HomeMy WebLinkAboutRS_Technical Information Report_220708_v2.
Maple Highlands
Preliminary Plat #LUA22-000112
Drainage Report
July 2022
Maple Highlands – Conner Homes
i
Drainage Report
July 2022
Prepared for:
Conner Homes
12600 SE 38th Street, Suite 250
Bellevue, WA 98006
Prepared by:
Jeremy Febus, PE, LEED AP
KPFF Consulting Engineers
1601 Fifth Avenue, Suite 1600
Seattle, WA 98101
(206) 622-5822
07/07/2022
KPFF Consulting Engineers
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Maple Highlands – Conner Homes
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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 ........................................................................ 2
Core Requirement No. 2: Offsite Analysis ..................................................................................................... 3
Core Requirement No. 3: Flow Control .......................................................................................................... 6
Core Requirement No. 4: Conveyance System ............................................................................................. 8
Core Requirement No. 5: Construction Stormwater Pollution prevention ..................................................... 8
Core Requirement No. 6: Maintenance and Operations ............................................................................... 8
Core Requirement No. 7: Financial Guarantees and Liability ....................................................................... 8
Core Requirement No. 8: Water Quality ........................................................................................................ 8
Core Requirement No. 9: On-Site BMPs ....................................................................................................... 9
Special Requirements ................................................................................................................................... 10
List of Figures
Figure 1-1: Vicinity Map, Courtesy of King County iMap...................................................................................... 1
Figure 2-1: Existing Drainage Basin and Downstream ........................................................................................ 2
Figure 3-1: Predeveloped Areas .......................................................................................................................... 6
Figure 3-2: Developed Areas ............................................................................................................................... 7
List of Tables
Table 3-1: Downstream Drainage Compliant Summary........................................................................................ 4
Table 3-2: On-Site Area Summary ....................................................................................................................... 7
Table 3-3: MGSFlood Peak Flow Rate with 15-Minute Time Step ...................................................................... 7
Table 3-4: Water Quality Pond Information .......................................................................................................... 9
Appendices
Appendix A – TIR Worksheet
Appendix B – Existing and Proposed Conditions Map
Appendix C – Downstream Analysis
Appendix D – Peak Flow Control Application Map and MGS Flood Calculations
Appendix E – On-Site BMPs Credits and Calculations
Appendix F – Pipe Conveyance
Appendix G – Erosion Control Plan and Details (To Be Provided With Future Submittal)
Appendix H – SWPPP
Appendix I – Bond Quantity Worksheet (To Be Provided With Future Submittal)
Appendix J – Operation and Maintenance Manual
Appendix K – Geotechnical Report
Maple Highlands – Conner Homes
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1. Project Overview
Maple Highlands is a 4.16-acre proposed residential development with 0.45-acres of right-of-way
improvements located at 13818 152nd Ave SE and 13929 154th Ave SE in Renton, Washington (see Figure 1-
1). The project consists of two existing parcels which will be subdivided into 13 parcels, including a storm tract
and dedication for public right-of-way. This report has been prepared in support of the preliminary plat
application. The project site includes construction of 12 single-family homes, construction of SE 5th Place and
153rd Ave SE onsite, associated frontage improvements, grading, utilities, and stormwater mitigation facilities.
The proposed project is subject to the requirements of the 2017 City of Renton Surface Water Manual
(RSWM) as adopted with amendments to the 2016 King County Surface Water Design Manual.
Figure 1-1: Vicinity Map, Courtesy of King County iMap
2. Existing Conditions and Drainage
The site is currently occupied by two single-family homes and consists of a single basin. The existing site
slopes generally southwest at gradual slopes and runoff sheet flows onto the neighboring property in the
existing condition. The project site and neighboring soils are mapped as Alderwood gravelly sandy loam (AgC)
according to the USDA Web Soil Survey.
Downstream of the site, stormwater is conveyed to a tightlined City of Renton system before entering a series
of drainage ditches owned by King County. Runoff continues to be conveyed by King County roadside ditches
0.25 miles downstream of the site and ultimately discharges to the Cedar River approximately 1.0 miles
downstream. See Figure 2-1 for the downstream flow path. See Appendix C for additional downstream
analysis information.
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Figure 2-1: Existing Drainage Basin and Downstream
3. Proposed Conditions and Requirements Summary
The proposed development requires a “Full Drainage Review” per the RSWM. The development must comply
with all nine core requirements and six special requirements.
CORE REQUIREMENT NO. 1: DISCHARGE AT THE NATURAL L OCATION
The development will modify the pre-existing topography and drainage patterns of the site to divert water from
entering the neighboring property to the southwest and instead capture and convey runoff to the municipal
system to the southeast. Onsite, runoff will be captured by a series of catch basins in the public right-of-way
and conveyed to a combination wetpool-detention pond before discharge from the project site.
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CORE REQUIREMENT NO. 2: OFFSITE ANALYSIS
A Level 1 downstream analysis was completed January 19th, 2022 as part of compliance with Core
Requirement 2. As outlined in RSWM Section 1.2.2.1, the Tasks 1-4 below were completed as part of the
offsite analysis.
Per City review comments dated May 6th, 2022, an additional Level 2 Downstream Analysis was completed on
May 20th, 2022 to address informal drainage complaints indicating a Type 3 – Severe Flooding Problem.
Information from the more in-depth analysis has been added to the appropriate tasks below. Calculations of
the existing downstream system can be found in Appendix C.
Task 1: Define and map the study area
The proposed project site is located at 13818 152nd Ave SE and 13929 154th Ave SE in Renton, Washington.
Both properties are currently developed with detached single-family homes and associated driveways and
various outbuildings. The existing ground cover is mostly grass and trees of varying age and health. The
existing site topography generally ranges from 0% to 10%. See Figure 1-1 for an aerial of existing site
conditions.
Task 2: Review all available information on the study area
King County iMap and the City of Renton (COR) Maps and GIS Data were reviewed to identify any potential
sensitive areas in the proximity of the project site. See Figure 2-1 for existing drainage basin and downstream.
Wetlands: iMap does not identify any wetlands on the project site.
Streams and 100-year Floodplain: The project site is not located in the 100-year floodplain.
Erosion Hazard Areas: COR Maps identifies no erosion hazard areas on the project site.
Seismic Hazard Areas: COR Maps identifies no seismic hazard areas on the project site.
Coal Mine Hazard Areas: COR Maps identifies no coal mine hazard areas on the project site.
Critical Aquifer Recharge Area: iMap does not identify the project within a critical aquifer recharge area.
Basin Condition: iMap does not indicate any basin conditions.
Areas Susceptible to Groundwater Contamination: iMap does not show the project site as being susceptible to
groundwater contamination.
King County iMAP was also reviewed for downstream drainage complaints. A total of nine possible relevant
complaints were identified, all in Unincorporated King County. Table 3-1 summarizes the available compliant
information in downstream order. After review, none appear to be active issues under review by the County.
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Table 3-1: Downstream Drainage Compliant Summary
Compliant
Number
Compliant
Type
Date
Recie
ved
Problem Date
Closed
Address
Parcel
Comments
Tracker ID
2018-
0932 R DDM 12/26/
2018
14009 154th
Ave SE
14634
00022
CONCERN ABOUT
DRAINAGE FROM A
PLAT IN THE CITY OF
RENTON.
CONCERNS
ADDRESSED BY
RIGHT-OF-WAY USE
PERMIT ROWP18-
0004.
43330.00
2016-
0242 CUST WQAI 11/3/
2016
151XX SE
142nd St
10720
00450 40900.00
2011-
0968 CUST WQAI 12/18/
2012
151XX SE
142nd St
10720
00450 36732.00
2000-
0430 FCR DCA 6/14/
2000
14995 SE
142nd St
10720
00460
UTILITY PROJECT.
SPOILS AND
MATERIAL
STOCKPILED IN R/D
TRACT. DISCUSSED
WITH UTILITY
INSPECTOR.
CONTRACTOR TO
REMOVE MATERIAL
2346.00
2001-
0332 FCR MMG 5/28/
2001
14995 SE
142nd St
10720
00460
REQUEST TO
REPLACE POND ID
SIGN AND TO
INSTALL SCOOP
LAW AND LEASH
SIGN
25854.00
2004-
0388 FCR MNM 8/24/
2004
14202
149TH PL
SE
10720
00460
Trees and debris
dumped on D90669.
Investigator spoke to
neighbors about illegal
dumping. Debris
cleaned up on
subsequent site visit.
29291.00
2002-
0629 FCR DDM 10/1/
2002
14995 SE
142ndt St
10720
00460
DEBRIS PICKED UP.
FACILITY MOWED
ON 4/17/02
27416.00
1997-
1537 FCR FLOO
D-ING
1/13/
1998
SE 142
ST/149 PL
SE
10720
00460
RETRO FIT OF R/D
PONDS LDSU PROJ 23284.00
1997-
0498 C
KC
PROP
E
4/4/
1997
14202
149TH PL
SE
10720
00440
ALLEGED DOP
DEFECATION IN R/D
FACILITY
22109.00
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Task 3: Field inspect the study area
A field inspection was completed January 19th, 2022 on a cloudy day with a temperature of approximately 50
degrees. The onsite drainage basin has slopes ranging from 0% to 10%. The project site is comprised of a
single basin with surface runoff traveling primarily as sheet slow over pervious areas. The drainage basin is
comprised mostly of grass with two single-family homes, landscaped areas, associated driveways, and various
outbuildings. Based on visual inspection and survey contour data, the low point of the site is in the southwest
corner adjacent to the neighboring properties to the south and west. The proposed downstream system to the
southeast of the project site did not show evidence of erosion or washout.
As part of the city-requested Level 2 downstream analysis, an additional field inspection was performed on
May 20th, 2022 on a cloudy day with a temperature of approximately 50 degrees. To quantify the capacity of
the downstream system, measurements were taken of the existing downstream ditches with a hand tape and
hand level. City GIS was also used to check existing slopes.
Sections of the downstream channels were then grouped by approximate ditch dimensions. The shallowest
grade (0.5%) was determined to be the most conservative and was used throughout to estimate the ditch
capacity. The minimum ditch widths and depths found were also conservatively used for capacity calculations.
Pipes carrying ditches beneath driveways were assumed to be at 0.5%.
As the proposed development will reduce the runoff generated during the 100-year storm event (see Appendix
D for calculations); and as the existing downstream system is able to pass the 100-year storm event from the
proposed development through its smallest section; and as no additional evidence of erosion or washout were
found, no additional analysis is proposed. See Appendix C for additional downstream measurements and
calculations.
Task 4: Describe the drainage system, and its existing and predicted drainage and water quality
problems.
Existing downstream
After leaving the project site, runoff continues to sheet flow to the south through private property until it
reaches the roadside conveyance system in SE 142nd St. From there, it is conveyed by roadside ditch to an
unnamed Cedar River tributary before discharging to Cedar River approximately 1-mile downstream.
Proposed downstream
The development will modify the pre-existing topography and drainage patterns to divert water from entering
the neighboring property to the southwest and instead capture and convey runoff to the municipal system to
the southeast. Onsite, runoff will be captured by a series of catch basins in the public right-of-way and
conveyed to a combination wetpool-detention pond before discharge from the project site.
Downstream of the municipal system in SE 154th St, runoff will be conveyed south along existing roadside
ditches on 154th Ave SE to the intersection of 154th Ave SE and SE 142nd St. Once runoff enters the roadside
ditch system on SE 142nd St, it rejoins the existing downstream drainage path before entering the unnamed
tributary to Cedar River. The existing and proposed downstream routes join within ¼ mile downstream of the
project site.
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CORE REQUIREMENT NO. 3: FLOW CONTROL
According to the Flow Control Application Map in the RSWM (see Appendix D), the project site is required to
meet the Flow Control Duration Standard Matching Forested Conditions. Flows from the development must
match the flow duration of pre-developed rates forested (historical, pre-developed) conditions over the range
of flows extending from 50% of the 2-year up to the full 50-year flow and match peaks for the 2-year and 10-
year return periods.
Per City comments dated May 6th, 2022, due to informal downstream drainage complaints, the project must
additionally meet Flood Problem Flow Control standard, matching forested site conditions for the 2-year
through the 100-year return frequencies.
Flow control requirements will be met using a combination wetpool-detention pond in the southeast corner of
the site. See Figures 3-1 and 3-2 and Table 3-2 and Table 3-3 for site areas and peak flow information.
Figure 3-1: Predeveloped Areas
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Figure 3-2: Developed Areas
Table 3-2: Disturbed Area Summary (On-site + Off-site)
Impervious (Acres) Pervious (Acres) Total (Acres)
Predeveloped Conditions 0.00 4.61 4.61
Developed Conditions 2.15 2.46 4.61
Table 3-3: MGSFlood Peak Flow Rate with 15-Minute Time Step
Predeveloped Peak
Flows (cfs)
Developed Peak Flows
(cfs)
2-Year Peak Flow 0.116 0.053
10-Year Peak Flow 0.228 0.081
25-Year Peak Flow 0.313 0.170
100-Year Peak Flow 0.373 0.207
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CORE REQUIREMENT NO. 4: CONVEYANCE SYSTEM
The proposed conveyance system has been designed to convey the 25-year peak flow without overtopping
any pipe system structure. The proposed 12-inch pipe at 0.5 percent has a capacity of 2.73 cfs, which is more
than the undetained 25-year developed peak flow of 2.30 cfs. See Appendix F for additional peak flow
calculations to compare storm pipe capacity.
CORE REQUIREMENT NO. 5: CONSTRUCTION STORMWATER PO LLUTION
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. Additionally, coverage under the Washington State Department of Ecology’s Construction
Stormwater General Permit will be obtained prior to civil construction permit.
TESC BMPs are anticipated to include silt fences, conveyance channels, check dams, sediment ponds, and
catch basin inserts. Additional TESC plans will be provided with a future submittal.
CORE REQUIREMENT NO. 6: MAINTENANCE AND OPERATIONS
The owner has maintenance responsibilities for on-site facilities, and the City of Renton has maintenance
responsibilities for stormwater facilities that are located within the public right-of-way of 152nd Ave SE and 154th
Ave SE. See Appendix J for a copy of the Maintenance and Operations Manual.
CORE REQUIREMENT NO. 7: FINANCIAL GUARANTEES AND L IABILITY
Bond quantities for site improvements will be provided with a future submittal.
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. As this project does not propose a specialty land use, per Section 6.1.1 of the
RSWM, Basic Water Quality treatment is required. This project proposes to primarily use a combination
wetpool-detention pond to meet water quality requirements.
Water Quality Pond
Basic water quality treatment is achieved by providing a basic wetpond volume equal to 91% water quality
treatment volume calculated using an approved hydraulic model. The water quality pond was designed per
Section 6.4.1.2 of the RSWM.
The pond has 3H:1V side slopes and is divided into two cells separated by a berm with 2:1 side slopes. The
top of the berm is one foot below the water quality design water surface. The first cell includes 1 foot of
sediment storage and contains approximately 35% of the total water quality volume. The inlet to the pond is
submerged with the invert 2 feet from the pond bottom. The outlet pipe extends 1 foot below the water quality
water surface and leads to an outlet structure with a birdcage lid. See Appendix D for required volume
calculations and full MGS Hydraulic Model results. See Table 3-4 for additional wetpool water quality
information.
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Table 3-4: Water Quality Pond Information
Dead Storage
Volume Required 12,526 cf
Volume Provided 33,761 cf
Cell 1 Depth 4.67 ft
Cell 2 Depth 4.67 ft
Bottom of Pond Elevation 374.08
WQ Elevation 378.75
CORE REQUIREMENT NO. 9: ON-SITE BMPS
The project is required to meet the On-site BMP requirements by targeting 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.
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; or,
2) Using a continuous runoff model to demonstrate compliance with the Low Impact Development (LID)
Performance Standard.
This development has opted to incorporate on-site BMPs to the maximum extent feasible per the RSWM.
The feasibility and applicability of full dispersion must be evaluated for all target impervious surfaces. Full
dispersion has been determined to be unfeasible due to limited undisturbed native vegetation, insufficient flow
paths, and poor soil infiltration characteristics. Additionally, future build-out in the development will likely
reduce the 25-foot minimum required dispersion pathway.
All target impervious surfaces not mitigated by full dispersion or full infiltration must be mitigated to the
maximum extent feasible using one or more BMPs from the following: limited infiltration, rain gardens,
bioretention, and permeable pavement. Each of the above has been determined to be unfeasible due to poor
soil infiltration characteristics.
On-site infiltration testing was performed by the Geotechnical Engineer in accordance with the RSWM and is
discussed in the geotechnical report prepared by GeoEngineers. See Appendix K for additional details.
All target impervious surfaces not mitigated by an aforementioned BMP must be mitigated to the maximum
extent feasible using the Basic Dispersion BMP. Basic dispersion has been determined to be unfeasible due to
limited vegetated flow paths.
The roof drain perforated pipe connection detailed in Section C2.11 of the RSWM is not feasible due to poor
soil conditions that would cause flooding problems.
BMPs must be implemented, at minimum, for an impervious area equal to at least 10% of the lot for lot sizes
up to 11,000 square feet and at least 20% of the lot for lot sizes between 11,000 and 22,000 square feet. If
these minimum areas are not mitigated using feasible BMPs from above, one or more BMPs from the following
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list are required to be implemented to achieve compliance: Reduced Impervious Surface Credit, Native Growth
Retention Credit, and Tree Retention Credit.
The reduced impervious surface credit using the restricted footprint technique was evaluated for the 12
residential lots. For lots smaller than 22,000 square feet, any recorded limit on total impervious surface less
than a norm of 4,000 square feet or the maximum allowed by the lot’s zoning, whichever is smaller, qualifies
for a restricted footprint credit equal to the difference in square footage. Lots 5, 7, and 8 can limit the
impervious surface credit, however the benefit is insignificant when account for future development (i.e. patios,
decks, etc.) and would provide greater than 4,000 square feet. Lots 1 through 4, 6, and 9 through 12 do not
receive the credit because the impervious areas from the lots are greater than 4,000 square feet. See
Appendix E for OSM BMP credit check for the twelve lots.
The native growth and tree retention credit was also evaluated for Lot 7 because of the proposed tree tract
along the northern extents. The total canopy coverage, per the Landscape Architects, is approximately 2,370
square feet. The sizing factor requires the credit to be 20% of the canopy area, which equates to 474 square
feet of mitigated area. Note flow control calculations under Core Requirement 3 excluded this credit to be
conservative.
Soil amendment will be implemented to the maximum extent feasible for all landscaped surfaces.
SPECIAL REQUIREMENT NO. 1: OTHER ADOPTED AREA-SPEC IFIC
REQUIREMENTS
This project is not subject to any other known area-specific requirements.
SPECIAL REQUIREMENT NO. 2: FLOOD HAZARD AREA DELIN EATION
This project is not located in a flood hazard area.
SPECIAL REQUIREMENT NO. 3: FLOOD PROTECTION FACILI TIES
This project does not modify or use a flood protection facility.
SPECIAL REQUIREMENT NO. 4: SOURCE CONTROL
Source control requirements apply to projects proposing commercial buildings or site development, which this
project does not.
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 AREA S
Under current delineations of aquifer protection areas within the city, the project site is not located within any
aquifer protection area or wellhead protection zone.
