Co.
5
4. Off-Site Analysis
UPSTREAM ANALYSIS
The site is located on a ridgeline; therefore, no upstream basins drain onto the project site.
DOWNSTREAM ANALYSIS
A downstream analysis was completed for the approved preliminary plat, and is not duplicated here.
5. Flow Control Analysis and Design
Table 5-1 and Table 5-2 for on-site area and peak flow information. Existing conditions areas in these tables
are per the approved preliminary plat to which this project is vested and are provided for reference only. The
cumulative impacts of the total development were reviewed and approved with no flow control facilities
required. An Existing Conditions Map can be found in Appendix B, and MGSFlood output data is included in
Appendix D.
Table 5-1: On-Site Area Summary
Impervious (Acres) Pervious (Acres) Total (Acres)
Block C
Existing Conditions 1.31 1.27 2.58
Proposed Conditions 2.01 0.57 2.58
Block D
Existing Conditions 1.28 0 1.28
Proposed Conditions 0.78 0.5 1.28
Total
Existing Conditions 2.59 1.27 3.86
Proposed Conditions 2.70 1.16 3.86
Table 5-2: MGSFlood Peak Flow Rate with 15-Minute Time Step
Predeveloped Peak
Flows (cfs)
Unmitigated
Developed Peak Flows
(cfs)
2-Year Peak Flow 1.063 1.102
10-Year Peak Flow 1.559 1.625
100-Year Peak Flow 2.796 2.915
6. Water Quality Analysis and Design
Stormwater runoff is treated through bioretention facilities to meet Basic Enhanced Water Quality treatment
requirements. A preliminary Surface Runoff Basin Map can be found in Appendix E.
Stormwater runoff from impervious surfaces is conveyed to bioretention facilities. Construction of Block C and
Block D were originally subdivided into 15 basins from the original master plan. Refer to Figure 6-1: Water
flow control for block c and d
has been reviewed under this permit
KPFF Consulting Engineers
6
Quality Basins. These have been modified since the previous master plan and site plan review submittal based
on site constraints. Please see the delineated water quality basin map in Appendix E.
The water quality design flow, when detention facilities are not required, must meet 91 percent of the total
runoff volume using a 15-minute time step per Section 6.2.1 of the RSWM. Additional infiltration testing was
completed on November 4, 2024 by Earth Solutions Northwest LLC. A memorandum summarizing findings is
included in Appendix M. Testing resulted in a minimum infiltration rate of 3.5 inches per hour in areas with
proposed infiltration; this value will be used across the site for a conservative approach. Runoff treated in
bioretention planters will infiltrate into native soils or overflow to the previously described downstream flow
path.
Design infiltration rates were determined per Section 5.2.1 of the RSWM. An infiltration rate of 6 inches per
hour with a safety factor of 2 was used for the amended soil and an infiltration rate of 3.5 inches per hour was
used for the underlying native soils per the memorandum in Appendix M. A design spreadsheet summarizing
contributing area, bioretention design, and all MGSFlood modeling output data will be provided in Appendix E
with construction documents.
Where planters receive roof and road runoff, all contributing areas are evaluated as one inflow volume to meet
the water quality treatment requirements and the on-site BMP requirements to the maximum extent feasible.
With this application, all bioretention planters meet the 91 percent of total runoff volume for the road surface
requiring water quality treatment with the addition of roof runoff for the on-site BMP requirement. Please see
table 6-1 below for water quality sub-basin sizing.
Table 6-1: Block C and D Bioretention Sizing for Water Quality and On-site BMPS
PLANTER #
(BASIN) BASIN
AREA (SF)
CONTRIBUTING AREA
BIORETENTION
BOTTOM AREA (SF)
NUMBER OF
CELLS
ROAD
(SF) SWK (SF) ROOF
(SF)
TOTAL
IMP (SF)
PERV
(SF)
BLOCK C
C1 12,128 8,879 698 - 9,577 2,551 173 2
C2 3,877 - - 2,872 2,872 1,005 31 1
C3 3,877 - - 2,872 2,872 1,005 50 1
C4 13,940 11,321 1,405 - 12,726 1,214 289 2
C5 11,696 - - 11,696 11,696 - 390 2
C6 4,625 - 3,884 3,884 741 53 1
C7 11,021 884 320 8,454 9,658 1,363 234 2
BLOCK D
D8 15,550 5,016 - 2,873 7,889 7,661 189 2
D9 10,500 2,264 - 3,482 5,746 4,754 160 1
D10 8,000 1,850 - 5,054 6,904 1,096 81 1
EX PH1
PLANTER 2,183 2,183 - - 2,183 - 90 1
Solera Phase 2: Block C and Block D – New Home Co.
7
7. On-site BMPs
According to section 1.2.9 of the RWSM, Core Requirement #9 can be satisfied by,
1) Application of BMPs to the maximum extent feasible; or,
2) Using a continuous runoff model to demonstrate compliance with the Low Impact Development (LID)
Performance Standard.
This development has opted to apply BMPs to the maximum extent feasible across the site. The development
has proposed to meet this requirement primarily through bioretention cells distributed throughout the site. Per
the master plan, 31,500 square feet of net open space area is required; bioretention and drainage facilities
cannot encroach within the open space provided, therefore the project is limited to 4,710 square feet of total
space available for bioretention facilities. Please see table 6-1 for the bioretention sizing and the storm
drainage plans for planter extents and slopes. Presettling is provided in basins with bioretention facilities taking
greater than 5,000 sf of impervious area. Weir walls separating cells receiving 5,000 sf of impervious area at a
single inlet have been implemented at the applicable planters.
For Block C, the site provides at-grade bioretention planters for road runoff and roof areas where feasible. The
project proposes the maximum bioretention area allowable by existing site constraints and meeting open
space requirements. Soil Amendment is proposed to meet BMP requirements for new pervious surfaces on
Block C in accordance with The City of Renton Surface Water Design Manual Appendix C.2.13.
For Block D, the site provides at-grade bioretention planters for road runoff and roof areas where feasible. The
project proposes the maximum bioretention area allowable by existing site constraints and meeting open
space requirements. For new pervious surface on Block D, Soil Amendment is proposed to meet BMP
requirements in accordance with The City of Renton Surface Water Design Manual Appendix C.2.13.
Overflow from bioretention areas will be routed via on-site conveyance structures and drain lines to the
existing public conveyance system. Basin delineation for the combined water quality and BMP bioretention
planters and individual basin’s MGSFlood Reports are provided in Appendix E.
8. Conveyance System Analysis and Design
Storm pipe conveyance and analysis are provided in Appendix F.
9. ESC Analysis and Design
Erosion Control plans and details are provided in Appendix G. A construction stormwater pollution prevention
plan is provided in Appendix H.
10. Special Reports and Studies
A geotechnical engineering report was prepared by Earth Solutions NW, LLC, dated September 2020. This is
included in Appendix K of this report.
KPFF Consulting Engineers
8
11. Bond Quantities and Declaration of Covenant
A City of Renton bond quantity worksheet is provided in Appendix I. A Declaration of Covenant for Operation
and Maintenance is provided in Appendix J.
Solera Subdivision: Block A and Block B – DevCo, LLC
Appendix A
Appendix A
TIR Worksheet
CITY OF RENTON SURFACE WATER DESIGN MANUAL
2017 City of Renton Surface Water Design Manual 12/12/2016 8-A-1
REFERENCE 8-A
TECHNICAL INFORMATION REPORT (TIR)
WORKSHEET
Part 1 PROJECT OWNER AND
PROJECT ENGINEER Part 2 PROJECT LOCATION AND
DESCRIPTION
Project Owner _____________________________
Phone ___________________________________
Address __________________________________
_________________________________________
Project Engineer ___________________________
Company _________________________________
Phone ___________________________________
Project Name __________________________
CED Permit # ________________________
Location Township ________________
Range __________________
Section _________________
Site Address __________________________
_____________________________________
Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS
Land Use (e.g., Subdivision / Short Subd.)
Building (e.g., M/F / Commercial / SFR)
Grading
Right-of-Way Use
Other _______________________
DFW HPA
COE 404
DOE Dam Safety
FEMA Floodplain
COE Wetlands
Other ________
Shoreline Management
Structural Rockery/Vault/_____
ESA Section 7
Part 5 PLAN AND REPORT INFORMATION
Technical Information Report Site Improvement Plan (Engr. Plans)
Type of Drainage Review
(check one):
Date (include revision
dates):
Date of Final:
Full
Targeted
Simplified
Large Project
Directed
____________________________________
__________________
Plan Type (check
one):
Date (include revision
dates):
Date of Final:
Full
Modified
Simplified
____________________________________
__________________
Jaden Storedahl
(503) 899-8170
1700 NW Gilman Blvd, Suite 220
Issaquah, WA 98027
Michelle Freeman
KPFF
(206) 622-5822
Solera Blocks C & D
23 North
05 East
9
2842 NE Sunset Boulevard,
Renton, WA 98056
X
X
X
X
X
X
09/24/2024
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-2
Part 6 SWDM ADJUSTMENT APPROVALS
Type (circle one): Standard / Blanket
Description: (include conditions in TIR Section 2)
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
Approved Adjustment No. ______________________ Date of Approval: _______________________
Part 7 MONITORING REQUIREMENTS
Monitoring Required: Yes / No
Start Date: _______________________
Completion Date: _______________________
Describe: _________________________________
_________________________________________
_________________________________________
Re: SWDM Adjustment No. ________________
Part 8 SITE COMMUNITY AND DRAINAGE BASIN
Community Plan: ____________________________________________________________________
Special District Overlays: ______________________________________________________________
Drainage Basin: _____________________________________________________________________
Stormwater Requirements: _____________________________________________________________
Part 9 ONSITE AND ADJACENT SENSITIVE AREAS
River/Stream ________________________
Lake ______________________________
Wetlands ____________________________
Closed Depression ____________________
Floodplain ___________________________
Other _______________________________
_______________________________
Steep Slope __________________________
Erosion Hazard _______________________
Landslide Hazard ______________________
Coal Mine Hazard ______________________
Seismic Hazard _______________________
Habitat Protection ______________________
_____________________________________
Core Requirements 1-9 and Special Requirements 1-6
Sunset Area Surface Water Master Plan (CH2M HILL, 2011)
none proposed
East Lake Washington
REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
2017 City of Renton Surface Water Design Manual 12/12/2016 Ref 8-A-3
Part 10 SOILS
Soil Type
______________________
______________________
______________________
______________________
Slopes
________________________
________________________
________________________
________________________
Erosion Potential
_________________________
_________________________
_________________________
_________________________
High Groundwater Table (within 5 feet)
Other ________________________________
Sole Source Aquifer
Seeps/Springs
Additional Sheets Attached
Part 11 DRAINAGE DESIGN LIMITATIONS
REFERENCE
Core 2 – Offsite Analysis_________________
Sensitive/Critical Areas__________________
SEPA________________________________
LID Infeasibility________________________
Other________________________________
_____________________________________
LIMITATION / SITE CONSTRAINT
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
Additional Sheets Attached
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet
per Threshold Discharge Area)
Threshold Discharge Area:
(name or description)
Core Requirements (all 8 apply):
Discharge at Natural Location Number of Natural Discharge Locations:
Offsite Analysis Level: 1 / 2 / 3 dated:__________________
Flow Control (include facility
summary sheet)
Standard: _______________________________
or Exemption Number: ____________
On-site BMPs: _______________________________
Conveyance System Spill containment located at: _____________________________
Erosion and Sediment Control /
Construction Stormwater Pollution
Prevention
CSWPP/CESCL/ESC Site Supervisor: _____________________
Contact Phone: _________________________
After Hours Phone: _________________________
Type C Till 2-5%Low
Block C and Block D
2
03/12/2021
TBD
Bioretention
TBD
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-4
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet
per Threshold Discharge Area)
Maintenance and Operation Responsibility (circle one): Private / Public
If Private, Maintenance Log Required: Yes / No
Financial Guarantees and Liability Provided: Yes / No
Water Quality (include facility
summary sheet)
Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog
or Exemption No. _______________________
Special Requirements (as applicable):
Area Specific Drainage
Requirements
Type: SDO / MDP / BP / Shared Fac. / None
Name: ________________________
Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None
100-year Base Flood Elevation (or range): _______________
Datum:
Flood Protection Facilities Describe:
Source Control
(commercial / industrial land use)
Describe land use:
Describe any structural controls:
Oil Control High-Use Site: Yes / No
Treatment BMP: _________________________________
Maintenance Agreement: Yes / No
with whom? _____________________________________
Other Drainage Structures
Describe:
Mixed
none
None
Residential
TBD During Building Permit Application
None
REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
2017 City of Renton Surface Water Design Manual 12/12/2016 Ref 8-A-5
Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS
MINIMUM ESC REQUIREMENTS
DURING CONSTRUCTION
Clearing Limits
Cover Measures
Perimeter Protection
Traffic Area Stabilization
Sediment Retention
Surface Water Collection
Dewatering Control
Dust Control
Flow Control
Control Pollutants
Protect Existing and Proposed BMPs/Facilities
Maintain Protective BMPs / Manage Project
MINIMUM ESC REQUIREMENTS
AFTER CONSTRUCTION
Stabilize exposed surfaces
Remove and restore Temporary ESC Facilities
Clean and remove all silt and debris, ensure operation of Permanent BMPs/Facilities, restore
operation of BMPs/Facilities as necessary
Flag limits of sensitive areas and open space
preservation areas
Other _______________________
Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch)
Flow Control Type/Description Water Quality Type/Description
Detention
Infiltration
Regional Facility
Shared Facility
On-site BMPs
Other
________________
________________
________________
________________
________________
________________
Vegetated Flowpath
Wetpool
Filtration
Oil Control
Spill Control
On-site BMPs
Other
________________
________________
________________
________________
________________
________________
________________
Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS
Drainage Easement
Covenant
Native Growth Protection Covenant
Tract
Other ____________________________
Cast in Place Vault
Retaining Wall
Rockery > 4′ High
Structural on Steep Slope
Other _______________________________
X
X
X
X
X X
X
X
X
X
Bioretention
X
X
X
X
X
X
X
X
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-6
Part 17 SIGNATURE OF PROFESSIONAL ENGINEER
I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my
knowledge the information provided here is accurate.
____________________________________________________________________________________ Signed/Date
09/03/2025
Solera Phase 2: Block C and Block D – New Home Co.
Appendix B
Appendix B
Existing Conditions Map
N
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F
W
A
Y
)
SUNSET LANE NE
(A DEDICATED PUBLIC RIGHT OF WAY)
NE SUNSET BOULEVARD
(A DEDICATED PUBLIC RIGHT OF WAY)
PERVIOUS: 1.78 ACRES
IMPERVIOUS = 11.04 ACRES
B A
DC
SOLERA
EXISTING CONDITIONS
JEFFERSON AVENUE NE
NE SUNSET BOULEVARD (SR 900)
NE
1
0
T
H
S
T
R
E
E
T
NE
1
1
T
H
S
T
R
E
E
T
N
E
1
2
T
H
S
T
R
E
E
T
HARRINGTON PLACE NE
KIR
K
L
A
N
D
AV
E
N
U
E
N
E
Solera Phase 2: Block C and Block D – New Home Co.
Appendix C
Appendix C
Proposed Conditions Map
0
1 inch = 40 feet
20'40'80'
LEGEND:
PROPERTY LINE
ROW LINE
ROW CENTERLINE
PROPOSED MAJOR CONTOUR
PROPOSED MINOR CONTOUR
STORM MAIN
CATCH BASIN
360
362
HARRINGTON PL NEHARR
I
N
G
T
O
N
A
V
E
N
E
NE
1
0
T
H
S
T
N
E
1
2
T
H
S
T
KIR
K
L
A
N
D
A
V
E
N
E
NE
1
1
T
H
S
T
JEFFERSON AVE NE JEFFERSON AVE NE
AL
L
E
Y
A
ALLEY B
AL
L
E
Y
D
AL
L
E
Y
E
AL
L
E
Y
F
AL
L
E
Y
G
ALLEY C
BLOCK B BLOCK A
BLOCK C
BLOCK D
SURFACE
ROOF TOP
SIDEWALK
ROAD/DRIVEWAY
BIORETENTION PLANTER
LANDSCAPE/GRAVEL
TOTAL
BLOCK A
1.94 AC
0.27 AC
0.03 AC
0.03 AC
0.33 AC
2.60 AC
BLOCK B
2.04 AC
0.22 AC
0.19 AC
0
0.31 AC
2.76 AC
TOTAL
5.51 AC
1.89 AC
2.91 AC
0.20 AC
2.31 AC
12.82 AC
BLOCK C
1.10 AC
0.37 AC
0.47 AC
0.03 AC
0.57 AC
2.57 AC
BLOCK D
0.43 AC
0.07 AC
0.25 AC
0.01 AC
0.52 AC
1.28 AC
OFF-SITE
0
0.96 AC
1.97 AC
0.13 AC
0.55 AC
3.61 AC
PHASE 1 (CONSTRUCTED)PHASE 2 (PROPOSED)
JEFFERSON AVENUE NE
NE
1
0
T
H
S
T
R
E
E
T
NE
1
1
T
H
S
T
R
E
E
T
KIR
K
L
A
N
D
AV
E
N
U
E
N
E
BLOCK ABLOCK B
Solera Phase 2: Block C and Block D – New Home Co.
Appendix D
Appendix D
Peak Flow Control Application Map and Flow Contorl MGS Flood Calculation
LakeDesire
ShadyLake (MudLake)
PantherLake LakeYoungs
LakeWashington
B l a ck Riv e r
Gree n Riv
e
r
C
edarRiver
UV900
UV167
UV515
UV169
UV900
UV169
UV167
BN
I
n
c
BN
I
n
c
BBNNIInncc
SSEERReennttoonnIIssssaaqquuaahh RR dd
RReennttoonnMMaapplleeVVaalllleeyyRRdd
MMaapplleeVVaalllleeyyHHwwyy
110088tthh
AAvvee
SSEE
SSWWSSuunnsseettBBllvvdd
RR
aa
ii
nn
ii
ee
rr
AAvvee
NN
NE 3rd StNE 3rd St
SW 43rd StSW 43rd St SSEE CC aarrrr RR dd
NE 4th StNE 4th St
SSEERReennttoonn MMaappllee VVaalllleeyy RRdd
LLooggaann
AAvvee
NN
S
R
5
1
5
S
R
5
1
5
PPaarrkk
AAvvee
NN
OOaakkeessddaallee
AAvvee
SSWW
SSuunnsseettBBllvvdd NNEE
DDuuvvaallll
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I-405 FWYI-405 FWY
II--440055
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SR
1
6
7
SR
1
6
7
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115566tthh
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UUnniioonn
AAvvee
NNEE
111166tthh
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SW 7th StSW 7th St
N 8th StN 8th St
PPuuggeettDDrrSS EE
RR
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SSWW 2277tthh SStt
BB
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nn
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SE 128th StSE 128th St
II
nn
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SE 192nd StSE 192nd St
SE 60th StSE 60th St
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AA
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116644tthh
AAvvee
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SE 208th StSE 208th St
SE 72nd StSE 72nd St
RRaaiinniieerrAAvvee
SS
111166tthh
AAvvee
SSEE
S 128th StS 128th St
NNeewwccaassttllee WWaayy
SS 221122tthh SStt
SS118800tthh SStt
CC
oo
aa
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rr
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SW 41st StSW 41st St
114400tthh
AAvvee
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112288tthh
AAvvee
SSEE
6688tthh
AAvvee
SS
SSEE 116688tthh SStt
NE 12th StNE 12th St
BB
ee
aa
ccoonn
AA
vv
ee
SS
FFoorreessttDDrr SSEE
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114488tthh
AAvvee
SSEE
SSEEMMaayy VVaalllleeyyRRdd
SS EE JJoonneess RRdd
SS EE 22 00 44 tt hh WW aayy
SW 34th StSW 34th St
SE 144th StSE 144th St
114488tthh
AAvvee
SSEE
115544tthhPPllSSEE
LL
aa
kk
ee
WW
aa
ss
hh
ii
nn
gg
tt
oo
nn
BB
ll
vv
dd
NN
EEddmmoonnddss
AAvvee
NNEE
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AAvvee
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EE MMeerrcceerrWWaayy
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HHwwyy
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d
,§-405
,§-405
,§-405
µ0 1 2Miles
Flow Control Application Map
Reference 15-A
Date: 01/09/2014
Flow Control Standards
Peak Rate Flow Control Standard (Existing Site Conditions)
Flow Control Duration Standard (Existing Site Conditions)
Flow Control Duration Standard (Forested Conditions)
Flood Problem Flow
Unincorporated King County Flow Control Standards
Renton City Limits
Potential Annexation Area
PROJECT SITE
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.63
Program License Number: 200410007
Project Simulation Performed on: 09/24/2024 3:40 PM
Report Generation Date: 09/24/2024 3:40 PM
—————————————————————————————————
Input File Name: Solera Phase 2 Flow Control.fld
Project Name: Entire Site Solera Townhomes (Phase 2)
Analysis Title: Flow Control Analysis
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Full Period of Record Available used for Routing
Climatic Region Number: 3
Precipitation Station : 95004005 Puget West 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 951040 Puget West 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : Ecology Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 3.860 3.860
Area of Links that Include Precip/Evap (acres) 0.000 0.000
Total (acres) 3.860 3.860
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
A/B, Lawn, Flat 1.270
PARKING/FLAT 2.590
BLOCKS C AND D FLOWCONTROL MODELING REPORT
----------------------------------------------
Subbasin Total 3.860
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 2
---------- Subbasin : Block C ----------
-------Area (Acres) --------
A/B, Lawn, Flat 0.630
ROADS/FLAT 0.480
ROOF TOPS/FLAT 1.100
SIDEWALKS/FLAT 0.370
----------------------------------------------
Subbasin Total 2.580
---------- Subbasin : Block D ----------
-------Area (Acres) --------
A/B, Lawn, Flat 0.530
ROADS/FLAT 0.250
ROOF TOPS/FLAT 0.430
SIDEWALKS/FLAT 0.070
----------------------------------------------
Subbasin Total 1.280
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: New Copy Lnk1
Link Type: Copy
Downstream Link: None
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 2
Number of Links: 1
BLOCKS C AND D FLOWCONTROL MODELING REPORT
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 427.906
_____________________________________
Total: 427.906
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Block C 212.268
Subbasin: Block D 178.575
Link: New Copy Lnk1 0.000
_____________________________________
Total: 390.843
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 2.708 ac-ft/year, Post Developed: 2.474 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: New Copy Lnk1 **********
2-Year Discharge Rate : 1.102 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.43 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.25 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 1219.58
Inflow Volume Including PPT-Evap (ac-ft): 1219.58
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 1219.58
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00%
BLOCKS C AND D FLOWCONTROL MODELING REPORT
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: New Copy Lnk1
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 1.063 2-Year 1.102
5-Year 1.336 5-Year 1.392
10-Year 1.559 10-Year 1.625
25-Year 1.877 25-Year 1.955
50-Year 2.334 50-Year 2.433
100-Year 2.796 100-Year 2.915
200-Year 2.928 200-Year 3.052
500-Year 3.097 500-Year 3.228
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): 4.1% FAIL
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): 16.2% FAIL
-------------------------------------------------------------------------------------------------
LID DURATION DESIGN CRITERIA: FAIL
-------------------------------------------------------------------------------------------------
BLOCKS C AND D FLOWCONTROL MODELING REPORT
Solera Phase 2: Block C and Block D – New Home Co.
Appendix E
Appendix E
Water Quality and On-Site BMP MGS Flood Bioretention Calculations
HAR
R
I
N
G
T
O
N
A
V
E
N
E
JEFFERSON AVE NE
AL
L
E
Y
A
ALLEY B
AL
L
E
Y
D
AL
L
E
Y
E
AL
L
E
Y
F
BLOCK C
NE
1
1
T
H
S
T
N
E
1
0
T
H
S
T
0
1 inch = 50 feet
25'50'100'
LEGEND:
PROPERTY LINE
PROPOSED MAJOR CONTOUR
PROPOSED MINOR CONTOUR
STORM MAIN
CATCH BASIN
BIORETENTION PLANTER
360
362
C:\
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Drawing Title
Date
Drawing Reference
Drawn/Ck'd By
Scale
ASI/RFI/CSK Number
1601 5th Avenue, Suite 1600
Seattle, WA 98101
206.622.5822
www.kpff.com
Project Title
Client
SOLERA TOWNHOMES
NEW HOME CO
BLOCK C DRAINAGE BASIN MAP
C 1" = 50'
03/06/2025 MDR/MNF
BMP TYPE OF
SURFACE
IMPERVIOUS
AREA (SF)
TOTAL CONTRIBUTING
IMPERVIOUS AREA (SF)
BMP BOTTOM AREA
PROVIDED (SF)
C1 PGIS 8,879 9,577 173NPGIS698
C2 NPGIS 2,872 2,872 31
C3 NPGIS 2,871 2,872 50
C4 PGIS 11,321 12,726 296NPGIS1,405
C5 NPGIS 11,696 11,696 390
C6 NPGIS 3,884 3,884 53
C7 PGIS 884 9,658 415
NPGIS 320
BYPASS NPGIS 24,098 23,788 N/A
HARRINGTON PL NE
N
E
1
2
T
H
S
T
AL
L
E
Y
G
ALLEY C
BLOCK D
NE
1
1
T
H
S
T
PROPERTY LINE
PROPOSED MAJOR CONTOUR
PROPOSED MINOR CONTOUR
STORM MAIN
CATCH BASIN
BIORETENTION PLANTER
360
362
0
1 inch = 50 feet
25'50'100'
LEGEND:
C:\
U
s
e
r
s
\
M
o
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a
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\
a
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1
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2
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M
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Ma
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2
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2
5
-
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R
Drawing Title
Date
Drawing Reference
Drawn/Ck'd By
Scale
ASI/RFI/CSK Number
1601 5th Avenue, Suite 1600
Seattle, WA 98101
206.622.5822
www.kpff.com
Project Title
Client
SOLERA TOWNHOMES
NEW HOME CO
BLOCK D DRAINAGE BASIN MAP
D 1" = 50'
03/06/2025 MDR/MNF
BMP TYPE OF
SURFACE
IMPERVIOUS
AREA (SF)
TOTAL CONTRIBUTING
IMPERVIOUS AREA (SF)
BMP BOTTOM AREA
PROVIDED (SF)
D8 PGIS 5,016 7,889 189NPGIS2,873
D9 PGIS 2,264
5,746 160
NPGIS 3,482
D10 PGIS 1,850 6,904 81NPGIS5,054
PHASE 1 EX
PLANTER NPGIS 2183 2183 90
BYPASS NPGIS 12,326 12,236 N/A
OPEN SPACE PLAN
SCALE 1" = 40'
LEGEND
COMMON OPEN SPACE
BIORETENTION PLANTERS WITHIN COMMON OPEN SPACE
32,291 SF
2,231 SF
PER RENTON CODE SECTION 4-2-115
350 SQUARE FEET OF COMMON OPEN SPACE TO BE PROVIDED PER UNIT
TOTAL UNITS PROVIDED:90
TOTAL COMMON OPEN SPACE REQUIRED:31,500 SF (350 X 90)
TOTAL COMMON OPEN SPACE PROVIDED:32,291 SF
PRIVATE OPEN SPACE REQUIRED PER UNIT:250 SF
OPEN SPACE CALCULATIONS
376 SF
290 SF
261 SF
334 SF
661 SF
710 SF
2,997 SF
446 SF
503 SF
300 SF
284 SF
293 SF
295 SF250 SF
278 SF
307 SF
286 SF
276 SF
353 SF
276 SF
353 SF294 SF
280 SF
305 SF
288 SF
355 SF
283 SF
275 SF
278 SF
355 SF
336 SF
336 SF
269 SF
262 SF
264 SF
467 SF
468 SF
349 SF
367 SF
356 SF
491 SF
372 SF
372 SF
489 SF
396 SF
328 SF
335 SF
353 SF
488 SF
383 SF 291 SF
304 SF
297 SF
322 SF
378 SF
364 SF
407 SF
287 SF
300 SF
292 SF
317 SF378 SF
290 SF
320 SF
303 SF
298 SF
321 SF
295 SF
287 SF
316 SF
300 SF
295 SF
320 SF
292 SF
287 SF
316 SF
300 SF
295 SF 292 SF 463 SF
292 SF
463 SF 292 SF 378 SF
292 SF
378 SF 292 SF
317 SF
317 SF
292 SF
292 SF
435 SF
3,176 SF
3,684 SF
3,995 SF
3,943 SF
1,696 SF
1,407 SF
1,960 SF
916 SF
1,471 SF
COMMON OPEN SPACE (TYP.)
PRIVATE OPEN SPACE (TYP.)
PROPERTY LINE (TYP.)
PRIVATE OPEN SPACE30,224 SF
833 SF
128 SF 165 SF 620 SF 715 SF 179 SF 416 SF 912 SF
BIORETENTION PLANTERS WITHINCOMMON OPEN SPACE (TYP.)
916 SF
733 SF
1,471 SF 1,471 SF
IN COMPLIANCE WITH CITY OF RENTON STANDARDS
DESIGN
12100 NE 195th St, Suite 300 Bothell, Washington 98011 425.885.7877
CIVIL ENGINEERINGLANDSCAPE ARCHITECTUREPLANNINGSURVEYING
SOLERA TOWNHOMES
SO
L
E
R
A
T
O
W
N
H
O
M
E
S
SO
L
E
R
A
T
O
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N
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M
E
S
C:
2
5
0
0
3
1
7
3
LU
A
:
2
4
-
0
0
0
3
7
5
PR
:
1
8
-
0
0
0
3
3
3
TE
D
-
4
0
-
4
3
6
3
OPEN SPACE PLAN
L2
.
0
1
L2.01
Solera Subdivision - Block C and Block D
Bioretention Sizing for LID Performance Standard & WQ
(SF) (AC)ROAD (SF) AC SWK (SF) AC ROOF (SF) AC TOTAL IMP (SF) PERV (SF) AC (SF) (AC)
BLOCK C
C1 12,128 0.2784 8,879 0.2038 698 0.0160 - - 9,577 2,551 0.0586 173 0.0040 64.07 2.70
C2 3,877 0.0890 - - - - 2,872 0.0659 2,872 1,005 0.0231 31 0.0007 11.48 2.70
C3 3,877 - - - - 2,872 0.0659 2,872 1,005 0.0231 50 0.0011 14.49 3.45
C4 13,940 0.3200 11,321 0.2599 1,405 0.0323 - - 12,726 1,214 0.0279 289 0.0066 74.10 3.90
C5 11,696 0.2685 - - - - 11,696 0.2685 11,696 - - 390 0.0090 59.09 6.60
C6 4,625 0.1062 - - - 3,884 0.0892 3,884 741 0.0170 53 0.0012 16.77 3.16
C7 11,021 0.2530 884 0.0203 320 0.0073 8,454 0.1941 9,658 1,363 0.0313 234 0.0054 37.74 6.20
BLOCK D
D8 15,550 0.3570 5,016 0.1152 - - 2,873 0.0660 7,889 7,661 0.1759 189 0.0043 47.25 4.00
D9 10,500 0.2410 2,264 0.0520 - - 3,482 0.0799 5,746 4,754 0.1091 160 0.0037 32.00 5.00
D10 8,000 1,850 0.0425 - - 5,054 0.1160 6,904 1,096 81 0.0019 40.50 2.00
EX PH1
PLANTER 2,183 0.0501 2,183 0.0501 - - - - 2,183 - - 90 0.0021 22.50 4.00
PLANTER #
(BASIN)
BASIN AREA CONTRIBUTING AREA
DESIGN BIORETENTION
BOTTOM AREA BOTTOM
WIDTH (FT)
BOTTOM
LENGTH
(FT)
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.64
Program License Number: 200410007
Project Simulation Performed on: 05/22/2025 2:59 PM
Report Generation Date: 05/22/2025 3:01 PM
—————————————————————————————————
Input File Name: Solera Phase 2 Water Quality.fld
Project Name: Entire Site Solera Townhomes (Phase 2)
Analysis Title: Water Quality Analysis
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Full Period of Record Available used for Routing
Climatic Region Number: 3
Precipitation Station : 95004005 Puget West 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 951040 Puget West 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : Ecology Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 0.794 1.957
Area of Links that Include Precip/Evap (acres) 0.000 0.040
Total (acres) 0.794 1.997
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
PARKING/FLAT 0.794
----------------------------------------------
WATER QUALITY AND ON-SITE BMPMODELING FOR BLOCKS C AND D
Subbasin Total 0.794
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 11
---------- Subbasin : C1 ----------
-------Area (Acres) --------
ROADS/FLAT 0.204
SIDEWALKS/FLAT 0.016
----------------------------------------------
Subbasin Total 0.220
---------- Subbasin : C2 ----------
-------Area (Acres) --------
C, Lawn, Flat 0.023
ROOF TOPS/FLAT 0.066
----------------------------------------------
Subbasin Total 0.089
---------- Subbasin : C4 ----------
-------Area (Acres) --------
C, Lawn, Flat 0.028
ROADS/FLAT 0.260
SIDEWALKS/FLAT 0.032
----------------------------------------------
Subbasin Total 0.320
---------- Subbasin : C6 ----------
-------Area (Acres) --------
C, Lawn, Flat 0.017
ROOF TOPS/FLAT 0.089
----------------------------------------------
Subbasin Total 0.106
---------- Subbasin : C7 ----------
-------Area (Acres) --------
C, Lawn, Flat 0.031
ROADS/FLAT 0.020
ROOF TOPS/FLAT 0.194
SIDEWALKS/MOD 0.007
----------------------------------------------
Subbasin Total 0.253
---------- Subbasin : C5 ----------
-------Area (Acres) --------
ROOF TOPS/FLAT 0.269
----------------------------------------------
Subbasin Total 0.269
---------- Subbasin : C3 ----------
-------Area (Acres) --------
C, Lawn, Flat 0.023
ROOF TOPS/FLAT 0.066
----------------------------------------------
Subbasin Total 0.089
---------- Subbasin : D10 ----------
-------Area (Acres) --------
ROADS/MOD 0.043
ROOF TOPS/FLAT 0.116
----------------------------------------------
Subbasin Total 0.159
---------- Subbasin : D9 ----------
-------Area (Acres) --------
ROADS/MOD 0.052
ROOF TOPS/FLAT 0.080
----------------------------------------------
Subbasin Total 0.132
---------- Subbasin : D8 ----------
-------Area (Acres) --------
ROADS/MOD 0.115
ROOF TOPS/FLAT 0.066
----------------------------------------------
Subbasin Total 0.181
---------- Subbasin : D11 ----------
-------Area (Acres) --------
C, Lawn, Flat 0.022
ROADS/MOD 0.117
----------------------------------------------
Subbasin Total 0.139
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 13
------------------------------------------
Link Name: Block C POC
Link Type: Copy
Downstream Link: None
------------------------------------------
Link Name: C1
Link Type: Ecology Bioretention Facility
Downstream Link Name: Block C POC
Floor Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 64.0
Bottom Width (ft) : 2.7
Bottom Slope (ft/ft) : 0.000
Side Slopes (ft/ft) : Z1= 2.50 Z2= 2.50 Z3= 2.50 Z4= 2.50
Bottom Area (sq-ft) : 173.
Area at Riser Crest El (sq-ft) : 346.
(acres) : 0.008
Volume at Riser Crest (cu-ft) : 129.
(ac-ft) : 0.003
Infiltration on Bottom and Sideslopes Selected
Soil Properties
Layer No Soil Name Thickness (ft)
1 ASTM 100 0.010
2 SMMWW 6 in/hr (Ecolo 1.500
3 GRAVEL 0.010
KSat Safety Factor: 4.0
Native Soil Infiltration Rate (in/hr) : 3.50
Underdrain Not Present
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
------------------------------------------
Link Name: BLOCK D POC
Link Type: Copy
Downstream Link: None
------------------------------------------
Link Name: C2
Link Type: Ecology Bioretention Facility
Downstream Link Name: Block C POC
Floor Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 11.5
Bottom Width (ft) : 2.7
Bottom Slope (ft/ft) : 0.000
Side Slopes (ft/ft) : Z1= 2.50 Z2= 2.50 Z3= 2.50 Z4= 2.50
Bottom Area (sq-ft) : 31.
Area at Riser Crest El (sq-ft) : 73.
(acres) : 0.002
Volume at Riser Crest (cu-ft) : 25.
(ac-ft) : 0.001
Infiltration on Bottom and Sideslopes Selected
Soil Properties
Layer No Soil Name Thickness (ft)
1 ASTM 100 0.010
2 SMMWW 6 in/hr (Ecolo 1.500
3 GRAVEL 0.010
KSat Safety Factor: 2.0
Native Soil Infiltration Rate (in/hr) : 3.50
Underdrain Not Present
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
------------------------------------------
Link Name: C4
Link Type: Ecology Bioretention Facility
Downstream Link Name: Block C POC
Floor Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 75.9
Bottom Width (ft) : 3.9
Bottom Slope (ft/ft) : 0.000
Side Slopes (ft/ft) : Z1= 2.50 Z2= 2.50 Z3= 2.50 Z4= 2.50
Bottom Area (sq-ft) : 296.
Area at Riser Crest El (sq-ft) : 502.
(acres) : 0.012
Volume at Riser Crest (cu-ft) : 199.
(ac-ft) : 0.005
Infiltration on Bottom and Sideslopes Selected
Soil Properties
Layer No Soil Name Thickness (ft)
1 ASTM 100 0.010
2 SMMWW 6 in/hr (Ecolo 1.500
3 GRAVEL 0.010
KSat Safety Factor: 4.0
Native Soil Infiltration Rate (in/hr) : 3.50
Underdrain Not Present
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
------------------------------------------
Link Name: C6
Link Type: Ecology Bioretention Facility
Downstream Link Name: Block C POC
Floor Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 16.8
Bottom Width (ft) : 3.2
Bottom Slope (ft/ft) : 0.000
Side Slopes (ft/ft) : Z1= 2.50 Z2= 2.50 Z3= 2.50 Z4= 2.50
Bottom Area (sq-ft) : 53.
Area at Riser Crest El (sq-ft) : 109.
(acres) : 0.003
Volume at Riser Crest (cu-ft) : 40.
(ac-ft) : 0.001
Infiltration on Bottom and Sideslopes Selected
Soil Properties
Layer No Soil Name Thickness (ft)
1 ASTM 100 0.010
2 SMMWW 6 in/hr (Ecolo 1.500
3 GRAVEL 0.010
KSat Safety Factor: 2.0
Native Soil Infiltration Rate (in/hr) : 3.50
Underdrain Not Present
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
------------------------------------------
Link Name: C7
Link Type: Ecology Bioretention Facility
Downstream Link Name: Block C POC
Floor Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 37.7
Bottom Width (ft) : 6.2
Bottom Slope (ft/ft) : 0.000
Side Slopes (ft/ft) : Z1= 2.50 Z2= 2.50 Z3= 2.50 Z4= 2.50
Bottom Area (sq-ft) : 234.
Area at Riser Crest El (sq-ft) : 350.
(acres) : 0.008
Volume at Riser Crest (cu-ft) : 145.
(ac-ft) : 0.003
Infiltration on Bottom and Sideslopes Selected
Soil Properties
Layer No Soil Name Thickness (ft)
1 ASTM 100 0.010
2 SMMWW 6 in/hr (Ecolo 1.500
3 GRAVEL 0.010
KSat Safety Factor: 4.0
Native Soil Infiltration Rate (in/hr) : 3.50
Underdrain Not Present
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
------------------------------------------
Link Name: C3
Link Type: Ecology Bioretention Facility
Downstream Link Name: Block C POC
Floor Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 14.5
Bottom Width (ft) : 3.5
Bottom Slope (ft/ft) : 0.000
Side Slopes (ft/ft) : Z1= 2.50 Z2= 2.50 Z3= 2.50 Z4= 2.50
Bottom Area (sq-ft) : 50.
Area at Riser Crest El (sq-ft) : 101.
(acres) : 0.002
Volume at Riser Crest (cu-ft) : 37.
(ac-ft) : 0.001
Infiltration on Bottom and Sideslopes Selected
Soil Properties
Layer No Soil Name Thickness (ft)
1 ASTM 100 0.010
2 SMMWW 6 in/hr (Ecolo 1.500
3 GRAVEL 0.010
KSat Safety Factor: 2.0
Native Soil Infiltration Rate (in/hr) : 3.50
Underdrain Not Present
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
------------------------------------------
Link Name: C5
Link Type: Ecology Bioretention Facility
Downstream Link Name: Block C POC
Floor Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 59.1
Bottom Width (ft) : 6.6
Bottom Slope (ft/ft) : 0.000
Side Slopes (ft/ft) : Z1= 2.50 Z2= 2.50 Z3= 2.50 Z4= 2.50
Bottom Area (sq-ft) : 390.
Area at Riser Crest El (sq-ft) : 560.
(acres) : 0.013
Volume at Riser Crest (cu-ft) : 237.
(ac-ft) : 0.005
Infiltration on Bottom and Sideslopes Selected
Soil Properties
Layer No Soil Name Thickness (ft)
1 ASTM 100 0.010
2 SMMWW 6 in/hr (Ecolo 1.500
3 GRAVEL 0.010
KSat Safety Factor: 4.0
Native Soil Infiltration Rate (in/hr) : 3.50
Underdrain Not Present
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
------------------------------------------
Link Name: D10
Link Type: Ecology Bioretention Facility
Downstream Link Name: BLOCK D POC
Floor Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 40.0
Bottom Width (ft) : 2.0
Bottom Slope (ft/ft) : 0.000
Side Slopes (ft/ft) : Z1= 2.50 Z2= 2.50 Z3= 2.50 Z4= 2.50
Bottom Area (sq-ft) : 80.
Area at Riser Crest El (sq-ft) : 191.
(acres) : 0.004
Volume at Riser Crest (cu-ft) : 67.
(ac-ft) : 0.002
Infiltration on Bottom and Sideslopes Selected
Soil Properties
Layer No Soil Name Thickness (ft)
1 ASTM 100 0.010
2 SMMWW 6 in/hr (Ecolo 1.500
3 GRAVEL 0.010
KSat Safety Factor: 2.0
Native Soil Infiltration Rate (in/hr) : 3.50
Underdrain Not Present
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
------------------------------------------
Link Name: D9
Link Type: Ecology Bioretention Facility
Downstream Link Name: BLOCK D POC
Floor Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 32.0
Bottom Width (ft) : 5.0
Bottom Slope (ft/ft) : 0.000
Side Slopes (ft/ft) : Z1= 2.50 Z2= 2.50 Z3= 2.50 Z4= 2.50
Bottom Area (sq-ft) : 160.
Area at Riser Crest El (sq-ft) : 259.
(acres) : 0.006
Volume at Riser Crest (cu-ft) : 104.
(ac-ft) : 0.002
Infiltration on Bottom and Sideslopes Selected
Soil Properties
Layer No Soil Name Thickness (ft)
1 ASTM 100 0.010
2 SMMWW 6 in/hr (Ecolo 1.500
3 GRAVEL 0.010
KSat Safety Factor: 4.0
Native Soil Infiltration Rate (in/hr) : 3.50
Underdrain Not Present
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
------------------------------------------
Link Name: D8
Link Type: Ecology Bioretention Facility
Downstream Link Name: BLOCK D POC
Floor Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 47.3
Bottom Width (ft) : 4.0
Bottom Slope (ft/ft) : 0.000
Side Slopes (ft/ft) : Z1= 2.50 Z2= 2.50 Z3= 2.50 Z4= 2.50
Bottom Area (sq-ft) : 189.
Area at Riser Crest El (sq-ft) : 324.
(acres) : 0.007
Volume at Riser Crest (cu-ft) : 128.
(ac-ft) : 0.003
Infiltration on Bottom and Sideslopes Selected
Soil Properties
Layer No Soil Name Thickness (ft)
1 ASTM 100 0.010
2 SMMWW 6 in/hr (Ecolo 1.500
3 GRAVEL 0.010
KSat Safety Factor: 4.0
Native Soil Infiltration Rate (in/hr) : 3.50
Underdrain Not Present
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
------------------------------------------
Link Name: Phase 1 Ex Planter
Link Type: Ecology Bioretention Facility
Downstream Link Name: BLOCK D POC
Floor Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.17
Storage Depth (ft) : 0.17
Bottom Length (ft) : 24.6
Bottom Width (ft) : 3.7
Bottom Slope (ft/ft) : 0.000
Side Slopes (ft/ft) : Z1= 2.50 Z2= 2.50 Z3= 2.50 Z4= 2.50
Bottom Area (sq-ft) : 91.
Area at Riser Crest El (sq-ft) : 116.
(acres) : 0.003
Volume at Riser Crest (cu-ft) : 76.
(ac-ft) : 0.002
Infiltration on Bottom and Sideslopes Selected
Soil Properties
Layer No Soil Name Thickness (ft)
1 ASTM 100 0.010
2 SMMWW 6 in/hr (Ecolo 3.250
3 GRAVEL 0.010
KSat Safety Factor: 2.0
Native Soil Infiltration Rate (in/hr) : 0.70
Underdrain Not Present
Riser Geometry
Riser Structure Type : Rectangular
Riser Length (ft) : 1.67
Riser Width (ft) : 2.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.17 ft
Hydraulic Structure Geometry
Number of Devices: 0
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 11
Number of Links: 13
********** Link: C1 ********** Link WSEL
Stats
WSEL Frequency Data(ft)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) WSEL Peak (ft)
======================================
1.05-Year 100.534
1.11-Year 100.538
1.25-Year 100.543
2.00-Year 100.554
3.33-Year 100.564
5-Year 100.568
10-Year 100.574
25-Year 100.585
50-Year 100.601
100-Year 100.615
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 0.000
_____________________________________
Total: 0.000
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: C1 0.000
Subbasin: C2 2.761
Subbasin: C4 3.306
Subbasin: C6 2.038
Subbasin: C7 3.685
Subbasin: C5 0.000
Subbasin: C3 2.761
Subbasin: D10 0.000
Subbasin: D9 0.000
Subbasin: D8 0.000
Subbasin: D11 2.654
Link: Block C POC Not Applicable
Link: C1 19.972
Link: BLOCK D POC Not Applicable
Link: C2 7.243
Link: C4 19.059
Link: C6 7.178
Link: C7 11.073
Link: C3 4.501
Link: C5 9.232
Link: D10 15.902
Link: D9 6.843
Link: D8 11.657
Link: Phase 1 Ex Planter 1.034
_____________________________________
Total: 130.895
Total Predevelopment Recharge is Less than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 0.000 ac-ft/year, Post Developed: 0.828 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 13
********** Link: C1 **********
2-Year Discharge Rate : 0.067 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.04 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.02 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume Including PPT-Evap (ac-ft): 99.80
Total Runoff Infiltrated (ac-ft): 19.97, 20.01%
Total Runoff Filtered (ac-ft): 70.06, 70.20%
Primary Outflow To Downstream System (ac-ft): 9.28
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.49
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 90.70%
********** Link: C2 **********
Infiltration/Filtration Statistics--------------------
Inflow Volume Including PPT-Evap (ac-ft): 34.42
Total Runoff Infiltrated (ac-ft): 7.24, 21.04%
Total Runoff Filtered (ac-ft): 24.75, 71.91%
Primary Outflow To Downstream System (ac-ft): 2.26
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.17
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 93.44%
********** Link: C4 **********
Infiltration/Filtration Statistics--------------------
Inflow Volume Including PPT-Evap (ac-ft): 138.08
Total Runoff Infiltrated (ac-ft): 19.06, 13.80%
Total Runoff Filtered (ac-ft): 108.37, 78.48%
Primary Outflow To Downstream System (ac-ft): 9.87
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.79
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 92.85%
********** Link: C6 **********
Infiltration/Filtration Statistics--------------------
Inflow Volume Including PPT-Evap (ac-ft): 43.54
Total Runoff Infiltrated (ac-ft): 7.18, 16.48%
Total Runoff Filtered (ac-ft): 34.15, 78.42%
Primary Outflow To Downstream System (ac-ft): 2.10
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.12
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 95.17%
********** Link: C7 **********
Infiltration/Filtration Statistics--------------------
Inflow Volume Including PPT-Evap (ac-ft): 106.70
Total Runoff Infiltrated (ac-ft): 11.07, 10.38%
Total Runoff Filtered (ac-ft): 86.54, 81.11%
Primary Outflow To Downstream System (ac-ft): 8.65
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.44
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 91.90%
********** Link: C3 **********
Infiltration/Filtration Statistics--------------------
Inflow Volume Including PPT-Evap (ac-ft): 34.48
Total Runoff Infiltrated (ac-ft): 4.50, 13.05%
Total Runoff Filtered (ac-ft): 28.82, 83.59%
Primary Outflow To Downstream System (ac-ft): 0.94
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.22
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 97.28%
********** Link: C5 **********
Infiltration/Filtration Statistics--------------------
Inflow Volume Including PPT-Evap (ac-ft): 122.56
Total Runoff Infiltrated (ac-ft): 9.23, 7.53%
Total Runoff Filtered (ac-ft): 107.50, 87.72%
Primary Outflow To Downstream System (ac-ft): 4.82
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 1.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 96.07%
********** Link: D10 **********
Infiltration/Filtration Statistics--------------------
Inflow Volume Including PPT-Evap (ac-ft): 71.69
Total Runoff Infiltrated (ac-ft): 15.90, 22.18%
Total Runoff Filtered (ac-ft): 51.64, 72.03%
Primary Outflow To Downstream System (ac-ft): 3.72
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.43
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 94.81%
********** Link: D9 **********
Infiltration/Filtration Statistics--------------------
Inflow Volume Including PPT-Evap (ac-ft): 60.39
Total Runoff Infiltrated (ac-ft): 6.84, 11.33%
Total Runoff Filtered (ac-ft): 49.88, 82.61%
Primary Outflow To Downstream System (ac-ft): 3.12
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.54
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 94.83%
********** Link: D8 **********
Infiltration/Filtration Statistics--------------------
Inflow Volume Including PPT-Evap (ac-ft): 83.00
Total Runoff Infiltrated (ac-ft): 11.66, 14.05%
Total Runoff Filtered (ac-ft): 65.26, 78.62%
Primary Outflow To Downstream System (ac-ft): 5.62
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.47
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 93.23%
********** Link: Phase 1 Ex Planter **********
Infiltration/Filtration Statistics--------------------
Inflow Volume Including PPT-Evap (ac-ft): 58.38
Total Runoff Infiltrated (ac-ft): 1.03, 1.77%
Total Runoff Filtered (ac-ft): 49.73, 85.18%
Primary Outflow To Downstream System (ac-ft): 5.33
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 2.28
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 90.86%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: C1
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 0.322 2-Year 6.670E-02
5-Year 0.408 5-Year 9.200E-02
10-Year 0.467 10-Year 0.106
25-Year 0.570 25-Year 0.127
50-Year 0.715 50-Year 0.163
100-Year 0.857 100-Year 0.192
200-Year 0.897 200-Year 0.212
500-Year 0.949 500-Year 0.238
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -97.6% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -97.8% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------
EXISTING PLANTER FROM PHASE1 WITH STUB FOR ALLEY G TO BECONFIRMED AFTER COMPLETIONOF AS-BUILTS
Solera Phase 2: Block C and Block D – New Home Co.
Appendix F
Appendix F
Pipe Conveyance
KPFF Consulting Engineers
SOLERA TOWNHOMES
KPFF Consulting Engineers
MAY, 2025
Drainage Calculations - Conveyance Check for the 25-year Storm Event
ASSUMPTIONS AND CONSTANTS
Manning's n =0.014 (per KCSWDM Table 4.2.1 D for Conc. Pipe - Uniform Flow Analysis)
Pr =3.35 in. (for 25-yr 24-hr event per KCSWDM Figure 3.2.1.B)
ar =2.66 (for 25-year event per KCSWDM Table 3.2.1.B)
br =0.65 (for 25-year event per KCSWDM Table 3.2.1.B)
Tc =6.3 minutes (minimum Tc per KCSWDM pg. 3-12)
C impervious =0.90 (per KCSWDM Table 3.2.1.A for Pavement and Roofs)
C pervious =0.25 (per KCSWDM Table 3.2.1.A for Pavement and Roofs)
V min. allow. =3.0 ft/s (for Pipes, per KCSWDM Figure 4.2.1.F)
V max. allow. =5.0 ft/s (for Bioswales and Ditches with less than 6% longitudinal slope, per KCSWDM pg. 6-40)
Min. Cover =36 in. (per King County Road Standards -1993 for Underground Utilities pg. 52)
Layout Contributing Flow Calculations (Rational Method)
Structure Number
Plan
Sheet Alignment Station Offset LT/RT
Impervious
Area
Pervious
Area Area C Tc Tf TcEND i25-yr I25-yr
Contributing
Q QTotal
(sf)(sf)(acres)(min)(min)(min)(in/hr/in)(in/hr)(cfs)(cfs)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
0
CB #14 ALLEY B 49+19.51 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.06 6.36 0.80 2.68 in/hr 0.13 cfs 0.13 cfs
CB #12A ALLEY D 69+81.42 -229.28 1,866 sf 3,462 sf 0.12 ac 0.48 6.3 0.07 6.37 0.80 2.68 in/hr 0.16 cfs 0.16 cfs
CB #13 ALLEY B 48+97.54 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.23 6.59 0.78 2.62 in/hr 0.00 cfs 0.13 cfs
CB #12 ALLEY B 48+15.52 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.21 6.80 0.77 2.56 in/hr 0.05 cfs 0.33 cfs
CB #11 ALLEY B 47+41.79 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.12 6.91 0.76 2.54 in/hr 0.00 cfs 0.33 cfs
CB #9A ALLEY D 69+65.85 -81.58 4,330 sf 3,070 sf 0.17 ac 0.63 6.3 0.11 6.41 0.80 2.66 in/hr 0.29 cfs 0.29 cfs
CB #10 ALLEY B 47+00.69 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.11 6.52 0.79 2.63 in/hr 0.13 cfs 0.42 cfs
CB #9 ALLEY B 46+61.86 -0.05 0 sf 0 sf 0.00 ac 0.00 6.3 0.14 6.66 0.78 2.60 in/hr 0.00 cfs 0.42 cfs
CB #8 ALLEY B 46+12.50 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.07 6.73 0.77 2.58 in/hr 0.16 cfs 0.57 cfs
CB #7 ALLEY B 45+86.48 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.17 6.90 0.76 2.54 in/hr 0.00 cfs 0.57 cfs
CB #6 ALLEY B 45+24.71 -0.01 4,095 sf 0 sf 0.09 ac 0.90 6.3 0.04 6.95 0.75 2.53 in/hr 0.26 cfs 0.83 cfs
CB #5 ALLEY B 45+09.02 0 1,570 sf 2,177 sf 0.09 ac 0.52 6.3 0.03 6.97 0.75 2.52 in/hr 0.11 cfs 0.94 cfs
CB #4 ALLEY B 44+99.97 0.01 0 sf 0 sf 0.00 ac 0.00 6.3 0.18 7.15 0.74 2.48 in/hr 0.05 cfs 0.99 cfs
CB #3 ALLEY B 44+36.35 0 8,534 sf 0 sf 0.20 ac 0.90 6.3 0.10 7.25 0.73 2.46 in/hr 0.43 cfs 1.43 cfs
CB #2 ALLEY A 30+56.91 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.02 7.27 0.73 2.45 in/hr 0.13 cfs 1.55 cfs
CB #1 ALLEY A 30+59.92 11.37 0 sf 0 sf 0.00 ac 0.00 6.3 0.11 7.38 0.73 2.43 in/hr 0.00 cfs 1.55 cfs
BLOCK D
CB #18A ALLEY D 69+67.13 -604.64 1,398 sf 3,198 sf 0.11 ac 0.45 6.3 0.10 6.40 0.80 2.67 in/hr 0.13 cfs 0.13 cfs
CB #19 ALLEY C 53+06.81 -8.35 0 sf 0 sf 0.00 ac 0.00 6.3 0.43 6.84 0.76 2.55 in/hr 0.10 cfs 0.23 cfs
CB #18 ALLEY C 52+01.75 4.76 2,871 sf 0 sf 0.07 ac 0.90 6.3 0.39 7.23 0.74 2.46 in/hr 0.23 cfs 0.46 cfs
CB #17 ALLEY C 51+03.42 0 3,483 sf 0 sf 0.08 ac 0.90 6.3 0.24 7.47 0.72 2.41 in/hr 0.17 cfs 0.63 cfs
CB #16 ALLEY C 50+43.42 0 2,871 sf 0 sf 0.07 ac 0.90 6.3 0.05 7.52 0.72 2.40 in/hr 0.27 cfs 0.90 cfs
CB #15 ALLEY C 50+33.31 -6.75 0 sf 0 sf 0.00 ac 0.00 6.3 0.16 7.68 0.71 2.37 in/hr 0.00 cfs 0.90 cfs
Solera Townhomes Conveyance Spreadsheet | 25yr UF 3 of 29 5/23/2025 | 10:35 AM
KPFF Consulting Engineers
SOLERA TOWNHOMES
KPFF Consulting Engineers
MAY, 2025
Layout
Structure Number
1
0
CB #14
CB #12A
CB #13
CB #12
CB #11
CB #9A
CB #10
CB #9
CB #8
CB #7
CB #6
CB #5
CB #4
CB #3
CB #2
CB #1
BLOCK D
CB #18A
CB #19
CB #18
CB #17
CB #16
CB #15
ASSUMPTIONS AND CONSTANTS cont.
8 -in Pipe Wall Thickness =2.0 in. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
12 -in Pipe Wall Thickness =2.0 in. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
18 -in Pipe Wall Thickness =2.5 in. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
24 -in Pipe Wall Thickness =3.0 in. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
30 -in Pipe Wall Thickness =4.0 in. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
Min Cover for Plain Conc. Pipe =1.5 ft. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
Min Cover for Class IV Conc. Pipe =1.0 ft. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
Min Cover for Class V Conc. Pipe =0.5 ft. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
Project Pavement Thickness =0.875 ft. (per XXXXX)
Pipe Capacity Calculations Conveyance Checks
Inlet Rim
Elevation
Outlet Rim
Elevation
Inlet Invert
Elevation
Outlet Invert
Elevation
Pipe
Diameter Length Slope Velocity, V
Pipe Flow
Capacity, Q Inlet Cover
Outlet
Cover
Structure
Type Structure
Diameter
Rim to
Invert Pipe Type
Pipe
Capacity
Used VFull Check Q Check Inlet Cover
Outlet
Cover
(inches)(feet)(%)(ft/s)(cfs)(ft)(ft)(in)(ft)(%)
18 19 20 21 22 23 24 27 28 29 30 31 32 34 35 36 37 38 39
352 sf 351.37 347.73 347.29 12 in 22.0 ft 2.00% 5.96 ft/s 4.68 cfs 2.9 ft 2.9 ft CB1 -4.1 ft Plain 2.8%OK OK Check Check
350.17 349.73 346.36 345.98 8 in 18.6 ft 2.03% 4.58 ft/s 1.60 cfs 3.0 ft 2.9 ft CB1 -3.8 ft Plain 9.8%OK OK Check Check
351.37 349.73 347.29 345.65 12 in 82.0 ft 2.00% 5.96 ft/s 4.68 cfs 2.9 ft 2.9 ft CB1 -4.1 ft Plain 2.8%OK OK Check Check
349.73 348.26 345.65 344.18 12 in 73.7 ft 1.99% 5.95 ft/s 4.67 cfs 2.9 ft 2.9 ft CB1 -4.1 ft Plain 7.1%OK OK Check Check
348.26 347.43 344.18 343.36 12 in 41.1 ft 2.00% 5.95 ft/s 4.67 cfs 2.9 ft 2.9 ft CB1 -4.1 ft Plain 7.1%OK OK Check Check
348.15 346.77 343.82 342.91 8 in 34.7 ft 2.62% 5.20 ft/s 1.81 cfs 3.5 ft 3.0 ft CB1 -4.3 ft Plain 15.7%OK OK OK OK
347.43 346.77 343.36 342.58 12 in 38.8 ft 2.01% 5.97 ft/s 4.69 cfs 2.9 ft 3.0 ft CB1 -4.1 ft Plain 8.9%OK OK Check OK
346.77 346.03 342.58 341.59 12 in 49.4 ft 2.01% 5.97 ft/s 4.69 cfs 3.0 ft 3.3 ft CB1 -4.2 ft Plain 8.9%OK OK OK OK
346.03 345.64 341.59 341.07 12 in 26.0 ft 2.00% 5.95 ft/s 4.68 cfs 3.3 ft 3.4 ft CB1 -4.4 ft Plain 12.2%OK OK OK OK
345.64 344.71 341.07 339.83 12 in 61.8 ft 2.01% 5.97 ft/s 4.69 cfs 3.4 ft 3.7 ft CB1 -4.6 ft Plain 12.2%OK OK OK OK
344.71 344.47 339.83 339.52 12 in 15.7 ft 1.98% 5.92 ft/s 4.65 cfs 3.7 ft 3.8 ft CB1 -4.9 ft Plain 17.9%OK OK OK OK
344.47 344.34 339.52 339.34 12 in 9.1 ft 1.99% 5.94 ft/s 4.67 cfs 3.8 ft 3.8 ft CB1 -5.0 ft Plain 20.2%OK OK OK OK
344.34 343.34 339.34 338.07 12 in 63.6 ft 2.00% 5.95 ft/s 4.67 cfs 3.8 ft 4.1 ft CB1 -5.0 ft Plain 21.2%OK OK OK OK
343.34 342.41 338.07 334.91 12 in 56.9 ft 5.55% 9.93 ft/s 7.80 cfs 4.1 ft 6.3 ft CB2 48 5.3 ft Plain 18.3%OK OK OK OK
342.41 342.50 334.91 334.34 12 in 11.8 ft 4.85% 9.27 ft/s 7.28 cfs 6.3 ft 7.0 ft CB2 48 7.5 ft Plain 21.3%OK OK OK OK
342.5 341.23 334.34 334.05 12.0 ft 29.0 ft 1.00% 4.21 ft/s 3.31 cfs 7.0 ft 6.0 ft CB2 48 8.2 ft Plain 46.9%OK OK OK OK
356.57 357.09 352.43 351.38 8 in 34.9 ft 3.00% 5.57 ft/s 1.94 cfs 3.3 ft 4.9 ft CB1 -4.1 ft Plain 6.5%OK OK OK OK
357.21 357.09 352.15 351.05 12 in 109.7 ft 1.00% 4.22 ft/s 3.31 cfs 3.9 ft 4.9 ft CB2 48 5.1 ft Plain 6.9%OK OK OK OK
357.09 354.79 351.05 350.06 12 in 99.3 ft 1.00% 4.21 ft/s 3.30 cfs 4.9 ft 3.6 ft CB2 48 6.0 ft Plain 13.8%OK OK OK OK
354.79 353.28 350.06 349.46 12 in 60.0 ft 1.00% 4.21 ft/s 3.31 cfs 3.6 ft 2.7 ft CB1 -4.7 ft Plain 19.0%OK OK OK Check
353.28 352.82 349.46 349.34 12 in 12.2 ft 0.99% 4.19 ft/s 3.29 cfs 2.7 ft 2.3 ft CB1 -3.8 ft Class IV 27.3%OK OK Check Check
352.82 351.97 349.34 348.86 12 in 43.0 ft 1.12% 4.45 ft/s 3.50 cfs 2.3 ft 1.9 ft CB1 -3.5 ft Class IV 25.7%OK OK Check Check
Solera Townhomes Conveyance Spreadsheet | 25yr UF 4 of 29 5/23/2025 | 10:35 AM
KPFF Consulting Engineers
SOLERA TOWNHOMES
KPFF Consulting Engineers
MAY, 2025
Drainage Calculations - Conveyance Check for the 100-year Storm Event
ASSUMPTIONS AND CONSTANTS
Manning's n = 0.014 (per KCSWDM Table 4.2.1 D for Conc. Pipe - Uniform Flow Analysis)
Pr =4.15 in. (for 25-yr 24-hr event per KCSWDM Figure 3.2.1.B)
ar =2.61 (for 25-year event per KCSWDM Table 3.2.1.B)
br =0.63 (for 25-year event per KCSWDM Table 3.2.1.B)
Tc = 6.3 minutes (minimum Tc per KCSWDM pg. 3-12)
C impervious = 0.90 (per KCSWDM Table 3.2.1.A for Pavement and Roofs)
C pervious = 0.25 (per KCSWDM Table 3.2.1.A for Pavement and Roofs)
V min. allow. = 3.0 ft/s (for Pipes, per KCSWDM Figure 4.2.1.F)
V max. allow. = 5.0 ft/s (for Bioswales and Ditches with less than 6% longitudinal slope, per KCSWDM pg. 6-40)
Min. Cover = 36 in. (per King County Road Standards -1993 for Underground Utilities pg. 52)
Layout Contributing Flow Calculations (Rational Method)
Structure Number
Plan
Sheet Alignment Station Offset LT/RT
Impervious
Area
Pervious
Area Area C Tc Tf TcEND i25-yr I25-yr
Contributing
Q QTotal
(sf)(sf)(acres)(min)(min)(min)(in/hr/in)(in/hr)(cfs)(cfs)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
0
0
0
CB #14 GD- ALLEY B 49+19.51 0.0 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.06 6.36 0.81 3.38 in/hr 0.20 cfs 0.20 cfs
CB #12A GD- ALLEY D 69+81.42 -229.3 0 1,866 sf 3,462 sf 0.12 ac 0.48 6.3 0.07 6.37 0.81 3.37 in/hr 0.20 cfs 0.20 cfs
CB #13 GD- ALLEY B 48+97.54 0.0 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.23 6.59 0.80 3.30 in/hr 0.00 cfs 0.20 cfs
CB #12 GD- ALLEY B 48+15.52 0.0 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.21 6.80 0.78 3.24 in/hr 0.09 cfs 0.49 cfs
CB #11 GD- ALLEY B 47+41.79 0.0 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.12 6.91 0.77 3.20 in/hr 0.00 cfs 0.49 cfs
CB #9A GD- ALLEY D 69+65.85 -81.6 0 4,330 sf 3,070 sf 0.17 ac 0.63 6.3 0.11 6.41 0.81 3.36 in/hr 0.36 cfs 0.36 cfs
CB #10 GD- ALLEY B 47+00.69 0.0 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.11 7.02 0.76 3.17 in/hr 0.19 cfs 0.68 cfs
CB #9 GD- ALLEY B 46+61.86 -0.1 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.14 7.16 0.76 3.13 in/hr 0.00 cfs 1.04 cfs
CB #8 GD- ALLEY B 46+12.50 0.0 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.07 7.23 0.75 3.11 in/hr 0.23 cfs 1.27 cfs
CB #7 GD- ALLEY B 45+86.48 0.0 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.17 7.40 0.74 3.07 in/hr 0.00 cfs 1.27 cfs
CB #6 GD- ALLEY B 45+24.71 0.0 0 4,095 sf 0 sf 0.09 ac 0.90 6.3 0.04 7.45 0.74 3.06 in/hr 0.33 cfs 1.60 cfs
CB #5 GD- ALLEY B 45+09.02 0.0 0 1,570 sf 2,177 sf 0.09 ac 0.52 6.3 0.03 7.47 0.74 3.05 in/hr 0.14 cfs 1.74 cfs
CB #4 GD- ALLEY B 44+99.97 0.0 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.18 7.65 0.72 3.01 in/hr 0.07 cfs 1.81 cfs
CB #3 GD- ALLEY B 44+36.35 0.0 0 8,534 sf 0 sf 0.20 ac 0.90 6.3 0.10 7.75 0.72 2.98 in/hr 0.53 cfs 2.33 cfs
CB #2 GD- ALLEY A 30+56.91 0.0 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.02 7.77 0.72 2.98 in/hr 0.19 cfs 2.53 cfs
CB #1 GD- ALLEY A 30+59.92 11.4 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.11 7.88 0.71 2.95 in/hr 0.00 cfs 2.53 cfs
BLOCK D
CB #18A GD- ALLEY D 69+67.13 -604.6 0 1,398 sf 3,198 sf 0.11 ac 0.45 6.3 0.10 6.40 0.81 3.36 in/hr 0.16 cfs 0.16 cfs
CB #19 GD- ALLEY C 53+06.81 -8.4 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.43 6.73 0.78 3.26 in/hr 0.15 cfs 0.15 cfs
CB #18 GD- ALLEY C 52+01.75 4.8 0 2,871 sf 0 sf 0.07 ac 0.90 6.3 0.39 7.13 0.76 3.14 in/hr 0.31 cfs 0.63 cfs
CB #17 GD- ALLEY C 51+03.42 0.0 0 3,483 sf 0 sf 0.08 ac 0.90 6.3 0.24 7.36 0.74 3.08 in/hr 0.22 cfs 0.85 cfs
CB #16 GD- ALLEY C 50+43.42 0.0 0 2,871 sf 0 sf 0.07 ac 0.90 6.3 0.05 7.41 0.74 3.07 in/hr 0.36 cfs 1.21 cfs
CB #15 GD- ALLEY C 50+33.31 -6.8 0 0 sf 0 sf 0.00 ac 0.00 6.3 0.16 7.57 0.73 3.02 in/hr 0.00 cfs 1.21 cfs
Solera Townhomes Conveyance Spreadsheet | 100yr UF 7 of 29 5/23/2025 | 10:35 AM
KPFF Consulting Engineers
SOLERA TOWNHOMES
KPFF Consulting Engineers
MAY, 2025
Layout
Structure Number
1
0
0
0
CB #14
CB #12A
CB #13
CB #12
CB #11
CB #9A
CB #10
CB #9
CB #8
CB #7
CB #6
CB #5
CB #4
CB #3
CB #2
CB #1
BLOCK D
CB #18A
CB #19
CB #18
CB #17
CB #16
CB #15
ASSUMPTIONS AND CONSTANTS cont.
8 -in Pipe Wall Thickness = 2.0 in. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
12 -in Pipe Wall Thickness = 2.0 in. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
18 -in Pipe Wall Thickness = 2.5 in. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
24 -in Pipe Wall Thickness = 3.0 in. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
30 -in Pipe Wall Thickness = 4.0 in. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
Min Cover for Plain Conc. Pipe = 1.5 ft. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
Min Cover for Class IV Conc. Pipe = 1.0 ft. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
Min Cover for Class V Conc. Pipe = 0.5 ft. (per WSDOT Hydraulics Manual Table 8-11.2 (English))
Project Pavement Thickness = 0.875 ft. (per XXXXX)
Pipe Capacity Calculations Conveyance Checks
Inlet Rim
Elevation
Outlet Rim
Elevation
Inlet Invert
Elevation
Outlet Invert
Elevation
Pipe
Diameter Length Slope Velocity, V
Pipe Flow
Capacity, Q Inlet Cover
Outlet
Cover
Structure
Type Structure
Diameter
Rim to
Invert Pipe Type
Pipe
Capacity
Used VFull Check Q Check Inlet Cover
Outlet
Cover
(inches)(feet)(%)(ft/s)(cfs)(ft)(ft)(in)(ft)(%)
18 19 20 21 22 23 24 27 28 29 30 31 32 34 35 36 37 38 39
351.81 351.37 347.73 347.29 12 in 22.0 ft 2.00% 5.96 ft/s 4.68 cfs 2.9 ft 3.1 ft CB1 -4.1 ft Plain 4.3%OK OK Check OK
350.17 349.73 346.36 345.98 8 in 18.6 ft 2.03% 4.58 ft/s 1.60 cfs 3.0 ft 3.1 ft CB1 -3.8 ft Plain 12.3%OK OK Check OK
351.37 349.73 347.29 345.65 12 in 82.0 ft 2.00% 5.96 ft/s 4.68 cfs 2.9 ft 3.1 ft CB1 -4.1 ft Plain 4.3%OK OK Check OK
349.73 348.26 345.65 344.18 12 in 73.7 ft 1.99% 5.95 ft/s 4.67 cfs 2.9 ft 3.1 ft CB1 -4.1 ft Plain 10.5%OK OK Check OK
348.26 347.43 344.18 343.36 12 in 41.1 ft 2.00% 5.95 ft/s 4.67 cfs 2.9 ft 3.1 ft CB1 -4.1 ft Plain 10.5%OK OK Check OK
348.15 346.77 343.82 342.91 8 in 34.7 ft 2.62% 5.20 ft/s 1.81 cfs 3.5 ft 3.2 ft CB1 -4.3 ft Plain 19.8%OK OK OK OK
347.43 346.77 343.36 342.58 12 in 38.8 ft 2.01% 5.97 ft/s 4.69 cfs 2.9 ft 3.2 ft CB1 -4.1 ft Plain 14.5%OK OK Check OK
346.77 346.03 342.58 341.59 12 in 49.4 ft 2.01% 5.97 ft/s 4.69 cfs 3.0 ft 3.4 ft CB1 -4.2 ft Plain 22.2%OK OK OK OK
346.03 345.64 341.59 341.07 12 in 26.0 ft 2.00% 5.95 ft/s 4.68 cfs 3.3 ft 3.6 ft CB1 -4.4 ft Plain 27.2%OK OK OK OK
345.64 344.71 341.07 339.83 12 in 61.8 ft 2.01% 5.97 ft/s 4.69 cfs 3.4 ft 3.9 ft CB1 -4.6 ft Plain 27.1%OK OK OK OK
344.71 344.47 339.83 339.52 12 in 15.7 ft 1.98% 5.92 ft/s 4.65 cfs 3.7 ft 4.0 ft CB1 -4.9 ft Plain 34.5%OK OK OK OK
344.47 344.34 339.52 339.34 12 in 9.1 ft 1.99% 5.94 ft/s 4.67 cfs 3.8 ft 4.0 ft CB1 -5.0 ft Plain 37.3%OK OK OK OK
344.34 343.34 339.34 338.07 12 in 63.6 ft 2.00% 5.95 ft/s 4.67 cfs 3.8 ft 4.3 ft CB1 -5.0 ft Plain 38.7%OK OK OK OK
343.34 342.41 338.07 334.91 12 in 56.9 ft 5.55% 9.93 ft/s 7.80 cfs 4.1 ft 6.5 ft CB2 48 5.3 ft Plain 29.9%OK OK OK OK
342.41 342.50 334.91 334.34 12 in 11.8 ft 4.85% 9.27 ft/s 7.28 cfs 6.3 ft 7.2 ft CB2 48 7.5 ft Plain 34.7%OK OK OK OK
342.50 341.23 334.34 334.05 12 in 29.0 ft 1.00% 4.21 ft/s 3.31 cfs 7.0 ft 6.2 ft CB2 48 8.2 ft Plain 76.3%OK OK OK OK
356.57 357.09 352.43 351.38 8 in 34.9 ft 3.00% 5.57 ft/s 1.94 cfs 3.3 ft 5.0 ft CB1 -4.1 ft Plain 8.2%OK OK OK OK
357.21 357.09 352.15 351.05 12 in 109.7 ft 1.00% 4.22 ft/s 3.31 cfs 3.9 ft 5.0 ft CB2 48 5.1 ft Plain 4.6%OK OK OK OK
357.09 354.79 351.05 350.06 12 in 99.3 ft 1.00% 4.21 ft/s 3.30 cfs 4.9 ft 3.7 ft CB2 48 6.0 ft Plain 18.9%OK OK OK OK
354.79 353.28 350.06 349.46 12 in 60.0 ft 1.00% 4.21 ft/s 3.31 cfs 3.6 ft 2.8 ft CB1 -4.7 ft Plain 25.6%OK OK OK Check
353.28 352.82 349.46 349.34 12 in 12.2 ft 0.99% 4.19 ft/s 3.29 cfs 2.7 ft 2.5 ft CB1 -3.8 ft Plain 36.8%OK OK Check Check
352.82 351.97 349.34 348.86 12 in 43.0 ft 1.12% 4.45 ft/s 3.50 cfs 2.3 ft 2.1 ft CB1 -3.5 ft Class IV 34.6%OK OK Check Check
Solera Townhomes Conveyance Spreadsheet | 100yr UF 8 of 29 5/23/2025 | 10:35 AM
KPFF Consulting Engineers
SOLERA TOWNHOMES
KPFF Consulting Engineers
MAY, 2025
Drainage Calculations - Backwater Analysis for the 25-year Storm Event
ASSUMPTIONS AND CONSTANTS
Manning's n =0.012 (per KCSWDM Table 4.2.1 D for PVC Pipe - Backwater Flow Anaysis)
Inlet Control Analysis = Assumed concrete pipe, square edge with headwall
*If Q/(AD^0.5)<=3.5, unsubmerged inlet conditions. If Q/(AD^0.5)>=4.0, submerged conditions (See KCSWDM pg.4-37)
Unsubmerged : Submerged :
K =0.0098 c =0.0398 (per KCSWDM Table 4.3.1.A for Circular Concrete Pipe - Square Edge with Headwall Equation Form 1)
M =2.0 Y =0.67 (per KCSWDM Table 4.3.1.A for Circular Concrete Pipe - Square Edge with Headwall Equation Form 1)
Bend Head Loss Coeff., Kb =1.23 (per KCSWDM Figure 4.2.1.K for 90° Bend at a Manhole, no Special Shaping)
Entrance Loss Coef., Ke =0.5 ( per KCSWDM Table 4.3.1.B for Square-Cut End Concrete Pipe)
g =32.2 ft/s2 - acceleration due to gravity
Layout Pipe Sytem Design Backwater Calculation
Structure Number
Design Flow,
Q Length Pipe Size "n" Value Slope Outlet El Inlet Elev Q/(AD^0.5)*
Inlet
Controlled
Condition Q2Bc/(gAc3)Critical Depth
Critical
Velocity Barrel Area
Barrel
Velocity
Barrel Vel
Head
(cfs)(ft)(in)(%)(ft)(ft)(ft)(fps)(sf)(fps)(ft)
1 2 3 4 5 6 7 8 9 10 14 15 16 17 18 19
0
0
0
CB #14 0.13 21.97 12 0.012 2.00% 347.29 347.73 0.167 Unsubmerged 1.00 0.15 1.81 0.785 0.167 0.0004
CB #12A 0.16 18.58 8 0.012 2.03% 345.98 346.36 0.548 Unsubmerged 0.99 0.18 2.04 0.349 0.448 0.0031
CB #13 0.13 82.02 12 0.012 2.00% 345.65 347.29 0.167 Unsubmerged 1.00 0.15 1.81 0.785 0.167 0.0004
CB #12 0.33 73.73 12 0.012 1.99% 344.18 345.65 0.424 Unsubmerged 1.00 0.24 2.32 0.785 0.424 0.0028
CB #11 0.33 41.10 12 0.012 2.00% 343.36 344.18 0.424 Unsubmerged 1.00 0.24 2.32 0.785 0.424 0.0028
CB #9A 0.29 34.66 8 0.012 2.62% 342.91 343.82 1.001 Unsubmerged 1.01 0.25 2.43 0.349 0.817 0.0104
CB #10 0.42 38.84 12 0.012 2.01% 342.58 343.36 0.529 Unsubmerged 1.01 0.27 2.48 0.785 0.529 0.0043
CB #9 0.42 49.36 12 0.012 2.01% 341.59 342.58 0.529 Unsubmerged 1.01 0.27 2.48 0.785 0.529 0.0043
CB #8 0.57 26.02 12 0.012 2.00% 341.07 341.59 0.729 Unsubmerged 1.01 0.31 2.71 0.785 0.729 0.0082
CB #7 0.57 61.76 12 0.012 2.01% 339.83 341.07 0.729 Unsubmerged 1.01 0.31 2.71 0.785 0.729 0.0082
CB #6 0.83 15.69 12 0.012 1.98% 339.52 339.83 1.057 Unsubmerged 1.01 0.38 3.03 0.785 1.057 0.0174
CB #5 0.94 9.05 12 0.012 1.99% 339.34 339.52 1.202 Unsubmerged 1.01 0.41 3.15 0.785 1.202 0.0224
CB #4 0.99 63.62 12 0.012 2.00% 338.07 339.34 1.262 Unsubmerged 1.01 0.42 3.19 0.785 1.262 0.0247
CB #3 1.43 56.91 12 0.012 5.55% 334.91 338.07 1.815 Unsubmerged 1.01 0.50 3.59 0.785 1.815 0.0511
CB #2 1.55 11.76 12 0.012 4.85% 334.34 334.91 1.976 Unsubmerged 1.01 0.53 3.69 0.785 1.976 0.0606
CB #1 1.55 29.00 12 0.012 1.00% 334.05 334.34 1.976 Unsubmerged 1.01 0.53 3.69 0.785 1.976 0.0606
BLOCK D
CB #18A 0.13 34.86 8 0.012 3.00% 351.38 352.43 0.442 Unsubmerged 0.99 0.16 1.92 0.349 0.361 0.0020
CB #19 0.23 109.74 12 0.012 1.00% 351.05 352.15 0.289 Unsubmerged 1.00 0.20 2.09 0.785 0.289 0.0013
CB #18 0.46 99.28 12 0.012 1.00% 350.06 351.05 0.581 Unsubmerged 1.00 0.28 2.54 0.785 0.581 0.0052
CB #17 0.63 60.00 12 0.012 1.00% 349.46 350.06 0.802 Unsubmerged 1.00 0.33 2.78 0.785 0.802 0.0100
CB #16 0.90 12.15 12 0.012 0.99% 349.34 349.46 1.145 Unsubmerged 1.00 0.40 3.09 0.785 1.145 0.0204
CB #15 0.90 43.00 12 0.012 1.12% 348.86 349.34 1.145 Unsubmerged 1.00 0.40 3.09 0.785 1.145 0.0204
Solera Townhomes Conveyance Spreadsheet | 25yr BW 11 of 29 5/23/2025 | 10:35 AM
KPFF Consulting Engineers
SOLERA TOWNHOMES
KPFF Consulting Engineers
MAY, 2025
Layout
Structure Number
1
0
0
0
CB #14
CB #12A
CB #13
CB #12
CB #11
CB #9A
CB #10
CB #9
CB #8
CB #7
CB #6
CB #5
CB #4
CB #3
CB #2
CB #1
BLOCK D
CB #18A
CB #19
CB #18
CB #17
CB #16
CB #15
Drainage Calculations - Backwater Analysis for the 25-year Storm Event
ASSUMPTIONS AND CONSTANTS
Manning's n = 0.012 (per KCSWDM Table 4.2.1 D for PVC Pipe - Backwater Flow Anaysis)
Inlet Control Analysis = Assumed concrete pipe, square edge with headwall
*If Q/(AD^0.5)<=3.5, unsubmerged inlet conditions. If Q/(AD^0.5)>=4.0, submerged conditions (See KCSWDM pg.4-37)
Unsubmerged : Submerged :
K = 0.0098 c = 0.0398
M = 2.0 Y = 0.67 (per KCSWDM Table 4.3.1.A for Circular Concrete Pipe - Square Edge with Headwall Equation Form 1)
Bend Head Loss Coeff., Kb = 1.23 (per KCSWDM Figure 4.2.1.K for 90° Bend at a Manhole, no Special Shaping)(per KCSWDM Table 4.3.1.A for Circular Concrete Pipe - Square Edge with Headwall Equation Form 1)
Entrance Loss Coef., Ke = 0.5 ( per KCSWDM Table 4.3.1.B for Square-Cut End Concrete Pipe)
g = 32.2 ft/s2 - acceleration due to gravity
Checks
TW Elev
Hydraulic
Radius Friction Loss
Entrance HGL
Elev
Entrance
Head Loss
Exit Head
Loss
Outlet
Control Elev
Inlet Control
Elev*
Inlet or Outlet
Controlled?
Approach
Velocity Head
Bend Head
Loss
Junction
Loss Coeff.,
Kj
Junction
Head Loss HW Elev CB Rim Elev
Overtopping
Check
Clearance
btwn Rim and
HGL
(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)
20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
347.48 0.250 0.0003 347.48 0.0002 0.0004 347.48 347.92 Inlet 0.000 0.0000 0.00 0.0000 347.92 351.81 OK 3.89
345.97 0.167 0.0026 345.97 0.0016 0.0031 345.97 346.60 Inlet 0.000 0.0000 0.00 0.0000 346.60 350.17 OK 3.57
345.97 0.250 0.0009 345.97 0.0002 0.0004 345.97 347.48 Inlet 0.000 0.0005 0.00 0.0000 347.48 351.37 OK 3.89
344.49 0.250 0.0054 344.50 0.0014 0.0028 344.50 345.96 Inlet 0.003 0.0038 0.62 0.0019 345.97 349.73 OK 3.76
343.71 0.250 0.0030 343.72 0.0014 0.0028 343.72 344.49 Inlet 0.003 0.0000 0.00 0.0000 344.49 348.26 OK 3.77
342.94 0.167 0.0163 342.96 0.0052 0.0104 342.97 344.16 Inlet 0.000 0.0000 0.00 0.0000 344.16 348.15 OK 3.99
342.94 0.250 0.0044 342.95 0.0022 0.0043 342.95 343.71 Inlet 0.003 0.0034 0.00 0.0000 343.71 347.43 OK 3.72
342.01 0.250 0.0057 342.01 0.0022 0.0043 342.02 342.93 Inlet 0.010 0.0127 0.43 0.0044 342.94 346.77 OK 3.83
341.49 0.250 0.0057 341.49 0.0041 0.0082 341.50 342.01 Inlet 0.004 0.0000 0.00 0.0000 342.01 346.03 OK 4.02
340.35 0.250 0.0134 340.36 0.0041 0.0082 340.37 341.49 Inlet 0.008 0.0000 0.00 0.0000 341.49 345.64 OK 4.15
340.07 0.250 0.0072 340.07 0.0087 0.0174 340.10 340.35 Inlet 0.008 0.0000 0.00 0.0000 340.35 344.71 OK 4.36
339.90 0.250 0.0054 339.90 0.0112 0.0224 339.94 340.08 Inlet 0.017 0.0000 0.00 0.0000 340.07 344.47 OK 4.40
338.75 0.250 0.0416 338.80 0.0124 0.0247 338.83 339.92 Inlet 0.022 0.0000 0.00 0.0000 339.90 344.34 OK 4.44
335.61 0.250 0.0768 335.69 0.0256 0.0511 335.77 338.78 Inlet 0.025 0.0000 0.00 0.0000 338.75 343.34 OK 4.59
335.05 0.250 0.0188 335.07 0.0303 0.0606 335.16 335.66 Inlet 0.051 0.0000 0.00 0.0000 335.61 342.41 OK 6.80
0.00 0.250 0.0464 0.05 0.0303 0.0606 0.14 335.11 Inlet 0.061 0.0000 0.00 0.0000 335.05 342.50 OK 7.45
351.43 0.167 0.0032 351.43 0.0010 0.0020 351.44 352.64 Inlet 0.000 0.0000 0.00 0.0000 352.64 356.57 OK 3.93
351.43 0.250 0.0038 351.43 0.0006 0.0013 351.43 352.41 Inlet 0.000 0.0000 0.00 0.0000 352.41 357.21 OK 4.80
350.51 0.250 0.0137 350.52 0.0026 0.0052 350.53 351.43 Inlet 0.002 0.0025 0.36 0.0007 351.43 357.09 OK 5.66
350.00 0.250 0.0158 350.02 0.0050 0.0100 350.03 350.51 Inlet 0.005 0.0000 0.00 0.0000 350.51 354.79 OK 4.28
349.87 0.250 0.0065 349.88 0.0102 0.0204 349.91 350.01 Inlet 0.010 0.0000 0.00 0.0000 350.00 353.28 OK 3.28
0.00 0.250 0.0231 0.02 0.0102 0.0204 0.05 349.89 Inlet 0.020 0.0000 0.00 0.0000 349.87 352.82 OK 2.95
Solera Townhomes Conveyance Spreadsheet | 25yr BW 12 of 29 5/23/2025 | 10:35 AM
KPFF Consulting Engineers
Layout Pipe Sytem Design Backwater Calculation
Structure Number
Design Flow,
Q Length Pipe Size "n" Value Slope Outlet El Inlet Elev Q/(AD^0.5)*
Inlet
Controlled
Condition Q2Bc/(gAc
3)Critical Depth
Critical
Velocity Barrel Area
Barrel
Velocity
Barrel Vel
Head
(cfs)(ft)(in)(%)(ft)(ft)(ft)(fps)(sf)(fps)(ft)
Solera Townhomes Conveyance Spreadsheet | 25yr BW 13 of 29 5/23/2025 | 10:35 AM
KPFF Consulting Engineers
Layout
Structure Number
Checks
TW Elev
Hydraulic
Radius Friction Loss
Entrance HGL
Elev
Entrance
Head Loss
Exit Head
Loss
Outlet
Control Elev
Inlet Control
Elev*
Inlet or Outlet
Controlled?
Approach
Velocity Head
Bend Head
Loss
Junction
Loss Coeff.,
Kj
Junction
Head Loss HW Elev CB Rim Elev
Overtopping
Check
Clearance
btwn Rim and
HGL
(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)
Solera Townhomes Conveyance Spreadsheet | 25yr BW 14 of 29 5/23/2025 | 10:35 AM
KPFF Consulting Engineers
SOLERA TOWNHOMES
KPFF Consulting Engineers
MAY, 2025
Drainage Calculations - Backwater Analysis for the 100-year Storm Event
ASSUMPTIONS AND CONSTANTS
Manning's n = 0.012 (per KCSWDM Table 4.2.1 D for PVC Pipe - Backwater Flow Anaysis)
Inlet Control Analysis = Assumed concrete pipe, square edge with headwall
*If Q/(AD^0.5)<=3.5, unsubmerged inlet conditions. If Q/(AD^0.5)>=4.0, submerged conditions (See KCSWDM pg.4-37)
Unsubmerged : Submerged :
K = 0.0098 c = 0.0398 (per KCSWDM Table 4.3.1.A for Circular Concrete Pipe - Square Edge with Headwall Equation Form 1)
M = 2 Y = 0.67 (per KCSWDM Table 4.3.1.A for Circular Concrete Pipe - Square Edge with Headwall Equation Form 1)
Bend Head Loss Coeff., Kb = 1.23 (per KCSWDM Figure 4.2.1.K for 90° Bend at a Manhole, no Special Shaping)
Entrance Loss Coef., Ke = 0.5 ( per KCSWDM Table 4.3.1.B for Square-Cut End Concrete Pipe)
g = 32.2 ft/s2 - acceleration due to gravity
Layout Pipe Sytem Design Backwater Calculation
Structure Number
Design Flow,
Q Length Pipe Size "n" Value Slope Outlet El Inlet Elev Q/(AD^0.5)*
Inlet
Controlled
Condition Q2Bc/(gAc3)Critical Depth
Critical
Velocity Barrel Area
Barrel
Velocity
Barrel Vel
Head
(cfs)(ft)(in)(%)(ft)(ft)(ft)(fps)(sf)(fps)(ft)
1 2 3 4 5 6 7 8 9 10 14 15 16 17 18 19
0
0
0
CB #14 0.20 21.97 12 0.012 2.00% 347.29 347.73 0.253 Unsubmerged 1.00 0.18 2.02 0.785 0.253 0.0010
CB #12A 0.20 18.58 8 0.012 2.03% 345.98 346.36 0.692 Unsubmerged 0.99 0.20 2.17 0.349 0.565 0.0050
CB #13 0.20 82.02 12 0.012 2.00% 345.65 347.29 0.253 Unsubmerged 1.00 0.18 2.02 0.785 0.253 0.0010
CB #12 0.49 73.73 12 0.012 1.99% 344.18 345.65 0.623 Unsubmerged 1.00 0.29 2.59 0.785 0.623 0.0060
CB #11 0.49 41.10 12 0.012 2.00% 343.36 344.18 0.623 Unsubmerged 1.00 0.29 2.59 0.785 0.623 0.0060
CB #9A 0.36 34.66 8 0.012 2.62% 342.91 343.82 1.262 Unsubmerged 1.01 0.28 2.61 0.349 1.031 0.0165
CB #10 0.68 38.84 12 0.012 2.01% 342.58 343.36 0.868 Unsubmerged 1.00 0.34 2.85 0.785 0.868 0.0117
CB #9 1.04 49.36 12 0.012 2.01% 341.59 342.58 1.326 Unsubmerged 1.00 0.43 3.24 0.785 1.326 0.0273
CB #8 1.27 26.02 12 0.012 2.00% 341.07 341.59 1.619 Unsubmerged 1.00 0.48 3.45 0.785 1.619 0.0407
CB #7 1.27 61.76 12 0.012 2.01% 339.83 341.07 1.619 Unsubmerged 1.00 0.48 3.45 0.785 1.619 0.0407
CB #6 1.60 15.69 12 0.012 1.98% 339.52 339.83 2.041 Unsubmerged 1.00 0.54 3.73 0.785 2.041 0.0647
CB #5 1.74 9.05 12 0.012 1.99% 339.34 339.52 2.215 Unsubmerged 1.00 0.56 3.84 0.785 2.215 0.0762
CB #4 1.81 63.62 12 0.012 2.00% 338.07 339.34 2.302 Unsubmerged 1.00 0.57 3.89 0.785 2.302 0.0823
CB #3 2.33 56.91 12 0.012 5.55% 334.91 338.07 2.971 Unsubmerged 1.00 0.65 4.29 0.785 2.971 0.1371
CB #2 2.53 11.76 12 0.012 4.85% 334.34 334.91 3.216 Unsubmerged 1.00 0.68 4.44 0.785 3.216 0.1606
CB #1 2.53 29.00 12 0.012 1.00% 334.05 334.34 3.216 Unsubmerged 1.00 0.68 4.44 0.785 3.216 0.1606
BLOCK D
CB #18A 0.16 34.86 8 0.012 3.00% 351.38 352.43 0.557 Unsubmerged 0.99 0.18 2.04 0.349 0.455 0.0032
CB #19 0.15 109.74 12 0.012 1.00% 351.05 352.15 0.195 Unsubmerged 1.00 0.16 1.89 0.785 0.195 0.0006
CB #18 0.63 99.28 12 0.012 1.00% 350.06 351.05 0.796 Unsubmerged 1.00 0.33 2.78 0.785 0.796 0.0098
CB #17 0.85 60.00 12 0.012 1.00% 349.46 350.06 1.078 Unsubmerged 1.00 0.39 3.04 0.785 1.078 0.0181
CB #16 1.21 12.15 12 0.012 0.99% 349.34 349.46 1.542 Unsubmerged 1.00 0.46 3.39 0.785 1.542 0.0369
CB #15 1.21 43.00 12 0.012 1.12% 348.86 349.34 1.542 Unsubmerged 1.00 0.46 3.39 0.785 1.542 0.0369
Solera Townhomes Conveyance Spreadsheet | 100yr BW 15 of 29 5/23/2025 | 10:35 AM
KPFF Consulting Engineers
SOLERA TOWNHOMES
KPFF Consulting Engineers
MAY, 2025
Layout
Structure Number
1
0
0
0
CB #14
CB #12A
CB #13
CB #12
CB #11
CB #9A
CB #10
CB #9
CB #8
CB #7
CB #6
CB #5
CB #4
CB #3
CB #2
CB #1
BLOCK D
CB #18A
CB #19
CB #18
CB #17
CB #16
CB #15
Drainage Calculations - Backwater Analysis for the 100-year Storm Event
ASSUMPTIONS AND CONSTANTS
Manning's n = 0.012 (per KCSWDM Table 4.2.1 D for PVC Pipe - Backwater Flow Anaysis)
Inlet Control Analysis = Assumed concrete pipe, square edge with headwall
*If Q/(AD^0.5)<=3.5, unsubmerged inlet conditions. If Q/(AD^0.5)>=4.0, submerged conditions (See KCSWDM pg.4-37)
Unsubmerged : Submerged :
K = 0.0098 c = 0.0398
M = 2 Y = 0.67 (per KCSWDM Table 4.3.1.A for Circular Concrete Pipe - Square Edge with Headwall Equation Form 1)
Bend Head Loss Coeff., Kb = 1.23 (per KCSWDM Figure 4.2.1.K for 90° Bend at a Manhole, no Special Shaping)(per KCSWDM Table 4.3.1.A for Circular Concrete Pipe - Square Edge with Headwall Equation Form 1)
Entrance Loss Coef., Ke = 0.5 ( per KCSWDM Table 4.3.1.B for Square-Cut End Concrete Pipe)
g = 32.2 ft/s2 - acceleration due to gravity
Checks
TW Elev
Hydraulic
Radius Friction Loss
Entrance HGL
Elev
Entrance
Head Loss
Exit Head
Loss
Outlet
Control Elev
Inlet Control
Elev*
Inlet or Outlet
Controlled?
Approach
Velocity Head
Bend Head
Loss
Junction
Loss Coeff.,
Kj
Junction
Head Loss HW Elev CB Rim Elev
Overtopping
Check
Clearance
btwn Rim and
HGL
(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft)
20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
347.53 0.250 0.0006 347.53 0.0005 0.0010 347.53 347.97 Inlet 0.000 0.0000 0.00 0.0000 347.97 351.81 OK 3.84
346.04 0.167 0.0042 346.05 0.0025 0.0050 346.05 346.63 Inlet 0.000 0.0000 0.00 0.0000 346.63 350.17 OK 3.54
346.04 0.250 0.0022 346.04 0.0005 0.0010 346.05 347.53 Inlet 0.001 0.0012 0.00 0.0000 347.53 351.37 OK 3.84
344.56 0.250 0.0117 344.57 0.0030 0.0060 344.58 346.04 Inlet 0.005 0.0061 0.55 0.0027 346.04 349.73 OK 3.69
343.83 0.250 0.0065 343.84 0.0030 0.0060 343.84 344.57 Inlet 0.006 0.0000 0.00 0.0000 344.56 348.26 OK 3.70
343.19 0.167 0.0259 343.21 0.0082 0.0165 343.24 344.21 Inlet 0.000 0.0000 0.00 0.0000 344.21 348.15 OK 3.94
343.19 0.250 0.0120 343.20 0.0058 0.0117 343.22 343.83 Inlet 0.006 0.0074 0.00 0.0000 343.83 347.43 OK 3.60
342.24 0.250 0.0356 342.27 0.0137 0.0273 342.32 343.18 Inlet 0.016 0.0203 0.35 0.0058 343.19 346.77 OK 3.58
341.71 0.250 0.0280 341.73 0.0203 0.0407 341.79 342.27 Inlet 0.027 0.0000 0.00 0.0000 342.24 346.03 OK 3.79
340.57 0.250 0.0664 340.64 0.0203 0.0407 340.70 341.75 Inlet 0.041 0.0000 0.00 0.0000 341.71 345.64 OK 3.93
340.28 0.250 0.0268 340.31 0.0323 0.0647 340.41 340.61 Inlet 0.041 0.0000 0.00 0.0000 340.57 344.71 OK 4.14
340.11 0.250 0.0182 340.13 0.0381 0.0762 340.25 340.35 Inlet 0.065 0.0000 0.00 0.0000 340.28 344.47 OK 4.19
338.99 0.250 0.1382 339.12 0.0411 0.0823 339.25 340.19 Inlet 0.076 0.0000 0.00 0.0000 340.11 344.34 OK 4.23
335.84 0.250 0.2060 336.04 0.0685 0.1371 336.25 339.07 Inlet 0.082 0.0000 0.00 0.0000 338.99 343.34 OK 4.35
335.26 0.250 0.0499 335.31 0.0803 0.1606 335.55 335.97 Inlet 0.137 0.0000 0.00 0.0000 335.84 342.41 OK 6.57
0.00 0.250 0.1230 0.12 0.0803 0.1606 0.36 335.42 Inlet 0.161 0.0000 0.00 0.0000 335.26 342.50 OK 7.24
351.50 0.167 0.0051 351.51 0.0016 0.0032 351.51 352.67 Inlet 0.000 0.0000 0.00 0.0000 352.67 356.57 OK 3.90
351.50 0.250 0.0017 351.50 0.0003 0.0006 351.51 352.36 Inlet 0.000 0.0000 0.00 0.0000 352.36 357.21 OK 4.85
350.58 0.250 0.0258 350.61 0.0049 0.0098 350.63 351.50 Inlet 0.003 0.0040 0.57 0.0018 351.50 357.09 OK 5.59
350.10 0.250 0.0286 350.13 0.0090 0.0181 350.16 350.59 Inlet 0.010 0.0000 0.00 0.0000 350.58 354.79 OK 4.21
349.96 0.250 0.0118 349.98 0.0184 0.0369 350.03 350.12 Inlet 0.018 0.0000 0.00 0.0000 350.10 353.28 OK 3.18
0.00 0.250 0.0419 0.04 0.0184 0.0369 0.10 350.00 Inlet 0.037 0.0000 0.00 0.0000 349.96 352.82 OK 2.86
Solera Townhomes Conveyance Spreadsheet | 100yr BW 16 of 29 5/23/2025 | 10:35 AM
KPFF Consulting Engineers
SOLERA TOWNHOMES
KPFF Consulting Engineers
MAY, 2025
Layout
Structure Number
1
0
0
0
CB #14
CB #12A
CB #13
CB #12
CB #11
CB #9A
CB #10
CB #9
CB #8
CB #7
CB #6
CB #5
CB #4
CB #3
CB #2
CB #1
BLOCK D
CB #18A
CB #19
CB #18
CB #17
CB #16
CB #15
Notes
Comments
50
Solera Townhomes Conveyance Spreadsheet | 100yr BW 17 of 29 5/23/2025 | 10:35 AM
Solera Phase 2: Block C and Block D – New Home Co.
Appendix G
Appendix G
Erosion Control Plan and Details
Solera Phase 2: Block C and Block D – New Home Co.
Appendix H
Appendix H
SWPPP
Solera Townhomes – New Home Co. Page 1
Construction Stormwater General Permit (CSWGP)
Stormwater Pollution Prevention Plan
(SWPPP)
for
Solera Townhomes
Prepared for:
Washington State Department of Ecology
Northwest Regional Office
Permittee / Owner Developer Operator / Contractor
Solera, LLC
10900 NE 8th Street, Suite 1200
Bellevue, WA 98004
New Home Co.
1700 NW Gilman Blvd, Suite 220
Issaquah, WA 98027
TBD
Project Site Location:
2842 NE Sunset Boulevard, Renton, WA 98056
Certified Erosion and Sediment Control Lead (CESCL)
Name Organization Contact Phone Number
TBD TBD TBD
SWPPP Prepared By
Name Organization Contact Phone Number
Danial Khan, EIT KPFF 206-622-5822
SWPPP Preparation Date
November 2024
Project Construction Dates
Activity / Phase Start Date End Date
Construction Start June 2025 September 2026
Solera Townhomes – New Home Co. Page 2
Table of Contents
List of Acronyms and Abbreviations ............................................................................................................. 4
Project Information (1.0) .............................................................................................................................. 5
Existing Conditions (1.1) ........................................................................................................................... 5
Proposed Construction Activities (1.2) ..................................................................................................... 6
Construction Stormwater Best Management Practices (BMPs) (2.0)........................................................... 7
The 13 Elements (2.1) ............................................................................................................................... 7
Element 1: Preserve Vegetation / Mark Clearing Limits (2.1.1) ........................................................... 7
Element 2: Establish Construction Access (2.1.2) ................................................................................. 8
Element 3: Control Flow Rates (2.1.3) .................................................................................................. 9
Element 4: Install Sediment Controls (2.1.4) ...................................................................................... 10
Element 5: Stabilize Soils (2.1.5) ......................................................................................................... 11
Element 6: Protect Slopes (2.1.6)........................................................................................................ 12
Element 7: Protect Drain Inlets (2.1.7) ............................................................................................... 13
Element 8: Stabilize Channels and Outlets (2.1.8) .............................................................................. 14
Element 9: Control Pollutants (2.1.9) ................................................................................................. 15
Element 10: Control Dewatering (2.1.10) ........................................................................................... 18
Element 11: Maintain BMPs (2.1.11) .................................................................................................. 19
Element 12: Manage the Project (2.1.12) ........................................................................................... 20
Element 13: Protect Low Impact Development (LID) BMPs (2.1.13) .................................................. 23
Pollution Prevention Team (3.0) ................................................................................................................. 23
Monitoring and Sampling Requirements (4.0) ........................................................................................... 24
Site Inspection (4.1) ................................................................................................................................ 24
Stormwater Quality Sampling (4.2) ........................................................................................................ 25
Turbidity Sampling (4.2.1) ................................................................................................................... 25
pH Sampling (4.2.2) ............................................................................................................................. 27
Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies (5.0) ........................................ 28
303(d) Listed Waterbodies (5.1) ............................................................................................................. 28
N/A .......................................................................................................................................................... 28
TMDL Waterbodies (5.2) ......................................................................................................................... 28
Reporting and Record Keeping (6.0) ........................................................................................................... 29
Record Keeping (6.1) ............................................................................................................................... 29
Solera Townhomes – New Home Co. Page 3
Site Log Book (6.1.1) ........................................................................................................................... 29
Records Retention (6.1.2) ................................................................................................................... 29
Updating the SWPPP (6.1.3) ............................................................................................................... 29
Reporting (6.2) ........................................................................................................................................ 30
Discharge Monitoring Reports (6.2.1) ................................................................................................. 30
Notification of Noncompliance (6.2.2)................................................................................................ 30
Appendix/Glossary .............................................................................................................................. 32
List of Tables
Table 1 - West of the Cascade Mountains Crest ......................................................................................... 11
Table 2 – Pollutants ..................................................................................................................................... 15
Table 3 – pH-Modifying Sources ................................................................................................................. 16
Table 4 – Dewatering BMPs ........................................................................................................................ 18
Table 5 – Management ............................................................................................................................... 20
Table 6 – BMP Implementation Schedule ................................................................................................... 21
Table 7 – Team Information ........................................................................................................................ 23
Table 8 – Turbidity Sampling Method ......................................................................................................... 25
Table 9 – pH Sampling Method ................................................................................................................... 27
List of Appendices
A. Site Plan
1. TESC Plans
2. TESC Details
B. BMP Detail
C. Site Inspection Form
D. Construction Stormwater General Permit (CSWGP)
E. 303(d) List Waterbodies / TMDL Waterbodies Information
F. Engineering Calculations
1. Sediment Tank Sizing
Solera Townhomes – New Home Co. Page 4
List of Acronyms and Abbreviations
Acronym / Abbreviation Explanation
303(d) Section of the Clean Water Act pertaining to Impaired Waterbodies
BFO Bellingham Field Office of the Department of Ecology
BMP(s) Best Management Practice(s)
CESCL Certified Erosion and Sediment Control Lead
CO2 Carbon Dioxide
CRO Central Regional Office of the Department of Ecology
CSWGP Construction Stormwater General Permit
CWA Clean Water Act
DMR Discharge Monitoring Report
DO Dissolved Oxygen
Ecology Washington State Department of Ecology
EPA United States Environmental Protection Agency
ERO Eastern Regional Office of the Department of Ecology
ERTS Environmental Report Tracking System
ESC Erosion and Sediment Control
GULD General Use Level Designation
NPDES National Pollutant Discharge Elimination System
NTU Nephelometric Turbidity Units
NWRO Northwest Regional Office of the Department of Ecology
pH Power of Hydrogen
RCW Revised Code of Washington
SPCC Spill Prevention, Control, and Countermeasure
su Standard Units
SWMMEW Stormwater Management Manual for Eastern Washington
SWMMWW Stormwater Management Manual for Western Washington
SWPPP Stormwater Pollution Prevention Plan
TESC Temporary Erosion and Sediment Control
SWRO Southwest Regional Office of the Department of Ecology
TMDL Total Maximum Daily Load
VFO Vancouver Field Office of the Department of Ecology
WAC Washington Administrative Code
WSDOT Washington Department of Transportation
WWHM Western Washington Hydrology Model
Solera Townhomes – New Home Co. Page 5
Project Information (1.0)
Project/Site Name: Solera Townhomes
Street/Location: 2842 Northeast Sunset Boulevard
City: Renton State: WA Zip code: 98056
Subdivision: N/A
Receiving waterbody: Lake Washington
Existing Conditions (1.1)
Total acreage (including support activities such as off-site equipment staging yards, material
storage areas, and borrow areas).
Total acreage: 3.85 Acres
Disturbed acreage: 3.85 Acres
Existing structures: The previous existing structures have already been demolished,
and the site is stabilized. No existing structures are present on-site.
Landscape topography:
The existing site is located within two drainage basins. The site
generally slopes 2-5% to the southwest or 2-5% to the north. There
is approximately 20 feet of vertical elevation change within the
project limits.
Drainage patterns: Stormwater runoff generally sheet flows towards existing
conveyance systems in Jefferson Ave NE, NE 10th St, NE 11th St,
and Harrington Ave NE.
Existing Vegetation: The previous parking lot and structures on site have been
demolished under a separate permit and the site is stabilized with
temporary gravel and grass.
Critical Areas: The project was preliminary mapped for isolated sensitive slopes up
to approximately 25% per RMC 4-3-050G.2.5.a. These isolated
areas evaluated by the project geotechnical engineer and
determined to be the result of previous site construction, rather than
a naturally occurring slope.
List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the
receiving waterbody: N/a
Solera Townhomes – New Home Co. Page 6
Proposed Construction Activities (1.2)
Description of site development:
The project proposes a total of 90 townhome units, 61 on Block C and 29 on Block D along with
associated alleys, landscape areas, open space, stormwater mitigation facilities, and requisite
utilities.
Description of construction activities:
Construction activities for the entire site will consist of site preparation, TESC installation, grade
and fill, storm drainage facilities, flow control BMPs, water quality facilities, and asphalt and
concrete paving. Construction stormwater will be detained onsite prior to discharge offsite; see
the Solera Townhomes technical information report (TIR) and TESC plan sheets (C4.00-C4.11)
for TESC design and details.
Description of site drainage including flow from and onto adjacent properties. Must be consistent
with Site Map in Appendix A:
Upon project completion, onsite roof areas on Block C will drain to infiltrating bioretention
facilities to the maximum extent feasible. Roof runoff that is not able to be infiltrated will be sent
to the storm system in Jefferson Ave NE. Roof runoff from Block D will be sent to infiltrating
bioretention facilities to the maximum extent feasible. Roof runoff that is not able to be infiltrated
will be sent to the storm system in Harrington Pl NE. Any surface water not captured due to
infeasibility is considered bypass and will ultimately outfall to existing systems surrounding the
site.
Description of final stabilization (example: extent of revegetation, paving, landscaping):
The site will predominately consist of building structures, asphalt roadway, and concrete
sidewalks. Available site will consist of bioretention and landscaped areas to meet open space
requirements.
Contaminated Site Information:
Proposed activities regarding contaminated soils or groundwater (example: on-site treatment
system, authorized sanitary sewer discharge):
Contamination on-site was removed under permit number B21-001703.
Solera Townhomes – New Home Co. Page 7
Construction Stormwater Best Management Practices (BMPs) (2.0)
The SWPPP is a living document reflecting current conditions and changes throughout the life
of the project. These changes may be informal (i.e., hand-written notes and deletions). Update
the SWPPP when the CESCL has noted a deficiency in BMPs or deviation from original design.
The 13 Elements (2.1)
Alternatives for all listed BMPs are included in Appendix B as a quick reference tool for the
onsite inspector in the event the BMP(s) listed below are deemed ineffective or inappropriate
during construction to satisfy the requirements set forth in this document. To avoid potential
erosion and sediment control issues that may cause a violation(s) of the King County and
Ecology requirements, the Certified Erosion and Sediment Control Lead will promptly initiate the
implementation of one or more of the alternative BMPs listed in Appendix B after the first sign
that existing BMPs are ineffective or failing.
Element 1: Preserve Vegetation / Mark Clearing Limits (2.1.1)
To protect adjacent properties and to reduce the area of soil exposed to construction, the limits
of construction shall be clearly marked before and during land-disturbing activities begin. Trees
that are to be preserved, as well as all sensitive areas and their buffers, shall be clearly
delineated, both in the field and on the plans. The BMPs relevant to marking and clearing limits
that shall be applied for this project include:
List and describe BMPs: High visibility fence (C103) / metal fence, tree protection fence
High-visibility metal fencing shall be placed around the perimeter of the site, abutting ROW
limits and easements to prevent intentional or unintentional access. High visibility plastic fence
shall be places at locations indicating steep slope conditions for staff and public safety. A secure
gate shall be located at the construction entrances to restrict access to construction areas.
Alternate BMPs for marking the clearing limits are included in Appendix B as a quick reference
tool for the onsite inspector in the event the BMP(s) listed above are deemed ineffective or
inappropriate during construction to satisfy the requirements set forth in this document. To
avoid potential erosion and sediment control issues that may cause a violation(s) of the King
County and Ecology requirements, the Certified Erosion and Sediment Control Lead will
promptly initiate the implementation of one or more of the alternative BMPs listed in Appendix B
after the first sign that existing BMPs are ineffective or failing.
Installation Schedules: Installation prior to construction.
Inspection and Maintenance plan: Construction fencing shall be inspected daily to ensure it is
in good condition and in correct location.
Responsible Staff: CESCL
Solera Townhomes – New Home Co. Page 8
Element 2: Establish Construction Access (2.1.2)
Construction access or activities occurring on unpaved areas shall be minimized, yet where
necessary, access points shall be stabilized to minimize the tracking of sediment onto public
roads, and wheel washing, street sweeping, and street cleaning shall be employed if necessary
to prevent sediment from entering state waters. All wash wastewater shall be controlled on site.
The specific BMPs related to establishing construction access that shall be used on this project
include:
List and describe BMPs: Stabilized Construction Entrance (C105), Wheel Wash (C106)
The stabilized construction accesses shall be installed at Jefferson Ave NE and NE 11th St. The
entrance shall have a minimum length of 100 feet and width of 15 feet.
Installation Schedules: Installation prior to construction.
Inspection and Maintenance plan: Construction access elements shall be inspected daily to
ensure it is in good condition and effectively preventing sediment from being tracked into the
roadway.
Responsible Staff: CESCL
Solera Townhomes – New Home Co. Page 9
Element 3: Control Flow Rates (2.1.3)
Will you construct stormwater retention and/or detention facilities?
Settlement tanks will be provided during the construction of Block C and D. Interceptor swales
and rock check dams will route all construction stormwater to the settlement tanks to hold the
water until it is released into existing storm drainage systems surrounding the site.
Will you use permanent infiltration ponds or other low impact development (example: rain
gardens, bio-retention, porous pavement) to control flow during construction?
Infiltrating bioretention planters will be utilized in the permanent condition.
List and describe BMPs: Check Dams (C207), Temporary Interceptor Swale/Dikes (C200),
Wattles (C235)
Installation Schedules: All on-site construction runoff will be routed through temporary
culverts and swales before being released into the settlement tanks where it will then be
pumped into the existing systems surrounding the site. The settlement tanks will hold
stormwater until the onsite stormwater conveyance system is complete. Wattles and check
dams shall be installed as construction progresses, indicated on the construction TESC plans.
The settlement tank was designed per the City of Renton Surface Water Design Manual and
King County Sedimentation Tank Standards. The stormwater leaving the settlement system will
be tested prior to discharge.
Inspection and Maintenance plan: Check dams and wattles shall be inspected daily to ensure
they are in good condition and effectively reducing sediment from leaving the site. The
settlement tanks shall be inspected daily, and consistently during storm events, to ensure
proper function.
Responsible Staff: CESCL
The project site is located west of the Cascade Mountain Crest. As such, the project must
comply with Core Requirement 3 (Ecology 2019).
In general, discharge rates of stormwater from the site will be controlled where increases in
impervious area or soil compaction during construction could lead to downstream erosion, or
where necessary to meet local agency stormwater discharge requirements (e.g. discharge to
combined sewer systems).
Solera Townhomes – New Home Co. Page 10
Element 4: Install Sediment Controls (2.1.4)
All stormwater runoff from disturbed areas shall pass through an appropriate sediment removal
BMP before leaving the construction site and entering the existing stormwater conveyance
surrounding the site or sheet flowing as bypass runoff. The specific BMPs to be
used for controlling sediment on this project include:
List and describe BMPs: Silt Fence (BMP C233), Dust Control (C140), Storm Drain Inlet
Protection (BMP C220)
Silt fencing shall be installed around the limits of disturbance prior to grading. Storm drain inlet
protection shall be installed in all constructed catch basins during construction to prevent
sediment laden runoff from the construction site from entering the stormwater system.
Installation Schedules: Installation prior to construction.
Inspection and Maintenance plan: Sediment control elements shall be inspected daily to
ensure they are in good condition and effectively preventing sediment from leaving the site.
Responsible Staff: CESCL
In addition, sediment will be removed from paved areas in and adjacent to construction work
areas manually or using mechanical sweepers, as needed, to minimize tracking of sediments on
vehicle tires away from the site and to minimize washoff of sediments from adjacent streets in
runoff.
Solera Townhomes – New Home Co. Page 11
Element 5: Stabilize Soils (2.1.5)
Table 1 - West of the Cascade Mountains Crest
Season Dates Number of Days Soils Can
be Left Exposed
During the Dry Season May 1 – September 30 7 days
During the Wet Season October 1 – April 30 2 days
Soils must be stabilized at the end of the shift before a holiday or weekend if needed based on
the weather forecast.
Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent
erosion throughout the life of the project.
Anticipated project dates: Start date: April 2025 End date: September 2026
Will you construct during the wet season?
Yes No
List and describe BMPs: Plastic Covering (BMP C123), Surface Roughening (BMP C130),
Dust Control (BMP C140), Nets and Blankets (BMP C122)
Installation Schedules: Soil stabilizing elements shall be installed as soon as practical
following the completion of mass grading and fine grading, and shall be maintained and
adjusted as needed.
Inspection and Maintenance plan: Soil stabilizing elements shall be inspected daily to ensure
they are in good condition.
Responsible Staff: CESCL
In general, cut and fill slopes will be stabilized as soon as possible and soil stockpiles will be
temporarily covered with plastic sheeting. All stockpiled soils shall be stabilized from erosion,
protected with sediment trapping measures, and where possible, be located away from storm
drain inlets, waterways, and drainage channels.
Solera Townhomes – New Home Co. Page 12
Element 6: Protect Slopes (2.1.6)
Will steep slopes be present at the site during construction?
Yes No
All cut and fill slopes shall be designed, constructed, and protected in a manner that minimizes
erosion while aligning with finished site topography. The following specific BMPs shall be used
to protect slopes for this project:
List and describe BMPs: Interceptor Dike and Swale (BMP C200). Check Dams (C207).
Installation Schedules: Slope protection elements shall be installed as practical before
and after mass grading and shall be maintained and adjusted as needed.
Inspection and Maintenance plan: Slope protection elements shall be inspected daily to
ensure they are in good condition and effectively preventing slope erosion.
Responsible Staff: CESCL
Temporary seeding will be implemented along any disturbed areas of the site prior to
construction to ensure stabilization of the soil. Permanent seeding will be implemented at the
end of construction along the same disturbed site areas.
Rock check dams will be used along the swale to reduce the runoff flow going to the settlement
tanks.
Interceptor swales will be used where runoff from disturbed slopes must be conveyed to the
settlement tanks. Interceptors will reduce the velocity of the runoff flowing across the site.
Solera Townhomes – New Home Co. Page 13
Element 7: Protect Drain Inlets (2.1.7)
List and describe BMPs: Storm Drain Inlet Protection (BMP C220)
All storm drain inlets and culverts made operable during construction shall be protected to
prevent unfiltered or untreated water from entering the drainage conveyance system. However,
the first priority is to keep all access roads clean of sediment and keep street wash water
separate from entering storm drains until treatment can be provided.
Inlet protection devices shall be cleaned (or removed and replaced) when sediment has filled
the device by one-third (1/3) or as specified by the manufacturer. Contractor shall provide
protection for inlets and catch basins onsite, and including elements within 500 feet downstream
of the project site. Inlets shall be inspected weekly at a minimum and daily during storm events.
Installation Schedules: Storm drain inlet protection shall be installed at the beginning of
construction and will be maintained and adjusted as needed.
Inspection and Maintenance plan: Storm drain inlet protection shall be inspected daily to
ensure it is in good condition and cleaned or replaced as needed.
Responsible Staff: CESCL
Solera Townhomes – New Home Co. Page 14
Element 8: Stabilize Channels and Outlets (2.1.8)
Provide stabilization, including armoring material, adequate to prevent erosion of outlets,
adjacent stream banks, slopes, and downstream reaches, will be installed at the outlets of all
conveyance systems.
List and describe BMPs: N/A
No BMPs are planned to be implemented for this element. Stormwater from the project site will
be discharged to a piped conveyance system and no erosion of the outlet is anticipated.
Installation Schedules: N/A
Inspection and Maintenance plan: N/A
Responsible Staff: N/A
The project site is located west of the Cascade Mountain Crest. As such, all temporary on-site
conveyance channels shall be designed, constructed, and stabilized to prevent erosion from the
expected peak 10-minute velocity of flow from a Type 1A, 10-year, 24-hour recurrence interval
storm for the developed condition. Alternatively, the 10-year, 1-hour peak flow rate indicated by
an approved continuous runoff simulation model, increased by a factor of 1.6, shall be used.
Solera Townhomes – New Home Co. Page 15
Element 9: Control Pollutants (2.1.9)
The following pollutants are anticipated to be present on-site:
Table 2 – Pollutants
Pollutant (and source, if applicable)
Diesel fuel – heavy equipment onsite
Hydraulic oil – heavy equipment onsite
General demolition debris
Concrete and concrete slurry – concrete trucks onsite
All pollutants, including waste materials and demolition debris, that occur onsite shall be
handled and disposed of in a manner that does not cause contamination of stormwater. Good
housekeeping and preventative measures shall be taken to ensure that the site will be kept
clean, well-organized, and free of debris. If required, BMPs to be implemented to control specific
sources of pollution are discussed below.
List and describe BMPs: Dust Control (BMP C140), Concrete Handling (BMP C151),
Material Delivery, Storage and Containment (BMP (C153), Storm Drain Inlet Protection (BMP
C220)
Installation Schedules: Pollutant control elements shall be installed as needed and shall
be maintained and adjusted as needed.
Inspection and Maintenance plan: Pollutant control elements shall be inspected and
maintained, as necessary.
Responsible Staff: CESCL
Will maintenance, fueling, and/or repair of heavy equipment and vehicles occur on-site?
Yes No
List and describe BMPs: Material Delivery, Storage and Containment BMP (C153)
Installation Schedules: Pollution control elements shall be installed as needed and shall
be maintained and adjusted as needed.
Inspection and Maintenance plan: Pollution control elements shall be inspected and
maintained, as necessary.
Responsible Staff: CESCL
Will wheel wash or tire bath system BMPs be used during construction?
Yes No
Solera Townhomes – New Home Co. Page 16
List and describe BMPs: Discharge wheel wash or tire bath wastewater to a separate
onsite treatment system that prevents discharge to surface water, such as closed-loop
recirculation or upland land application, or to the sanitary sewer. For discharges to the sanitary
sewer, permits must be obtained from the wastewater management agency presiding over the
project site.
Wheel wash or tire bath wastewater should not include wastewater from concrete washout
areas.
Installation Schedules: Wheel wash systems shall be installed beginning Grade and Fill
construction. Wheel wash systems shall be onsite daily during construction, and may be used
multiple times a day at contractor discretion.
Inspection and Maintenance plan: Wheel wash system shall be inspected and maintained as
needed and after use.
Responsible Staff: CESCL
Will pH-modifying sources be present on-site?
Yes No
Table 3 – pH-Modifying Sources
None
Bulk cement
Cement kiln dust
Fly ash
Other cementitious materials
New concrete washing or curing waters
Waste streams generated from concrete grinding and sawing
Exposed aggregate processes
Dewatering concrete vaults
Y Concrete pumping and mixer washout waters
Recycled concrete
Other (i.e., calcium lignosulfate) [please describe]
List and describe BMPs: Concrete Washout Area (BMP C154)
All concrete washout waters shall be vacuumed while the work is actively occurring to prevent
migration offsite, and shall not remain on existing asphalt or concrete surfaces. The washout
waters shall be disposed of in a manner that does not violate surface water or groundwater
quality standards.
Solera Townhomes – New Home Co. Page 17
Installation Schedules: BMPs relating to pH-modifying sources shall be implemented, as
necessary.
Inspection and Maintenance plan: BMPs relating to pH-modifying sources shall be inspected
and maintained, as necessary.
Responsible Staff: CESCL
Concrete trucks must not be washed out onto the ground, or into storm drains, open ditches,
streets, or streams. Excess concrete must not be dumped on-site, except in designated
concrete washout areas with appropriate BMPs installed.
Demolition:
· All structure demolition has already occurred, and the site is stabilized. Dust released
from any further demolition will be controlled using Dust Control measures (BMP C140).
· Storm drain inlets vulnerable to stormwater discharge carrying dust, soil, or debris will be
protected using Storm Drain Inlet Protection (BMP C220 as described above for Element
7).
· Process water and slurry resulting from sawcutting and surfacing operations will be
prevented from entering the waters of the State by implementing Sawcutting and
Surfacing Pollution Prevention measures (BMP C152).
Concrete and grout:
· Process water and slurry resulting from concrete work will be prevented from entering
the waters of the State by implementing Concrete Handling measures (BMP C151).
Solera Townhomes – New Home Co. Page 18
Element 10: Control Dewatering (2.1.10)
All trench de-watering water shall be discharged into a controlled conveyance system before
discharge to the sediment pond. Clean, non-turbid de-watering water, such as well-point ground
water, shall be discharged to systems tributary to, or directly into surface waters of the State, as
specified in Element #8, provided the de-watering flow does not cause erosion or flooding of
receiving waters. Clean de-watering water shall not be routed through the sediment pond.
Table 4 – Dewatering BMPs
Infiltration
Transport off-site in a vehicle (vacuum truck for legal disposal)
Ecology-approved on-site chemical treatment or other suitable treatment technologies
Sanitary or combined sewer discharge with local sewer district approval (last resort)
Use of sedimentation bag with discharge to ditch or swale (small volumes of localized
dewatering)
List and describe BMPs: No BMPs are planned for dewatering.
Installation Schedules: N/A
Inspection and Maintenance plan: N/A
Responsible Staff: N/A
Solera Townhomes – New Home Co. Page 19
Element 11: Maintain BMPs (2.1.11)
All temporary and permanent Erosion and Sediment Control (ESC) BMPs shall be maintained
and repaired as needed to ensure the continued performance of their intended function.
Maintenance and repair shall be conducted in accordance with each BMP specification (see
Volume II of the SWMMWW or Chapter 7 of the SWMMEW).
Visual monitoring of all BMPs installed at the site will be conducted at least once every calendar
week and within 24 hours of any stormwater or non-stormwater discharge from the site. If the
site becomes inactive and is temporarily stabilized, the inspection frequency may be reduced to
once every calendar month.
All temporary ESC BMPs shall be removed within 30 days after final site stabilization is
achieved or after the temporary BMPs are no longer needed.
Trapped sediment shall be stabilized on-site or removed. Disturbed soil resulting from removal
of either BMPs or vegetation shall be permanently stabilized.
Additionally, protection must be provided for all BMPs installed for the permanent control of
stormwater from sediment and compaction. BMPs that are to remain in place following
completion of construction shall be examined and restored to full operating condition. If
sediment enters these BMPs during construction, the sediment shall be removed, and the
facility shall be returned to conditions specified in the construction documents.
Solera Townhomes – New Home Co. Page 20
Element 12: Manage the Project (2.1.12)
The project will be managed based on the following principles:
· Projects will be phased to the maximum extent practicable and seasonal work limitations
will be considered.
· Inspection and monitoring:
o Inspection, maintenance, and repair of all BMPs will occur as needed to ensure
performance of their intended function.
o Site inspections and monitoring will be conducted in accordance with Special
Condition S4 of the CSWGP. Sampling locations are indicated on the Site Map.
Sampling station(s) are located in accordance with applicable requirements of
the CSWGP.
· Maintain an updated SWPPP.
o The SWPPP will be updated, maintained, and implemented in accordance with
Special Conditions S3, S4, and S9 of the CSWGP.
As site work progresses the SWPPP will be modified routinely to reflect changing site
conditions. The SWPPP will be reviewed monthly to ensure the content is current.
Table 5 – Management
Y Design the project to fit the existing topography, soils, and drainage patterns
Y Emphasize erosion control rather than sediment control
Y Minimize the extent and duration of the area exposed
Y Keep runoff velocities low
Y Retain sediment on-site
Y Thoroughly monitor site and maintain all ESC measures
Y Schedule major earthwork during the dry season
Other (please describe)
Solera Townhomes – New Home Co. Page 21
Table 6 – BMP Implementation Schedule
Phase of Construction
Project
Stormwater BMPs Date Wet/Dry
Season
[Insert construction
activity]
[Insert BMP] [MM/DD/YYYY] [Insert
Season]
Solera Townhomes – New Home Co. Page 22
Phase of Construction
Project
Stormwater BMPs Date Wet/Dry
Season
[Insert construction
activity]
[Insert BMP] [MM/DD/YYYY] [Insert
Season]
Solera Townhomes – New Home Co. Page 23
Element 13: Protect Low Impact Development (LID) BMPs (2.1.13)
No LID BMPs are currently proposed for the construction phase of this project. Existing LID
BMP’s surrounding the site will be protected using straw wattle and construction fencing.
Pollution Prevention Team (3.0)
Table 7 – Team Information
Title Name(s) Phone Number
Certified Erosion and
Sediment Control Lead
(CESCL)
TBD TBD
Resident Engineer Michelle Freeman 206-622-5822
Emergency Ecology
Contact
Kendra Hendersen 360-870-6757
Emergency Permittee/
Owner Contact
TBD TBD
Non-Emergency Owner
Contact
Jaden Storedahl 503-899-8170
Monitoring Personnel TBD TBD
Ecology Regional Office Rachel McCrea
Northwest Regional Office
206-594-0146
Solera Townhomes – New Home Co. Page 24
Monitoring and Sampling Requirements (4.0)
Monitoring includes visual inspection, sampling for water quality parameters of concern, and
documentation of the inspection and sampling findings in a site logbook. A site logbook will be
maintained for all on-site construction activities and will include:
· A record of the implementation of the SWPPP and other permit requirements
· Site inspections
· Stormwater sampling data
File a blank form under Appendix C.
The site logbook must be maintained on-site within reasonable access to the site and be made
available upon request to Ecology or the local jurisdiction.
Numeric effluent limits may be required for certain discharges to 303(d) listed waterbodies. See
CSWGP Special Condition S8 and Section 5 of this template.
Complete the following paragraph for sites that discharge to impaired waterbodies for fine
sediment, turbidity, phosphorus, or pH:
Site Inspection (4.1)
Site inspections will be conducted at least once every calendar week and within 24 hours
following any discharge from the site. For sites that are temporarily stabilized and inactive, the
required frequency is reduced to once per calendar month.
The discharge point(s) are indicated on the Site Map (see Appendix A) and in accordance with
the applicable requirements of the CSWGP.
Solera Townhomes – New Home Co. Page 25
Stormwater Quality Sampling (4.2)
Turbidity Sampling (4.2.1)
Requirements include calibrated turbidity meter or transparency tube to sample site discharges
for compliance with the CSWGP. Sampling will be conducted at all discharge points at least
once per calendar week.
Method for sampling turbidity:
Table 8 – Turbidity Sampling Method
Y Turbidity Meter/Turbidimeter (required for disturbances 5 acres or greater in size)
Transparency Tube (option for disturbances less than 1 acre and up to 5 acres in size)
The benchmark for turbidity value is 25 nephelometric turbidity units (NTU) and a transparency
less than 33 centimeters.
If the discharge’s turbidity is 26 to 249 NTU or the transparency is less than 33 cm but equal to
or greater than 6 cm, the following steps will be conducted:
1. Review the SWPPP for compliance with Special Condition S9. Make appropriate
revisions within 7 days of the date the discharge exceeded the benchmark.
2. Immediately begin the process to fully implement and maintain appropriate source
control and/or treatment BMPs as soon as possible. Address the problems within 10
days of the date the discharge exceeded the benchmark. If installation of necessary
treatment BMPs is not feasible within 10 days, Ecology may approve additional time
when the Permittee requests an extension within the initial 10-day response period.
3. Document BMP implementation and maintenance in the site log book.
If the turbidity exceeds 250 NTU or the transparency is 6 cm or less at any time, the following
steps will be conducted:
1. Telephone or submit an electronic report to the applicable Ecology Region’s
Environmental Report Tracking System (ERTS) within 24 hours.
https://www.ecology.wa.gov/About-us/Get-involved/Report-an-environmental-issue
· Central Region (Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan, Yakima):
(509) 575-2490
· Eastern Region (Adams, Asotin, Columbia, Ferry, Franklin, Garfield, Grant,
Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, Whitman): (509) 329-3400
· Northwest Region (King, Kitsap, Island, San Juan, Skagit, Snohomish,
Whatcom): (425) 649-7000
· Southwest Region (Clallam, Clark, Cowlitz, Grays Harbor, Jefferson, Lewis,
Mason, Pacific, Pierce, Skamania, Thurston, Wahkiakum,): (360) 407-6300
Solera Townhomes – New Home Co. Page 26
2. Immediately begin the process to fully implement and maintain appropriate source
control and/or treatment BMPs as soon as possible. Address the problems within 10
days of the date the discharge exceeded the benchmark. If installation of necessary
treatment BMPs is not feasible within 10 days, Ecology may approve additional time
when the Permittee requests an extension within the initial 10-day response period
3. Document BMP implementation and maintenance in the site log book.
4. Continue to sample discharges daily until one of the following is true:
· Turbidity is 25 NTU (or lower).
· Transparency is 33 cm (or greater).
· Compliance with the water quality limit for turbidity is achieved.
o 1 - 5 NTU over background turbidity, if background is less than 50 NTU
o 1% - 10% over background turbidity, if background is 50 NTU or greater
· The discharge stops or is eliminated.
Solera Townhomes – New Home Co. Page 27
pH Sampling (4.2.2)
pH monitoring is required for “Significant concrete work” (i.e. greater than 1000 cubic yards
poured concrete or recycled concrete over the life of the project).The use of engineered soils
(soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln
dust [CKD] or fly ash) also requires pH monitoring.
For significant concrete work, pH sampling will start the first day concrete is poured and
continue until it is cured, typically three (3) weeks after the last pour.
For engineered soils and recycled concrete, pH sampling begins when engineered soils or
recycled concrete are first exposed to precipitation and continues until the area is fully
stabilized.
If the measured pH is 8.5 or greater, the following measures will be taken:
1. Prevent high pH water from entering storm sewer systems or surface water.
2. Adjust or neutralize the high pH water to the range of 6.5 to 8.5 su using appropriate
technology such as carbon dioxide (CO2) sparging (liquid or dry ice).
3. Written approval will be obtained from Ecology prior to the use of chemical treatment
other than CO2 sparging or dry ice.
Method for sampling pH:
Table 9 – pH Sampling Method
Y pH meter
pH test kit
Wide range pH indicator paper
Solera Townhomes – New Home Co. Page 28
Discharges to 303(d) or Total Maximum Daily Load (TMDL)
Waterbodies (5.0)
303(d) Listed Waterbodies (5.1)
Is the receiving water 303(d) (Category 5) listed for turbidity, fine sediment, phosphorus, or pH?
Yes No
List the impairment(s):
N/A
TMDL Waterbodies (5.2)
Waste Load Allocation for CWSGP discharges: N/A
Describe the method(s) for TMDL compliance: N/A
List and describe BMPs: N/A
Discharges to TMDL receiving waterbodies will meet in-stream water quality criteria at the point
of discharge.