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Maple Highlands – Conner Homes
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
__________________
__________________
__________________
Maple Highlands
tbd
23N
Aron Golden, Agent for the Conner
Homes Group, LLC
12600 SE 38th St, Suite 250
Tim Prusa
KPFF Consulting Engineers
(206) 926-0586
1-888-302-1252
Bellevue, WA 98006 05E
9
13929 154th Ave SE &
13818 152nd Ave SE Renton, WA 98059
X
X
03/18/2022
X
03/18/2022
07/08/2022
07/08/2022
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 ______________________
_____________________________________
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: _________________________
Alderwood gravelly sandy loam (AgC)8-15%Low
One onsite drainage basin
1
05/20/2022
Soil Amendment
TBD
X Infiltration infeasible, see Geotech report
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:
None
None
Provided at civil construction
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
X
X
X
X
N/a
X Wetpool-Detention Pond
Wetpool-Detention PondX
X
X Soil Amendment
Soil Amendment
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
Maple Highlands – Conner Homes
Appendix B
Appendix B
Existing and Proposed Conditions Map
Total disturbed (forested):
200,770 sf (4.61 ac)
3
BPE 386.4
376376376390
384
386
388
392
394388
38
6
386386386 3863863863
8
6 3861
BPE 388.4
2
BPE 387.4
4
BPE 385.0
12
BPE 386.0
11
BPE 386.1
5
BPE 385.4
6
BPE 386.1
7
BPE 386.4
10
BPE 387.0
9
BPE 386.6
8
BPE 386.3
SE 138TH PL
152ND AVE SE153RD AVE SESE 5TH PL
SE 5TH PL
154TH AVE SEROCKERY
ROCKERY
CIP RETAINING WALL
CB #12
RIM=385.50
12" CPEP IE OUT=382.32 (SE)
CB #11
RIM=385.81
12" DI IE IN=382.18 (NW)
12" DI IE OUT=382.18 (E)CB #5
RIM=384.51
12" DI IE OUT=381.15 (N)
CB#4
RIM=384.32
12" DI IE IN=381.01 (S, W)
12" DI IE OUT=381.01 (E)
CB #1
RIM=383.68
12" DI IE OUT=381.03 (W)CB #2
RIM=383.68
12" DI IE IN=380.91 (W)
12" DI IE OUT=380.91 (SE)
CB #3
RIM=384.53
12" DI IE IN=380.73 (NW)
12" DI IE IN=380.73 (W)
12" DI IE OUT=380.73 (E)
CB #6
RIM=385.28
12" CPEP IE IN=380.55 (W)
12" CPEP IE IN=380.55 (S)
12" CPEP IE OUT=380.55 (E)
CB #7
RIM=385.31
12" CPEP IE OUT=380.79 (N)
CB #8
RIM=386.82
12" CPEP IE IN=379.30 (W)
12" CPEP IE OUT=379.30 (S)
CB #9
RIM=390.91
12" DI IE OUT=388.16 (E)
CB #10
RIM=390.98
12" DI IE IN=388.03 (W)
EX 18" CPEP IE IN =387.47 (N)
EX 18" CPEP IE OUT =387.47 (S)
CONTROL STRUCTURE
RIM=385.25
12" CPEP IE OUT=378.75 (E)
CB #16
RIM=382.64
12" CPEP IE IN=378.52 (W)
12" CPEP IE OUT=378.52 (E)
27 LF 12" CPEP @ 0.5%
28 LF 12" DI @ 0.5%48 LF 12" DI
@ 0.5%
22 LF 8" DI @ 0.5%
40 LF 12" DI @ 0.5%
36 LF 12"
CPEP @ 0.5%
20 LF 12"
CPEP @ 1.0%
150 LF 12"
CPEP @ 1.5%
47 LF 12"
CPEP @ 1.5%
15 LF 12" CPEP @ 0.7%
26 LF 12" CPEP
@ 0.7%
27 LF 12" DI @ 0.5%TW 385.70BW 381.67TW 385.73BW 379.53TW 385.75BW 377.34T
W
3
8
5
.
7
5
B
W
3
7
9
.
5
2
TW
3
8
5
.
4
5
BW
3
8
1
.
0
0
T
W
3
8
5
.
4
5
B
W
3
8
5
.
0
0
TW
3
8
5
.
4
5
BW
3
7
4
.
0
8TW 385.45BW 374.08T
W
3
8
8
.
5
5
B
W
3
8
8
.
5
5
TW
3
9
1
.
2
5
BW
3
8
9
.
0
1
TW
3
9
3
.
6
3
BW
3
8
9
.
0
0 TW 396.00BW 390.00TW 387.16BW 387.16386TOP OF POND 385.45
BOT OF POND 374.08
INTERIOR SLOPES 3:1
EX CB
RIM=382.40
12" CPEP IE IN=378.34 (W)
EX 4" PVC IE IN=378.99 (NE)
EX 18" CPEP IE IN=378.38 (N)
EX 18" CPEP IE OUT=378.34 (S)
TREE TRACT BOUNDARY
24 LF 12"
CPEP @ 1.5%
CB #14
RIM=386.85
12" CPEP IE IN=378.94
12" CPEP IE OUT=378.94 380
376378382
384
386
TW 388.49BW 374.08CB #15
RIM=382.89
12" CPEP IE IN=378.67 (W)
12" CPEP IE OUT=378.67 (E)
15 LF 12" CPEP @ 0.7%
232 LF 12" DI @ 0.5%
NW 1/4 OF THE NW 1/4 AND THE NE 1/4 OF THE NW 1/4 SECTION 9, TOWNSHIP 23 NORTH, RANGE 05 EAST, W.M.
1601 5th Avenue, Suite 1600
Seattle, WA 98101
206.622.5822
www.kpff.com
R
Call 811two business daysbefore you dig
CITY OF
RENTON
IN COMPLIANCE WITH CITY OF RENTON STANDARDS
MAPLE HIGHLANDS
13818 152ND AVE SE
RENTON, WA 98059TED-XX-XXXX07/08/2022
11MAPLE HIGHLANDSLUA22-XXXXXXC22-XXXXXXPR22-XXXXXXC4.0DRAINAGE CONTROL PLAN
5
0
1 INCH = 40 FEET
20'40'80'
APPROXIMATE EARTHWORK QUANTITIES
APPROXIMATE EARTHWORK QUANTITIES WERE ESTIMATED USING A GRID
VOLUME METHOD AND AUTOCAD CIVIL 3D SOFTWARE. THE FOLLOWING
VALUES ARE ESTIMATE PROVIDED TO ILLUSTRATE GENERAL EARTHWORK
EFFORTS BASED ON AVAILABLE EXISTING TOPOGRAPHIC SURVEY AND
FINISHED GRADE DESIGN DATA, AND DOES NOT INCLUDE ESTIMATED
EARTHWORK VOLUMES THAT WOULD BE DISPLACED OR OTHERWISE
OCCUPIED BY STRUCTURE, FOUNDATION, AND PAVEMENT SECTIONS OR
TRENCH BACKFILL:
FILL: 12000 CY
CUT: 2000 CY
NET: 10000 CY (FILL)
THE CONTRACTOR SHALL USE THEIR OWN MEANS AND METHOD TO
ESTIMATE EARTHWORK QUANTITIES.
LEGEND
PROPERTY LINE
ROW LINE
ROAD CENTERLINE
LOT LINE
EASEMENT
WATER LINE
SANITARY SEWER LINE
STORM DRAIN LINE
WATER METER
GATE VALVE
FIRE HYDRANT
WATER BEND WITH THRUST
BLOCKING
CATCH BASIN (TYPE 1)
CATCH BASIN (TYPE 2)
SANITARY SEWER MANHOLE
FLOW DIRECTION
CLEANOUT
AREAS TO POND
WATER QUALITY AND
DETENTION POND
Maple Highlands – Conner Homes
Appendix C
Appendix C
Downstream Analysis
SECTION 2.3 DRAINAGE REVIEW PLAN SPECIFICATIONS
12/12/2016 2017 City of Renton Surface Water Design Manual
2-12
TIR SECTION 3
OFFSITE ANALYSIS
All projects in engineering review shall complete, at a minimum, an Offsite Analysis, except for projects
meeting the exemptions outlined in Section 1.2.2. The Offsite Analysis is usually completed as part of the
initial permit application and review process, and is to be included in the TIR. Note: If offsite conditions
have been altered since the initial submittal, a new offsite analysis may be required.
The primary component of the offsite analysis is the downstream analysis described in detail below.
Upstream areas are included in this component to the extent they are expected to be affected by backwater
effects from the proposed project. Other components of the offsite analysis could include, but are not
limited to, evaluation of impacts to fish habitat, groundwater levels, groundwater quality, or other
environmental features expected to be significantly impacted by the proposed project due to its size or
proximity to such features.
Levels of Analysis
The offsite analysis report requirements vary depending on the specific site and downstream conditions.
Each project submittal shall include at least a Level 1 downstream analysis. Upon review of the Level 1
analysis, CED may require a Level 2 or Level 3 analysis. If conditions warrant, additional, more detailed
analysis may be required. Note: Potential impacts upstream of the proposal shall also be evaluated.
Level 1 Analysis
The Level 1 analysis is a qualitative survey of each downstream system leaving a site. This analysis is
required for all proposed projects and shall be submitted with the initial permit application. Depending
on the findings of the Level 1 analysis, a Level 2 or 3 analysis may need to be completed or additional
information may be required. If further analysis is required, the applicant may schedule a meeting with
CED staff.
Level 2 or 3 Analysis
If drainage problems are identified in the Level 1 analysis, a Level 2 (rough quantitative) analysis or a
Level 3 (more precise quantitative) analysis may be required to further evaluate proposed mitigation
for the problem. CED staff will determine whether a Level 2 or 3 analysis is required based on the
evidence of existing or potential drainage problems identified in the Level 1 analysis and on the
proposed design of onsite drainage facilities. The Level 3 analysis is required when results need to be
as accurate as possible: for example, if the site is flat; if the system is affected by downstream
controls; if minor changes in the drainage system could flood roads or buildings; or if the proposed
project will contribute more than 15 percent of the total peak flow to the drainage problem location.
The Level 2 or 3 analysis may not be required if CED determines from the Level 1 analysis that
adequate mitigation will be provided.
Additional Analysis
Additional, more detailed hydrologic analysis may be required if CED determines that the
downstream analysis has not been sufficient to accurately determine the impacts of a proposed project
on an existing or potential drainage problem. This more detailed analysis may include a point of
compliance analysis as detailed in Section 3.3.6.
Scope of Analysis
Regardless of the level of downstream analysis required, the applicant shall define and map the study area
(Task 1), review resources (Task 2), inspect the study area (Task 3), describe the drainage system and
problems (Task 4), and propose mitigation measures (Task 5) as described below.
Task 1. Study Area Definition and Maps
For the purposes of Task 2 below, the study area shall extend downstream one mile (minimum
flowpath distance) from the proposed project discharge location and shall extend upstream as
necessary to encompass the offsite drainage area tributary to the proposed project site. For the
2.3.1 ENGINEERING PLAN SPECIFICATIONS
2017 City of Renton Surface Water Design Manual 12/12/2016
2-13
purposes of Tasks 3, 4, and 5, the study area shall extend downstream to a point on the drainage
system where the proposed project site constitutes less than 15 percent of the total tributary drainage
area, but not less than one-quarter mile (minimum flowpath distance). The study area shall also extend
upstream of the project site a distance sufficient to preclude any backwater effects from the proposed
project.
The offsite analysis shall include a site map showing property lines, and the best available
topographical map (e.g., from CED and Renton topographic map) with the study area boundaries,
site boundaries, downstream flowpath for a distance of one mile, and potential/existing problems
(Task 4) shown. Other maps, diagrams, photographs and aerial photos may be helpful in describing
the study area.
Task 2. Resource Review
To assist the design engineer in preparing an offsite analysis, Renton has gathered information
regarding existing and potential flooding, erosion, and water quality problems. For all levels of
analysis, all of the resources described below shall be reviewed for existing/potential problems in the
study area (upstream and one mile downstream of the project site):
• Adopted basin plans available at King County DPER, King County DNRP, and CED. For areas
where there is no adopted basin plan, Basin Reconnaissance Summary Reports may be useful.
• Floodplain/floodway (FEMA) maps available at CED and the library.
• Other offsite analysis reports in the same subbasin, if available (check with CED staff).
• Sensitive Areas Folio available at King County DPER, King County DNRP, and the library (see
also the City’s website: <http://rentonwa.gov/government/default.aspx?id=29885>) must be used
to document the distance downstream from the proposed project to the nearest critical areas.
• 2U.S. Department of Agriculture, King County Soils Survey available at King County DPER and
the library.
• Wetlands Inventory maps available at CED.
• Washington State Department of Ecology’s latest published Clean Water Act Section 303d list of
polluted waters posted at the following website:
<http://www.ecy.wa.gov/programs/wq/303d/currentassessmt.html>.
• City of Renton Erosion Maps and Landslide Maps.
Potential/existing problems identified in the above documents shall be documented in the Drainage
System Table (see Reference Section 8-B) as well as described in the text of the Level 1
Downstream Analysis Report. If a document is not available for the site, note in the report that the
information was not available as of a particular date. If necessary, additional resources are available
from King County, the Washington State Department of Fisheries and Wildlife (WDFW), the State
Department of Ecology (Ecology), the United States Army Corps of Engineers (Corps), and the public
works departments of other municipalities in the vicinity of the proposed project site.
Task 3. Field Inspection
The design engineer shall physically inspect the existing on- and offsite drainage systems of the study
area for each discharge location. Specifically, he/she shall investigate any evidence of the following
existing or potential problems and drainage features:
Level 1 Inspection:
1. Investigate any problems reported or observed during the resource review.
2. Locate all existing/potential constrictions or lack of capacity in the existing drainage system.
3. Identify all existing/potential downstream drainage problems as defined in Section 1.2.2.1.
4. Identify existing/potential overtopping, scouring, bank sloughing, or sedimentation.
2 Footnote 2 is not used.
SECTION 2.3 DRAINAGE REVIEW PLAN SPECIFICATIONS
12/12/2016 2017 City of Renton Surface Water Design Manual
2-14
5. Identify significant destruction of aquatic habitat or organisms (e.g., severe siltation, bank
erosion, or incision in a stream).
6. Collect qualitative data on features such as land use, impervious surfaces, topography, and
soil types.
7. Collect information on pipe sizes, channel characteristics, drainage structures, and relevant
critical areas (e.g., wetlands, streams, steep slopes).
8. Verify tributary basins delineated in Task 1.
9. Contact neighboring property owners or residents in the area about past or existing drainage
problems, and describe these in the report (optional).
10. Note the date and weather conditions at the time of the inspection.
Level 2 or 3 Inspection:
1. Perform a Level 1 Inspection.
2. Document existing site conditions (approved drainage systems or pre-1979 aerial
photographs) as defined in Core Requirement #3.
3. Collect quantitative field data. For Level 2, conduct rough field survey using hand tape, hand
level, and rod; for Level 3, collect field survey profile and cross-section topographic data
prepared by an experienced surveyor.
Task 4. Drainage System Description and Problem Descriptions
Each drainage system component and problem shall be addressed in the offsite analysis report in three
places: on a map (Task 1), in the narrative (Task 4), and in the Offsite Analysis Drainage System Table
(see Reference Section 8-B).
Drainage System Descriptions: The following information about drainage system components such
as pipes, culverts, bridges, outfalls, ponds, tanks, and vaults shall be included in the report:
1. Location (corresponding map label and distance downstream/upstream from site discharge)
2. Physical description (type, size, length, slope, vegetation, and land cover)
3. Problems including copies of any relevant drainage complaints
4. Field observations.
Problem Descriptions: All existing or potential drainage and water quality problems (e.g., ponding
water, high/low flows, siltation, erosion, listed water bodies, etc.) identified in the resource review or
field inspection shall be described in the offsite analysis. These descriptions will help in determining if
such problems require special attention per Core Requirement #2 (see Section 1.2.2.1) because they
are one of three defined drainage problem types or one of seven defined water quality problem types.
Special attention may include more analysis, additional flow control, or other onsite or offsite
mitigation measures as specified by the problem-specific mitigation requirements set forth in
Sections 1.2.2.2 and 1.2.2.3.
The following information shall be provided for each existing or potential drainage problem:
1. Description of the problem (ponding water, high or low flows, siltation, erosion, slides, etc.).
2. Magnitude of or damage caused by the drainage problem (siltation of ponds, dried-up ornamental
ponds, road inundation, flooded property, flooded building, flooded septic system, significant
destruction of aquatic habitat or organisms).
3. General frequency and duration of drainage problem (dates and times the problem occurred, if
available).
Downstream Bottom Width Top Width Channel Depth Slope
Section A 24"60"24"0.50%
(max measured)41"96"30"1.10%
Section B 24"36"12"0.50%
(max measured)27"42"26"1.40%
Section C 24"46"7"0.50%
(max measured)26"49"8"0.50%
Section D 12"60"24"0.50%
(max measured)38"84"30"0.90%
EASTERN DOWSTREAM SUMMARY OF VALUES (HAND MEASURED)
Downstream Bottom Width Top Width Channel Depth Slope
Section A 24"60"24"0.50%
(max measured)41"96"30"1.10%
Section B 24"36"12"0.50%
(max measured)27"42"26"1.40%
Section C 24"46"7"0.50%
(max measured)26"49"8"0.50%
Section D 12"60"24"0.50%
(max measured)38"84"30"0.90%
EASTERN DOWSTREAM SUMMARY OF VALUES (HAND MEASURED)
Cedar River
0.25 mile
downstream
1.0 mile
downstream
Site
discharge
Project Site
SD
22 LF 12"
SD @ 0.5%
18" Outfall
Section A
Section B
Section B
20 LF 12"
SD @ 0.5%
28 LF 12"
SD @ 0.5%
Section C
SDSD
Section D
50 LF 18"
SD @ 0.5%
26 LF 12"
SD @ 0.5%
Section B
Section B
30 LF 12"
SD @ 0.5%
SD
18 LF 12"
SD @ 0.5%
27 LF 12"
SD @ 0.5%
Worksheet for 12-Inch Pipe
Project Description
Manning
FormulaFriction Method
Full Flow
CapacitySolve For
Input Data
0.012Roughness Coefficient
ft/ft0.005Channel Slope
in12.0Normal Depth
in12.0Diameter
cfs2.73Discharge
Results
cfs2.73Discharge
in12.0Normal Depth
ft²0.8Flow Area
ft3.1Wetted Perimeter
in3.0Hydraulic Radius
ft0.00Top Width
in8.5Critical Depth
%100.0Percent Full
ft/ft0.007Critical Slope
ft/s3.47Velocity
ft0.19Velocity Head
ft1.19Specific Energy
(N/A)Froude Number
cfs2.94Maximum Discharge
cfs2.73Discharge Full
ft/ft0.005Slope Full
UndefinedFlow Type
GVF Input Data
in0.0Downstream Depth
ft0.0Length
0Number Of Steps
GVF Output Data
in0.0Upstream Depth
N/AProfile Description
ft0.00Profile Headloss
%0.0Average End Depth Over Rise
%0.0Normal Depth Over Rise
ft/s0.00Downstream Velocity
ft/s0.00Upstream Velocity
in12.0Normal Depth
in8.5Critical Depth
ft/ft0.005Channel Slope
ft/ft0.007Critical Slope
Page 1 of 127 Siemon Company Drive Suite 200 W
Watertown, CT 06795 USA +1-203-755-1666
6/20/2022
FlowMaster
[10.03.00.03]
Bentley Systems, Inc. Haestad Methods Solution
CenterChambers Downstream.fm8
Worksheet for 18-Inch Pipe
Project Description
Manning
FormulaFriction Method
Full Flow
CapacitySolve For
Input Data
0.012Roughness Coefficient
ft/ft0.005Channel Slope
in18.0Normal Depth
in18.0Diameter
cfs8.05Discharge
Results
cfs8.05Discharge
in18.0Normal Depth
ft²1.8Flow Area
ft4.7Wetted Perimeter
in4.5Hydraulic Radius
ft0.00Top Width
in13.2Critical Depth
%100.0Percent Full
ft/ft0.006Critical Slope
ft/s4.55Velocity
ft0.32Velocity Head
ft1.82Specific Energy
(N/A)Froude Number
cfs8.66Maximum Discharge
cfs8.05Discharge Full
ft/ft0.005Slope Full
UndefinedFlow Type
GVF Input Data
in0.0Downstream Depth
ft0.0Length
0Number Of Steps
GVF Output Data
in0.0Upstream Depth
N/AProfile Description
ft0.00Profile Headloss
%0.0Average End Depth Over Rise
%0.0Normal Depth Over Rise
ft/s0.00Downstream Velocity
ft/s0.00Upstream Velocity
in18.0Normal Depth
in13.2Critical Depth
ft/ft0.005Channel Slope
ft/ft0.006Critical Slope
Page 1 of 127 Siemon Company Drive Suite 200 W
Watertown, CT 06795 USA +1-203-755-1666
6/20/2022
FlowMaster
[10.03.00.03]
Bentley Systems, Inc. Haestad Methods Solution
CenterChambers Downstream.fm8
Section A
24"60"
24"0.5%
Worksheet for Section A
Project Description
Manning
FormulaFriction Method
DischargeSolve For
Input Data
0.030Roughness Coefficient
ft/ft0.005Channel Slope
in24.0Normal Depth
H:V0.750Left Side Slope
H:V0.750Right Side Slope
ft2.00Bottom Width
Results
cfs24.52Discharge
ft²7.0Flow Area
ft7.0Wetted Perimeter
in12.0Hydraulic Radius
ft5.00Top Width
in16.7Critical Depth
ft/ft0.019Critical Slope
ft/s3.50Velocity
ft0.19Velocity Head
ft2.19Specific Energy
0.522Froude Number
SubcriticalFlow Type
GVF Input Data
in0.0Downstream Depth
ft0.0Length
0Number Of Steps
GVF Output Data
in0.0Upstream Depth
N/AProfile Description
ft0.00Profile Headloss
ft/s0.00Downstream Velocity
ft/s0.00Upstream Velocity
in24.0Normal Depth
in16.7Critical Depth
ft/ft0.005Channel Slope
ft/ft0.019Critical Slope
Page 1 of 127 Siemon Company Drive Suite 200 W
Watertown, CT 06795 USA +1-203-755-1666
6/16/2022
FlowMaster
[10.03.00.03]
Bentley Systems, Inc. Haestad Methods Solution
CenterChambers Downstream.fm8
Section B
12"36"
18"
0
.
5%
Worksheet for Section B
Project Description
Manning
FormulaFriction Method
DischargeSolve For
Input Data
0.045Roughness Coefficient
ft/ft0.005Channel Slope
in18.0Normal Depth
H:V0.750Left Side Slope
H:V0.750Right Side Slope
ft1.50Bottom Width
Results
cfs7.59Discharge
ft²3.9Flow Area
ft5.3Wetted Perimeter
in9.0Hydraulic Radius
ft3.75Top Width
in9.7Critical Depth
ft/ft0.049Critical Slope
ft/s1.93Velocity
ft0.06Velocity Head
ft1.56Specific Energy
0.332Froude Number
SubcriticalFlow Type
GVF Input Data
in0.0Downstream Depth
ft0.0Length
0Number Of Steps
GVF Output Data
in0.0Upstream Depth
N/AProfile Description
ft0.00Profile Headloss
ft/s0.00Downstream Velocity
ft/s0.00Upstream Velocity
in18.0Normal Depth
in9.7Critical Depth
ft/ft0.005Channel Slope
ft/ft0.049Critical Slope
Page 1 of 127 Siemon Company Drive Suite 200 W
Watertown, CT 06795 USA +1-203-755-1666
6/16/2022
FlowMaster
[10.03.00.03]
Bentley Systems, Inc. Haestad Methods Solution
CenterChambers Downstream.fm8
Section C
7"46"
24"
0.
5
%
Worksheet for Section C
Project Description
Manning
FormulaFriction Method
DischargeSolve For
Input Data
0.070Roughness Coefficient
ft/ft0.005Channel Slope
in7.0Normal Depth
H:V0.636Left Side Slope
H:V0.636Right Side Slope
ft2.00Bottom Width
Results
cfs1.14Discharge
ft²1.4Flow Area
ft3.4Wetted Perimeter
in4.9Hydraulic Radius
ft2.74Top Width
in2.5Critical Depth
ft/ft0.139Critical Slope
ft/s0.83Velocity
ft0.01Velocity Head
ft0.59Specific Energy
0.205Froude Number
SubcriticalFlow Type
GVF Input Data
in0.0Downstream Depth
ft0.0Length
0Number Of Steps
GVF Output Data
in0.0Upstream Depth
N/AProfile Description
ft0.00Profile Headloss
ft/sInfinityDownstream Velocity
ft/sInfinityUpstream Velocity
in7.0Normal Depth
in2.5Critical Depth
ft/ft0.005Channel Slope
ft/ft0.139Critical Slope
Page 1 of 127 Siemon Company Drive Suite 200 W
Watertown, CT 06795 USA +1-203-755-1666
6/16/2022
FlowMaster
[10.03.00.03]
Bentley Systems, Inc. Haestad Methods Solution
CenterChambers Downstream.fm8
Section D
24"60"
12"0.5%
Worksheet for Section D
Project Description
Manning
FormulaFriction Method
DischargeSolve For
Input Data
0.041Roughness Coefficient
ft/ft0.005Channel Slope
in24.0Normal Depth
H:V1.000Left Side Slope
H:V1.000Right Side Slope
ft1.00Bottom Width
Results
cfs14.35Discharge
ft²6.0Flow Area
ft6.7Wetted Perimeter
in10.8Hydraulic Radius
ft5.00Top Width
in15.0Critical Depth
ft/ft0.037Critical Slope
ft/s2.39Velocity
ft0.09Velocity Head
ft2.09Specific Energy
0.385Froude Number
SubcriticalFlow Type
GVF Input Data
in0.0Downstream Depth
ft0.0Length
0Number Of Steps
GVF Output Data
in0.0Upstream Depth
N/AProfile Description
ft0.00Profile Headloss
ft/s0.00Downstream Velocity
ft/s0.00Upstream Velocity
in24.0Normal Depth
in15.0Critical Depth
ft/ft0.005Channel Slope
ft/ft0.037Critical Slope
Page 1 of 127 Siemon Company Drive Suite 200 W
Watertown, CT 06795 USA +1-203-755-1666
6/16/2022
FlowMaster
[10.03.00.03]
Bentley Systems, Inc. Haestad Methods Solution
CenterChambers Downstream.fm8
Maple Highlands – Conner Homes
Appendix D
Appendix D
Peak Flow Control Application Map and MGS Flood Cal culations
LakeDesire
ShadyLake (MudLake)
PantherLake LakeYoungs
LakeWashington
Bl a c kRi ver
Gr eenRiv
e
r
C
edarRi verUV900
UV167
UV515
UV169
UV900
UV169
UV167BN IncBN IncBBNNIInnccSSEERReennttoonn II ssss aa qquuaahh RR dd
RReennttoonnMMaappllee VVaalllleeyyRRdd
MMaapplleeVVaalllleeyyHHwwyy
110088tthhAAvveeSSEESSWW SSuunnsseettBBllvvdd RRaaiinnii
eerrAAvveeNNNE 3rd StNE 3rd St
SW 43rd StSW 43rd St SS EE CCaarrrrRR dd
NE 4th StNE 4th St
SSEE RReennttoonn MMaappllee VVaalllleeyy RRddLLooggaannAAvveeNN
SR 515SR 515PPaarrkkAAvveeNNOOaakkeessddaalleeAAvveeSSWWSSuunnsseettBBllvvddNN EE
DDuuvvaallllAAvveeNNEEI-405 FWYI-405 FWY II--440055FFWWYYSR 167SR 167114400tthh
WWaayySS
EENNEE 2277tthh SStt
115566tthhAAvveeSSEEUUnniioonnAAvveeNNEE111166tthhAAvveeSSEESW 7th StSW 7th St
N 8th StN 8th St
PP uuggeettDDrrSSEE
RR
ee
nnttoonnAAvvee SS
SSWW 2277tthh SStt BBeennssoonnRRddSSWWiilllliiaammssAAvveeSSMMoonnrrooeeAAvveeNNEESE 128th StSE 128th St
II
nntt
eerr
uurr
bbaannAAvveeSS HHooqquuiiaammAAvveeNNEE8844tthhAAvveeSSSSEEPPeett
rr
oovvii
tt
sskkyyRRddEEVVaalllleeyyHHwwyySE 192nd StSE 192nd St
SE 60th StSE 60th St
TTaallbboottRRddSSRRee
nn
tt
oo
nn
AAvveeSS116644tthhAAvveeSSEESE 208th StSE 208th St
SE 72nd StSE 72nd St
RRaaiinniieerr
AAvvee
SS 111166tthhAAvveeSSEES 128th StS 128th St
NNeewwccaassttllee WWaayy
SS 221122tthh SStt
SS 118800tthh SStt CCooaall
CCrreeeekkPPkkwwyySSEESW 41st StSW 41st St
114400tthhAAvveeSSEE112288tthhAAvveeSSEE6688tthhAAvveeSSSSEE 116688tthh SStt
NE 12th StNE 12th St
BBee
aa
ccoonn
AA
vv
ee
SS
FFoorreesstt DDrr SSEE
SSEE 116644tthh SStt 114488tthhAAvveeSSEESSEE MMaayy VVaalllleeyy RRdd
SS EE JJ oo nn ee ss RR dd
SSEE 22 00 44 tthh WW aayySW 34th StSW 34th St
SE 144th StSE 144th St
114488tthhAAvveeSSEE115544tthhPPllSSEELL
aa
kk
ee
WWaa
sshhii
nnggtt
oonnBBll
vvddNNEEddmmoonnddssAAvveeNNEEAAbbeerrddeeeennAAvveeNNEEEEMM eerrcceerrWWaayyWWeessttVVaalllleeyyHHwwyyEast Valley RdEast Valley Rd,§-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 4.57
Program License Number: 200410007
Project Simulation Performed on: 07/06/2022 10:25 AM
Report Generation Date: 07/06/2022 10:26 AM
—————————————————————————————————
Input File Name: 2022-06-30 Wetpond.fld
Project Name: Chambers Plat
Analysis Title: 2022-07-06
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Climatic Region Number: 16
Full Period of Record Available used for Routing
Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097
Evaporation Station : 961044 Puget East 44 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) 4.610 4.610
Area of Links that Include Precip/Evap (acres) 0.000 0.000
Total (acres) 4.610 4.610
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
C, Forest, Flat 4.610
----------------------------------------------
Subbasin Total 4.610
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
C, Lawn, Mod 2.470
ROADS/FLAT 2.140
----------------------------------------------
Subbasin Total 4.610
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: New Structure Lnk2
Link Type: Structure
Downstream Link: None
User Specified Elevation Volume Table Used
Elevation (ft) Pond Volume (cu-ft)
100.00 0.
100.25 2887.
100.75 8030.
101.25 13294.
101.75 18677.
102.25 24181.
102.75 29800.
103.25 35531.
103.75 41370.
104.25 47315.
104.75 53349.
105.25 59452.
105.75 65632.
106.25 71872.
106.75 78149.
107.25 84463.
Constant Infiltration Option Used
Infiltration Rate (in/hr): 0.00
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 18.00
Common Length (ft) : 0.020
Riser Crest Elevation : 106.75 ft
Hydraulic Structure Geometry
Number of Devices: 2
---Device Number 1 ---
Device Type : Circular Orifice
Control Elevation (ft) : 100.00
Diameter (in) : 1.04
Orientation : Horizontal
Elbow : No
--- Device Number 2 ---
Device Type : Vertical Rectangular Orifice
Control Elevation (ft) : 103.99
Length (in) : 0.20
Height (in) : 33.14
Orientation : Vertical
Elbow : No
**********************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
********** Subbasin: Subbasin 1 **********
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 1.144
5-Year 1.538
10-Year 1.892
25-Year 2.441
50-Year 3.223
100-Year 4.038
200-Year 4.142
500-Year 4.252
********** Link: New Structure Lnk2 ********** Link Inflow Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 1.144
5-Year 1.538
10-Year 1.892
25-Year 2.441
50-Year 3.223
100-Year 4.038
200-Year 4.142
500-Year 4.252
********** Link: New Structure Lnk2 ********** Link WSEL Stats
WSEL Frequency Data(ft)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) WSEL Peak (ft)
======================================
1.05-Year 101.900
1.11-Year 102.080
1.25-Year 102.357
2.00-Year 103.297
3.33-Year 103.923
5-Year 104.550
10-Year 105.243
25-Year 105.707
50-Year 105.806
100-Year 106.090
***********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 1 877.313
_____________________________________
Total: 877.313
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 318.122
Link: New Structure Lnk2 0.000
_____________________________________
Total: 318.122
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 5.553 ac-ft/year, Post Developed: 2.013 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: New Structure Lnk2 **********
Basic Wet Pond Volume (91% Exceedance): 13607. cu-ft
Computed Large Wet Pond Volume, 1.5*Basic Volume: 20410. cu-ft
2-Year Discharge Rate : 0.053 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.34 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.19 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 1678.58
Inflow Volume Including PPT-Evap (ac-ft): 1678.58
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): 1678.31
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 Structure Lnk2
*** 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 0.116 2-Year 5.261E-02
5-Year 0.183 5-Year 8.055E-02
10-Year 0.228 10-Year 0.129
25-Year 0.313 25-Year 0.170
50-Year 0.344 50-Year 0.179
100-Year 0.373 100-Year 0.207
200-Year 0.552 200-Year 0.213
500-Year 0.793 500-Year 0.219
** 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%): -56.2% PASS
Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -56.2% PASS
Maximum Excursion from Q2 to Q50 (Must be less than 10%): -58.2% PASS
Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS
-------------------------------------------------------------------------------------------------
MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS
-------------------------------------------------------------------------------------------------
Maple Highlands – Conner Homes
Appendix E
Appendix E
On-Site BMPs Credits and Calculations
4000 20%
Lot Total Lot
Area (sf)
Blg Footprint
Area/Impervious
Coverage (sf)
Additional
Hardscape Area:
16x30 driveways
(sf)
% Impervious Lot BMP Imp.
Area Credit (sf)
Modeled Imp.
Coverage (sf)
Modeled
Landscape
Area (sf)
EX Tree (to
remain)
Canopy
Area (sf)
Impervious/Hard
Surface Area
Mitigated (sf)
Lot # 7 Impervious Area
(sf)
Lot 37
Modeled
Landscape
Area (sf)
1 11579 4394 480 42% 0 4394 7185 TOTAL 2370 474 2692 6362
2 10042 4192 480 47% 0 4192 5850
3 9650 3934 480 46% 0 3934 5716
4 10449 3836 480 41% 0 3836 6613
5 9947 3329 480 38% 191 3138 6809 *Min of 100 sf/tree. Cannot exceed 25% of impervious surface requiring mitigation
6 9018 3672 480 46% 0 3672 5346
7 9054 3343 480 42% 177 3166 5888
8 9078 2910 480 37% 610 2300 6778
9 9202 3601 480 44% 0 3601 5601
10 9179 3589 480 44% 0 3589 5590
11 9974 4366 480 49% 0 4366 5608
12 10378 4654 480 49% 0 4654 5724
Storm Tract 21137
TOTAL 138687 45820 978 44842 72708
C.2.9. The credit area below threshold equates to equal area of proposed impervious mitiagted area.
REDUCED IMPERVIOUS SURFACE CREDIT: RESTRICTED FOOTPRINT BMP TREE RETENTION CREDIT
C.2.14: The credit area equates to percentage of the ex tree canopy area.
CREDITS NOT USED
IN POND CALCS TO
BE CONSERVATIVE
Maple Highlands – Conner Homes
Appendix F
Appendix F
Pipe Conveyance
Worksheet for 12-Inch Pipe @0.5%
Project Description
Manning
FormulaFriction Method
Full Flow
CapacitySolve For
Input Data
0.012Roughness Coefficient
ft/ft0.005Channel Slope
in12.0Normal Depth
in12.0Diameter
cfs2.73Discharge
Results
cfs2.73Discharge
in12.0Normal Depth
ft²0.8Flow Area
ft3.1Wetted Perimeter
in3.0Hydraulic Radius
ft0.00Top Width
in8.5Critical Depth
%100.0Percent Full
ft/ft0.007Critical Slope
ft/s3.47Velocity
ft0.19Velocity Head
ft1.19Specific Energy
(N/A)Froude Number
cfs2.94Maximum Discharge
cfs2.73Discharge Full
ft/ft0.005Slope Full
UndefinedFlow Type
GVF Input Data
in0.0Downstream Depth
ft0.0Length
0Number Of Steps
GVF Output Data
in0.0Upstream Depth
N/AProfile Description
ft0.00Profile Headloss
%0.0Average End Depth Over Rise
%0.0Normal Depth Over Rise
ft/s0.00Downstream Velocity
ft/s0.00Upstream Velocity
in12.0Normal Depth
in8.5Critical Depth
ft/ft0.005Channel Slope
ft/ft0.007Critical Slope
Page 1 of 127 Siemon Company Drive Suite 200 W
Watertown, CT 06795 USA +1-203-755-1666
6/22/2022
FlowMaster
[10.03.00.03]
Bentley Systems, Inc. Haestad Methods Solution
CenterUntitled1.fm8
SECTION 3.2 RUNOFF COMPUTATION AND ANALYSIS METHODS
12/12/2016 2017 City of Renton Surface Water Design Manual
3-22
TABLE 3.2.2.A EQUIVALENCE BETWEEN SCS SOIL TYPES AND TYPICAL
CONTINUOUS MODELING SOIL TYPES
SCS Soil Type
SCS
Hydrologic
Soil Group
Soil Group for
Continuous
Model Notes
Alderwood (AgB, AgC, AgD) C Till
Arents, Alderwood Material (AmB, AmC) C Till
Arents, Everett Material (An) B Outwash 1
Beausite (BeC, BeD, BeF) C Till 2
Bellingham (Bh) D Till 3
Briscot (Br) D Till 3
Buckley (Bu) D Till 4
Earlmont (Ea) D Till 3
Edgewick (Ed) C Till 3
Everett (EvB, EvC, EvD, EwC) A/B Outwash 1
Indianola (InC, InA, InD) A Outwash 1
Kitsap (KpB, KpC, KpD) C Till
Klaus (KsC) C Outwash 1
Neilton (NeC) A Outwash 1
Newberg (Ng) B Till 3
Nooksack (Nk) C Till 3
Norma (No) D Till 3
Orcas (Or) D Wetland
Oridia (Os) D Till 3
Ovall (OvC, OvD, OvF) C Till 2
Pilchuck (Pc) C Till 3
Puget (Pu) D Till 3
Puyallup (Py) B Till 3
Ragnar (RaC, RaD, RaC, RaE) B Outwash 1
Renton (Re) D Till 3
Salal (Sa) C Till 3
Sammamish (Sh) D Till 3
Seattle (Sk) D Wetland
Shalcar (Sm) D Till 3
Si (Sn) C Till 3
Snohomish (So, Sr) D Till 3
Sultan (Su) C Till 3
Tukwila (Tu) D Till 3
Woodinville (Wo) D Till 3
Notes:
1. Where outwash soils are saturated or underlain at shallow depth (<5 feet) by glacial till, they should be treated as till
soils.
2. These are bedrock soils, but calibration of HSPF by King County shows bedrock soils to have similar hydrologic
response to till soils.
3. These are alluvial soils, some of which are underlain by glacial till or have a seasonally high water table. In the absence
of detailed study, these soils should be treated as till soils.
4. Buckley soils are formed on the low-permeability Osceola mudflow. Hydrologic response is assumed to be similar to that
of till soils.
3.2.2 CONTINUOUS MODELS AND THE RUNOFF FILES METHOD
2017 City of Renton Surface Water Design Manual 12/12/2016
3-23
Land Cover Types in Continuous Modeling
Continuous models support land cover types including forest, pasture, grass, and impervious. These cover
types shall be applied in accordance with Core Requirement #3 and as specified in Table 3.2.2.B.
Predevelopment land cover types are determined by whether the project is in a Peak Rate Flow Control
Standard Area or Flow Control Duration Standard Area and whether the area in question is a target
surface, as defined in Section 1.2.3.1. Target surfaces within Peak Rate Flow Control Standard Areas and
Flow Control Duration Standard Matching Existing Condition Areas and non-target surfaces are modeled
as existing site conditions; for target surfaces in Flow Control Duration Standard Matching Forested
Condition Areas, the predeveloped condition is assumed to be forested (historical) site conditions.
TABLE 3.2.2.B CONTINUOUS MODEL COVER GROUPS AND AREAS OF APPLICATION
Continuous
Model Application
Cover Group Predevelopment Post-Development
Forest All forest/shrub cover,
irrespective of age.
All permanent (e.g., protected by covenant or critical
area designation) onsite forest/shrub cover,
irrespective of age, planted at densities sufficient to
ensure 80%+ canopy cover within 5 years.
Pasture All grassland, pasture land,
lawns, and cultivated or cleared
areas, except for lawns in
redevelopment areas with
predevelopment densities in
excess of 4 DU/GA.
Unprotected forest in rural residential development
shall be considered half pasture, half grass.
Pasture areas to be retained on large rural residential
lots (10 acres or greater) may be modeled as half
pasture, half grass.
Grass Lawns in redevelopment areas
with predevelopment densities in
excess of 4 DU/GA.
All post-development grassland and landscaping and
all onsite forested land not protected by covenant or
designated as a protection area (wellhead, wetland,
or buffer) in RMC 4-3-050 (except in rural areas as
noted above).