The Construction Stormwater General Permit Proposed New Discharge to an Impaired Water
Body form is included in Appendix D. This was completed in phase 1 for all
Solera Townhomes – New Home Co. Page 29
Reporting and Record Keeping (6.0)
Record Keeping (6.1)
Site Log Book (6.1.1)
A site log book will be maintained for all on-site construction activities and will include:
· A record of the implementation of the SWPPP and other permit requirements
· Site inspections
· Sample logs
Records Retention (6.1.2)
Records will be retained during the life of the project and for a minimum of three (3) years
following the termination of permit coverage in accordance with Special Condition S5.C of the
CSWGP.
Permit documentation to be retained on-site:
· CSWGP
· Permit Coverage Letter
· SWPPP
· Site Log Book
Permit documentation will be provided within 14 days of receipt of a written request from
Ecology. A copy of the SWPPP or access to the SWPPP will be provided to the public when
requested in writing in accordance with Special Condition S5.G.2.b of the CSWGP.
Updating the SWPPP (6.1.3)
The SWPPP will be modified if:
· Found ineffective in eliminating or significantly minimizing pollutants in stormwater
discharges from the site.
· There is a change in design, construction, operation, or maintenance at the construction
site that has, or could have, a significant effect on the discharge of pollutants to waters
of the State.
Solera Townhomes – New Home Co. Page 30
The SWPPP will be modified within seven (7) days if inspection(s) or investigation(s) determine
additional or modified BMPs are necessary for compliance. An updated timeline for BMP
implementation will be prepared.
Reporting (6.2)
Discharge Monitoring Reports (6.2.1)
Cumulative soil disturbance is less than one (1) acre; therefore, Discharge Monitoring
Reports (DMRs) will not be submitted to Ecology because water quality sampling is not being
conducted at the site.
Notification of Noncompliance (6.2.2)
If any of the terms and conditions of the permit is not met, and the resulting noncompliance may
cause a threat to human health or the environment, the following actions will be taken:
1. Ecology will be notified within 24-hours of the failure to comply by calling the applicable
Regional office ERTS phone number (Regional office numbers listed below).
2. Immediate action will be taken to prevent the discharge/pollution or otherwise stop or
correct the noncompliance. If applicable, sampling and analysis of any noncompliance
will be repeated immediately and the results submitted to Ecology within five (5) days of
becoming aware of the violation.
3. A detailed written report describing the noncompliance will be submitted to Ecology
within five (5) days, unless requested earlier by Ecology.
Anytime turbidity sampling indicates turbidity is 250 NTUs or greater, or water transparency is 6
cm or less, the Ecology Regional office will be notified by phone within 24 hours of analysis as
required by Special Condition S5.A of the CSWGP.
· Central Region at (509) 575-2490 for Benton, Chelan, Douglas, Kittitas, Klickitat,
Okanogan, or Yakima County
· Eastern Region at (509) 329-3400 for Adams, Asotin, Columbia, Ferry, Franklin,
Garfield, Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, or Whitman
County
· Northwest Region at (425) 649-7000 for Island, King, Kitsap, San Juan, Skagit,
Snohomish, or Whatcom County
· Southwest Region at (360) 407-6300 for Clallam, Clark, Cowlitz, Grays Harbor,
Jefferson, Lewis, Mason, Pacific, Pierce, Skamania, Thurston, or Wahkiakum
Include the following information:
1. Your name and / Phone number
2. Permit number
Solera Townhomes – New Home Co. Page 31
3. City / County of project
4. Sample results
5. Date / Time of call
6. Date / Time of sample
7. Project name
In accordance with Special Condition S4.D.5.b of the CSWGP, the Ecology Regional office will
be notified if chemical treatment other than CO2 sparging is planned for adjustment of high pH
water.
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Appendices
Solera Townhomes – New Home Co. Page 33
A. Site Plan
1. TESC Plans
2. TESC Details
Solera Townhomes – New Home Co. Page 34
B. BMP Detail
High Visibility Plastic or Metal Fence (BMP C103)
Stabilized Construction Entrance (BMP C105)
Wheel Wash (BMP C106)
Temporary and Permanent Seeding (BMP C120)
Nets and Blankets (BMP C122)
Plastic Covering (BMP C123)
Sodding (BMP C124)
Topsoiling (BMP C125)
Surface Roughening (BMP C130)
Dust Control (BMP C140)
Concrete Handling (BMP C151)
Material Delivery, Storage, and Containment (BMP C153)
Concrete Washout Area (BMP C154)
Interceptor Dike and Swale (BMP C200)
Check Dams (BMP C207)
Storm Drain Inlet Protection (BMP C220)
Silt Fence (BMP C233)
Wattles (BMP C235)
II-3 Construction Stormwater BMPs
II-3.1 A Summary of Construction Stormwater
BMPs
This chapter contains standards and specifications for temporary BMPs, used as appropriate during
the construction phase of a project. Often using BMPs in combination is the best method to meet
Construction Stormwater Pollution Prevention Plan (Construction SWPPP) requirements.
The standards and specifications in this chapter are not intended to limit innovative efforts to effect-
ively control erosion and sedimentation. Construction SWPPPs can contain experimental BMPs or
make minor modifications to standard BMPs. However, the permitting authority (state, local, or both)
must approve such practices before use. Experimental and modified BMPs must achieve the same
or better performance than the BMPs listed below.
None of the BMPs listed below will work successfully throughout the construction project without
inspection and maintenance. Regular inspections to identify problems with the operation of each
BMP, and the timely repair of any problems are essential to the continued operation of the BMPs. As
site conditions change, BMPs must change to remain in compliance.
Construction stormwater BMPs are divided into two categories: Construction Source Control BMPs
and Construction Runoff BMPs.
Table II-3.1: Construction Stormwater BMPs by SWPPP Element shows the relationship of the Con-
struction Stormwater BMPs to the Construction SWPPP Elements described in I-3.4.2 MR2: Con-
struction Stormwater Pollution Prevention Plan (SWPPP).
Construction Storm-
water BMP
Construction SWPPP Element #
#1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13
Construction Source Control BMPs
BMP C101: Preserving
Natural Vegetation ü
BMP C102: Buffer
Zones ü ü
BMP C103: High-Vis-
ibility Fence ü ü
BMP C105: Stabilized
Construction Access ü
BMP C106: Wheel
Wash ü
Table II-3.1: Construction Stormwater BMPs by SWPPP Element
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Volume II -Chapter 3 -Page 267
Construction Storm-
water BMP
Construction SWPPP Element #
#1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13
BMP C107: Con-
struction Road / Parking
Area Stabilization
ü
BMP C120: Temporary
and Permanent Seeding ü ü
BMP C121: Mulching ü ü
BMP C122: Nets and
Blankets ü ü ü
BMP C123: Plastic
Covering ü ü
BMP C124: Sodding ü ü
BMP C125: Topsoiling /
Composting ü
BMP C126: Poly-
acrylamide (PAM) for
Soil Erosion Protection
ü
BMP C130: Surface
Roughening ü ü
BMP C131: Gradient
Terraces ü ü
BMP C140: Dust Con-
trol ü
BMP C150: Mater-
ials on Hand ü ü
BMP C151: Concrete
Handling ü
BMP C152: Sawcutting
and Surfacing Pollution
Prevention
ü
BMP C153: Material
Delivery, Storage, and
Containment
ü
Table II-3.1: Construction Stormwater BMPs by SWPPP Element
(continued)
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Construction Storm-
water BMP
Construction SWPPP Element #
#1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13
BMP C154: Concrete
Washout Area ü
BMP C160: Certified
Erosion and Sediment
Control Lead
ü ü
BMP C162: Scheduling ü
Construction Runoff BMPs
BMP C200: Interceptor
Dike and Swale ü ü
BMP C201: Grass-
Lined Channels ü ü
BMP C202: Riprap
Channel Lining ü
BMP C203: Water Bars ü ü ü
BMP C204: Pipe Slope
Drains ü
BMP C205: Subsurface
Drains ü
BMP C206: Level
Spreader ü ü
BMP C207: Check
Dams ü ü ü ü
BMP C208: Triangular
Silt Dike (TSD) ü ü
BMP C209: Outlet Pro-
tection ü ü
BMP C220: Inlet Pro-
tection ü
BMP C231: Brush Bar-
rier ü ü
BMP C232: Gravel Fil-
ter Berm ü
Table II-3.1: Construction Stormwater BMPs by SWPPP Element
(continued)
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Volume II -Chapter 3 -Page 269
Construction Storm-
water BMP
Construction SWPPP Element #
#1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13
BMP C233: Silt Fence ü ü
BMP C234: Vegetated
Strip ü ü
BMP C235: Wattles ü ü
BMP C236: Vegetative
Filtration ü
BMP C240: Sediment
Trap ü ü
BMP C241: Sediment
Pond (Temporary) ü ü
BMP C250: Con-
struction Stormwater
Chemical Treatment
ü ü
BMP C251: Con-
struction Stormwater
Filtration
ü ü
BMP C252: Treating
and Disposing of High
pH Water
ü
Construction SWPPP Elements:
Element 1: Preserve Vegetation / Mark Clearing Limits
Element 2: Establish Construction Access
Element 3: Control Flow Rates
Element 4: Install Sediment Controls
Element 5: Stabilize Soils
Element 6: Protect Slopes
Element 7: Protect Drain Inlets
Element 8: Stabilize Channels and Outlets
Element 9: Control Pollutants
Element 10: Control Dewatering
Element 11: Maintain BMPs
Element 12: Manage the Project
Element 13: Protect Low Impact Development BMPs
Table II-3.1: Construction Stormwater BMPs by SWPPP Element
(continued)
II-3.2 Construction Source Control BMPs
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burying and smothering vegetation.
l Vegetative buffer zones for streams, lakes or other waterways shall be established by the
local permitting authority or other state or federal permits or approvals.
Maintenance Standards
Inspect the area frequently to make sure flagging remains in place and the area remains undis-
turbed. Replace all damaged flagging immediately. Remove all materials located in the buffer area
that may impede the ability of the vegetation to act as a filter.
BMP C103: High-Visibility Fence
Purpose
High-visibility fencing is intended to:
l Restrict clearing to approved limits.
l Prevent disturbance of sensitive areas, their buffers, and other areas required to be left undis-
turbed.
l Limit construction traffic to designated construction entrances, exits, or internal roads.
l Protect areas where marking with survey tape may not provide adequate protection.
Conditions of Use
To establish clearing limits plastic, fabric, or metal fence may be used:
l At the boundary of sensitive areas, their buffers, and other areas required to be left uncleared.
l As necessary to control vehicle access to and on the site.
Design and Installation Specifications
High-visibility plastic fence shall be composed of a high-density polyethylene material and shall be at
least four feet in height. Posts for the fencing shall be steel or wood and placed every 6 feet on center
(maximum) or as needed to ensure rigidity. The fencing shall be fastened to the post every six inches
with a polyethylene tie. On long continuous lengths of fencing, a tension wire or rope shall be used as
a top stringer to prevent sagging between posts. The fence color shall be high-visibility orange. The
fence tensile strength shall be 360 lbs/ft using the ASTM D4595 testing method.
If appropriate install fabric silt fence in accordance with BMP C233: Silt Fence to act as high-visibility
fence. Silt fence shall be at least 3 feet high and must be highly visible to meet the requirements of
this BMP.
Metal fences shall be designed and installed according to the manufacturer's specifications.
Metal fences shall be at least 3 feet high and must be highly visible.
Fences shall not be wired or stapled to trees.
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Maintenance Standards
If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and
visibility restored.
BMP C105: Stabilized Construction Access
Purpose
Stabilized construction accesses are established to reduce the amount of sediment transported onto
paved roads outside the project site by vehicles or equipment. This is done by constructing a sta-
bilized pad of quarry spalls at entrances and exits for project sites.
Conditions of Use
Construction accesses shall be stabilized wherever traffic will be entering or leaving a construction
site if paved roads or other paved areas are within 1,000 feet of the site.
For residential subdivision construction sites, provide a stabilized construction access for each res-
idence, rather than only at the main subdivision entrance. Stabilized surfaces shall be of sufficient
length/width to provide vehicle access/parking, based on lot size and configuration.
On large commercial, highway, and road projects, the designer should include enough extra mater-
ials in the contract to allow for additional stabilized accesses not shown in the initial Construction
SWPPP. It is difficult to determine exactly where access to these projects will take place; additional
materials will enable the contractor to install them where needed.
Design and Installation Specifications
See Figure II-3.1: Stabilized Construction Access for details. Note: the 100’ minimum length of the
access shall be reduced to the maximum practicable size when the size or configuration of the site
does not allow the full length (100’).
Construct stabilized construction accesses with a 12-inch thick pad of 4-inch to 8-inch quarry spalls,
a 4-inch course of asphalt treated base (ATB), or use existing pavement. Do not use crushed con-
crete, cement, or calcium chloride for construction access stabilization because these products raise
pH levels in stormwater and concrete discharge to waters of the State is prohibited.
A separation geotextile shall be placed under the spalls to prevent fine sediment from pumping up
into the rock pad. The geotextile shall meet the standards listed in Table II-3.2: Stabilized Con-
struction Access Geotextile Standards.
Geotextile Property Required Value
Grab Tensile Strength (ASTM D4751)200 psi min.
Table II-3.2: Stabilized Construction Access
Geotextile Standards
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Geotextile Property Required Value
Grab Tensile Elongation (ASTM D4632)30% max.
Mullen Burst Strength (ASTM D3786-80a)400 psi min.
AOS (ASTM D4751)20-45 (U.S. standard sieve size)
Table II-3.2: Stabilized Construction Access
Geotextile Standards (continued)
l Consider early installation of the first lift of asphalt in areas that will be paved; this can be used
as a stabilized access. Also consider the installation of excess concrete as a stabilized access.
During large concrete pours, excess concrete is often available for this purpose.
l Fencing (see BMP C103: High-Visibility Fence) shall be installed as necessary to restrict
traffic to the construction access.
l Whenever possible, the access shall be constructed on a firm, compacted subgrade. This can
substantially increase the effectiveness of the pad and reduce the need for maintenance.
l Construction accesses should avoid crossing existing sidewalks and back of walk drains if at
all possible. If a construction access must cross a sidewalk or back of walk drain, the full length
of the sidewalk and back of walk drain must be covered and protected from sediment leaving
the site.
Alternative Material Specification
WSDOT has raised safety concerns about the Quarry Spall rock specified above. WSDOT observes
that the 4-inch to 8-inch rock sizes can become trapped between Dually truck tires, and then
released off-site at highway speeds. WSDOT has chosen to use a modified specification for the rock
while continuously verifying that the Stabilized Construction Access remains effective. To remain
effective, the BMP must prevent sediment from migrating off site. To date, there has been no per-
formance testing to verify operation of this new specification. Jurisdictions may use the alternative
specification, but must perform increased off-site inspection if they use, or allow others to use, it.
Stabilized Construction Accesses may use material that meets the requirements of WSDOT's Stand-
ard Specifications for Road, Bridge, and Municipal Construction Section 9-03.9(1) (WSDOT, 2016)
for ballast except for the following special requirements.
The grading and quality requirements are listed in Table II-3.3: Stabilized Construction Access
Alternative Material Requirements.
Sieve Size Percent Passing
2½″99-100
Table II-3.3: Stabilized
Construction Access
Alternative Material
Requirements
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Sieve Size Percent Passing
2″65-100
¾″40-80
No. 4 5 max.
No. 100 0-2
% Fracture 75 min.
Table II-3.3: Stabilized
Construction Access
Alternative Material
Requirements
(continued)
l All percentages are by weight.
l The sand equivalent value and dust ratio requirements do not apply.
l The fracture requirement shall be at least one fractured face and will apply the combined
aggregate retained on the No. 4 sieve in accordance with FOP for AASHTO T 335.
Maintenance Standards
Quarry spalls shall be added if the pad is no longer in accordance with the specifications.
l If the access is not preventing sediment from being tracked onto pavement, then alternative
measures to keep the streets free of sediment shall be used. This may include replace-
ment/cleaning of the existing quarry spalls, street sweeping, an increase in the dimensions of
the access, or the installation of BMP C106: Wheel Wash.
l Any sediment that is tracked onto pavement shall be removed by shoveling or street sweep-
ing. The sediment collected by sweeping shall be removed or stabilized on site. The pavement
shall not be cleaned by washing down the street, except when high efficiency sweeping is inef-
fective and there is a threat to public safety. If it is necessary to wash the streets, the con-
struction of a small sump to contain the wash water shall be considered. The sediment would
then be washed into the sump where it can be controlled.
l Perform street sweeping by hand or with a high efficiency sweeper. Do not use a non-high effi-
ciency mechanical sweeper because this creates dust and throws soils into storm systems or
conveyance ditches.
l Any quarry spalls that are loosened from the pad, which end up on the roadway shall be
removed immediately.
l If vehicles are entering or exiting the site at points other than the construction access(es),
BMP C103: High-Visibility Fence shall be installed to control traffic.
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l Upon project completion and site stabilization, all construction accesses intended as per-
manent access for maintenance shall be permanently stabilized.
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Figure II-3.1: Stabilized Construction Access
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Approved as Functionally Equivalent
Ecology has approved products as able to meet the requirements of this BMP. The products did not
pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions
may choose not to accept these products, or may require additional testing prior to consideration for
local use. Products that Ecology has approved as functionally equivalent are available for review on
Ecology’s website at:
https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per-
mittee-guidance-resources/Emerging-stormwater-treatment-technologies
BMP C106: Wheel Wash
Purpose
Wheel washes reduce the amount of sediment transported onto paved roads by washing dirt from
the wheels of motor vehicles prior to the motor vehicles leaving the construction site.
Conditions of Use
l Use a wheel wash when BMP C105: Stabilized Construction Access is not preventing sed-
iment from being tracked off site.
l Wheel washing is generally an effective BMP when installed with careful attention to topo-
graphy. For example, a wheel wash can be detrimental if installed at the top of a slope abut-
ting a right-of-way where the water from the dripping truck can run unimpeded into the street.
l Pressure washing combined with an adequately sized and surfaced pad with direct drainage
to a large 10-foot x 10-foot sump can be very effective.
l Wheel wash wastewater is not stormwater. It is commonly called process water, and must be
discharged to a separate on-site treatment system that prevents discharge to waters of the
State, or to the sanitary sewer with local sewer district approval.
l Wheel washes may use closed-loop recirculation systems to conserve water use.
l Wheel wash wastewater shall not include wastewater from concrete washout areas.
l When practical, the wheel wash should be placed in sequence with BMP C105: Stabilized
Construction Access. Locate the wheel wash such that vehicles exiting the wheel wash will
enter directly onto BMP C105: Stabilized Construction Access. In order to achieve this, BMP
C105: Stabilized Construction Access may need to be extended beyond the standard install-
ation to meet the exit of the wheel wash.
Design and Installation Specifications
Suggested details are shown in Figure II-3.2: Wheel Wash. The Local Permitting Authority may
allow other designs. A minimum of 6 inches of asphalt treated base (ATB) over crushed base mater-
ial or 8 inches over a good subgrade is recommended to pave the wheel wash.
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Use a low clearance truck to test the wheel wash before paving. Either a belly dump or lowboy will
work well to test clearance.
Keep the water level from 12 to 14 inches deep to avoid damage to truck hubs and filling the truck
tongues with water.
Midpoint spray nozzles are only needed in extremely muddy conditions.
Wheel wash systems should be designed with a small grade change, 6- to 12-inches for a 10-foot-
wide pond, to allow sediment to flow to the low side of pond to help prevent re-suspension of sed-
iment. A drainpipe with a 2- to 3-foot riser should be installed on the low side of the pond to allow for
easy cleaning and refilling. Polymers may be used to promote coagulation and flocculation in a
closed-loop system. Polyacrylamide (PAM) added to the wheel wash water at a rate of 0.25 - 0.5
pounds per 1,000 gallons of water increases effectiveness and reduces cleanup time. If PAM is
already being used for dust or erosion control and is being applied by a water truck, the same truck
can be used to change the wash water.
Maintenance Standards
The wheel wash should start out each day with fresh water.
The wheel wash water should be changed a minimum of once per day. On large earthwork jobs
where more than 10-20 trucks per hour are expected, the wheel wash water will need to be changed
more often.
Approved as Functionally Equivalent
Ecology has approved products as able to meet the requirements of this BMP. The products did not
pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions
may choose not to accept these products, or may require additional testing prior to consideration for
local use. Products that Ecology has approved as functionally equivalent are available for review on
Ecology’s website at:
https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per-
mittee-guidance-resources/Emerging-stormwater-treatment-technologies
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Figure II-3.2: Wheel Wash
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Crushed rock, gravel base, etc., shall be added as required to maintain a stable driving surface and
to stabilize any areas that have eroded.
Following construction, these areas shall be restored to pre-construction condition or better to pre-
vent future erosion.
Perform street cleaning at the end of each day or more often if necessary.
BMP C120: Temporary and Permanent Seeding
Purpose
Seeding reduces erosion by stabilizing exposed soils. A well-established vegetative cover is one of
the most effective methods of reducing erosion.
Conditions of Use
Use seeding throughout the project on disturbed areas that have reached final grade or that will
remain unworked for more than 30 days.
The optimum seeding windows for western Washington are April 1 through June 30 and September
1 through October 1.
Between July 1 and August 30 seeding requires irrigation until 75 percent grass cover is established.
Between October 1 and March 30 seeding requires a cover of mulch or an erosion control blanket
until 75 percent grass cover is established.
Review all disturbed areas in late August to early September and complete all seeding by the end of
September. Otherwise, vegetation will not establish itself enough to provide more than average pro-
tection.
Mulch is required at all times for seeding because it protects seeds from heat, moisture loss, and
transport due to runoff. Mulch can be applied on top of the seed or simultaneously by hydroseeding.
See BMP C121: Mulching for specifications.
Seed and mulch all disturbed areas not otherwise vegetated at final site stabilization. Final sta-
bilization means the completion of all soil disturbing activities at the site and the establishment of a
permanent vegetative cover, or equivalent permanent stabilization measures (such as pavement,
riprap, gabions, or geotextiles) which will prevent erosion. See BMP T5.13: Post-Construction Soil
Quality and Depth.
Design and Installation Specifications
General
l Install channels intended for vegetation before starting major earthwork and hydroseed with a
Bonded Fiber Matrix. For vegetated channels that will have high flows, install erosion control
blankets over the top of hydroseed. Before allowing water to flow in vegetated channels,
establish 75 percent vegetation cover. If vegetated channels cannot be established by seed
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before water flow; install sod in the channel bottom — over top of hydromulch and erosion con-
trol blankets.
l Confirm the installation of all required surface water control measures to prevent seed from
washing away.
l Hydroseed applications shall include a minimum of 1,500 pounds per acre of mulch with 3 per-
cent tackifier. See BMP C121: Mulching for specifications.
l Areas that will have seeding only and not landscaping may need compost or meal-based
mulch included in the hydroseed in order to establish vegetation. Re-install native topsoil on
the disturbed soil surface before application. See BMP T5.13: Post-Construction Soil Quality
and Depth.
l When installing seed via hydroseeding operations, only about 1/3 of the seed actually ends up
in contact with the soil surface. This reduces the ability to establish a good stand of grass
quickly. To overcome this, consider increasing seed quantities by up to 50 percent.
l Enhance vegetation establishment by dividing the hydromulch operation into two phases:
o Phase 1- Install all seed and fertilizer with 25-30 percent mulch and tackifier onto soil in
the first lift.
o Phase 2- Install the rest of the mulch and tackifier over the first lift.
Or, enhance vegetation by:
o Installing the mulch, seed, fertilizer, and tackifier in one lift.
o Spread or blow straw over the top of the hydromulch at a rate of 800-1000 pounds per
acre.
o Hold straw in place with a standard tackifier.
Both of these approaches will increase cost moderately but will greatly improve and enhance
vegetative establishment. The increased cost may be offset by the reduced need for:
o Irrigation.
o Reapplication of mulch.
o Repair of failed slope surfaces.
This technique works with standard hydromulch (1,500 pounds per acre minimum) and Bon-
ded Fiber Matrix/ Mechanically Bonded Fiber Matrix (BFM/MBFMs) (3,000 pounds per acre
minimum).
l Seed may be installed by hand if:
o Temporary and covered by straw, mulch, or topsoil.
o Permanent in small areas (usually less than 1 acre) and covered with mulch, topsoil, or
erosion blankets.
l The seed mixes listed in Table II-3.4: Temporary and Permanent Seed Mixes include
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recommended mixes for both temporary and permanent seeding.
l Apply these mixes, with the exception of the wet area seed mix, at a rate of 120 pounds per
acre. This rate can be reduced if soil amendments or slow-release fertilizers are used. Apply
the wet area seed mix at a rate of 60 pounds per acre.
l Consult the local suppliers or the local conservation district for their recommendations. The
appropriate mix depends on a variety of factors, including location, exposure, soil type, slope,
and expected foot traffic. Alternative seed mixes approved by the local authority may be used,
depending on the soil type and hydrology of the area.
Common Name Latin Name % Weight % Purity % Germination
Temporary Erosion Control Seed Mix
A standard mix for areas requiring a temporary vegetative cover.
Chewings or
annual blue grass
Festuca rubra var.
commutata or Poa
anna
40 98 90
Perennial rye Lolium perenne 50 98 90
Redtop or colonial
bentgrass
Agrostis alba or
Agrostis tenuis 5 92 85
White dutch clover Trifolium repens 5 98 90
Landscaping Seed Mix
A recommended mix for landscaping seed.
Perennial rye blend Lolium perenne 70 98 90
Chewings and red
fescue blend
Festuca rubra var.
commutata or Fes-
tuca rubra
30 98 90
Low-Growing Turf Seed Mix
A turf seed mix for dry situations where there is no need for watering. This mix requires very little main-
tenance.
Dwarf tall fescue
(several varieties)
Festuca arundin-
acea var. 45 98 90
Dwarf perennial
rye (Barclay)
Lolium perenne
var. barclay 30 98 90
Red fescue Festuca rubra 20 98 90
Colonial bentgrass Agrostis tenuis 5 98 90
Bioswale Seed Mix
A seed mix for bioswales and other intermittently wet areas.
Tall or meadow fes-Festuca arundin-75-80 98 90
Table II-3.4: Temporary and Permanent Seed Mixes
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Common Name Latin Name % Weight % Purity % Germination
cue acea or Festuca
elatior
Seaside/Creeping
bentgrass Agrostis palustris 10-15 92 85
Redtop bentgrass Agrostis alba or
Agrostis gigantea 5-10 90 80
Wet Area Seed Mix
A low-growing, relatively non-invasive seed mix appropriate for very wet areas that are not regulated wet-
lands. Consult Hydraulic Permit Authority (HPA) for seed mixes if applicable.
Tall or meadow fes-
cue
Festuca arundin-
acea or Festuca
elatior
60-70 98 90
Seaside/Creeping
bentgrass Agrostis palustris 10-15 98 85
Meadow foxtail Alepocurus praten-
sis 10-15 90 80
Alsike clover Trifolium hybridum 1-6 98 90
Redtop bentgrass Agrostis alba 1-6 92 85
Meadow Seed Mix
A recommended meadow seed mix for infrequently maintained areas or non-maintained areas where col-
onization by native plants is desirable. Likely applications include rural road and utility right-of-way. Seed-
ing should take place in September or very early October in order to obtain adequate establishment prior to
the winter months. Consider the appropriateness of clover, a fairly invasive species, in the mix. Amending
the soil can reduce the need for clover.
Redtop or Oregon
bentgrass
Agrostis alba or
Agrostis ore-
gonensis
20 92 85
Red fescue Festuca rubra 70 98 90
White dutch clover Trifolium repens 10 98 90
Table II-3.4: Temporary and Permanent Seed Mixes (continued)
Roughening and Rototilling
l The seedbed should be firm and rough. Roughen all soil no matter what the slope. Track walk
slopes before seeding if engineering purposes require compaction. Backblading or smoothing
of slopes greater than 4H:1V is not allowed if they are to be seeded.
l Restoration-based landscape practices require deeper incorporation than that provided by a
simple single-pass rototilling treatment. Wherever practical, initially rip the subgrade to
improve long-term permeability, infiltration, and water inflow qualities. At a minimum,
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permanent areas shall use soil amendments to achieve organic matter and permeability per-
formance defined in engineered soil/landscape systems. For systems that are deeper than 8
inches complete the rototilling process in multiple lifts, or prepare the engineered soil system
per specifications and place to achieve the specified depth.
Fertilizers
l Conducting soil tests to determine the exact type and quantity of fertilizer is recommended.
This will prevent the over-application of fertilizer.
l Organic matter is the most appropriate form of fertilizer because it provides nutrients (includ-
ing nitrogen, phosphorus, and potassium) in the least water-soluble form.
l In general, use 10-4-6 N-P-K (nitrogen-phosphorus-potassium) fertilizer at a rate of 90
pounds per acre. Always use slow-release fertilizers because they are more efficient and
have fewer environmental impacts. Do not add fertilizer to the hydromulch machine, or agit-
ate, more than 20 minutes before use. Too much agitation destroys the slow-release coating.
l There are numerous products available that take the place of chemical fertilizers. These
include several with seaweed extracts that are beneficial to soil microbes and organisms. If
100 percent cottonseed meal is used as the mulch in hydroseed, chemical fertilizer may not be
necessary. Cottonseed meal provides a good source of long-term, slow-release, available
nitrogen.
Bonded Fiber Matrix and Mechanically Bonded Fiber Matrix
l On steep slopes use Bonded Fiber Matrix (BFM) or Mechanically Bonded Fiber Matrix
(MBFM) products. Apply BFM/MBFM products at a minimum rate of 3,000 pounds per acre
with approximately 10 percent tackifier. Achieve a minimum of 95 percent soil coverage during
application. Numerous products are available commercially. Most products require 24-36
hours to cure before rainfall and cannot be installed on wet or saturated soils. Generally,
products come in 40-50 pound bags and include all necessary ingredients except for seed and
fertilizer.
l Install products per manufacturer's instructions.
l BFMs and MBFMs provide good alternatives to blankets in most areas requiring vegetation
establishment. Advantages over blankets include:
o BFM and MBFMs do not require surface preparation.
o Helicopters can assist in installing BFM and MBFMs in remote areas.
o On slopes steeper than 2.5H:1V, blanket installers may require ropes and harnesses
for safety.
o Installing BFM and MBFMs can save at least $1,000 per acre compared to blankets.
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Maintenance Standards
Reseed any seeded areas that fail to establish at least 75 percent cover (100 percent cover for areas
that receive sheet or concentrated flows). If reseeding is ineffective, use an alternate method such
as sodding, mulching, nets, or blankets.
l Reseed and protect by mulch any areas that experience erosion after achieving adequate
cover. Reseed and protect by mulch any eroded area.
l Supply seeded areas with adequate moisture, but do not water to the extent that it causes run-
off.
Approved as Functionally Equivalent
Ecology has approved products as able to meet the requirements of this BMP. The products did not
pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions
may choose not to accept these products, or may require additional testing prior to consideration for
local use. Products that Ecology has approved as functionally equivalent are available for review on
Ecology’s website at:
https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per-
mittee-guidance-resources/Emerging-stormwater-treatment-technologies
BMP C121: Mulching
Purpose
Mulching soils provides immediate temporary protection from erosion. Mulch also enhances plant
establishment by conserving moisture, holding fertilizer, seed, and topsoil in place, and moderating
soil temperatures. There are a variety of mulches that can be used. This section discusses only the
most common types of mulch.
Conditions of Use
As a temporary cover measure, mulch should be used:
l For less than 30 days on disturbed areas that require cover.
l At all times for seeded areas, especially during the wet season and during the hot summer
months.
l During the wet season on slopes steeper than 3H:1V with more than 10 feet of vertical relief.
Mulch may be applied at any time of the year and must be refreshed periodically.
For seeded areas, mulch may be made up of 100 percent:
l cottonseed meal;
l fibers made of wood, recycled cellulose, hemp, or kenaf;
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Mulch Mater-
ial Guideline Description
Remarks
This is a cost-effective way to dispose of debris from clearing and grub-
bing, and it eliminates the problems associated with burning. Generally, it
should not be used on slopes above approx. 10% because of its tendency
to be transported by runoff. It is not recommended within 200 feet of sur-
face waters. If permanent seeding or planting is expected shortly after
mulch, the decomposition of the chipped vegetation may tie up nutrients
important to grass establishment.
Note: thick application of this material over existing grass, herbaceous spe-
cies, and some groundcovers could smother and kill vegetation.
Wood-
Based
Mulch
Quality
Standards
No visible water or dust during handling. Must be purchased from a supplier
with a Solid Waste Handling Permit or one exempt from solid waste reg-
ulations.
Application
Rates 2" thick min.; approx. 100 tons per acre (approx. 750 lbs. per cubic yard)
Remarks
This material is often called "wood straw" or "hog fuel". The use of mulch
ultimately improves the organic matter in the soil. Special caution is
advised regarding the source and composition of wood-based mulches. Its
preparation typically does not provide any weed seed control, so evidence
of residual vegetation in its composition or known inclusion of weed plants
or seeds should be monitored and prevented (or minimized).
Wood
Strand
Mulch
Quality
Standards
A blend of loose, long, thin wood pieces derived from native conifer or
deciduous trees with high length-to-width ratio.
Application
Rates 2" thick min.
Remarks
Cost-effective protection when applied with adequate thickness. A min-
imum of 95-percent of the wood strand shall have lengths between 2 and
10-inches, with a width and thickness between 1/16 and 1/2-inches. The
mulch shall not contain resin, tannin, or other compounds in quantities that
would be detrimental to plant life. Sawdust or wood shavings shall not be
used as mulch. [Specification 9-14.4(4) from the Standard Specifications
for Road, Bridge, and Municipal Construction (WSDOT, 2016)
Table II-3.6: Mulch Standards and Guidelines (continued)
BMP C122: Nets and Blankets
Purpose
Erosion control nets and blankets are intended to prevent erosion and hold seed and mulch in place
on steep slopes and in channels so that vegetation can become well established. In addition, some
nets and blankets can be used to permanently reinforce turf to protect drainage ways during high
flows.
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Nets (commonly called matting) are strands of material woven into an open, but high-tensile strength
net (for example, coconut fiber matting). Blankets are strands of material that are not tightly woven,
but instead form a layer of interlocking fibers, typically held together by a biodegradable or pho-
todegradable netting (for example, excelsior or straw blankets). They generally have lower tensile
strength than nets, but cover the ground more completely. Coir (coconut fiber) fabric comes as both
nets and blankets.
Conditions of Use
Erosion control netting and blankets shall be made of natural plant fibers unaltered by synthetic
materials.
Erosion control nets and blankets should be used:
l To aid permanent vegetated stabilization of slopes 2H:1V or greater and with more than 10
feet of vertical relief.
l For drainage ditches and swales (highly recommended). The application of appropriate net-
ting or blanket to drainage ditches and swales can protect bare soil from channelized runoff
while vegetation is established. Nets and blankets also can capture a great deal of sediment
due to their open, porous structure. Nets and blankets can be used to permanently stabilize
channels and may provide a cost-effective, environmentally preferable alternative to riprap.
Disadvantages of nets and blankets include:
l Surface preparation is required.
l On slopes steeper than 2.5H:1V, net and blanket installers may need to be roped and har-
nessed for safety.
l They cost at least $4,000-6,000 per acre installed.
Advantages of nets and blankets include:
l Installation without mobilizing special equipment.
l Installation by anyone with minimal training
l Installation in stages or phases as the project progresses.
l Installers can hand place seed and fertilizer as they progress down the slope.
l Installation in any weather.
l There are numerous types of nets and blankets that can be designed with various parameters
in mind. Those parameters include: fiber blend, mesh strength, longevity, biodegradability,
cost, and availability.
An alternative to nets and blankets in some limited conditions is BMP C202: Riprap Channel Lining.
Ensure that BMP C202: Riprap Channel Lining is appropriate before using it as a substitute for nets
and blankets.
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Design and Installation Specifications
l See Figure II-3.3: Channel Installation (Clackamas County et al., 2008) and Figure II-3.4:
Slope Installation for typical orientation and installation of nets and blankets used in channels
and as slope protection. Note: these are typical only; all nets and blankets must be installed
per manufacturer’s installation instructions.
l Installation is critical to the effectiveness of these products. If good ground contact is not
achieved, runoff can concentrate under the product, resulting in significant erosion.
l Installation of nets and blankets on slopes:
1. Complete final grade and track walk up and down the slope.
2. Install hydromulch with seed and fertilizer.
3. Dig a small trench, approximately 12 inches wide by 6 inches deep along the top of the
slope.
4. Install the leading edge of the net/blanket into the small trench and staple approximately
every 18 inches. NOTE: Staples are metal, “U”-shaped, and a minimum of 6 inches
long. Longer staples are used in sandy soils. Biodegradable stakes are also available.
5. Roll the net/blanket slowly down the slope as the installer walks backward. NOTE: The
net/blanket rests against the installer’s legs. Staples are installed as the net/blanket is
unrolled. It is critical that the proper staple pattern is used for the net/blanket being
installed. The net/blanket is not to be allowed to roll down the slope on its own as this
stretches the net/blanket, making it impossible to maintain soil contact. In addition, no
one is allowed to walk on the net/blanket after it is in place.
6. If the net/blanket is not long enough to cover the entire slope length, the trailing edge of
the upper net/blanket should overlap the leading edge of the lower net/blanket and be
stapled. On steeper slopes, this overlap should be installed in a small trench, stapled,
and covered with soil.
l With the variety of products available, it is impossible to cover all the details of appropriate use
and installation. Therefore, it is critical that the designer consult the manufacturer's inform-
ation and that a site visit takes place in order to ensure that the product specified is appro-
priate. Information is also available in WSDOT's Standard Specifications for Road, Bridge,
and Municipal Construction Division 8-01 and Division 9-14 (WSDOT, 2016).
l Use jute matting in conjunction with mulch (BMP C121: Mulching). Excelsior, woven straw
blankets and coir (coconut fiber) blankets may be installed without mulch. There are many
other types of erosion control nets and blankets on the market that may be appropriate in cer-
tain circumstances.
l In general, most nets (e.g., jute matting) require mulch in order to prevent erosion because
they have a fairly open structure. Blankets typically do not require mulch because they usually
provide complete protection of the surface.
l Extremely steep, unstable, wet, or rocky slopes are often appropriate candidates for use of
synthetic blankets, as are riverbanks, beaches and other high-energy environments. If
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synthetic blankets are used, the soil should be hydromulched first.
l 100-percent biodegradable blankets are available for use in sensitive areas. These organic
blankets are usually held together with a paper or fiber mesh and stitching which may last up
to a year.
l Most netting used with blankets is photodegradable, meaning it breaks down under sunlight
(not UV stabilized). However, this process can take months or years even under bright sun.
Once vegetation is established, sunlight does not reach the mesh. It is not uncommon to find
non-degraded netting still in place several years after installation. This can be a problem if
maintenance requires the use of mowers or ditch cleaning equipment. In addition, birds and
small animals can become trapped in the netting.
Maintenance Standards
l Maintain good contact with the ground. Erosion must not occur beneath the net or blanket.
l Repair and staple any areas of the net or blanket that are damaged or not in close contact with
the ground.
l Fix and protect eroded areas if erosion occurs due to poorly controlled drainage.
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Figure II-3.3: Channel Installation
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Figure II-3.4: Slope Installation
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BMP C123: Plastic Covering
Purpose
Plastic covering provides immediate, short-term erosion protection to slopes and disturbed areas.
Conditions of Use
Plastic covering may be used on disturbed areas that require cover measures for less than 30 days,
except as stated below.
l Plastic is particularly useful for protecting cut and fill slopes and stockpiles. However, the rel-
atively rapid breakdown of most polyethylene sheeting makes it unsuitable for applications
greater than six months.
l Due to rapid runoff caused by plastic covering, do not use this method upslope of areas that
might be adversely impacted by concentrated runoff. Such areas include steep and/or
unstable slopes.
l Plastic sheeting may result in increased runoff volumes and velocities, requiring additional on-
site measures to counteract the increases. Creating a trough with wattles or other material
can convey clean water away from these areas.
l To prevent undercutting, trench and backfill rolled plastic covering products.
l Although the plastic material is inexpensive to purchase, the cost of installation, maintenance,
removal, and disposal add to the total costs of this BMP.
l Whenever plastic is used to protect slopes, install water collection measures at the base of the
slope. These measures include plastic-covered berms, channels, and pipes used to convey
clean rainwater away from bare soil and disturbed areas. Do not mix clean runoff from a
plastic covered slope with dirty runoff from a project.
l Other uses for plastic include:
o Temporary ditch liner.
o Pond liner in temporary sediment pond.
o Liner for bermed temporary fuel storage area if plastic is not reactive to the type of fuel
being stored.
o Emergency slope protection during heavy rains.
o Temporary drainpipe (“elephant trunk”) used to direct water.
Design and Installation Specifications
l Plastic slope cover must be installed as follows:
1. Run plastic up and down the slope, not across the slope.
2. Plastic may be installed perpendicular to a slope if the slope length is less than 10 feet.
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3. Provide a minimum of 8-inch overlap at the seams.
4. On long or wide slopes, or slopes subject to wind, tape all seams.
5. Place plastic into a small (12-inch wide by 6-inch deep) slot trench at the top of the slope
and backfill with soil to keep water from flowing underneath.
6. Place sand filled burlap or geotextile bags every 3 to 6 feet along seams and tie them
together with twine to hold them in place.
7. Inspect plastic for rips, tears, and open seams regularly and repair immediately. This
prevents high velocity runoff from contacting bare soil, which causes extreme erosion.
8. Sandbags may be lowered into place tied to ropes. However, all sandbags must be
staked in place.
l Plastic sheeting shall have a minimum thickness of 0.06 millimeters.
l If erosion at the toe of a slope is likely, a gravel berm, riprap, or other suitable protection shall
be installed at the toe of the slope in order to reduce the velocity of runoff.
Maintenance Standards
l Torn sheets must be replaced and open seams repaired.
l Completely remove and replace the plastic if it begins to deteriorate due to ultraviolet radi-
ation.
l Completely remove plastic when no longer needed.
l Dispose of old tires used to weight down plastic sheeting appropriately.
Approved as Functionally Equivalent
Ecology has approved products as able to meet the requirements of this BMP. The products did not
pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions
may choose not to accept these products, or may require additional testing prior to consideration for
local use. Products that Ecology has approved as functionally equivalent are available for review on
Ecology’s website at:
https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per-
mittee-guidance-resources/Emerging-stormwater-treatment-technologies
BMP C124: Sodding
Purpose
The purpose of sodding is to establish turf for immediate erosion protection and to stabilize drainage
paths where concentrated overland flow will occur.
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Conditions of Use
Sodding may be used in the following areas:
l Disturbed areas that require short-term or long-term cover.
l Disturbed areas that require immediate vegetative cover.
l All waterways that require vegetative lining. Waterways may also be seeded rather than sod-
ded, and protected with a net or blanket.
Design and Installation Specifications
Sod shall be free of weeds, of uniform thickness (approximately 1-inch thick), and shall have a dense
root mat for mechanical strength.
The following steps are recommended for sod installation:
1. Shape and smooth the surface to final grade in accordance with the approved grading plan.
Consider any areas (such as swales) that need to be overexcavated below design elevation to
allow room for placing soil amendment and sod.
2. Amend 4 inches (minimum) of compost into the top 8 inches of the soil if the organic content of
the soil is less than ten percent or the permeability is less than 0.6 inches per hour. See
https://ecology.wa.gov/Waste-Toxics/Reducing-recycling-waste/Organic-mater-
ials/Managing-organics-compost for further information.
3. Fertilize according to the sod supplier's recommendations.
4. Work lime and fertilizer 1 to 2 inches into the soil, and smooth the surface.
5. Lay strips of sod beginning at the lowest area to be sodded and perpendicular to the direction
of water flow. Wedge strips securely into place. Square the ends of each strip to provide for a
close, tight fit. Stagger joints at least 12 inches. Staple on slopes steeper than 3H:1V. Staple
the upstream edge of each sod strip.
6. Roll the sodded area and irrigate.
7. When sodding is carried out in alternating strips or other patterns, seed the areas between the
sod immediately after sodding.
Maintenance Standards
If the grass is unhealthy, the cause shall be determined and appropriate action taken to reestablish a
healthy groundcover. If it is impossible to establish a healthy groundcover due to frequent saturation,
instability, or some other cause, the sod shall be removed, the area seeded with an appropriate mix,
and protected with a net or blanket.
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BMP C125: Topsoiling / Composting
Purpose
Topsoiling and composting provide a suitable growth medium for final site stabilization with veget-
ation. While not a permanent cover practice in itself, topsoiling and composting are an integral com-
ponent of providing permanent cover in those areas where there is an unsuitable soil surface for
plant growth. Use this BMP in conjunction with other BMPs such as BMP C120: Temporary and Per-
manent Seeding, BMP C121: Mulching, or BMP C124: Sodding. Implementation of this BMP may
meet the post-construction requirements of BMP T5.13: Post-Construction Soil Quality and Depth.
Native soils and disturbed soils that have been organically amended not only retain much more
stormwater, but also serve as effective biofilters for urban pollutants and, by supporting more vig-
orous plant growth, reduce the water, fertilizer and pesticides needed to support installed land-
scapes. Topsoil does not include any subsoils but only the material from the top several inches
including organic debris.
Conditions of Use
l Permanent landscaped areas shall contain healthy topsoil that reduces the need for fertilizers,
improves overall topsoil quality, provides for better vegetative health and vitality, improves
hydrologic characteristics, and reduces the need for irrigation.
l Leave native soils and the duff layer undisturbed to the maximum extent practicable. Stripping
of existing, properly functioning soil system and vegetation for the purpose of topsoiling during
construction is not acceptable. Preserve existing soil systems in undisturbed and uncom-
pacted conditions if functioning properly.
l Areas that already have good topsoil, such as undisturbed areas, do not require soil amend-
ments.
l Restore, to the maximum extent practical, native soils disturbed during clearing and grading to
a condition equal to or better than the original site condition’s moisture-holding capacity. Use
on-site native topsoil, incorporate amendments into on-site soil, or import blended topsoil to
meet this requirement.
l Topsoiling is a required procedure when establishing vegetation on shallow soils, and soils of
critically low pH (high acid) levels.
l Beware of where the topsoil comes from, and what vegetation was on site before disturbance.
Invasive plant seeds may be included and could cause problems for establishing native plants,
landscaped areas, or grasses.
l Topsoil from the site will contain mycorrhizal bacteria that are necessary for healthy root
growth and nutrient transfer. These native mycorrhiza are acclimated to the site and will
provide optimum conditions for establishing grasses. Use commercially available mycorrhiza
products when using off-site topsoil.
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Design and Installation Specifications
Meet the following requirements for disturbed areas that will be developed as lawn or landscaped
areas at the completed project site:
l Maximize the depth of the topsoil wherever possible to provide the maximum possible infilt-
ration capacity and beneficial growth medium. Topsoil shall have:
o A minimum depth of 8-inches. Scarify subsoils below the topsoil layer at least 4-inches
with some incorporation of the upper material to avoid stratified layers, where feasible.
Ripping or re-structuring the subgrade may also provide additional benefits regarding
the overall infiltration and interflow dynamics of the soil system.
o A minimum organic content of 10% dry weight in planting beds, and 5% organic matter
content in turf areas. Incorporate organic amendments to a minimum 8-inch depth
except where tree roots or other natural features limit the depth of incorporation.
o A pH between 6.0 and 8.0 or matching the pH of the undisturbed soil.
o If blended topsoil is imported, then fines should be limited to 25 percent passing through
a 200 sieve.
l Mulch planting beds with 2 inches of organic material
l Accomplish the required organic content, depth, and pH by returning native topsoil to the site,
importing topsoil of sufficient organic content, and/or incorporating organic amendments.
When using the option of incorporating amendments to meet the organic content requirement,
use compost that meets the compost specification for Bioretention (See BMP T7.30: Biore-
tention), with the exception that the compost may have up to 35% biosolids or manure.
l Sections 3 through 7 of Building Soil: Guidelines and Resources for Implementing Soil Quality
and Depth BMP T5.13 in WDOE Stormwater Management Manual for Western Washington
(Stenn et al., 2016), provides useful guidance for implementing whichever option is chosen. It
includes guidance for pre-approved default strategies and guidance for custom strategies.
Check with your local jurisdiction concerning its acceptance of this guidance.
l The final composition and construction of the soil system will result in a natural selection or
favoring of certain plant species over time. For example, incorporation of topsoil may favor
grasses, while layering with mildly acidic, high-carbon amendments may favor more woody
vegetation.
l Allow sufficient time in scheduling for topsoil spreading prior to seeding, sodding, or planting.
l Take care when applying top soil to subsoils with contrasting textures. Sandy topsoil over
clayey subsoil is a particularly poor combination, as water creeps along the junction between
the soil layers and causes the topsoil to slough. If topsoil and subsoil are not properly bonded,
water will not infiltrate the soil profile evenly and it will be difficult to establish vegetation. The
best method to promote bonding is to actually work the topsoil into the layer below for a depth
of at least 6 inches.
l Field exploration of the site shall be made to determine if there is surface soil of sufficient
quantity and quality to justify stripping. Topsoil shall be friable and loamy (loam, sandy loam,
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silt loam, sandy clay loam, and clay loam). Avoid areas of natural ground water recharge.
l Stripping shall be confined to the immediate construction area. A 4-inch to 6-inch stripping
depth is common, but depth may vary depending on the particular soil. All surface runoff con-
trol structures shall be in place prior to stripping.
l Do not place topsoil while in a frozen or muddy condition, when the subgrade is excessively
wet, or when conditions exist that may otherwise be detrimental to proper grading or pro-
posed sodding or seeding.
l In any areas requiring grading, remove and stockpile the duff layer and topsoil on site in a des-
ignated, controlled area, not adjacent to public resources and critical areas. Reapply stock-
piled topsoil to other portions of the site where feasible.
l Locate the topsoil stockpile so that it meets specifications and does not interfere with work on
the site. It may be possible to locate more than one pile in proximity to areas where topsoil will
be used.
l Stockpiling of topsoil shall occur in the following manner:
o Side slopes of the stockpile shall not exceed 2H:1V.
o Between October 1 and April 30:
n An interceptor dike with gravel outlet and silt fence shall surround all topsoil.
n Within 2 days complete erosion control seeding, or covering stockpiles with clear
plastic, or other mulching materials.
o Between May 1 and September 30:
n An interceptor dike with gravel outlet and silt fence shall surround all topsoil if the
stockpile will remain in place for a longer period of time than active construction
grading.
n Within 7 days complete erosion control seeding, or covering stockpiles with clear
plastic, or other mulching materials.
l When native topsoil is to be stockpiled and reused the following should apply to ensure that
the mycorrhizal bacterial, earthworms, and other beneficial organisms will not be destroyed:
o Re-install topsoil within 4 to 6 weeks.
o Do not allow the saturation of topsoil with water.
o Do not use plastic covering.
Maintenance Standards
l Inspect stockpiles regularly, especially after large storm events. Stabilize any areas that have
eroded.
l Establish soil quality and depth toward the end of construction and once established, protect
from compaction, such as from large machinery use, and from erosion.
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l Plant and mulch soil after installation.
l Leave plant debris or its equivalent on the soil surface to replenish organic matter.
l Reduce and adjust, where possible, the use of irrigation, fertilizers, herbicides and pesticides,
rather than continuing to implement formerly established practices.
BMP C126: Polyacrylamide (PAM) for Soil Erosion
Protection
Purpose
Polyacrylamide (PAM) is used on construction sites to prevent soil erosion.
Applying PAM to bare soil in advance of a rain event significantly reduces erosion and controls sed-
iment in two ways. First, PAM increases the soil’s available pore volume, thus increasing infiltration
and reducing the quantity of stormwater runoff. Second, it increases flocculation of suspended
particles and aids in their deposition, thus reducing stormwater runoff turbidity and improving water
quality.
Conditions of Use
PAM shall not be directly applied to water or allowed to enter a water body. Stormwater runoff shall
pass through a sediment pond prior to discharging to surface waters.
PAM can be applied to bare soil under the following conditions:
l During rough grading operations.
l In Staging areas.
l Balanced cut and fill earthwork.
l Haul roads prior to placement of crushed rock surfacing.
l Compacted soil roadbase.
l Stockpiles.
l After final grade and before paving or final seeding and planting.
l Pit sites.
l Sites having a winter shut down. In the case of winter shut down, or where soil will remain
unworked for several months, PAM should be used together with mulch.
Design and Installation Specifications
l Do not use PAM on a slope that flows directly into a stream or wetland.
l Do not add PAM to water discharging from the site.
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l PAM designated for these uses should be "water soluble" or "linear" or "non-crosslinked".
Cross-linked or water absorbent PAM, polymerized in highly acidic (pH<2) conditions, are
used to maintain soil moisture content.
l The PAM anionic charge density may vary from 2-30 percent; a value of 18 percent is typical.
Studies conducted by the United States Department of Agriculture (USDA)/ARS demon-
strated that soil stabilization was optimized by using very high molecular weight (12-15 mg/-
mole), highly anionic (>20% hydrolysis) PAM.
l PAM tackifiers are available and being used in place of guar and alpha plantago. Typically,
PAM tackifiers should be used at a mixing rate of no more than 0.5-1 lb. per 1000 gallons of
water in a hydromulch machine. Some tackifier product instructions say to use at an applic-
ation rate of 3 – 5 lbs per acre, which can be too much. In addition, pump problems can occur
at higher application rates due to increased viscosity.
Maintenance Standards
l PAM may be reapplied on actively worked areas after a 48-hour period.
l Reapplication is not required unless PAM treated soil is disturbed or unless turbidity levels
show the need for an additional application. If PAM treated soil is left undisturbed, a reapplic-
ation may be necessary after two months. More PAM applications may be required for steep
slopes, silty and clayey soils (USDA Classification Type "C" and "D" soils), long grades, and
high precipitation areas. When PAM is applied first to bare soil and then covered with straw, a
reapplication may not be necessary for several months.
l Loss of sediment and PAM may be a basis for penalties per RCW 90.48.080.
l PAM may affect the treatment efficiency of chitosan flocculent systems.
BMP C130: Surface Roughening
Purpose
Surface roughening aids in the establishment of vegetative cover, reduces runoff velocity, increases
infiltration, and provides for sediment trapping through the provision of a rough soil surface. Hori-
zontal depressions are created by operating a tiller or other suitable equipment on the contour or by
leaving slopes in a roughened condition by not fine grading them.
Use this BMP in conjunction with other BMPs such as BMP C120: Temporary and Permanent Seed-
ing, BMP C121: Mulching, or BMP C124: Sodding.
Conditions for Use
l All slopes steeper than 3H:1V and greater than 5 vertical feet require surface roughening to a
depth of 2 to 4 inches prior to seeding.
l Areas that will not be stabilized immediately may be roughened to reduce runoff velocity until
seeding takes place.
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l Slopes with a stable rock face do not require roughening.
l Slopes where mowing is planned should not be excessively roughened.
Design and Installation Specifications
There are different methods for achieving a roughened soil surface on a slope, and the selection of
an appropriate method depends upon the type of slope. Roughening methods include stair-step
grading, grooving, contour furrows, and tracking. See Figure II-3.5: Surface Roughening by Track-
ing and Contour Furrows. Factors to be considered in choosing a roughening method are slope
steepness, mowing requirements, and whether the slope is formed by cutting or filling.
l Disturbed areas that will not require mowing may be stair-step graded, grooved, or left rough
after filling.
l Stair-step grading is particularly appropriate in soils containing large amounts of soft rock.
Each "step" catches material that sloughs from above, and provides a level site where veget-
ation can become established. Stairs should be wide enough to work with standard earth mov-
ing equipment. Stair steps must be on contour or gullies will form on the slope.
l Areas that will be mowed (these areas should have slopes less steep than 3H:1V) may have
small furrows left by disking, harrowing, raking, or seed-planting machinery operated on the
contour.
l Graded areas with slopes steeper than 3H:1V but less than 2H:1V should be roughened
before seeding. This can be accomplished in a variety of ways, including "track walking," or
driving a crawler tractor up and down the slope, leaving a pattern of cleat imprints parallel to
slope contours.
l Tracking is done by operating equipment up and down the slope to leave horizontal depres-
sions in the soil.
Maintenance Standards
l Areas that are surface roughened should be seeded as quickly as possible.
l Regular inspections should be made of the area. If rills appear, they should be re-roughened
and re-seeded immediately.
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Figure II-3.5: Surface Roughening by Tracking and Contour Furrows
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flow.
l Vertical spacing determined by the above methods may be increased as much as 0.5 feet or
10 percent, whichever is greater, to provide better alignment or location, to avoid obstacles, to
adjust for equipment size, or to reach a satisfactory outlet. The drainage area above the ter-
race should not exceed the area that would be drained by a terrace with normal spacing.
l The terrace should have enough capacity to handle the peak runoff expected from a 2-year,
24-hour design storm without overtopping.
l The terrace cross-section should be proportioned to fit the land slope.
l The ridge height should include a reasonable settlement factor.
l The ridge should have a minimum top width of 3 feet at the design height.
l The minimum cross-sectional area of the terrace channel should be 8 square feet for land
slopes of 5 percent or less, 7 square feet for slopes from 5 to 8 percent, and 6 square feet for
slopes steeper than 8 percent. The terrace can be constructed wide enough to be maintained
using a small vehicle.
Maintenance Standards
Maintenance should be performed as needed. Terraces should be inspected regularly; at least once
per year, and after large storm events.
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Figure II-3.6: Gradient Terraces
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BMP C140: Dust Control
Purpose
Dust control prevents wind transport of dust from disturbed soil surfaces onto roadways, drainage
ways, and surface waters.
Conditions of Use
Use dust control in areas (including roadways) subject to surface and air movement of dust where
on-site or off-site impacts to roadways, drainage ways, or surface waters are likely.
Design and Installation Specifications
l Vegetate or mulch areas that will not receive vehicle traffic. In areas where planting, mulching,
or paving is impractical, apply gravel or landscaping rock.
l Limit dust generation by clearing only those areas where immediate activity will take place,
leaving the remaining area(s) in the original condition. Maintain the original ground cover as
long as practical.
l Construct natural or artificial windbreaks or windscreens. These may be designed as enclos-
ures for small dust sources.
l Sprinkle the site with water until the surface is wet. Repeat as needed. To prevent carryout of
mud onto the street, refer to BMP C105: Stabilized Construction Access and BMP C106:
Wheel Wash.
l Irrigation water can be used for dust control. Irrigation systems should be installed as a first
step on sites where dust control is a concern.
l Spray exposed soil areas with a dust palliative, following the manufacturer’s instructions and
cautions regarding handling and application. Used oil is prohibited from use as a dust sup-
pressant. Local governments may approve other dust palliatives such as calcium chloride or
PAM.
l PAM (BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection) added to water at a rate
of 0.5 pounds per 1,000 gallons of water per acre and applied from a water truck is more effect-
ive than water alone. This is due to increased infiltration of water into the soil and reduced
evaporation. In addition, small soil particles are bonded together and are not as easily trans-
ported by wind. Adding PAM may reduce the quantity of water needed for dust control. Note
that the application rate specified here applies to this BMP, and is not the same application
rate that is specified in BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection, but the
downstream protections still apply.
Refer to BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection for conditions of use.
PAM shall not be directly applied to water or allowed to enter a water body.
l Contact your local Air Pollution Control Authority for guidance and training on other dust con-
trol measures. Compliance with the local Air Pollution Control Authority constitutes
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compliance with this BMP.
l Use vacuum street sweepers.
l Remove mud and other dirt promptly so it does not dry and then turn into dust.
l Techniques that can be used for unpaved roads and lots include:
o Lower speed limits. High vehicle speed increases the amount of dust stirred up from
unpaved roads and lots.
o Upgrade the road surface strength by improving particle size, shape, and mineral types
that make up the surface and base materials.
o Add surface gravel to reduce the source of dust emission. Limit the amount of fine
particles (those smaller than .075 mm) to 10 to 20 percent.
o Use geotextile fabrics to increase the strength of new roads or roads undergoing recon-
struction.
o Encourage the use of alternate, paved routes, if available.
o Apply chemical dust suppressants using the admix method, blending the product with
the top few inches of surface material. Suppressants may also be applied as surface
treatments.
o Limit dust-causing work on windy days.
o Pave unpaved permanent roads and other trafficked areas.
Maintenance Standards
Respray area as necessary to keep dust to a minimum.
BMP C150: Materials on Hand
Purpose
Keep quantities of erosion prevention and sediment control materials on the project site at all times
to be used for regular maintenance and emergency situations such as unexpected heavy rains. Hav-
ing these materials on-site reduces the time needed to replace existing or implement new BMPs
when inspections indicate that existing BMPs are not meeting the Construction SWPPP require-
ments. In addition, contractors can save money by buying some materials in bulk and storing them at
their office or yard.
Conditions of Use
l Construction projects of any size or type can benefit from having materials on hand. A small
commercial development project could have a roll of plastic and some gravel available for
immediate protection of bare soil and temporary berm construction. A large earthwork project,
such as highway construction, might have several tons of straw, several rolls of plastic, flexible
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pipe, sandbags, geotextile fabric and steel “T” posts.
l Materials should be stockpiled and readily available before any site clearing, grubbing, or
earthwork begins. A large contractor or project proponent could keep a stockpile of materials
that are available for use on several projects.
l If storage space at the project site is at a premium, the contractor could maintain the materials
at their office or yard. The office or yard must be less than an hour from the project site.
Design and Installation Specifications
Depending on project type, size, complexity, and length, materials and quantities will vary. A good
minimum list of items that will cover numerous situations includes:
l Clear Plastic, 6 mil
l Drainpipe, 6 or 8 inch diameter
l Sandbags, filled
l Straw Bales for mulching
l Quarry Spalls
l Washed Gravel
l Geotextile Fabric
l Catch Basin Inserts
l Steel "T" Posts
l Silt fence material
l Straw Wattles
Maintenance Standards
l All materials with the exception of the quarry spalls, steel “T” posts, and gravel should be kept
covered and out of both sun and rain.
l Re-stock materials as needed.
BMP C151: Concrete Handling
Purpose
Concrete work can generate process water and slurry that contain fine particles and high pH, both of
which can violate water quality standards in the receiving water. Concrete spillage or concrete dis-
charge to waters of the State is prohibited. Use this BMP to minimize and eliminate concrete, con-
crete process water, and concrete slurry from entering waters of the State.
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Conditions of Use
Any time concrete is used, utilize these management practices. Concrete construction project com-
ponents include, but are not limited to:
l Curbs
l Sidewalks
l Roads
l Bridges
l Foundations
l Floors
l Runways
Disposal options for concrete, in order of preference are:
1. Off-site disposal
2. Concrete wash-out areas (see BMP C154: Concrete Washout Area)
3. De minimus washout to formed areas awaiting concrete
Design and Installation Specifications
l Wash concrete truck drums at an approved off-site location or in designated concrete
washout areas only. Do not wash out concrete trucks onto the ground (including formed areas
awaiting concrete), or into storm drains, open ditches, streets, or streams. Refer to BMP
C154: Concrete Washout Area for information on concrete washout areas.
o Return unused concrete remaining in the truck and pump to the originating batch plant
for recycling. Do not dump excess concrete on site, except in designated concrete
washout areas as allowed in BMP C154: Concrete Washout Area.
l Wash small concrete handling equipment (e.g. hand tools, screeds, shovels, rakes, floats,
trowels, and wheelbarrows) into designated concrete washout areas or into formed areas
awaiting concrete pour.
l At no time shall concrete be washed off into the footprint of an area where an infiltration fea-
ture will be installed.
l Wash equipment difficult to move, such as concrete paving machines, in areas that do not dir-
ectly drain to natural or constructed stormwater conveyance or potential infiltration areas.
l Do not allow washwater from areas, such as concrete aggregate driveways, to drain directly
(without detention or treatment) to natural or constructed stormwater conveyances.
l Contain washwater and leftover product in a lined container when no designated concrete
washout areas (or formed areas, allowed as described above) are available. Dispose of con-
tained concrete and concrete washwater (process water) properly.
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l Always use forms or solid barriers for concrete pours, such as pilings, within 15-feet of surface
waters.
l Refer to BMP C252: Treating and Disposing of High pH Water for pH adjustment require-
ments.
l Refer to the Construction Stormwater General Permit (CSWGP) for pH monitoring require-
ments if the project involves one of the following activities:
o Significant concrete work (as defined in the CSWGP).
o The use of soils amended with (but not limited to) Portland cement-treated base,
cement kiln dust or fly ash.
o Discharging stormwater to segments of water bodies on the 303(d) list (Category 5) for
high pH.
Maintenance Standards
Check containers for holes in the liner daily during concrete pours and repair the same day.
BMP C152: Sawcutting and Surfacing Pollution
Prevention
Purpose
Sawcutting and surfacing operations generate slurry and process water that contains fine particles
and high pH (concrete cutting), both of which can violate the water quality standards in the receiving
water. Concrete spillage or concrete discharge to waters of the State is prohibited. Use this BMP to
minimize and eliminate process water and slurry created through sawcutting or surfacing from enter-
ing waters of the State.
Conditions of Use
Utilize these management practices anytime sawcutting or surfacing operations take place. Saw-
cutting and surfacing operations include, but are not limited to:
l Sawing
l Coring
l Grinding
l Roughening
l Hydro-demolition
l Bridge and road surfacing
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Design and Installation Specifications
l Vacuum slurry and cuttings during cutting and surfacing operations.
l Slurry and cuttings shall not remain on permanent concrete or asphalt pavement overnight.
l Slurry and cuttings shall not drain to any natural or constructed drainage conveyance includ-
ing stormwater systems. This may require temporarily blocking catch basins.
l Dispose of collected slurry and cuttings in a manner that does not violate ground water or sur-
face water quality standards.
l Do not allow process water generated during hydro-demolition, surface roughening or similar
operations to drain to any natural or constructed drainage conveyance including stormwater
systems. Dispose of process water in a manner that does not violate ground water or surface
water quality standards.
l Handle and dispose of cleaning waste material and demolition debris in a manner that does
not cause contamination of water. Dispose of sweeping material from a pick-up sweeper at an
appropriate disposal site.
Maintenance Standards
Continually monitor operations to determine whether slurry, cuttings, or process water could enter
waters of the state. If inspections show that a violation of water quality standards could occur, stop
operations and immediately implement preventive measures such as berms, barriers, secondary
containment, and/or vacuum trucks.
BMP C153: Material Delivery, Storage, and
Containment
Purpose
Prevent, reduce, or eliminate the discharge of pollutants to the stormwater system or watercourses
from material delivery and storage. Minimize the storage of hazardous materials on-site, store mater-
ials in a designated area, and install secondary containment.