For purposes of runoff modeling, underdrained
pervious areas may be modeled explicitly to account
for attenuation and infiltration, or may be modeled as
50% impervious/50% grass where either: (a) there is
no added liner, (b) where the added liner is a
treatment liner, or (c) where the added liner is one
that does not restrict infiltration rates below the in situ
soil infiltration rate. Other lined underdrained systems
must be modeled explicitly or as 100% impervious.
Wetland All delineated wetland areas. All delineated wetland areas.
Impervious(1) All impervious surfaces,
including heavily compacted
gravel and dirt roads, parking
areas, etc., and open water
bodies (ponds and lakes).
All impervious surfaces, including compacted gravel
and dirt roads, parking areas, etc., and open water
bodies, including onsite detention and water quality
ponds.(2)
(1) Impervious acreage used in computations should be the effective impervious area (EIA). This is the effective area as
determined through layouts of the proposal and on-site BMP credit reductions from Table 1.2.9.A in Chapter 1. Non-
effective impervious areas are considered the same as the surrounding pervious land cover.
(2) To avoid iterations in the facility sizing process, the “assumed size” of the facility need only be within 80% of the final
facility size when modeling its contribution of runoff from direct rainfall.
4.2.1 PIPE SYSTEMS
2017 City of Renton Surface Water Design Manual 12/12/2016
4-21
V = R2/3 S1/2 (4-1)
or use the continuity equation, Q = AV, such that:
Q = A R2/3 S1/2 (4-2)
where Q = discharge (cfs)
V = velocity (fps)
A = area (sf)
n = Manning's roughness coefficient; see Table 4.2.1.D below
R = hydraulic radius = area/wetted perimeter (ft)
S = slope of the energy grade line (ft/ft)
For pipes flowing partially full, the actual velocity may be estimated from the hydraulic properties shown
in Figure 4.2.1.G by calculating Qfull and Vfull and using the ratio Qdesign/Qfull to find V and d (depth of
flow).
Table 4.2.1.D provides the recommended Manning's “n” values for preliminary design using the
Uniform Flow Analysis method for pipe systems. Note: The “n” values for this method are 15% higher in
order to account for entrance, exit, junction, and bend head losses.
TABLE 4.2.1.D MANNING’S “n” VALUES FOR PIPES
Type of Pipe Material Analysis Method
Uniform Flow
(preliminary
design)
Backwater Flow
(capacity
verification)
A. Concrete pipe, lined CPE pipe and lined PP pipe
B. Annular Corrugated Metal Pipe or Pipe Arch:
1. 2-2/3″ x 1/2″ corrugation (riveted):
a. plain or fully coated
b. paved invert (40% of circumference paved):
1) flow at full depth
2) flow at 80% full depth
3) flow at 60% full depth
c. treatment 5
2. 3″ x 1″ corrugation
3. 6″ x 2″ corrugation (field bolted)
C. Helical 2-2/3″ x 1/2″ corrugation and unlined CPE pipe
D. Spiral rib metal pipe and PVC pipe
E. Ductile iron pipe cement lined
F. Solid wall HDPE pipe (butt fused only)
0.014
0.028
0.021
0.018
0.015
0.015
0.031
0.035
0.028
0.013
0.014
0.009
0.012
0.024
0.018
0.016
0.013
0.013
0.027
0.030
0.024
0.011
0.012
0.009
n
49.1
n
49.1
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.57
Program License Number: 200410007
Project Simulation Performed on: 06/27/2022 5:07 PM
Report Generation Date: 06/27/2022 5:07 PM
—————————————————————————————————
Input File Name: Conveyance.fld
Project Name: Maple Highlands
Analysis Title: Chambers Plat Conveyance Calc
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Climatic Region Number: 16
Full Period of Record Available used for Routing
Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097
Evaporation Station : 961044 Puget East 44 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) 4.610 4.610
Area of Links that Include Precip/Evap (acres) 0.000 0.000
Total (acres) 4.610 4.610
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
C, Forest, Mod 4.610
----------------------------------------------
Subbasin Total 4.610
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
C, Lawn, Flat 2.460
ROADS/FLAT 2.150
----------------------------------------------
Subbasin Total 4.610
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 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: 0
***********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 1 877.198
_____________________________________
Total: 877.198
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 317.075
_____________________________________
Total: 317.075
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 5.552 ac-ft/year, Post Developed: 2.007 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 0
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Subbasin: Subbasin 1
*** 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 0.119 2-Year 1.103
5-Year 0.190 5-Year 1.446
10-Year 0.248 10-Year 1.804
25-Year 0.341 25-Year 2.299
50-Year 0.428 50-Year 2.999
100-Year 0.454 100-Year 3.721
200-Year 0.726 200-Year 3.827
500-Year 1.091 500-Year 3.944
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
< 2.73 cfs (12" @0.5%)
Maple Highlands – Conner Homes
Appendix G
Appendix G
Erosion Control Plan and Details
(To Be Provided With Future Submittal)
Maple Highlands – Conner Homes
Appendix H
Appendix H
SWPPP
Page 1
Construction Stormwater General Permit (CSWGP)
Stormwater Pollution Prevention Plan
(SWPPP)
for
Maple Highlands
Prepared for:
Department of Ecology
Northwest Region Office
Permittee / Owner Developer Operator / Contractor
Conner Homes Conner Homes Conner Homes
13818 152nd Ave SE Renton, WA 98059
Certified Erosion and Sediment Control Lead (CESCL)
Name Organization Contact Phone Number
TBD TBD TBD
SWPPP Prepared By
Name Organization Contact Phone Number
Glorie Anne Calipjo KPFF Consulting Engineers 206.622.5822
SWPPP Preparation Date
June / 17 / 2022
Project Construction Dates
Activity / Phase Start Date End Date
[Insert Text] MM / DD / YYYY MM / DD / YYYY
Page 2
Table of Contents
List of Acronyms and Abbreviations ........................................................................................... 4
1.0 Project Information ............................................................................................................... 5
1.1 Existing Conditions ........................................................................................................... 5
Category 5 water: 3 Listings ................................................................................................ 6
1.2 Proposed Construction Activities ...................................................................................... 7
2.0 Construction Stormwater Best Management Practices (BMPs) ............................................ 8
2.1 The 13 Elements .............................................................................................................. 8
2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits .............................................. 9
2.1.2 Element 2: Establish Construction Access ………………………………………………………………10
2.1.3 Element 3: Control Flow Rates ..................................................................................11
2.1.4 Element 4: Install Sediment Controls .........................................................................12
2.1.5 Element 5: Stabilize Soils ..........................................................................................13
2.1.6 Element 6: Protect Slopes .........................................................................................15
2.1.7 Element 7: Protect Drain Inlets ..................................................................................17
2.1.8 Element 8: Stabilize Channels and Outlets................................................................18
2.1.9 Element 9: Control Pollutants ....................................................................................20
2.1.10 Element 10: Control Dewatering ..............................................................................23
2.1.11 Element 11: Maintain BMPs ....................................................................................24
2.1.12 Element 12: Manage the Project .............................................................................25
2.1.13 Element 13: Protect Low Impact Development (LID) BMPs .....................................28
3.0 Pollution Prevention Team ..................................................................................................29
4.0 Monitoring and Sampling Requirements ..............................................................................30
4.1 Site Inspection .................................................................................................................30
4.2 Stormwater Quality Sampling ..........................................................................................30
4.2.1 Turbidity Sampling ....................................................................................................30
4.2.2 pH Sampling .............................................................................................................32
Page 3
5.0 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies ..........................33
5.1 303(d) Listed Waterbodies ...............................................................................................33
5.2TMDL Waterbodies ...........................................................................................................34
6.0 Reporting and Record Keeping ...........................................................................................35
6.1 Record Keeping ...............................................................................................................35
6.1.1 Site Log Book ............................................................................................................35
6.1.2 Records Retention ....................................................................................................35
6.1.3 Updating the SWPPP ................................................................................................35
6.2 Reporting .........................................................................................................................36
6.2.1 Discharge Monitoring Reports ...................................................................................36
6.2.2 Notification of Noncompliance ...................................................................................36
List of Tables
Table 1: Summary of Existing Conditions .................................................................................................... 6
Table 2: Pollutants .....................................................................................................................................20
Table 3: pH-Modifying Sources ..................................................................................................................22
Table 4: Dewatering BMPs ........................................................................................................................ 23
Table 5: Management ................................................................................................................................25
Table 6: BMP Implementation Schedule ....................................................................................................26
Table 7: Team Information ........................................................................................................................28
Table 8: Turbidity Sampling Method ..........................................................................................................32
Table 9: pH Sampling Method ................................................................................................................... 25
List of Appendices
Appendix A – Site Map TESC Plan
Appendix B – BMP Details
Appendix C – Standard Site Inspection Form
Appendix D – State of Washington Construction Stormwater General Permit (CSWGP)
Appendix E – Engineering Calculations
Appendix F – 303(d) List Waterbodies / TMDL Waterbodies Information
Appendix G – Correspondence
Appendix H – Contaminated Site Information
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
Page 5
Project Information (1.0)
Project/Site Name: Chambers Bagnell Plat/Maple Highlands
Street/Location: 13818 152nd Ave SE & 13929 154th Ave SE
City: Renton State: Wa Zip code: 98059
Subdivision: N/A
Receiving waterbody: Cedar River
Existing Conditions (1.1)
Total acreage (including support activities such as off-site equipment staging yards, material
storage areas, borrow areas).
Total acreage: 4.61 Acres
Disturbed acreage: 4.61 Acres
Existing structures: Two single-family residences and several outbuildings.
Landscape topography: The existing site is mainly covered in vegetation, trees, and shrubs
along the property perimeter. The project site is currently compacted as Alderwood gravelly
loam (AgC) in accordance to the USDA Web Soil Survey.
Drainage patterns: Stormwater runoff flows from the surface along 154th Ave SE towards the
southwest side of the site in 152nd Ave SE. The existing site generally slopes 2-5% to the
southwest, with elevation change of approximately 14 feet across the site. Storrmwater flows
through roadside ditches 0.25 miles downstream of the site and discharges to the Cedar River
1.0 miles downstream.
Existing Vegetation: The existing site consist of vegetation such as grass, shrubs, and trees that
surrounds the residences and property perimeter.
Critical Areas (wetlands, streams, high erosion risk, steep or difficult to stabilize slopes): N/A
List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the
receiving waterbody:
Category 5 water: 3 Listings
Temperature; Listing ID 4816; Assessment Unit ID: 17110012000024
Dissolved Oxygen; Listing ID 10654; Assessment Unit ID: 17110012000024
pH; Listing ID10655; Assessment Unit ID: 17110012000024
Page 6
Table 1 includes a list of suspected and/or known contaminants associated with the construction
activity.
Table 1 – Summary of Site Pollutant Constituents
Constituent
(Pollutant) Location Depth Concentration
Proposed Construction Activities (1.2)
Description of site development (example: subdivision):
The existing site consist of two single family residences and outbuildings. The project site will be
subdivided into 13 parcels, with a public right-of-way and a storm tract. The project will construct
12 single-family homes, SE 139th Place, and 153rd Ave SE onsite. The project will include
frontage improvements, grading, utilities, and stormwater mitigation facilities.
Description of construction activities (example: site preparation, demolition, excavation):
The existing structures will be demolished for a 12-lot residential development with stormwater
facilities, paved access roads, and utilities constructed within the site. Construction activities
includes the construction of perimeter walls along the proposed residences with bearing loads of
two to six kips per linear foot and series of columns with a maximum load of 30 kips. A slab-on-
grade floor loading of 150 pounds per square foot (psf) are expected.
Description of site drainage including flow from and onto adjacent properties. Must be consistent
with Site Map in Appendix A:
The proposed site drainage will alter drainage patterns where runoff is conveyed to the
southeast. Within the site, runoff will be collected by several catch basins in the public right-of-
way and into a combination wetpool-detention pond. From the project site, runoff will flow along
the roadside ditch system on 154th Ave SE to the intersection of SE 142nd. Within ¼ mile
downstream of the site, the existing and proposed drainage path rejoins.
Description of final stabilization (example: extent of revegetation, paving, landscaping):
[Insert Text]
Contaminated Site Information:
Proposed activities regarding contaminated soils or groundwater (example: on-site treatment
system, authorized sanitary sewer discharge):
[Insert Text]
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)
Element 1: Preserve Vegetation / Mark Clearing Limits (2.1.1)
List and describe BMPs: Preserving Natural Vegetation (C101), High-Visibility Fence (C103)
High-visibility fencing will be installed along the construction site limits. Installation of siltation
control fencing, anchored straw, or coir wattles on the downhill side of work areas. All clearing
limits, vulnerable areas, and trees must be marked to be preserved prior construction activities.
During construction, trees and sensitive areas shall be preserved on steep slopes. The Certified
Erosion and Sediment Control Lead will inspect the BMP daily and make modifications if the
exisiting BMP is ineffective to prevent erosion and sediment issues.
Installation Schedules: BMPs are to be installed prior construction and will be modified
according to construction limits.
Inspection and Maintenance plan: Inspection of construction fencing shall be inspected
according to the 2019 Department of Ecology Stormwater Management Manual for Western
Washington (2019 SWMMWW).
Responsible Staff: CESCL
Page 8
Element 2: Establish Construction Access (2.1.2)
List and describe BMPs: Stabilized Construction Access (C105), Wheel Wash (C106),
Construction Road/Parking Area Stabilization (C107)
To minimize dust generation and vehicles tracking sediment off-site, a stabilized pad of quarry
spalls will be constructed at a stabilized construction entrance/exit. The construction access is
stabilized to minimize the amount of sediment conveyed onto paved roads off-site from vehicles
and equipments.
Wheel wash is necessary to remove dirt from the wheels of vehicles to reduce the amount of
sediment along the paved roads prior to vehicles leaving the construction site.
All permanent and temporary roads and parking areas are to be constructed with enough
stability.
Installation Schedules: BMPs are to be installed prior construction.
Inspection and Maintenance plan: Inspection of construction access, wheel wash, and
parking areas shall be inspected according to the 2019 Department of Ecology Stormwater
Management Manual for Western Washington (2019 SWMMWW).
Responsible Staff: CESCL
Page 9
Element 3: Control Flow Rates (2.1.3)
Will you construct stormwater retention and/or detention facilities?
Yes No
Will you use permanent infiltration ponds or other low impact development (example: rain
gardens, bio-retention, porous pavement) to control flow during construction?
Yes No
The characteristics of the soil infiltration are indicated to be poor which makes rain gardens, bio-
retentions, permeable pavements, and infiltration ponds to be unfeasible.
List and describe BMPs: Temporary Interceptor Swale (C200), Check Dams (C207), Silt Fence
(C233), Wattles (C235)
The interceptor swale must be installed during construction for concentrated flows and may be
observed after a rainfall event. All sediments in the flow area must be removed immediately.
Repairments for damages are to be completed caused by construction traffic.
To minimize flow rates and energy, check dams are to be constructed across a ditch or swale.
Check dams are to be installed perpendicular to the flow of water and must not be placed in
streams unless the State Department of Fish and Wildlife makes an approval. The rock shall be
constructed large enough for a complete coverage of the swale and ditch and to ensure that the
edges are higher than the center of the dam. Silt fences provides a physical barrier to minimize
the transport of coarse sediment from the construction site. Wattles shall be installed during the
construction phase to minimize the flow rate and captures sediments.
Installation Schedules: BMPs are to be installed prior construction.
Inspection and Maintenance plan: Inspection of an interceptor swale, check dams, silt fence,
and wattles shall be inspected according to the 2019 Department of Ecology Stormwater
Management Manual for Western Washington (2019 SWMMWW).
Responsible Staff: CESCL
Element 4: Install Sediment Controls (2.1.4)
List and describe BMPs: Storm Drain Inlet (C220), Silt Fence (C233), Wattles (C235), Sediment
Trap (C240), Dust Control (C410)
Inlets shall have protection downslope 500 feet of a construction area and prevents coarse
sediment from entering drainage systems. Storm drain inlets shall be protected before the
disturbed drainage area is stabilized.
Prior to grading, silt fencing will be installed around the perimeters of disturbance and to be
placed downslope of all disturbed areas. Silt fences minimizes the transport of sediments along
the runoff and shall not be constructed in streams and V-shaped ditches. Wattles consist of
Page 10
straw or compost and are installed in shallow trenches and along constructed slopes. Wattles
act as a sediment control barrier to reduce the velocity and captures sediments.
Sediment traps shall be installed prior to disturbance along the drainage area, which is a small
temporary ponding area used to gather and store sediments during construction. To prevent the
transport of dust from disturbed soil surfaces onto drainage ways and roads, irrigation systems
may be utilized as a dust control and are installed at the beginning phase of construction.
Installation Schedules: BMPs are to be installed prior construction.
Inspection and Maintenance plan: Inspection of storm drain inlets, silt fencing, wattles, and
sediment traps shall be inspected according to the 2019 Department of Ecology Stormwater
Management Manual for Western Washington (2019 SWMMWW).
Responsible Staff: CESCL
Page 11
Element 5: Stabilize Soils (2.1.5)
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.
Anticipated project dates: Start date: End date:
Will you construct during the wet season?
Yes No
List and describe BMPs: Plastic Covering (C123), Dust Control (C140)
Plastic covering shall be installed on disturbed areas as it runs up and down the slope. If the
slope length is less than 10 feet, the plastic may be placed perpendicular to a slope. Slopes
subject to wind must have all seams taped on long and wide slope. At the top of the slope, the
plastic shall be placed into a small (12-inch wide by 6-inch deep) slot trench and backfill with
soil. Geotextile bags are to be placed every 3 to 6 feet along the seams and sandbags are to be
lowered.
Dust control shall be installed prior to construction onsite such as irrigation water. Disturbed soil
areas shall be sprayed with a dust palliative in accordance to the manufacturer’s cautions and
instructions. The construction site will be sprayed with water until the surface is damped.
Installation Schedules: BMPs are to be installed prior construction.
Inspection and Maintenance plan: Inspection of plastic covering and dust control shall be
inspected according to the 2019 Department of Ecology Stormwater Management Manual for
Western Washington (2019 SWMMWW).
Inspections observes for tears, rips, and open seams and provides immediate repairments to
prevent large runoff, which results in severe erosion.
Responsible Staff: CESCL
Page 12
Element 6: Protect Slopes (2.1.6)
Will steep slopes be present at the site during construction?
Yes No
List and describe BMPs: Temporary Interceptor Swale (C200), Check Dams (C207)
The installation of a dike or swale shall be stabilized with permanent or temporary vegetation
during construction. An interceptor dike or swale must be utilized where runoff is transported to
an erosion control from an exposed site. The interceptor dike or swale shall be installed
horizonatally across a disturbed slope to minimize the amount of runoff flowing down the slope.
Check dams shall be constructed on rock dams or pea-gravel filled bags and must be placed
perpendicular to the flow, and must be installed on an area where runoff from disturbed slopes
transport to an erosion control facility.
Installation Schedules: BMPs are to be installed prior construction.
Inspection and Maintenance plan: Inspection of an interceptor swale and check dams shall be
inspected in accordance to the 2019 Department of Ecology Stormwater Management Manual
for Western Washington (2019 SWMMWW).
Responsible Staff: CESCL
Page 13
Element 7: Protect Drain Inlets (2.1.7)
List and describe BMPs: Storm Drain Inlet (C220)
All storm drain inlets must be protected to prevent unfiltered stormwater from entering the
drainage system. All access roads must be cleared from sediments and prevent untreated water
from entering storm drains. Drain inlets shall be placed downslope and within 500 feet from a
disturbed area or construction area. Drain inlets will prevent unfiltered water from entering the
drainage conveyance system.
Installation Schedules: BMPs are to be installed prior construction.
Inspection and Maintenance plan: Inspection of storm drain inlets shall be inspected in
accordance to the 2019 Department of Ecology Stormwater Management Manual for Western
Washington (2019 SWMMWW). Inspections on inlets occur on a weekly basin at a minimimum
and daily during storm events.
Responsible Staff: CESCL
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: Check Dams (C207), Outlet Protection (C209)
To minimize flow rates and energy, check dams are to be constructed across a ditch or swale.
Check dams are to be installed perpendicular to the flow of water and must not be placed in
streams unless the State Department of Fish and Wildlife approves. The rock shall be
constructed large enough for complete coverage of the swale and ditch and to ensure that the
edges are higher than the center of the dam.
Outlet protection will be placed at the outlet of a pipe to provide protection from erosion by lining
a minimum of 6 feet downstream and along the channel sides a minimum of 1 foot above the
tailwater elevation.
Installation Schedules: BMPs are to be installed prior construction.
Inspection and Maintenance plan: Inspection of check dams and outlets shall be inspected
according to the 2019 Department of Ecology Stormwater Management Manual for Western
Washington.
Responsible Staff: CESCL
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)
Concrete and Concrete Slurry – Stoneway Concrete
Diesel Gasoline – Source varies
Hydraulic Fluid – Source varies
List and describe BMPs: Dust Control (C140), Concrete Handling (C151), Material Delivery,
Storage, and Containment (C153), Concrete Washout Area (C154)
All pollutants that occur onsite will be disposed to prevent contamination of stormwater.
Concrete truck drums must be washed at an approved off-site location. Wash equipments in
areas that do not drain to natural infiltration areas. Temporary storage area shall be located
near construction entrances and away from storm drains. Hazardous material storage onsite
must be minimized.
Demolished walls or sidewalks will require Dust Control measures. All pollutants such as waste
materials and demolition debris that occur on-site will be disposed in a manner that does not
result in stormwater contamination. Prevention of water and slurry from sawcutting operations
from entering the waters of the State will be implemented.
Installation Schedules: BMPs are to be installed prior construction.
Inspection and Maintenance plan: Inspection of check dams and outlets shall be inspected in
accordance to the 2019 Department of Ecology Stormwater Management Manual for Western
Washington (2019 SWMMWW).
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 (C153)
Temporary storage area must be located away from vehicular traffics and near construction
entrances, and away from storm drains. Hazardous material storage on-site must be reduced
and all storing materials must be covered during the wet weather season. Materials will be
placed in secondary containment such as an earthen dike and chemicals must not be placed on
the ground.
Page 16
Installation Schedules: BMPs are to be installed prior construction.
Inspection and Maintenance plan: Inspection of material delivery, storage, and containment
shall be inspected in accordance to the 2019 Department of Ecology Stormwater Management
Manual for Western Washington.
Responsible Staff: CESCL
Will wheel wash or tire bath system BMPs be used during construction?
TBD
Yes No
List and describe BMPs: Wheel wash or tire bath wastewater shall discharge to a separate
onsite treatment system to prevent wastewater from discharging to surface water such as
sanitary sewer or a closed-loop recirculation. The wastewater management agency provides
permits for the project site.
Installation Schedules: Wheel wash systems must be placed at the start of the Grade and
Fill construction. Wheel wash systems shall be placed on-site daily, and may be used on
several days at contractor discretion.
Inspection and Maintenance plan: Inspection on wheel wash occurs as needed and after use.
Responsible Staff: CESCL
Will pH-modifying sources be present on-site?
Yes No If yes, check the source(s).
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]
Page 17
List and describe BMPs: Concrete Washout Area (BMP C154)
All concrete washout washers must not remain on asphalt or concrete surfaces, and shall be
cleared off. Disposal of washout water must not violate the quality of groundwater or surface
water.
Installation Schedules: Concrete washout washers must be installed prior to use.
Inspection and Maintenance plan: Concrete washout washers shall be inspected and
maintained as needed.
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.
Element 10: Control Dewatering (2.1.10)
Dewatering within the construction is expected to be directed towards existing truck ponds and
flow out to sanitary sewer.
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 applicable for dewatering.
Installation Schedules: N/A
Inspection and Maintenance plan: N/A
Responsible Staff: N/A
Page 18
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 continued performance of their intended function.
Maintenance and repair shall be conducted in accordance with each particular 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.
Page 19
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 taken into account.
· 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)
Page 20
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]
Phase of Construction
Project
Stormwater BMPs Date Wet/Dry
Season
Page 21
[Insert construction
activity]
[Insert BMP] [MM/DD/YYYY] [Insert
Season]
Page 22
Element 13: Protect Low Impact Development (LID) BMPs (2.1.13)
No infiltrating LIDs are mentioned or proposed.
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 TBD 206-622-5822
Emergency Ecology
Contact
Kendra Henderson 360-870-6757
Emergency Permittee/
Owner Contact
TBD TBD
Non-Emergency Owner
Contact
Tom Neubauer 425-452-4042
Monitoring Personnel TBD TBD
Ecology Regional Office Rachel McCrea
Northwest Regional Office
206-594-0000
Page 23
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 log book. 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
· Stormwater sampling data
A site inspection form is included in Appendix C.
The site log book must be maintained on-site within reasonable access to the site and be made
available upon request to Ecology or the local jurisdiction.
The receiving waterbody, Cedar River, is impaired for: dissolved oxygen, temperature, and pH.
All stormwater and dewatering discharges from the site are subject to an effluent limit of 8.5 su
for pH and/or 25 NTU for turbidity.
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.
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)
Y Transparency Tube (option for disturbances less than 1 acre and up to 5 acres in size)
Page 24
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
· Northwest Region (King, Kitsap, Island, San Juan, Skagit, Snohomish,
Whatcom): (425) 649-7000
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.
Page 25
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:
Check the analysis method you will use:
Table 8 – pH Sampling Method
Y pH meter
pH test kit
Wide range pH indicator paper
Page 26
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): pH within the Cedar River is indicated in Category 5
The receiving waterbody, Cedar River, is impaired for: temperature, dissolved oxygen, and pH.
All stormwater and dewatering discharges from the site are subject to an effluent limit of 8.5 su
for pH and/or 25 NTU for turbidity.
List and describe BMPs: Treating and Disposing of High pH Water C252,
pH: Permittees are required to apply the 2019 Stormwater Management Manual for Western
Washington to conduct pH sampling (see BMP C252).
Prior to discharge to ground water, high pH levels in stormwater above 8.5 must be lowered to
an appropriate range of 6.5 to 8.5 which is a typical range to maintain the survival of aquatic
organisms and natural watercourses. Stormwater with pH levels out of range may be
neutralized on site or discharged to ground water in accordance to the Construction Stormwater
General permit.
Temperature: To minimize high temperature, vegetation such as trees can be used to extend
shading over the drainage and surface water.
Dissolved Oxygen: Aerators or fountains shall be installed during the summer to prevent
dissolved oxygen conditions from depleting. Dechlorinate agents should not be over applied as
it reduces the dissolved oxygen concentration and pH in discharge or receiving waters.
TMDL Waterbodies (5.2)
This project does not discharge directly to any TDML Waterbodies.
Waste Load Allocation for CWSGP discharges:
[Insert text here]
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 F.
Page 27
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.
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)
Page 28
Discharge Monitoring Reports (6.2.1)
Cumulative soil disturbance is one (1) acre or larger; therefore, Discharge Monitoring
Reports (DMRs) will be submitted to Ecology monthly. If there was no discharge during a given
monitoring period the DMR will be submitted as required, reporting “No Discharge”. The DMR
due date is fifteen (15) days following the end of each calendar month.
DMRs will be reported online through Ecology’s WQWebDMR System.
To sign up for WQWebDMR go to:
https://www.ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Water-quality-
permits-guidance/WQWebPortal-guidance
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.
Specific information to be included in the noncompliance report is found in Special Condition
S5.F.3 of the CSWGP.
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:
Page 29
1. Your name and / Phone number
2. Permit number
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.
Page 30
Appendices
A. Site Map
B. BMP Details
C. Standard Site Inspection Form
D. State of Washignton Construction Stormwater General Permit (CSWGP)
E. Engineering Calculations
F. 303(d) List Waterbodies Information
G. Correspondence
Ecology
Local Government
H. Contaminated Site Information
Administrative Order
Sanitary Management Permit
Soil and Groundwater Reports
Maps and Figures Depiciting Contamination
Page 31
Page 32
Appendix A
Site Map
Page 33
3
BPE 386.4
376376376390
384
386
388
392
394388
38
6
386386386 3863863863
8
6 3861
BPE 388.4
2
BPE 387.4
4
BPE 385.0
12
BPE 386.0
11
BPE 386.1
5
BPE 385.4
6
BPE 386.1
7
BPE 386.4
10
BPE 387.0
9
BPE 386.6
8
BPE 386.3
SE 138TH PL
152ND AVE SE153RD AVE SESE 5TH PL
SE 5TH PL
154TH AVE SEROCKERY
ROCKERY
CIP RETAINING WALL
CB #12
RIM=385.50
12" CPEP IE OUT=382.32 (SE)
CB #11
RIM=385.81
12" DI IE IN=382.18 (NW)
12" DI IE OUT=382.18 (E)CB #5
RIM=384.51
12" DI IE OUT=381.15 (N)
CB#4
RIM=384.32
12" DI IE IN=381.01 (S, W)
12" DI IE OUT=381.01 (E)
CB #1
RIM=383.68
12" DI IE OUT=381.03 (W)CB #2
RIM=383.68
12" DI IE IN=380.91 (W)
12" DI IE OUT=380.91 (SE)
CB #3
RIM=384.53
12" DI IE IN=380.73 (NW)
12" DI IE IN=380.73 (W)
12" DI IE OUT=380.73 (E)
CB #6
RIM=385.28
12" CPEP IE IN=380.55 (W)
12" CPEP IE IN=380.55 (S)
12" CPEP IE OUT=380.55 (E)
CB #7
RIM=385.31
12" CPEP IE OUT=380.79 (N)
CB #8
RIM=386.82
12" CPEP IE IN=379.30 (W)
12" CPEP IE OUT=379.30 (S)
CB #9
RIM=390.91
12" DI IE OUT=388.16 (E)
CB #10
RIM=390.98
12" DI IE IN=388.03 (W)
EX 18" CPEP IE IN =387.47 (N)
EX 18" CPEP IE OUT =387.47 (S)
CONTROL STRUCTURE
RIM=385.25
12" CPEP IE OUT=378.75 (E)
CB #16
RIM=382.64
12" CPEP IE IN=378.52 (W)
12" CPEP IE OUT=378.52 (E)
27 LF 12" CPEP @ 0.5%
28 LF 12" DI @ 0.5%48 LF 12" DI
@ 0.5%
22 LF 8" DI @ 0.5%
40 LF 12" DI @ 0.5%
36 LF 12"
CPEP @ 0.5%
20 LF 12"
CPEP @ 1.0%
150 LF 12"
CPEP @ 1.5%
47 LF 12"
CPEP @ 1.5%
15 LF 12" CPEP @ 0.7%
26 LF 12" CPEP
@ 0.7%
27 LF 12" DI @ 0.5%TW 385.70BW 381.67TW 385.73BW 379.53TW 385.75BW 377.34T
W
3
8
5
.
7
5
B
W
3
7
9
.
5
2
TW
3
8
5
.
4
5
BW
3
8
1
.
0
0
T
W
3
8
5
.
4
5
B
W
3
8
5
.
0
0
TW
3
8
5
.
4
5
BW
3
7
4
.
0
8TW 385.45BW 374.08T
W
3
8
8
.
5
5
B
W
3
8
8
.
5
5
TW
3
9
1
.
2
5
BW
3
8
9
.
0
1
TW
3
9
3
.
6
3
BW
3
8
9
.
0
0 TW 396.00BW 390.00TW 387.16BW 387.16386TOP OF POND 385.45
BOT OF POND 374.08
INTERIOR SLOPES 3:1
EX CB
RIM=382.40
12" CPEP IE IN=378.34 (W)
EX 4" PVC IE IN=378.99 (NE)
EX 18" CPEP IE IN=378.38 (N)
EX 18" CPEP IE OUT=378.34 (S)
TREE TRACT BOUNDARY
24 LF 12"
CPEP @ 1.5%
CB #14
RIM=386.85
12" CPEP IE IN=378.94
12" CPEP IE OUT=378.94 380
376378382
384
386
TW 388.49BW 374.08CB #15
RIM=382.89
12" CPEP IE IN=378.67 (W)
12" CPEP IE OUT=378.67 (E)
15 LF 12" CPEP @ 0.7%
232 LF 12" DI @ 0.5%
NW 1/4 OF THE NW 1/4 AND THE NE 1/4 OF THE NW 1/4 SECTION 9, TOWNSHIP 23 NORTH, RANGE 05 EAST, W.M.
1601 5th Avenue, Suite 1600
Seattle, WA 98101
206.622.5822
www.kpff.com
R
Call 811two business daysbefore you dig
CITY OF
RENTON
IN COMPLIANCE WITH CITY OF RENTON STANDARDS
MAPLE HIGHLANDS
13818 152ND AVE SE
RENTON, WA 98059TED-XX-XXXX07/08/2022
11MAPLE HIGHLANDSLUA22-XXXXXXC22-XXXXXXPR22-XXXXXXC4.0DRAINAGE CONTROL PLAN
5
0
1 INCH = 40 FEET
20'40'80'
APPROXIMATE EARTHWORK QUANTITIES
APPROXIMATE EARTHWORK QUANTITIES WERE ESTIMATED USING A GRID
VOLUME METHOD AND AUTOCAD CIVIL 3D SOFTWARE. THE FOLLOWING
VALUES ARE ESTIMATE PROVIDED TO ILLUSTRATE GENERAL EARTHWORK
EFFORTS BASED ON AVAILABLE EXISTING TOPOGRAPHIC SURVEY AND
FINISHED GRADE DESIGN DATA, AND DOES NOT INCLUDE ESTIMATED
EARTHWORK VOLUMES THAT WOULD BE DISPLACED OR OTHERWISE
OCCUPIED BY STRUCTURE, FOUNDATION, AND PAVEMENT SECTIONS OR
TRENCH BACKFILL:
FILL: 12000 CY
CUT: 2000 CY
NET: 10000 CY (FILL)
THE CONTRACTOR SHALL USE THEIR OWN MEANS AND METHOD TO
ESTIMATE EARTHWORK QUANTITIES.
LEGEND
PROPERTY LINE
ROW LINE
ROAD CENTERLINE
LOT LINE
EASEMENT
WATER LINE
SANITARY SEWER LINE
STORM DRAIN LINE
WATER METER
GATE VALVE
FIRE HYDRANT
WATER BEND WITH THRUST
BLOCKING
CATCH BASIN (TYPE 1)
CATCH BASIN (TYPE 2)
SANITARY SEWER MANHOLE
FLOW DIRECTION
CLEANOUT
Page 34
Appendix B
BMP Details
Page 35
BMP C101: Preserving Natural Vegetation
Purpose
The purpose of preserving natural vegetation is to reduce erosion wherever practicable. Limiting site
disturbance is the single most effective method for reducing erosion. For example, conifers can hold
up to about 50 percent of all rain that falls during a storm. Up to 20-30 percent of this rain may never
reach the ground but is taken up by the tree or evaporates. Another benefit is that the rain held in the
tree can be released slowly to the ground after the storm.
Conditions of Use
Natural vegetation should be preserved on steep slopes, near perennial and intermittent water-
courses or swales, and on building sites in wooded areas.
l As required by local governments.
l Phase construction to preserve natural vegetation on the project site for as long as possible
during the construction period.
Design and Installation Specifications
Natural vegetation can be preserved in natural clumps or as individual trees, shrubs and vines.
The preservation of individual plants is more difficult because heavy equipment is generally used to
remove unwanted vegetation. The points to remember when attempting to save individual plants
are:
l Is the plant worth saving? Consider the location, species, size, age, vigor, and the work
involved. Local governments may also have ordinances to save natural vegetation and trees.
l Fence or clearly mark areas around trees that are to be saved. It is preferable to keep ground
disturbance away from the trees at least as far out as the dripline.
Plants need protection from three kinds of injuries:
l Construction Equipment - This injury can be above or below the ground level. Damage results
from scarring, cutting of roots, and compaction of the soil. Placing a fenced buffer zone around
plants to be saved prior to construction can prevent construction equipment injuries.
l Grade Changes - Changing the natural ground level will alter grades, which affects the plant's
ability to obtain the necessary air, water, and minerals. Minor fills usually do not cause prob-
lems although sensitivity between species does vary and should be checked. Trees can typ-
ically tolerate fill of 6 inches or less. For shrubs and other plants, the fill should be less.
When there are major changes in grade, it may become necessary to supply air to the roots of
plants. This can be done by placing a layer of gravel and a tile system over the roots before the
fill is made. The tile system should be laid out on the original grade leading from a dry well
2019Stormwater ManagementManualfor WesternWashington
VolumeII- Chapter 3- Page271
around the tree trunk. The system should then be covered with small stones to allow air to cir-
culate over the root area.
Lowering the natural ground level can seriously damage trees and shrubs. The highest per-
centage of the plant roots are in the upper 12 inches of the soil and cuts of only 2-3 inches can
cause serious injury. To protect the roots it may be necessary to terrace the immediate area
around the plants to be saved. If roots are exposed, construction of retaining walls may be
needed to keep the soil in place. Plants can also be preserved by leaving them on an undis-
turbed, gently sloping mound. To increase the chances for survival, it is best to limit grade
changes and other soil disturbances to areas outside the dripline of the plant.
l Excavations - Protect trees and other plants when excavating for drainfields, power, water,
and sewer lines. Where possible, the trenches should be routed around trees and large
shrubs. When this is not possible, it is best to tunnel under them. This can be done with hand
tools or with power augers. If it is not possible to route the trench around plants to be saved,
then the following should be observed:
o Cut as few roots as possible. When you have to cut, cut clean. Paint cut root ends with a
wood dressing like asphalt base paint if roots will be exposed for more than 24-hours.
o Backfill the trench as soon as possible.
o Tunnel beneath root systems as close to the center of the main trunk to preserve most
of the important feeder roots.
Some problems that can be encountered with a few specific trees are:
l Maple, Dogwood, Red alder, Western hemlock, Western red cedar, and Douglas fir do not
readily adjust to changes in environment and special care should be taken to protect these
trees.
l The windthrow hazard of Pacific silver fir and madrona is high, while that of Western hemlock
is moderate. The danger of windthrow increases where dense stands have been thinned.
Other species (unless they are on shallow, wet soils less than 20 inches deep) have a low
windthrow hazard.
l Cottonwoods, maples, and willows have water-seeking roots. These can cause trouble in
sewer lines and infiltration fields. On the other hand, they thrive in high moisture conditions
that other trees would not.
l Thinning operations in pure or mixed stands of Grand fir, Pacific silver fir, Noble fir, Sitka
spruce, Western red cedar, Western hemlock, Pacific dogwood, and Red alder can cause ser-
ious disease problems. Disease can become established through damaged limbs, trunks,
roots, and freshly cut stumps. Diseased and weakened trees are also susceptible to insect
attack.
Maintenance Standards
Inspect flagged and/or fenced areas regularly to make sure flagging or fencing has not been
removed or damaged. If the flagging or fencing has been damaged or visibility reduced, it shall be
repaired or replaced immediately and visibility restored.
2019Stormwater ManagementManualfor WesternWashington
VolumeII- Chapter 3- Page272
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.
2019Stormwater ManagementManualfor WesternWashington
VolumeII- Chapter 3- Page274
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
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 275
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
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 276
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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BMP C107: Construction Road / Parking Area
Stabilization
Purpose
Stabilizing roads, parking areas, and other on-site vehicle transportation routes immediately after
grading reduces erosion caused by construction traffic or stormwater runoff.
Conditions of Use
Roads and parking areas shall be stabilized wherever they are constructed, whether permanent or
temporary, for use by construction traffic.
BMP C103: High-Visibility Fence shall be installed, if necessary, to limit the access of vehicles to only
those roads and parking areas that are stabilized.
Design and Installation Specifications
l On areas that will receive asphalt as part of the project, install the first lift as soon as possible.
l A 6-inch depth of 2- to 4-inch crushed rock, gravel base, or crushed surfacing base course
shall be applied immediately after grading or utility installation. A 4-inch course of asphalt
treated base (ATB) may also be used, or the road/parking area may be paved. It may also be
possible to use cement or calcium chloride for soil stabilization. If cement or cement kiln dust is
used for roadbase stabilization, pH monitoring and BMP C252: Treating and Disposing of
High pH Water is necessary to evaluate and minimize the effects on stormwater. If the area
will not be used for permanent roads, parking areas, or structures, a 6-inch depth of hog fuel
may also be used, but this is likely to require more maintenance. Whenever possible, con-
struction roads and parking areas shall be placed on a firm, compacted subgrade.
l Temporary road gradients shall not exceed 15 percent. Roadways shall be carefully graded to
drain. Drainage ditches shall be provided on each side of the roadway in the case of a
crowned section, or on one side in the case of a super-elevated section. Drainage ditches
shall be directed to a sediment control BMP.
l Rather than relying on ditches, it may also be possible to grade the road so that runoff sheet-
flows into a heavily vegetated area with a well-developed topsoil. Landscaped areas are not
adequate. If this area has at least 50 feet of vegetation that water can flow through, then it is
generally preferable to use the vegetation to treat runoff, rather than a sediment pond or trap.