Conditions of Use
Use at construction sites with delivery and storage of the following materials:
l Petroleum products such as fuel, oil and grease
l Soil stabilizers and binders (e.g., Polyacrylamide)
l Fertilizers, pesticides and herbicides
l Detergents
l Asphalt and concrete compounds
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l Hazardous chemicals such as acids, lime, adhesives, paints, solvents, and curing compounds
l Any other material that may be detrimental if released to the environment
Design and Installation Specifications
l The temporary storage area should be located away from vehicular traffic, near the con-
struction entrance(s), and away from waterways or storm drains.
l Safety Data Sheets (SDS) should be supplied for all materials stored. Chemicals should be
kept in their original labeled containers.
l Hazardous material storage on-site should be minimized.
l Hazardous materials should be handled as infrequently as possible.
l During the wet weather season (Oct 1 – April 30), consider storing materials in a covered
area.
l Materials should be stored in secondary containments, such as an earthen dike, horse trough,
or even a children’s wading pool for non-reactive materials such as detergents, oil, grease,
and paints. Small amounts of material may be secondarily contained in “bus boy” trays or con-
crete mixing trays.
l Do not store chemicals, drums, or bagged materials directly on the ground. Place these items
on a pallet and, when possible, within secondary containment.
l If drums must be kept uncovered, store them at a slight angle to reduce ponding of rainwater
on the lids to reduce corrosion. Domed plastic covers are inexpensive and snap to the top of
drums, preventing water from collecting.
l Liquids, petroleum products, and substances listed in 40 CFR Parts 110, 117, or 302 shall be
stored in approved containers and drums and shall not be overfilled. Containers and drums
shall be stored in temporary secondary containment facilities.
l Temporary secondary containment facilities shall provide for a spill containment volume able
to contain 10% of the total enclosed container volume of all containers, or 110% of the capa-
city of the largest container within its boundary, whichever is greater.
l Secondary containment facilities shall be impervious to the materials stored therein for a min-
imum contact time of 72 hours.
l Sufficient separation should be provided between stored containers to allow for spill cleanup
and emergency response access.
l During the wet weather season (Oct 1 – April 30), each secondary containment facility shall
be covered during non-working days, prior to and during rain events.
l Keep material storage areas clean, organized and equipped with an ample supply of appro-
priate spill clean-up material (spill kit).
l The spill kit should include, at a minimum:
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o 1-Water Resistant Nylon Bag
o 3-Oil Absorbent Socks 3”x 4’
o 2-Oil Absorbent Socks 3”x 10’
o 12-Oil Absorbent Pads 17”x19”
o 1-Pair Splash Resistant Goggles
o 3-Pair Nitrile Gloves
o 10-Disposable Bags with Ties
o Instructions
Maintenance Standards
l Secondary containment facilities shall be maintained free of accumulated rainwater and spills.
In the event of spills or leaks, accumulated rainwater and spills shall be collected and placed
into drums. These liquids shall be handled as hazardous waste unless testing determines
them to be non-hazardous.
l Re-stock spill kit materials as needed.
BMP C154: Concrete Washout Area
Purpose
Prevent or reduce the discharge of pollutants from concrete waste to stormwater by conducting
washout off-site, or performing on-site washout in a designated area.
Conditions of Use
Concrete washout areas are implemented on construction projects where:
l Concrete is used as a construction material
l It is not possible to dispose of all concrete wastewater and washout off-site (ready mix plant,
etc.).
l Concrete truck drums are washed on-site.
Note that auxiliary concrete truck components (e.g. chutes and hoses) and small concrete
handling equipment (e.g. hand tools, screeds, shovels, rakes, floats, trowels, and wheel-
barrows) may be washed into formed areas awaiting concrete pour.
At no time shall concrete be washed off into the footprint of an area where an infiltration feature will
be installed.
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Design and Installation Specifications
Implementation
l Perform washout of concrete truck drums at an approved off-site location or in designated con-
crete washout areas only.
l Do not wash out concrete onto non-formed areas, or into storm drains, open ditches, streets,
or streams.
l Wash equipment difficult to move, such as concrete paving machines, in areas that do not dir-
ectly drain to natural or constructed stormwater conveyance or potential infiltration areas.
l Do not allow excess concrete to be dumped on-site, except in designated concrete washout
areas as allowed above.
l Concrete washout areas may be prefabricated concrete washout containers, or self-installed
structures (above-grade or below-grade).
l Prefabricated containers are most resistant to damage and protect against spills and leaks.
Companies may offer delivery service and provide regular maintenance and disposal of solid
and liquid waste.
l If self-installed concrete washout areas are used, below-grade structures are preferred over
above-grade structures because they are less prone to spills and leaks.
l Self-installed above-grade structures should only be used if excavation is not practical.
l Concrete washout areas shall be constructed and maintained in sufficient quantity and size to
contain all liquid and concrete waste generated by washout operations.
Education
l Discuss the concrete management techniques described in this BMP with the ready-mix con-
crete supplier before any deliveries are made.
l Educate employees and subcontractors on the concrete waste management techniques
described in this BMP.
l Arrange for the contractor’s superintendent or Certified Erosion and Sediment Control Lead
(CESCL) to oversee and enforce concrete waste management procedures.
l A sign should be installed adjacent to each concrete washout area to inform concrete equip-
ment operators to utilize the proper facilities.
Contracts
Incorporate requirements for concrete waste management into concrete supplier and subcontractor
agreements.
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Location and Placement
l Locate concrete washout areas at least 50 feet from sensitive areas such as storm drains,
open ditches, water bodies, or wetlands.
l Allow convenient access to the concrete washout area for concrete trucks, preferably near the
area where the concrete is being poured.
l If trucks need to leave a paved area to access the concrete washout area, prevent track-out
with a pad of rock or quarry spalls (see BMP C105: Stabilized Construction Access). These
areas should be far enough away from other construction traffic to reduce the likelihood of acci-
dental damage and spills.
l The number of concrete washout areas you install should depend on the expected demand
for storage capacity.
l On large sites with extensive concrete work, concrete washout areas should be placed in mul-
tiple locations for ease of use by concrete truck drivers.
Concrete Truck Washout Procedures
l Washout of concrete truck drums shall be performed in designated concrete washout areas
only.
l Concrete washout from concrete pumper bins can be washed into concrete pumper trucks
and discharged into designated concrete washout areas or properly disposed of off-site.
Concrete Washout Area Installation
l Concrete washout areas should be constructed as shown in the figures below, with a recom-
mended minimum length and minimum width of 10 ft, but with sufficient quantity and volume to
contain all liquid and concrete waste generated by washout operations.
l Plastic lining material should be a minimum of 10 mil polyethylene sheeting and should be free
of holes, tears, or other defects that compromise the impermeability of the material.
l Lath and flagging should be commercial type.
l Liner seams shall be installed in accordance with manufacturers’ recommendations.
l Soil base shall be prepared free of rocks or other debris that may cause tears or holes in the
plastic lining material.
Maintenance Standards
Inspection and Maintenance
l Inspect and verify that concrete washout areas are in place prior to the commencement of con-
crete work.
l Once concrete wastes are washed into the designated washout area and allowed to harden,
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the concrete should be broken up, removed, and disposed of per applicable solid waste reg-
ulations. Dispose of hardened concrete on a regular basis.
l During periods of concrete work, inspect the concrete washout areas daily to verify continued
performance.
o Check overall condition and performance.
o Check remaining capacity (% full).
o If using self-installed concrete washout areas, verify plastic liners are intact and side-
walls are not damaged.
o If using prefabricated containers, check for leaks.
l Maintain the concrete washout areas to provide adequate holding capacity with a minimum
freeboard of 12 inches.
l Concrete washout areas must be cleaned, or new concrete washout areas must be con-
structed and ready for use once the concrete washout area is 75% full.
l If the concrete washout area is nearing capacity, vacuum and dispose of the waste material in
an approved manner.
l Do not discharge liquid or slurry to waterways, storm drains or directly onto ground.
l Do not discharge to the sanitary sewer without local approval.
l Place a secure, non-collapsing, non-water collecting cover over the concrete washout
area prior to predicted wet weather to prevent accumulation and overflow of pre-
cipitation.
l Remove and dispose of hardened concrete and return the structure to a functional con-
dition. Concrete may be reused on-site or hauled away for disposal or recycling.
l When you remove materials from a self-installed concrete washout area, build a new struc-
ture; or, if the previous structure is still intact, inspect for signs of weakening or damage, and
make any necessary repairs. Re-line the structure with new plastic after each cleaning.
Removal of Concrete Washout Areas
l When concrete washout areas are no longer required for the work, the hardened concrete,
slurries and liquids shall be removed and properly disposed of.
l Materials used to construct concrete washout areas shall be removed from the site of the work
and disposed of or recycled.
l Holes, depressions or other ground disturbance caused by the removal of the concrete
washout areas shall be backfilled, repaired, and stabilized to prevent erosion.
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Figure II-3.7: Concrete Washout Area with Wood Planks
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Figure II-3.8: Concrete Washout Area with Straw Bales
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Figure II-3.9: Prefabricated Concrete Washout Container w/Ramp
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Conditions of Use
The construction sequence schedule is an orderly listing of all major land-disturbing activities
together with the necessary erosion and sedimentation control measures planned for the project.
This type of schedule guides the contractor on work to be done before other work is started so that
serious erosion and sedimentation problems can be avoided.
Following a specified work schedule that coordinates the timing of land-disturbing activities and the
installation of control measures is perhaps the most cost-effective way of controlling erosion during
construction. The removal of ground cover leaves a site vulnerable to erosion. Construction sequen-
cing that limits land clearing, provides timely installation of erosion and sedimentation controls, and
restores protective cover quickly can significantly reduce the erosion potential of a site.
Design Considerations
l Minimize construction during rainy periods.
l Schedule projects to disturb only small portions of the site at any one time. Complete grading
as soon as possible. Immediately stabilize the disturbed portion before grading the next por-
tion. Practice staged seeding in order to revegetate cut and fill slopes as the work progresses.
II-3.3 Construction Runoff BMPs
BMP C200: Interceptor Dike and Swale
Purpose
Provide a dike of compacted soil or a swale at the top or base of a disturbed slope or along the peri-
meter of a disturbed construction area to convey stormwater. Use the dike and/or swale to intercept
the runoff from unprotected areas and direct it to areas where erosion can be controlled. This can
prevent storm runoff from entering the work area or sediment-laden runoff from leaving the con-
struction site.
Conditions of Use
Use an interceptor dike or swale where runoff from an exposed site or disturbed slope must be con-
veyed to an erosion control BMP which can safely convey the stormwater.
l Locate upslope of a construction site to prevent runoff from entering the disturbed area.
l When placed horizontally across a disturbed slope, it reduces the amount and velocity of run-
off flowing down the slope.
l Locate downslope to collect runoff from a disturbed area and direct it to a sediment BMP (e.g.
BMP C240: Sediment Trap or BMP C241: Sediment Pond (Temporary)).
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Design and Installation Specifications
l Dike and/or swale and channel must be stabilized with temporary or permanent vegetation or
other channel protection during construction.
l Steep grades require channel protection and check dams.
l Review construction for areas where overtopping may occur.
l Can be used at the top of new fill before vegetation is established.
l May be used as a permanent diversion channel to carry the runoff.
l Contributing area for an individual dike or swale should be one acre or less.
l Design the dike and/or swale to contain flows calculated by one of the following methods:
o Single Event Hydrograph Method: The peak volumetric flow rate calculated using a 10-
minute time step from a Type 1A, 10-year, 24-hour frequency storm for the worst-case
land cover condition.
OR
o Continuous Simulation Method: The 10-year peak flow rate, as determined by an
approved continuous runoff model with a 15-minute time step for the worst-case land
cover condition.
Worst-case land cover conditions (i.e., producing the most runoff) should be used for analysis
(in most cases, this would be the land cover conditions just prior to final landscaping).
Interceptor Dikes
Interceptor dikes shall meet the following criteria:
l Top Width: 2 feet minimum.
l Height: 1.5 feet minimum on berm.
l Side Slope: 2H:1V or flatter.
l Grade: Depends on topography, however, dike system minimum is 0.5%, and maximum is
1%.
l Compaction: Minimum of 90 percent ASTM D698 standard proctor.
l Stabilization: Depends on velocity and reach. Inspect regularly to ensure stability.
l Ground Slopes <5%: Seed and mulch applied within 5 days of dike construction (see BMP
C121: Mulching).
l Ground Slopes 5 - 40%: Dependent on runoff velocities and dike materials. Stabilization
should be done immediately using either sod or riprap, or other measures to avoid erosion.
l The upslope side of the dike shall provide positive drainage to the dike outlet. No erosion shall
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occur at the outlet. Provide energy dissipation measures as necessary. Sediment-laden runoff
must be released through a sediment trapping facility.
l Minimize construction traffic over temporary dikes. Use temporary cross culverts for channel
crossing.
l See Table II-3.8: Horizontal Spacing of Interceptor Dikes Along Ground Slope for recom-
mended horizontal spacing between dikes.
Average Slope Slope Percent Flowpath Length
20H:1V or less 3-5%300 feet
(10 to 20)H:1V 5-10%200 feet
(4 to 10)H:1V 10-25%100 feet
(2 to 4)H:1V 25-50%50 feet
Table II-3.8: Horizontal Spacing of
Interceptor Dikes Along Ground
Slope
Interceptor Swales
Interceptor swales shall meet the following criteria:
l Bottom Width: 2 feet minimum; the cross-section bottom shall be level.
l Depth: 1-foot minimum.
l Side Slope: 2H:1V or flatter.
l Grade: Maximum 5 percent, with positive drainage to a suitable outlet (such as BMP C241:
Sediment Pond (Temporary)).
l Stabilization: Seed as per BMP C120: Temporary and Permanent Seeding, or BMP C202:
Riprap Channel Lining, 12 inches thick riprap pressed into the bank and extending at least 8
inches vertical from the bottom.
Maintenance Standards
l Inspect diversion dikes and interceptor swales once a week and after every rainfall. Imme-
diately remove sediment from the flow area.
l Damage caused by construction traffic or other activity must be repaired before the end of
each working day.
l Check outlets and make timely repairs as needed to avoid gully formation. When the area
below the temporary diversion dike is permanently stabilized, remove the dike and fill and sta-
bilize the channel to blend with the natural surface.
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BMP C207: Check Dams
Purpose
Construction of check dams across a swale or ditch reduces the velocity of concentrated flow and dis-
sipates energy at the check dam.
Conditions of Use
Use check dams where temporary or permanent channels are not yet vegetated, channel lining is
infeasible, and/or velocity checks are required.
l Check dams may not be placed in streams unless approved by the State Department of Fish
and Wildlife.
l Check dams may not be placed in wetlands without approval from a permitting agency.
l Do not place check dams below the expected backwater from any salmonid bearing water
between October 1 and May 31 to ensure that there is no loss of high flow refuge habitat for
overwintering juvenile salmonids and emergent salmonid fry.
Design and Installation Specifications
l Construct rock check dams from appropriately sized rock. The rock used must be large
enough to stay in place given the expected design flow through the channel. The rock must be
placed by hand or by mechanical means (do not dump the rock to form the dam) to achieve
complete coverage of the ditch or swale and to ensure that the center of the dam is lower than
the edges.
l Check dams may also be constructed of either rock or pea-gravel filled bags. Numerous new
products are also available for this purpose. They tend to be re-usable, quick and easy to
install, effective, and cost efficient.
l Place check dams perpendicular to the flow of water.
l The check dam should form a triangle when viewed from the side. This prevents undercutting
as water flows over the face of the check dam rather than falling directly onto the ditch bottom.
l Before installing check dams, impound and bypass upstream water flow away from the work
area. Options for bypassing include pumps, siphons, or temporary channels.
l Check dams combined with sumps work more effectively at slowing flow and retaining sed-
iment than a check dam alone. A deep sump should be provided immediately upstream of the
check dam.
l In some cases, if carefully located and designed, check dams can remain as permanent install-
ations with very minor regrading. They may be left as either spillways, in which case accu-
mulated sediment would be graded and seeded, or as check dams to prevent further
sediment from leaving the site.
l The maximum spacing between check dams shall be such that the downstream toe of the
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upstream dam is at the same elevation as the top of the downstream dam.
l Keep the maximum height at 2 feet at the center of the check dam.
l Keep the center of the check dam at least 12 inches lower than the outer edges at natural
ground elevation.
l Keep the side slopes of the check dam at 2H:1V or flatter.
l Key the stone into the ditch banks and extend it beyond the abutments a minimum of 18
inches to avoid washouts from overflow around the dam.
l Use filter fabric foundation under a rock or sand bag check dam. If a blanket ditch liner is used,
filter fabric is not necessary. A piece of organic or synthetic blanket cut to fit will also work for
this purpose.
l In the case of grass-lined ditches and swales, all check dams and accumulated sediment shall
be removed when the grass has matured sufficiently to protect the ditch or swale - unless the
slope of the swale is greater than 4 percent. The area beneath the check dams shall be
seeded and mulched immediately after dam removal.
l Ensure that channel appurtenances, such as culvert entrances below check dams, are not
subject to damage or blockage from displaced stones.
l See Figure II-3.16: Rock Check Dam.
Maintenance Standards
Check dams shall be monitored for performance and sediment accumulation during and after each
rainfall that produces runoff. Sediment shall be removed when it reaches one half the sump depth.
l Anticipate submergence and deposition above the check dam and erosion from high flows
around the edges of the dam.
l If significant erosion occurs between dams, install a protective riprap liner in that portion of the
channel. See BMP C202: Riprap Channel Lining.
Approved as Functionally Equivalent
Ecology has approved products as able to meet the requirements of this BMP. The products did not
pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions
may choose not to accept these products, or may require additional testing prior to consideration for
local use. Products that Ecology has approved as functionally equivalent are available for review on
Ecology’s website at:
https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per-
mittee-guidance-resources/Emerging-stormwater-treatment-technologies
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Figure II-3.16: Rock Check Dam
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and staples.
o In the case of grass-lined ditches and swales, check dams and accumulated sediment
shall be removed when the grass has matured sufficiently to protect the ditch or swale
unless the slope of the swale is greater than 4 percent. The area beneath the check
dams shall be seeded and mulched immediately after dam removal.
Maintenance Standards
l Inspect TSDs for performance and sediment accumulation during and after each rainfall that
produces runoff. Remove sediment when it reaches one half the height of the TSD.
l Anticipate submergence and deposition above the TSD and erosion from high flows around
the edges of the TSD. Immediately repair any damage or any undercutting of the TSD.
BMP C209: Outlet Protection
Purpose
Outlet protection prevents scour at conveyance outlets and minimizes the potential for downstream
erosion by reducing the velocity of concentrated stormwater flows.
Conditions of Use
Use outlet protection at the outlets of all ponds, pipes, ditches, or other conveyances that discharge
to a natural or manmade drainage feature such as a stream, wetland, lake, or ditch.
Design and Installation Specifications
l The receiving channel at the outlet of a pipe shall be protected from erosion by lining a min-
imum of 6 feet downstream and extending up the channel sides a minimum of 1–foot above
the maximum tailwater elevation, or 1-foot above the crown, whichever is higher. For pipes lar-
ger than 18 inches in diameter, the outlet protection lining of the channel shall be four times
the diameter of the outlet pipe.
l Standard wingwalls, tapered outlets, and paved channels should also be considered when
appropriate for permanent culvert outlet protection (WSDOT, 2015).
l BMP C122: Nets and Blankets or BMP C202: Riprap Channel Lining provide suitable options
for lining materials.
l With low flows, BMP C201: Grass-Lined Channels can be an effective alternative for lining
material.
l The following guidelines shall be used for outlet protection with riprap:
o If the discharge velocity at the outlet is less than 5 fps, use 2-inch to 8-inch riprap. Min-
imum thickness is 1-foot.
o For 5 to 10 fps discharge velocity at the outlet, use 24-inch to 48-inch riprap. Minimum
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thickness is 2 feet.
o For outlets at the base of steep slope pipes (pipe slope greater than 10 percent), use an
engineered energy dissipator.
o Filter fabric or erosion control blankets should always be used under riprap to prevent
scour and channel erosion. See BMP C122: Nets and Blankets.
l Bank stabilization, bioengineering, and habitat features may be required for disturbed areas.
This work may require a Hydraulic Project Approval (HPA) from the Washington State Depart-
ment of Fish and Wildlife. See I-2.11 Hydraulic Project Approvals.
Maintenance Standards
l Inspect and repair as needed.
l Add rock as needed to maintain the intended function.
l Clean energy dissipator if sediment builds up.
BMP C220: Inlet Protection
Purpose
Inlet protection prevents coarse sediment from entering drainage systems prior to permanent sta-
bilization of the disturbed area.
Conditions of Use
Use inlet protection at inlets that are operational before permanent stabilization of the disturbed
areas that contribute runoff to the inlet. Provide protection for all storm drain inlets downslope and
within 500 feet of a disturbed or construction area, unless those inlets are preceded by a sediment
trapping BMP.
Also consider inlet protection for lawn and yard drains on new home construction. These small and
numerous drains coupled with lack of gutters can add significant amounts of sediment into the roof
drain system. If possible, delay installing lawn and yard drains until just before landscaping, or cap
these drains to prevent sediment from entering the system until completion of landscaping. Provide
18-inches of sod around each finished lawn and yard drain.
Table II-3.10: Storm Drain Inlet Protection lists several options for inlet protection. All of the methods
for inlet protection tend to plug and require a high frequency of maintenance. Limit contributing drain-
age areas for an individual inlet to one acre or less. If possible, provide emergency overflows with
additional end-of-pipe treatment where stormwater ponding would cause a hazard.
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Type of Inlet Pro-
tection
Emergency
Overflow
Applicable for
Paved/ Earthen Sur-
faces
Conditions of Use
Drop Inlet Protection
Excavated drop
inlet protection
Yes, temporary
flooding may
occur
Earthen
Applicable for heavy flows. Easy
to maintain. Large area requirement:
30'x30'/acre
Block and gravel
drop inlet pro-
tection
Yes Paved or Earthen Applicable for heavy concentrated flows.
Will not pond.
Gravel and wire
drop inlet pro-
tection
No Paved or Earthen Applicable for heavy concentrated flows.
Will pond. Can withstand traffic.
Catch basin filters Yes Paved or Earthen Frequent maintenance required.
Curb Inlet Protection
Curb inlet pro-
tection with
wooden weir
Small capacity
overflow Paved Used for sturdy, more compact install-
ation.
Block and gravel
curb inlet pro-
tection
Yes Paved Sturdy, but limited filtration.
Culvert Inlet Protection
Culvert inlet sed-
iment trap N/A N/A 18 month expected life.
Table II-3.10: Storm Drain Inlet Protection
Design and Installation Specifications
Excavated Drop Inlet Protection
Excavated drop inlet protection consists of an excavated impoundment around the storm drain inlet.
Sediment settles out of the stormwater prior to entering the storm drain. Design and installation spe-
cifications for excavated drop inlet protection include:
l Provide a depth of 1-2 ft as measured from the crest of the inlet structure.
l Slope sides of excavation should be no steeper than 2H:1V.
l Minimum volume of excavation is 35 cubic yards.
l Shape the excavation to fit the site, with the longest dimension oriented toward the longest
inflow area.
l Install provisions for draining to prevent standing water.
l Clear the area of all debris.
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l Grade the approach to the inlet uniformly.
l Drill weep holes into the side of the inlet.
l Protect weep holes with screen wire and washed aggregate.
l Seal weep holes when removing structure and stabilizing area.
l Build a temporary dike, if necessary, to the down slope side of the structure to prevent bypass
flow.
Block and Gravel Filter
A block and gravel filter is a barrier formed around the inlet with standard concrete blocks and gravel.
See Figure II-3.17: Block and Gravel Filter. Design and installation specifications for block gravel fil-
ters include:
l Provide a height of 1 to 2 feet above the inlet.
l Recess the first row of blocks 2-inches into the ground for stability.
l Support subsequent courses by placing a pressure treated wood 2x4 through the block open-
ing.
l Do not use mortar.
l Lay some blocks in the bottom row on their side to allow for dewatering the pool.
l Place hardware cloth or comparable wire mesh with ½-inch openings over all block openings.
l Place gravel to just below the top of blocks on slopes of 2H:1V or flatter.
l An alternative design is a gravel berm surrounding the inlet, as follows:
o Provide a slope of 3H:1V on the upstream side of the berm.
o Provide a slope of 2H:1V on the downstream side of the berm.
o Provide a 1-foot wide level stone area between the gravel berm and the inlet.
o Use stones 3 inches in diameter or larger on the upstream slope of the berm.
o Use gravel ½- to ¾-inch at a minimum thickness of 1-foot on the downstream slope of
the berm.
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Figure II-3.17: Block and Gravel Filter
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Gravel and Wire Mesh Filter
Gravel and wire mesh filters are gravel barriers placed over the top of the inlet. This method does not
provide an overflow. Design and installation specifications for gravel and wire mesh filters include:
l Use a hardware cloth or comparable wire mesh with ½-inch openings.
o Place wire mesh over the drop inlet so that the wire extends a minimum of 1-foot bey-
ond each side of the inlet structure.
o Overlap the strips if more than one strip of mesh is necessary.
l Place coarse aggregate over the wire mesh.
o Provide at least a 12-inch depth of aggregate over the entire inlet opening and extend at
least 18-inches on all sides.
Catch Basin Filters
Catch basin filters are designed by manufacturers for construction sites. The limited sediment stor-
age capacity increases the amount of inspection and maintenance required, which may be daily for
heavy sediment loads. To reduce maintenance requirements, combine a catch basin filter with
another type of inlet protection. This type of inlet protection provides flow bypass without overflow
and therefore may be a better method for inlets located along active rights-of-way. Design and install-
ation specifications for catch basin filters include:
l Provides 5 cubic feet of storage.
l Requires dewatering provisions.
l Provides a high-flow bypass that will not clog under normal use at a construction site.
l Insert the catch basin filter in the catch basin just below the grating.
Curb Inlet Protection with Wooden Weir
Curb inlet protection with wooden weir is an option that consists of a barrier formed around a curb
inlet with a wooden frame and gravel. Design and installation specifications for curb inlet protection
with wooden weirs include:
l Use wire mesh with ½-inch openings.
l Use extra strength filter cloth.
l Construct a frame.
l Attach the wire and filter fabric to the frame.
l Pile coarse washed aggregate against the wire and fabric.
l Place weight on the frame anchors.
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Block and Gravel Curb Inlet Protection
Block and gravel curb inlet protection is a barrier formed around a curb inlet with concrete blocks and
gravel. See Figure II-3.18: Block and Gravel Curb Inlet Protection. Design and installation spe-
cifications for block and gravel curb inlet protection include:
l Use wire mesh with ½-inch openings.
l Place two concrete blocks on their sides abutting the curb at either side of the inlet opening.
These are spacer blocks.
l Place a 2x4 stud through the outer holes of each spacer block to align the front blocks.
l Place blocks on their sides across the front of the inlet and abutting the spacer blocks.
l Place wire mesh over the outside vertical face.
l Pile coarse aggregate against the wire to the top of the barrier.
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Figure II-3.18: Block and Gravel Curb Inlet Protection
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Curb and Gutter Sediment Barrier
Curb and gutter sediment barrier is a sandbag or rock berm (riprap and aggregate) 3 feet high and 3
feet wide in a horseshoe shape. See Figure II-3.19: Curb and Gutter Barrier. Design and installation
specifications for curb and gutter sediment barrier include:
l Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 feet high
and 3 feet wide, at least 2 feet from the inlet.
l Construct a horseshoe shaped sedimentation trap on the upstream side of the berm. Size the
trap to sediment trap standards for protecting a culvert inlet.
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Figure II-3.19: Curb and Gutter Barrier
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Maintenance Standards
l Inspect all forms of inlet protection frequently, especially after storm events. Clean and
replace clogged catch basin filters. For rock and gravel filters, pull away the rocks from the
inlet and clean or replace. An alternative approach would be to use the clogged rock as fill and
put fresh rock around the inlet.
l Do not wash sediment into storm drains while cleaning. Spread all excavated material evenly
over the surrounding land area or stockpile and stabilize as appropriate.
Approved as Functionally Equivalent
Ecology has approved products as able to meet the requirements of this BMP. The products did not
pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions
may choose not to accept these products, or may require additional testing prior to consideration for
local use. Products that Ecology has approved as functionally equivalent are available for review on
Ecology’s website at:
https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per-
mittee-guidance-resources/Emerging-stormwater-treatment-technologies
BMP C231: Brush Barrier
Purpose
The purpose of brush barriers is to reduce the transport of coarse sediment from a construction site
by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland
flow.
Conditions of Use
l Brush barriers may be used downslope of disturbed areas that are less than one-quarter acre.
l Brush barriers are not intended to treat concentrated flows, nor are they intended to treat sub-
stantial amounts of overland flow. Any concentrated flows must be directed to a sediment trap-
ping BMP. The only circumstance in which overland flow can be treated solely by a brush
barrier, rather than by a sediment trapping BMP, is when the area draining to the barrier is
small.
l Brush barriers should only be installed on contours.
Design and Installation Specifications
l Height: 2 feet (minimum) to 5 feet (maximum).
l Width: 5 feet at base (minimum) to 15 feet (maximum).
l Filter fabric (geotextile) may be anchored over the brush berm to enhance the filtration ability
of the barrier. Ten-ounce burlap is an adequate alternative to filter fabric.
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BMP C233: Silt Fence
Purpose
Silt fence reduces the transport of coarse sediment from a construction site by providing a temporary
physical barrier to sediment and reducing the runoff velocities of overland flow.
Conditions of Use
Silt fence may be used downslope of all disturbed areas.
l Silt fence shall prevent sediment carried by runoff from going beneath, through, or over the
top of the silt fence, but shall allow the water to pass through the fence.
l Silt fence is not intended to treat concentrated flows, nor is it intended to treat substantial
amounts of overland flow. Convey any concentrated flows through the drainage system to a
sediment trapping BMP.
l Do not construct silt fences in streams or use in V-shaped ditches. Silt fences do not provide
an adequate method of silt control for anything deeper than sheet or overland flow.
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Figure II-3.22: Silt Fence
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Design and Installation Specifications
l Use in combination with other construction stormwater BMPs.
l Maximum slope steepness (perpendicular to the silt fence line) 1H:1V.
l Maximum sheet or overland flow path length to the silt fence of 100 feet.
l Do not allow flows greater than 0.5 cfs.
l Use geotextile fabric that meets the following standards. All geotextile properties listed below
are minimum average roll values (i.e., the test result for any sampled roll in a lot shall meet or
exceed the values shown in Table II-3.11: Geotextile Fabric Standards for Silt Fence):
Geotextile Property Minimum Average Roll Value
Polymeric Mesh AOS
(ASTM D4751)
0.60 mm maximum for slit film woven (#30 sieve).
0.30 mm maximum for all other geotextile types (#50 sieve).
0.15 mm minimum for all fabric types (#100 sieve).
Water Permittivity
(ASTM D4491)
0.02 sec-1 minimum
Grab Tensile Strength
(ASTM D4632)
180 lbs. Minimum for extra strength fabric.
100 lbs minimum for standard strength fabric.
Grab Tensile Strength
(ASTM D4632)
30% maximum
Ultraviolet Resistance
(ASTM D4355)
70% minimum
Table II-3.11: Geotextile Fabric Standards for Silt Fence
l Support standard strength geotextiles with wire mesh, chicken wire, 2-inch x 2-inch wire,
safety fence, or jute mesh to increase the strength of the geotextile. Silt fence materials are
available that have synthetic mesh backing attached.
l Silt fence material shall contain ultraviolet ray inhibitors and stabilizers to provide a minimum
of six months of expected usable construction life at a temperature range of 0°F to 120°F.
l One-hundred percent biodegradable silt fence is available that is strong, long lasting, and can
be left in place after the project is completed, if permitted by the local jurisdiction.
l Refer to Figure II-3.22: Silt Fence for standard silt fence details. Include the following Stand-
ard Notes for silt fence on construction plans and specifications:
1. The Contractor shall install and maintain temporary silt fences at the locations shown in
the Plans.
2. Construct silt fences in areas of clearing, grading, or drainage prior to starting those
activities.
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3. The silt fence shall have a 2-feet min. and a 2½-feet max. height above the original
ground surface.
4. The geotextile fabric shall be sewn together at the point of manufacture to form fabric
lengths as required. Locate all sewn seams at support posts. Alternatively, two sections
of silt fence can be overlapped, provided that the overlap is long enough and that the
adjacent silt fence sections are close enough together to prevent silt laden water from
escaping through the fence at the overlap.
5. Attach the geotextile fabric on the up-slope side of the posts and secure with staples,
wire, or in accordance with the manufacturer's recommendations. Attach the geotextile
fabric to the posts in a manner that reduces the potential for tearing.
6. Support the geotextile fabric with wire or plastic mesh, dependent on the properties of
the geotextile selected for use. If wire or plastic mesh is used, fasten the mesh securely
to the up-slope side of the posts with the geotextile fabric up-slope of the mesh.
7. Mesh support, if used, shall consist of steel wire with a maximum mesh spacing of 2-
inches, or a prefabricated polymeric mesh. The strength of the wire or polymeric mesh
shall be equivalent to or greater than 180 lbs. grab tensile strength. The polymeric mesh
must be as resistant to the same level of ultraviolet radiation as the geotextile fabric it
supports.
8. Bury the bottom of the geotextile fabric 4-inches min. below the ground surface. Backfill
and tamp soil in place over the buried portion of the geotextile fabric, so that no flow can
pass beneath the silt fence and scouring cannot occur. When wire or polymeric back-up
support mesh is used, the wire or polymeric mesh shall extend into the ground 3-inches
min.
9. Drive or place the silt fence posts into the ground 18-inches min. A 12–inch min. depth
is allowed if topsoil or other soft subgrade soil is not present and 18-inches cannot be
reached. Increase fence post min. depths by 6 inches if the fence is located on slopes of
3H:1V or steeper and the slope is perpendicular to the fence. If required post depths
cannot be obtained, the posts shall be adequately secured by bracing or guying to pre-
vent overturning of the fence due to sediment loading.
10. Use wood, steel or equivalent posts. The spacing of the support posts shall be a max-
imum of 6-feet. Posts shall consist of either:
l Wood with minimum dimensions of 2 inches by 2 inches by 3 feet. Wood shall be
free of defects such as knots, splits, or gouges.
l No. 6 steel rebar or larger.
l ASTM A 120 steel pipe with a minimum diameter of 1-inch.
l U, T, L, or C shape steel posts with a minimum weight of 1.35 lbs./ft.
l Other steel posts having equivalent strength and bending resistance to the post
sizes listed above.
11. Locate silt fences on contour as much as possible, except at the ends of the fence,
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where the fence shall be turned uphill such that the silt fence captures the runoff water
and prevents water from flowing around the end of the fence.
12. If the fence must cross contours, with the exception of the ends of the fence, place
check dams perpendicular to the back of the fence to minimize concentrated flow and
erosion. The slope of the fence line where contours must be crossed shall not be
steeper than 3H:1V.
l Check dams shall be approximately 1-foot deep at the back of the fence. Check
dams shall be continued perpendicular to the fence at the same elevation until
the top of the check dam intercepts the ground surface behind the fence.
l Check dams shall consist of crushed surfacing base course, gravel backfill for
walls, or shoulder ballast. Check dams shall be located every 10 feet along the
fence where the fence must cross contours.
l Refer to Figure II-3.23: Silt Fence Installation by Slicing Method for slicing method details. The
following are specifications for silt fence installation using the slicing method:
1. The base of both end posts must be at least 2- to 4-inches above the top of the geo-
textile fabric on the middle posts for ditch checks to drain properly. Use a hand level or
string level, if necessary, to mark base points before installation.
2. Install posts 3- to 4-feet apart in critical retention areas and 6- to 7-feet apart in standard
applications.
3. Install posts 24-inches deep on the downstream side of the silt fence, and as close as
possible to the geotextile fabric, enabling posts to support the geotextile fabric from
upstream water pressure.
4. Install posts with the nipples facing away from the geotextile fabric.
5. Attach the geotextile fabric to each post with three ties, all spaced within the top 8-
inches of the fabric. Attach each tie diagonally 45 degrees through the fabric, with each
puncture at least 1-inch vertically apart. Each tie should be positioned to hang on a post
nipple when tightening to prevent sagging.
6. Wrap approximately 6-inches of the geotextile fabric around the end posts and secure
with 3 ties.
7. No more than 24-inches of a 36-inch geotextile fabric is allowed above ground level.
8. Compact the soil immediately next to the geotextile fabric with the front wheel of the
tractor, skid steer, or roller exerting at least 60 pounds per square inch. Compact the
upstream side first and then each side twice for a total of four trips. Check and correct
the silt fence installation for any deviation before compaction. Use a flat-bladed shovel
to tuck the fabric deeper into the ground if necessary.
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Figure II-3.23: Silt Fence Installation by Slicing Method
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Maintenance Standards
l Repair any damage immediately.
l Intercept and convey all evident concentrated flows uphill of the silt fence to a sediment trap-
ping BMP.
l Check the uphill side of the silt fence for signs of the fence clogging and acting as a barrier to
flow and then causing channelization of flows parallel to the fence. If this occurs, replace the
fence and remove the trapped sediment.
l Remove sediment deposits when the deposit reaches approximately one-third the height of
the silt fence, or install a second silt fence.
l Replace geotextile fabric that has deteriorated due to ultraviolet breakdown.
BMP C234: Vegetated Strip
Purpose
Vegetated strips reduce the transport of coarse sediment from a construction site by providing a
physical barrier to sediment and reducing the runoff velocities of overland flow.
Conditions of Use
l Vegetated strips may be used downslope of all disturbed areas.
l Vegetated strips are not intended to treat concentrated flows, nor are they intended to treat
substantial amounts of overland flow. Any concentrated flows must be conveyed through the
drainage system to BMP C241: Sediment Pond (Temporary) or other sediment trapping
BMP. The only circumstance in which overland flow can be treated solely by a vegetated strip,
rather than by a sediment trapping BMP, is when the following criteria are met (see Table II-
3.12: Contributing Drainage Area for Vegetated Strips):
Average Contributing Area
Slope
Average Contributing Area Per-
cent Slope
Max Contributing area Flowpath
Length
1.5H : 1V or flatter 67% or flatter 100 feet
2H : 1V or flatter 50% or flatter 115 feet
4H : 1V or flatter 25% or flatter 150 feet
6H : 1V or flatter 16.7% or flatter 200 feet
10H : 1V or flatter 10% or flatter 250 feet
Table II-3.12: Contributing Drainage Area for Vegetated Strips
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 376
Design and Installation Specifications
l The vegetated strip shall consist of a continuous strip of dense vegetation with topsoil for a min-
imum of a 25-foot length along the flowpath. Grass-covered, landscaped areas are generally
not adequate because the volume of sediment overwhelms the grass. Ideally, vegetated strips
shall consist of undisturbed native growth with a well-developed soil that allows for infiltration
of runoff.
l The slope within the vegetated strip shall not exceed 4H:1V.
l The uphill boundary of the vegetated strip shall be delineated with clearing limits.
Maintenance Standards
l Any areas damaged by erosion or construction activity shall be seeded immediately and pro-
tected by mulch.
l If more than 5 feet of the original vegetated strip width has had vegetation removed or is being
eroded, sod must be installed.
l If there are indications that concentrated flows are traveling across the vegetated strip, storm-
water runoff controls must be installed to reduce the flows entering the vegetated strip, or addi-
tional perimeter protection must be installed.
BMP C235: Wattles
Purpose
Wattles are temporary erosion and sediment control barriers consisting of straw, compost, or other
material that is wrapped in netting made of natural plant fiber or similar encasing material. They
reduce the velocity and can spread the flow of rill and sheet runoff, and can capture and retain sed-
iment.
Conditions of Use
l Wattles shall consist of cylinders of plant material such as weed-free straw, coir, wood chips,
excelsior, or wood fiber or shavings encased within netting made of natural plant fibers
unaltered by synthetic materials.
l Use wattles:
o In disturbed areas that require immediate erosion protection.
o On exposed soils during the period of short construction delays, or over winter months.
o On slopes requiring stabilization until permanent vegetation can be established.
l The material used dictates the effectiveness period of the wattle. Generally, wattles are effect-
ive for one to two seasons.
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 377
l Prevent rilling beneath wattles by entrenching and overlapping wattles to prevent water from
passing between them.
Design Criteria
l See Figure II-3.24: Wattles for typical construction details.
l Wattles are typically 8 to 10 inches in diameter and 25 to 30 feet in length.
l Install wattles perpendicular to the flow direction and parallel to the slope contour.
l Place wattles in shallow trenches, staked along the contour of disturbed or newly constructed
slopes. Dig narrow trenches across the slope (on contour) to a depth of 3- to 5-inches on clay
soils and soils with gradual slopes. On loose soils, steep slopes, and areas with high rainfall,
the trenches should be dug to a depth of 5- to 7- inches, or 1/2 to 2/3 of the thickness of the
wattle.
l Start building trenches and installing wattles from the base of the slope and work up. Spread
excavated material evenly along the uphill slope and compact it using hand tamping or other
methods.
l Construct trenches at intervals of 10- to 25-feet depending on the steepness of the slope, soil
type, and rainfall. The steeper the slope the closer together the trenches.
l Install the wattles snugly into the trenches and overlap the ends of adjacent wattles 12 inches
behind one another.
l Install stakes at each end of the wattle, and at 4-foot centers along entire length of wattle.
l If required, install pilot holes for the stakes using a straight bar to drive holes through the wattle
and into the soil.
l Wooden stakes should be approximately 0.75 x 0.75 x 24 inches min. Willow cuttings or 3/8-
inch rebar can also be used for stakes.
l Stakes should be driven through the middle of the wattle, leaving 2 to 3 inches of the stake pro-
truding above the wattle.
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 378
Figure II-3.24: Wattles
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 379
Maintenance Standards
l Wattles may require maintenance to ensure they are in contact with soil and thoroughly
entrenched, especially after significant rainfall on steep sandy soils.
l Inspect the slope after significant storms and repair any areas where wattles are not tightly
abutted or water has scoured beneath the wattles.
Approved as Functionally Equivalent
Ecology has approved products as able to meet the requirements of this BMP. The products did not
pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions
may choose not to accept these products, or may require additional testing prior to consideration for
local use. Products that Ecology has approved as functionally equivalent are available for review on
Ecology’s website at:
https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per-
mittee-guidance-resources/Emerging-stormwater-treatment-technologies
BMP C236: Vegetative Filtration
Purpose
Vegetative filtration as a BMP is used in conjunction with detention storage in the form of portable
tanks or BMP C241: Sediment Pond (Temporary), BMP C206: Level Spreader, and a pumping sys-
tem with surface intake. Vegetative filtration improves turbidity levels of stormwater discharges by fil-
tering runoff through existing vegetation where undisturbed forest floor duff layer or established lawn
with thatch layer are present. Vegetative filtration can also be used to infiltrate dewatering waste
from foundations, vaults, and trenches as long as runoff does not occur.
Conditions of Use
l For every five acres of disturbed soil use one acre of grass field, farm pasture, or wooded
area. Reduce or increase this area depending on project size, ground water table height, and
other site conditions.
l Wetlands shall not be used for vegetative filtration.
l Do not use this BMP in areas with a high ground water table, or in areas that will have a high
seasonal ground water table during the use of this BMP.
l This BMP may be less effective on soils that prevent the infiltration of the water, such as hard
till.
l Using other effective source control measures throughout a construction site will prevent the
generation of additional highly turbid water and may reduce the time period or area need for
this BMP.
l Stop distributing water into the vegetated filtration area if standing water or erosion results.
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 380
Solera Townhomes – New Home Co. Page 35
C. Site Inspection Form
The results of each inspection shall be summarized in an inspection report or checklist
that is entered into or attached to the site log book. It is suggested that the inspection
report or checklist be included in this appendix to keep monitoring and inspection
information in one document, but this is optional. However, it is mandatory that this
SWPPP and the site inspection forms be kept onsite at all times during construction, and
that inspections be performed and documented as outlined below.
At a minimum, each inspection report or checklist shall include:
a. Inspection date/times
b. Weather information: general conditions during inspection, approximate
amount of precipitation since the last inspection, and approximate amount
of precipitation within the last 24 hours.
c. A summary or list of all BMPs that have been implemented, including
observations of all erosion/sediment control structures or practices.
d. The following shall be noted:
i. locations of BMPs inspected,
ii. locations of BMPs that need maintenance,
iii. the reason maintenance is needed,
iv. locations of BMPs that failed to operate as designed or intended, and
v. locations where additional or different BMPs are needed, and the
reason(s) why
e. A description of stormwater discharged from the site. The presence of
suspended sediment, turbid water, discoloration, and/or oil sheen shall be
noted, as applicable.
f. Confirmation of zero stormwater discharge from the site.
g. General comments and notes, including a brief description of any BMP
repairs, maintenance or installations made as a result of the inspection.
h. A statement that, in the judgment of the person conducting the site
inspection, the site is either in compliance or out of compliance with the
terms and conditions of the SWPPP. If the site inspection indicates that
the site is out of compliance, the inspection report shall include a
summary of the remedial actions required to bring the site back into
compliance, as well as a schedule of implementation.
Solera Townhomes – New Home Co. Page 36
i. Name, title, and signature of person conducting the site inspection; and
the following statement: “I certify under penalty of law that this report is
true, accurate, and complete, to the best of my knowledge and belief.”
When the site inspection indicates that the site is not in compliance with any terms and
conditions of the City of Renton, King County, and Ecology requirements, the Permittee
shall take immediate action(s) to: stop, contain, and clean up the unauthorized
discharges, or otherwise stop the noncompliance; correct the problem(s); implement
appropriate Best Management Practices (BMPs), and/or conduct maintenance of
existing BMPs; and achieve compliance with all applicable standards and permit
conditions.
Construction Stormwater Site Inspection Form
Page 1
Project Name Permit # Inspection Date Time
Name of Certified Erosion Sediment Control Lead (CESCL) or qualified inspector if less than one acre
Print Name:
Approximate rainfall amount since the last inspection (in inches):
Approximate rainfall amount in the last 24 hours (in inches):
Current Weather Clear Cloudy Mist Rain Wind Fog
A. Type of inspection: Weekly Post Storm Event Other
B. Phase of Active Construction (check all that apply):
Pre Construction/installation of erosion/sediment
controls
Clearing/Demo/Grading Infrastructure/storm/roads
Concrete pours Vertical
Construction/buildings
Utilities
Offsite improvements Site temporary stabilized Final stabilization
C. Questions:
1. Were all areas of construction and discharge points inspected? Yes No
2. Did you observe the presence of suspended sediment, turbidity, discoloration, or oil sheen Yes No
3. Was a water quality sample taken during inspection? (refer to permit conditions S4 & S5) Yes No
4. Was there a turbid discharge 250 NTU or greater, or Transparency 6 cm or less?* Yes No
5. If yes to #4 was it reported to Ecology? Yes No
6. Is pH sampling required? pH range required is 6.5 to 8.5. Yes No
If answering yes to a discharge, describe the event. Include when, where, and why it happened; what action was taken,
and when.
*If answering yes to # 4 record NTU/Transparency with continual sampling daily until turbidity is 25 NTU or less/ transparency is 33
cm or greater.
Sampling Results: Date:
Parameter Method (circle one) Result Other/Note
NTU cm pH
Turbidity tube, meter, laboratory
pH Paper, kit, meter
Construction Stormwater Site Inspection Form
Page 2
D. Check the observed status of all items. Provide “Action Required “details and dates.
Element # Inspection BMPs
Inspected
BMP needs
maintenance
BMP
failed
Action
required
(describe in
section F)
yes no n/a
1
Clearing
Limits
Before beginning land disturbing
activities are all clearing limits,
natural resource areas (streams,
wetlands, buffers, trees) protected
with barriers or similar BMPs? (high
visibility recommended)
2
Construction
Access
Construction access is stabilized
with quarry spalls or equivalent
BMP to prevent sediment from
being tracked onto roads?
Sediment tracked onto the road
way was cleaned thoroughly at the
end of the day or more frequent as
necessary.
3
Control Flow
Rates
Are flow control measures installed
to control stormwater volumes and
velocity during construction and do
they protect downstream
properties and waterways from
erosion?
If permanent infiltration ponds are
used for flow control during
construction, are they protected
from siltation?
4
Sediment
Controls
All perimeter sediment controls
(e.g. silt fence, wattles, compost
socks, berms, etc.) installed, and
maintained in accordance with the
Stormwater Pollution Prevention
Plan (SWPPP).
Sediment control BMPs (sediment
ponds, traps, filters etc.) have been
constructed and functional as the
first step of grading.
Stormwater runoff from disturbed
areas is directed to sediment
removal BMP.
5
Stabilize
Soils
Have exposed un-worked soils
been stabilized with effective BMP
to prevent erosion and sediment
deposition?
Construction Stormwater Site Inspection Form
Page 3
Element # Inspection BMPs
Inspected
BMP needs
maintenance
BMP
failed
Action
required
(describe in
section F)
yes no n/a
5
Stabilize Soils
Cont.
Are stockpiles stabilized from erosion,
protected with sediment trapping
measures and located away from drain
inlet, waterways, and drainage
channels?
Have soils been stabilized at the end of
the shift, before a holiday or weekend
if needed based on the weather
forecast?
6
Protect
Slopes
Has stormwater and ground water
been diverted away from slopes and
disturbed areas with interceptor dikes,
pipes and or swales?
Is off-site storm water managed
separately from stormwater generated
on the site?
Is excavated material placed on uphill
side of trenches consistent with safety
and space considerations?
Have check dams been placed at
regular intervals within constructed
channels that are cut down a slope?
7
Drain Inlets
Storm drain inlets made operable
during construction are protected.
Are existing storm drains within the
influence of the project protected?
8
Stabilize
Channel and
Outlets
Have all on-site conveyance channels
been designed, constructed and
stabilized to prevent erosion from
expected peak flows?
Is stabilization, including armoring
material, adequate to prevent erosion
of outlets, adjacent stream banks,
slopes and downstream conveyance
systems?
9
Control
Pollutants
Are waste materials and demolition
debris handled and disposed of to
prevent contamination of stormwater?
Has cover been provided for all
chemicals, liquid products, petroleum
products, and other material?
Has secondary containment been
provided capable of containing 110%
of the volume?
Were contaminated surfaces cleaned
immediately after a spill incident?
Were BMPs used to prevent
contamination of stormwater by a pH
modifying sources?
Construction Stormwater Site Inspection Form
Page 4
Element # Inspection BMPs
Inspected
BMP needs
maintenance
BMP
failed
Action
required
(describe in
section F)
yes no n/a
9
Cont.
Wheel wash wastewater is handled
and disposed of properly.
10
Control
Dewatering
Concrete washout in designated areas.
No washout or excess concrete on the
ground.
Dewatering has been done to an
approved source and in compliance
with the SWPPP.
Were there any clean non turbid
dewatering discharges?
11
Maintain
BMP
Are all temporary and permanent
erosion and sediment control BMPs
maintained to perform as intended?
12
Manage the
Project
Has the project been phased to the
maximum degree practicable?
Has regular inspection, monitoring and
maintenance been performed as
required by the permit?
Has the SWPPP been updated,
implemented and records maintained?
13
Protect LID
Is all Bioretention and Rain Garden
Facilities protected from
sedimentation with appropriate BMPs?
Is the Bioretention and Rain Garden
protected against over compaction of
construction equipment and foot
traffic to retain its infiltration
capabilities?
Permeable pavements are clean and
free of sediment and sediment laden-
water runoff. Muddy construction
equipment has not been on the base
material or pavement.
Have soiled permeable pavements
been cleaned of sediments and pass
infiltration test as required by
stormwater manual methodology?
Heavy equipment has been kept off
existing soils under LID facilities to
retain infiltration rate.
E. Check all areas that have been inspected.
All in place BMPs All disturbed soils All concrete wash out area All material storage areas
All discharge locations All equipment storage areas All construction entrances/exits
Construction Stormwater Site Inspection Form
Page 5
F. Elements checked “Action Required” (section D) describe corrective action to be taken. List the element number;
be specific on location and work needed. Document, initial, and date when the corrective action has been completed
and inspected.
Element
#
Description and Location Action Required Completion
Date
Initials
Attach additional page if needed
Sign the following certification:
“I certify that this report is true, accurate, and complete, to the best of my knowledge and belief”
Inspected by: (print) (Signature) Date:
Title/Qualification of Inspector:
Solera Townhomes – New Home Co. Page 37
D. Construction Stormwater General Permit (CSWGP)
Approved CSWGP WAR310291 covers all sites under the approved Master Plan.
June 2, 2021
Tom Neubauer Solera, LLC 10900 NE 8th STE STE 1200
Bellevue, WA 98004-4460 RE: Coverage under the Construction Stormwater General Permit
Permit number: WAR310291
Site Name: Solera Location: NE Sunset Blvd Between NE 10th and NE 12th Renton County: King Disturbed Acres: 13 Dear Tom Neubauer: The Washington State Department of Ecology (Ecology) received your Notice of Intent for
coverage under Ecology’s Construction Stormwater General Permit (CSWGP). This is your permit coverage letter. Your permit coverage is effective June 2, 2021. Retain this letter as an official record of permit coverage for your site. You may keep your records in electronic format if you can easily access them from your construction site. You can
get the CSWGP, permit forms, and other information at www.ecology.wa.gov/eCoverage-packet. Contact your Permit Administrator, listed below, if you want a copy of the CSWGP mailed to you. Please read the permit and contact Ecology if you have any questions.
Electronic Discharge Monitoring Reports (WQWebDMR) This permit requires you to submit monthly discharge monitoring reports (DMRs) for the full
duration of permit coverage (from the first full month of coverage to termination). DMRs must
be submitted electronically using Ecology’s secure online system, WQWebDMR. To sign up for WQWebDMR go to www.ecology.wa.gov/programs/wq/permits/paris/webdmr.html. If you have questions, contact the portal staff at (360) 407-7097 (Olympia area), or (800) 633-6193/option 3,
or email WQWebPortal@ecy.wa.gov.
Tom Neubauer June 2, 2021 Page 2
Appeal Process
You have a right to appeal coverage under the general permit to the Pollution Control Hearing Board (PCHB). Appeals must be filed within 30 days of the date of receipt of this letter. Any appeal is limited to the general permit’s applicability or non-applicability to a specific
discharger. The appeal process is governed by chapter 43.21B RCW and chapter 371-08 WAC.
“Date of receipt” is defined in RCW 43.21B.001(2). For more information regarding your right to appeal, go to https://apps.ecology.wa.gov/publications/summarypages/1710007.html to view Ecology’s Focus Sheet: Appeal of General Permit Coverage.
Ecology Field Inspector Assistance
If you have questions regarding stormwater management at your construction site, please contact
your Regional Inspector, Maria Zeman of Ecology's Northwest Regional Office in Bellevue at Maria.Zeman@ecy.wa.gov, or at 425-649-7100.
Questions or Additional Information Ecology is here to help. Please review our web page at www.ecology.wa.gov/constructionstormwaterpermit. If you have questions about the Construction Stormwater General Permit, please contact your Permit Administrator, Kendra Henderson at kendra.henderson@ecy.wa.gov, or (360) 407-6556.
Sincerely,
Jeff Killelea, Manager Program Development Services Section Water Quality Program
Issuance Date: November 18, 2020
Effective Date: January 1, 2021
Expiration Date: December 31, 2025
CONSTRUCTION STORMWATER
GENERAL PERMIT
National Pollutant Discharge Elimination System (NPDES) and State Waste Discharge
General Permit for Stormwater Discharges Associated with Construction Activity
State of Washington
Department of Ecology
Olympia, Washington 98504
In compliance with the provisions of Chapter 90.48 Revised Code of Washington (State of Washington Water Pollution Control Act) and Title 33 United States Code, Section 1251 et seq. The Federal Water Pollution Control Act (The Clean Water Act)
Until this permit expires, is modified, or revoked, Permittees that have properly obtained coverage under this general permit are authorized to discharge in accordance with the special and general conditions that follow.
__________________________________ Vincent McGowan, P.E. Water Quality Program Manager Washington State Department of Ecology
Construction Stormwater General Permit Page i
TABLE OF CONTENTS
LIST OF TABLES .................................................................................................................................. ii
SUMMARY OF PERMIT REPORT SUBMITTALS ...................................................................................... 1
SPECIAL CONDITIONS ......................................................................................................................... 3
S1. Permit Coverage .............................................................................................................................. 3
S2. Application Requirements ............................................................................................................... 7
S3. Compliance with Standards ............................................................................................................. 9
S4. Monitoring Requirements, Benchmarks, and Reporting Triggers ................................................. 10
S5. Reporting and Recordkeeping Requirements ................................................................................ 17
S6. Permit Fees .................................................................................................................................... 20
S7. Solid and Liquid Waste Disposal .................................................................................................... 20
S8. Discharges to 303(D) or TMDL Waterbodies ................................................................................. 20
S9. Stormwater Pollution Prevention Plan .......................................................................................... 23
S10. Notice Of Termination ................................................................................................................... 32
GENERAL CONDITIONS ..................................................................................................................... 34
G1. Discharge Violations....................................................................................................................... 34
G2. Signatory Requirements ................................................................................................................ 34
G3. Right of Inspection and Entry ......................................................................................................... 35
G4. General Permit Modification and Revocation ............................................................................... 35
G5. Revocation of Coverage Under tPermit ......................................................................................... 35
G6. Reporting a Cause for Modification ............................................................................................... 36
G7. Compliance with Other Laws and Statutes .................................................................................... 36
G8. Duty to Reapply.............................................................................................................................. 36
G9. Removed Substance ....................................................................................................................... 36
G10. Duty to Provide Information .......................................................................................................... 36
G11. Other Requirements of 40 CFR ...................................................................................................... 37
G12. Additional Monitoring .................................................................................................................... 37
G13. Penalties for Violating Permit Conditions ...................................................................................... 37
G14. Upset .............................................................................................................................................. 37
G15. Property Rights .............................................................................................................................. 37
G16. Duty to Comply .............................................................................................................................. 37
G17. Toxic Pollutants .............................................................................................................................. 38
G18. Penalties for Tampering ................................................................................................................. 38
G19. Reporting Planned Changes ........................................................................................................... 38
G20. Reporting Other Information ......................................................................................................... 38
G21. Reporting Anticipated Non-Compliance ........................................................................................ 38
Construction Stormwater General Permit Page ii
G22. Requests to Be Excluded From Coverage Under the Permit ......................................................... 39
G23. Appeals........................................................................................................................................... 39
G24. Severability..................................................................................................................................... 39
G25. Bypass Prohibited .......................................................................................................................... 39
APPENDIX A – DEFINITIONS .............................................................................................................. 42
APPENDIX B – ACRONYMS ................................................................................................................ 50
LIST OF TABLES
Table 1 Summary of Required Submittals ................................................................................................ 1
Table 2 Summary of Required On-site Documentation ........................................................................... 2
Table 3 Summary of Primary Monitoring Requirements ....................................................................... 12
Table 4 Monitoring and Reporting Requirements ................................................................................. 14
Table 5 Turbidity, Fine Sediment & Phosphorus Sampling and Limits for
303(d)-Listed Waters ................................................................................................................ 22
Table 6 pH Sampling and Limits for 303(d)-Listed Waters ..................................................................... 22
Construction Stormwater General Permit Page 1
SUMMARY OF PERMIT REPORT SUBMITTALS
Refer to the Special and General Conditions within this permit for additional submittal requirements.
Appendix A provides a list of definitions. Appendix B provides a list of acronyms.
Table 1 Summary of Required Submittals
Permit Section Submittal Frequency First Submittal Date
S5.A and
S8
High Turbidity/Transparency Phone
Reporting
As Necessary Within 24 hours
S5.B Discharge Monitoring Report Monthly* Within 15 days following the
end of each month
S5.F and S8 Noncompliance Notification – Telephone Notification As necessary Within 24 hours
S5.F Noncompliance Notification – Written
Report
As necessary Within 5 Days of
non-compliance
S9.D Request for Chemical Treatment Form As necessary Written approval from
Ecology is required prior to
using chemical treatment
(with the exception of dry ice,
CO2 or food grade vinegar to
adjust pH)
G2 Notice of Change in Authorization As necessary
G6 Permit Application for Substantive
Changes to the Discharge
As necessary
G8 Application for Permit Renewal 1/permit cycle No later than 180 days
before expiration
S2.A Notice of Permit Transfer As necessary
G19 Notice of Planned Changes As necessary
G21 Reporting Anticipated Non-compliance As necessary
NOTE: *Permittees must submit electronic Discharge Monitoring Reports (DMRs) to the Washington State
Department of Ecology monthly, regardless of site discharge, for the full duration of permit coverage. Refer
to Section S5.B of this General Permit for more specific information regarding DMRs.
Construction Stormwater General Permit Page 2
Table 2 Summary of Required On-site Documentation
Document Title
Permit Conditions
Permit Coverage Letter See Conditions S2, S5
Construction Stormwater General Permit (CSWGP) See Conditions S2, S5
Site Log Book See Conditions S4, S5
Stormwater Pollution Prevention Plan (SWPPP) See Conditions S5, S9
Site Map See Conditions S5, S9
Construction Stormwater General Permit Page 3
SPECIAL CONDITIONS
S1. PERMIT COVERAGE
A. Permit Area
This Construction Stormwater General Permit (CSWGP) covers all areas of Washington State,
except for federal operators and Indian Country as specified in Special Condition S1.E.3 and 4.
B. Operators Required to Seek Coverage Under this General Permit
1. Operators of the following construction activities are required to seek coverage under
this CSWGP:
a. Clearing, grading and/or excavation that results in the disturbance of one or more
acres (including off-site disturbance acreage related to construction-support activity
as authorized in S1.C.2) and discharges stormwater to surface waters of the State;
and clearing, grading and/or excavation on sites smaller than one acre that are part
of a larger common plan of development or sale, if the common plan of
development or sale will ultimately disturb one acre or more and discharge
stormwater to surface waters of the State.
i. This category includes forest practices (including, but not limited to, class IV
conversions) that are part of a construction activity that will result in the
disturbance of one or more acres, and discharge to surface waters of the State
(that is, forest practices that prepare a site for construction activities); and
b. Any size construction activity discharging stormwater to waters of the State that the
Washington State Department of Ecology (Ecology):
i. Determines to be a significant contributor of pollutants to waters of the State
of Washington.
ii. Reasonably expects to cause a violation of any water quality standard.
2. Operators of the following activities are not required to seek coverage under this CSWGP
(unless specifically required under Special Condition S1.B.1.b, above):
a. Construction activities that discharge all stormwater and non-stormwater to
groundwater, sanitary sewer, or combined sewer, and have no point source
discharge to either surface water or a storm sewer system that drains to surface
waters of the State.
b. Construction activities covered under an Erosivity Waiver (Special Condition S1.F).
c. Routine maintenance that is performed to maintain the original line and grade,
hydraulic capacity, or original purpose of a facility.
C. Authorized Discharges
1. Stormwater Associated with Construction Activity. Subject to compliance with the terms
and conditions of this permit, Permittees are authorized to discharge stormwater
associated with construction activity to surface waters of the State or to a storm sewer
system that drains to surface waters of the State. (Note that “surface waters of the
Construction Stormwater General Permit Page 4
State” may exist on a construction site as well as off site; for example, a creek running
through a site.)
2. Stormwater Associated with Construction Support Activity. This permit also authorizes
stormwater discharge from support activities related to the permitted construction site
(for example, an on-site portable rock crusher, off-site equipment staging yards, material
storage areas, borrow areas, etc.) provided:
a. The support activity relates directly to the permitted construction site that is
required to have an NPDES permit; and
b. The support activity is not a commercial operation serving multiple unrelated
construction projects, and does not operate beyond the completion of the
construction activity; and
c. Appropriate controls and measures are identified in the Stormwater Pollution
Prevention Plan (SWPPP) for the discharges from the support activity areas.
3. Non-Stormwater Discharges. The categories and sources of non-stormwater discharges
identified below are authorized conditionally, provided the discharge is consistent with
the terms and conditions of this permit:
a. Discharges from fire-fighting activities.
b. Fire hydrant system flushing.
c. Potable water, including uncontaminated water line flushing.
d. Hydrostatic test water.
e. Uncontaminated air conditioning or compressor condensate.
f. Uncontaminated groundwater or spring water.
g. Uncontaminated excavation dewatering water (in accordance with S9.D.10).
h. Uncontaminated discharges from foundation or footing drains.
i. Uncontaminated or potable water used to control dust. Permittees must minimize
the amount of dust control water used.
j. Routine external building wash down that does not use detergents.
k. Landscape irrigation water.
The SWPPP must adequately address all authorized non-stormwater discharges, except for
discharges from fire-fighting activities, and must comply with Special Condition S3. At a
minimum, discharges from potable water (including water line flushing), fire hydrant system
flushing, and pipeline hydrostatic test water must undergo the following: dechlorination to a
concentration of 0.1 parts per million (ppm) or less, and pH adjustment to within 6.5 – 8.5
standard units (su), if necessary.
D. Prohibited Discharges
The following discharges to waters of the State, including groundwater, are prohibited:
Construction Stormwater General Permit Page 5
1. Concrete wastewater
2. Wastewater from washout and clean-up of stucco, paint, form release oils, curing
compounds and other construction materials.
3. Process wastewater as defined by 40 Code of Federal Regulations (CFR) 122.2 (See
Appendix A of this permit).
4. Slurry materials and waste from shaft drilling, including process wastewater from shaft
drilling for construction of building, road, and bridge foundations unless managed
according to Special Condition S9.D.9.j.
5. Fuels, oils, or other pollutants used in vehicle and equipment operation and
maintenance.
6. Soaps or solvents used in vehicle and equipment washing.
7. Wheel wash wastewater, unless managed according to Special Condition S9.D.9.
8. Discharges from dewatering activities, including discharges from dewatering of trenches
and excavations, unless managed according to Special Condition S9.D.10.
E. Limits on Coverage
Ecology may require any discharger to apply for and obtain coverage under an individual permit
or another more specific general permit. Such alternative coverage will be required when
Ecology determines that this CSWGP does not provide adequate assurance that water quality
will be protected, or there is a reasonable potential for the project to cause or contribute to a
violation of water quality standards.
The following stormwater discharges are not covered by this permit:
1. Post-construction stormwater discharges that originate from the site after completion of
construction activities and the site has undergone final stabilization.
2. Non-point source silvicultural activities such as nursery operations, site preparation,
reforestation and subsequent cultural treatment, thinning, prescribed burning, pest and
fire control, harvesting operations, surface drainage, or road construction and
maintenance, from which there is natural runoff as excluded in 40 CFR Subpart 122.
3. Stormwater from any federal operator.
4. Stormwater from facilities located on Indian Country as defined in 18 U.S.C.§1151,
except portions of the Puyallup Reservation as noted below.
Indian Country includes:
a. All land within any Indian Reservation notwithstanding the issuance of any patent,
and, including rights-of-way running through the reservation. This includes all
federal, tribal, and Indian and non-Indian privately owned land within the
reservation.
b. All off-reservation Indian allotments, the Indian titles to which have not been
extinguished, including rights-of-way running through the same.
c. All off-reservation federal trust lands held for Native American Tribes.
Construction Stormwater General Permit Page 6
Puyallup Exception: Following the Puyallup Tribes of Indians Land Settlement Act of
1989, 25 U.S.C. §1773; the permit does apply to land within the Puyallup
Reservation except for discharges to surface water on land held in trust by the
federal government.
5. Stormwater from any site covered under an existing NPDES individual permit in which
stormwater management and/or treatment requirements are included for all stormwater
discharges associated with construction activity.
6. Stormwater from a site where an applicable Total Maximum Daily Load (TMDL)
requirement specifically precludes or prohibits discharges from construction activity.
F. Erosivity Waiver
Construction site operators may qualify for an Erosivity Waiver from the CSWGP if the following
conditions are met:
1. The site will result in the disturbance of fewer than five (5) acres and the site is not a
portion of a common plan of development or sale that will disturb five (5) acres or
greater.
2. Calculation of Erosivity “R” Factor and Regional Timeframe:
a. The project’s calculated rainfall erosivity factor (“R” Factor) must be less than five
(5) during the period of construction activity, (See the CSWGP homepage
http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html for a
link to the EPA’s calculator and step by step instructions on computing the “R”
Factor in the EPA Erosivity Waiver Fact Sheet). The period of construction activity
starts when the land is first disturbed and ends with final stabilization. In addition:
b. The entire period of construction activity must fall within the following timeframes:
i. For sites west of the Cascades Crest: June 15 – September 15.
ii. For sites east of the Cascades Crest, excluding the Central Basin:
June 15 – October 15.
iii. For sites east of the Cascades Crest, within the Central Basin: no timeframe
restrictions apply. The Central Basin is defined as the portions of Eastern
Washington with mean annual precipitation of less than 12 inches. For a map of
the Central Basin (Average Annual Precipitation Region 2), refer to:
http://www.ecy.wa.gov/programs/wq/stormwater/construction/resourcesguida
nce.html.