The 50 feet shall not include wetlands or their buffers. If runoff is allowed to sheetflow through
adjacent vegetated areas, it is vital to design the roadways and parking areas so that no con-
centrated runoff is created.
l Storm drain inlets shall be protected to prevent sediment-laden water entering the drainage
system (see BMP C220: Inlet Protection).
Maintenance Standards
Inspect stabilized areas regularly, especially after large storm events.
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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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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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BMP C160: Certified Erosion and Sediment Control
Lead
Purpose
The project proponent designates at least one person as the responsible representative in charge of
erosion and sediment control (ESC), and water quality protection. The designated person shall be
responsible for ensuring compliance with all local, state, and federal erosion and sediment control
and water quality requirements. Construction sites one acre or larger that discharge to waters of the
State must designate a Certified Erosion and Sediment Control Lead (CESCL) as the responsible
representative.
Conditions of Use
A CESCL shall be made available on projects one acre or larger that discharge stormwater to sur-
face waters of the state. Sites less than one acre may have a person without CESCL certification
conduct inspections.
The CESCL shall:
l Have a current certificate proving attendance in an erosion and sediment control training
course that meets the minimum ESC training and certification requirements established by
Ecology.
Ecology has provided the minimum requirements for CESCL course training, as well as a list
of ESC training and certification providers at:
https://ecology.wa.gov/Regulations-Permits/Permits-certifications/Certified-erosion-sed-
iment-control
OR
l Be a Certified Professional in Erosion and Sediment Control (CPESC). For additional inform-
ation go to:
http://www.envirocertintl.org/cpesc/
Specifications
l CESCL certification shall remain valid for three years.
l The CESCL shall have authority to act on behalf of the contractor or project proponent and
shall be available, or on-call, 24 hours per day throughout the period of construction.
l The Construction SWPPP shall include the name, telephone number, fax number, and
address of the designated CESCL. See II-2 Construction Stormwater Pollution Prevention
Plans (Construction SWPPPs).
l A CESCL may provide inspection and compliance services for multiple construction projects
in the same geographic region, but must be on site whenever earthwork activities are
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occurring that could generate release of turbid water.
l Duties and responsibilities of the CESCL shall include, but are not limited to the following:
o Maintaining a permit file on site at all times which includes the Construction SWPPP
and any associated permits and plans.
o Directing BMP installation, inspection, maintenance, modification, and removal.
o Updating all project drawings and the Construction SWPPP with changes made.
o Completing any sampling requirements including reporting results using electronic Dis-
charge Monitoring Reports (WebDMR).
o Facilitate, participate in, and take corrective actions resulting from inspections per-
formed by outside agencies or the owner.
o Keeping daily logs, and inspection reports. Inspection reports should include:
n Inspection date/time.
n Weather information; general conditions during inspection and approximate
amount of precipitation since the last inspection.
n Visual monitoring results, including a description of discharged stormwater. The
presence of suspended sediment, turbid water, discoloration, and oil sheen shall
be noted, as applicable.
n Any water quality monitoring performed during inspection.
n General comments and notes, including a brief description of any BMP repairs,
maintenance or installations made as a result of the inspection.
n A summary or list of all BMPs implemented, including observations of all
erosion/sediment control structures or practices. The following shall be noted:
1. Locations of BMPs inspected.
2. Locations of BMPs that need maintenance.
3. Locations of BMPs that failed to operate as designed or intended.
4. Locations of where additional or different BMPs are required.
BMP C162: Scheduling
Purpose
Sequencing a construction project reduces the amount and duration of soil exposed to erosion by
wind, rain, runoff, and vehicle tracking.
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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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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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Volume II -Chapter 3 -Page 372
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,
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 373
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.
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 374
Figure II-3.23: Silt Fence Installation by Slicing Method
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 375
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
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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
Maintenance Standards
l Monitor the spray field on a daily basis to ensure that over saturation of any portion of the field
doesn’t occur at any time. The presence of standing puddles of water or creation of con-
centrated flows visually signify that over saturation of the field has occurred.
l Monitor the vegetated spray field all the way down to the nearest surface water, or farthest
spray area, to ensure that the water has not caused overland or concentrated flows, and has
not created erosion around the spray nozzle(s).
l Do not exceed water quality standards for turbidity.
l Ecology recommends that a separate inspection log be developed, maintained and kept with
the existing site logbook to aid the operator conducting inspections. This separate “Field Filtra-
tion Logbook” can also aid in demonstrating compliance with permit conditions.
l Inspect the spray nozzles daily, at a minimum, for leaks and plugging from sediment particles.
l If erosion, concentrated flows, or over saturation of the field occurs, rotate the use of branches
or spray heads or move the branches to a new field location.
l Check all branches and the manifold for unintended leaks.
BMP C240: Sediment Trap
Purpose
A sediment trap is a small temporary ponding area with a gravel outlet used to collect and store sed-
iment from sites during construction. Sediment traps, along with other perimeter controls, shall be
installed before any land disturbance takes place in the drainage area.
Conditions of Use
l Sediment traps are intended for use on sites where the tributary drainage area is less than 3
acres, with no unusual drainage features, and a projected build-out time of six months or less.
The sediment trap is a temporary measure (with a design life of approximately 6 months) and
shall be maintained until the tributary area is permanently protected against erosion by veget-
ation and/or structures.
l Sediment traps are only effective in removing sediment down to about the medium silt size
fraction. Runoff with sediment of finer grades (fine silt and clay) will pass through untreated,
emphasizing the need to control erosion to the maximum extent first.
l Projects that are constructing permanent Flow Control BMPs, or Runoff Treatment BMPs
that use ponding for treatment, may use the rough-graded or final-graded permanent BMP
footprint for the temporary sediment trap. When permanent BMP footprints are used as tem-
porary sediment traps, the surface area requirement of the sediment trap must be met. If the
surface area requirement of the sediment trap is larger than the surface area of the per-
manent BMP, then the sediment trap shall be enlarged beyond the permanent BMP footprint
to comply with the surface area requirement.
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Volume II -Chapter 3 -Page 383
l A floating pond skimmer may be used for the sediment trap outlet if approved by the Local Per-
mitting Authority.
l Sediment traps may not be feasible on utility projects due to the limited work space or the
short-term nature of the work. Portable tanks may be used in place of sediment traps for utility
projects.
Design and Installation Specifications
l See Figure II-3.26: Cross Section of Sediment Trap and Figure II-3.27: Sediment Trap Outlet
for details.
l To determine the sediment trap geometry, first calculate the design surface area (SA) of the
trap, measured at the invert of the weir. Use the following equation:
SA = FS(Q2/Vs)
where
Q2 =
o Option 1 - Single Event Hydrograph Method:
Q2 = Peak volumetric flow rate calculated using a 10-minute time step from a Type 1A,
2-year, 24-hour frequency storm for the developed condition. The 10-year peak volu-
metric flow rate shall be used if the project size, expected timing and duration of con-
struction, or downstream conditions warrant a higher level of protection.
o Option 2 - For construction sites that are less than 1 acre, the Rational Method may be
used to determine Q2.
Vs = The settling velocity of the soil particle of interest. The 0.02 mm (medium silt) particle with
an assumed density of 2.65 g/cm3 has been selected as the particle of interest and has a set-
tling velocity (Vs) of 0.00096 ft/sec.
FS = A safety factor of 2 to account for non-ideal settling.
Therefore, the equation for computing sediment trap surface area becomes:
SA = 2 x Q2/0.00096
or
2080 square feet per cfs of inflow
l Sediment trap depth shall be 3.5 feet minimum from the bottom of the trap to the top of the
overflow weir.
l To aid in determining sediment depth, all sediment traps shall have a staff gauge with a prom-
inent mark 1-foot above the bottom of the trap.
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Volume II -Chapter 3 -Page 384
l Design the discharge from the sediment trap by using the guidance for discharge from tem-
porary sediment ponds in BMP C241: Sediment Pond (Temporary).
Maintenance Standards
l Sediment shall be removed from the trap when it reaches 1-foot in depth.
l Any damage to the trap embankments or slopes shall be repaired.
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 385
Figure II-3.26: Cross Section of Sediment Trap
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 386
Figure II-3.27: Sediment Trap Outlet
2019 Stormwater Management Manual for Western Washington
Volume II -Chapter 3 -Page 387
Page 36
Appendix C
Standard Site Inspection Form
Page 37
Construction Stormwater Site Inspection Form
Page 1
Project Name Chambers Bagnell
Plat
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:
Page 38
Appendix D
State of Washington Construction Stormwater General Permit (CSWGP)
Page 39
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
Disturbance 1
Weekly Site
Inspections
Weekly
Sampling w/
Turbidity Meter
Weekly
Sampling w/
Transparency
Tube
Weekly pH
Sampling 2
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 method 3
Required Yes
Sites that disturb 5
acres or more
Required Required Not Required 4 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
Page 40
Appendix E
Engineering Calculations
Page 41
Page 42
Appendix F
303(d) List Waterbodies / TMDL Waterbodies Information
Page 43
Maple Highlands – Conner Homes
Appendix I
Appendix I
Bond Quantity Worksheet
(To Be Provided With Future Submittal)
Maple Highlands – Conner Homes
Appendix J
Appendix J
Operation and Maintenance Manual
Maple Highlands – Conner Homes
Maple Highlands
13818 & 13929 152nd Ave SE
Renton, WA 98059
Stormwater Operations and Maintenance
Manual
July 2022
Maple Highlands – Connor Homes
i
Stormwater Operations and Maintenance
Manual
July 2022
Prepared for:
Owner/Applicant
Conner Homes
12600 SE 38th St
Bellevue, WA 98006
Prepared by:
KPFF Consulting Engineers
Maddy Murphy, Civil Design Engineer
1601 Fifth Avenue, Suite 1600
Seattle, WA 98101
Phone: (206) 622-5822
KPFF Project No. 2100590
Associated Permits:
Land Use Permit
Civil Construction Permit
KPFF Consulting Engineers
ii
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Maple Highlands – Connor Homes
iii
Table of Contents
1. Stormwater Facility Narrative ...................................................................................................................... 1
2. Maintenance Task Description .................................................................................................................... 1
Appendices
Appendix A – Site Plan
Appendix B – BMP Maintenance List
Appendix C – Stormwater Facility Maintenance Activity Log
KPFF Consulting Engineers
iv
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Maple Highlands – Connor Homes
Appendix A
1. Stormwater Facility Narrative
Maple Highlands consists of approximately 4.16 acres of new residential development and approximately
0.45-acres of improvements in the right-of-way. The project site is located at 13818 152nd Avenue Southeast
and 13929 154th Avenue Southeast in Renton, Washington. The project consists of two existing parcels which
will be subdivided into 13 parcels, including a storm tract and dedication for public right-of-way. The project
development includes construction of Southeast 5th Place and 153rd Avenue Southeast streets, 12 single-
family homes, associated frontage improvements, grading, utilities, and stormwater mitigation facilities.
This Operations and Maintenance (O&M) Manual is intended for the project owner once the project is
complete and is intended to satisfy the Drainage Review Plan Specifications in Section 2.3.1.1 of the 2017 City
of Renton Surface Water Manual (RSWM) as adopted with amendments to the 2016 King County Surface
Water Design Manual.
Connor Homes will be the responsible party for maintenance of the on-site storm systems. The contact for
Connor Homes is Aron Golden, who can be reached at (206) 271-6613. The City will take over responsibility of
operating and maintaining the proposed drainage facilities in the right-of-way. Until that time, this O&M manual
will be kept at a location that can be made available to the City for inspection prior to the Certificate of
Occupancy.
The location of each Best Management Practice (BMP), detail drawings for each BMP, descriptions for all
maintenance tasks and the frequency of each task, and a sample maintenance activity log are provided in this
O&M Manual. The stormwater facilities located on-site generally consist of catch basins for collection, storm
drain pipe for conveyance, and storm water quality and detention pond.
If you are unsure whether a problem exists, please contact City of Renton Community and Economic
Development (CED) Department at (425) 430-7294.
2. Maintenance Task Description
MAINTENANCE STANDARDS FOR DRAINAGE FACILITIES
Refer to the attached maintenance requirements for the following:
· Catch basins and area drains
· Conveyance pipes and ditches
· Debris barriers
· Grounds (Landscaping)
· Access road
· Sheet flow BMP
· Soil Amendment BMP
KPFF Consulting Engineers
2
Appendix A
Site Plan
3
BPE 386.4
376376376390
384
386
388
392
394388
38
6
386386386 3863863863
8
6 3861
BPE 388.4
2
BPE 387.4
4
BPE 385.0
12
BPE 386.0
11
BPE 386.1
5
BPE 385.4
6
BPE 386.1
7
BPE 386.4
10
BPE 387.0
9
BPE 386.6
8
BPE 386.3
SE 138TH PL
152ND AVE SE153RD AVE SESE 5TH PL
SE 5TH PL
154TH AVE SEROCKERY
ROCKERY
CIP RETAINING WALL
CB #12
RIM=385.50
12" CPEP IE OUT=382.32 (SE)
CB #11
RIM=385.81
12" DI IE IN=382.18 (NW)
12" DI IE OUT=382.18 (E)CB #5
RIM=384.51
12" DI IE OUT=381.15 (N)
CB#4
RIM=384.32
12" DI IE IN=381.01 (S, W)
12" DI IE OUT=381.01 (E)
CB #1
RIM=383.68
12" DI IE OUT=381.03 (W)CB #2
RIM=383.68
12" DI IE IN=380.91 (W)
12" DI IE OUT=380.91 (SE)
CB #3
RIM=384.53
12" DI IE IN=380.73 (NW)
12" DI IE IN=380.73 (W)
12" DI IE OUT=380.73 (E)
CB #6
RIM=385.28
12" CPEP IE IN=380.55 (W)
12" CPEP IE IN=380.55 (S)
12" CPEP IE OUT=380.55 (E)
CB #7
RIM=385.31
12" CPEP IE OUT=380.79 (N)
CB #8
RIM=386.82
12" CPEP IE IN=379.30 (W)
12" CPEP IE OUT=379.30 (S)
CB #9
RIM=390.91
12" DI IE OUT=388.16 (E)
CB #10
RIM=390.98
12" DI IE IN=388.03 (W)
EX 18" CPEP IE IN =387.47 (N)
EX 18" CPEP IE OUT =387.47 (S)
CONTROL STRUCTURE
RIM=385.25
12" CPEP IE OUT=378.75 (E)
CB #16
RIM=382.64
12" CPEP IE IN=378.52 (W)
12" CPEP IE OUT=378.52 (E)
27 LF 12" CPEP @ 0.5%
28 LF 12" DI @ 0.5%48 LF 12" DI
@ 0.5%
22 LF 8" DI @ 0.5%
40 LF 12" DI @ 0.5%
36 LF 12"
CPEP @ 0.5%
20 LF 12"
CPEP @ 1.0%
150 LF 12"
CPEP @ 1.5%
47 LF 12"
CPEP @ 1.5%
15 LF 12" CPEP @ 0.7%
26 LF 12" CPEP
@ 0.7%
27 LF 12" DI @ 0.5%TW 385.70BW 381.67TW 385.73BW 379.53TW 385.75BW 377.34T
W
3
8
5
.
7
5
B
W
3
7
9
.
5
2
TW
3
8
5
.
4
5
BW
3
8
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0 TW 396.00BW 390.00TW 387.16BW 387.16386TOP OF POND 385.45
BOT OF POND 374.08
INTERIOR SLOPES 3:1
EX CB
RIM=382.40
12" CPEP IE IN=378.34 (W)
EX 4" PVC IE IN=378.99 (NE)
EX 18" CPEP IE IN=378.38 (N)
EX 18" CPEP IE OUT=378.34 (S)
TREE TRACT BOUNDARY
24 LF 12"
CPEP @ 1.5%
CB #14
RIM=386.85
12" CPEP IE IN=378.94
12" CPEP IE OUT=378.94 380
376378382
384
386
TW 388.49BW 374.08CB #15
RIM=382.89
12" CPEP IE IN=378.67 (W)
12" CPEP IE OUT=378.67 (E)
15 LF 12" CPEP @ 0.7%
232 LF 12" DI @ 0.5%
NW 1/4 OF THE NW 1/4 AND THE NE 1/4 OF THE NW 1/4 SECTION 9, TOWNSHIP 23 NORTH, RANGE 05 EAST, W.M.
1601 5th Avenue, Suite 1600
Seattle, WA 98101
206.622.5822
www.kpff.com
R
Call 811two business daysbefore you dig
CITY OF
RENTON
IN COMPLIANCE WITH CITY OF RENTON STANDARDS
MAPLE HIGHLANDS
13818 152ND AVE SE
RENTON, WA 98059TED-XX-XXXX07/08/2022
11MAPLE HIGHLANDSLUA22-XXXXXXC22-XXXXXXPR22-XXXXXXC4.0DRAINAGE CONTROL PLAN
5
0
1 INCH = 40 FEET
20'40'80'
APPROXIMATE EARTHWORK QUANTITIES
APPROXIMATE EARTHWORK QUANTITIES WERE ESTIMATED USING A GRID
VOLUME METHOD AND AUTOCAD CIVIL 3D SOFTWARE. THE FOLLOWING
VALUES ARE ESTIMATE PROVIDED TO ILLUSTRATE GENERAL EARTHWORK
EFFORTS BASED ON AVAILABLE EXISTING TOPOGRAPHIC SURVEY AND
FINISHED GRADE DESIGN DATA, AND DOES NOT INCLUDE ESTIMATED
EARTHWORK VOLUMES THAT WOULD BE DISPLACED OR OTHERWISE
OCCUPIED BY STRUCTURE, FOUNDATION, AND PAVEMENT SECTIONS OR
TRENCH BACKFILL:
FILL: 12000 CY
CUT: 2000 CY
NET: 10000 CY (FILL)
THE CONTRACTOR SHALL USE THEIR OWN MEANS AND METHOD TO
ESTIMATE EARTHWORK QUANTITIES.
LEGEND
PROPERTY LINE
ROW LINE
ROAD CENTERLINE
LOT LINE
EASEMENT
WATER LINE
SANITARY SEWER LINE
STORM DRAIN LINE
WATER METER
GATE VALVE
FIRE HYDRANT
WATER BEND WITH THRUST
BLOCKING
CATCH BASIN (TYPE 1)
CATCH BASIN (TYPE 2)
SANITARY SEWER MANHOLE
FLOW DIRECTION
CLEANOUT
Maple Highlands – Connor Homes
Appendix B
Appendix B
BMP Maintenance List
CITY OF RENTON SURFACE WATER DESIGN MANUAL
2017 City of Renton Surface Water Design Manual 12/12/2016
A-1
APPENDIX A
MAINTENANCE REQUIREMENTS FOR
STORMWATER FACILITIES AND ON-SITE
BMPS
This appendix contains the maintenance requirements for the following typical stormwater flow control
and water quality facilities and on-site BMPs (ctrl/click the title to follow the link):
No. 1 – Detention Ponds
No. 2 – Infiltration Facilities
No. 3 – Detention Tanks and Vaults
No. 4 – Control Structure/Flow Restrictor
No. 5 – Catch Basins and Manholes
No. 6 – Conveyance Pipes and Ditches
No. 7 – Debris Barriers (e.g., trash racks)
No. 8 – Energy Dissipaters
No. 9 – Fencing
No. 10 – Gates/Bollards/Access Barriers
No. 11 – Grounds (landscaping)
No. 12 – Access Roads
No. 13 – Basic Bioswale (grass)
No. 14 – Wet Bioswale
No. 15 – Filter Strip
No. 16 – Wetpond
No. 17 – Wetvault
No. 18 – Stormwater Wetland
No. 19 – Sand Filter Pond
No. 20 – Sand Filter Vault
No. 21 – Proprietary Facility Cartridge Filter Systems
No. 22 – Baffle Oil/Water Separator
No. 23 – Coalescing Plate Oil/Water Separator
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual
A-2
No. 24 – Catch Basin Insert (not allowed in the city for oil control)
No. 25 – Drywell BMP
No. 26 – Gravel Filled Infiltration Trench BMP
No. 27 – Gravel Filled Dispersion Trench BMP
No. 28 – Native Vegetated Surface/Native Vegetated Landscape BMP
No. 29 – Perforated Pipe Connections BMP
No. 30 – Permeable Pavement BMP
No. 31 – Bioretention BMP
No. 32 – RainWater Harvesting BMP
No. 33 – Rock Pad BMP
No. 34 – Sheet Flow BMP
No. 35 – Splash Block BMP
No. 36 – Vegetated Roof BMP
No. 37 – Rain Garden BMP
No. 38 – Soil Amendment BMP
No. 39 – Retained Trees
No. 40 – Filterra System
No. 41 – Compost Amended Vegetated Filter Strip (CAVFS)
No. 42 – Media Filter Drain (MFD)
No. 43 – Compost-Amended Biofiltration Swale
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016
A-3
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 City personnel
or the public.
Noxious and nuisance vegetation removed
according to applicable regulations. No
danger of noxious vegetation where City
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.
Excessive growth of
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 inlet/outlet
pipe
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.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual
A-10
NO. 5 – CATCH BASINS AND MANHOLES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Structure Sediment
accumulation
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.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016
A-11
NO. 5 – CATCH BASINS AND MANHOLES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Inlet/Outlet Pipe
(cont.)
Damaged inlet/outlet
pipe
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
(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
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.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual
A-12
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/root
growth in pipe
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 pipes 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 City personnel
or the public.
Noxious and nuisance vegetation removed
according to applicable regulations. No
danger of noxious vegetation where City
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.
Excessive vegetation
growth
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.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016
A-13
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 pipe or structure
Structure which bars attached to is
damaged – pipe is loose or cracked or
concrete structure is cracked, broken, or
loose.
Structure barrier attached to is sound.
Bars Incorrect 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.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016
A-15
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.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual
A-16
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
bollards
Bollard broken, missing, does not fit into
support hole or hinge broken or missing.
No access for motorized vehicles to get
into facility.
Bollards do 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 Boulders not located to prevent motorized
vehicle access.
No access for motorized vehicles to get
into facility.
Evidence of vehicles
circumventing
boulders
Motorized vehicles going around or
between boulders.
No access for motorized vehicles to get
into facility.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016
A-17
NO. 11 – GROUNDS (LANDSCAPING)
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 City personnel
or the public.
Noxious and nuisance vegetation removed
according to applicable regulations. No
danger of noxious vegetation where City
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.
Excessive growth of
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 tree identified 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 tree or
shrub identified
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.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual
A-18
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
blocks/grids
Access surface compacted because of
broken on missing modular block.
Access road surface restored so road
infiltrates.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016
A-43
NO. 32 – RAINWATER HARVESTING BMP
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Preventive Insufficient 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. 1).
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
Filter is partially or fully plugged preventing
water from getting in to the storage unit.
Filter is allowing collection water into
storage unit.
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 Insufficient 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 growth 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.
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.
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
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.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016
A-47
NO. 38 – SOIL AMENDMENT BMP
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Soil Media Unhealthy vegetation Vegetation not fully covering ground
surface or vegetation health is poor.
Yellowing: possible Nitrogen (N)
deficiency. Poor growth: possible
Phosphorous (P) deficiency. Poor
flowering, spotting or curled leaves, or
weak roots or stems: possible Potassium
(K) deficiency.
Plants are healthy and appropriate for site
conditions
Inadequate soil
nutrients and
structure
In the fall, return leaf fall and shredded
woody materials from the landscape to the
site when possible
Soil providing plant nutrients and structure
Excessive vegetation
growth
Grass becomes excessively tall (greater
than 10 inches); nuisance weeds and other
vegetation start to take over.
Healthy turf- “grasscycle” (mulch-mow or
leave the clippings) to build turf health
Weeds Preventive maintenance Avoid use of pesticides (bug and weed
killers), like “weed & feed,” which damage
the soil
Fertilizer needed Where fertilization is needed (mainly turf
and annual flower beds), a moderate
fertilization program should be used which
relies on compost, natural fertilizers or
slow-release synthetic balanced fertilizers
Integrated Pest Management (IPM)
protocols for fertilization followed
Bare spots Bare spots on soil No bare spots, area covered with
vegetation or mulch mixed into the
underlying soil.
Compaction Poor infiltration due to soil compaction
• To remediate compaction, aerate
soil, till to at least 8-inch depth, or
further amend soil with compost and
re-till
• If areas are turf, aerate compacted
areas and top dress them with 1/4 to
1/2 inch of compost to renovate them
• If drainage is still slow, consider
investigating alternative causes (e.g.,
high wet season groundwater levels,
low permeability soils)
• Also consider site use and protection
from compacting activities
No soil compaction
Poor infiltration Soils become waterlogged, do not appear
to be infiltrating.
Facility infiltrating properly
Erosion/Scouring Erosion Areas of potential erosion are visible Causes of erosion (e.g., concentrate flow
entering area, channelization of runoff)
identified and damaged area stabilized
(regrade, rock, vegetation, erosion control
matting).For deep channels or cuts (over 3
inches in ponding depth), temporary
erosion control measures in place until
permanent repairs can be made
Grass/Vegetation Unhealthy vegetation Less than 75% of planted vegetation is
healthy with a generally good appearance.
Healthy vegetation. Unhealthy plants
removed/replaced. Appropriate vegetation
planted in terms of exposure, soil and soil
moisture.
Noxious Weeds Noxious weeds Listed noxious vegetation is present (refer
to current County noxious weed list).
No noxious weeds present.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual
A-48
NO. 39 – RETAINED TREES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Tree Dead or declining Dead, damaged, or declining Tree replaced per planting plan or
acceptable substitute
NO. 40 – FILTERRA SYSTEM
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
In addition to the specific maintenance criteria provided below, all manufacturer’s requirements shall be followed.
Facility – General
Requirements
Life cycle Once per year, except mulch and trash
removal twice per year
Facility is re-inspected and any needed
maintenance performed
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 Excessive sediment or
trash accumulation
Accumulated sediments or trash impair free
flow of water into system
Inlet should be free of obstructions allowing
free distributed flow of water into system
Mulch Cover Trash and floatable
debris accumulation
Excessive trash and/or debris accumulation Minimal trash or other debris on mulch
cover. Mulch cover raked level.
“Ponding” of water on
mulch cover
“Ponding” in unit could be indicative of
clogging due to excessive fine sediment
accumulation or spill of petroleum oils
Stormwater should drain freely and evenly
through mulch cover
Proprietary Filter
Media/
Vegetation Substrate
“Ponding” of water on
mulch cover after
mulch cover has been
maintained
Excessive fine sediment passes the mulch
cover and clogs the filter media/vegetative
substrate
Stormwater should drain freely and evenly
through mulch cover. Replace substrate and
vegetation when needed
Vegetation Plants not growing or in
poor condition
Soil/mulch too wet, evidence of spill,
incorrect plant selection, pest infestation,
and/or vandalism to plants
Plants should be healthy and pest free
Media/mulch too dry Irrigation is required
Plants absent Plants absent Appropriate plants are present
Excessive plant growth Excessive plant growth inhibits facility
function or becomes a hazard for pedestrian
and vehicular circulation and safety
Pruning and/or thinning vegetation maintains
proper plant density. Appropriate plants are
present.
Structure Structure has visible
cracks
Cracks wider than ½ inch
Evidence of soil particles entering the
structure through the cracks
Structure is sealed and structurally sound
Maple Highlands – Connor Homes
Appendix C
Appendix C
Stormwater Facility Maintenance Activity Log
STORMWATER FACILITY MAINTENANCE ACTIVITY LOG
13818 & 13929 152nd Ave SE
Renton, WA 98059
Name of Inspector(s): ____________________________________________________________
Inspection Date: ________________________________________________________________
Inspection Time: ________________________________________________________________
Approximate Date/Time of Last Rainfall:______________________________________________
Type of Stormwater Facility: _______________________________________________________
Location of Facility on Site (in relation to building or other permanent structures):
Water levels and observations (oil sheen, smell, turbidity, etc.):
Sediment accumulation & record of sediment removal:
Condition of vegetation (height, survival rates, invasive species present, etc.) and record of
replacement and management (mowing, weeding, etc.):
Condition of physical properties such as inlets, outlets, piping, fences, irrigation facilities, and side
slopes. Record damaged items and replacement activities:
Presence of insects or vectors. Record control activities:
Identify safety hazards present. Record resolution activities:
Notes:
Maple Highlands – Conner Homes
Appendix K
Appendix K
Geotechnical Report
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone 425.415.0551 ♦ Fax 425.415.0311
www.riley-group.com
GEOTECHNICAL ENGINEERING REPORT
PREPARED BY:
THE RILEY GROUP, INC.
17522 BOTHELL WAY NORTHEAST
BOTHELL, WASHINGTON 98011
PREPARED FOR:
CONNER HOMES
12600 SOUTHEAST 28TH STREET, SUITE 250
BELLEVUE, WASHINGTON 98006
RGI PROJECT NO. 2021-316-1
CHAMBERS-BAGNELL PROPERTY DEVELOPMENT
13818 152ND AVENUE SOUTHEAST & 13929 154TH AVENUE SOUTHEAST
RENTON, WASHINGTON
JUNE 14, 2021
Geotechnical Engineering Report i June 14, 2021
Chambers-Bagnell Property Development, Renton, Washington RGI Project No. 2021-316-1
TABLE OF CONTENTS
1.0 INTRODUCTION ............................................................................................................................... 1
2.0 PROJECT DESCRIPTION ............................................................................................................... 1
3.0 FIELD EXPLORATION AND LABORATORY TESTING .......................................................... 1
3.1 FIELD EXPLORATION ................................................................................................................................... 1
3.2 LABORATORY TESTING ................................................................................................................................ 2
4.0 SITE CONDITIONS ........................................................................................................................... 2
4.1 SURFACE .................................................................................................................................................. 2
4.2 GEOLOGY ................................................................................................................................................. 2
4.3 SOILS ....................................................................................................................................................... 2
4.4 GROUNDWATER ........................................................................................................................................ 3
4.5 SEISMIC CONSIDERATIONS ........................................................................................................................... 3
4.6 GEOLOGIC HAZARD AREAS .......................................................................................................................... 4
5.0 DISCUSSION AND RECOMMENDATIONS ................................................................................. 4
5.1 GEOTECHNICAL CONSIDERATIONS ................................................................................................................. 4
5.2 EARTHWORK ............................................................................................................................................. 4
5.2.1 Erosion and Sediment Control ..................................................................................................... 4
5.2.2 Stripping and Subgrade Preparation ............................................................................................ 5
5.2.3 Excavations................................................................................................................................... 6
5.2.4 Structural Fill ................................................................................................................................ 6
5.2.5 Cut and Fill Slopes ........................................................................................................................ 8
5.2.6 Wet Weather Construction Considerations ................................................................................. 8
5.3 FOUNDATIONS .......................................................................................................................................... 9
5.4 RETAINING WALLS ................................................................................................................................... 10
5.5 SLAB-ON-GRADE CONSTRUCTION ............................................................................................................... 10
5.6 DRAINAGE .............................................................................................................................................. 11
5.6.1 Surface ....................................................................................................................................... 11
5.6.2 Subsurface .................................................................................................................................. 11
5.6.3 Infiltration .................................................................................................................................. 11
5.7 UTILITIES ................................................................................................................................................ 11
6.0 ADDITIONAL SERVICES .............................................................................................................. 12
7.0 LIMITATIONS ................................................................................................................................. 12
LIST OF FIGURES AND APPENDICES
Figure 1 ..................................................................................................................... Site Vicinity Map
Figure 2 ............................................................................................... Geotechnical Exploration Plan
Figure 3 ............................................................................................... Retaining Wall Drainage Detail
Figure 4 ....................................................................................................Typical Footing Drain Detail
Appendix A .......................................................................... Field Exploration and Laboratory Testing
Geotechnical Engineering Report ii June 14, 2021
Chambers-Bagnell Property Development, Renton, Washington RGI Project No. 2021-316-1
Executive Summary
This Executive Summary should be used in conjunction with the entire Geotechnical
Engineering Report (GER) for design and/or construction purposes. It should be recognized
that specific details were not included or fully developed in this section, and the GER must
be read in its entirety for a comprehensive understanding of the items contained herein.
Section 7.0 should be read for an understanding of limitations.
RGI’s geotechnical scope of work included the advancement of 5 test pits to approximate
depths of 4 to 10 feet below existing site grades.
Based on the information obtained from our subsurface exploration, the site is suitable for
development of the proposed project. The following geotechnical considerations were
identified:
Soil Conditions: The soils encountered during field exploration include loose to medium
dense sand with some silt and silty sand with some gravel over dense to very dense silty
sand with varying amounts of gravel glacial till.
Groundwater: Light to moderate groundwater seepage was encountered at Test Pit TP-1
at a depth of 7.5 feet.
Foundations: Foundations for the proposed residence may be supported on conventional
spread footings bearing on medium dense to dense native soil or structural fill.
Slab-on-grade: Slab-on-grade floors and slabs for the proposed residence can be
supported on medium dense to dense native soil or structural fill.
Geotechnical Engineering Report 1 June 14, 2021
Chambers-Bagnell Property Development, Renton, Washington RGI Project No. 2021-316-1
1.0 Introduction
This Geotechnical Engineering Report (GER) presents the results of the geotechnical
engineering services provided for the Chambers-Bagnell Property Development in Renton,
Washington. The purpose of this evaluation is to assess subsurface conditions and provide
geotechnical recommendations for the construction of a 12-lot residential development.
Our scope of services included field explorations, laboratory testing, engineering analyses,
and preparation of this GER.
The recommendations in the following sections of this GER are based upon our current
understanding of the proposed site development as outlined below. If actual features vary
or changes are made, RGI should review them in order to modify our recommendations as
required. In addition, RGI requests to review the site grading plan, final design drawings
and specifications when available to verify that our project understanding is correct and
that our recommendations have been properly interpreted and incorporated into the
project design and construction.
2.0 Project description
The project site is located at 13818 152nd Avenue Southeast & 13929 154th Avenue
Southeast in Renton, Washington. The approximate location of the site is shown on Figure
1.
The site is currently occupied by two single family residences and several outbuildings. RGI
understands that the existing structures will be demolished and a 12-lot residential
development with associated utilities, paved access roads, and stormwater facilities will be
constructed at the site.
At the time of preparing this GER, residence structural plans were not available for our
review. Based on our experience with similar construction, RGI anticipates that the
proposed residences will be supported on perimeter walls with bearing loads of two to six
kips per linear foot, and a series of columns with a maximum load up to 30 kips. Slab-on-
grade floor loading of 150 pounds per square foot (psf) are expected.
3.0 Field Exploration and Laboratory Testing
3.1 FIELD EXPLORATION
On May 18, 2021, RGI observed the excavation of 5 test pits. The approximate exploration
locations are shown on Figure 2.
Field logs of each exploration were prepared by the geologist that continuously observed
during the excavation. These logs included visual classifications of the materials
encountered during excavation as well as our interpretation of the subsurface conditions
Geotechnical Engineering Report 2 June 14, 2021
Chambers-Bagnell Property Development, Renton, Washington RGI Project No. 2021-316-1
between samples. The test pit logs included in Appendix A represent an interpretation of
the field logs and include modifications based on laboratory observation and analysis of
the samples.
3.2 LABORATORY TESTING
During the field exploration, a representative portion of each recovered sample was sealed
in containers and transported to our laboratory for further visual and laboratory
examination. Selected samples retrieved from the test pits were tested for moisture
content and grain size analysis to aid in soil classification and provide input for the
recommendations provided in this GER. The results and descriptions of the laboratory tests
are enclosed in Appendix A.
4.0 Site Conditions
4.1 SURFACE
The subject site is comprised of two parcels totaling approximately 4.16 acres in size. The
site is bound to the north, and south by single family residences, to the east by an
undeveloped pasture and 154th Avenue Southeast, and to the west by a single family
residence and 152nd Avenue Southeast.
The existing site is occupied by two single family residences and several outbuildings. The
site slopes generally southwest with a total of approximately 14 feet of elevation change
across the property. The site is vegetated primarily with grass, with small- to large-diameter
decorative shrubs and trees along the property perimeter and around the residences.
4.2 GEOLOGY
Review of the Geologic Map of the Renton Quadrangle, King Country, Washington (1965),
by Mullineaux, D.R. indicates that the soil through most of the site is mapped as recessional
stratified drift (Qpa), which is sandy and gravelly outwash deposited during glacial
recession. The northeastern portion of the site is mapped as ground moraine deposits (Qgt)
which is a compact mixture of sand, silt, clay, and gravel deposited by glacial ice. The soils
encountered at the site generally match the descriptions for ground moraine deposits
(glacial till), with minor recessional deposits observed in the southern portion of the
property.
4.3 SOILS
The soils encountered during field exploration include loose to medium dense sand with
some silt and silty sand with some gravel over dense to very dense silty sand with varying
amounts of gravel glacial till.
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Chambers-Bagnell Property Development, Renton, Washington RGI Project No. 2021-316-1
More detailed descriptions of the subsurface conditions encountered are presented in the
test pits included in Appendix A. Sieve analysis was performed on two selected soil samples.
Grain size distribution curves are included in Appendix A.
4.4 GROUNDWATER
Light to moderate groundwater seepage was encountered at Test Pit TP-1 at a depth of 7.5
feet.
It should be recognized that fluctuations of the groundwater table will occur due to
seasonal variations in the amount of rainfall, runoff, and other factors not evident at the
time the explorations were performed. In addition, perched water can develop within
seams and layers contained in fill soils or higher permeability soils overlying less permeable
soils following periods of heavy or prolonged precipitation. Therefore, groundwater levels
during construction or at other times in the future may be higher or lower than the levels
indicated on the logs. Groundwater level fluctuations should be considered when
developing the design and construction plans for the project.
4.5 SEISMIC CONSIDERATIONS
Based on the International Building Code (IBC), RGI recommends the follow seismic
parameters for design.
Table 1 IBC
Parameter 2018 Value
Site Soil Class1 C2
Site Latitude 47.4783
Site Longitude -122.1364
Short Period Spectral Response Acceleration, SS (g) 1.372
1-Second Period Spectral Response Acceleration, S1 (g) 0.469
Adjusted Short Period Spectral Response Acceleration, SMS (g) 1.646
Adjusted 1-Sec Period Spectral Response Acceleration, SM1 (g) 0.703
Numeric seismic design value at 0.2 second; SDS(g) 1.097
Numeric seismic design value at 1.0 second; SD1(g) 0.469
1. Note: In general accordance with Chapter 20 of ASCE 7-16. The Site Class is based on the average characteristics of the upper 100 feet
of the subsurface profile.
2. Note: ASCE 7-16 require a site soil profile determination extending to a depth of 100 feet for seismic site classification. The current
scope of our services does not include the required 100 foot soil profile determination. Test pits extended to a maximum depth of 10
feet, and this seismic site class definition considers that similar soil continues below the maximum depth of the subsurface exploration.
Additional exploration to deeper depths would be required to confirm the conditions below the current depth of exploration.
Geotechnical Engineering Report 4 June 14, 2021
Chambers-Bagnell Property Development, Renton, Washington RGI Project No. 2021-316-1
Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength
due to an increase in water pressure induced by vibrations from a seismic event.
Liquefaction mainly affects geologically recent deposits of fine-grained sands that are
below the groundwater table. Soils of this nature derive their strength from intergranular
friction. The generated water pressure or pore pressure essentially separates the soil grains
and eliminates this intergranular friction, thus reducing or eliminating the soil’s strength.
RGI reviewed the results of the field and laboratory testing and assessed the potential for
liquefaction of the site’s soil during an earthquake. Since the site is underlain by glacial till,
RGI considers that the possibility of liquefaction during an earthquake is minimal.
4.6 GEOLOGIC HAZARD AREAS
Regulated geologically hazardous areas include erosion, landslide, earthquake, or other
geological hazards. Based on the definition in the Renton Municipal Code, the site does not
contain geologically hazardous areas.
5.0 Discussion and Recommendations
5.1 GEOTECHNICAL CONSIDERATIONS
Based on our study, the site is suitable for the proposed construction from a geotechnical
standpoint. Foundations for the proposed residences can be supported on conventional
spread footings bearing on competent native soil or structural fill. Slab-on-grade floors can
be similarly supported.