3. Construction site operators must submit a complete Erosivity Waiver certification form at
least one week before disturbing the land. Certification must include statements that the
operator will:
a. Comply with applicable local stormwater requirements; and
b. Implement appropriate erosion and sediment control BMPs to prevent violations of
water quality standards.
4. This waiver is not available for facilities declared significant contributors of pollutants as
defined in Special Condition S1.B.1.b or for any size construction activity that could
Construction Stormwater General Permit Page 7
reasonably expect to cause a violation of any water quality standard as defined in Special
Condition S1.B.1.b.ii.
5. This waiver does not apply to construction activities which include non-stormwater
discharges listed in Special Condition S1.C.3.
6. If construction activity extends beyond the certified waiver period for any reason, the
operator must either:
a. Recalculate the rainfall erosivity “R” factor using the original start date and a new
projected ending date and, if the “R” factor is still under 5 and the entire project
falls within the applicable regional timeframe in Special Condition S1.F.2.b,
complete and submit an amended waiver certification form before the original
waiver expires; or
b. Submit a complete permit application to Ecology in accordance with Special
Condition S2.A and B before the end of the certified waiver period.
S2. APPLICATION REQUIREMENTS
A. Permit Application Forms
1. Notice of Intent Form
a. Operators of new or previously unpermitted construction activities must submit a
complete and accurate permit application (Notice of Intent, or NOI) to Ecology.
b. Operators must apply using the electronic application form (NOI) available on Ecology’s
website (http://ecy.wa.gov/programs/wq/stormwater/construction/index.html).
Permittees unable to submit electronically (for example, those who do not have an
internet connection) must contact Ecology to request a waiver and obtain instructions
on how to obtain a paper NOI.
Department of Ecology
Water Quality Program - Construction Stormwater
PO Box 47696
Olympia, Washington 98504-7696
c. The operator must submit the NOI at least 60 days before discharging stormwater
from construction activities and must submit it prior to the date of the first public
notice (See Special Condition S2.B, below, for details). The 30-day public comment
period begins on the publication date of the second public notice. Unless Ecology
responds to the complete application in writing, coverage under the general permit
will automatically commence on the 31st day following receipt by Ecology of a
completed NOI, or the issuance date of this permit, whichever is later; unless Ecology
specifies a later date in writing as required by WAC173-226-200(2). See S8.B for
Limits on Coverage for New Discharges to TMDL or 303(d)-Listed Waters.
d. If an applicant intends to use a Best Management Practice (BMP) selected on the
basis of Special Condition S9.C.4 (“demonstrably equivalent” BMPs), the applicant
must notify Ecology of its selection as part of the NOI. In the event the applicant
selects BMPs after submission of the NOI, the applicant must provide notice of the
Construction Stormwater General Permit Page 8
selection of an equivalent BMP to Ecology at least 60 days before intended use of
the equivalent BMP.
e. Applicants must notify Ecology if they are aware of contaminated soils and/or
groundwater associated with the construction activity. Provide detailed information
with the NOI (as known and readily available) on the nature and extent of the
contamination (concentrations, locations, and depth), as well as pollution
prevention and/or treatment BMPs proposed to control the discharge of soil and/or
groundwater contaminants in stormwater. Examples of such detail may include, but
are not limited to:
i. List or table of all known contaminants with laboratory test results showing
concentration and depth,
ii. Map with sample locations,
iii. Related portions of the Stormwater Pollution Prevention Plan (SWPPP) that
address the management of contaminated and potentially contaminated
construction stormwater and dewatering water,
iv. Dewatering plan and/or dewatering contingency plan.
2. Transfer of Coverage Form
The Permittee can transfer current coverage under this permit to one or more new
operators, including operators of sites within a Common Plan of Development, provided:
i. The Permittee submits a complete Transfer of Coverage Form to Ecology,
signed by the current and new discharger and containing a specific date for
transfer of permit responsibility, coverage and liability (including any
Administrative Orders associated with the permit); and
ii. Ecology does not notify the current discharger and new discharger of intent to
revoke coverage under the general permit. If this notice is not given, the
transfer is effective on the date specified in the written agreement.
When a current discharger (Permittee) transfers a portion of a permitted site, the current
discharger must also indicate the remaining permitted acreage after the transfer.
Transfers do not require public notice.
3. Modification of Coverage Form
Permittees must notify Ecology regarding any changes to the information provided on
the NOI by submitting an Update/Modification of Permit Coverage form in accordance
with General Conditions G6 and G19. Examples of such changes include, but are not
limited to:
i. Changes to the Permittee’s mailing address,
ii. Changes to the on-site contact person information, and
iii. Changes to the area/acreage affected by construction activity.
Construction Stormwater General Permit Page 9
B. Public Notice
For new or previously unpermitted construction activities, the applicant must publish a public
notice at least one time each week for two consecutive weeks, at least 7 days apart, in a
newspaper with general circulation in the county where the construction is to take place. The
notice must be run after the NOI has been submitted and must contain:
1. A statement that “The applicant is seeking coverage under the Washington State
Department of Ecology’s Construction Stormwater NPDES and State Waste Discharge
General Permit.”
2. The name, address, and location of the construction site.
3. The name and address of the applicant.
4. The type of construction activity that will result in a discharge (for example, residential
construction, commercial construction, etc.), and the total number of acres to be
disturbed over the lifetime of the project.
5. The name of the receiving water(s) (that is, the surface water(s) to which the site will
discharge), or, if the discharge is through a storm sewer system, the name of the
operator of the system and the receiving water(s) the system discharges to.
6. The statement: Any persons desiring to present their views to the Washington State
Department of Ecology regarding this application, or interested in Ecology’s action on this
application, may notify Ecology in writing no later than 30 days of the last date of
publication of this notice. Ecology reviews public comments and considers whether
discharges from this project would cause a measurable change in receiving water quality,
and, if so, whether the project is necessary and in the overriding public interest according
to Tier II antidegradation requirements under WAC 173-201A-320. Comments can be
submitted to: Department of Ecology, PO Box 47696, Olympia, Washington 98504-7696
Attn: Water Quality Program, Construction Stormwater.
S3. COMPLIANCE WITH STANDARDS
A. Discharges must not cause or contribute to a violation of surface water quality standards
(Chapter 173-201A WAC), groundwater quality standards (Chapter 173-200 WAC),
sediment management standards (Chapter 173-204 WAC), and human health-based
criteria in the Federal water quality criteria applicable to Washington. (40 CFR Part 131.45)
Discharges that are not in compliance with these standards are prohibited.
B. Prior to the discharge of stormwater and non-stormwater to waters of the State, the
Permittee must apply All Known, Available, and Reasonable methods of prevention,
control, and Treatment (AKART). This includes the preparation and implementation of an
adequate SWPPP, with all appropriate BMPs installed and maintained in accordance with
the SWPPP and the terms and conditions of this permit.
C. Ecology presumes that a Permittee complies with water quality standards unless discharge
monitoring data or other site-specific information demonstrates that a discharge causes or
contributes to a violation of water quality standards, when the Permittee complies with the
following conditions. The Permittee must fully:
Construction Stormwater General Permit Page 10
1. Comply with all permit conditions, including; planning, sampling, monitoring,
reporting, and recordkeeping conditions.
2. Implement stormwater BMPs contained in stormwater management manuals
published or approved by Ecology, or BMPs that are demonstrably equivalent to BMPs
contained in stormwater management manuals published or approved by Ecology,
including the proper selection, implementation, and maintenance of all applicable and
appropriate BMPs for on-site pollution control. (For purposes of this section, the
stormwater manuals listed in Appendix 10 of the Phase I Municipal Stormwater Permit
are approved by Ecology.)
D. Where construction sites also discharge to groundwater, the groundwater discharges must
also meet the terms and conditions of this CSWGP. Permittees who discharge to
groundwater through an injection well must also comply with any applicable requirements
of the Underground Injection Control (UIC) regulations, Chapter 173-218 WAC.
S4. MONITORING REQUIREMENTS, BENCHMARKS, AND
REPORTING TRIGGERS
A. Site Log Book
The Permittee must maintain a site log book that contains a record of the implementation of
the SWPPP and other permit requirements, including the installation and maintenance of
BMPs, site inspections, and stormwater monitoring.
B. Site Inspections
Construction sites one (1) acre or larger that discharge stormwater to surface waters of the
State must have site inspections conducted by a Certified Erosion and Sediment Control Lead
(CESCL). Sites less than one (1) acre may have a person without CESCL certification conduct
inspections. (See Special Conditions S4.B.3 and B.4, below, for detailed requirements of the
Permittee’s CESCL.)
Site inspections must include all areas disturbed by construction activities, all BMPs, and all
stormwater discharge points under the Permittee’s operational control.
1. The Permittee must have staff knowledgeable in the principles and practices of erosion
and sediment control. The CESCL (sites one acre or more) or inspector (sites less than one
acre) must have the skills to assess the:
a. Site conditions and construction activities that could impact the quality of
stormwater; and
b. Effectiveness of erosion and sediment control measures used to control the quality
of stormwater discharges. The SWPPP must identify the CESCL or inspector, who
must be present on site or on-call at all times. The CESCL (sites one (1) acre or more)
must obtain this certification through an approved erosion and sediment control
training program that meets the minimum training standards established by Ecology.
(See BMP C160 in the manual, referred to in Special Condition S9.C.1 and 2.)
2. The CESCL or inspector must examine stormwater visually for the presence of suspended
sediment, turbidity, discoloration, and oil sheen. BMP effectiveness must be evaluated to
Construction Stormwater General Permit Page 11
determine if it is necessary to install, maintain, or repair BMPs to improve the quality of
stormwater discharges.
Based on the results of the inspection, the Permittee must correct the problems
identified, by:
a. Reviewing the SWPPP for compliance with Special Condition S9 and making
appropriate revisions within 7 days of the inspection.
b. Immediately beginning the process of fully implementing and maintaining
appropriate source control and/or treatment BMPs, within 10 days of the
inspection. If installation of necessary treatment BMPs is not feasible within 10
days, Ecology may approve additional time when an extension is requested by a
Permittee within the initial 10-day response period.
c. Documenting BMP implementation and maintenance in the site log book.
3. The CESCL or inspector must inspect all areas disturbed by construction activities, all
BMPs, and all stormwater discharge points at least once every calendar week and within
24 hours of any discharge from the site. (For purposes of this condition, individual
discharge events that last more than one (1) day do not require daily inspections. For
example, if a stormwater pond discharges continuously over the course of a week, only
one (1) inspection is required that week.) Inspection frequency may be reduced to once
every calendar month for inactive sites that are temporarily stabilized.
4. The Permittee must summarize the results of each inspection in an inspection report or
checklist and enter the report/checklist into, or attach it to, the site log book. At a
minimum, each inspection report or checklist must include:
a. Inspection date and time.
b. Weather information.
c. The general conditions during inspection.
d. The approximate amount of precipitation since the last inspection.
e. The approximate amount of precipitation within the last 24 hours.
f. A summary or list of all implemented BMPs, including observations of all
erosion/sediment control structures or practices.
g. A description of:
i. BMPs inspected (including location).
ii. BMPs that need maintenance and why.
iii. BMPs that failed to operate as designed or intended, and
iv. Where additional or different BMPs are needed, and why.
h. A description of stormwater discharged from the site. The Permittee must note the
presence of suspended sediment, turbidity, discoloration, and oil sheen, as
applicable.
Construction Stormwater General Permit Page 12
i. Any water quality monitoring performed during inspection.
j. General comments and notes, including a brief description of any BMP repairs,
maintenance, or installations made following the inspection.
k. An implementation schedule for the remedial actions that the Permittee plans to
take if the site inspection indicates that the site is out of compliance. The remedial
actions taken must meet the requirements of the SWPPP and the permit.
l. A summary report of the inspection.
m. The name, title, and signature of the person conducting the site inspection, a phone
number or other reliable method to reach this person, and the following statement:
I certify that this report is true, accurate, and complete to the best of my knowledge
and belief.
Table 3 Summary of Primary Monitoring Requirements
Size of Soil
Disturbance1
Weekly Site
Inspections
Weekly
Sampling w/
Turbidity Meter
Weekly Sampling w/
Transparency
Tube
Weekly pH
Sampling2
CESCL
Required for
Inspections?
Sites that disturb less
than 1 acre, but are
part of a larger
Common Plan of
Development
Required Not Required Not Required Not Required No
Sites that disturb 1 acre or more, but
fewer than 5 acres
Required Sampling Required –
either method3
Required Yes
Sites that disturb 5 acres or more
Required Required Not Required4 Required Yes
1 Soil disturbance is calculated by adding together all areas that will be affected by construction activity.
Construction activity means clearing, grading, excavation, and any other activity that disturbs the surface of the
land, including ingress/egress from the site.
2 If construction activity results in the disturbance of 1 acre or more, and involves significant concrete work (1,000
cubic yards of concrete or recycled concrete placed or poured over the life of a project) or the use of engineered
soils (soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln dust [CKD], or
fly ash), and stormwater from the affected area drains to surface waters of the State or to a storm sewer
stormwater collection system that drains to other surface waters of the State, the Permittee must conduct pH
sampling in accordance with Special Condition S4.D.
3 Sites with one or more acres, but fewer than 5 acres of soil disturbance, must conduct turbidity or transparency
sampling in accordance with Special Condition S4.C.4.a or b.
4 Sites equal to or greater than 5 acres of soil disturbance must conduct turbidity sampling using a turbidity meter
in accordance with Special Condition S4.C.4.a.
Construction Stormwater General Permit Page 13
C. Turbidity/Transparency Sampling Requirements
1. Sampling Methods
a. If construction activity involves the disturbance of five (5) acres or more, the
Permittee must conduct turbidity sampling per Special Condition S4.C.4.a, below.
b. If construction activity involves one (1) acre or more but fewer than five (5) acres of
soil disturbance, the Permittee must conduct either transparency sampling or
turbidity sampling per Special Condition S4.C.4.a or b, below.
2. Sampling Frequency
a. The Permittee must sample all discharge points at least once every calendar week
when stormwater (or authorized non-stormwater) discharges from the site or
enters any on-site surface waters of the state (for example, a creek running through
a site); sampling is not required on sites that disturb less than an acre.
b. Samples must be representative of the flow and characteristics of the discharge.
c. Sampling is not required when there is no discharge during a calendar week.
d. Sampling is not required outside of normal working hours or during unsafe
conditions.
e. If the Permittee is unable to sample during a monitoring period, the Permittee must
include a brief explanation in the monthly Discharge Monitoring Report (DMR).
f. Sampling is not required before construction activity begins.
g. The Permittee may reduce the sampling frequency for temporarily stabilized,
inactive sites to once every calendar month.
3. Sampling Locations
a. Sampling is required at all points where stormwater associated with construction
activity (or authorized non-stormwater) is discharged off site, including where it
enters any on-site surface waters of the state (for example, a creek running through
a site).
b. The Permittee may discontinue sampling at discharge points that drain areas of the
project that are fully stabilized to prevent erosion.
c. The Permittee must identify all sampling point(s) in the SWPPP and on the site map
and clearly mark these points in the field with a flag, tape, stake or other visible
marker.
d. Sampling is not required for discharge that is sent directly to sanitary or combined
sewer systems.
e. The Permittee may discontinue sampling at discharge points in areas of the project
where the Permittee no longer has operational control of the construction activity.
Construction Stormwater General Permit Page 14
4. Sampling and Analysis Methods
a. The Permittee performs turbidity analysis with a calibrated turbidity meter
(turbidimeter) either on site or at an accredited lab. The Permittee must record the
results in the site log book in nephelometric turbidity units (NTUs).
b. The Permittee performs transparency analysis on site with a 1¾ inch diameter, 60
centimeter (cm)-long transparency tube. The Permittee will record the results in the
site log book in centimeters (cm).
Table 4 Monitoring and Reporting Requirements
Parameter Unit Analytical Method Sampling
Frequency
Benchmark
Value
Turbidity NTU SM2130 Weekly, if
discharging 25 NTUs
Transparency Cm
Manufacturer
instructions, or Ecology guidance
Weekly, if
discharging 33 cm
5. Turbidity/Transparency Benchmark Values and Reporting Triggers
The benchmark value for turbidity is 25 NTUs. The benchmark value for transparency is
33 centimeters (cm). Note: Benchmark values do not apply to discharges to segments of
water bodies on Washington State’s 303(d) list (Category 5) for turbidity, fine sediment,
or phosphorus; these discharges are subject to a numeric effluent limit for turbidity.
Refer to Special Condition S8 for more information and follow S5.F – Noncompliance
Notification for reporting requirements applicable to discharges which exceed the
numeric effluent limit for turbidity.
a. Turbidity 26 – 249 NTUs, or Transparency 32 – 7 cm:
If the discharge turbidity is 26 to 249 NTUs; or if discharge transparency is 32 to 7
cm, the Permittee must:
i. Immediately begin the process to fully implement and maintain appropriate
source control and/or treatment BMPs, and no later than 10 days of the date
the discharge exceeded the benchmark. If installation of necessary treatment
BMPs is not feasible within 10 days, Ecology may approve additional time when
the Permittee requests an extension within the initial 10-day response period.
ii. Review the SWPPP for compliance with Special Condition S9 and make
appropriate revisions within 7 days of the date the discharge exceeded the
benchmark.
iii. Document BMP implementation and maintenance in the site log book.
b. Turbidity 250 NTUs or greater, or Transparency 6 cm or less:
If a discharge point’s turbidity is 250 NTUs or greater, or if discharge transparency is
less than or equal to 6 cm, the Permittee must complete the reporting and adaptive
Construction Stormwater General Permit Page 15
management process described below. For discharges which are subject to a
numeric effluent limit for turbidity, see S5.F – Noncompliance Notification.
i. Within 24 hours, telephone or submit an electronic report to the applicable
Ecology Region’s Environmental Report Tracking System (ERTS) number (or
through Ecology’s Water Quality Permitting Portal [WQWebPortal] – Permit
Submittals when the form is available), in accordance with Special Condition S5.A.
• Central Region (Okanogan, Chelan, Douglas, Kittitas, Yakima, Klickitat,
Benton): (509) 575-2490
• Eastern Region (Adams, Asotin, Columbia, Ferry, Franklin, Garfield,
Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, Whitman):
(509) 329-3400
• Northwest Region (Kitsap, Snohomish, Island, King, San Juan, Skagit,
Whatcom): (425) 649-7000
• Southwest Region (Grays Harbor, Lewis, Mason, Thurston, Pierce, Clark,
Cowlitz, Skamania, Wahkiakum, Clallam, Jefferson, Pacific): (360) 407-6300
These numbers and a link to the ERTS reporting page are also listed at the following
website: http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html.
ii. Immediately begin the process to fully implement and maintain appropriate
source control and/or treatment BMPs as soon as possible, addressing the
problems within 10 days of the date the discharge exceeded the benchmark. If
installation of necessary treatment BMPs is not feasible within 10 days, Ecology
may approve additional time when the Permittee requests an extension within
the initial 10-day response period.
iii. Sample discharges daily until:
a) Turbidity is 25 NTUs (or lower); or
b) Transparency is 33 cm (or greater); or
c) The Permittee has demonstrated compliance with the water quality
standard for turbidity:
1) No more than 5 NTUs over background turbidity, if background is less
than 50 NTUs, or
2) No more than 10% over background turbidity, if background is 50
NTUs or greater; or
*Note: background turbidity in the receiving water must be
measured immediately upstream (upgradient) or outside of the area
of influence of the discharge.
d) The discharge stops or is eliminated.
iv. Review the SWPPP for compliance with Special Condition S9 and make
appropriate revisions within seven (7) days of the date the discharge exceeded
the benchmark.
Construction Stormwater General Permit Page 16
v. Document BMP implementation and maintenance in the site log book.
Compliance with these requirements does not relieve the Permittee from responsibility to
maintain continuous compliance with permit benchmarks.
D. pH Sampling Requirements – Significant Concrete Work or Engineered Soils
If construction activity results in the disturbance of 1 acre or more, and involves significant
concrete work (significant concrete work means greater than 1000 cubic yards placed or
poured concrete or recycled concrete used over the life of a project) or the use of engineered
soils (soil amendments including but not limited to Portland cement-treated base [CTB],
cement kiln dust [CKD], or fly ash), and stormwater from the affected area drains to surface
waters of the State or to a storm sewer system that drains to surface waters of the State, the
Permittee must conduct pH sampling as set forth below. Note: In addition, discharges to
segments of water bodies on Washington State’s 303(d) list (Category 5) for high pH are subject
to a numeric effluent limit for pH; refer to Special Condition S8.
1. The Permittee must perform pH analysis on site with a calibrated pH meter, pH test kit,
or wide range pH indicator paper. The Permittee must record pH sampling results in the
site log book.
2. During the applicable pH monitoring period defined below, the Permittee must obtain a
representative sample of stormwater and conduct pH analysis at least once per week.
a. For sites with significant concrete work, the Permittee must begin the pH sampling
period when the concrete is first placed or poured and exposed to precipitation, and
continue weekly throughout and after the concrete placement, pour and curing
period, until stormwater pH is in the range of 6.5 to 8.5 (su).
b. For sites with recycled concrete where monitoring is required, the Permittee must
begin the weekly pH sampling period when the recycled concrete is first exposed to
precipitation and must continue until the recycled concrete is fully stabilized with
the stormwater pH in the range of 6.5 to 8.5 (su).
c. For sites with engineered soils, the Permittee must begin the pH sampling period
when the soil amendments are first exposed to precipitation and must continue
until the area of engineered soils is fully stabilized.
3. The Permittee must sample pH in the sediment trap/pond(s) or other locations that
receive stormwater runoff from the area of significant concrete work or engineered soils
before the stormwater discharges to surface waters.
4. The benchmark value for pH is 8.5 standard units. Anytime sampling indicates that pH is
8.5 or greater, the Permittee must either:
a. Prevent the high pH water (8.5 or above) from entering storm sewer systems or
surface waters of the state; or
b. If necessary, adjust or neutralize the high pH water until it is in the range of pH 6.5 to
8.5 (su) using an appropriate treatment BMP such as carbon dioxide (CO2) sparging, dry
ice or food grade vinegar. The Permittee must obtain written approval from Ecology
before using any form of chemical treatment other than CO2 sparging, dry ice or food
grade vinegar.
Construction Stormwater General Permit Page 17
S5. REPORTING AND RECORDKEEPING REQUIREMENTS
A. High Turbidity Reporting
Anytime sampling performed in accordance with Special Condition S4.C indicates turbidity has
reached the 250 NTUs or more (or transparency less than or equal to 6 cm), high turbidity
reporting level, the Permittee must notify Ecology within 24 hours of analysis either by calling
the applicable Ecology Region’s Environmental Report Tracking System (ERTS) number by
phone or by submitting an electronic ERTS report (through Ecology’s Water Quality Permitting
Portal (WQWebPortal) – Permit Submittals when the form is available). See the CSWGP website
for links to ERTS and the WQWebPortal. (http://www.ecy.wa.gov/programs/wq/stormwater/
construction/index.html) Also, see phone numbers in Special Condition S4.C.5.b.i.
B. Discharge Monitoring Reports (DMRs)
Permittees required to conduct water quality sampling in accordance with Special Conditions
S4.C (Turbidity/Transparency), S4.D (pH), S8 (303[d]/TMDL sampling), and/or G12 (Additional
Sampling) must submit the results to Ecology.
Permittees must submit monitoring data using Ecology's WQWebDMR web application
accessed through Ecology’s Water Quality Permitting Portal.
Permittees unable to submit electronically (for example, those who do not have an internet
connection) must contact Ecology to request a waiver and obtain instructions on how to obtain
a paper copy DMR at:
Department of Ecology
Water Quality Program - Construction Stormwater
PO Box 47696
Olympia, WA 98504-7696
Permittees who obtain a waiver not to use WQWebDMR must use the forms provided to them
by Ecology; submittals must be mailed to the address above. Permittees must submit DMR
forms to be received by Ecology within 15 days following the end of each month.
If there was no discharge during a given monitoring period, all Permittees must submit a DMR
as required with “no discharge” entered in place of the monitoring results. DMRs are required
for the full duration of permit coverage (from the first full month following the effective date of
permit coverage up until Ecology has approved termination of the coverage). For more
information, contact Ecology staff using information provided at the following website:
www.ecy.wa.gov/programs/wq/permits/paris/contacts.html.
C. Records Retention
The Permittee must retain records of all monitoring information (site log book, sampling
results, inspection reports/checklists, etc.), Stormwater Pollution Prevention Plan, copy of the
permit coverage letter (including Transfer of Coverage documentation) and any other
documentation of compliance with permit requirements for the entire life of the construction
project and for a minimum of five (5) years following the termination of permit coverage. Such
information must include all calibration and maintenance records, and records of all data used
to complete the application for this permit. This period of retention must be extended during
Construction Stormwater General Permit Page 18
the course of any unresolved litigation regarding the discharge of pollutants by the Permittee
or when requested by Ecology.
D. Recording Results
For each measurement or sample taken, the Permittee must record the following information:
1. Date, place, method, and time of sampling or measurement.
2. The first and last name of the individual who performed the sampling or measurement.
3. The date(s) the analyses were performed.
4. The first and last name of the individual who performed the analyses.
5. The analytical techniques or methods used.
6. The results of all analyses.
E. Additional Monitoring by the Permittee
If the Permittee samples or monitors any pollutant more frequently than required by this
permit using test procedures specified by Special Condition S4 of this permit, the sampling
results for this monitoring must be included in the calculation and reporting of the data
submitted in the Permittee’s DMR.
F. Noncompliance Notification
In the event the Permittee is unable to comply with any part of the terms and conditions of this
permit, and the resulting noncompliance may cause a threat to human health or the
environment (such as but not limited to spills or fuels or other materials, catastrophic pond or
slope failure, and discharges that violate water quality standards), or exceed numeric effluent
limitations (see S8 – Discharges to 303(d) or TMDL Waterbodies), the Permittee must, upon
becoming aware of the circumstance:
1. Notify Ecology within 24 hours of the failure to comply by calling the applicable Regional
office ERTS phone number (refer to Special Condition S4.C.5.b.i, or go to
https://ecology.wa.gov/About-us/Get-involved/Report-an-environmental-issue to find
contact information for the regional offices.)
2. Immediately take action to prevent the discharge/pollution, or otherwise stop or correct
the noncompliance, and, if applicable, repeat sampling and analysis of any noncompliance
immediately and submit the results to Ecology within five (5) days of becoming aware of
the violation (See S5.F.3, below, for details on submitting results in a report).
3. Submit a detailed written report to Ecology within five (5) days of the time the Permittee
becomes aware of the circumstances, unless requested earlier by Ecology. The report must
be submitted using Ecology’s Water Quality Permitting Portal (WQWebPortal) – Permit
Submittals, unless a waiver from electronic reporting has been granted according to S5.B.
The report must contain a description of the noncompliance, including exact dates and
times, and if the noncompliance has not been corrected, the anticipated time it is expected
to continue; and the steps taken or planned to reduce, eliminate, and prevent
reoccurrence of the noncompliance.
Construction Stormwater General Permit Page 19
The Permittee must report any unanticipated bypass and/or upset that exceeds any
effluent limit in the permit in accordance with the 24-hour reporting requirement
contained in 40 C.F.R. 122.41(l)(6).
Compliance with these requirements does not relieve the Permittee from responsibility
to maintain continuous compliance with the terms and conditions of this permit or the
resulting liability for failure to comply. Upon request of the Permittee, Ecology may waive
the requirement for a written report on a case-by-case basis, if the immediate
notification is received by Ecology within 24 hours.
G. Access to Plans and Records
1. The Permittee must retain the following permit documentation (plans and records) on
site, or within reasonable access to the site, for use by the operator or for on-site review
by Ecology or the local jurisdiction:
a. General Permit
b. Permit Coverage Letter
c. Stormwater Pollution Prevention Plan (SWPPP)
d. Site Log Book
e. Erosivity Waiver (if applicable)
2. The Permittee must address written requests for plans and records listed above (Special
Condition S5.G.1) as follows:
a. The Permittee must provide a copy of plans and records to Ecology within 14 days of
receipt of a written request from Ecology.
b. The Permittee must provide a copy of plans and records to the public when
requested in writing. Upon receiving a written request from the public for the
Permittee’s plans and records, the Permittee must either:
i. Provide a copy of the plans and records to the requester within 14 days of a
receipt of the written request; or
ii. Notify the requester within 10 days of receipt of the written request of the
location and times within normal business hours when the plans and records
may be viewed; and provide access to the plans and records within 14 days of
receipt of the written request; or
Within 14 days of receipt of the written request, the Permittee may submit a
copy of the plans and records to Ecology for viewing and/or copying by the
requester at an Ecology office, or a mutually agreed location. If plans and
records are viewed and/or copied at a location other than at an Ecology office,
the Permittee will provide reasonable access to copying services for which a
reasonable fee may be charged. The Permittee must notify the requester
within 10 days of receipt of the request where the plans and records may be
viewed and/or copied.
Construction Stormwater General Permit Page 20
S6. PERMIT FEES
The Permittee must pay permit fees assessed by Ecology. Fees for stormwater discharges covered
under this permit are established by Chapter 173-224 WAC. Ecology continues to assess permit
fees until the permit is terminated in accordance with Special Condition S10 or revoked in
accordance with General Condition G5.
S7. SOLID AND LIQUID WASTE DISPOSAL
The Permittee must handle and dispose of solid and liquid wastes generated by construction
activity, such as demolition debris, construction materials, contaminated materials, and waste
materials from maintenance activities, including liquids and solids from cleaning catch basins and
other stormwater facilities, in accordance with:
A. Special Condition S3, Compliance with Standards.
B. WAC 173-216-110.
C. Other applicable regulations.
S8. DISCHARGES TO 303(d) OR TMDL WATERBODIES
A. Sampling and Numeric Effluent Limits For Certain Discharges to 303(d)-Listed
Water Bodies
1. Permittees who discharge to segments of water bodies listed as impaired by the State of
Washington under Section 303(d) of the Clean Water Act for turbidity, fine sediment,
high pH, or phosphorus, must conduct water quality sampling according to the
requirements of this section, and Special Conditions S4.C.2.b-f and S4.C.3.b-d, and must
comply with the applicable numeric effluent limitations in S8.C and S8.D.
2. All references and requirements associated with Section 303(d) of the Clean Water Act
mean the most current listing by Ecology of impaired waters (Category 5) that exists on
January 1, 2021, or the date when the operator’s complete permit application is received
by Ecology, whichever is later.
B. Limits on Coverage for New Discharges to TMDL or 303(d)-Listed Waters
Construction sites that discharge to a TMDL or 303(d)-listed waterbody are not eligible for
coverage under this permit unless the operator:
Construction Stormwater General Permit Page 21
1. Prevents exposing stormwater to pollutants for which the waterbody is impaired, and
retains documentation in the SWPPP that details procedures taken to prevent exposure
on site; or
2. Documents that the pollutants for which the waterbody is impaired are not present at
the site, and retains documentation of this finding within the SWPPP; or
3. Provides Ecology with data indicating the discharge is not expected to cause or
contribute to an exceedance of a water quality standard, and retains such data on site
with the SWPPP. The operator must provide data and other technical information to
Ecology that sufficiently demonstrate:
a. For discharges to waters without an EPA-approved or -established TMDL, that the
discharge of the pollutant for which the water is impaired will meet in-stream water
quality criteria at the point of discharge to the waterbody; or
b. For discharges to waters with an EPA-approved or -established TMDL, that there is
sufficient remaining wasteload allocation in the TMDL to allow construction
stormwater discharge and that existing dischargers to the waterbody are subject to
compliance schedules designed to bring the waterbody into attainment with water
quality standards.
Operators of construction sites are eligible for coverage under this permit only after
Ecology makes an affirmative determination that the discharge will not cause or
contribute to the existing impairment or exceed the TMDL.
C. Sampling and Numeric Effluent Limits for Discharges to Water Bodies on the 303(d) List
for Turbidity, Fine Sediment, or Phosphorus
1. Permittees who discharge to segments of water bodies on the 303(d) list (Category 5) for
turbidity, fine sediment, or phosphorus must conduct turbidity sampling in accordance
with Special Condition S4.C.2 and comply with either of the numeric effluent limits noted
in Table 5 below.
2. As an alternative to the 25 NTUs effluent limit noted in Table 5 below (applied at the
point where stormwater [or authorized non-stormwater] is discharged off-site),
Permittees may choose to comply with the surface water quality standard for turbidity.
The standard is: no more than 5 NTUs over background turbidity when the background
turbidity is 50 NTUs or less, or no more than a 10% increase in turbidity when the
background turbidity is more than 50 NTUs. In order to use the water quality standard
requirement, the sampling must take place at the following locations:
a. Background turbidity in the 303(d)-listed receiving water immediately upstream
(upgradient) or outside the area of influence of the discharge.
b. Turbidity at the point of discharge into the 303(d)-listed receiving water, inside the
area of influence of the discharge.
3. Discharges that exceed the numeric effluent limit for turbidity constitute a violation of
this permit.
4. Permittees whose discharges exceed the numeric effluent limit must sample discharges
daily until the violation is corrected and comply with the non-compliance notification
requirements in Special Condition S5.F.
Construction Stormwater General Permit Page 22
Table 5 Turbidity, Fine Sediment & Phosphorus Sampling and Limits for 303(d)-Listed Waters
Parameter identified in
303(d) listing
Parameter
Sampled Unit Analytical
Method
Sampling
Frequency
Numeric Effluent
Limit1
• Turbidity
• Fine Sediment
• Phosphorus
Turbidity NTU SM2130 Weekly, if discharging 25 NTUs, at the point where stormwater is
discharged from the
site; OR
In compliance with
the surface water
quality standard for
turbidity (S8.C.2.a)
1 Permittees subject to a numeric effluent limit for turbidity may, at their discretion, choose either
numeric effluent limitation based on site-specific considerations including, but not limited to,
safety, access and convenience.
D. Discharges to Water Bodies on the 303(d) List for High pH
1. Permittees who discharge to segments of water bodies on the 303(d) list (Category 5) for
high pH must conduct pH sampling in accordance with the table below, and comply with
the numeric effluent limit of pH 6.5 to 8.5 su (Table 6).
Table 6 pH Sampling and Limits for 303(d)-Listed Waters
Parameter identified in 303(d)
listing
Parameter
Sampled/Units
Analytical
Method
Sampling
Frequency
Numeric Effluent
Limit
High pH pH /Standard Units pH meter Weekly, if discharging In the range of 6.5 – 8.5 su
2. At the Permittee’s discretion, compliance with the limit shall be assessed at one of the
following locations:
a. Directly in the 303(d)-listed waterbody segment, inside the immediate area of
influence of the discharge; or
b. Alternatively, the Permittee may measure pH at the point where the discharge
leaves the construction site, rather than in the receiving water.
3. Discharges that exceed the numeric effluent limit for pH (outside the range of 6.5 – 8.5 su)
constitute a violation of this permit.
4. Permittees whose discharges exceed the numeric effluent limit must sample discharges
daily until the violation is corrected and comply with the non-compliance notification
requirements in Special Condition S5.F.
E. Sampling and Limits for Sites Discharging to Waters Covered by a TMDL or another
Pollution Control Plan
Construction Stormwater General Permit Page 23
1. Discharges to a waterbody that is subject to a Total Maximum Daily Load (TMDL) for
turbidity, fine sediment, high pH, or phosphorus must be consistent with the TMDL. Refer
to http://www.ecy.wa.gov/programs/wq/tmdl/TMDLsbyWria/TMDLbyWria.html for
more information on TMDLs.
a. Where an applicable TMDL sets specific waste load allocations or requirements for
discharges covered by this permit, discharges must be consistent with any specific
waste load allocations or requirements established by the applicable TMDL.
i. The Permittee must sample discharges weekly, unless otherwise specified by
the TMDL, to evaluate compliance with the specific waste load allocations or
requirements.
ii. Analytical methods used to meet the monitoring requirements must conform
to the latest revision of the Guidelines Establishing Test Procedures for the
Analysis of Pollutants contained in 40 CFR Part 136.
iii. Turbidity and pH methods need not be accredited or registered unless
conducted at a laboratory which must otherwise be accredited or registered.
b. Where an applicable TMDL has established a general waste load allocation for
construction stormwater discharges, but has not identified specific requirements,
compliance with Special Conditions S4 (Monitoring) and S9 (SWPPPs) will constitute
compliance with the approved TMDL.
c. Where an applicable TMDL has not specified a waste load allocation for construction
stormwater discharges, but has not excluded these discharges, compliance with
Special Conditions S4 (Monitoring) and S9 (SWPPPs) will constitute compliance with
the approved TMDL.
d. Where an applicable TMDL specifically precludes or prohibits discharges from
construction activity, the operator is not eligible for coverage under this permit.
S9. STORMWATER POLLUTION PREVENTION PLAN
The Permittee must prepare and properly implement an adequate Stormwater Pollution
Prevention Plan (SWPPP) for construction activity in accordance with the requirements of this
permit beginning with initial soil disturbance and until final stabilization.
A. The Permittee’s SWPPP must meet the following objectives:
1. To identify best management practices (BMPs) which prevent erosion and sedimentation,
and to reduce, eliminate or prevent stormwater contamination and water pollution from
construction activity.
2. To prevent violations of surface water quality, groundwater quality, or sediment
management standards.
3. To control peak volumetric flow rates and velocities of stormwater discharges.
Construction Stormwater General Permit Page 24
B. General Requirements
1. The SWPPP must include a narrative and drawings. All BMPs must be clearly referenced in
the narrative and marked on the drawings. The SWPPP narrative must include
documentation to explain and justify the pollution prevention decisions made for the
project. Documentation must include:
a. Information about existing site conditions (topography, drainage, soils, vegetation, etc.).
b. Potential erosion problem areas.
c. The 13 elements of a SWPPP in Special Condition S9.D.1-13, including BMPs
used to address each element.
d. Construction phasing/sequence and general BMP implementation schedule.
e. The actions to be taken if BMP performance goals are not achieved—for example,
a contingency plan for additional treatment and/or storage of stormwater that
would violate the water quality standards if discharged.
f. Engineering calculations for ponds, treatment systems, and any other designed
structures. When a treatment system requires engineering calculations, these
calculations must be included in the SWPPP. Engineering calculations do not need to
be included in the SWPPP for treatment systems that do not require such calculations.
2. The Permittee must modify the SWPPP if, during inspections or investigations conducted
by the owner/operator, or the applicable local or state regulatory authority, it is
determined that the SWPPP is, or would be, ineffective in eliminating or significantly
minimizing pollutants in stormwater discharges from the site. The Permittee must then:
a. Review the SWPPP for compliance with Special Condition S9 and make appropriate
revisions within 7 days of the inspection or investigation.
b. Immediately begin the process to fully implement and maintain appropriate source
control and/or treatment BMPs as soon as possible, addressing the problems no later
than 10 days from the inspection or investigation. If installation of necessary treatment
BMPs is not feasible within 10 days, Ecology may approve additional time when an
extension is requested by a Permittee within the initial 10-day response period.
c. Document BMP implementation and maintenance in the site log book.
The Permittee must modify the SWPPP whenever there is a change in design,
construction, operation, or maintenance at the construction site that has, or could have,
a significant effect on the discharge of pollutants to waters of the State.
C. Stormwater Best Management Practices (BMPs)
BMPs must be consistent with:
1. Stormwater Management Manual for Western Washington (most current approved
edition at the time this permit was issued), for sites west of the crest of the Cascade
Mountains; or
Construction Stormwater General Permit Page 25
2. Stormwater Management Manual for Eastern Washington (most current approved
edition at the time this permit was issued), for sites east of the crest of the Cascade
Mountains; or
3. Revisions to the manuals listed in Special Condition S9.C.1 & 2, or other stormwater
management guidance documents or manuals which provide an equivalent level of
pollution prevention, that are approved by Ecology and incorporated into this permit in
accordance with the permit modification requirements of WAC 173-226-230; or
4. Documentation in the SWPPP that the BMPs selected provide an equivalent level of
pollution prevention, compared to the applicable stormwater management manuals,
including:
a. The technical basis for the selection of all stormwater BMPs (scientific, technical studies,
and/or modeling) that support the performance claims for the BMPs being selected.
b. An assessment of how the selected BMP will satisfy AKART requirements and the
applicable federal technology-based treatment requirements under 40 CFR part 125.3.
D. SWPPP – Narrative Contents and Requirements
The Permittee must include each of the 13 elements below in Special Condition S9.D.1-13 in
the narrative of the SWPPP and implement them unless site conditions render the element
unnecessary and the exemption from that element is clearly justified in the SWPPP.
1. Preserve Vegetation/Mark Clearing Limits
a. Before beginning land-disturbing activities, including clearing and grading, clearly
mark all clearing limits, sensitive areas and their buffers, and trees that are to be
preserved within the construction area.
b. Retain the duff layer, native topsoil, and natural vegetation in an undisturbed state
to the maximum degree practicable.
2. Establish Construction Access
a. Limit construction vehicle access and exit to one route, if possible.
b. Stabilize access points with a pad of quarry spalls, crushed rock, or other equivalent
BMPs, to minimize tracking sediment onto roads.
c. Locate wheel wash or tire baths on site, if the stabilized construction entrance is not
effective in preventing tracking sediment onto roads.
d. If sediment is tracked off site, clean the affected roadway thoroughly at the end of
each day, or more frequently as necessary (for example, during wet weather).
Remove sediment from roads by shoveling, sweeping, or pickup and transport of the
sediment to a controlled sediment disposal area.
e. Conduct street washing only after sediment removal in accordance with Special
Condition S9.D.2.d.
f. Control street wash wastewater by pumping back on site or otherwise preventing it
from discharging into systems tributary to waters of the State.
Construction Stormwater General Permit Page 26
3. Control Flow Rates
a. Protect properties and waterways downstream of construction sites from erosion
and the associated discharge of turbid waters due to increases in the velocity and
peak volumetric flow rate of stormwater runoff from the project site, as required by
local plan approval authority.
b. Where necessary to comply with Special Condition S9.D.3.a, construct stormwater
infiltration or detention BMPs as one of the first steps in grading. Assure that
detention BMPs function properly before constructing site improvements (for
example, impervious surfaces).
c. If permanent infiltration ponds are used for flow control during construction,
protect these facilities from sedimentation during the construction phase.
4. Install Sediment Controls
The Permittee must design, install and maintain effective erosion controls and sediment
controls to minimize the discharge of pollutants. At a minimum, the Permittee must:
a. Construct sediment control BMPs (sediment ponds, traps, filters, infiltration
facilities, etc.) as one of the first steps in grading. These BMPs must be functional
before other land disturbing activities take place.
b. Minimize sediment discharges from the site. The design, installation and
maintenance of erosion and sediment controls must address factors such as the
amount, frequency, intensity and duration of precipitation, the nature of resulting
stormwater runoff, and soil characteristics, including the range of soil particle sizes
expected to be present on the site.
c. Direct stormwater runoff from disturbed areas through a sediment pond or other
appropriate sediment removal BMP, before the runoff leaves a construction site or
before discharge to an infiltration facility. Runoff from fully stabilized areas may be
discharged without a sediment removal BMP, but must meet the flow control
performance standard of Special Condition S9.D.3.a.
d. Locate BMPs intended to trap sediment on site in a manner to avoid interference
with the movement of juvenile salmonids attempting to enter off-channel areas or
drainages.
e. Provide and maintain natural buffers around surface waters, direct stormwater to
vegetated areas to increase sediment removal and maximize stormwater
infiltration, unless infeasible.
f. Where feasible, design outlet structures that withdraw impounded stormwater
from the surface to avoid discharging sediment that is still suspended lower in the
water column.
5. Stabilize Soils
a. The Permittee must stabilize exposed and unworked soils by application of effective
BMPs that prevent erosion. Applicable BMPs include, but are not limited to:
temporary and permanent seeding, sodding, mulching, plastic covering, erosion
Construction Stormwater General Permit Page 27
control fabrics and matting, soil application of polyacrylamide (PAM), the early
application of gravel base on areas to be paved, and dust control.
b. The Permittee must control stormwater volume and velocity within the site to
minimize soil erosion.
c. The Permittee must control stormwater discharges, including both peak flow rates
and total stormwater volume, to minimize erosion at outlets and to minimize
downstream channel and stream bank erosion.
d. Depending on the geographic location of the project, the Permittee must not allow
soils to remain exposed and unworked for more than the time periods set forth
below to prevent erosion.
West of the Cascade Mountains Crest
During the dry season (May 1 - September 30): 7 days
During the wet season (October 1 - April 30): 2 days
East of the Cascade Mountains Crest, except for Central Basin*
During the dry season (July 1 - September 30): 10 days
During the wet season (October 1 - June 30): 5 days
The Central Basin*, East of the Cascade Mountains Crest
During the dry Season (July 1 - September 30): 30 days
During the wet season (October 1 - June 30): 15 days
*Note: The Central Basin is defined as the portions of Eastern Washington
with mean annual precipitation of less than 12 inches.
e. The Permittee must stabilize soils at the end of the shift before a holiday or
weekend if needed based on the weather forecast.
f. The Permittee must stabilize soil stockpiles from erosion, protected with sediment
trapping measures, and where possible, be located away from storm drain inlets,
waterways, and drainage channels.
g. The Permittee must minimize the amount of soil exposed during construction activity.
h. The Permittee must minimize the disturbance of steep slopes.
i. The Permittee must minimize soil compaction and, unless infeasible, preserve topsoil.
6. Protect Slopes
a. The Permittee must design and construct cut-and-fill slopes in a manner to minimize
erosion. Applicable practices include, but are not limited to, reducing continuous
length of slope with terracing and diversions, reducing slope steepness, and
roughening slope surfaces (for example, track walking).
b. The Permittee must divert off-site stormwater (run-on) or groundwater away from
slopes and disturbed areas with interceptor dikes, pipes, and/or swales. Off-site
stormwater should be managed separately from stormwater generated on the site.
c. At the top of slopes, collect drainage in pipe slope drains or protected channels to
prevent erosion.
Construction Stormwater General Permit Page 28
i. West of the Cascade Mountains Crest: Temporary pipe slope drains must handle
the peak 10-minute flow rate from a Type 1A, 10-year, 24-hour frequency storm
for the developed condition. Alternatively, the 10-year, 1-hour flow rate
predicted by an approved continuous runoff model, increased by a factor of 1.6,
may be used. The hydrologic analysis must use the existing land cover condition
for predicting flow rates from tributary areas outside the project limits. For
tributary areas on the project site, the analysis must use the temporary or
permanent project land cover condition, whichever will produce the highest flow
rates. If using the Western Washington Hydrology Model (WWHM) to predict
flows, bare soil areas should be modeled as "landscaped area.”
ii. East of the Cascade Mountains Crest: Temporary pipe slope drains must handle
the expected peak flow rate from a 6-month, 3-hour storm for the developed
condition, referred to as the short duration storm.
d. Place excavated material on the uphill side of trenches, consistent with safety and
space considerations.
e. Place check dams at regular intervals within constructed channels that are cut down
a slope.
7. Protect Drain Inlets
a. Protect all storm drain inlets made operable during construction so that stormwater
runoff does not enter the conveyance system without first being filtered or treated
to remove sediment.
b. Clean or remove and replace inlet protection devices when sediment has filled one-
third of the available storage (unless a different standard is specified by the product
manufacturer).
8. Stabilize Channels and Outlets
a. Design, construct and stabilize all on-site conveyance channels to prevent erosion
from the following expected peak flows:
i. West of the Cascade Mountains Crest: Channels must handle the peak 10-
minute flow rate from a Type 1A, 10-year, 24-hour frequency storm for the
developed condition. Alternatively, the 10-year, 1-hour flow rate indicated by
an approved continuous runoff model, increased by a factor of 1.6, may be
used. The hydrologic analysis must use the existing land cover condition for
predicting flow rates from tributary areas outside the project limits. For
tributary areas on the project site, the analysis must use the temporary or
permanent project land cover condition, whichever will produce the highest
flow rates. If using the WWHM to predict flows, bare soil areas should be
modeled as "landscaped area.”
ii. East of the Cascade Mountains Crest: Channels must handle the expected peak
flow rate from a 6-month, 3-hour storm for the developed condition, referred
to as the short duration storm.
b. Provide stabilization, including armoring material, adequate to prevent erosion of
outlets, adjacent stream banks, slopes, and downstream reaches at the outlets of all
conveyance systems.
Construction Stormwater General Permit Page 29
9. Control Pollutants
Design, install, implement and maintain effective pollution prevention measures to
minimize the discharge of pollutants. The Permittee must:
a. Handle and dispose of all pollutants, including waste materials and demolition
debris that occur on site in a manner that does not cause contamination of
stormwater.
b. Provide cover, containment, and protection from vandalism for all chemicals, liquid
products, petroleum products, and other materials that have the potential to pose a
threat to human health or the environment. Minimize storage of hazardous
materials on-site. Safety Data Sheets (SDS) should be supplied for all materials
stored. Chemicals should be kept in their original labeled containers. On-site fueling
tanks must include secondary containment. Secondary containment means placing
tanks or containers within an impervious structure capable of containing 110% of
the volume of the largest tank within the containment structure. Double-walled
tanks do not require additional secondary containment.
c. Conduct maintenance, fueling, and repair of heavy equipment and vehicles using
spill prevention and control measures. Clean contaminated surfaces immediately
following any spill incident.
d. Discharge wheel wash or tire bath wastewater to a separate on-site treatment
system that prevents discharge to surface water, such as closed-loop recirculation
or upland land application, or to the sanitary sewer with local sewer district
approval.
e. Apply fertilizers and pesticides in a manner and at application rates that will not
result in loss of chemical to stormwater runoff. Follow manufacturers’ label
requirements for application rates and procedures.
f. Use BMPs to prevent contamination of stormwater runoff by pH-modifying sources.
The sources for this contamination include, but are not limited to: bulk cement,
cement kiln dust, fly ash, new concrete washing and curing waters, recycled
concrete stockpiles, waste streams generated from concrete grinding and sawing,
exposed aggregate processes, dewatering concrete vaults, concrete pumping and
mixer washout waters. (Also refer to the definition for "concrete wastewater" in
Appendix A – Definitions.)
g. Adjust the pH of stormwater or authorized non-stormwater if necessary to prevent
an exceedance of groundwater and/or surface water quality standards.
h. Assure that washout of concrete trucks is performed off-site or in designated
concrete washout areas only. Do not wash out concrete truck drums onto the
ground, or into storm drains, open ditches, streets, or streams. Washout of small
concrete handling equipment may be disposed of in a formed area awaiting
concrete where it will not contaminate surface or groundwater. Do not dump excess
concrete on site, except in designated concrete washout areas. Concrete spillage or
concrete discharge directly to groundwater or surface waters of the State is
Construction Stormwater General Permit Page 30
prohibited. At no time shall concrete be washed off into the footprint of an area
where an infiltration BMP will be installed.
i. Obtain written approval from Ecology before using any chemical treatment, with
the exception of CO2, dry ice or food grade vinegar, to adjust pH.
j. Uncontaminated water from water-only based shaft drilling for construction of
building, road, and bridge foundations may be infiltrated provided the wastewater is
managed in a way that prohibits discharge to surface waters. Prior to infiltration,
water from water-only based shaft drilling that comes into contact with curing
concrete must be neutralized until pH is in the range of 6.5 to 8.5 (su).
10. Control Dewatering
a. Permittees must discharge foundation, vault, and trench dewatering water, which
have characteristics similar to stormwater runoff at the site, in conjunction with BMPs
to reduce sedimentation before discharge to a sediment trap or sediment pond.
b. Permittees may discharge clean, non-turbid dewatering water, such as well-point
groundwater, to systems tributary to, or directly into surface waters of the State, as
specified in Special Condition S9.D.8, provided the dewatering flow does not cause
erosion or flooding of receiving waters. Do not route clean dewatering water through
stormwater sediment ponds. Note that “surface waters of the State” may exist on a
construction site as well as off site; for example, a creek running through a site.
c. Other dewatering treatment or disposal options may include:
i. Infiltration
ii. Transport off site in a vehicle, such as a vacuum flush truck, for legal disposal in
a manner that does not pollute state waters.
iii. Ecology-approved on-site chemical treatment or other suitable treatment
technologies (See S9.D.9.i, regarding chemical treatment written approval).
iv. Sanitary or combined sewer discharge with local sewer district approval, if
there is no other option.
v. Use of a sedimentation bag with discharge to a ditch or swale for small
volumes of localized dewatering.
d. Permittees must handle highly turbid or contaminated dewatering water separately
from stormwater.
11. Maintain BMPs
a. Permittees must maintain and repair all temporary and permanent erosion and
sediment control BMPs as needed to assure continued performance of their
intended function in accordance with BMP specifications.
b. Permittees must remove all temporary erosion and sediment control BMPs within
30 days after achieving final site stabilization or after the temporary BMPs are no
longer needed.
Construction Stormwater General Permit Page 31
12. Manage the Project
a. Phase development projects to the maximum degree practicable and take into
account seasonal work limitations.
b. Inspect, maintain and repair all BMPs as needed to assure continued performance
of their intended function. Conduct site inspections and monitoring in accordance
with Special Condition S4.
c. Maintain, update, and implement the SWPPP in accordance with Special Conditions
S3, S4, and S9.
13. Protect Low Impact Development (LID) BMPs
The primary purpose of on-site LID Stormwater Management is to reduce the disruption of
the natural site hydrology through infiltration. LID BMPs are permanent facilities.
a. Permittees must protect all LID BMPs (including, but not limited to, Bioretention and
Rain Garden facilities) from sedimentation through installation and maintenance of
erosion and sediment control BMPs on portions of the site that drain into the
Bioretention and/or Rain Garden facilities. Restore the BMPs to their fully
functioning condition if they accumulate sediment during construction. Restoring
the facility must include removal of sediment and any sediment-laden bioretention/
rain garden soils, and replacing the removed soils with soils meeting the design
specification.
b. Permittees must maintain the infiltration capabilities of LID BMPs by protecting
against compaction by construction equipment and foot traffic. Protect completed
lawn and landscaped areas from compaction due to construction equipment.
c. Permittees must control erosion and avoid introducing sediment from surrounding
land uses onto permeable pavements. Do not allow muddy construction equipment
on the base material or pavement. Do not allow sediment-laden runoff onto
permeable pavements or base materials.
d. Permittees must clean permeable pavements fouled with sediments or no longer
passing an initial infiltration test using local stormwater manual methodology or the
manufacturer’s procedures.
e. Permittees must keep all heavy equipment off existing soils under LID BMPs that
have been excavated to final grade to retain the infiltration rate of the soils.
E. SWPPP – Map Contents and Requirements
The Permittee’s SWPPP must also include a vicinity map or general location map (for example,
a USGS quadrangle map, a portion of a county or city map, or other appropriate map) with
enough detail to identify the location of the construction site and receiving waters within one
mile of the site.
The SWPPP must also include a legible site map (or maps) showing the entire construction site.
The following features must be identified, unless not applicable due to site conditions.
1. The direction of north, property lines, and existing structures and roads.
2. Cut and fill slopes indicating the top and bottom of slope catch lines.
Construction Stormwater General Permit Page 32
3. Approximate slopes, contours, and direction of stormwater flow before and after major
grading activities.
4. Areas of soil disturbance and areas that will not be disturbed.
5. Locations of structural and nonstructural controls (BMPs) identified in the SWPPP.
6. Locations of off-site material, stockpiles, waste storage, borrow areas, and
vehicle/equipment storage areas.
7. Locations of all surface water bodies, including wetlands.
8. Locations where stormwater or non-stormwater discharges off-site and/or to a surface
waterbody, including wetlands.
9. Location of water quality sampling station(s), if sampling is required by state or local
permitting authority.
10. Areas where final stabilization has been accomplished and no further construction-phase
permit requirements apply.
11. Location or proposed location of LID facilities.
S10. NOTICE OF TERMINATION
Partial terminations of permit coverage are not authorized.
A. The site is eligible for termination of coverage when it has met any of the following
conditions:
1. The site has undergone final stabilization, the Permittee has removed all temporary
BMPs (except biodegradable BMPs clearly manufactured with the intention for the
material to be left in place and not interfere with maintenance or land use), and all
stormwater discharges associated with construction activity have been eliminated; or
2. All portions of the site that have not undergone final stabilization per Special Condition
S10.A.1 have been sold and/or transferred (per Special Condition S2.A), and the
Permittee no longer has operational control of the construction activity; or
3. For residential construction only, the Permittee has completed temporary stabilization
and the homeowners have taken possession of the residences.
B. When the site is eligible for termination, the Permittee must submit a complete and
accurate Notice of Termination (NOT) form, signed in accordance with General
Condition G2, to:
Department of Ecology
Water Quality Program - Construction Stormwater
PO Box 47696
Olympia, WA 98504-7696
Construction Stormwater General Permit Page 33
When an electronic termination form is available, the Permittee may choose to submit a
complete and accurate Notice of Termination (NOT) form through the Water Quality Permitting
Portal rather than mailing a hardcopy as noted above.
The termination is effective on the 31st calendar day following the date Ecology receives a
complete NOT form, unless Ecology notifies the Permittee that termination request is denied
because the Permittee has not met the eligibility requirements in Special Condition S10.A.
Permittees are required to comply with all conditions and effluent limitations in the permit
until the permit has been terminated.
Permittees transferring the property to a new property owner or operator/Permittee are
required to complete and submit the Notice of Transfer form to Ecology, but are not required
to submit a Notice of Termination form for this type of transaction.
Construction Stormwater General Permit Page 34
GENERAL CONDITIONS
G1. DISCHARGE VIOLATIONS
All discharges and activities authorized by this general permit must be consistent with the terms
and conditions of this general permit. Any discharge of any pollutant more frequent than or at a
level in excess of that identified and authorized by the general permit must constitute a violation of
the terms and conditions of this permit.
G2. SIGNATORY REQUIREMENTS
A. All permit applications must bear a certification of correctness to be signed:
1. In the case of corporations, by a responsible corporate officer.
2. In the case of a partnership, by a general partner of a partnership.
3. In the case of sole proprietorship, by the proprietor.
4. In the case of a municipal, state, or other public facility, by either a principal executive
officer or ranking elected official.
B. All reports required by this permit and other information requested by Ecology (including
NOIs, NOTs, and Transfer of Coverage forms) must be signed by a person described above
or by a duly authorized representative of that person. A person is a duly authorized
representative only if:
1. The authorization is made in writing by a person described above and submitted to
Ecology.
2. The authorization specifies either an individual or a position having responsibility for
the overall operation of the regulated facility, such as the position of plant manager,
superintendent, position of equivalent responsibility, or an individual or position
having overall responsibility for environmental matters.
C. Changes to authorization. If an authorization under paragraph G2.B.2 above is no longer
accurate because a different individual or position has responsibility for the overall
operation of the facility, a new authorization satisfying the requirements of paragraph
G2.B.2 above must be submitted to Ecology prior to or together with any reports,
information, or applications to be signed by an authorized representative.
D. Certification. Any person signing a document under this section must make the following
certification:
I certify under penalty of law, that this document and all attachments were
prepared under my direction or supervision in accordance with a system
designed to assure that qualified personnel properly gathered and evaluated the
information submitted. Based on my inquiry of the person or persons who
manage the system, or those persons directly responsible for gathering
information, the information submitted is, to the best of my knowledge and
belief, true, accurate, and complete. I am aware that there are significant
penalties for submitting false information, including the possibility of fine and
imprisonment for knowing violations.
Construction Stormwater General Permit Page 35
G3. RIGHT OF INSPECTION AND ENTRY
The Permittee must allow an authorized representative of Ecology, upon the presentation of
credentials and such other documents as may be required by law:
A. To enter upon the premises where a discharge is located or where any records are kept
under the terms and conditions of this permit.
B. To have access to and copy, at reasonable times and at reasonable cost, any records
required to be kept under the terms and conditions of this permit.
C. To inspect, at reasonable times, any facilities, equipment (including monitoring and control
equipment), practices, methods, or operations regulated or required under this permit.
D. To sample or monitor, at reasonable times, any substances or parameters at any location for
purposes of assuring permit compliance or as otherwise authorized by the Clean Water Act.
G4. GENERAL PERMIT MODIFICATION AND REVOCATION
This permit may be modified, revoked and reissued, or terminated in accordance with the
provisions of Chapter 173-226 WAC. Grounds for modification, revocation and reissuance, or
termination include, but are not limited to, the following:
A. When a change occurs in the technology or practices for control or abatement of pollutants
applicable to the category of dischargers covered under this permit.
B. When effluent limitation guidelines or standards are promulgated pursuant to the CWA or
Chapter 90.48 RCW, for the category of dischargers covered under this permit.
C. When a water quality management plan containing requirements applicable to the
category of dischargers covered under this permit is approved, or
D. When information is obtained that indicates cumulative effects on the environment from
dischargers covered under this permit are unacceptable.
G5. REVOCATION OF COVERAGE UNDER THE PERMIT
Pursuant to Chapter 43.21B RCW and Chapter 173-226 WAC, the Director may terminate coverage
for any discharger under this permit for cause. Cases where coverage may be terminated include,
but are not limited to, the following:
A. Violation of any term or condition of this permit.
B. Obtaining coverage under this permit by misrepresentation or failure to disclose fully all
relevant facts.
C. A change in any condition that requires either a temporary or permanent reduction or
elimination of the permitted discharge.
D. Failure or refusal of the Permittee to allow entry as required in RCW 90.48.090.
E. A determination that the permitted activity endangers human health or the environment,
or contributes to water quality standards violations.
F. Nonpayment of permit fees or penalties assessed pursuant to RCW 90.48.465 and Chapter
173-224 WAC.
Construction Stormwater General Permit Page 36
G. Failure of the Permittee to satisfy the public notice requirements of WAC 173-226-130(5),
when applicable.
The Director may require any discharger under this permit to apply for and obtain coverage
under an individual permit or another more specific general permit. Permittees who have their
coverage revoked for cause according to WAC 173-226-240 may request temporary coverage
under this permit during the time an individual permit is being developed, provided the request
is made within ninety (90) days from the time of revocation and is submitted along with a
complete individual permit application form.
G6. REPORTING A CAUSE FOR MODIFICATION
The Permittee must submit a new application, or a supplement to the previous application,
whenever a material change to the construction activity or in the quantity or type of discharge is
anticipated which is not specifically authorized by this permit. This application must be submitted
at least sixty (60) days prior to any proposed changes. Filing a request for a permit modification,
revocation and reissuance, or termination, or a notification of planned changes or anticipated
noncompliance does not relieve the Permittee of the duty to comply with the existing permit until
it is modified or reissued.
G7. COMPLIANCE WITH OTHER LAWS AND STATUTES
Nothing in this permit will be construed as excusing the Permittee from compliance with any
applicable federal, state, or local statutes, ordinances, or regulations.
G8. DUTY TO REAPPLY
The Permittee must apply for permit renewal at least 180 days prior to the specified expiration
date of this permit. The Permittee must reapply using the electronic application form (NOI)
available on Ecology’s website. Permittees unable to submit electronically (for example, those who
do not have an internet connection) must contact Ecology to request a waiver and obtain
instructions on how to obtain a paper NOI.
Department of Ecology
Water Quality Program - Construction Stormwater
PO Box 47696
Olympia, WA 98504-7696
G9. REMOVED SUBSTANCE
The Permittee must not re-suspend or reintroduce collected screenings, grit, solids, sludges, filter
backwash, or other pollutants removed in the course of treatment or control of stormwater to the
final effluent stream for discharge to state waters.
G10. DUTY TO PROVIDE INFORMATION
The Permittee must submit to Ecology, within a reasonable time, all information that Ecology may
request to determine whether cause exists for modifying, revoking and reissuing, or terminating
this permit or to determine compliance with this permit. The Permittee must also submit to
Ecology, upon request, copies of records required to be kept by this permit [40 CFR 122.41(h)].
Construction Stormwater General Permit Page 37
G11. OTHER REQUIREMENTS OF 40 CFR
All other requirements of 40 CFR 122.41 and 122.42 are incorporated in this permit by reference.
G12. ADDITIONAL MONITORING
Ecology may establish specific monitoring requirements in addition to those contained in this
permit by administrative order or permit modification.
G13. PENALTIES FOR VIOLATING PERMIT CONDITIONS
Any person who is found guilty of willfully violating the terms and conditions of this permit shall be
deemed guilty of a crime, and upon conviction thereof shall be punished by a fine of up to ten
thousand dollars ($10,000) and costs of prosecution, or by imprisonment at the discretion of the
court. Each day upon which a willful violation occurs may be deemed a separate and additional
violation.
Any person who violates the terms and conditions of a waste discharge permit shall incur, in
addition to any other penalty as provided by law, a civil penalty in the amount of up to ten
thousand dollars ($10,000) for every such violation. Each and every such violation shall be a
separate and distinct offense, and in case of a continuing violation, every day’s continuance shall be
deemed to be a separate and distinct violation.
G14. UPSET
Definition – “Upset” means an exceptional incident in which there is unintentional and temporary
noncompliance with technology-based permit effluent limitations because of factors beyond the
reasonable control of the Permittee. An upset does not include noncompliance to the extent
caused by operational error, improperly designed treatment facilities, inadequate treatment
facilities, lack of preventive maintenance, or careless or improper operation.
An upset constitutes an affirmative defense to an action brought for noncompliance with such
technology-based permit effluent limitations if the requirements of the following paragraph are met.
A Permittee who wishes to establish the affirmative defense of upset must demonstrate, through
properly signed, contemporaneous operating logs or other relevant evidence that: 1) an upset
occurred and that the Permittee can identify the cause(s) of the upset; 2) the permitted facility was
being properly operated at the time of the upset; 3) the Permittee submitted notice of the upset as
required in Special Condition S5.F, and; 4) the Permittee complied with any remedial measures
required under this permit.
In any enforcement proceeding, the Permittee seeking to establish the occurrence of an upset has
the burden of proof.
G15. PROPERTY RIGHTS
This permit does not convey any property rights of any sort, or any exclusive privilege.
G16. DUTY TO COMPLY
The Permittee must comply with all conditions of this permit. Any permit noncompliance
constitutes a violation of the Clean Water Act and is grounds for enforcement action; for permit
termination, revocation and reissuance, or modification; or denial of a permit renewal application.
Construction Stormwater General Permit Page 38
G17. TOXIC POLLUTANTS
The Permittee must comply with effluent standards or prohibitions established under Section
307(a) of the Clean Water Act for toxic pollutants within the time provided in the regulations that
establish those standards or prohibitions, even if this permit has not yet been modified to
incorporate the requirement.
G18. PENALTIES FOR TAMPERING
The Clean Water Act provides that any person who falsifies, tampers with, or knowingly renders
inaccurate any monitoring device or method required to be maintained under this permit shall, upon
conviction, be punished by a fine of not more than $10,000 per violation, or by imprisonment for not
more than two years per violation, or by both. If a conviction of a person is for a violation committed
after a first conviction of such person under this condition, punishment shall be a fine of not more
than $20,000 per day of violation, or imprisonment of not more than four (4) years, or both.
G19. REPORTING PLANNED CHANGES
The Permittee must, as soon as possible, give notice to Ecology of planned physical alterations,
modifications or additions to the permitted construction activity. The Permittee should be aware
that, depending on the nature and size of the changes to the original permit, a new public notice
and other permit process requirements may be required. Changes in activities that require
reporting to Ecology include those that will result in:
A. The permitted facility being determined to be a new source pursuant to 40 CFR 122.29(b).
B. A significant change in the nature or an increase in quantity of pollutants discharged,
including but not limited to: a 20% or greater increase in acreage disturbed by construction
activity.
C. A change in or addition of surface water(s) receiving stormwater or non-stormwater from
the construction activity.
D. A change in the construction plans and/or activity that affects the Permittee’s monitoring
requirements in Special Condition S4.
Following such notice, permit coverage may be modified, or revoked and reissued pursuant to 40
CFR 122.62(a) to specify and limit any pollutants not previously limited. Until such modification is
effective, any new or increased discharge in excess of permit limits or not specifically authorized by
this permit constitutes a violation.
G20. REPORTING OTHER INFORMATION
Where the Permittee becomes aware that it failed to submit any relevant facts in a permit
application, or submitted incorrect information in a permit application or in any report to Ecology,
it must promptly submit such facts or information.
G21. REPORTING ANTICIPATED NON-COMPLIANCE
The Permittee must give advance notice to Ecology by submission of a new application or
supplement thereto at least forty-five (45) days prior to commencement of such discharges, of any
facility expansions, production increases, or other planned changes, such as process modifications,
in the permitted facility or activity which may result in noncompliance with permit limits or
conditions. Any maintenance of facilities, which might necessitate unavoidable interruption of
Construction Stormwater General Permit Page 39
operation and degradation of effluent quality, must be scheduled during non-critical water quality
periods and carried out in a manner approved by Ecology.
G22. REQUESTS TO BE EXCLUDED FROM COVERAGE UNDER THE PERMIT
Any discharger authorized by this permit may request to be excluded from coverage under the
general permit by applying for an individual permit. The discharger must submit to the Director an
application as described in WAC 173-220-040 or WAC 173-216-070, whichever is applicable, with
reasons supporting the request. These reasons will fully document how an individual permit will
apply to the applicant in a way that the general permit cannot. Ecology may make specific requests
for information to support the request. The Director will either issue an individual permit or deny
the request with a statement explaining the reason for the denial. When an individual permit is
issued to a discharger otherwise subject to the construction stormwater general permit, the
applicability of the construction stormwater general permit to that Permittee is automatically
terminated on the effective date of the individual permit.
G23. APPEALS
A. The terms and conditions of this general permit, as they apply to the appropriate class of
dischargers, are subject to appeal by any person within 30 days of issuance of this general
permit, in accordance with Chapter 43.21B RCW, and Chapter 173-226 WAC.
B. The terms and conditions of this general permit, as they apply to an individual discharger,
are appealable in accordance with Chapter 43.21B RCW within 30 days of the effective date
of coverage of that discharger. Consideration of an appeal of general permit coverage of an
individual discharger is limited to the general permit’s applicability or nonapplicability to
that individual discharger.
C. The appeal of general permit coverage of an individual discharger does not affect any other
dischargers covered under this general permit. If the terms and conditions of this general
permit are found to be inapplicable to any individual discharger(s), the matter shall be
remanded to Ecology for consideration of issuance of an individual permit or permits.
G24. SEVERABILITY
The provisions of this permit are severable, and if any provision of this permit, or application of any
provision of this permit to any circumstance, is held invalid, the application of such provision to
other circumstances, and the remainder of this permit shall not be affected thereby.
G25. BYPASS PROHIBITED
A. Bypass Procedures
Bypass, which is the intentional diversion of waste streams from any portion of a treatment
facility, is prohibited for stormwater events below the design criteria for stormwater
management. Ecology may take enforcement action against a Permittee for bypass unless one
of the following circumstances (1, 2, 3 or 4) is applicable.
1. Bypass of stormwater is consistent with the design criteria and part of an approved
management practice in the applicable stormwater management manual.
2. Bypass for essential maintenance without the potential to cause violation of permit limits
or conditions.
Construction Stormwater General Permit Page 40
Bypass is authorized if it is for essential maintenance and does not have the potential to
cause violations of limitations or other conditions of this permit, or adversely impact
public health.
3. Bypass of stormwater is unavoidable, unanticipated, and results in noncompliance of this
permit.
This bypass is permitted only if:
a. Bypass is unavoidable to prevent loss of life, personal injury, or severe property
damage. “Severe property damage” means substantial physical damage to property,
damage to the treatment facilities which would cause them to become inoperable,
or substantial and permanent loss of natural resources which can reasonably be
expected to occur in the absence of a bypass.
b. There are no feasible alternatives to the bypass, such as the use of auxiliary
treatment facilities, retention of untreated wastes, maintenance during normal
periods of equipment downtime (but not if adequate backup equipment should
have been installed in the exercise of reasonable engineering judgment to prevent a
bypass which occurred during normal periods of equipment downtime or
preventative maintenance), or transport of untreated wastes to another treatment
facility.
c. Ecology is properly notified of the bypass as required in Special Condition S5.F of
this permit.
4. A planned action that would cause bypass of stormwater and has the potential to result
in noncompliance of this permit during a storm event.
The Permittee must notify Ecology at least thirty (30) days before the planned date of
bypass. The notice must contain:
a. A description of the bypass and its cause
b. An analysis of all known alternatives which would eliminate, reduce, or mitigate the
need for bypassing.
c. A cost-effectiveness analysis of alternatives including comparative resource damage
assessment.
d. The minimum and maximum duration of bypass under each alternative.
e. A recommendation as to the preferred alternative for conducting the bypass.
f. The projected date of bypass initiation.
g. A statement of compliance with SEPA.
h. A request for modification of water quality standards as provided for in WAC 173-
201A-110, if an exceedance of any water quality standard is anticipated.
i. Steps taken or planned to reduce, eliminate, and prevent reoccurrence of the
bypass.
5. For probable construction bypasses, the need to bypass is to be identified as early in the
planning process as possible. The analysis required above must be considered during
Construction Stormwater General Permit Page 41
preparation of the Stormwater Pollution Prevention Plan (SWPPP) and must be included
to the extent practical. In cases where the probable need to bypass is determined early,
continued analysis is necessary up to and including the construction period in an effort to
minimize or eliminate the bypass.
Ecology will consider the following before issuing an administrative order for this type
bypass:
a. If the bypass is necessary to perform construction or maintenance-related activities
essential to meet the requirements of this permit.
b. If there are feasible alternatives to bypass, such as the use of auxiliary treatment
facilities, retention of untreated wastes, stopping production, maintenance during
normal periods of equipment down time, or transport of untreated wastes to
another treatment facility.
c. If the bypass is planned and scheduled to minimize adverse effects on the public and
the environment.
After consideration of the above and the adverse effects of the proposed bypass and any
other relevant factors, Ecology will approve, conditionally approve, or deny the request.
The public must be notified and given an opportunity to comment on bypass incidents of
significant duration, to the extent feasible. Approval of a request to bypass will be by
administrative order issued by Ecology under RCW 90.48.120.
B. Duty to Mitigate
The Permittee is required to take all reasonable steps to minimize or prevent any discharge or
sludge use or disposal in violation of this permit that has a reasonable likelihood of adversely
affecting human health or the environment.
Construction Stormwater General Permit Page 42
APPENDIX A – DEFINITIONS
AKART is an acronym for “All Known, Available, and Reasonable methods of prevention, control, and
Treatment.” AKART represents the most current methodology that can be reasonably required for
preventing, controlling, or abating the pollutants and controlling pollution associated with a discharge.
Applicable TMDL means a TMDL for turbidity, fine sediment, high pH, or phosphorus, which was
completed and approved by EPA before January 1, 2021, or before the date the operator’s complete
permit application is received by Ecology, whichever is later. TMDLs completed after a complete permit
application is received by Ecology become applicable to the Permittee only if they are imposed through
an administrative order by Ecology, or through a modification of permit coverage.
Applicant means an operator seeking coverage under this permit.
Benchmark means a pollutant concentration used as a permit threshold, below which a pollutant is
considered unlikely to cause a water quality violation, and above which it may. When pollutant
concentrations exceed benchmarks, corrective action requirements take effect. Benchmark values are
not water quality standards and are not numeric effluent limitations; they are indicator values.
Best Management Practices (BMPs) means schedules of activities, prohibitions of practices,
maintenance procedures, and other physical, structural and/or managerial practices to prevent or
reduce the pollution of waters of the State. BMPs include treatment systems, operating procedures, and
practices to control stormwater associated with construction activity, spillage or leaks, sludge or waste
disposal, or drainage from raw material storage.
Buffer means an area designated by a local jurisdiction that is contiguous to and intended to protect a
sensitive area.
Bypass means the intentional diversion of waste streams from any portion of a treatment facility.
Calendar Day A period of 24 consecutive hours starting at 12:00 midnight and ending the following
12:00 midnight.
Calendar Week (same as Week) means a period of seven consecutive days starting at 12:01 a.m. (0:01
hours) on Sunday.
Certified Erosion and Sediment Control Lead (CESCL) means a person who has current certification
through an approved erosion and sediment control training program that meets the minimum training
standards established by Ecology (See BMP C160 in the SWMM).
Chemical Treatment means the addition of chemicals to stormwater and/or authorized non-stormwater
prior to filtration and discharge to surface waters.
Clean Water Act (CWA) means the Federal Water Pollution Control Act enacted by Public Law 92-500, as
amended by Public Laws 95-217, 95-576, 96-483, and 97-117; USC 1251 et seq.
Combined Sewer means a sewer which has been designed to serve as a sanitary sewer and a storm
sewer, and into which inflow is allowed by local ordinance.
Construction Stormwater General Permit Page 43
Common Plan of Development or Sale means a site where multiple separate and distinct construction
activities may be taking place at different times on different schedules and/or by different contractors,
but still under a single plan. Examples include: 1) phased projects and projects with multiple filings or
lots, even if the separate phases or filings/lots will be constructed under separate contract or by
separate owners (e.g., a development where lots are sold to separate builders); 2) a development plan
that may be phased over multiple years, but is still under a consistent plan for long-term development;
3) projects in a contiguous area that may be unrelated but still under the same contract, such as
construction of a building extension and a new parking lot at the same facility; and 4) linear projects
such as roads, pipelines, or utilities. If the project is part of a common plan of development or sale, the
disturbed area of the entire plan must be used in determining permit requirements.
Composite Sample means a mixture of grab samples collected at the same sampling point at different
times, formed either by continuous sampling or by mixing discrete samples. May be "time-composite"
(collected at constant time intervals) or "flow-proportional" (collected either as a constant sample
volume at time intervals proportional to stream flow, or collected by increasing the volume of each
aliquot as the flow increases while maintaining a constant time interval between the aliquots.
Concrete Wastewater means any water used in the production, pouring and/or clean-up of concrete or
concrete products, and any water used to cut, grind, wash, or otherwise modify concrete or concrete
products. Examples include water used for or resulting from concrete truck/mixer/pumper/tool/chute
rinsing or washing, concrete saw cutting and surfacing (sawing, coring, grinding, roughening, hydro-
demolition, bridge and road surfacing). When stormwater comingles with concrete wastewater, the
resulting water is considered concrete wastewater and must be managed to prevent discharge to waters
of the State, including groundwater.
Construction Activity means land disturbing operations including clearing, grading or excavation which
disturbs the surface of the land (including off-site disturbance acreage related to construction-support
activity). Such activities may include road construction, construction of residential houses, office
buildings, or industrial buildings, site preparation, soil compaction, movement and stockpiling of
topsoils, and demolition activity.
Construction Support Activity means off-site acreage that will be disturbed as a direct result of the
construction project and will discharge stormwater. For example, off-site equipment staging yards,
material storage areas, borrow areas, and parking areas.
Contaminant means any hazardous substance that does not occur naturally or occurs at greater than
natural background levels. See definition of “hazardous substance” and WAC 173-340-200.
Contaminated soil means soil which contains contaminants, pollutants, or hazardous substances that do
not occur naturally or occur at levels greater than natural background.
Contaminated groundwater means groundwater which contains contaminants, pollutants, or hazardous
substances that do not occur naturally or occur at levels greater than natural background.
Demonstrably Equivalent means that the technical basis for the selection of all stormwater BMPs is
documented within a SWPPP, including:
1. The method and reasons for choosing the stormwater BMPs selected.
2. The pollutant removal performance expected from the BMPs selected.
Construction Stormwater General Permit Page 44
3. The technical basis supporting the performance claims for the BMPs selected, including any
available data concerning field performance of the BMPs selected.
4. An assessment of how the selected BMPs will comply with state water quality standards.
5. An assessment of how the selected BMPs will satisfy both applicable federal technology-based
treatment requirements and state requirements to use all known, available, and reasonable
methods of prevention, control, and treatment (AKART).
Department means the Washington State Department of Ecology.
Detention means the temporary storage of stormwater to improve quality and/or to reduce the mass
flow rate of discharge.
Dewatering means the act of pumping groundwater or stormwater away from an active construction site.
Director means the Director of the Washington State Department of Ecology or his/her authorized
representative.
Discharger means an owner or operator of any facility or activity subject to regulation under Chapter
90.48 RCW or the Federal Clean Water Act.
Domestic Wastewater means water carrying human wastes, including kitchen, bath, and laundry wastes
from residences, buildings, industrial establishments, or other places, together with such groundwater
infiltration or surface waters as may be present.
Ecology means the Washington State Department of Ecology.
Engineered Soils means the use of soil amendments including, but not limited, to Portland cement
treated base (CTB), cement kiln dust (CKD), or fly ash to achieve certain desirable soil characteristics.
Equivalent BMPs means operational, source control, treatment, or innovative BMPs which result in
equal or better quality of stormwater discharge to surface water or to groundwater than BMPs selected
from the SWMM.
Erosion means the wearing away of the land surface by running water, wind, ice, or other geological
agents, including such processes as gravitational creep.
Erosion and Sediment Control BMPs means BMPs intended to prevent erosion and sedimentation, such as
preserving natural vegetation, seeding, mulching and matting, plastic covering, filter fences, sediment traps,
and ponds. Erosion and sediment control BMPs are synonymous with stabilization and structural BMPs.
Federal Operator is an entity that meets the definition of “Operator” in this permit and is either any
department, agency or instrumentality of the executive, legislative, and judicial branches of the Federal
government of the United States, or another entity, such as a private contractor, performing
construction activity for any such department, agency, or instrumentality.
Final Stabilization (same as fully stabilized or full stabilization) means the completion of all soil
disturbing activities at the site and the establishment of permanent vegetative cover, or equivalent
permanent stabilization measures (such as pavement, riprap, gabions, or geotextiles) which will prevent
erosion. See the applicable Stormwater Management Manual for more information on vegetative cover
expectations and equivalent permanent stabilization measures.
Construction Stormwater General Permit Page 45
Groundwater means water in a saturated zone or stratum beneath the land surface or a surface
waterbody.
Hazardous Substance means any dangerous or extremely hazardous waste as defined in RCW
70.105.010 (5) and (6), or any dangerous or extremely dangerous waste as designated by rule under
chapter 70.105 RCW; any hazardous sub-stance as defined in RCW 70.105.010(14) or any hazardous
substance as defined by rule under chapter 70.105 RCW; any substance that, on the effective date of
this section, is a hazardous substance under section 101(14) of the federal cleanup law, 42U.S.C., Sec.
9601(14); petroleum or petroleum products; and any substance or category of substances, including
solid waste decomposition products, determined by the director by rule to present a threat to human
health or the environment if released into the environment. The term hazardous substance does not
include any of the following when contained in an underground storage tank from which there is not a
release: crude oil or any fraction thereof or petroleum, if the tank is in compliance with all applicable
federal, state, and local law.
Injection Well means a well that is used for the subsurface emplacement of fluids. (See Well.)
Jurisdiction means a political unit such as a city, town or county; incorporated for local self-government.
National Pollutant Discharge Elimination System (NPDES) means the national program for issuing,
modifying, revoking and reissuing, terminating, monitoring, and enforcing permits, and imposing and
enforcing pretreatment requirements, under sections 307, 402, 318, and 405 of the Federal Clean Water
Act, for the discharge of pollutants to surface waters of the State from point sources. These permits are
referred to as NPDES permits and, in Washington State, are administered by the Washington State
Department of Ecology.
Notice of Intent (NOI) means the application for, or a request for coverage under this general permit
pursuant to WAC 173-226-200.
Notice of Termination (NOT) means a request for termination of coverage under this general permit as
specified by Special Condition S10 of this permit.
Operator means any party associated with a construction project that meets either of the following two
criteria:
• The party has operational control over construction plans and specifications, including the
ability to make modifications to those plans and specifications; or
• The party has day-to-day operational control of those activities at a project that are necessary to
ensure compliance with a SWPPP for the site or other permit conditions (e.g., they are
authorized to direct workers at a site to carry out activities required by the SWPPP or comply
with other permit conditions).
Permittee means individual or entity that receives notice of coverage under this general permit.
pH means a liquid’s measure of acidity or alkalinity. A pH of 7 is defined as neutral. Large variations
above or below this value are considered harmful to most aquatic life.
pH Monitoring Period means the time period in which the pH of stormwater runoff from a site must be
tested a minimum of once every seven days to determine if stormwater pH is between 6.5 and 8.5.
Construction Stormwater General Permit Page 46
Point Source means any discernible, confined, and discrete conveyance, including but not limited to, any
pipe, ditch, channel, tunnel, conduit, well, discrete fissure, and container from which pollutants are or
may be discharged to surface waters of the State. This term does not include return flows from irrigated
agriculture. (See the Fact Sheet for further explanation)
Pollutant means dredged spoil, solid waste, incinerator residue, filter backwash, sewage, garbage,
domestic sewage sludge (biosolids), munitions, chemical wastes, biological materials, radioactive
materials, heat, wrecked or discarded equipment, rock, sand, cellar dirt, and industrial, municipal, and
agricultural waste. This term does not include sewage from vessels within the meaning of section 312 of
the CWA, nor does it include dredged or fill material discharged in accordance with a permit issued
under section 404 of the CWA.
Pollution means contamination or other alteration of the physical, chemical, or biological properties of
waters of the State; including change in temperature, taste, color, turbidity, or odor of the waters; or
such discharge of any liquid, gaseous, solid, radioactive or other substance into any waters of the State
as will or is likely to create a nuisance or render such waters harmful, detrimental or injurious to the
public health, safety or welfare; or to domestic, commercial, industrial, agricultural, recreational, or
other legitimate beneficial uses; or to livestock, wild animals, birds, fish or other aquatic life.
Process Wastewater means any non-stormwater which, during manufacturing or processing, comes into
direct contact with or results from the production or use of any raw material, intermediate product,
finished product, byproduct, or waste product. If stormwater commingles with process wastewater, the
commingled water is considered process wastewater.
Receiving Water means the waterbody at the point of discharge. If the discharge is to a storm sewer
system, either surface or subsurface, the receiving water is the waterbody to which the storm system
discharges. Systems designed primarily for other purposes such as for groundwater drainage, redirecting
stream natural flows, or for conveyance of irrigation water/return flows that coincidentally convey
stormwater are considered the receiving water.
Representative means a stormwater or wastewater sample which represents the flow and
characteristics of the discharge. Representative samples may be a grab sample, a time-proportionate
composite sample, or a flow proportionate sample. Ecology’s Construction Stormwater Monitoring
Manual provides guidance on representative sampling.
Responsible Corporate Officer for the purpose of signatory authority means: (i) a president, secretary,
treasurer, or vice-president of the corporation in charge of a principal business function, or any other
person who performs similar policy- or decision-making functions for the corporation, or (ii) the
manager of one or more manufacturing, production, or operating facilities, provided, the manager is
authorized to make management decisions which govern the operation of the regulated facility
including having the explicit or implicit duty of making major capital investment recommendations, and
initiating and directing other comprehensive measures to assure long term environmental compliance
with environmental laws and regulations; the manager can ensure that the necessary systems are
established or actions taken to gather complete and accurate information for permit application
requirements; and where authority to sign documents has been assigned or delegated to the manager in
accordance with corporate procedures (40 CFR 122.22).
Sanitary Sewer means a sewer which is designed to convey domestic wastewater.
Construction Stormwater General Permit Page 47
Sediment means the fragmented material that originates from the weathering and erosion of rocks or
unconsolidated deposits, and is transported by, suspended in, or deposited by water.
Sedimentation means the depositing or formation of sediment.
Sensitive Area means a waterbody, wetland, stream, aquifer recharge area, or channel migration zone.
SEPA (State Environmental Policy Act) means the Washington State Law, RCW 43.21C.020, intended to
prevent or eliminate damage to the environment.
Significant Amount means an amount of a pollutant in a discharge that is amenable to available and
reasonable methods of prevention or treatment; or an amount of a pollutant that has a reasonable
potential to cause a violation of surface or groundwater quality or sediment management standards.
Significant Concrete Work means greater than 1000 cubic yards placed or poured concrete or recycled
concrete used over the life of a project.
Significant Contributor of Pollutants means a facility determined by Ecology to be a contributor of a
significant amount(s) of a pollutant(s) to waters of the State of Washington.
Site means the land or water area where any "facility or activity" is physically located or conducted.
Source Control BMPs means physical, structural or mechanical devices or facilities that are intended to
prevent pollutants from entering stormwater. A few examples of source control BMPs are erosion
control practices, maintenance of stormwater facilities, constructing roofs over storage and working
areas, and directing wash water and similar discharges to the sanitary sewer or a dead end sump.
Stabilization means the application of appropriate BMPs to prevent the erosion of soils, such as,
temporary and permanent seeding, vegetative covers, mulching and matting, plastic covering and
sodding. See also the definition of Erosion and Sediment Control BMPs.
Storm Drain means any drain which drains directly into a storm sewer system, usually found along
roadways or in parking lots.
Storm Sewer System means a means a conveyance, or system of conveyances (including roads with
drainage systems, municipal streets, catch basins, curbs, gutters, ditches, manmade channels, or storm
drains designed or used for collecting or conveying stormwater. This does not include systems which are
part of a combined sewer or Publicly Owned Treatment Works (POTW), as defined at 40 CFR 122.2.
Stormwater means that portion of precipitation that does not naturally percolate into the ground or
evaporate, but flows via overland flow, interflow, pipes, and other features of a stormwater drainage
system into a defined surface waterbody, or a constructed infiltration facility.
Stormwater Management Manual (SWMM) or Manual means the technical Manual published by
Ecology for use by local governments that contain descriptions of and design criteria for BMPs to
prevent, control, or treat pollutants in stormwater.
Stormwater Pollution Prevention Plan (SWPPP) means a documented plan to implement measures to
identify, prevent, and control the contamination of point source discharges of stormwater.
Construction Stormwater General Permit Page 48
Surface Waters of the State includes lakes, rivers, ponds, streams, inland waters, salt waters, and all
other surface waters and water courses within the jurisdiction of the state of Washington.
Temporary Stabilization means the exposed ground surface has been covered with appropriate
materials to provide temporary stabilization of the surface from water or wind erosion. Materials
include, but are not limited to, mulch, riprap, erosion control mats or blankets and temporary cover
crops. Seeding alone is not considered stabilization. Temporary stabilization is not a substitute for the
more permanent “final stabilization.”
Total Maximum Daily Load (TMDL) means a calculation of the maximum amount of a pollutant that a
waterbody can receive and still meet state water quality standards. Percentages of the total maximum
daily load are allocated to the various pollutant sources. A TMDL is the sum of the allowable loads of a
single pollutant from all contributing point and nonpoint sources. The TMDL calculations must include a
"margin of safety" to ensure that the waterbody can be protected in case there are unforeseen events
or unknown sources of the pollutant. The calculation must also account for seasonable variation in
water quality.
Transfer of Coverage (TOC) means a request for transfer of coverage under this general permit as
specified by Special Condition S2.A of this permit.
Treatment BMPs means BMPs that are intended to remove pollutants from stormwater. A few examples
of treatment BMPs are detention ponds, oil/water separators, biofiltration, and constructed wetlands.
Transparency means a measurement of water clarity in centimeters (cm), using a 60 cm transparency
tube. The transparency tube is used to estimate the relative clarity or transparency of water by noting
the depth at which a black and white Secchi disc becomes visible when water is released from a value in
the bottom of the tube. A transparency tube is sometimes referred to as a “turbidity tube.”
Turbidity means the clarity of water expressed as nephelometric turbidity units (NTUs) and measured
with a calibrated turbidimeter.
Uncontaminated means free from any contaminant. See definition of “contaminant” and WAC 173-340-200.
Upset means an exceptional incident in which there is unintentional and temporary noncompliance with
technology-based permit effluent limitations because of factors beyond the reasonable control of the
Permittee. An upset does not include noncompliance to the extent caused by operational error,
improperly designed treatment facilities, inadequate treatment facilities, lack of preventive
maintenance, or careless or improper operation.
Waste Load Allocation (WLA) means the portion of a receiving water’s loading capacity that is allocated
to one of its existing or future point sources of pollution. WLAs constitute a type of water quality based
effluent limitation (40 CFR 130.2[h]).
Water-Only Based Shaft Drilling is a shaft drilling process that uses water only and no additives are
involved in the drilling of shafts for construction of building, road, or bridge foundations.
Water Quality means the chemical, physical, and biological characteristics of water, usually with respect
to its suitability for a particular purpose.
Waters of the State includes those waters as defined as "waters of the United States" in 40 CFR Subpart
122.2 within the geographic boundaries of Washington State and "waters of the State" as defined in
Chapter 90.48 RCW, which include lakes, rivers, ponds, streams, inland waters, underground waters, salt
Construction Stormwater General Permit Page 49
waters, and all other surface waters and water courses within the jurisdiction of the state of
Washington.
Well means a bored, drilled or driven shaft, or dug hole whose depth is greater than the largest surface
dimension. (See Injection Well.)
Wheel Wash Wastewater means any water used in, or resulting from the operation of, a tire bath or
wheel wash (BMP C106: Wheel Wash), or other structure or practice that uses water to physically
remove mud and debris from vehicles leaving a construction site and prevent track-out onto roads.
When stormwater comingles with wheel wash wastewater, the resulting water is considered wheel
wash wastewater and must be managed according to Special Condition S9.D.9.
Construction Stormwater General Permit Page 50
APPENDIX B – ACRONYMS
AKART All Known, Available, and Reasonable Methods of Prevention,
Control, and Treatment
BMP Best Management Practice
CESCL Certified Erosion and Sediment Control Lead
CFR Code of Federal Regulations
CKD Cement Kiln Dust
cm Centimeters
CPD Common Plan of Development
CTB Cement-Treated Base
CWA Clean Water Act
DMR Discharge Monitoring Report
EPA Environmental Protection Agency
ERTS Environmental Report Tracking System
ESC Erosion and Sediment Control
FR Federal Register
LID Low Impact Development
NOI Notice of Intent
NOT Notice of Termination
NPDES National Pollutant Discharge Elimination System
NTU Nephelometric Turbidity Unit
RCW Revised Code of Washington
SEPA State Environmental Policy Act
SWMM Stormwater Management Manual
SWPPP Stormwater Pollution Prevention Plan
TMDL Total Maximum Daily Load
UIC Underground Injection Control
USC United States Code
USEPA United States Environmental Protection Agency
WAC Washington Administrative Code
WQ Water Quality
WWHM Western Washington Hydrology Model
Solera Townhomes – New Home Co. Page 38
E. 303(d) List Waterbodies / TMDL Waterbodies Information
Not applicable to this project
Solera Townhomes – New Home Co. Page 39
F. Engineering Calculations
1. Sediment Tank Sizing
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.64
Program License Number: 200410007
Project Simulation Performed on: 10/29/2024 4:00 PM
Report Generation Date: 10/29/2024 4:51 PM
—————————————————————————————————
Input File Name: Solera Phase 2 TESC Sizing.fld
Project Name: Solera Townhomes (Phase 2)
Analysis Title: TESC Sizing
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Full Period of Record Available used for Routing
Climatic Region Number: 3
Precipitation Station : 95004005 Puget West 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 951040 Puget West 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : Ecology Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 3.860 3.860
Area of Links that Include Precip/Evap (acres) 0.000 0.000
Total (acres) 3.860 3.860
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
A/B, Lawn, Flat 1.270
PARKING/FLAT 2.590
----------------------------------------------
Subbasin Total 3.860
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 2
---------- Subbasin : Block C ----------
-------Area (Acres) --------
A/B, Lawn, Flat 0.630
ROADS/FLAT 0.480
ROOF TOPS/FLAT 1.100
SIDEWALKS/FLAT 0.370
----------------------------------------------
Subbasin Total 2.580
---------- Subbasin : Block D ----------
-------Area (Acres) --------
A/B, Lawn, Flat 0.530
ROADS/FLAT 0.250
ROOF TOPS/FLAT 0.430
SIDEWALKS/FLAT 0.070
----------------------------------------------
Subbasin Total 1.280
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: New Copy Lnk1
Link Type: Copy
Downstream Link: None
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 2
Number of Links: 1
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 427.906
_____________________________________
Total: 427.906
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Block C 212.268
Subbasin: Block D 178.575
Link: New Copy Lnk1 0.000
_____________________________________
Total: 390.843
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 2.708 ac-ft/year, Post Developed: 2.474 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: New Copy Lnk1 **********
2-Year Discharge Rate : 1.102 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.43 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.25 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 1219.58
Inflow Volume Including PPT-Evap (ac-ft): 1219.58
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 1219.58
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: New Copy Lnk1
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 1.063 2-Year 1.102
5-Year 1.336 5-Year 1.392
10-Year 1.559 10-Year 1.625
25-Year 1.877 25-Year 1.955
50-Year 2.334 50-Year 2.433
100-Year 2.796 100-Year 2.915
200-Year 2.928 200-Year 3.052
500-Year 3.097 500-Year 3.228
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
729.3 GPM
SETTLEMENT TANK SIZING CALCULATIONS:
Q = 729.3 GPM
t = 90 min hydraulic retention time
V (gal) = Q*t
V (gal) = 729.3 * 90 = 65,637 gal
Block C: (2) 21,000 gal and (1) 9,000 gal settlement tanks proposed
Block D: (1) 21,000 gal settlement tank proposed
Total Proposed Volume = 21,000+21,000+9,000+21,000 = 72,000 gal
Solera Phase 2: Block C and Block D – New Home Co.
Appendix K
Appendix I
Bond Quantity Worksheet
1055 South Grady Way – 6 th Floor | Renton, WA 98057 (425) 430-7200
•
•
Section I: Project Information
•
•
•
Section II: Bond Quantities Worksheets
•
•Section II.a EROSION CONTROL (Stabilization/Erosion Sediment Control (ESC))
•Section II.b TRANSPORTATION (Street and Site Improvements)
•Section II.c DRAINAGE (Drainage and Stormwater Facilities):
•Section II.d WATER - ONLY APPLICABLE IF WATER SERVICE IS PROVIDED BY CITY OF RENTON
•Section II.e SANITARY SEWER - ONLY APPLICABLE IF SEWER SERVICE IS PROVIDED BY CITY OF RENTON
•
•
•
•
•
•
Section III. Bond Worksheet
•
BOND QUANTITY WORKSHEET INSTRUCTIONS
This worksheet is intended to be a "working" copy of the bond quantity worksheet, which will be used throughout all phases of the project, from initial
submittal to project close-out approval.
Submit this workbook, in its entirety, as follows:
The following forms are to be completed by the engineer/developer/applicant as applicable to the project:
The Bond Worksheet form will auto-calculate and auto-populate from the information provided in Section I and Section II.
This section includes all pertinent information for the project
Section II contains a separate spreadsheet TAB for each of the following specialties:
(1) electronic copy (.xlsx format) and (1) hard copy of the entire workbook for civil construction permit submittal. Hard copies are to be included as part
of the Technical Information Report (TIR).
(1) electronic copy (.xlsx format) and (1) hard copy of the entire workbook for final close-out submittal.
This section must be completed in its entirety
Information from this section auto-populates to all other relevant areas of the workbook
This section calculates the required Permit Bond for construction permit issuance as well as the required Maintenance Bond for project close-out
submittals to release the permit bond on a project.
All unit prices include labor, equipment, materials, overhead, profit, and taxes.
Complete the 'Quantity' columns for each of the appropriate section(s). Include existing Right-of-Way (ROW), Future Public Improvements and Private
Improvements.
The 'Quantity Remaining' column is only to be used when a project is under construction. The City allows one (1) bond reduction during the life of the
project with the exception of the maintenance period reduction.
Excel will auto-calculate and auto-populate the relevant fields and subtotals throughout the document. Only the 'Quantity' columns should need
completing.
Additional items not included in the lists can be added under the "write-in" sections. Provide a complete description, cost estimate and unit of measure
for each write-in item.
Note: Private improvements, with the exception of stormwater facilities, are not included in the bond amount calculation, but must be entered on the
form. Stormwater facilities (public and private) are required to be included in the bond amount.
Page 1 of 15
Ref 8-H Bond Quantity Worksheet INSTRUCTIONS
Version: 4/1/2024
Printed 5/30/2025
1055 South Grady Way – 6 th Floor | Renton, WA 98057 (425) 430-7200
Date Prepared:
Name:
PE Registration No:
Firm Name:
Firm Address:
Phone No.
Email Address:
Project Name: Project Owner:
CED Plan # (LUA): Phone:
CED Permit # (C): Address:
Site Address:
Street Intersection: Addt'l Project Owner:
Parcel #(s): Phone:
Address:
Clearing and grading greater than or equal to 5,000 board feet of timber?
Yes/No:NO Water Service Provided by:
If Yes, Provide Forest Practice Permit #:Sewer Service Provided by:
Total Estimated Construction Costs E
A + B + C + D 1,628,050.28$
Estimated Civil Construction Permit - Construction Costs2
Stormwater (Drainage)C 326,259.68$
As outlined in City Ordinance No. 4345, 50% of the plan review and inspection fees are to be paid at Permit Submittal. The balance is due at Permit Issuance.
Significant changes or additional review cycles (beyond 3 cycles) during the review process may result in adjustments to the final review fees.
Roadway (Erosion Control + Transportation)D 407,930.43$
Water A 300,093.21$
Wastewater (Sanitary Sewer)B 593,766.96$
Abbreviated Legal
Description:
2842 NE Sunset Blvd, Renton, WA 98056
1700 NW Gilman Blvd, Suite 220TBD
LUA24-000375 503-899-8170
5/30/2025
Prepared by:
FOR APPROVALProject Phase 1
jeremy.febus@kpff.com
Jeremy Febus
39847
KPFF Consulting Engineers
1601 5th Ave, Suite #1600, Seattle, WA 98101
(206) 622-5822
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
PROJECT INFORMATION
CITY OF RENTON
CITY OF RENTON
1 Select the current project status/phase from the following options:
For Approval - Preliminary Data Enclosed, pending approval from the City;
For Construction - Estimated Data Enclosed, Plans have been approved for contruction by the City;
Project Closeout - Final Costs and Quantities Enclosed for Project Close-out Submittal
Engineer Stamp Required
(all cost estimates must have original wet stamp and signature)
Clearing and Grading Utility Providers
N/A
Project Location and Description Project Owner Information
Solera Townhomes
Issaquah, WA 98027
722780-1785, 722780-1235, 722780-1405
New Home Co.
Page 2 of 15
Ref 8-H Bond Quantity Worksheet SECTION I PROJECT INFORMATION
Version 4/1/2024
Printed 5/30/2025
05/30/2025
10.3%2 All prices include labor, equipment, materials, overhead, profit, and taxes. City of Renton Sales Tax is:
Page 3 of 15
Ref 8-H Bond Quantity Worksheet SECTION I PROJECT INFORMATION
Version 4/1/2024
Printed 5/30/2025
CED Permit #:TBD
Unit
Reference #Price Unit Quantity Cost
Backfill & compaction-embankment ESC-1 7.50$ CY
Check dams, 4" minus rock ESC-2 SWDM 5.4.6.3 90.00$ Each 22 1,980.00
Catch Basin Protection ESC-3 145.00$ Each 28 4,060.00
Crushed surfacing 1 1/4" minus ESC-4 WSDOT 9-03.9(3)110.00$ CY
Ditching ESC-5 10.50$ CY
Excavation-bulk ESC-6 2.30$ CY
Fence, silt ESC-7 SWDM 5.4.3.1 5.00$ LF 584 2,920.00
Fence, Temporary (NGPE)ESC-8 1.75$ LF 2584 4,522.00
Geotextile Fabric ESC-9 3.00$ SY
Hay Bale Silt Trap ESC-10 0.60$ Each
Hydroseeding ESC-11 SWDM 5.4.2.4 0.90$ SY 17785 16,006.50
Interceptor Swale / Dike ESC-12 1.15$ LF 2823 3,246.45
Jute Mesh ESC-13 SWDM 5.4.2.2 4.00$ SY
Level Spreader ESC-14 2.00$ LF
Mulch, by hand, straw, 3" deep ESC-15 SWDM 5.4.2.1 2.90$ SY
Mulch, by machine, straw, 2" deep ESC-16 SWDM 5.4.2.1 2.30$ SY
Piping, temporary, CPP, 6"ESC-17 13.75$ LF
Piping, temporary, CPP, 8"ESC-18 16.00$ LF
Piping, temporary, CPP, 12"ESC-19 20.50$ LF 143 2,931.50
Plastic covering, 6mm thick, sandbagged ESC-20 SWDM 5.4.2.3 4.60$ SY
Rip Rap, machine placed; slopes ESC-21 WSDOT 9-13.1(2)51.00$ CY
Rock Construction Entrance, 50'x15'x1'ESC-22 SWDM 5.4.4.1 2,050.00$ Each
Rock Construction Entrance, 100'x15'x1'ESC-23 SWDM 5.4.4.1 3,675.00$ Each 4 14,700.00
Sediment pond riser assembly ESC-24 SWDM 5.4.5.2 2,525.00$ Each
Sediment trap, 5' high berm ESC-25 SWDM 5.4.5.1 22.00$ LF
Sed. trap, 5' high, riprapped spillway berm section ESC-26 SWDM 5.4.5.1 80.00$ LF
Seeding, by hand ESC-27 SWDM 5.4.2.4 1.15$ SY
Sodding, 1" deep, level ground ESC-28 SWDM 5.4.2.5 9.20$ SY
Sodding, 1" deep, sloped ground ESC-29 SWDM 5.4.2.5 11.50$ SY
TESC Supervisor ESC-30 125.00$ HR
Water truck, dust control ESC-31 SWDM 5.4.7 160.00$ HR
Unit
Reference #Price Unit Quantity Cost
Each 3
Each 1
EROSION/SEDIMENT SUBTOTAL:50,366.45
SALES TAX @ 10.3%5,187.74
EROSION/SEDIMENT TOTAL:55,554.19
(A)
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR EROSION & SEDIMENT CONTROL
Description No.
(A)
Baker Tank (21,000 Gal)
Baker Tank (9,000 Gal)
WRITE-IN-ITEMS
Page 4 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.a EROSION_CONTROL
Version: 4/01/2024
Printed 5/30/2025
CED Permit #:TBD
Existing Future Public Private
Right-of-Way Improvements Improvements
(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
GENERAL ITEMS
Backfill & Compaction- embankment GI-1 7.00$ CY
Backfill & Compaction- trench GI-2 10.25$ CY
Clear/Remove Brush, by hand (SY)GI-3 1.15$ SY
Bollards - fixed GI-4 275.00$ Each
Bollards - removable GI-5 520.00$ Each
Clearing/Grubbing/Tree Removal GI-6 11,475.00$ Acre
Excavation - bulk GI-7 2.30$ CY 7579 17,431.70
Excavation - Trench GI-8 5.75$ CY
Fencing, cedar, 6' high GI-9 23.00$ LF
Fencing, chain link, 4'GI-10 44.00$ LF
Fencing, chain link, vinyl coated, 6' high GI-11 23.00$ LF
Fencing, chain link, gate, vinyl coated, 20' GI-12 1,600.00$ Each
Fill & compact - common barrow GI-13 28.75$ CY
Fill & compact - gravel base GI-14 31.00$ CY
Fill & compact - screened topsoil GI-15 44.75$ CY
Gabion, 12" deep, stone filled mesh GI-16 74.50$ SY
Gabion, 18" deep, stone filled mesh GI-17 103.25$ SY
Gabion, 36" deep, stone filled mesh GI-18 172.00$ SY
Grading, fine, by hand GI-19 2.90$ SY 62 179.80
Grading, fine, with grader GI-20 2.30$ SY
Monuments, 3' Long GI-21 1,025.00$ Each
Sensitive Areas Sign GI-22 8.00$ Each
Sodding, 1" deep, sloped ground GI-23 9.25$ SY
Surveying, line & grade GI-24 975.00$ Day
Surveying, lot location/lines GI-25 2,050.00$ Acre
Topsoil Type A (imported)GI-26 32.75$ CY
Traffic control crew ( 2 flaggers )GI-27 137.75$ HR
Trail, 4" chipped wood GI-28 9.15$ SY
Trail, 4" crushed cinder GI-29 10.25$ SY
Trail, 4" top course GI-30 13.75$ SY
Conduit, 2"GI-31 5.75$ LF
Wall, retaining, concrete GI-32 63.00$ SF
Wall, rockery GI-33 17.25$ SF
SUBTOTAL THIS PAGE:17,611.50
(B)(C)(D)(E)
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR STREET AND SITE IMPROVEMENTS
Quantity Remaining
(Bond Reduction)
(B) (C)
Page 5 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION
Version: 4/1/2024
Printed 5/30/2025
CED Permit #:TBD
Existing Future Public Private
Right-of-Way Improvements Improvements
(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR STREET AND SITE IMPROVEMENTS
Quantity Remaining
(Bond Reduction)
(B) (C)
ROAD IMPROVEMENT/PAVEMENT/SURFACING
AC Grinding, 4' wide machine < 1000sy RI-1 34.50$ SY
AC Grinding, 4' wide machine 1000-2000sy RI-2 18.25$ SY
AC Grinding, 4' wide machine > 2000sy RI-3 11.50$ SY
AC Removal/Disposal RI-4 40.00$ SY
Barricade, Type III ( Permanent )RI-5 64.25$ LF
Guard Rail RI-6 34.50$ LF
Curb & Gutter, rolled RI-7 19.50$ LF
Curb & Gutter, vertical RI-8 14.25$ LF 365 5,201.25
Curb and Gutter, demolition and disposal RI-9 20.50$ LF
Curb, extruded asphalt RI-10 6.25$ LF
Curb, extruded concrete RI-11 8.00$ LF
Sawcut, asphalt, 3" depth RI-12 3.00$ LF
Sawcut, concrete, per 1" depth RI-13 5.00$ LF
Sealant, asphalt RI-14 2.25$ LF
Shoulder, gravel, 4" thick RI-15 17.25$ SY
Sidewalk, 4" thick RI-16 43.50$ SY 31 1,348.50 2479 107,836.50
Sidewalk, 4" thick, demolition and disposal RI-17 37.00$ SY
Sidewalk, 5" thick RI-18 47.00$ SY
Sidewalk, 5" thick, demolition and disposal RI-19 46.00$ SY
Sign, Handicap RI-20 97.00$ Each
Striping, per stall RI-21 8.00$ Each
Striping, thermoplastic, ( for crosswalk )RI-22 3.50$ SF
Striping, 4" reflectorized line RI-23 0.55$ LF
Additional 2.5" Crushed Surfacing RI-24 4.15$ SY
HMA 1/2" Overlay 1.5" RI-25 16.00$ SY
HMA 1/2" Overlay 2"RI-26 20.75$ SY
HMA Road, 2", 4" rock, First 2500 SY RI-27 32.25$ SY 2500 80,625.00
HMA Road, 2", 4" rock, Qty. over 2500SY RI-28 24.00$ SY 227 5,448.00
HMA Road, 4", 6" rock, First 2500 SY RI-29 51.75$ SY
HMA Road, 4", 6" rock, Qty. over 2500 SY RI-30 42.50$ SY
HMA Road, 4", 4.5" ATB RI-31 43.50$ SY
Gravel Road, 4" rock, First 2500 SY RI-32 17.25$ SY
Gravel Road, 4" rock, Qty. over 2500 SY RI-33 11.50$ SY
Thickened Edge RI-34 10.00$ LF
SUBTOTAL THIS PAGE:1,348.50 86,073.00 113,037.75
(B)(C)(D)(E)
Page 6 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION
Version: 4/1/2024
Printed 5/30/2025
CED Permit #:TBD
Existing Future Public Private
Right-of-Way Improvements Improvements
(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR STREET AND SITE IMPROVEMENTS
Quantity Remaining
(Bond Reduction)
(B) (C)
PARKING LOT SURFACING No.
2" AC, 2" top course rock & 4" borrow PL-1 24.00$ SY
2" AC, 1.5" top course & 2.5" base course PL-2 32.00$ SY
4" select borrow PL-3 5.75$ SY
1.5" top course rock & 2.5" base course PL-4 16.00$ SY
SUBTOTAL PARKING LOT SURFACING:
(B)(C)(D)(E)
LANDSCAPING & VEGETATION No.
Street Trees LA-1 300.00$ 138 41,400.00
Median Landscaping LA-2
Right-of-Way Landscaping LA-3
Wetland Landscaping LA-4
SUBTOTAL LANDSCAPING & VEGETATION:41,400.00
(B)(C)(D)(E)
TRAFFIC & LIGHTING No.
Signs TR-1
Street Light System ( # of Poles)TR-2 6,000.00$ Each 10 60,000.00
Traffic Signal TR-3
Traffic Signal Modification TR-4
SUBTOTAL TRAFFIC & LIGHTING:60,000.00
(B)(C)(D)(E)
WRITE-IN-ITEMS
SUBTOTAL WRITE-IN ITEMS:
STREET AND SITE IMPROVEMENTS SUBTOTAL:1,348.50 86,073.00 232,049.25
SALES TAX @ 10.3%138.90 8,865.52 23,901.07
STREET AND SITE IMPROVEMENTS TOTAL:1,487.40 94,938.52 255,950.32
(B)(C)(D)(E)
Page 7 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION
Version: 4/1/2024
Printed 5/30/2025
CED Permit #:TBD
Existing Future Public Private
Right-of-Way Improvements Improvements
(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
DRAINAGE (CPE = Corrugated Polyethylene Pipe, N12 or Equivalent) For Culvert prices, Average of 4' cover was assumed. Assume perforated PVC is same price as solid pipe.)
Access Road, R/D D-1 30.00$ SY
* (CBs include frame and lid)
Beehive D-2 103.00$ Each 10 1,030.00
Through-curb Inlet Framework D-3 460.00$ Each 3 1,380.00
CB Type I D-4 1,725.00$ Each 16 27,600.00 14 24,150.00
CB Type IL D-5 2,000.00$ Each
CB Type II, 48" diameter D-6 3,500.00$ Each 5 17,500.00
for additional depth over 4' D-7 550.00$ FT
CB Type II, 54" diameter D-8 4,075.00$ Each
for additional depth over 4'D-9 570.00$ FT
CB Type II, 60" diameter D-10 4,225.00$ Each
for additional depth over 4'D-11 690.00$ FT
CB Type II, 72" diameter D-12 6,900.00$ Each
for additional depth over 4'D-13 975.00$ FT
CB Type II, 96" diameter D-14 16,000.00$ Each
for additional depth over 4'D-15 1,050.00$ FT
Trash Rack, 12"D-16 400.00$ Each 15 6,000.00
Trash Rack, 15"D-17 470.00$ Each
Trash Rack, 18"D-18 550.00$ Each
Trash Rack, 21"D-19 630.00$ Each
Cleanout, PVC, 4"D-20 170.00$ Each
Cleanout, PVC, 6"D-21 195.00$ Each 19 3,705.00
Cleanout, PVC, 8"D-22 230.00$ Each
Culvert, PVC, 4" D-23 11.50$ LF
Culvert, PVC, 6" D-24 15.00$ LF 334 5,010.00
Culvert, PVC, 8" D-25 17.00$ LF
Culvert, PVC, 12" D-26 26.00$ LF
Culvert, PVC, 15" D-27 40.00$ LF
Culvert, PVC, 18" D-28 47.00$ LF
Culvert, PVC, 24"D-29 65.00$ LF
Culvert, PVC, 30" D-30 90.00$ LF
Culvert, PVC, 36" D-31 150.00$ LF
Culvert, CMP, 8"D-32 22.00$ LF
Culvert, CMP, 12"D-33 33.00$ LF
SUBTOTAL THIS PAGE:46,480.00 39,895.00
(B)(C)(D)(E)
Quantity Remaining
(Bond Reduction) (B)(C)
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR DRAINAGE AND STORMWATER FACILITIES
Page 8 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE
Version: 4/1/2024
Printed 5/30/2025
CED Permit #:TBD
Existing Future Public Private
Right-of-Way Improvements Improvements
(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
Quantity Remaining
(Bond Reduction) (B)(C)
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR DRAINAGE AND STORMWATER FACILITIES
DRAINAGE (Continued)
Culvert, CMP, 15"D-34 40.00$ LF
Culvert, CMP, 18"D-35 47.00$ LF
Culvert, CMP, 24"D-36 64.00$ LF
Culvert, CMP, 30"D-37 90.00$ LF
Culvert, CMP, 36"D-38 150.00$ LF
Culvert, CMP, 48"D-39 218.00$ LF
Culvert, CMP, 60"D-40 310.00$ LF
Culvert, CMP, 72"D-41 400.00$ LF
Culvert, Concrete, 8"D-42 48.00$ LF
Culvert, Concrete, 12"D-43 55.00$ LF
Culvert, Concrete, 15"D-44 89.00$ LF
Culvert, Concrete, 18"D-45 100.00$ LF
Culvert, Concrete, 24"D-46 120.00$ LF
Culvert, Concrete, 30"D-47 145.00$ LF
Culvert, Concrete, 36"D-48 175.00$ LF
Culvert, Concrete, 42"D-49 200.00$ LF
Culvert, Concrete, 48"D-50 235.00$ LF
Culvert, CPE Triple Wall, 6" D-51 16.00$ LF
Culvert, CPE Triple Wall, 8" D-52 18.00$ LF
Culvert, CPE Triple Wall, 12" D-53 27.00$ LF
Culvert, CPE Triple Wall, 15" D-54 40.00$ LF
Culvert, CPE Triple Wall, 18" D-55 47.00$ LF
Culvert, CPE Triple Wall, 24" D-56 64.00$ LF
Culvert, CPE Triple Wall, 30" D-57 90.00$ LF
Culvert, CPE Triple Wall, 36" D-58 149.00$ LF
Culvert, LCPE, 6"D-59 69.00$ LF
Culvert, LCPE, 8"D-60 83.00$ LF 303 25,149.00 31 2,573.00
Culvert, LCPE, 12"D-61 96.00$ LF 851 81,696.00
Culvert, LCPE, 15"D-62 110.00$ LF
Culvert, LCPE, 18"D-63 124.00$ LF
Culvert, LCPE, 24"D-64 138.00$ LF
Culvert, LCPE, 30"D-65 151.00$ LF
Culvert, LCPE, 36"D-66 165.00$ LF
Culvert, LCPE, 48"D-67 179.00$ LF
Culvert, LCPE, 54"D-68 193.00$ LF
SUBTOTAL THIS PAGE:106,845.00 2,573.00
(B)(C)(D)(E)
Page 9 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE
Version: 4/1/2024
Printed 5/30/2025
CED Permit #:TBD
Existing Future Public Private
Right-of-Way Improvements Improvements
(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
Quantity Remaining
(Bond Reduction) (B)(C)
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR DRAINAGE AND STORMWATER FACILITIES
DRAINAGE (Continued)
Culvert, LCPE, 60"D-69 206.00$ LF
Culvert, LCPE, 72"D-70 220.00$ LF
Culvert, HDPE, 6"D-71 48.00$ LF
Culvert, HDPE, 8"D-72 60.00$ LF
Culvert, HDPE, 12"D-73 85.00$ LF
Culvert, HDPE, 15"D-74 122.00$ LF
Culvert, HDPE, 18"D-75 158.00$ LF
Culvert, HDPE, 24"D-76 254.00$ LF
Culvert, HDPE, 30"D-77 317.00$ LF
Culvert, HDPE, 36"D-78 380.00$ LF
Culvert, HDPE, 48"D-79 443.00$ LF
Culvert, HDPE, 54"D-80 506.00$ LF
Culvert, HDPE, 60"D-81 570.00$ LF
Culvert, HDPE, 72"D-82 632.00$ LF
Pipe, Polypropylene, 6"D-83 96.00$ LF
Pipe, Polypropylene, 8"D-84 100.00$ LF
Pipe, Polypropylene, 12"D-85 100.00$ LF
Pipe, Polypropylene, 15"D-86 103.00$ LF
Pipe, Polypropylene, 18"D-87 106.00$ LF
Pipe, Polypropylene, 24"D-88 119.00$ LF
Pipe, Polypropylene, 30"D-89 136.00$ LF
Pipe, Polypropylene, 36"D-90 185.00$ LF
Pipe, Polypropylene, 48"D-91 260.00$ LF
Pipe, Polypropylene, 54"D-92 381.00$ LF
Pipe, Polypropylene, 60"D-93 504.00$ LF
Pipe, Polypropylene, 72"D-94 625.00$ LF
Culvert, DI, 6"D-95 70.00$ LF
Culvert, DI, 8"D-96 101.00$ LF
Culvert, DI, 12"D-97 121.00$ LF
Culvert, DI, 15"D-98 148.00$ LF
Culvert, DI, 18"D-99 175.00$ LF
Culvert, DI, 24"D-100 200.00$ LF
Culvert, DI, 30"D-101 227.00$ LF
Culvert, DI, 36"D-102 252.00$ LF
Culvert, DI, 48"D-103 279.00$ LF
Culvert, DI, 54"D-104 305.00$ LF
Culvert, DI, 60"D-105 331.00$ LF
Culvert, DI, 72"D-106 357.00$ LF
SUBTOTAL THIS PAGE:
(B)(C)(D)(E)
Page 10 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE
Version: 4/1/2024
Printed 5/30/2025
CED Permit #:TBD
Existing Future Public Private
Right-of-Way Improvements Improvements
(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
Quantity Remaining
(Bond Reduction) (B)(C)
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR DRAINAGE AND STORMWATER FACILITIES
Specialty Drainage Items
Ditching SD-1 10.90$ CY
Flow Dispersal Trench (1,436 base+)SD-3 32.00$ LF
French Drain (3' depth)SD-4 30.00$ LF
Geotextile, laid in trench, polypropylene SD-5 3.40$ SY
Mid-tank Access Riser, 48" dia, 6' deep SD-6 2,300.00$ Each
Pond Overflow Spillway SD-7 18.25$ SY
Restrictor/Oil Separator, 12"SD-8 1,320.00$ Each
Restrictor/Oil Separator, 15"SD-9 1,550.00$ Each
Restrictor/Oil Separator, 18"SD-10 1,950.00$ Each
Riprap, placed SD-11 48.20$ CY
Tank End Reducer (36" diameter)SD-12 1,375.00$ Each
Infiltration pond testing SD-13 143.00$ HR
Permeable Pavement SD-14
Permeable Concrete Sidewalk SD-15
Culvert, Box __ ft x __ ft SD-16
SUBTOTAL SPECIALTY DRAINAGE ITEMS:
(B)(C)(D)(E)
STORMWATER FACILITIES (Include Flow Control and Water Quality Facility Summary Sheet and Sketch)
Detention Pond SF-1 Each
Detention Tank SF-2 Each
Detention Vault SF-3 Each
Infiltration Pond SF-4 Each
Infiltration Tank SF-5 Each
Infiltration Vault SF-6 Each
Infiltration Trenches SF-7 Each
Basic Biofiltration Swale SF-8 Each
Wet Biofiltration Swale SF-9 Each
Wetpond SF-10 Each
Wetvault SF-11 Each
Sand Filter SF-12 Each
Sand Filter Vault SF-13 Each
Linear Sand Filter SF-14 Each
Proprietary Facility SF-15 Each
Bioretention Facility SF-16 10,000.00$ Each 10 100,000.00
SUBTOTAL STORMWATER FACILITIES:100,000.00
(B)(C)(D)(E)
Page 11 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE
Version: 4/1/2024
Printed 5/30/2025
CED Permit #:TBD
Existing Future Public Private
Right-of-Way Improvements Improvements
(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
Quantity Remaining
(Bond Reduction) (B)(C)
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR DRAINAGE AND STORMWATER FACILITIES
WRITE-IN-ITEMS (INCLUDE ON-SITE BMPs)
WI-1
WI-2
WI-3
WI-4
WI-5
WI-6
WI-7
WI-8
WI-9
WI-10
WI-11
WI-12
WI-13
WI-14
WI-15
SUBTOTAL WRITE-IN ITEMS:
DRAINAGE AND STORMWATER FACILITIES SUBTOTAL:153,325.00 142,468.00
SALES TAX @ 10.3%15,792.48 14,674.20
DRAINAGE AND STORMWATER FACILITIES TOTAL:169,117.48 157,142.20
(B) (C) (D) (E)
Page 12 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE
Version: 4/1/2024
Printed 5/30/2025
CED Permit #:TBD
Existing Future Public Private
Right-of-Way Improvements Improvements
(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
Connection to Existing Watermain W-1 3,400.00$ Each 4 13,600.00
Ductile Iron Watermain, CL 52, 4 Inch Diameter W-2 58.00$ LF
Ductile Iron Watermain, CL 52, 6 Inch Diameter W-3 65.00$ LF
Ductile Iron Watermain, CL 52, 8 Inch Diameter W-4 75.00$ LF
Ductile Iron Watermain, CL 52, 10 Inch Diameter W-5 80.00$ LF
Ductile Iron Watermain, CL 52, 12 Inch Diameter W-6 145.00$ LF 1476 214,020.00
Gate Valve, 4 inch Diameter W-7 1,225.00$ Each
Gate Valve, 6 inch Diameter W-8 1,350.00$ Each
Gate Valve, 8 Inch Diameter W-9 1,550.00$ Each
Gate Valve, 10 Inch Diameter W-10 2,100.00$ Each
Gate Valve, 12 Inch Diameter W-11 2,500.00$ Each 17 42,500.00
Fire Hydrant Assembly W-12 5,000.00$ Each
Permanent Blow-Off Assembly W-13 1,950.00$ Each 1 1,950.00
Air-Vac Assembly, 2-Inch Diameter W-14 3,050.00$ Each
Air-Vac Assembly, 1-Inch Diameter W-15 1,725.00$ Each
Compound Meter Assembly 3-inch Diameter W-16 9,200.00$ Each
Compound Meter Assembly 4-inch Diameter W-17 10,500.00$ Each
Compound Meter Assembly 6-inch Diameter W-18 11,500.00$ Each
Pressure Reducing Valve Station 8-inch to 10-inch W-19 23,000.00$ Each
WATER SUBTOTAL:13,600.00 258,470.00
SALES TAX @ 10.3%1,400.80 26,622.41
WATER TOTAL:15,000.80 285,092.41
(B) (C) (D) (E)
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR WATER
Quantity Remaining
(Bond Reduction)
(B)(C)
Page 13 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.d WATER
Version: 4/1/2024
Printed 5/30/2025
CED Permit #:TBD
Existing Future Public Private
Right-of-Way Improvements Improvements
(D) (E)
Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost
Clean Outs SS-1 1,150.00$ Each 2 2,300.00 90 103,500.00
Grease Interceptor, 500 gallon SS-2 9,200.00$ Each
Grease Interceptor, 1000 gallon SS-3 11,500.00$ Each
Grease Interceptor, 1500 gallon SS-4 17,200.00$ Each
Side Sewer Pipe, PVC. 4 Inch Diameter SS-5 92.00$ LF
Side Sewer Pipe, PVC. 6 Inch Diameter SS-6 110.00$ LF 1208 132,880.00
Sewer Pipe, PVC, 8 inch Diameter SS-7 120.00$ LF 1462 175,440.00
Sewer Pipe, PVC, 12 Inch Diameter SS-8 144.00$ LF
Sewer Pipe, DI, 8 inch Diameter SS-9 130.00$ LF
Sewer Pipe, DI, 12 Inch Diameter SS-10 150.00$ LF
Manhole, 48 Inch Diameter SS-11 6,900.00$ Each 2 13,800.00 16 110,400.00
Manhole, 54 Inch Diameter SS-13 6,800.00$ Each
Manhole, 60 Inch Diameter SS-15 7,600.00$ Each
Manhole, 72 Inch Diameter SS-17 10,600.00$ Each
Manhole, 96 Inch Diameter SS-19 16,000.00$ Each
Pipe, C-900, 12 Inch Diameter SS-21 205.00$ LF
Outside Drop SS-24 1,700.00$ LS
Inside Drop SS-25 1,150.00$ LS
Sewer Pipe, PVC, ____ Inch Diameter SS-26
Lift Station (Entire System)SS-27 LS
SANITARY SEWER SUBTOTAL:13,800.00 288,140.00 236,380.00
SALES TAX @ 10.3%1,421.40 29,678.42 24,347.14
SANITARY SEWER TOTAL:15,221.40 317,818.42 260,727.14
(B) (C) (D) (E)
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
FOR SANITARY SEWER
Quantity Remaining
(Bond Reduction) (B)(C)
Page 14 of 15
Ref 8-H Bond Quantity Worksheet SECTION II.e SANITARY SEWER
Version: 4/1/2024
Printed 5/30/2025
1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430-7200
Date:
Name: Project Name:
PE Registration No: CED Plan # (LUA):
Firm Name:CED Permit # (C):
Firm Address: Site Address:
Phone No. Parcel #(s):
Email Address:Project Phase:
Site Restoration/Erosion Sediment Control Subtotal (a)
Existing Right-of-Way Improvements Subtotal (b) (b)31,709.60$
Future Public Improvements Subtotal (c)697,849.35$
Stormwater & Drainage Facilities (Public & Private) Subtotal (d) (d)326,259.68$
(e)
(f)
Site Restoration
Existing Right-of-Way and Storm Drainage Improvements
Maintenance Bond 211,163.72$
Bond Reduction 2
Construction Permit Bond Amount 3
Minimum Bond Amount is $10,000.00
1 Estimate Only - May involve multiple and variable components, which will be established on an individual basis by Development Engineering.
2 The City of Renton allows one request only for bond reduction prior to the maintenance period. Reduction of not more than 70% of the original bond amount, provided that the remaining 30% will
cover all remaining items to be constructed.
3 Required Bond Amounts are subject to review and modification by Development Engineering.
* Note: The word BOND as used in this document means any financial guarantee acceptable to the City of Renton.
** Note: All prices include labor, equipment, materials, overhead, profit, and taxes.
EST1
((b) + (c) + (d)) x 20%
-$
MAINTENANCE BOND */**
(after final acceptance of construction)
55,554.19$
31,709.60$
373,824.07$
55,554.19$
-$
326,259.68$
-$
429,378.27$
P
(a) x 100%
SITE IMPROVEMENT BOND QUANTITY WORKSHEET
BOND CALCULATIONS
5/30/2025
Jeremy Febus
39847
KPFF Consulting Engineers
R
((b x 150%) + (d x 100%))
S
(e) x 150% + (f) x 100%
Bond Reduction: Existing Right-of-Way Improvements (Quantity
Remaining)2
Bond Reduction: Stormwater & Drainage Facilities (Quantity
Remaining)2
T
(P +R - S)
Prepared by: Project Information
CONSTRUCTION BOND AMOUNT */**
(prior to permit issuance)
(206) 622-5822
jeremy.febus@kpff.com
Solera Townhomes
LUA24-000375
2842 NE Sunset Blvd, Renton, WA 98056
722780-1785, 722780-1235, 722780-1405
FOR APPROVAL
TBD
1601 5th Ave, Suite #1600, Seattle, WA 98101
Page 15 of 15
Ref 8-H Bond Quantity Worksheet SECTION III. BOND WORKSHEET
Version: 4/1/2024
Printed 5/30/2025
Solera Phase 2: Block C and Block D – New Home Co.
Appendix H
Appendix J
Operations and Maintenance Manual
Solera Townhomes
Renton, WA
Operations and Maintenance Manual
May 2025 Draft
Solera Townhomes – Operations and Maintenance Manual
i
Operations and Maintenance Manual
May 2025
Owner:
Dalton Arndt
Solera Manager, LLC
10900 NE 8th Street, Suite 1200
Bellevue, WA 98004
Applicant:
Richard Rawlings
TNHC Washington, LLC
1700 NW Gilman Blvd, Suite 220
Issaquah, WA 98207
(206) 344-8606
Prepared by:
Michelle Freeman, PE
Monica Regan, PE
KPFF Consulting Engineers
1601 Fifth Avenue, Suite 1600
Seattle, WA 98101
(206) 622-5822
KPFF Project No. 2400283
KPFF Consulting Engineers
ii
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Solera Townhomes – Operations and Maintenance Manual
iii
Table of Contents
1. Operations and Maintenance Guidelines ................................................................................................ 1
Appendices
Appendix A – 2016 King County Surface Water Design Manual Operations and Maintenance Procedures
KPFF Consulting Engineers
iv
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Solera Townhomes – Operations and Maintenance Manual
1
1. Operations and Maintenance Guidelines
Requirements for the operations and maintenance of the storm drainage infrastructure associated with the
Solera Townhome project are provided in this manual. The project consists of the construction of storm
drainage infrastructure for 90 townhome units and associated alley and utility improvements on Block C and D
of the Solera Short Plat. Phase 1 comprised the construction of Blocks A and B, which is complete and
included the clearing of Blocks C and D. The phase 2 site is roughly 4-acres.
Several designs and technologies will be implemented on the phase 2 site to manage stormwater. These
include: collection and conveyance of stormwater and bioretention planters. Each of these facilities and
technologies needs to be operated and maintained, and this manual provides direction on how to do so.
Collection and conveyance of stormwater infrastructure is described as a network of storm drainage pipes and
facilities such as inlets and catch basins, which collect and route stormwater throughout the site. Operation
and maintenance procedures of the collection and conveyance of stormwater shall be in accordance with the
2016 King County Surface Water Design Manual Appendix A No. 5 Catch Basins and Manholes, and Appendix
A No. 6 Conveyance Pipes and Ditches.
A large portion of the site runoff will be routed to bioretention planters located along the alley frontages on site.
Stormwater will be treated in the bioretention planters and then routed to the proposed conveyance system in
the streets. Operation and maintenance procedures for the bioretention facility shall be in accordance with the
2016 King County Surface Water Design manual Appendix A No. 31 Bioretention BMP.
Managing the hardscape and landscaping at Solera is an important part of keeping storm drainage
infrastructure and technology functional. Maintenance and operation procedures for the grounds on-site shall
be in accordance with the 2016 King County Surface Water Design Manual Appendix A No. 11 Grounds
(Landscaping).
Solera Townhomes – Operations and Maintenance Manual
Appendix A
Appendix A
2016 King County Surface Water Design Manual Operations and Maintenance
Procedures
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL, APPENDIX A
APPENDIX A
MAINTENANCE REQUIREMENTS FOR FLOW CONTROL,
CONVEYANCE, AND WATER QUALITY FACILITIES
This appendix contains the maintenance requirements for the following typical stormwater control and water quality facilities and components (ctrl/click ► to follow the link):
► No. 1 – Detention Ponds (p. A-2)
► No. 2 – Infiltration Facilities (p. A-3)
► No. 3 – Detention Tanks and Vaults (p. A-5)
► No. 4 – Control Structure/Flow Restrictor (p. A-7)
► No. 5 – Catch Basins and Manholes (p. A-9)
► No. 6 – Conveyance Pipes and Ditches (p. A-11)
► No. 7 – Debris Barriers (e.g., Trash Racks) (p. A-12)
► No. 8 – Energy Dissipaters (p. A- 13)
► No. 9 – Fencing (p. A-14)
► No. 10 – Gates/Bollards/Access Barriers (p. A-15)
► No. 11 – Grounds (Landscaping) (p. A-16)
► No. 12 – Access Roads (p. A-17)
► No. 13 – Basic Bioswale (grass) (p. A-18)
► No. 14 – Wet Bioswale (p. A-19)
► No. 15 – Filter Strip (p. A-20)
► No. 16 – Wetpond (p. A-21)
► No. 17 – Wetvault (p. A-23)
► No. 18 – Stormwater Wetland (p. A-24)
► No. 19 – Sand Filter Pond (p. A-26)
► No. 20 – Sand Filter Vault (p. A-28)
► No. 21 – Stormfilter (Cartridge Type) (p. A-30)
► No. 22 – Baffle Oil/Water Separator (p. A-32)
► No. 23 – Coalescing Plate Oil/Water Separator (p. A-33)
► No. 24 – Catch Basin Insert (p. A-34)
► No. 25 – Drywell BMP (p. A-35)
► No. 26 – Gravel Filled Infiltration Trench BMP (p. A-35)
► No. 27 – Gravel Filled Dispersion Trench BMP (p. A-36)
► No. 28 – Native Vegetated Surface / Native Vegetated Landscape BMP (p. A-37)
► No. 29 – Perforated Pipe Connections BMP (p. A-37)
► No. 30 – Permeable Pavement BMP (p. A-38)
► No. 31 – Bioretention BMP (p. A-39)
► No. 32 – RainWater Harvesting BMP (p. A- 40)
► No. 33 – Rock Pad BMP (p. A-40)
► No. 34 – Sheet Flow BMP (p. A-40)
► No. 35 – Splash Block BMP (p. A-41)
► No. 36 – Vegetated Roof BMP (p. A-42)
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-1
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 1 – DETENTION PONDS
Maintenance Component Defect or Problem Conditions When Maintenance Is Needed Results Expected When Maintenance Is Performed
Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping.
Trash and debris cleared from site.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious
vegetation where County personnel or the public might normally be.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants
present other than a surface oil film.
Grass/groundcover Grass or groundcover exceeds 18 inches in
height.
Grass or groundcover mowed to a
height no greater than 6 inches.
Top or Side Slopes of Dam, Berm or Embankment
Rodent holes Any evidence of rodent holes if facility is acting as a dam or berm, or any evidence of water piping through dam or berm via rodent holes.
Rodents removed or destroyed and dam or berm repaired.
Tree growth Tree growth threatens integrity of slopes, does not allow maintenance access, or interferes with maintenance activity. If trees are not a threat or not interfering with access or maintenance, they do not need to be removed.
Trees do not hinder facility performance or maintenance activities.
Erosion Eroded damage over 2 inches deep where cause of damage is still present or where there is
potential for continued erosion. Any erosion observed on a compacted slope.
Slopes stabilized using appropriate erosion control measures. If erosion
is occurring on compacted slope, a licensed civil engineer should be consulted to resolve source of erosion.
Settlement Any part of a dam, berm or embankment that has settled 4 inches lower than the design
elevation.
Top or side slope restored to design dimensions. If settlement is
significant, a licensed civil engineer should be consulted to determine the cause of the settlement.
Storage Area Sediment accumulation Accumulated sediment that exceeds 10% of the designed pond depth. Sediment cleaned out to designed pond shape and depth; pond reseeded if necessary to control erosion.
Liner damaged (If Applicable) Liner is visible or pond does not hold water as designed. Liner repaired or replaced.
Inlet/Outlet Pipe. Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering
at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
Emergency Overflow/Spillway Tree growth Tree growth impedes flow or threatens stability of spillway. Trees removed.
Rock missing Only one layer of rock exists above native soil in area five square feet or larger or any exposure of native soil on the spillway.
Spillway restored to design standards.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-2
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 2 – INFILTRATION FACILITIES
Maintenance Component Defect or Problem Conditions When Maintenance Is Needed Results Expected When Maintenance Is Performed
Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping.
Trash and debris cleared from site.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious
vegetation where County personnel or the public might normally be.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants
present other than a surface oil film.
Grass/groundcover Grass or groundcover exceeds 18 inches in
height.
Grass or groundcover mowed to a
height no greater than 6 inches.
Infiltration Pond, Top or Side Slopes of Dam, Berm or Embankment
Rodent holes Any evidence of rodent holes if facility is acting as a dam or berm, or any evidence of water piping through dam or berm via rodent holes.
Rodents removed or destroyed and dam or berm repaired.
Tree growth Tree growth threatens integrity of dams, berms or slopes, does not allow maintenance access, or interferes with maintenance activity. If trees are not a threat to dam, berm, or embankment integrity or not interfering with access or
maintenance, they do not need to be removed.
Trees do not hinder facility performance or maintenance activities.
Erosion Eroded damage over 2 inches deep where cause
of damage is still present or where there is potential for continued erosion. Any erosion observed on a compacted slope.
Slopes stabilized using appropriate
erosion control measures. If erosion is occurring on compacted slope, a licensed civil engineer should be consulted to resolve source of
erosion.
Settlement Any part of a dam, berm or embankment that
has settled 4 inches lower than the design elevation.
Top or side slope restored to design
dimensions. If settlement is significant, a licensed civil engineer should be consulted to determine the cause of the settlement.
Infiltration Pond, Tank, Vault, Trench, or Small Basin Storage Area
Sediment accumulation If two inches or more sediment is present or a percolation test indicates facility is working at or less than 90% of design.
Facility infiltrates as designed.
Liner damaged (If Applicable) Liner is visible or pond does not hold water as designed. Liner repaired or replaced.
Infiltration Tank Structure Plugged air vent Any blockage of the vent. Tank or vault freely vents.
Tank bent out of shape Any part of tank/pipe is bent out of shape more than 10% of its design shape. Tank repaired or replaced to design.
Gaps between sections, damaged joints or cracks or
tears in wall
A gap wider than ½-inch at the joint of any tank sections or any evidence of soil particles entering the tank at a joint or through a wall.
No water or soil entering tank through joints or walls.
Infiltration Vault Structure Damage to wall, frame, bottom, and/or top slab
Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is not structurally sound.
Vault is sealed and structurally sound.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-3
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 2 – INFILTRATION FACILITIES
Maintenance Component Defect or Problem Conditions When Maintenance Is Needed Results Expected When Maintenance Is Performed
Inlet/Outlet Pipes Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering
at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place.
Any open manhole requires immediate maintenance.
Manhole access covered.
Locking mechanism
not working
Mechanism cannot be opened by one
maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person.
Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access.
Large access doors/plate Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can opened as designed.
Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat; covers access opening completely.
Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate.
Infiltration Pond, Tank, Vault, Trench, or Small Basin Filter Bags
Plugged Filter bag more than 1/2 full. Replace filter bag or redesign system.
Infiltration Pond, Tank, Vault, Trench, or Small Basin Pre-settling Ponds and Vaults
Sediment accumulation 6" or more of sediment has accumulated. Pre-settling occurs as designed
Infiltration Pond, Rock Filter Plugged High water level on upstream side of filter remains for extended period of time or little or no
water flows through filter during heavy rain storms.
Rock filter replaced evaluate need for filter and remove if not
necessary.
Infiltration Pond Emergency Overflow Spillway
Rock missing Only one layer of rock exists above native soil in area five square feet or larger, or any exposure of native soil at the top of out flow path of spillway. Rip-rap on inside slopes need not be
replaced.
Spillway restored to design standards.
Tree growth Tree growth impedes flow or threatens stability of spillway. Trees removed.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-4
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 3 – DETENTION TANKS AND VAULTS
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping.
Trash and debris cleared from site.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious
vegetation where County personnel or the public might normally be.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants
present other than a surface oil film.
Grass/groundcover Grass or groundcover exceeds 18 inches in
height.
Grass or groundcover mowed to a
height no greater than 6 inches.
Tank or Vault Storage Area Trash and debris Any trash and debris accumulated in vault or tank (includes floatables and non-floatables). No trash or debris in vault.
Sediment accumulation Accumulated sediment depth exceeds 10% of the diameter of the storage area for ½ length of storage vault or any point depth exceeds 15% of diameter. Example: 72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than ½ length of tank.
All sediment removed from storage area.
Tank Structure Plugged air vent Any blockage of the vent. Tank or vault freely vents.
Tank bent out of
shape
Any part of tank/pipe is bent out of shape more
than 10% of its design shape.
Tank repaired or replaced to design.
Gaps between
sections, damaged joints or cracks or tears in wall
A gap wider than ½-inch at the joint of any tank
sections or any evidence of soil particles entering the tank at a joint or through a wall.
No water or soil entering tank
through joints or walls.
Vault Structure Damage to wall, frame, bottom, and/or top slab
Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is
not structurally sound.
Vault is sealed and structurally sound.
Inlet/Outlet Pipes Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering
at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-5
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 3 – DETENTION TANKS AND VAULTS
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place.
Any open manhole requires immediate maintenance.
Manhole access covered.
Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts
cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person.
Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access.
Large access doors/plate Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can opened as designed.
Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat; covers access opening completely.
Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-6
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed
Structure Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the structure opening or is blocking capacity of the structure by more than 10%.
No Trash or debris blocking or potentially blocking entrance to structure.
Trash or debris in the structure that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin.
No trash or debris in the structure.
Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents.
Sediment Sediment exceeds 60% of the depth from the bottom of the structure to the invert of the lowest
pipe into or out of the structure or the bottom of the FROP-T section or is within 6 inches of the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section.
Sump of structure contains no sediment.
Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb.
Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks.
Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab.
Frame is sitting flush on top slab.
Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering structure
through cracks, or maintenance person judges that structure is unsound.
Structure is sealed and structurally sound.
Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering structure through cracks.
No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe.
Settlement/ misalignment Structure has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards.
Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of inlet/outlet pipes.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations.
Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Ladder rungs missing or unsafe Ladder is unsafe due to missing rungs, misalignment, rust, cracks, or sharp edges. Ladder meets design standards and allows maintenance person safe access.
FROP-T Section Damage T section is not securely attached to structure wall and outlet pipe structure should support at
least 1,000 lbs of up or down pressure.
T section securely attached to wall and outlet pipe.
Structure is not in upright position (allow up to 10% from plumb). Structure in correct position.
Connections to outlet pipe are not watertight or show signs of deteriorated grout. Connections to outlet pipe are water tight; structure repaired or replaced and works as designed.
Any holes—other than designed holes—in the
structure.
Structure has no holes other than
designed holes.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-7
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed
Cleanout Gate Damaged or missing Cleanout gate is missing. Replace cleanout gate.
Cleanout gate is not watertight. Gate is watertight and works as designed.
Gate cannot be moved up and down by one maintenance person. Gate moves up and down easily and is watertight.
Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed.
Orifice Plate Damaged or missing Control device is not working properly due to missing, out of place, or bent orifice plate. Plate is in place and works as designed.
Obstructions Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed.
Overflow Pipe Obstructions Any trash or debris blocking (or having the potential of blocking) the overflow pipe. Pipe is free of all obstructions and works as designed.
Deformed or damaged lip Lip of overflow pipe is bent or deformed. Overflow pipe does not allow overflow at an elevation lower than design
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
Metal Grates (If Applicable) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards.
Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal
Damaged or missing Grate missing or broken member(s) of the grate. Grate is in place and meets design standards.
Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent
maintenance.
Cover/lid protects opening to structure.
Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not
work.
Mechanism opens with proper tools.
Cover/lid difficult to
Remove
One maintenance person cannot remove
cover/lid after applying 80 lbs. of lift.
Cover/lid can be removed and
reinstalled by one maintenance person.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-8
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 5 – CATCH BASINS AND MANHOLES
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed
Structure Sediment Sediment exceeds 60% of the depth from the bottom of the catch basin to the invert of the lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin.
Sump of catch basin contains no sediment.
Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the catch basin
by more than 10%.
No Trash or debris blocking or potentially blocking entrance to catch basin.
Trash or debris in the catch basin that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin.
No trash or debris in the catch
basin.
Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane).
No dead animals or vegetation present within catch basin.
Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents.
Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb.
Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks.
Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab.
Frame is sitting flush on top slab.
Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering catch
basin through cracks, or maintenance person judges that catch basin is unsound.
Catch basin is sealed and is structurally sound.
Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks.
No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe.
Settlement/ misalignment Catch basin has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards.
Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the catch basin at the joint of the inlet/outlet
pipes.
No cracks more than ¼-inch wide at the joint of inlet/outlet pipes.
Contaminants and
pollution
Any evidence of contaminants or pollution such
as oil, gasoline, concrete slurries or paint.
Materials removed and disposed of
according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-9
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 5 – CATCH BASINS AND MANHOLES
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed
Metal Grates (Catch Basins) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards.
Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal
Damaged or missing Grate missing or broken member(s) of the grate.
Any open structure requires urgent maintenance.
Grate is in place and meets design standards.
Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance.
Cover/lid protects opening to structure.
Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to Remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-10
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 6 – CONVEYANCE PIPES AND DITCHES
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Pipes Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% of the diameter of the pipe. Water flows freely through pipes.
Vegetation/roots Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations.
Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Damage to protective coating or corrosion Protective coating is damaged; rust or corrosion is weakening the structural integrity of any part of pipe.
Pipe repaired or replaced.
Damaged Any dent that decreases the cross section area of pipe by more than 20% or is determined to
have weakened structural integrity of the pipe.
Pipe repaired or replaced.
Ditches Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Trash and debris cleared from ditches.
Sediment accumulation Accumulated sediment that exceeds 20% of the design depth. Ditch cleaned/flushed of all sediment and debris so that it matches design.
Noxious weeds Any noxious or nuisance vegetation which may
constitute a hazard to County personnel or the public.
Noxious and nuisance vegetation
removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations.
Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Vegetation Vegetation that reduces free movement of water through ditches. Water flows freely through ditches.
Erosion damage to slopes Any erosion observed on a ditch slope. Slopes are not eroding.
Rock lining out of place or missing (If Applicable)
One layer or less of rock exists above native soil area 5 square feet or more, any exposed native soil.
Replace rocks to design standards.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-11
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 7 – DEBRIS BARRIERS (E.G., TRASH RACKS)
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed.
Site Trash and debris Trash or debris plugging more than 20% of the area of the barrier. Barrier clear to receive capacity flow.
Sediment accumulation Sediment accumulation of greater than 20% of the area of the barrier Barrier clear to receive capacity flow.
Structure Cracked broken or loose Structure which bars attached to is damaged - pipe is loose or cracked or concrete structure is
cracked, broken of loose.
Structure barrier attached to is sound.
Bars Bar spacing Bar spacing exceeds 6 inches. Bars have at most 6 inches spacing.
Damaged or missing bars Bars are bent out of shape more than 3 inches. Bars in place with no bends more than ¾ inch.
Bars are missing or entire barrier missing. Bars in place according to design.
Bars are loose and rust is causing 50% deterioration to any part of barrier. Repair or replace barrier to design standards.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-12
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 8 – ENERGY DISSIPATERS
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed.
Site Trash and debris Trash and/or debris accumulation. Dissipater clear of trash and/or debris.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Rock Pad Missing or moved Rock Only one layer of rock exists above native soil in area five square feet or larger or any exposure of native soil.
Rock pad prevents erosion.
Dispersion Trench Pipe plugged with sediment Accumulated sediment that exceeds 20% of the design depth. Pipe cleaned/flushed so that it matches design.
Not discharging water properly Visual evidence of water discharging at concentrated points along trench (normal
condition is a “sheet flow” of water along trench).
Water discharges from feature by sheet flow.
Perforations plugged. Over 1/4 of perforations in pipe are plugged with debris or sediment. Perforations freely discharge flow.
Water flows out top of “distributor” catch basin.
Water flows out of distributor catch basin during any storm less than the design storm. No flow discharges from distributor catch basin.
Receiving area over-
saturated
Water in receiving area is causing or has
potential of causing landslide problems.
No danger of landslides.
Gabions Damaged mesh Mesh of gabion broken, twisted or deformed so
structure is weakened or rock may fall out.
Mesh is intact, no rock missing.
Corrosion Gabion mesh shows corrosion through more
than ¼ of its gage.
All gabion mesh capable of
containing rock and retaining designed form.
Collapsed or deformed baskets Gabion basket shape deformed due to any cause. All gabion baskets intact, structure stands as designed.
Missing rock Any rock missing that could cause gabion to loose structural integrity. No rock missing.
Manhole/Chamber Worn or damaged post, baffles or side of chamber
Structure dissipating flow deteriorates to ½ or original size or any concentrated worn spot exceeding one square foot which would make structure unsound.
Structure is in no danger of failing.
Damage to wall, frame, bottom, and/or top slab
Cracks wider than ½-inch or any evidence of soil entering the structure through cracks, or maintenance inspection personnel determines that the structure is not structurally sound.
Manhole/chamber is sealed and structurally sound.
Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes.
No soil or water enters and no water
discharges at the joint of inlet/outlet pipes.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-13
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 9 – FENCING
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Site Erosion or holes under fence Erosion or holes more than 4 inches high and 12-18 inches wide permitting access through an opening under a fence.
No access under the fence.
Wood Posts, Boards and Cross Members Missing or damaged parts Missing or broken boards, post out of plumb by more than 6 inches or cross members broken No gaps on fence due to missing or broken boards, post plumb to within 1½ inches, cross members sound.
Weakened by rotting or insects Any part showing structural deterioration due to rotting or insect damage All parts of fence are structurally sound.
Damaged or failed post foundation Concrete or metal attachments deteriorated or unable to support posts. Post foundation capable of supporting posts even in strong wind.
Metal Posts, Rails and Fabric Damaged parts Post out of plumb more than 6 inches. Post plumb to within 1½ inches.
Top rails bent more than 6 inches. Top rail free of bends greater than 1 inch.
Any part of fence (including post, top rails, and fabric) more than 1 foot out of design alignment. Fence is aligned and meets design standards.
Missing or loose tension wire. Tension wire in place and holding fabric.
Deteriorated paint or
protective coating
Part or parts that have a rusting or scaling
condition that has affected structural adequacy.
Structurally adequate posts or parts
with a uniform protective coating.
Openings in fabric Openings in fabric are such that an 8-inch
diameter ball could fit through.
Fabric mesh openings within 50% of
grid size.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-14
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 10 – GATES/BOLLARDS/ACCESS BARRIERS
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Chain Link Fencing Gate Damaged or missing members Missing gate. Gates in place.
Broken or missing hinges such that gate cannot be easily opened and closed by a maintenance person.
Hinges intact and lubed. Gate is working freely.
Gate is out of plumb more than 6 inches and more than 1 foot out of design alignment. Gate is aligned and vertical.
Missing stretcher bar, stretcher bands, and ties. Stretcher bar, bands, and ties in place.
Locking mechanism does not lock gate Locking device missing, no-functioning or does not link to all parts. Locking mechanism prevents opening of gate.
Openings in fabric Openings in fabric are such that an 8-inch diameter ball could fit through. Fabric mesh openings within 50% of grid size.
Bar Gate Damaged or missing cross bar Cross bar does not swing open or closed, is missing or is bent to where it does not prevent vehicle access.
Cross bar swings fully open and closed and prevents vehicle access.
Locking mechanism does not lock gate Locking device missing, no-functioning or does not link to all parts. Locking mechanism prevents opening of gate.
Support post damaged Support post does not hold cross bar up. Cross bar held up preventing vehicle access into facility.
Bollards Damaged or missing Bollard broken, missing, does not fit into support hole or hinge broken or missing. No access for motorized vehicles to get into facility.
Does not lock Locking assembly or lock missing or cannot be attached to lock bollard in place. No access for motorized vehicles to get into facility.
Boulders Dislodged Boulders not located to prevent motorized vehicle access. No access for motorized vehicles to get into facility.
Circumvented Motorized vehicles going around or between boulders. No access for motorized vehicles to get into facility.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-15
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 11 – GROUNDS (LANDSCAPING)
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Site Trash or litter Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping.
Trash and debris cleared from site.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious
vegetation where County personnel or the public might normally be.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants
present other than a surface oil film.
Grass/groundcover Grass or groundcover exceeds 18 inches in
height.
Grass or groundcover mowed to a
height no greater than 6 inches.
Trees and Shrubs Hazard Any tree or limb of a tree identified as having a potential to fall and cause property damage or threaten human life. A hazard tree identified by a qualified arborist must be removed as soon as possible.
No hazard trees in facility.
Damaged Limbs or parts of trees or shrubs that are split or broken which affect more than 25% of the total foliage of the tree or shrub.
Trees and shrubs with less than 5% of total foliage with split or broken limbs.
Trees or shrubs that have been blown down or knocked over. No blown down vegetation or knocked over vegetation. Trees or shrubs free of injury.
Trees or shrubs which are not adequately
supported or are leaning over, causing exposure of the roots.
Tree or shrub in place and
adequately supported; dead or diseased trees removed.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-16
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 12 – ACCESS ROADS
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed
Site Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet (i.e., trash and debris would fill up one standards size garbage can).
Roadway drivable by maintenance vehicles.
Debris which could damage vehicle tires or prohibit use of road. Roadway drivable by maintenance vehicles.
Contaminants and
pollution
Any evidence of contaminants or pollution such
as oil, gasoline, concrete slurries or paint.
Materials removed and disposed of
according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Blocked roadway Any obstruction which reduces clearance above road surface to less than 14 feet. Roadway overhead clear to 14 feet high.
Any obstruction restricting the access to a 10- to 12 foot width for a distance of more than 12 feet
or any point restricting access to less than a 10 foot width.
At least 12-foot of width on access road.
Road Surface Erosion, settlement, potholes, soft spots, ruts
Any surface defect which hinders or prevents maintenance access. Road drivable by maintenance vehicles.
Vegetation on road surface Trees or other vegetation prevent access to facility by maintenance vehicles. Maintenance vehicles can access facility.
Shoulders and Ditches Erosion Erosion within 1 foot of the roadway more than 8 inches wide and 6 inches deep. Shoulder free of erosion and matching the surrounding road.
Weeds and brush Weeds and brush exceed 18 inches in height or hinder maintenance access. Weeds and brush cut to 2 inches in height or cleared in such a way as to allow maintenance access.
Modular Grid Pavement Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if
appropriate. No contaminants present other than a surface oil film.
Damaged or missing Access surface compacted because of broken on missing modular block. Access road surface restored so road infiltrates.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-17
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 13 – BASIC BIOSWALE (GRASS)
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed
Site Trash and debris Any trash and/or debris accumulated on the bioswale site. No trash or debris on the bioswale site.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Swale Section Sediment accumulation Sediment depth exceeds 2 inches in 10% of the swale treatment area. No sediment deposits in grass treatment area of the bioswale.
Sediment inhibits grass growth over 10% of swale length. Grass growth not inhibited by sediment.
Sediment inhibits even spreading of flow. Flow spreads evenly through swale
Erosion/scouring Eroded or scoured swale bottom due to channelization or high flows. No eroded or scoured areas in bioswale. Cause of erosion or scour addressed.
Poor vegetation coverage Grass is sparse or bare or eroded patches occur in more than 10% of the swale bottom. Swale has no bare spots and grass is thick and healthy.
Grass too tall Grass excessively tall (greater than 10 inches), grass is thin or nuisance weeds and other vegetation have taken over.
Grass is between 3 and 4 inches tall, thick and healthy. No clippings left in swale. No nuisance vegetation present.
Excessive shade
Grass growth is poor because sunlight does not reach swale. Health grass growth or swale converted to a wet bioswale.
Constant baseflow Continuous flow through the swale, even when it has been dry for weeks or an eroded, muddy
channel has formed in the swale bottom.
Baseflow removed from swale by a low-flow pea-gravel drain or
bypassed around the swale.
Standing water Water pools in the swale between storms or
does not drain freely.
Swale freely drains and there is no
standing water in swale between storms.
Channelization Flow concentrates and erodes channel through swale. No flow channels in swale.
Flow Spreader Concentrated flow Flow from spreader not uniformly distributed across entire swale width. Flows are spread evenly over entire swale width.
Inlet/Outlet Pipe Sediment
accumulation
Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet
pipes (includes floatables and non-floatables).
No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the
inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at
the joint of the inlet/outlet pipe.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-18
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 14 – WET BIOSWALE
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance Is Performed
Site Trash and debris Any trash and/or debris accumulated at the site. No trash or debris at the site.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Swale Section Sediment accumulation Sediment depth exceeds 2 inches in 10% of the swale treatment area. No sediment deposits in treatment area.
Erosion/scouring Eroded or scoured swale bottom due to channelization or high flows. No eroded or scoured areas in bioswale. Cause of erosion or scour addressed.
Water depth Water not retained to a depth of about 4 inches during the wet season. Water depth of 4 inches through out swale for most of wet season.
Vegetation ineffective Vegetation sparse, does not provide adequate filtration or crowded out by very dense clumps of cattail or nuisance vegetation.
Wetland vegetation fully covers bottom of swale and no cattails or nuisance vegetation present.
Insufficient water Wetland vegetation dies due to lack of water. Wetland vegetation remains healthy (may require converting to grass lined bioswale
Flow Spreader Concentrated flow Flow from spreader not uniformly distributed across entire swale width. Flows are spread evenly over entire swale width.
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-19
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 15 – FILTER STRIP
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance Is Performed
Site Trash and debris Any trash and debris accumulated on the filter strip site. Filter strip site free of any trash or debris
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Grass Strip Sediment accumulation Sediment accumulation on grass exceeds 2 inches depth. No sediment deposits in treatment area.
Erosion/scouring Eroded or scoured swale bottom due to channelization or high flows. No eroded or scoured areas in bioswale. Cause of erosion or scour addressed.
Grass too tall Grass excessively tall (greater than 10 inches), grass is thin or nuisance weeds and other
vegetation have taken over.
Grass is between 3 and 4 inches tall, thick and healthy. No clippings
left in swale. No nuisance vegetation present.
Vegetation ineffective Grass has died out, become excessively tall (greater than 10 inches) or nuisance vegetation is taking over.
Grass is healthy, less than 9 inches high and no nuisance vegetation present.
Flow Spreader Concentrated flow Flow from spreader not uniformly distributed across entire swale width. Flows are spread evenly over entire swale width.
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering
at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-20
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 16 – WETPOND
Maintenance Component Defect or Problem Condition When Maintenance is Needed
Results Expected When Maintenance Is Performed
Site Trash and debris Any trash and debris accumulated on the wetpond site. Wetpond site free of any trash or debris.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if
appropriate. No contaminants present other than a surface oil film.
Grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches.
Side Slopes of Dam, Berm, internal berm or Embankment
Rodent holes Any evidence of rodent holes if facility is acting as a dam or berm, or any evidence of water piping through dam or berm via rodent holes.
Rodents removed or destroyed and dam or berm repaired.
Tree growth Tree growth threatens integrity of dams, berms or slopes, does not allow maintenance access, or interferes with maintenance activity. If trees are not a threat to dam, berm or embankment integrity, are not interfering with access or maintenance or leaves do not cause a plugging problem they do not need to be removed.
Trees do not hinder facility performance or maintenance activities.
Erosion Eroded damage over 2 inches deep where cause of damage is still present or where there is potential for continued erosion. Any erosion
observed on a compacted slope.
Slopes stabilized using appropriate erosion control measures. If erosion is occurring on compacted slope, a
licensed civil engineer should be consulted to resolve source of erosion.
Top or Side Slopes of Dam, Berm, internal berm or
Embankment
Settlement Any part of a dam, berm or embankment that has settled 4 inches lower than the design elevation.
Top or side slope restored to design dimensions. If settlement is significant, a licensed civil engineer
should be consulted to determine the cause of the settlement.
Irregular surface on internal berm Top of berm not uniform and level. Top of berm graded to design elevation.
Pond Areas Sediment accumulation (except first wetpool cell)
Accumulated sediment that exceeds 10% of the designed pond depth. Sediment cleaned out to designed pond shape and depth.
Sediment accumulation (first wetpool cell)
Sediment accumulations in pond bottom that exceeds the depth of sediment storage (1 foot) plus 6 inches.
Sediment storage contains no sediment.
Liner damaged (If Applicable) Liner is visible or pond does not hold water as designed. Liner repaired or replaced.
Water level (all wetpool cells) Cell level(s) drops more than 12 inches in any 7-day period. Cell level(s) drops less than 12 inches in any 7-day period.
Algae mats (first wetpool cell) Algae mats develop over more than 10% of the water surface should be removed. Algae mats removed (usually in the late summer before Fall rains, especially in Sensitive Lake Protection Areas.)
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-21
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 16 – WETPOND
Maintenance Component Defect or Problem Condition When Maintenance is Needed
Results Expected When Maintenance Is Performed
Design planting and vegetation survival and maintenance
Sparse or dying design planting, or when design plantings are not thriving across 80% or more of the design vegetated areas within the pond; invasive vegetation e.g., cattails
Design plantings and vegetation are thriving and appropriately spaced across 80% or more of the design vegetated areas within the pond; invasives removed including root clumps
Gravity Drain Inoperable valve Valve will not open and close. Valve opens and closes normally.
Valve won’t seal Valve does not seal completely. Valve completely seals closed.
Emergency Overflow Spillway Tree growth Tree growth impedes flow or threatens stability of spillway. Trees removed.
Rock missing Only one layer of rock exists above native soil in area five square feet or larger, or any exposure of native soil at the top of out flow path of spillway. Rip-rap on inside slopes need not be
replaced.
Spillway restored to design standards.
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering
at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-22
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 17 – WETVAULT
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed
Site Trash and debris Trash and debris accumulated on facility site. Trash and debris removed from facility site.
Treatment Area
Trash and debris Any trash and debris accumulated in vault (includes floatables and non-floatables). No trash or debris in vault.
Sediment accumulation Sediment accumulation in vault bottom exceeds the depth of the sediment zone plus 6 inches. No sediment in vault.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations.
Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Vault Structure Damage to wall, frame, bottom, and/or top slab
Cracks wider than ½-inch, any evidence of soil entering the structure through cracks, vault does not retain water or qualified inspection personnel
determines that the vault is not structurally sound.
Vault is sealed and structurally sound.
Baffles damaged Baffles corroding, cracking, warping and/or showing signs of failure or baffle cannot be removed.
Repair or replace baffles or walls to specifications.
Ventilation Ventilation area blocked or plugged. No reduction of ventilation area exists.
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
Gravity Drain Inoperable valve Valve will not open and close. Valve opens and closes normally.
Valve won’t seal Valve does not seal completely. Valve completely seals closed.
Access Manhole Access cover/lid damaged or difficult to open
Access cover/lid cannot be easily opened by one person. Corrosion/deformation of cover/lid. Access cover/lid can be opened by one person.
Locking mechanism
not working
Mechanism cannot be opened by one
maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person.
Access doors/plate has gaps, doesn't
cover completely
Large access doors not flat and/or access opening not completely covered. Doors close flat; covers access opening completely.
Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate.
Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-23
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 18 – STORMWATER WETLAND
Maintenance Component Defect or Problem Condition When Maintenance is Needed
Results Expected When Maintenance Is Performed
Site Trash and debris Trash and debris accumulated on facility site. Trash and debris removed from facility site.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if
appropriate. No contaminants present other than a surface oil film.
Grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches.
Side Slopes of Dam, Berm, internal berm or Embankment
Rodent holes Any evidence of rodent holes if facility is acting as a dam or berm, or any evidence of water piping through dam or berm via rodent holes.
Rodents removed or destroyed and dam or berm repaired.
Tree growth Tree growth threatens integrity of dams, berms or slopes, does not allow maintenance access, or interferes with maintenance activity. If trees are not a threat to dam, berm, or embankment integrity or not interfering with access or maintenance, they do not need to be removed.
Trees do not hinder facility performance or maintenance activities.
Erosion Eroded damage over 2 inches deep where cause of damage is still present or where there is potential for continued erosion. Any erosion observed on a compacted slope.
Slopes stabilized using appropriate erosion control measures. If erosion is occurring on compacted slope, a licensed civil engineer should be
consulted to resolve source of erosion.
Top or Side Slopes of Dam, Berm, internal berm or Embankment
Settlement Any part of a dam, berm or embankment that has settled 4 inches lower than the design elevation.
Top or side slope restored to design dimensions. If settlement is significant, a licensed civil engineer should be consulted to determine
the cause of the settlement.
Irregular surface on internal berm Top of berm not uniform and level. Top of berm graded flat to design elevation.
Pond Areas
Sediment accumulation (first cell/forebay)
Sediment accumulations in pond bottom that exceeds the depth of sediment storage (1 foot) plus 6 inches.
Sediment storage contains no sediment.
Sediment
accumulation (wetland cell)
Accumulated sediment that exceeds 10% of the
designed pond depth.
Sediment cleaned out to designed
pond shape and depth.
Liner damaged (If Applicable) Liner is visible or pond does not hold water as designed. Liner repaired or replaced.
Water level (first cell/forebay) Cell level drops more than 12 inches in any 7-day period. Cell level drops no more than 12 inches in any 7-day period.
Water level (wetland cell) Cell does not retain water for at least 10 months of the year or wetland plants are not surviving. Water retained at least 10 months of the year or wetland plants are surviving.
Algae mats (first cell/forebay) Algae mats develop over more than 10% of the water surface should be removed. Algae mats removed (usually in the late summer before Fall rains, especially in Sensitive Lake Protection Areas.)
4/24/2016 2016 Surface Water Design Manual – Appendix A A-24
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 18 – STORMWATER WETLAND
Maintenance Component Defect or Problem Condition When Maintenance is Needed
Results Expected When Maintenance Is Performed
Vegetation Vegetation dead, dying, or overgrown (cattails) or not meeting original planting specifications across more than 20% of the entire design vegetated area within the pond.
Plants in wetland cell surviving across 80% or more of the entire design vegetated area within the pond and not interfering with wetland function.
Gravity Drain Inoperable valve Valve will not open and close. Valve opens and closes normally.
Valve won’t seal Valve does not seal completely. Valve completely seals closed.
Emergency
Overflow Spillway
Tree growth Tree growth impedes flow or threatens stability of
spillway.
Trees removed.
Rock missing Only one layer of rock exists above native soil in
area five square feet or larger, or any exposure of native soil at the top of out flow path of spillway. Rip-rap on inside slopes need not be replaced.
Spillway restored to design
standards.
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-25
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 19 – SAND FILTER POND
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance Is Performed
Site Trash and debris Trash and debris accumulated on facility site. Trash and debris removed from facility site.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if
appropriate. No contaminants present other than a surface oil film.
Grass/groundcover (not in the treatment area)
Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches.
Pre-Treatment (if applicable) Sediment accumulation Sediment accumulations in pond bottom that exceeds the depth of sediment storage (1 foot) plus 6 inches.
Sediment storage contains no sediment.
Liner damaged (If Applicable) Liner is visible or pond does not hold water as designed. Liner repaired or replaced.
Water level Cell empty, doesn't hold water. Water retained in first cell for most of the year.
Algae mats Algae mats develop over more than 10% of the water surface should be removed. Algae mats removed (usually in the late summer before Fall rains, especially in Sensitive Lake
Protection Areas.)
Pond Area Sediment
accumulation
Sediment or crust depth exceeds ½-inch over 10
% of surface area of sand filter.
No sediment or crust deposit on
sand filter that would impede permeability of the filter section.
Grass (if applicable) Grass becomes excessively tall (greater than 6 inches) or when nuisance weeds and other vegetation start to take over or thatch build up occurs.
Mow vegetation and/or remove nuisance vegetation.
Side Slopes of Pond Rodent holes Any evidence of rodent holes if facility is acting as a dam or berm, or any evidence of water piping through dam or berm via rodent holes.
Rodents removed or destroyed and dam or berm repaired.
Tree growth Tree growth threatens integrity of dams, berms or slopes, does not allow maintenance access,
or interferes with maintenance activity. If trees are not a threat to dam, berm, or embankment integrity or not interfering with access or maintenance, they do not need to be removed.
Trees do not hinder facility performance or maintenance
activities.
Erosion Eroded damage over 2 inches deep where cause of damage is still present or where there is
potential for continued erosion. Any erosion observed on a compacted slope.
Slopes stabilized using appropriate erosion control measures. If erosion
is occurring on compacted slope, a licensed civil engineer should be consulted to resolve source of erosion.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-26
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 19 – SAND FILTER POND
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance Is Performed
Sand Filter Media Plugging Drawdown of water through the sand filter media, takes longer than 24 hours, and/or flow through the overflow pipes occurs frequently. A sieve analysis of >4% -100 or >2% -200 requires replacing sand filter media.
Sand filter media surface is aerated or the surface is scraped and replaced, and drawdown rate is normal.
Prolonged flows Sand is saturated for prolonged periods of time (several weeks) and does not dry out between storms due to continuous base flow or prolonged
flows from detention facilities.
Excess flows bypassed or confined to small portion of filter media surface.
Short circuiting Flows become concentrated over one section of
the sand filter rather than dispersed or drawdown rate of pool exceeds 12 inches per hour.
Flow and percolation of water
through the sand filter is uniform and dispersed across the entire filter area and drawdown rate is normal.
Media thickness Sand thickness is less than 18 inches. Rebuild sand thickness to a minimum of 18 inches.
Underdrains and Clean-Outs Sediment/debris Underdrains or clean-outs partially plugged or filled with sediment and/or debris. Junction box/cleanout wyes not watertight.
Underdrains and clean-outs free of sediment and debris and are watertight.
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
Rock Pad Missing or out of place Only one layer of rock exists above native soil in area five square feet or larger, or any exposure
of native soil.
Rock pad restored to design standards.
Flow spreader Concentrated flow Flow from spreader not uniformly distributed
across sand filter.
Flows spread evenly over sand filter.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-27
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 20 – SAND FILTER VAULT
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed
Site Trash and debris Trash and debris accumulated on facility site. Trash and debris removed from facility site.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if
appropriate. No contaminants present other than a surface oil film.
Grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches.
Pre-Treatment Chamber Sediment accumulation Sediment accumulation exceeds the depth of the sediment zone plus 6 inches. Sediment storage contains no sediment.
Sand Filter Media Sediment accumulation Sediment depth exceeds ½-inch on sand filter media. Sand filter freely drains at normal rate.
Trash and debris Trash and debris accumulated in vault (floatables and non-floatables). No trash or debris in vault.
Plugging Drawdown of water through the sand filter media,
takes longer than 24 hours, and/or flow through the overflow pipes occurs frequently. A sieve analysis of >4% -100 or >2% -200 requires replacing sand filter media.
Sand filter media drawdown rate is
normal.
Short circuiting Seepage or flow occurs along the vault walls and corners. Sand eroding near inflow area.
Cleanout wyes are not watertight.
Sand filter media section re-laid and compacted along perimeter of vault
to form a semi-seal. Erosion protection added to dissipate force of incoming flow and curtail erosion.
Vault Structure Damaged to walls, frame, bottom and/or top slab.
Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is not structurally sound.
Vault replaced or repaired to provide complete sealing of the structure.
Ventilation Ventilation area blocked or plugged. No reduction of ventilation area exists.
Underdrains and Cleanouts Sediment/debris Underdrains or clean-outs partially plugged, filled with sediment and/or debris or not watertight. Underdrains and clean-outs free of sediment and debris and sealed.
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering
at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-28
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 20 – SAND FILTER VAULT
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed
Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance.
Manhole access covered.
Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance
person.
Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access.
Large access doors/plate
Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can opened as designed.
Gaps, doesn't cover completely Large access doors not flat and/or access
opening not completely covered.
Doors close flat; covers access
opening completely.
Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door
or plate.
Lifting rings sufficient to lift or
remove door or plate.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-29
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 21 – STORMFILTER (CARTRIDGE TYPE)
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed
Facility Documentation Update facility inspection record after each inspection. Maintenance records are up to date.
Provide certification of replaced filter media. Filter media is certified to meet Stormfilter® specifications.
Site Trash and debris Any trash or debris which impairs the function of the facility. Trash and debris removed from facility.
Contaminants and pollution Any evidence of contaminants or pollution such as oils, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations.
Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Life cycle System has not been inspected for three years. Facility is re-inspected and any needed maintenance performed.
Vault Treatment Area Sediment on vault floor Greater than 2 inches of sediment. Vault is free of sediment.
Sediment on top of cartridges Greater than ½ inch of sediment. Vault is free of sediment.
Multiple scum lines above top of cartridges
Thick or multiple scum lines above top of cartridges. Probably due to plugged canisters or underdrain manifold.
Cause of plugging corrected, canisters replaced if necessary.
Vault Structure Damage to wall, Frame, Bottom, and/or Top Slab
Cracks wider than ½-inch and any evidence of soil particles entering the structure through the cracks, or qualified inspection personnel determines the vault is not structurally sound.
Vault replaced or repaired to design specifications.
Baffles damaged Baffles corroding, cracking warping, and/or showing signs of failure as determined by maintenance/inspection person.
Repair or replace baffles to specification.
Filter Media Standing water in vault 9 inches or greater of static water in the vault for more than 24 hours following a rain event and/or overflow occurs frequently. Probably due to
plugged filter media, underdrain or outlet pipe.
No standing water in vault 24 hours after a rain event.
Short circuiting Flows do not properly enter filter cartridges. Flows go through filter media.
Underdrains and Clean-Outs Sediment/debris Underdrains or clean-outs partially plugged or filled with sediment and/or debris. Underdrains and clean-outs free of sediment and debris.
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance.
Manhole access covered.
Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-30
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 21 – STORMFILTER (CARTRIDGE TYPE)
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed
Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access.
Large access doors/plate Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can opened as designed.
Gaps, doesn't cover
completely
Large access doors not flat and/or access
opening not completely covered.
Doors close flat and cover access
opening completely.
Lifting Rings missing,
rusted
Lifting rings not capable of lifting weight of door
or plate.
Lifting rings sufficient to lift or
remove door or plate.
Inspection Frequency Maintenance conditions are site-specific,
depending on pollutant loading.
FIRST YEAR POST CONSTRUCTION: Monthly during wet season, every other month during dry season
FOLLOWING FIRST YEAR: Continue monthly until site-specific frequency is established, then follow that schedule
AT A MINIMUM, FOLLOWING FIRST YEAR: Annually (or quarterly if used as primary treatment) and following significant storms.
Inspect Stormfilter facility for any
maintenance deficiencies; maintain or replace as required per established site-specific schedule and manufacturer’s requirements.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-31
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 22 – BAFFLE OIL/WATER SEPARATOR
Maintenance Component Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed
Site Trash and debris Any trash or debris which impairs the function of the facility. Trash and debris removed from facility.
Contaminants and pollution Floating oil in excess of 1 inch in first chamber, any oil in other chambers or other contaminants of any type in any chamber.
No contaminants present other than a surface oil film.
Vault Treatment
Area
Sediment
accumulation
Sediment accumulates exceeds 6 inches in the
vault.
No sediment in the vault.
Discharge water not
clear
Inspection of discharge water shows obvious
signs of poor water quality- effluent discharge from vault shows thick visible sheen.
Effluent discharge is clear.
Trash or debris accumulation Any trash and debris accumulation in vault (floatables and non-floatables). Vault is clear of trash and debris.
Oil accumulation Oil accumulations that exceed 1 inch, at the surface of the water in the oil/water separator chamber.
No visible oil depth on water.
Vault Structure Damage to Wall, Frame, Bottom, and/or Top Slab
Cracks wider than ½-inch or evidence of soil particles entering the structure through the cracks, or maintenance/inspection personnel determines that the vault is not structurally sound.
Vault replaced or repaired to design specifications.
Baffles damaged Baffles corroding, cracking, warping and/or
showing signs of failure as determined by maintenance inspection personnel.
Repair or replace baffles to
specifications.
Gravity Drain Inoperable valve Valve will not open and close. Valve opens and closes normally.
Valve won’t seal Valve does not seal completely. Valve completely seals closed.
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place.
Any open manhole requires immediate maintenance.
Manhole access covered.
Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts
cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person.
Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access.
Large access doors/plate Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can opened as designed.
Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat and cover access opening completely.
Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or cover/lid. Lifting rings sufficient to lift or remove cover/lid.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-32
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 23 – COALESCING PLATE OIL/WATER SEPARATOR
Maintenance Component Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed
Site Trash and debris Any trash or debris which impairs the function of the facility. Trash and debris removed from facility.
Contaminants and pollution Floating oil in excess of 1 inch in first chamber, any oil in other chambers or other contaminants of any type in any chamber.
No contaminants present other than a surface oil film.
Vault Treatment
Area
Sediment
accumulation in the forebay
Sediment accumulation of 6 inches or greater in
the forebay.
No sediment in the forebay.
Discharge water not clear Inspection of discharge water shows obvious signs of poor water quality - effluent discharge from vault shows thick visible sheen.
Repair function of plates so effluent is clear.
Trash or debris accumulation Trash and debris accumulation in vault (floatables and non-floatables). Trash and debris removed from vault.
Oil accumulation Oil accumulation that exceeds 1 inch at the water surface in the in the coalescing plate chamber. No visible oil depth on water and coalescing plates clear of oil.
Coalescing Plates Damaged Plate media broken, deformed, cracked and/or showing signs of failure. Replace that portion of media pack or entire plate pack depending on severity of failure.
Sediment accumulation Any sediment accumulation which interferes with the operation of the coalescing plates. No sediment accumulation interfering with the coalescing plates.
Vault Structure Damage to Wall, Frame, Bottom,
and/or Top Slab
Cracks wider than ½-inch and any evidence of soil particles entering the structure through the
cracks, or maintenance inspection personnel determines that the vault is not structurally sound.
Vault replaced or repaired to design specifications.
Baffles damaged Baffles corroding, cracking, warping and/or showing signs of failure as determined by maintenance/inspection person.
Repair or replace baffles to specifications.
Ventilation Pipes Plugged Any obstruction to the ventilation pipes. Ventilation pipes are clear.
Shutoff Valve Damaged or inoperable Shutoff valve cannot be opened or closed. Shutoff valve operates normally.
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes.
Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate
maintenance.
Manhole access covered.
Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance
person.
Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards.
Allows maintenance person safe access.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-33
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 23 – COALESCING PLATE OIL/WATER SEPARATOR
Maintenance Component Defect Condition When Maintenance is Needed Results Expected When Maintenance is Performed
Large access doors/plate Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can opened as designed.
Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat and cover access opening completely.
Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate.
NO. 24 – CATCH BASIN INSERT
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Media Insert Visible Oil Visible oil sheen passing through media Media inset replaced.
Insert does not fit catch basin properly Flow gets into catch basin without going through media. All flow goes through media.
Filter media plugged Filter media plugged. Flow through filter media is normal.
Oil absorbent media
saturated
Media oil saturated. Oil absorbent media replaced.
Water saturated Catch basin insert is saturated with water, which
no longer has the capacity to absorb.
Insert replaced.
Service life exceeded Regular interval replacement due to typical average life of media insert product, typically one month.
Media replaced at manufacturer’s recommended interval.
Seasonal maintenance When storms occur and during the wet season. Remove, clean and replace or install new insert after major storms, monthly during the wet season or at manufacturer’s recommended interval.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-34
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 25 – DRYWELL BMP
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Preventative Plugging, obstructions Any cause limiting flow into drywell. Drywell able to receive full flow prior to and during wet season.
Site Trash and debris Trash or debris that could end up in the drywell is evident. No trash or debris that could get into the drywell can be found.
Pipes Inlet is plugged The entrance to the pipe is restricted due to sediment, trash, or debris. The entrance to the pipe is not restricted.
Vegetation/roots Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes.
Plugged Sediment or other material prevents free flow of water through the pipe. Water flows freely through pipes.
Broken or joint leaks. Damage to the pipe or pipe joints allowing water to seep out. Pipe does not allow water to exit other than at the outlet.
Structure Basin leaks Holes or breaks in the basin allow water to leave the basin at locations other than per design. Basin is sealed and allows water to exit only where designed.
Filter Media Filter media plugged Filter media plugged. Flow through filter media is normal.
Inspection Frequency Annually and prior to and following significant storms. Inspect drywell system for any defects of deficiencies.
NO. 26 – GRAVEL FILLED INFILTRATION TRENCH BMP
Maintenance
Component
Defect or Problem Conditions When Maintenance is Needed Results Expected When
Maintenance is Performed
Preventative Blocking, obstructions Debris or trash limiting flow to infiltration trench. Infiltration trench able to receive full flow prior to and during wet season.
Site Trash and debris Trash or debris that could end up in the
infiltration trench is evident.
No trash or debris that could get into
the infiltration trench can be found.
Pipes Inlet is plugged The entrance to the pipe is restricted due to
sediment, trash, or debris.
The entrance to the pipe is not
restricted.
Vegetation/roots Vegetation/roots that reduce free movement of
water through pipes.
Water flows freely through pipes.
Plugged Sediment or other material prevents free flow of
water through the pipe.
Water flows freely through pipes.
Broken or joint leaks. Damage to the pipe or pipe joints allowing water to seep out. Pipe does not allow water to exit other than at the outlet to the trench.
Structure Flow not reaching trench Flows are not getting into the trench as designed. Water enters and exits trench as designed.
Cleanout/inspection access does not allow
cleaning or inspection of trench
The cleanout/inspection access is not available. Cleanout/inspection access is available.
Filter Media Filter media plugged Filter media plugged. Flow through filter media is normal.
Inspection Frequency Annually and prior to and following significant
storms.
Inspect infiltration trench system for
any defects of deficiencies.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-35
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 27 – GRAVEL FILLED DISPERSION TRENCH BMP
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Preventative Blocking, obstructions Debris or trash limiting flow to dispersion trench or preventing spreader function. Dispersion trench able to receive full flow prior to and during wet season.
Site Trash and debris Trash or debris that could end up in the dispersion trench is evident. No trash or debris that could get into the dispersion trench can be found.
Pipes Inlet is plugged The entrance to the pipe is restricted due to sediment, trash, or debris. The entrance to the pipe is not restricted.
Vegetation/roots Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes.
Plugged Sediment or other material prevents free flow of water through the pipe. Water flows freely through pipes.
Broken joint or joint leaks. Damage to the pipe or pipe joints allowing water to seep out. Pipe does not allow water to exit other than at the outlet to the trench.
Cleanout caps Cleanout caps are broken, missing, or buried. Cleanout caps are accessible and intact.
Structure Flow not reaching trench Flows are not getting into the trench as designed. Water enters and exits trench as designed.
Perforated pipe plugged Flow not able to enter or properly exit from perforated pipe. Water freely enters and exits perforated pipe.
Flow not spreading evenly at outlet of trench
Outlet flows channelizing or not spreading evenly from trench. Sheet flow occurs at the outlet of the trench.
Cleanout/inspection access does not allow
cleaning or inspection of perforated pipe
The cleanout/inspection access is not available. Cleanout/inspection access is available.
Filter Media Filter media plugged Filter media plugged. Flow through filter media is normal.
Inspection Frequency Annually and prior to and following significant storms. Inspect dispersion trench system for any defects of deficiencies.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-36
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 28 – NATIVE VEGETATED SURFACE / NATIVE VEGETATED LANDSCAPE BMP
Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance Is Performed
Site Trash and debris Trash and debris accumulated on the native vegetated surface/native vegetated landscape site.
Native vegetated surface site free of any trash or debris.
Vegetation Native vegetation type Less than two species each of native trees, shrubs, and groundcover occur in the design area.
A minimum of two species each of native trees, shrubs, and groundcover is established and healthy.
Native vegetated area Less than 90% if the required vegetated area has healthy growth. A minimum of 90% of the required vegetated area has healthy growth.
Undesirable vegetation Weeds, blackberry, and other undesirable plants are invading more than 10% of vegetated area. Less than 10% undesirable vegetation occurs in the required native vegetated surface area.
Vegetated Area Soil compaction Soil in the native vegetation area compacted. Less than 8% of native vegetation area is compacted.
Insufficient area Less than 3.5 square feet of native vegetation area for every 1 square foot of impervious surface.
A minimum of 3.5 square feet of native vegetation area for every 1 square foot of impervious surface.
Excess slope Slope of native vegetation area greater than 15%. Slope of native growth area does not exceed 15%.
Inspection Frequency Annually Inspect native vegetation area for any defects of deficiencies
NO. 29 – PERFORATED PIPE CONNECTIONS BMP
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Preventative Blocking, obstructions Debris or trash limiting flow into perforated pipe system or outfall of BMP is plugged or otherwise nonfunctioning.
Outfall of BMP is receiving designed flows from perforated pipe connection.
Inflow Inflow impeded Inflow into the perforated pipe is partially or fully blocked or altered to prevent flow from getting
into the pipe.
Inflow to the perforated pipe is unimpeded.
Pipe Trench Area Surface compacted Ground surface over the perforated pipe trench is
compacted or covered with impermeable material.
Ground surface over the perforated
pipe is not compacted and free of any impervious cover.
Outflow Outflow impeded Outflow from the perforated pipe into the public drainage system is blocked. Outflow to the public drainage system is unimpeded.
Outfall Area Erosion or landslides Existence of the perforated pipe is causing or exasperating erosion or landslides. Perforated pipe system is sealed off and an alternative BMP is implemented.
Inspection Frequency Annually and prior to and following significant storms. Perforated pipe system is operating as designed.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-37
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 30 – PERMEABLE PAVEMENT BMP
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Preventative Surface cleaning/ vegetation control Media surface vacuumed or pressure washed annually, vegetation controlled to design maximum. Weed growth suggesting sediment accumulation.
No dirt, sediment, or debris clogging porous media, or vegetation limiting infiltration.
Porous Concrete, Porous Asphaltic Concrete, and Permeable Pavers
Trash and debris Trash and debris on the pavement interfering with infiltration; leaf drop in fall season. No trash or debris interfering with infiltration.
Sediment accumulation Sediment accumulation on the pavement interfering with infiltration; runoff from adjacent areas depositing sediment/debris on pavement.
Pavement infiltrates as designed; adjacent areas stabilized.
Infiltration rate Pavement does not infiltrate at a rate of 10 inches per hour. Pavement infiltrates at a rate greater than 10 inches per hour.
Ponding Standing water for a long period of time on the surface of the pavement. Standing water infiltrates at the desired rate.
Broken or cracked pavement Pavement is broken or cracked. No broken pavement or cracks on the surface of the pavement.
Settlement Uneven pavement surface indicating settlement of the subsurface layer. Pavement surface is uniformly level.
Moss growth Moss growing on pavement interfering with infiltration. No moss interferes with infiltration.
Inflow Inflow to the pavement is diverted, restricted, or depositing sediment and debris on the pavement.
Inflow to pavement is unobstructed and not bringing sediment or debris to the pavement.
Underdrain Underdrain is not flowing when pavement has been infiltrating water. Underdrain flows freely when water is present.
Overflow Overflow not controlling excess water to desired location; native soil is exposed or other signs of erosion damage are present.
Overflow permits excess water to leave the site at the desired location; Overflow is stabilized and
appropriately armored.
Permeable Pavers Broken or missing pavers Broken or missing paving blocks on surface of pavement. No missing or broken paving blocks interfering with infiltration.
Level surface Uneven surface due to settlement or scour of fill in the interstices of the paving blocks. Pavement surface is uniformly level.
Compaction Poor infiltration due to soil compaction between paving blocks. No soil compaction in the interstices of the paver blocks limiting
infiltration.
Dead grass Grass in the interstices of the paving blocks is
dead.
Healthy grass is growing in the
interstices of the paver blocks.
Inspection Frequency Annually and after large storms, and as needed seasonally to control leaf drop, evergreen needles etc.
Permeable pavement is functioning
normally.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-38
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 31 – BIORETENTION BMP
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Preventative Vegetation Vegetation to be watered and pruned as
needed and mulch applied to a minimum of 2 inches to maintain healthy growth.
Healthy vegetation growth with full
coverage as designed.
Bioretention Area Trash and debris Trash and debris in the bioretention area; leaf drop in the fall season. No trash or debris In the bioretention area.
Sediment accumulation Sediment accumulation in the bioretention area interfering with infiltration. Water in the bioretention infiltrates as designed.
Ponding Standing water in the bioretention area for more than two days. Standing water infiltrates at the desired rate.
Inflow Inflow not getting into bioretention;
debris/sediment blockage at inlet features; native soil is exposed or other signs of erosion damage is present.
Unobstructed and properly routed
inflow into bioretention area; inlet is stabilized and appropriately armored.
Overflow outlet Overflow water not controlled by outlet features; native soil is exposed or other signs of erosion damage is present.
Outlet features control overflow; overflow is stabilized and appropriately armored.
Underdrain Underdrain is not flowing when bioretention area has been infiltrating water. Underdrain flows freely when water is present.
Vegetation Plant health Plants not thriving across at least 80% of the entire design vegetated area within the BMP; overly dense vegetation requiring pruning.
Healthy water tolerant plants in bioretention area, plants thriving across at least 80% of the entire design vegetated area within the facility.
Plant species Plants not water tolerant species. Plants are water tolerant.
Weeds Weeds growing in bioretention area. No weeds in bioretention area.
Watering Planting schedule requires frequent watering (approx. weekly Year 1, bimonthly Years 2 and
3) for new facilities, and as needed for established plantings or dry periods
Plants are established and thriving
Pest Control Signs of pests, such as wilting or chewed leaves or bark, spotting or other indicators; extended ponding period encouraging mosquitoes
Plant community is pest-free when following an approved Integrated Pest Management plan; bioretention functioning normally and ponding
controlled as needed for pest control
Containment Berm and Earthen Slopes Erosion; Erosion occurring at earthen slopes or containment berm side slope. Erosion on the containment berm and side slopes has been repaired and the cause of the erosion corrected.
Voids created by nuisance animals (e.g., rodents) or tree roots
Voids affecting berm integrity or creating leaky pond condition Voids have been repaired; facility is free of nuisance animals following an approved Integrated Pest Management plan.
Settlement Any part of the containment berm top has less than 6 inches of freeboard from the maximum pond level to the top of the berm.
A minimum of 6 inches freeboard from the maximum pond level to the top of the berm.
Amended Soil Soil nutrients Soil not providing plant nutrients. Soil providing plant nutrients.
Bare spots Bare spots on soil in bioretention area. No bare spots, bioretention area covered with vegetation or mulch mixed into the underlying soil.
Compaction Poor infiltration due to soil compaction in the bioretention area. No soil compaction in the bioretention area.
Inspection Frequency Annually and after large storms, and as needed seasonally for pruning, plant maintenance, pest control and to control leaf drop, evergreen needles etc.
Bioretention facility is functioning normally; plant community is thriving and pest-free.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-39
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 32 – RAINWATER HARVESTING BMP
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Preventative Storage volume No rain water in storage unit at the beginning of the rain season. Maximum storage available at the beginning of the rain season (Oct. 1st).
Collection Area Trash and debris Trash of debris on collection area may plug filter system Collection area clear of trash and debris.
Filter Restricted or plugged Filter is partially or fully plugged preventing water
from getting in to the storage unit.
Filter is allowing collection water
into storage unit.
Inspection Frequency Annually and after large storms Rain harvesting equipment is
functioning normally.
Maintenance log A Maintenance log must be kept and available for
review by KC staff.
Maintenance log is kept and is
available to KC staff.
NO. 33 – ROCK PAD BMP
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Site Trash and debris Trash and debris accumulated on rock pad site. Rock pad site free of any trash or debris.
Rock Pad Area Rock pad size Rock pad is not 2 feet by 3 feet by 6 inches thick or as designed. Rock pad is 2 feet by 3 feet by 6 inches thick or as designed.
Vegetation Vegetation is seen growing in or through rock pad. No vegetation within rock pad area.
Rock Exposed soil Soil can be seen through the rock pad. Full thickness of the rock pad is in place, no soil visible through rock pad.
Inspection Frequency Annually and after large storms Rock pad is functioning normally.
NO. 34 – SHEET FLOW BMP
Maintenance
Component
Defect or Problem Conditions When Maintenance is Needed Results Expected When
Maintenance is Performed
Site Trash and debris Trash and debris accumulated on the sheet flow site. Sheet flow site free of any trash or debris.
Sheet flow area Erosion Soil erosion occurring in sheet flow zone. Soil erosion is not occurring and rills and channels have been repaired.
Concentrated flow Sheet flow is not occurring in the sheet flow zone. Sheet flow area is regraded to provide sheet flow.
Inspection Frequency Annually and after large storms Rain harvesting equipment is functioning normally.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-40
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 35 – SPLASH BLOCK BMP
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Site Trash and debris Trash and debris accumulated on the splash block. Splash block site free of any trash or debris.
Splash Block Dislodged Splash block moved from outlet of downspout. Splash block correctly positioned to catch discharge from downspout.
Channeling Water coming off the splash block causing erosion. No erosion occurs from the splash block.
Downspout water misdirected Water coming from the downspout is not discharging to the dispersal area. Water is discharging normally to the dispersal area.
Inspection Frequency Annually and after large storms. Rain harvesting equipment is functioning normally.
2016 Surface Water Design Manual – Appendix A 4/24/2016 A-41
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 36 – VEGETATED ROOF BMP (Retained from the 2009 SWDM for reference)
Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed
Preventative Vegetation Vegetation to be watered and pruned as needed to maintain healthy growth. Healthy vegetation growth with full coverage as designed.
Site Trash and debris Trash and debris has accumulated on the vegetated roof. Vegetated roof free of any trash or debris.
Waterproof Membrane Leaking Waterproof membrane breached. Waterproof membrane has no tears or holes allowing water through it.
Drainage Layer Drainage pathway Drainage layer flow plugged or obstructed. Drainage layer passing water with no obstruction.
Drainage Overflow Drainage of overflow is obstructed. Overflow has no obstruction.
Growth Media Compaction Soil in the growth media area compacted. No part of the growth media is compacted.
Erosion Growth media washed out. Growth media is not being washed away.
Nutrients Plants are not thriving. Growth media has proper nutrients to support plant growth.
Vegetation Vegetation Type Vegetation species not succulents, grass, herbs,
and/or wildflowers adapted to harsh conditions. Correct species of vegetation is used.
Vegetation Area Healthy vegetation covers less than 90% of vegetation area. Healthy vegetation covers more than 90% of vegetation area.
Undesirable Vegetation Weeds and other undesirable plants are invading more than 10% of vegetated area. No undesirable vegetation occurs in the vegetated area. No herbicides or pesticides used to control undesirable vegetation.
Special Vegetation Special vegetation not thriving. Special vegetation is kept healthy and inspected on frequent
schedule.
Border Zone Access Border zone limited by vegetation overgrowth or other means. Border zone is kept open so vegetated area is accessible.
Gravel Stop Containment Gravel stop does not contain overflow or divert it to a designed outlet. Overflow water is only exits from the designed outlet.
Inspection Frequency Annually and after large storms. Rain harvesting equipment is functioning normally.
Vegetation inspected monthly. Vegetation is kept healthy and thriving.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-42
Solera Phase 2: Block C and Block D – New Home Co.
Appendix K
Appendix K
Geotechnical Report
(PROVIDED SEPARATELY)
Solera Phase 2: Block C and Block D – New Home Co.
Appendix J
Appendix L
2018 Infiltration Test Report
(PROVIDED SEPARATELY)
Solera Phase 2: Block C and Block D – New Home Co.
Appendix M
Appendix M
Infiltration Test Report Memorandum
15365 NE 90th Street, Suite 100 • Redmond, WA 98052 • (425) 449-4704
3130 Varney Lane, Suite 105 • Pasco, WA 99301 • (509) 905-0275
esnw.com
Earth Solutions NW LLC
Geotechnical Engineering, Construction
Observation/Testing and Environmental Services
January 14, 2025
ES-5719.08
TNHC Washington, LLC
1700 Northwest Gilman Boulevard, Suite 220
Issaquah, Washington 98027
Attention: Jaden Storedahl
Subject: Infiltration Evaluation
Solera – Blocks C and D
Northeast 11th Street and Jefferson Avenue Northeast
Renton, Washington
Dear Jaden:
As requested, Earth Solutions NW, LLC (ESNW) has prepared this infiltration evaluation letter
regarding the proposed project. This letter was prepared in general accordance with the scope
of services outlined in our proposal dated November 4, 2024. A summary of the subsurface
exploration, laboratory analyses, and recommendations with respect to infiltration feasibility and
design are provided herein.
Project & Site Description
Currently referred to as Blocks C and D, the project site is associated with the larger “Solera”
mixed-use development and is located to the west of Northeast Sunset Boulevard, between
Northeast 10th Street and Kirkland Avenue Northeast, in Renton, Washington. The approximate
location of the property is illustrated on Plate 1 (Vicinity Map). The site consists of three tax
parcels (King County Parcel Numbers 722780-1785, -1235, and -1405), totaling about 4.12 acres.
We understand that a townhome development and associated improvements will be constructed
on site. Per the referenced site plan, infiltration is currently proposed in the form of various
bioretention planters spread throughout the development area.
TNHC Washington, LLC ES-5719.08
January 14, 2025 Page 2
Earth Solutions NW, LLC
Subsurface Conditions
An ESNW representative observed, logged, and sampled four test pits on November 18 and 19,
2024. The test pits were targeted to readily accessible site areas whereat bioretention is currently
proposed and were performed using a mini trackhoe and operator retained by ESNW. At the time
of the November 2024 fieldwork, both the Block C and Block D areas had been previously graded.
Block C had been covered with hydroseed while Block D was primarily in use as a parking and
storage area for the Solera project construction activities. The test pits were completed to
evaluate and classify site soils and to characterize groundwater conditions within the
development area. The approximate locations of the test pits are depicted on Plate 2 (Subsurface
Exploration Plan). Please refer to the test pit logs provided as an attachment to this letter for a
more detailed description of subsurface conditions.
Representative soil samples collected at the test pit locations were analyzed for moisture content
and grain size distribution in general accordance with both Unified Soil Classification System
(USCS) and United States Department of Agriculture (USDA) methods and procedures. The
laboratory test results are provided as an attachment to this evaluation letter.
Topsoil and Fill
Topsoil was generally encountered across the Block C lot; topsoil present in the area is
considered to be the result of prior stripping, stockpiling, and replacement of the original topsoil
layer. The topsoil was encountered within the upper 12 inches of existing grades at the test pit
locations and was characterized by a dark brown color, minor root intrusions, and trace organic
matter. For the intent of this evaluation and narrative, the replaced topsoil is not referred to as “
structural fill” given that it was likely intended solely for use as pad cover. However, it should be
noted that the topsoil is designated as fill in the corresponding exploration logs. Topsoil was not
encountered at the test pit (TP-301) performed in Block D.
Structural fill soil was encountered in one test pit (TP-301) during the subsurface exploration. The
fill consisted of roughly three inches of crushed rock over poorly graded sand. The fill was
observed to a depth of approximately two-and-one-half feet below the existing ground surface
(bgs) and characterized as medium dense and damp.
Native Soil
Native soils consisting primarily of poorly to well-graded sand with silt and silty sand (USCS: SP-
SM, SW-SM, and SM, respectively) were observed underlying topsoil and structural fill. The in-
situ density of the native soil was characterized primarily as medium dense to dense at each test
location, and the in-situ moisture content was chiefly characterized as damp to moist at the time
of exploration. The maximum exploration depth was approximately nine feet bgs.
TNHC Washington, LLC ES-5719.08
January 14, 2025 Page 3
Earth Solutions NW, LLC
Geologic Setting
The referenced geologic map identifies Vashon glacial till (Qt) deposits underlying the site and
surrounding area with younger sands (Qys) to the west of the site. Vashon till is characterized as
a concrete-like mixture of silt, sand, gravel, and clay. Younger sands are generally well sorted,
poorly graded, and loose sands of varying fines content. The referenced WSS resource identifies
Urban land and arents Alderwood material. Designation of arents indicates some reworking
(earthwork and grading activities) of the native soils. Based on our field observations, the on-site
native soil is consistent with the characteristics of the younger sands unit that are mapped in the
project vicinity.
Groundwater
Neither perched groundwater nor a shallow, local groundwater table were observed during the
November 2024 subsurface exploration. Furthermore, no evidence of iron oxide staining and/or
mottling (which are potentially indicative of seasonally high groundwater fluctuations) were
observed. However, zones of perched groundwater may be encountered within site excavations
depending on location and the time of year. Groundwater seepage is common within glacial
deposits; seepage rates and elevations fluctuate depending on many factors, including
precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater
seepage flow rates are higher during the winter, spring and early summer months.
Infiltration Evaluation
Four small-scale Pilot Infiltration Tests (PITs) were conducted in general accordance with the
requirements of the 2022 City of Renton Surface Water Design Manual (2022 RSWDM) during
the November 2024 fieldwork. The PITs were completed within undisturbed native soils at depths
ranging between roughly three-and-one-half to six-and-one-half feet bgs. The following table
provides the test location, test depth, encountered soil type, measured rate, appropriate
correction factors, and the long-term recommended design infiltration rate (Idesign):
Test
Location
Approx.
Test Depth
(feet)
Soil
Type
Imeasured
(in/hr)
Correction Factors Idesign
(in/hr) Ftesting Fgeometry Fplugging
TP-301 3.5 SW-SM 30 0.5 0.5 0.9 6
TP-302 6.5 SM 1.25 0.5 0.5 0.9 0.3
TP-303 3.5 SP-SM 14.4 0.5 0.5 0.9 3.5
TP-304 4 SW-SM 21 0.5 0.5 0.9 4
TNHC Washington, LLC ES-5719.08
January 14, 2025 Page 4
Earth Solutions NW, LLC
Based on our in-situ test results, soils present within Blocks C and D are considered to possess
somewhat variable infiltration characteristics. With respect to the majority of the site area (as
demonstrated via the PITs completed at test pit locations TP-301, -303, and -304) the native,
poorly to well-graded sand with silt possesses a moderate infiltration potential. In our opinion, the
lowest measured rate recorded from these PITs (TP-303) and resulting design infiltration rate
of 3.5 in/hr should be used for facility design across the majority of the site where cleaner
sands are anticipated. The exception to this is the southwestern site corner in the vicinity of TP-
302 whereat silty sand soils were primarily exposed. Based on our representative testing
completed at TP-302, a design infiltration rate of 0.3 in/hr should be used for facility design
in this area or areas where silty sand is encountered.
Subsequent overexcavation following the completion of the PITs indicate relatively uniform, sand-
predominate soils at TP-301, -303, and -304 to depths of about seven to at least nine feet bgs.
Thereafter, the test pits were terminated or silty sand soils were encountered. The exception to
this is TP-302 whereat silty sand was encountered throughout.
Provided that facilities are designed in accordance with the infiltration rates developed based on
site location and anticipated soil conditions, and an overflow is included, it is our opinion that
infiltration can be successfully utilized for the project area. If designs alter or change from the
conditions under which this letter was prepared, ESNW should contacted to review the
evaluations provided herein and determine if any additional testing may be warranted. In any
case, ESNW should be contacted to review infiltration designs to confirm that they have
incorporated the recommendations provided in this letter. Additionally, ESNW should be
contacted during infiltration facility construction to confirm soil conditions are as anticipated. It
should be noted that sandy deposits such as those encountered on site may possess discrete,
localized, and/or erratic lensing which may alter or reduce infiltration performance if present within
relative proximity to the infiltration facility bottom. As such, confirmatory test pits that extend to a
depth below the facility subgrade elevation that is equivalent to the minimum required vertical
separation offset may be recommended at representative facility locations during construction.
The intent of the confirmatory test pits would be to evaluate the presence of such lensing and if
overexcavation and restoration may be necessary.
Limitations
This letter has been prepared for the exclusive use of TNHC Washington, LLC and its
representatives. No warranty, express or implied, is made. The recommendations and
conclusions provided in this letter are professional opinions consistent with the level of care and
skill that is typical of other members in the profession currently practicing under similar conditions
in this area. Variations in the soil and groundwater conditions encountered at the test pit locations
may exist and may not become evident until construction. ESNW should reevaluate the contents
of this letter if variations are encountered.
TNHC Washington, LLC ES-5719.08
January 14, 2025 Page 5
Earth Solutions NW, LLC
We trust this letter meets your current needs. Please call if you have any questions about this
letter or if we can be of further assistance.
Sincerely,
EARTH SOLUTIONS NW, LLC
Steven K. Hartwig, L.G. Chase G. Halsen, L.G., L.E.G.
Senior Staff Geologist Project Manager
Raymond A. Coglas, P.E.
Senior Principal Engineer
Attachments: Plate 1 – Vicinity Map
Plate 2 – Subsurface Exploration Plan
Subsurface Exploration Logs
Laboratory Test Results
01/14/2025
01/14/2025
TNHC Washington, LLC ES-5719.08
January 14, 2025 Page 6
Earth Solutions NW, LLC
References:
2022 City of Renton Surface Water Design Manual (2022 RSWDM)
Online Web Soil Survey (WSS) resource and the Soil Survey of Washington, provided by
the Natural Resources Conservation Service (NRCS) under the United States Department
of Agriculture (USDA)
Preliminary Geologic Map of Seattle and Vicinity, Washington, compiled by H.H. Waldron
et. al., dated 1961
Townhouse Layout Exhibit, prepared by KPFF, dated June 28, 2024
Drawn CAM
Checked SKH Date Jan.2025
Date 01/07/2025 Proj.No.5719.08
Plate 1
Geotechnical Engineering,Construction
Observation/Testing and Environmental Services
Earth Solutions NWLLCEarthSolutionsNWLLC
EarthSolutionsNWLLC
Vicinity Map
Solera –Blocks C &D
Renton,Washington
Reference:
King County,Washington
OpenStreetMap.org
NORTH
NOTE:This plate may contain areas of color.ESNW cannot be
responsible for any subsequent misinterpretation of the information
resulting from black &white reproductions of this plate.
Renton
SITE
Plate
Proj.No.
Date
Checked
Drawn
Earth
Solutions
NWLLC
Geotechnical
Engineering,Construction
Observation/Testing
and
Environmental
Services
Earth
Solutions
NWLLC
Earth
Solutions
NWLLC
TP-302
TP-303
TP-304
TP-301
Block C
Block B
Block A
Block D
n.e.10th street
n.e.11th
street
jefferso n aven ue n.e.
harringto n place n.e.
n.e.12th street
1
23
4567
89
11 10
12131415
16171819
20
212223 2425262728
29
30313233
3435363738
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
1
234
56789
10
11
12
13
14
15 16 17
18
19
20
21
22
23
24
25
26
27
28
29
alley
a
alley B
alley C
alley
D
alley
E
alley
F
alley
G Subsurface
Exploration
Plan
Solera
–
Blocks
C
&
D
Renton,
Washington
0 50 100 20 0
Scale in Feet1"=100'
NOTE:This plate may contain areas of color.ESNW cannot be
responsible for any subsequent misinterpretation of the information
resulting from black &white reproductions of this plate.
NOTE:The graphics shown on this plate are not intended for design
purposes or precise scale measurements,but only to illustrate the
approximate test locations relative to the approximate locations of
existing and /or proposed site features.The information illustrated
is largely based on data provided by the client at the time of our
study.ESNW cannot be responsible for subsequent design changes
or interpretation of the data by others.
LEGEND
Approximate Location of
ESNW Test Pit,Proj.No.
ES-5719.08,Nov.2024
Subject Site
Proposed Townhouse
TP-301
NORTH
CAM
SKH
01/07/2025
5719.08
2
>
12%
Fines
<
5%
Fines
Highly
Organic
Soils
Silts
and
Clays
Liquid
Limit
50
or
More
Silts
and
Clays
Liquid
Limit
Less
Than
50
Fine-Grained
Soils
-
50%
or
More
Passes
No.
200
Sieve
Coarse-Grained
Soils
-
More
Than
50%
Retained
on
No.
200
Sieve
Sands
-
50%
or
More
of
Coarse
Fraction
Passes
No.
4
Sieve
Gravels
-
More
Than
50%
of
Coarse
Fraction
Retained
on
No.
4
Sieve
>
12%
Fines
<
5%
Fines GW
GP
GM
GC
SW
SP
SM
SC
ML
CL
OL
MH
CH
OH
PT
Well-graded gravel with
or without sand,little to
no fines
Poorly graded gravel with
or without sand,little to
no fines
Silty gravel with or without
sand
Clayey gravel with or
without sand
Well-graded sand with
or without gravel,little to
no fines
Poorly graded sand with
or without gravel,little to
no fines
Silty sand with or without
gravel
Clayey sand with or
without gravel
Silt with or without sand
or gravel;sandy or
gravelly silt
Clay of low to medium
plasticity;lean clay with
or without sand or gravel;
sandy or gravelly lean clay
Organic clay or silt of
low plasticity
Elastic silt with or withoutsandorgravel;sandy or
gravelly elastic silt
Clay of high plasticity;
fat clay with or without
sand or gravel;sandy or
gravelly fat clay
Organic clay or silt of
medium to high plasticity
Peat,muck,and other
highly organic soils
EEaarrtthh SSoolluuttiioonnss NNWWLLC
Geotechnical Engineering,ConstructionObservation/Testing and Environmental Services EXPLORATION LOG KEY
Fill FILL Made Ground
Classifications of soils in this geotechnical report and as shown on the exploration logs are based on visualfieldand/or laboratory observations,which include density/consistency,moisture condition,grain size,andplasticityestimates,and should not be construed to imply field or laboratory testing unless presented herein.
Visual-manual and/or laboratory classification methods of ASTM D2487 and D2488 were used as an
identification guide for the Unified Soil Classification System.
Terms Describing Relative Density and Consistency
Coarse-Grained Soils:
Fine-Grained Soils:
SPT blows/foot
SPT blows/foot
Test Symbols &Units
Fines =Fines Content (%)
MC =Moisture Content (%)
DD =Dry Density (pcf)
Str =Shear Strength (tsf)
PID =Photoionization Detector (ppm)
OC =Organic Content (%)
CEC =Cation Exchange Capacity (meq/100 g)
LL =Liquid Limit (%)
PL =Plastic Limit (%)
PI =Plasticity Index (%)
Component Definitions
Descriptive Term Size Range and Sieve Number
Smaller than No.200 (0.075 mm)
Boulders
Modifier Definitions
Percentage by
Weight (Approx.)
<5
5 to 14
15 to 29
>30_
Modifier
Trace (sand,silt,clay,gravel)
Slightly (sandy,silty,clayey,gravelly)
Sandy,silty,clayey,gravelly
Very (sandy,silty,clayey,gravelly)
Moisture Content
Dry -Absence of moisture,dusty,dry to
the touch
Damp -Perceptible moisture,likely below
optimum MC
Moist -Damp but no visible water,likely
at/near optimum MC
Wet -Water visible but not free draining,
likely above optimum MC
Saturated/Water Bearing -Visible free
water,typically below groundwater table
Symbols
Cement groutsurfaceseal
Bentonite
chips
Grout
seal
Filter pack with
blank casing
section
Screened casing
or Hydrotip with
filter pack
End cap
ATD =At time
of drilling
Static water
level (date)
_>50
Density
Very Loose
Loose
Medium Dense
Dense
Very Dense
Consistency
Very Soft
Soft
Medium Stiff
Stiff
Very Stiff
Hard
<4
4 to 9
10 to 29
30 to 49
<2
2 to 3
4 to 7
8 to 14
15 to 29
_>30
LLC
EarthSolutionsNWLLC
Cobbles
GravelCoarse GravelFineGravel
Sand
Coarse Sand
Medium Sand
Fine Sand
Silt and Clay
Larger than 12"
3"to 12"
3"to No.4 (4.75 mm)3"to 3/4"3/4"to No.4 (4.75 mm)
No.4 (4.75 mm)to No.200 (0.075 mm)
No.4 (4.75 mm)to No.10 (2.00 mm)
No.10 (2.00 mm)to No.40 (0.425 mm)
No.40 (0.425 mm)to No.200 (0.075 mm)
354.7
352.5
346.0
GB
GB
MC = 9.5Fines = 8.6
MC = 13.7Fines = 9.6
GP
SP
SW-SM
Crushed rock base coarse, 3" (Fill)-geofabric at base
Brown poorly graded SAND, medium dense, damp (Fill)
-relic topsoil horizon
Brown well-graded SAND with silt and gravel, medium dense, damp to moist
-small-scale Pilot Infiltration Test at 3.5', probed 6"
[USDA Classification: gravelly SAND]
-becomes gray, slight caving to BOH
[USDA Classification: gravelly SAND]
Test pit terminated at 9.0 feet below existing grade. No groundwater encountered duringexcavation. Caving observed from 4.5 feet to BOH.
LIMITATIONS: Ground elevation (if listed) is approximate; the test location was notsurveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on
this test log as a standalone document. Refer to the text of the geotechnical report for acomplete understanding of subsurface conditions.
0.3
2.5
9.0
SA
M
P
L
E
T
Y
P
E
NU
M
B
E
R
DE
P
T
H
(f
t
)
0.0
2.5
5.0
7.5
PAGE 1 OF 1
TEST PIT NUMBER TP-301
CHECKED BY CGH
NOTES
SURFACE CONDITIONS Gravel
AT TIME OF EXCAVATIONAT TIME OF EXCAVATION
AFTER EXCAVATION
EXCAVATION CONTRACTOR NW Excavating
DATE STARTED 11/18/24 COMPLETED 11/18/24
GROUND WATER LEVEL:
GROUND ELEVATION 355 ft
LOGGED BY SKH
LATITUDE 47.50277 LONGITUDE -122.17999
PROJECT NUMBER ES-5719.08 PROJECT NAME Solera – Blocks C & D
GE
N
E
R
A
L
B
H
/
T
P
/
W
E
L
L
-
5
7
1
9
-
8
.
G
P
J
-
G
I
N
T
U
S
.
G
D
T
-
1
/
7
/
2
5
15365 NE 90th Street, Suite 100
Redmond, WA 98052
Office (425) 449-4704 | esnw.com
Branch Office: Pasco, WA
TESTS
U.
S
.
C
.
S
.
MATERIAL DESCRIPTION
GR
A
P
H
I
C
LO
G
342.0
334.0
GB
GB
MC = 9.1Fines = 25.0
MC = 10.5Fines = 30.7
TPSL
SM
Dark brown TOPSOIL, roots to 6" (Fill)
Brown silty SAND with gravel, medium dense, damp
-probed 5"
-becomes gray, dense
-probed 3"
-slight caving to BOH
-becomes gray
-small-scale Pilot Infiltration Test at 6.5'
[USDA Classification: gravelly sandy LOAM]
-becomes silty sand
[USDA Classification: gravelly sandy LOAM]
Test pit terminated at 9.0 feet below existing grade. No groundwater encountered duringexcavation. Caving observed from 4.0 feet to BOH.
LIMITATIONS: Ground elevation (if listed) is approximate; the test location was notsurveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on
this test log as a standalone document. Refer to the text of the geotechnical report for acomplete understanding of subsurface conditions.
1.0
9.0
SA
M
P
L
E
T
Y
P
E
NU
M
B
E
R
DE
P
T
H
(f
t
)
0.0
2.5
5.0
7.5
PAGE 1 OF 1
TEST PIT NUMBER TP-302
CHECKED BY CGH
NOTES
SURFACE CONDITIONS Grass
AT TIME OF EXCAVATIONAT TIME OF EXCAVATION
AFTER EXCAVATION
EXCAVATION CONTRACTOR NW Excavating
DATE STARTED 11/19/24 COMPLETED 11/19/24
GROUND WATER LEVEL:
GROUND ELEVATION 343 ft
LOGGED BY SKH
LATITUDE 47.50065 LONGITUDE -122.18228
PROJECT NUMBER ES-5719.08 PROJECT NAME Solera – Blocks C & D
GE
N
E
R
A
L
B
H
/
T
P
/
W
E
L
L
-
5
7
1
9
-
8
.
G
P
J
-
G
I
N
T
U
S
.
G
D
T
-
1
/
7
/
2
5
15365 NE 90th Street, Suite 100
Redmond, WA 98052
Office (425) 449-4704 | esnw.com
Branch Office: Pasco, WA
TESTS
U.
S
.
C
.
S
.
MATERIAL DESCRIPTION
GR
A
P
H
I
C
LO
G
346.0
339.0
338.0
GB
GB
MC = 8.4Fines = 6.1
MC = 13.1Fines = 17.8
TPSL
SP-SM
SM
Dark brown TOPSOIL, roots to 6" (Fill)
Brown poorly graded SAND with silt, medium dense, damp
-probed 7"
-slight caving to BOH
-small-scale Pilot Infiltration Test at 3.5'
[USDA Classification: slightly gravelly SAND]
Brown silty SAND, dense, damp
[USDA Classification: gravelly loamy SAND]
Test pit terminated at 9.0 feet below existing grade. No groundwater encountered duringexcavation. Caving observed from 2.5 feet to BOH.
LIMITATIONS: Ground elevation (if listed) is approximate; the test location was notsurveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on
this test log as a standalone document. Refer to the text of the geotechnical report for acomplete understanding of subsurface conditions.
1.0
8.0
9.0
SA
M
P
L
E
T
Y
P
E
NU
M
B
E
R
DE
P
T
H
(f
t
)
0.0
2.5
5.0
7.5
PAGE 1 OF 1
TEST PIT NUMBER TP-303
CHECKED BY CGH
NOTES
SURFACE CONDITIONS Grass
AT TIME OF EXCAVATIONAT TIME OF EXCAVATION
AFTER EXCAVATION
EXCAVATION CONTRACTOR NW Excavating
DATE STARTED 11/19/24 COMPLETED 11/19/24
GROUND WATER LEVEL:
GROUND ELEVATION 347 ft
LOGGED BY SKH
LATITUDE 47.50123 LONGITUDE -122.18144
PROJECT NUMBER ES-5719.08 PROJECT NAME Solera – Blocks C & D
GE
N
E
R
A
L
B
H
/
T
P
/
W
E
L
L
-
5
7
1
9
-
8
.
G
P
J
-
G
I
N
T
U
S
.
G
D
T
-
1
/
7
/
2
5
15365 NE 90th Street, Suite 100
Redmond, WA 98052
Office (425) 449-4704 | esnw.com
Branch Office: Pasco, WA
TESTS
U.
S
.
C
.
S
.
MATERIAL DESCRIPTION
GR
A
P
H
I
C
LO
G
353.0
347.0
345.0
GB
GB
MC = 14.0Fines = 10.8
MC = 11.9Fines = 21.5
TPSL
SW-SM
SM
Dark brown TOPSOIL, roots to 6" (Fill)
Brown well-graded SAND with silt, medium dense, damp to moist
-slight caving to BOH
-small-scale Pilot Infiltration Test at 4', probed 7"
[USDA Classification: slightly gravelly SAND]
Brown silty SAND with gravel, dense, damp
[USDA Classification: gravelly loamy SAND]
Test pit terminated at 9.0 feet below existing grade. No groundwater encountered duringexcavation. Caving observed from 3.0 feet to BOH.
LIMITATIONS: Ground elevation (if listed) is approximate; the test location was notsurveyed. Coordinates are approximate and based on the WGS84 datum. Do not rely on
this test log as a standalone document. Refer to the text of the geotechnical report for acomplete understanding of subsurface conditions.
1.0
7.0
9.0
SA
M
P
L
E
T
Y
P
E
NU
M
B
E
R
DE
P
T
H
(f
t
)
0.0
2.5
5.0
7.5
PAGE 1 OF 1
TEST PIT NUMBER TP-304
CHECKED BY CGH
NOTES
SURFACE CONDITIONS Grass
AT TIME OF EXCAVATIONAT TIME OF EXCAVATION
AFTER EXCAVATION
EXCAVATION CONTRACTOR NW Excavating
DATE STARTED 11/19/24 COMPLETED 11/19/24
GROUND WATER LEVEL:
GROUND ELEVATION 354 ft
LOGGED BY SKH
LATITUDE 47.50192 LONGITUDE -122.18078
PROJECT NUMBER ES-5719.08 PROJECT NAME Solera – Blocks C & D
GE
N
E
R
A
L
B
H
/
T
P
/
W
E
L
L
-
5
7
1
9
-
8
.
G
P
J
-
G
I
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U
S
.
G
D
T
-
1
/
7
/
2
5
15365 NE 90th Street, Suite 100
Redmond, WA 98052
Office (425) 449-4704 | esnw.com
Branch Office: Pasco, WA
TESTS
U.
S
.
C
.
S
.
MATERIAL DESCRIPTION
GR
A
P
H
I
C
LO
G
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
0.0010.010.1110100
10.82
8.52
3.50
LL
TP-301
TP-301
TP-302
TP-302
TP-303
0.088
0.079
0.099
3/4U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS
GRAVEL SAND
37.5
37.5
37.5
37.5
9.5
%Silt
1.03
1.08
1.27
TP-301
TP-301
TP-302
TP-302
TP-303
2 2003
Cc CuClassification
%Clay
16
PID60 D30
coarse SILT OR CLAYfinemedium
GRAIN SIZE IN MILLIMETERS
3/8 50
3.5ft.
9.0ft.
6.5ft.
9.0ft.
3.5ft.
3.50ft.
9.00ft.
6.50ft.
9.00ft.
3.50ft.
PL
3
D100
140
Specimen Identification
1
fine
6 HYDROMETER304
8.6
9.6
25.0
30.7
6.1
101/2
COBBLES
Specimen Identification
4
coarse
20 401.5 8 14
USDA: Brown Gravelly Sand. USCS: SW-SM with Gravel.
USDA: Gray Gravelly Sand. USCS: SW-SM with Gravel.
USDA: Gray Gravelly Sandy Loam. USCS: SM with Gravel.
USDA: Gray Gravelly Sandy Loam. USCS: SM.
USDA: Brown Slightly Gravelly Sand. USCS: SP-SM.
6 60
PE
R
C
E
N
T
F
I
N
E
R
B
Y
W
E
I
G
H
T
D10
0.292
0.238
0.108
0.066
0.21
0.948
0.669
0.451
0.398
0.348
GRAIN SIZE DISTRIBUTION
100
PROJECT NUMBER ES-5719.08 PROJECT NAME Solera - Blocks C & D
GR
A
I
N
S
I
Z
E
U
S
D
A
E
S
-
5
7
1
9
.
0
8
S
O
L
E
R
A
–
B
L
O
C
K
S
C
&
D
.
G
P
J
G
I
N
T
U
S
L
A
B
.
G
D
T
1
/
3
/
2
5
15365 NE 90th Street, Suite 100Redmond, WA 98052Office (425) 449-4704 | esnw.comBranch Office: Pasco, WA
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
0.0010.010.1110100
8.19
LL
TP-303
TP-304
TP-304
0.06
3/4U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS
GRAVEL SAND
19
19
19
%Silt
2.62
TP-303
TP-304
TP-304
2 2003
Cc CuClassification
%Clay
16
PID60 D30
coarse SILT OR CLAYfinemedium
GRAIN SIZE IN MILLIMETERS
3/8 50
9.0ft.
4.0ft.
9.0ft.
9.00ft.
4.00ft.
9.00ft.
PL
3
D100
140
Specimen Identification
1
fine
6 HYDROMETER304
17.8
10.8
21.5
101/2
COBBLES
Specimen Identification
4
coarse
20 401.5 8 14
USDA: Gray Gravelly Loamy Sand. USCS: SM.
USDA: Brown Slightly Gravelly Sand. USCS: SW-SM.
USDA: Gray Gravelly Loamy Sand. USCS: SM with Gravel.
6 60
PE
R
C
E
N
T
F
I
N
E
R
B
Y
W
E
I
G
H
T
D10
0.166
0.276
0.16
0.448
0.489
0.463
GRAIN SIZE DISTRIBUTION
100
PROJECT NUMBER ES-5719.08 PROJECT NAME Solera - Blocks C & D
GR
A
I
N
S
I
Z
E
U
S
D
A
E
S
-
5
7
1
9
.
0
8
S
O
L
E
R
A
–
B
L
O
C
K
S
C
&
D
.
G
P
J
G
I
N
T
U
S
L
A
B
.
G
D
T
1
/
3
/
2
5
15365 NE 90th Street, Suite 100Redmond, WA 98052Office (425) 449-4704 | esnw.comBranch Office: Pasco, WA
Solera Phase 2: Block C and Block D – New Home Co.
Appendix M
Appendix M
Infiltration Test Report Memorandum
N
Approved Preliminary Plat Drainage Report
.
Solera Subdivision
Drainage Report
July 2018
Solera Subdivision
i
Drainage Report
2018
Prepared for:
Quadrant Homes
15900 SE. Eastgate Way, Suite 300
Bellevue, WA 98008
Prepared by:
Jeremy Febus, PE, LEED AP
KPFF Consulting Engineers
1601 Fifth Avenue, Suite 1600
Seattle, WA 98101
(206) 622-5822
KPFF Project No. 117659
July
KPFF Consulting Engineers
ii
This Page Intentionally Left Blank
Solera Subdivision
iii
Table of Contents
1. 1. Project Overview ....................................................................................................... 1
2. 2. Existing Conditions ................................................................................................... 2
3. 3. Conditions and Requirements Summary...................................................................... 3
Core Requirement No. 1: Discharge at The natural Location ...................................................... 3
Core Requirement No. 2: Offsite Analysis .................................................................................. 3
Core Requirement No. 3: Flow Control ....................................................................................... 3
Core Requirement No. 4: Conveyance System ........................................................................... 3
Core Requirement No. 5: Construction Stormwater Pollution prevention .................................. 3
Core Requirement No. 6: Maintenance and Operations ............................................................. 3
Core Requirement No. 7: Financial Guarantees and Liability ....................................................... 3
Core Requirement No. 8: water quality ...................................................................................... 3
Core Requirement No. 9: On-Site BMPS .................................................................................... 4
special requirement No. 1: Other Adopted Area-Specific Requirements ..................................... 4
special requirement No. 2: Flood Hazard Area Delineation ......................................................... 4
special requirement No. 3: Flood Protection Facilities ................................................................. 4
special requirement No. 4: Source Control .................................................................................. 4
special requirement No. 5: oil control .......................................................................................... 4
special requirement No. 6: aquifer protection areas .................................................................... 4
4. 4. Off-Site Analysis ....................................................................................................... 4
3.1 upstream analysis .................................................................................................................. 4
3.2 Downstream analysis ............................................................................................................ 4
5. 5. Flow Control Analysis and Design ............................................................................... 7
6. 6. Water Quality Analysis and Design ............................................................................. 8
6.1 Water Quality Requirement .................................................................................................. 9
6.2 On-site BMP Requirement .................................................................................................... 9
7. 7. Conveyance System Analysis and Design .................................................................. 10
8. 8. Esc Analysis and Design ........................................................................................... 10
9. 9. Special Reports and Studies ..................................................................................... 10
10. 10. Bond Quantities and Declaration of Covenant .......................................................... 10
KPFF Consulting Engineers
iv
List of Figures
Figure 1-1: Site Map .................................................................................................................................. 1
Figure 1-2: Site Topography ...................................................................................................................... 2
Figure 4-1: Predeveloped Areas ................................................................................................................ 7
Figure 4-2: Developed Areas ..................................................................................................................... 8
Figure 5-1: Surface Runoff Basins .............................................................................................................. 9
List of Tables
Table 4-1: MGS Flood Peak Flow Rate Results ........................................................................................... 8
Appendices
Appendix A
Existing Conditions Site Map
Proposed Conditions Site Plan
Appendix B
Flow Control Applications Map
MGS Flood Peak Flow Report
MGS Flood Bioretention Report
Appendix C
Geotechnical Report
Infiltration Test Report
Drainage Report – Solera Unit Lot Subdivision
Appendix A
1. Project Overview
The Solera Subdivision is a proposed residential and mixed use development at the northern corner of NE 10th
Ave and Sunset Blvd in Renton, Washington. The project consists of 151 for-sale town home units,
approximately 521 apartment units and roughly 39,000 sq ft of non-residential or commercial space. The
project consists of 6 existing parcels which will be subdivided into 7 parcels including realignment and
dedication of a portion of Jefferson Avenue NE ROW totaling 11.8 acres (Figure 1-1). The realigned and
expanded public right-of-ways will bisect the site connecting NE 12th Street to NE 10th Street and Harrington
Place to NE Sunset Boulevard. Additional frontage ROW dedications will be provides as well.
Figure 1-1: Site Map
SITE
KPFF Consulting Engineers
2
2. Existing Conditions
The site is substantially developed and paved in its existing condition. The current use, the Greater Hi-Lands
Shopping Center and its accompanying surface parking lot occupy the majority of the site. A 1.1 acre parcel, in
the southwest corner of the site, is undeveloped - consisting of lawn and gravel. The majority of the site slopes
to the southwest at grades of 2-5%. The northern extent of the project site, near the existing US Bank building,
slopes toward NE 12th St at grades of 2-5%. See Figure 2-1 for an overview of site topography.
Figure 1-2: Site Topography
Drainage Report – Solera Unit Lot Subdivision
Appendix A
3. Conditions and Requirements Summary
In compliance to the City of Renton city code, proposed development shall be in accordance with a city
amended version of the 2016 King County Surface Water Manual City titled The Renton Surface Water Manual
(RSWM).
CORE REQUIREMENT NO. 1: DISCHARGE AT THE NATURAL LOCATION
The project proposes to connect to existing public stormwater conveyance systems in NE 10th St and NE 12th
St. These storm drains converge within ¼ mile downstream.
CORE REQUIREMENT NO. 2: OFFSITE ANALYSIS
An offsite analysis has been conducted, see Section 3.
CORE REQUIREMENT NO. 3: FLOW CONTROL
According to the Flow Control Application Map, from the RSWM the development is required to meet the Peak
Rate Flow Control Standard – Match Existing. Developed flows must match 2, 10 and 100-yr peak flows which
existed on site prior to May 1979. Existing improvements on the site were built in phases over a range of
years from 1958 to 1977, and so for the purposes of this analysis, “existing conditions” are defined as the
current land use.
CORE REQUIREMENT NO. 4: CONVEYANCE SYSTEM
Proposed conveyance system elements, both onsite and offsite, shall be analyzed, designed and constructed
according to RSWM requirements. Conveyance system calculations will be provided during construction
document permitting following entitlement.
CORE REQUIREMENT NO. 5: CONSTRUCTION STORMWATER POLLUTION
PREVENTION
Erosion and Sediment Control measures and Stormwater Pollution Prevention and Spill Control measures will
be applied through a Construction Stormwater Pollution Prevention (CSWPP) plan to be prepared during
construction permitting.
CORE REQUIREMENT NO. 6: MAINTENANCE AND OPERATIONS
Operation and Maintenance measures for stormwater infrastructure will be provided prior to Final Plat
Submittal.
CORE REQUIREMENT NO. 7: FINANCIAL GUARANTEES AND LIABILITY
Bond quantities for the City of Renton will be provided prior to construction permitting.
CORE REQUIREMENT NO. 8: WATER QUALITY
The project is required to apply Enhanced Basic WQ treatment due to the Commercial and multifamily land
uses. To achieve this bioretention facilities have been proposed throughout the site, See Section 5 for a more
detailed analysis.
KPFF Consulting Engineers
4
CORE REQUIREMENT NO. 9: ON-SITE BMPS
The project is satisfying the on-site BMP requirement by demonstrating compliance with the LID Performance
Standard as described in Section 1.2.9.1.B in the RSWM. The LID Performance standard is being achieved
through the use of bioretention facilities dispersed throughout the development. See Section 6 for a more
detailed analysis.
SPECIAL REQUIREMENT NO. 1: OTHER ADOPTED AREA-SPECIFIC
REQUIREMENTS
This project is within the Sunset Area Surface Water Master Plan (CH2M HILL, 2011) which requires the
developer to install an 8 ft wide bioretention facility along the south side of NE 12th St.
SPECIAL REQUIREMENT NO. 2: FLOOD HAZARD AREA DELINEATION
This project is not located in a flood hazard area.
SPECIAL REQUIREMENT NO. 3: FLOOD PROTECTION FACILITIES
This project does not modify or use a flood protection facility.
SPECIAL REQUIREMENT NO. 4: SOURCE CONTROL
Source control requirements apply to projects proposing a commercial building or which require a Commercial
Site Development permit. The commercial development will apply the appropriate BMP’s required during
building permits.
SPECIAL REQUIREMENT NO. 5: OIL CONTROL
The project does not classify as a high use site and is thus exempt from the Special Requirement #5.
SPECIAL REQUIREMENT NO. 6: AQUIFER PROTECTION AREAS
The project is within wellhead protection zone 2. However, the project is not proposing any of the drainage
facilities mentioned in Section 1.3.6 of the RSWM and thus special requirement No. 6 is not applicable.
4. Off-Site Analysis
3.1 UPSTREAM ANALYSIS
The site is on a ridgeline. There are no upstream basins that drain onto the project site.
3.2 DOWNSTREAM ANALYSIS
Approximately 90% of the existing development drains to the southwest, where it is collected in the public
conveyance systems within NE 10th St. The Sunset Neighborhood park, directly across NE 10th St, has sized
their bioretention cells to accommodate 0.77 acres of the flow from our site, while the rest of this runoff is
conveyed west along 10th St toward Sunset Blvd. The remaining approximately 10% of existing runoff flows, to
the north, where it discharges to the public stormwater conveyance system within NE 12th St. Flow from all of
three of these discharge locations converge within ¼ mile downstream.
The downstream path for this site’s runoff is contained within a piped public conveyance system.
Approximately 1 mile downstream, the piped system crosses under Interstate 405 and outfalls into a series of
Drainage Report – Solera Unit Lot Subdivision
Appendix A
wetlands. Runoff flows through the wetlands until it reaches a creek which flows to Lake Washington. The
Sunset Area Storm Water Master Plan notes that there are no known capacity issues in the drainage system
downstream of our site.
KPFF Consulting Engineers
6
Figure 3-1: 1-Mile Downstream Flow Path
Drainage Report – Solera Unit Lot Subdivision
Appendix A
5. Flow Control Analysis and Design
According to the Flow Control Application Map the project falls within the Peak Flow Control Standard (Existing
Site conditions) Region (see Appendix B). This standard states that the 2, 10 and 100 yr peak flows for
developed conditions must be less than peak flows that existed on site prior to May 1979.
The King County Assessor’s Reports indicate that the latest improvements to the developed parcels were
made in 1977. Street frontages being improved (Sunset Blvd, Harrington Pl, Kirkland Avenue NE, and NE 12th
St) were all assumed to their current condition prior to the on-site parcels. See Figures 4-1 and 4-2 for a
comparison of impervious and pervious surfaces in the existing and developed conditions. For this reason
existing surveyed conditions were modeled as existing conditions in this analysis.
Figure 5-1: Predeveloped Areas
KPFF Consulting Engineers
8
Figure 5-2: Developed Areas
Table 5-1: MGS Flood Peak Flow Rate Results
The proposed improvements to the site will create more pervious surface than existed in May 1979. As a
result, without the implementation of any flow control measures, te developed peak flows are less than
predeveloped peak flows in the 2, 10 and 100yr condition – complying with Core Requirement #3.
6. Water Quality Analysis and LID Performance Standard
Design
The project is proposing to construct infiltrating bioretention cells to satisfy both Core Requirement No. 8
Water Quality and Core Requirement No. 9 On-site BMPs.
Predeveloped Peak Flows Developed Peak Flows
2 yr 4.35 cfs 3.92 cfs
10 yr 6.42 cfs 5.90 cfs
100 yr 11.34 cfs 10.64 cfs
Drainage Report – Solera Unit Lot Subdivision
Appendix A
6.1 WATER QUALITY REQUIREMENT
Over 50% of the developed site will be commercial and multifamily land use. According to the RSWM this
triggers the need for Enhanced Basic Water Quality treatment. The treatment goal of Enhanced Basic Water
Requirement can be achieved by treating targeted surface runoff with bioretention (Enhanced Basic Option 4,
6.1.2 RSWM).
The project site has been subdivided into 56 sub-basins (Figure 5-1)
Figure 5-1: Surface Runoff Basins
The grading approach in each of these sub-basins is such that runoff will sheet flow from new PGIS and drain
through a curb cut into a bioretention facility. Runoff will be treated in the bioretention cells and infiltrate into
native soils. Additionally, the surface runoff from street frontage improvements will be treated using
bioretention cells (basins 47-56). Bioretention facilities have been sized using MGS Flood methodology to treat
91% of runoff entering the cell. An infiltration rate of 6 in/hr was used for the amended soil and an infiltration
rate of 0.7 in/hr was used for the underlying native soils consistent with infiltration test results completed by
Earth Solutions Northwest LLC (report in Appendix C). It should be noted that the 0.7 in/hr is a conservative
infiltration rate. Rates ranging from 2 in/hr – 20 in/hr were tested on site, but the lowest rate was used along
with a correction factor to. The MGS Flood Report demonstrating compliance is located in Appendix B.
6.2 ON-SITE BMP REQUIREMENT
According to section 1.2.9 of the RWSM, Core Requirement #9 can be satisfied by,
1) application of BMPs to the maximum extent feasible
2) or by using a continuous runoff model to demonstrate compliance with the Low Impact Development
(LID) Performance Standard.
KPFF Consulting Engineers
10
This development has opted to use the LID performance Standard. In order to comply with this standard,
“Stormwater discharges shall match developed discharge durations to pre-developed durations for the range
of pre-developed discharge rates from 8% of the 2-year peak flow to 50% of the 2-yr peak flows.” These
durations must be matched through the modeling of on-site BMPs —bioretention has been chosen for this
development. Using the same basins and infiltration rates as in section 6.1, each individual basin was modeled
to LID duration standards using MGS Flood Methodology. It was found that the LID performance standard
generated bioretention facilities smaller in size than what is needed to meet water quality standards. For this
reason, all bioretention facilities were sized to water quality standards, i.e. 91% of runoff treated. MGS Flood
Reports in Appendix B show results for both water quality and LID performance standard.
6.2 ON-SITE BMP MIXED USE LOTS
Mixed-use lots will use a combination of green-roof and ground level bio-retention planters to achieve 100% of
the LID performance standard. Meeting this requirement strictly through the use of bio-retention planters
would require approximately 2800 square feet of planter area on each mixed use parcel. The preliminary
drainage plan demonstrates that area in excess of this amount is available adjacent to the building structures.
The actual BMP sizing and placement will be refined and fully documented through individual site plan
entitlements for each mixed-use parcel.
7. Conveyance System Analysis and Design
No existing capacity issues are known within the downstream conveyance system. A detailed analysis will be
performed for the projects receiving conveyance system during construction document permitting. Proposed
conveyance system elements, both onsite and offsite, shall be analyzed, designed and constructed according
to RSWM requirements. Conveyance system calculations will be provided during construction document
permitting following entitlement.
8. Esc Analysis and Design
Erosion and Sediment Control measures and Stormwater Pollution Prevention and Spill Control measures will
be applied through a Construction Stormwater Pollution Prevention (CSWPP) plan.
9. Special Reports and Studies
The Sunset Area Surface water Master Plan (CH2M HILL, 2011) discusses the City of Renton’s surface water
management program within the Sunset Area. The Master Plan requires this project to install an 8’ bioretention
facility along the south side of NE 12th St.
10. Bond Quantities and Declaration of Covenant
Bond quantities for the City of Renton will be provided prior to construction permitting.
Drainage Report – Solera Unit Lot Subdivision
Appendix A
KPFF Consulting Engineers
12
Appendix A
1. Existing Conditions Site Map
2. Proposed Conditions Site Plan
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1601 5th Avenue, Suite 1600
Seattle, WA 98101
206.622.5822
www.kpff.com
PERVIOUS: 3.17 ACRES
IMPERVIOUS = 9.43 ACRES
SUNSET BLVD
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DEVELOPED CONDITIONS
Drainage Report - Rose Hill Subdivision
Appendix B
Appendix B
1. Flow Control Applications Map
2. MGS Flood Peak Flow Report
3. MGS Flood Bioretention Report
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Flow Control Application Map
Reference 15-A
Date: 01/09/2014
Flow Control Standards
Peak Rate Flow Control Standard (Existing Site Conditions)
Flow Control Duration Standard (Existing Site Conditions)
Flow Control Duration Standard (Forested Conditions)
Flood Problem Flow
Unincorporated King County Flow Control Standards
Renton City Limits
Potential Annexation Area
PROJECT SITE
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.43
Program License Number: 200410007
Project Simulation Performed on: 03/08/2018 7:02 PM
Report Generation Date: 03/08/2018 7:04 PM
—————————————————————————————————
Input File Name: Biroetnetion WQ V BMP.fld
Project Name: Solera Subdivision
Analysis Title: Bioretention WQvBMP
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Climatic Region Number: 0
Full Period of Record Available used for Routing
Precipitation Station : 95004005 Puget West 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 951040 Puget West 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 0.100 0.100
Area of Links that Include Precip/Evap (acres) 0.000 0.001
Total (acres) 0.100 0.101
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
Impervious 0.100
----------------------------------------------
Subbasin Total 0.100
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
Impervious 0.100
----------------------------------------------
Subbasin Total 0.100
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
FLOW CONTROL
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: New Bio Lnk1
Link Type: Bioretention Facility
Downstream Link: None
Base Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 103.00
Storage Depth (ft) : 3.00
Bottom Length (ft) : 5.0
Bottom Width (ft) : 6.0
Side Slopes (ft/ft) : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00
Bottom Area (sq-ft) : 30.
Area at Riser Crest El (sq-ft) : 552.
(acres) : 0.013
Volume at Riser Crest (cu-ft) : 717.
(ac-ft) : 0.016
Infiltration on Bottom only Selected
Soil Properties
Biosoil Thickness (ft) : 1.00
Biosoil Saturated Hydraulic Conductivity (in/hr) : 2.00
Biosoil Porosity (Percent) : 20.00
Maximum Elevation of Bioretention Soil : 101.00
Native Soil Hydraulic Conductivity (in/hr) : 0.50
Underdrain Present
Orifice NOT Present in Under Drain
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 103.00 ft
Hydraulic Structure Geometry
Number of Devices: 0
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
********** Link: New Bio Lnk1 ********** Link WSEL Stats
WSEL Frequency Data(ft)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) WSEL Peak (ft)
======================================
1.05-Year 102.564
1.11-Year 102.778
1.25-Year 103.003
2.00-Year 103.023
3.33-Year 103.029
5-Year 103.034
10-Year 103.038
25-Year 103.046
50-Year 103.048
100-Year 103.049
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 0.000
_____________________________________
Total: 0.000
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 0.000
Link: New Bio Lnk1 0.000
_____________________________________
Total: 0.000
Total Predevelopment Recharge Equals Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 0.000 ac-ft/year, Post Developed: 0.000 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: New Bio Lnk1 **********
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 45.20
Inflow Volume Including PPT-Evap (ac-ft): 47.23
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 43.78, 92.69%
Primary Outflow To Downstream System (ac-ft): 47.18
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 92.69%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: New Bio Lnk1
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 3.814E-02 2-Year 1.928E-02
5-Year 4.963E-02 5-Year 3.534E-02
10-Year 5.581E-02 10-Year 4.216E-02
25-Year 6.500E-02 25-Year 5.376E-02
50-Year 8.392E-02 50-Year 5.666E-02
100-Year 9.771E-02 100-Year 5.929E-02
200-Year 0.101 200-Year 5.938E-02
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** Flow Duration Performance ****
Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -71.9% PASS
Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -58.0% PASS
Maximum Excursion from Q2 to Q50 (Must be less than 10%): -57.2% PASS
Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -91.4% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -71.9% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.43
Program License Number: 200410007
Project Simulation Performed on: 07/04/2018 2:10 PM
Report Generation Date: 07/04/2018 2:10 PM
—————————————————————————————————
Input File Name: Basin 1.fld
Project Name: Solera
Analysis Title: BMP Performance Standard
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Climatic Region Number: 0
Full Period of Record Available used for Routing
Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 961040 Puget East 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 1.000 0.295
Area of Links that Include Precip/Evap (acres) 0.000 0.008
Total (acres) 1.000 0.303
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
Till Forest 1.000
----------------------------------------------
Subbasin Total 1.000
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Impervious ----------
-------Area (Acres) --------
Till Grass 0.107
Impervious 0.188
----------------------------------------------
Subbasin Total 0.295
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
BIORETENTION SIZING. MODELING
RESULTS FOR BASINS 1-10 ARE
PROVIDED. ALL BIORETENTION BASINS
WILL BE PROVIDED UPON CITY REQUEST.
BASIN 1
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: iMPERVIOUS BIO
Link Type: Bioretention Facility
Downstream Link: None
Base Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 25.0
Bottom Width (ft) : 14.0
Side Slopes (ft/ft) : L1= 0.00 L2= 0.00 W1= 0.00 W2= 0.00
Bottom Area (sq-ft) : 350.
Area at Riser Crest El (sq-ft) : 350.
(acres) : 0.008
Volume at Riser Crest (cu-ft): 333.
(ac-ft) : 0.008
Infiltration on Bottom only Selected
Soil Properties
Biosoil Thickness (ft) : 1.50
Biosoil Saturated Hydraulic Conductivity (in/hr) : 6.00
Biosoil Porosity (Percent) : 30.00
Maximum Elevation of Bioretention Soil : 101.00
Native Soil Hydraulic Conductivity (in/hr) : 0.70
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 172.429
_____________________________________
Total: 172.429
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Impervious 13.077
Link: iMPERVIOUS BIO 99.700
_____________________________________
Total: 112.776
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 1.091 ac-ft/year, Post Developed: 0.714 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: iMPERVIOUS BIO **********
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 105.81
Inflow Volume Including PPT-Evap (ac-ft): 109.04
Total Runoff Infiltrated (ac-ft): 99.70, 91.43%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 9.24
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 91.43%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: iMPERVIOUS BIO
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 2.131E-02 2-Year 5.415E-02
5-Year 3.473E-02 5-Year 8.402E-02
10-Year 4.680E-02 10-Year 9.703E-02
25-Year 5.933E-02 25-Year 0.123
50-Year 7.572E-02 50-Year 0.157
100-Year 8.205E-02 100-Year 0.172
200-Year 0.128 200-Year 0.184
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -94.6% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -77.0% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.43
Program License Number: 200410007
Project Simulation Performed on: 07/04/2018 2:14 PM
Report Generation Date: 07/04/2018 2:14 PM
—————————————————————————————————
Input File Name: Basin 1.fld
Project Name: Solera
Analysis Title: BMP Performance Standard
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Climatic Region Number: 0
Full Period of Record Available used for Routing
Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 961040 Puget East 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 1.000 0.128
Area of Links that Include Precip/Evap (acres) 0.000 0.004
Total (acres) 1.000 0.132
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
Till Forest 1.000
----------------------------------------------
Subbasin Total 1.000
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Basin2 ----------
-------Area (Acres) --------
Till Grass 0.022
Impervious 0.106
----------------------------------------------
Subbasin Total 0.128
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
BASIN 2
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: iMPERVIOUS BIO
Link Type: Bioretention Facility
Downstream Link: None
Base Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 21.0
Bottom Width (ft) : 9.0
Side Slopes (ft/ft) : L1= 0.00 L2= 0.00 W1= 0.00 W2= 0.00
Bottom Area (sq-ft) : 189.
Area at Riser Crest El (sq-ft) : 189.
(acres) : 0.004
Volume at Riser Crest (cu-ft): 180.
(ac-ft) : 0.004
Infiltration on Bottom only Selected
Soil Properties
Biosoil Thickness (ft) : 1.50
Biosoil Saturated Hydraulic Conductivity (in/hr) : 6.00
Biosoil Porosity (Percent) : 30.00
Maximum Elevation of Bioretention Soil : 101.00
Native Soil Hydraulic Conductivity (in/hr) : 0.70
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 172.429
_____________________________________
Total: 172.429
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Basin2 2.628
Link: iMPERVIOUS BIO 49.181
_____________________________________
Total: 51.808
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 1.091 ac-ft/year, Post Developed: 0.328 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: iMPERVIOUS BIO **********
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 51.85
Inflow Volume Including PPT-Evap (ac-ft): 53.64
Total Runoff Infiltrated (ac-ft): 49.18, 91.68%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 4.40
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 91.68%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: iMPERVIOUS BIO
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 2.131E-02 2-Year 2.853E-02
5-Year 3.473E-02 5-Year 4.420E-02
10-Year 4.680E-02 10-Year 4.976E-02
25-Year 5.933E-02 25-Year 6.145E-02
50-Year 7.572E-02 50-Year 6.910E-02
100-Year 8.205E-02 100-Year 8.113E-02
200-Year 0.128 200-Year 8.887E-02
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -96.1% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -91.1% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.43
Program License Number: 200410007
Project Simulation Performed on: 07/04/2018 2:17 PM
Report Generation Date: 07/04/2018 2:18 PM
—————————————————————————————————
Input File Name: Basin 1.fld
Project Name: Solera
Analysis Title: BMP Performance Standard
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Climatic Region Number: 0
Full Period of Record Available used for Routing
Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 961040 Puget East 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 1.000 0.137
Area of Links that Include Precip/Evap (acres) 0.000 0.004
Total (acres) 1.000 0.141
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
Till Forest 1.000
----------------------------------------------
Subbasin Total 1.000
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Basin 3 ----------
-------Area (Acres) --------
Till Grass 0.046
Impervious 0.091
----------------------------------------------
Subbasin Total 0.137
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
BASIN 3
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: iMPERVIOUS BIO
Link Type: Bioretention Facility
Downstream Link: None
Base Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 21.0
Bottom Width (ft) : 8.0
Side Slopes (ft/ft) : L1= 0.00 L2= 0.00 W1= 0.00 W2= 0.00
Bottom Area (sq-ft) : 168.
Area at Riser Crest El (sq-ft) : 168.
(acres) : 0.004
Volume at Riser Crest (cu-ft): 160.
(ac-ft) : 0.004
Infiltration on Bottom only Selected
Soil Properties
Biosoil Thickness (ft) : 1.50
Biosoil Saturated Hydraulic Conductivity (in/hr) : 6.00
Biosoil Porosity (Percent) : 30.00
Maximum Elevation of Bioretention Soil : 101.00
Native Soil Hydraulic Conductivity (in/hr) : 0.70
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 172.429
_____________________________________
Total: 172.429
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Basin 3 5.622
Link: iMPERVIOUS BIO 47.325
_____________________________________
Total: 52.946
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 1.091 ac-ft/year, Post Developed: 0.335 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: iMPERVIOUS BIO **********
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 50.23
Inflow Volume Including PPT-Evap (ac-ft): 51.79
Total Runoff Infiltrated (ac-ft): 47.32, 91.38%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 4.41
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 91.38%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: iMPERVIOUS BIO
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 2.131E-02 2-Year 2.721E-02
5-Year 3.473E-02 5-Year 4.074E-02
10-Year 4.680E-02 10-Year 4.692E-02
25-Year 5.933E-02 25-Year 5.807E-02
50-Year 7.572E-02 50-Year 7.312E-02
100-Year 8.205E-02 100-Year 8.714E-02
200-Year 0.128 200-Year 8.779E-02
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -95.7% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -92.3% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.43
Program License Number: 200410007
Project Simulation Performed on: 07/04/2018 2:19 PM
Report Generation Date: 07/04/2018 2:19 PM
—————————————————————————————————
Input File Name: Basin 1.fld
Project Name: Solera
Analysis Title: BMP Performance Standard
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Climatic Region Number: 0
Full Period of Record Available used for Routing
Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 961040 Puget East 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 1.000 0.088
Area of Links that Include Precip/Evap (acres) 0.000 0.003
Total (acres) 1.000 0.091
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
Till Forest 1.000
----------------------------------------------
Subbasin Total 1.000
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Basin 4 ----------
-------Area (Acres) --------
Till Grass 0.016
Impervious 0.072
----------------------------------------------
Subbasin Total 0.088
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
BASIN 4
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: iMPERVIOUS BIO
Link Type: Bioretention Facility
Downstream Link: None
Base Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 21.0
Bottom Width (ft) : 6.0
Side Slopes (ft/ft) : L1= 0.00 L2= 0.00 W1= 0.00 W2= 0.00
Bottom Area (sq-ft) : 126.
Area at Riser Crest El (sq-ft) : 126.
(acres) : 0.003
Volume at Riser Crest (cu-ft): 120.
(ac-ft) : 0.003
Infiltration on Bottom only Selected
Soil Properties
Biosoil Thickness (ft) : 1.50
Biosoil Saturated Hydraulic Conductivity (in/hr) : 6.00
Biosoil Porosity (Percent) : 30.00
Maximum Elevation of Bioretention Soil : 101.00
Native Soil Hydraulic Conductivity (in/hr) : 0.70
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 172.429
_____________________________________
Total: 172.429
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Basin 4 1.955
Link: iMPERVIOUS BIO 33.472
_____________________________________
Total: 35.427
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 1.091 ac-ft/year, Post Developed: 0.224 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: iMPERVIOUS BIO **********
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 35.50
Inflow Volume Including PPT-Evap (ac-ft): 36.69
Total Runoff Infiltrated (ac-ft): 33.47, 91.23%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 3.18
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 91.23%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: iMPERVIOUS BIO
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 2.131E-02 2-Year 2.083E-02
5-Year 3.473E-02 5-Year 3.055E-02
10-Year 4.680E-02 10-Year 3.582E-02
25-Year 5.933E-02 25-Year 4.278E-02
50-Year 7.572E-02 50-Year 5.197E-02
100-Year 8.205E-02 100-Year 5.864E-02
200-Year 0.128 200-Year 6.138E-02
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -96.4% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -95.8% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.43
Program License Number: 200410007
Project Simulation Performed on: 07/04/2018 2:21 PM
Report Generation Date: 07/04/2018 2:21 PM
—————————————————————————————————
Input File Name: Basin 1.fld
Project Name: Solera
Analysis Title: BMP Performance Standard
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Climatic Region Number: 0
Full Period of Record Available used for Routing
Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 961040 Puget East 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 1.000 0.176
Area of Links that Include Precip/Evap (acres) 0.000 0.006
Total (acres) 1.000 0.181
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
Till Forest 1.000
----------------------------------------------
Subbasin Total 1.000
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Basin 5 ----------
-------Area (Acres) --------
Till Grass 0.034
Impervious 0.142
----------------------------------------------
Subbasin Total 0.176
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
BASIN 5
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: iMPERVIOUS BIO
Link Type: Bioretention Facility
Downstream Link: None
Base Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 23.0
Bottom Width (ft) : 11.0
Side Slopes (ft/ft) : L1= 0.00 L2= 0.00 W1= 0.00 W2= 0.00
Bottom Area (sq-ft) : 253.
Area at Riser Crest El (sq-ft) : 253.
(acres) : 0.006
Volume at Riser Crest (cu-ft): 240.
(ac-ft) : 0.006
Infiltration on Bottom only Selected
Soil Properties
Biosoil Thickness (ft) : 1.50
Biosoil Saturated Hydraulic Conductivity (in/hr) : 6.00
Biosoil Porosity (Percent) : 30.00
Maximum Elevation of Bioretention Soil : 101.00
Native Soil Hydraulic Conductivity (in/hr) : 0.70
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 172.429
_____________________________________
Total: 172.429
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Basin 5 4.094
Link: iMPERVIOUS BIO 66.660
_____________________________________
Total: 70.754
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 1.091 ac-ft/year, Post Developed: 0.448 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: iMPERVIOUS BIO **********
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 70.40
Inflow Volume Including PPT-Evap (ac-ft): 72.79
Total Runoff Infiltrated (ac-ft): 66.66, 91.57%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 6.06
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 91.57%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: iMPERVIOUS BIO
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 2.131E-02 2-Year 3.842E-02
5-Year 3.473E-02 5-Year 5.963E-02
10-Year 4.680E-02 10-Year 6.619E-02
25-Year 5.933E-02 25-Year 8.314E-02
50-Year 7.572E-02 50-Year 9.421E-02
100-Year 8.205E-02 100-Year 0.110
200-Year 0.128 200-Year 0.121
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -95.6% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -85.6% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.43
Program License Number: 200410007
Project Simulation Performed on: 07/04/2018 2:25 PM
Report Generation Date: 07/04/2018 2:25 PM
—————————————————————————————————
Input File Name: Basin 1.fld
Project Name: Solera
Analysis Title: BMP Performance Standard
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Climatic Region Number: 0
Full Period of Record Available used for Routing
Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 961040 Puget East 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 1.000 0.111
Area of Links that Include Precip/Evap (acres) 0.000 0.003
Total (acres) 1.000 0.114
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
Till Forest 1.000
----------------------------------------------
Subbasin Total 1.000
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Basin 6 ----------
-------Area (Acres) --------
Till Grass 0.038
Impervious 0.073
----------------------------------------------
Subbasin Total 0.111
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
BASIN 6
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: iMPERVIOUS BIO
Link Type: Bioretention Facility
Downstream Link: None
Base Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 19.0
Bottom Width (ft) : 7.0
Side Slopes (ft/ft) : L1= 0.00 L2= 0.00 W1= 0.00 W2= 0.00
Bottom Area (sq-ft) : 133.
Area at Riser Crest El (sq-ft) : 133.
(acres) : 0.003
Volume at Riser Crest (cu-ft): 126.
(ac-ft) : 0.003
Infiltration on Bottom only Selected
Soil Properties
Biosoil Thickness (ft) : 1.50
Biosoil Saturated Hydraulic Conductivity (in/hr) : 6.00
Biosoil Porosity (Percent) : 30.00
Maximum Elevation of Bioretention Soil : 101.00
Native Soil Hydraulic Conductivity (in/hr) : 0.70
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 172.429
_____________________________________
Total: 172.429
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Basin 6 4.607
Link: iMPERVIOUS BIO 37.957
_____________________________________
Total: 42.564
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 1.091 ac-ft/year, Post Developed: 0.269 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: iMPERVIOUS BIO **********
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 40.45
Inflow Volume Including PPT-Evap (ac-ft): 41.68
Total Runoff Infiltrated (ac-ft): 37.96, 91.08%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 3.68
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 91.08%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: iMPERVIOUS BIO
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 2.131E-02 2-Year 2.210E-02
5-Year 3.473E-02 5-Year 3.293E-02
10-Year 4.680E-02 10-Year 3.756E-02
25-Year 5.933E-02 25-Year 4.822E-02
50-Year 7.572E-02 50-Year 5.876E-02
100-Year 8.205E-02 100-Year 7.242E-02
200-Year 0.128 200-Year 7.814E-02
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -95.9% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -95.0% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.43
Program License Number: 200410007
Project Simulation Performed on: 07/04/2018 2:27 PM
Report Generation Date: 07/04/2018 2:27 PM
—————————————————————————————————
Input File Name: Basin 1.fld
Project Name: Solera
Analysis Title: BMP Performance Standard
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Climatic Region Number: 0
Full Period of Record Available used for Routing
Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 961040 Puget East 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 1.000 0.109
Area of Links that Include Precip/Evap (acres) 0.000 0.004
Total (acres) 1.000 0.113
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
Till Forest 1.000
----------------------------------------------
Subbasin Total 1.000
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Basin 7 ----------
-------Area (Acres) --------
Till Grass 0.014
Impervious 0.095
----------------------------------------------
Subbasin Total 0.109
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
BASIN 7
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: iMPERVIOUS BIO
Link Type: Bioretention Facility
Downstream Link: None
Base Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 19.0
Bottom Width (ft) : 9.0
Side Slopes (ft/ft) : L1= 0.00 L2= 0.00 W1= 0.00 W2= 0.00
Bottom Area (sq-ft) : 171.
Area at Riser Crest El (sq-ft) : 171.
(acres) : 0.004
Volume at Riser Crest (cu-ft): 162.
(ac-ft) : 0.004
Infiltration on Bottom only Selected
Soil Properties
Biosoil Thickness (ft) : 1.50
Biosoil Saturated Hydraulic Conductivity (in/hr) : 6.00
Biosoil Porosity (Percent) : 30.00
Maximum Elevation of Bioretention Soil : 101.00
Native Soil Hydraulic Conductivity (in/hr) : 0.70
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 172.429
_____________________________________
Total: 172.429
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Basin 7 1.711
Link: iMPERVIOUS BIO 43.292
_____________________________________
Total: 45.003
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 1.091 ac-ft/year, Post Developed: 0.285 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: iMPERVIOUS BIO **********
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 45.41
Inflow Volume Including PPT-Evap (ac-ft): 47.04
Total Runoff Infiltrated (ac-ft): 43.29, 92.02%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 3.70
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 92.02%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: iMPERVIOUS BIO
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 2.131E-02 2-Year 2.521E-02
5-Year 3.473E-02 5-Year 3.831E-02
10-Year 4.680E-02 10-Year 4.363E-02
25-Year 5.933E-02 25-Year 5.179E-02
50-Year 7.572E-02 50-Year 6.019E-02
100-Year 8.205E-02 100-Year 7.058E-02
200-Year 0.128 200-Year 7.770E-02
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -96.5% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -93.2% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.43
Program License Number: 200410007
Project Simulation Performed on: 07/04/2018 2:29 PM
Report Generation Date: 07/04/2018 2:29 PM
—————————————————————————————————
Input File Name: Basin 1.fld
Project Name: Solera
Analysis Title: BMP Performance Standard
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Climatic Region Number: 0
Full Period of Record Available used for Routing
Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 961040 Puget East 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 1.000 0.218
Area of Links that Include Precip/Evap (acres) 0.000 0.007
Total (acres) 1.000 0.225
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
Till Forest 1.000
----------------------------------------------
Subbasin Total 1.000
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Basin 8 ----------
-------Area (Acres) --------
Till Grass 0.032
Impervious 0.186
----------------------------------------------
Subbasin Total 0.218
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
BASIN 8
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: iMPERVIOUS BIO
Link Type: Bioretention Facility
Downstream Link: None
Base Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 25.0
Bottom Width (ft) : 13.0
Side Slopes (ft/ft) : L1= 0.00 L2= 0.00 W1= 0.00 W2= 0.00
Bottom Area (sq-ft) : 325.
Area at Riser Crest El (sq-ft) : 325.
(acres) : 0.007
Volume at Riser Crest (cu-ft): 309.
(ac-ft) : 0.007
Infiltration on Bottom only Selected
Soil Properties
Biosoil Thickness (ft) : 1.50
Biosoil Saturated Hydraulic Conductivity (in/hr) : 6.00
Biosoil Porosity (Percent) : 30.00
Maximum Elevation of Bioretention Soil : 101.00
Native Soil Hydraulic Conductivity (in/hr) : 0.70
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 172.429
_____________________________________
Total: 172.429
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Basin 8 3.911
Link: iMPERVIOUS BIO 84.886
_____________________________________
Total: 88.797
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 1.091 ac-ft/year, Post Developed: 0.562 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: iMPERVIOUS BIO **********
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 89.83
Inflow Volume Including PPT-Evap (ac-ft): 92.92
Total Runoff Infiltrated (ac-ft): 84.89, 91.35%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 7.92
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 91.35%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: iMPERVIOUS BIO
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 2.131E-02 2-Year 5.000E-02
5-Year 3.473E-02 5-Year 7.600E-02
10-Year 4.680E-02 10-Year 8.869E-02
25-Year 5.933E-02 25-Year 0.104
50-Year 7.572E-02 50-Year 0.120
100-Year 8.205E-02 100-Year 0.139
200-Year 0.128 200-Year 0.156
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -95.3% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -80.1% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.43
Program License Number: 200410007
Project Simulation Performed on: 07/04/2018 2:31 PM
Report Generation Date: 07/04/2018 2:31 PM
—————————————————————————————————
Input File Name: Basin 1.fld
Project Name: Solera
Analysis Title: BMP Performance Standard
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Climatic Region Number: 0
Full Period of Record Available used for Routing
Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 961040 Puget East 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 1.000 0.132
Area of Links that Include Precip/Evap (acres) 0.000 0.003
Total (acres) 1.000 0.135
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
Till Forest 1.000
----------------------------------------------
Subbasin Total 1.000
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Basin 9 ----------
-------Area (Acres) --------
Till Grass 0.055
Impervious 0.077
----------------------------------------------
Subbasin Total 0.132
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
BASIN 9
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: iMPERVIOUS BIO
Link Type: Bioretention Facility
Downstream Link: None
Base Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 25.0
Bottom Width (ft) : 6.0
Side Slopes (ft/ft) : L1= 0.00 L2= 0.00 W1= 0.00 W2= 0.00
Bottom Area (sq-ft) : 150.
Area at Riser Crest El (sq-ft) : 150.
(acres) : 0.003
Volume at Riser Crest (cu-ft): 143.
(ac-ft) : 0.003
Infiltration on Bottom only Selected
Soil Properties
Biosoil Thickness (ft) : 1.50
Biosoil Saturated Hydraulic Conductivity (in/hr) : 6.00
Biosoil Porosity (Percent) : 30.00
Maximum Elevation of Bioretention Soil : 101.00
Native Soil Hydraulic Conductivity (in/hr) : 0.70
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 172.429
_____________________________________
Total: 172.429
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Basin 9 6.722
Link: iMPERVIOUS BIO 43.061
_____________________________________
Total: 49.783
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 1.091 ac-ft/year, Post Developed: 0.315 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: iMPERVIOUS BIO **********
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 45.49
Inflow Volume Including PPT-Evap (ac-ft): 46.87
Total Runoff Infiltrated (ac-ft): 43.06, 91.87%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 3.78
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 91.87%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: iMPERVIOUS BIO
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 2.131E-02 2-Year 2.273E-02
5-Year 3.473E-02 5-Year 3.588E-02
10-Year 4.680E-02 10-Year 4.265E-02
25-Year 5.933E-02 25-Year 5.312E-02
50-Year 7.572E-02 50-Year 6.709E-02
100-Year 8.205E-02 100-Year 8.041E-02
200-Year 0.128 200-Year 8.373E-02
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -96.0% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -94.5% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.43
Program License Number: 200410007
Project Simulation Performed on: 07/04/2018 2:32 PM
Report Generation Date: 07/04/2018 2:32 PM
—————————————————————————————————
Input File Name: Basin 1.fld
Project Name: Solera
Analysis Title: BMP Performance Standard
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Climatic Region Number: 0
Full Period of Record Available used for Routing
Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 961040 Puget East 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 1.000 0.110
Area of Links that Include Precip/Evap (acres) 0.000 0.004
Total (acres) 1.000 0.114
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
Till Forest 1.000
----------------------------------------------
Subbasin Total 1.000
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Basin 10 ----------
-------Area (Acres) --------
Till Grass 0.014
Impervious 0.096
----------------------------------------------
Subbasin Total 0.110
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
BASIN 10
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: iMPERVIOUS BIO
Link Type: Bioretention Facility
Downstream Link: None
Base Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 100.50
Storage Depth (ft) : 0.50
Bottom Length (ft) : 20.0
Bottom Width (ft) : 9.0
Side Slopes (ft/ft) : L1= 0.00 L2= 0.00 W1= 0.00 W2= 0.00
Bottom Area (sq-ft) : 180.
Area at Riser Crest El (sq-ft) : 180.
(acres) : 0.004
Volume at Riser Crest (cu-ft): 171.
(ac-ft) : 0.004
Infiltration on Bottom only Selected
Soil Properties
Biosoil Thickness (ft) : 1.50
Biosoil Saturated Hydraulic Conductivity (in/hr) : 6.00
Biosoil Porosity (Percent) : 30.00
Maximum Elevation of Bioretention Soil : 101.00
Native Soil Hydraulic Conductivity (in/hr) : 0.70
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 6.00
Common Length (ft) : 0.000
Riser Crest Elevation : 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 172.429
_____________________________________
Total: 172.429
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Basin 10 1.711
Link: iMPERVIOUS BIO 44.165
_____________________________________
Total: 45.876
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 1.091 ac-ft/year, Post Developed: 0.290 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: iMPERVIOUS BIO **********
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 45.86
Inflow Volume Including PPT-Evap (ac-ft): 47.58
Total Runoff Infiltrated (ac-ft): 44.17, 92.82%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 3.39
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 92.82%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: iMPERVIOUS BIO
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 2.131E-02 2-Year 2.492E-02
5-Year 3.473E-02 5-Year 3.728E-02
10-Year 4.680E-02 10-Year 4.252E-02
25-Year 5.933E-02 25-Year 5.175E-02
50-Year 7.572E-02 50-Year 6.059E-02
100-Year 8.205E-02 100-Year 7.122E-02
200-Year 0.128 200-Year 7.853E-02
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%): -96.8% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -93.6% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------