Detailed recommendations regarding the above issues and other geotechnical design
considerations are provided in the following sections. These recommendations should be
incorporated into the final design drawings and construction specifications.
5.2 EARTHWORK
The earthwork is expected to include grading the site to provide lot and roadway grades.
Installing underground utilities and preparing road and sidewalk subgrades. The residence
construction is expected to include excavating and backfilling the residence foundations
and preparing slab subgrades.
5.2.1 EROSION AND SEDIMENT CONTROL
Potential sources or causes of erosion and sedimentation depend on construction
methods, slope length and gradient, amount of soil exposed and/or disturbed, soil type,
construction sequencing and weather. The impacts on erosion-prone areas can be reduced
by implementing an erosion and sedimentation control plan. The plan should be designed
in accordance with applicable city and/or county standards.
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Chambers-Bagnell Property Development, Renton, Washington RGI Project No. 2021-316-1
RGI recommends the following erosion control Best Management Practices (BMPs):
Scheduling site preparation and grading for the drier summer and early fall months
and undertaking activities that expose soil during periods of little or no rainfall
Retaining existing vegetation whenever feasible
Establishing a quarry spall construction entrance
Installing siltation control fencing or anchored straw or coir wattles on the downhill
side of work areas
Covering soil stockpiles with anchored plastic sheeting
Revegetating or mulching exposed soils with a minimum 3-inch thickness of straw
if surfaces will be left undisturbed for more than one day during wet weather or
one week in dry weather
Directing runoff away from exposed soils and slopes
Minimizing the length and steepness of slopes with exposed soils and cover
excavation surfaces with anchored plastic sheeting
Decreasing runoff velocities with check dams, straw bales or coir wattles
Confining sediment to the project site
Inspecting and maintaining erosion and sediment control measures frequently (The
contractor should be aware that inspection and maintenance of erosion control
BMPs is critical toward their satisfactory performance. Repair and/or replacement
of dysfunctional erosion control elements should be anticipated.)
Permanent erosion protection should be provided by reestablishing vegetation using
hydroseeding and/or landscape planting. Until the permanent erosion protection is
established, site monitoring should be performed by qualified personnel to evaluate the
effectiveness of the erosion control measures. Provisions for modifications to the erosion
control system based on monitoring observations should be included in the erosion and
sedimentation control plan.
5.2.2 STRIPPING AND SUBGRADE PREPARATION
Stripping efforts should include removal of pavements, vegetation, organic materials, and
deleterious debris from areas slated for residences, pavement, and utility construction. The
test pits location encountered zero inches of asphalt concrete and zero inches of crushed
rock base. Site did not contain landscape islands. The test pits encountered nine to eleven
inches of topsoil and rootmass. Deeper areas of stripping may be required in heavily
vegetated areas of the site.
Subgrade soils that become disturbed due to elevated moisture conditions should be
overexcavated to reveal firm, non-yielding, non-organic soils and backfilled with
compacted structural fill. In order to maximize utilization of site soils as structural fill, RGI
recommends that the earthwork portion of this project be completed during extended
periods of warm and dry weather if possible. If earthwork is completed during the wet
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Chambers-Bagnell Property Development, Renton, Washington RGI Project No. 2021-316-1
season (typically November through May) it will be necessary to take extra precautionary
measures to protect subgrade soils. Wet season earthwork will require additional
mitigative measures beyond that which would be expected during the drier summer and
fall months.
5.2.3 EXCAVATIONS
All temporary cut slopes associated with the site and utility excavations should be
adequately inclined to prevent sloughing and collapse. The site soils consist of dense to
very dense silty sand with varying amounts of gravel.
Accordingly, for excavations more than 4 feet but less than 20 feet in depth, the temporary
side slopes should be laid back with a minimum slope inclination of 1H:1V
(Horizontal:Vertical). If there is insufficient room to complete the excavations in this
manner, or excavations greater than 20 feet in depth are planned, using temporary shoring
to support the excavations should be considered. For open cuts at the site, RGI
recommends:
No traffic, construction equipment, stockpiles or building supplies are allowed at
the top of cut slopes within a distance of at least five feet from the top of the cut
Exposed soil along the slope is protected from surface erosion using waterproof
tarps and/or plastic sheeting
Construction activities are scheduled so that the length of time the temporary cut
is left open is minimized
Surface water is diverted away from the excavation
The general condition of slopes should be observed periodically by a geotechnical
engineer to confirm adequate stability and erosion control measures
In all cases, however, appropriate inclinations will depend on the actual soil and
groundwater conditions encountered during earthwork. Ultimately, the site contractor
must be responsible for maintaining safe excavation slopes that comply with applicable
OSHA or WISHA guidelines.
5.2.4 STRUCTURAL FILL
RGI recommends fill below the foundation and floor slab, behind retaining walls, and below
pavement and hardscape surfaces be placed in accordance with the following
recommendations for structural fill. The structural fill should be placed after completion of
site preparation procedures as described above.
The suitability of excavated site soils and import soils for compacted structural fill use will
depend on the gradation and moisture content of the soil when it is placed. As the amount
of fines (that portion passing the U.S. No. 200 sieve) increases, soil becomes increasingly
sensitive to small changes in moisture content and adequate compaction becomes more
difficult or impossible to achieve. Soils containing more than about 5 percent fines cannot
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Chambers-Bagnell Property Development, Renton, Washington RGI Project No. 2021-316-1
be consistently compacted to a dense, non-yielding condition when the moisture content
is more than 2 percent above or below optimum. Optimum moisture content is that
moisture that results in the greatest compacted dry density with a specified compactive
effort.
Non-organic site soils are only considered suitable for structural fill provided that their
moisture content is within about two percent of the optimum moisture level as determined
by American Society of Testing and Materials D1557-09 Standard Test Methods for
Laboratory Compaction Characteristics of Soil Using Modified Effort (ASTM D1557).
Excavated site soils may not be suitable for re-use as structural fill depending on the
moisture content and weather conditions at the time of construction. If soils are stockpiled
for future reuse and wet weather is anticipated, the stockpile should be protected with
plastic sheeting that is securely anchored. Even during dry weather, moisture conditioning
(such as, windrowing and drying) of site soils to be reused as structural fill may be required.
The site soils are moisture sensitive and may require moisture conditioning prior to use as
structural fill. If on-site soils are or become unusable, it may become necessary to import
clean, granular soils to complete site work that meet the grading requirements listed in
Table 2 to be used as structural fill.
Table 2 Structural Fill Gradation
U.S. Sieve Size Percent Passing
4 inches 100
No. 4 sieve 22 to 100
No. 200 sieve 0 to 5*
*Based on minus 3/4 inch fraction.
Prior to use, an RGI representative should observe and test all materials imported to the
site for use as structural fill. Structural fill materials should be placed in uniform loose layers
not exceeding 12 inches and compacted as specified in Table 3. The soil’s maximum density
and optimum moisture should be determined by ASTM D1557.
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Chambers-Bagnell Property Development, Renton, Washington RGI Project No. 2021-316-1
Table 3 Structural Fill Compaction ASTM D1557
Location Material Type
Minimum
Compaction
Percentage
Moisture Content
Range
Foundations On-site granular or approved
imported fill soils: 95 +2 -2
Retaining Wall Backfill On-site granular or approved
imported fill soils: 92 +2 -2
Slab-on-grade On-site granular or approved
imported fill soils: 95 +2 -2
General Fill (non-
structural areas)
On-site soils or approved
imported fill soils: 90 +3 -2
Placement and compaction of structural fill should be observed by RGI. A representative
number of in-place density tests should be performed as the fill is being placed to confirm
that the recommended level of compaction is achieved.
5.2.5 CUT AND FILL SLOPES
All permanent cut and fill slopes should be graded with a finished inclination no greater
than 2H:1V. Upon completion of construction, the slope face should be trackwalked,
compacted and vegetated, or provided with other physical means to guard against erosion.
All fill placed for slope construction should meet the structural fill requirements as
described this section.
Final grades at the top of the slopes must promote surface drainage away from the slope
crest. Water must not be allowed to flow in an uncontrolled fashion over the slope face. If
it is necessary to direct surface runoff towards the slope, it should be controlled at the top
of the slope, piped in a closed conduit installed on the slope face, and taken to an
appropriate point of discharge beyond the toe of the slope.
5.2.6 WET WEATHER CONSTRUCTION CONSIDERATIONS
RGI recommends that preparation for site grading and construction include procedures
intended to drain ponded water, control surface water runoff, and to collect shallow
subsurface seepage zones in excavations where encountered. It will not be possible to
successfully compact the subgrade or utilize on-site soils as structural fill if accumulated
water is not drained prior to grading or if drainage is not controlled during construction.
Attempting to grade the site without adequate drainage control measures will reduce the
amount of on-site soil effectively available for use, increase the amount of select import fill
materials required, and ultimately increase the cost of the earthwork phases of the project.
Free water should not be allowed to pond on the subgrade soils. RGI anticipates that the
Geotechnical Engineering Report 9 June 14, 2021
Chambers-Bagnell Property Development, Renton, Washington RGI Project No. 2021-316-1
use of berms and shallow drainage ditches, with sumps and pumps in utility trenches, will
be required for surface water control during wet weather and/or wet site conditions.
5.3 FOUNDATIONS
Following site preparation and grading, the proposed residence foundations can be
supported on conventional spread footings bearing on competent native soil or structural
fill. Loose, organic, or other unsuitable soils may be encountered in the proposed residence
footprints. If unsuitable soils are encountered, they should be overexcavated and backfilled
with structural fill. If loose soils are encountered, the soils should be moisture conditioned
and compacted to a firm and unyielding condition.
Perimeter foundations exposed to weather should be at a minimum depth of 18 inches
below final exterior grades. Interior foundations can be constructed at any convenient
depth below the floor slab. Finished grade is defined as the lowest adjacent grade within 5
feet of the foundation for perimeter (or exterior) footings and finished floor level for
interior footings.
Table 4 Foundation Design
Design Parameter Value
Allowable Bearing Capacity 2,000 psf1
Friction Coefficient 0.30
Passive pressure (equivalent fluid pressure) 250 pcf2
Minimum foundation dimensions Columns: 24 inches
Walls: 16 inches
1. psf = pounds per square foot
2. pcf = pounds per cubic foot
The allowable foundation bearing pressures apply to dead loads plus design live load
conditions. For short-term loads, such as wind and seismic, a 1/3 increase in this allowable
capacity may be used. At perimeter locations, RGI recommends not including the upper 12
inches of soil in the computation of passive pressures because they can be affected by
weather or disturbed by future grading activity. The passive pressure value assumes the
foundation will be constructed neat against competent soil or backfilled with structural fill
as described in Section 5.2.4. The recommended base friction and passive resistance value
includes a safety factor of about 1.5.
With spread footing foundations designed in accordance with the recommendations in this
section, maximum total and differential post-construction settlements of 1 inch and 1/2
inch, respectively, should be expected.
Geotechnical Engineering Report 10 June 14, 2021
Chambers-Bagnell Property Development, Renton, Washington RGI Project No. 2021-316-1
5.4 RETAINING WALLS
If retaining walls are needed for the residences or detention vaults, RGI recommends cast-
in-place concrete walls be used. The magnitude of earth pressure development on
retaining walls will partly depend on the quality of the wall backfill. RGI recommends
placing and compacting wall backfill as structural fill. Wall drainage will be needed behind
the wall face. A typical retaining wall drainage detail is shown in Figure 3.
With wall backfill placed and compacted as recommended, level backfill and drainage
properly installed, RGI recommends using the values in the following table for design.
Table 5 Retaining Wall Design
Design Parameter Value
Allowable Bearing Capacity 2,000 psf
Active Earth Pressure (unrestrained walls) 35 pcf
At-rest Earth Pressure (restrained walls) 50 pcf
For seismic design, an additional uniform load of 7 times the wall height (H) for
unrestrained walls and 14H in psf for restrained walls should be applied to the wall surface.
Friction at the base of foundations and passive earth pressure will provide resistance to
these lateral loads. Values for these parameters are provided in Section 5.3.
5.5 SLAB-ON-GRADE CONSTRUCTION
Once site preparation has been completed as described in Section 5.2, suitable support for
slab-on-grade construction should be provided. RGI recommends that the concrete slab be
placed on top of medium dense native soil or structural fill. Immediately below the floor
slab, RGI recommends placing a four-inch thick capillary break layer of clean, free-draining
sand or gravel that has less than five percent passing the U.S. No. 200 sieve. This material
will reduce the potential for upward capillary movement of water through the underlying
soil and subsequent wetting of the floor slab. Where moisture by vapor transmission is
undesirable, an 8- to 10-millimeter thick plastic membrane should be placed on a 4-inch
thick layer of clean gravel.
For the anticipated floor slab loading, we estimate post-construction floor settlements of
1/4- to 1/2-inch.
Geotechnical Engineering Report 11 June 14, 2021
Chambers-Bagnell Property Development, Renton, Washington RGI Project No. 2021-316-1
5.6 DRAINAGE
5.6.1 SURFACE
Final exterior grades should promote free and positive drainage away from the residence
area. Water must not be allowed to pond or collect adjacent to foundations or within the
immediate residence area. For non-pavement locations, RGI recommends providing a
minimum drainage gradient of 3 percent for a minimum distance of 10 feet from the
residence perimeter. In paved locations, a minimum gradient of 1 percent should be
provided unless provisions are included for collection and disposal of surface water
adjacent to the structure.
5.6.2 SUBSURFACE
RGI recommends installing perimeter foundation drains. A typical footing drain detail is
shown on Figure 4. The foundation drains and roof downspouts should be tightlined
separately to an approved discharge facility. Subsurface drains must be laid with a gradient
sufficient to promote positive flow to a controlled point of approved discharge.
5.6.3 INFILTRATION
Vashon-age lodgment till was encountered at depths ranging from approximately 1.5 to 3.5 feet
below existing grade in the test pits completed at the Site. The very dense lodgment till is
considered a “restrictive layer” in stormwater infiltration facility design.
The shallow depth to the lodgment till (restrictive layer) would make any conventional
infiltration facility (infiltration pond, infiltration trench, or infiltration gallery) infeasible due to
lack of the required separation distance between the base of these facilities and a restrictive
layer, typically 5 feet. The shallow depth to the restrictive layer would also make Low Impact
Development rain gardens infeasible due to the absence of sufficient thickness of permeable
soils below grade in which to construct the rain garden, in addition to required separation
distances from the base of a rain garden to a restrictive layer, 3 feet.
5.7 UTILITIES
Utility pipes should be bedded and backfilled in accordance with American Public Works
Association (APWA) specifications. For site utilities located within the right-of-ways,
bedding and backfill should be completed in accordance with City of Renton specifications.
At a minimum, trench backfill should be placed and compacted as structural fill, as
described in Section 5.2.4. Where utilities occur below unimproved areas, the degree of
compaction can be reduced to a minimum of 90 percent of the soil’s maximum density as
determined by the referenced ASTM D1557. The native soils excavated on site should be
suitable for use as backfill material. Imported structural fill meeting the gradation provided
in Table 2 may be necessary for trench backfilling wet weather.
Geotechnical Engineering Report 12 June 14, 2021
Chambers-Bagnell Property Development, Renton, Washington RGI Project No. 2021-316-1
6.0 Additional Services
RGI is available to provide further geotechnical consultation throughout the design phase
of the project. RGI should review the final design and specifications in order to verify that
earthwork and foundation recommendations have been properly interpreted and
incorporated into project design and construction.
RGI is also available to provide geotechnical engineering and construction monitoring
services during construction. The integrity of the earthwork and construction depends on
proper site preparation and procedures. In addition, engineering decisions may arise in the
field in the event that variations in subsurface conditions become apparent. Construction
monitoring services are not part of this scope of work. If these services are desired, please
let us know and we will prepare a cost proposal.
7.0 Limitations
This GER is the property of RGI, Conner Homes, and its designated agents. Within the limits
of the scope and budget, this GER was prepared in accordance with generally accepted
geotechnical engineering practices in the area at the time this GER was issued. This GER is
intended for specific application to the Chambers-Bagnell Property Development project in
Renton, Washington, and for the exclusive use of Conner Homes and its authorized
representatives. No other warranty, expressed or implied, is made. Site safety, excavation
support, and dewatering requirements are the responsibility of others.
The scope of services for this project does not include either specifically or by implication
any environmental or biological (for example, mold, fungi, bacteria) assessment of the site
or identification or prevention of pollutants, hazardous materials or conditions. If the
owner is concerned about the potential for such contamination or pollution, we can
provide a proposal for these services.
The analyses and recommendations presented in this GER are based upon data obtained
from the explorations performed on site. Variations in soil conditions can occur, the nature
and extent of which may not become evident until construction. If variations appear
evident, RGI should be requested to reevaluate the recommendations in this GER prior to
proceeding with construction.
It is the client’s responsibility to see that all parties to the project, including the designers,
contractors, subcontractors, are made aware of this GER in its entirety. The use of
information contained in this GER for bidding purposes should be done at the contractor’s
option and risk.
USGS, 2020, Renton, Washington
USGS, 2020, Maple Valley, Washington
7.5-Minute Quadrangle
Approximate Scale: 1"=1000'
0 500 1000 2000 N
Site Vicinity Map
Figure 1
06/2021
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Chambers-Bagnell Development
RGI Project Number:
2021-316-1
Date Drawn:
Address: 13818 152nd Avenue SE & 13929 154th Avenue SE, Renton, WA 98059
SITE
TP-1TP-2TP-3TP-4TP-506/2021Corporate Office17522 Bothell Way NortheastBothell, Washington 98011Phone: 425.415.0551Fax: 425.415.0311Chambers-Bagnell DevelopmentRGI Project Number:2021-316-1Date Drawn:Address: 13818 152nd Avenue SE & 13929 154th Avenue SE, Renton, WA 98059Figure 2Approximate Scale: 1"=100'050100200N= Boring by RGI, 05/18/21= Site boundaryGeotechnical Exploration Plan
Incliniations)
12" Over the Pipe
3" Below the Pipe
Perforated Pipe
4" Diameter PVC
Compacted Structural
Backfill (Native or Import)
12" min.
Filter Fabric Material
12" Minimum Wide
Free-Draining Gravel
Slope to Drain
(See Report for
Appropriate
Excavated Slope
06/2021
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Chambers-Bagnell Development
RGI Project Number:
2021-316-1
Date Drawn:
Address: 13818 152nd Avenue SE & 13929 154th Avenue SE, Renton, WA 98059
Retaining Wall Drainage Detail
Figure 3
Not to Scale
3/4" Washed Rock or Pea Gravel
4" Perforated Pipe
Building Slab
Structural
Backfill
Compacted
Filter Fabric
06/2021
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Chambers-Bagnell Development
RGI Project Number:
2021-316-1
Date Drawn:
Address: 13818 152nd Avenue SE & 13929 154th Avenue SE, Renton, WA 98059
Typical Footing Drain Detail
Figure 4
Not to Scale
Geotechnical Engineering Report June 14, 2021
Chambers-Bagnell Property Development, Renton, Washington RGI Project No. 2021-316-1
APPENDIX A
FIELD EXPLORATION AND LABORATORY TESTING
On May 18, 2021, RGI performed field explorations using a mini excavator. We explored
subsurface soil conditions at the site by observing the excavation of five test pits to a
maximum depth of 10 feet below existing grade. The test pit locations are shown on Figure
2. The test pit locations were approximately determined by measurements from existing
property lines and paved roads.
A geologist from our office conducted the field exploration and classified the soil conditions
encountered, maintained a log of each test exploration, obtained representative soil
samples, and observed pertinent site features. All soil samples were visually classified in
accordance with the Unified Soil Classification System (USCS).
Representative soil samples obtained from the explorations were placed in closed
containers and taken to our laboratory for further examination and testing. As a part of the
laboratory testing program, the soil samples were classified in our in house laboratory
based on visual observation, texture, plasticity, and the limited laboratory testing described
below.
Moisture Content Determinations
Moisture content determinations were performed in accordance with ASTM D2216-10
Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil
and Rock by Mass (ASTM D2216) on representative samples obtained from the exploration
in order to aid in identification and correlation of soil types. The moisture content of typical
sample was measured and is reported on the test pit logs.
Grain Size Analysis
A grain size analysis indicates the range in diameter of soil particles included in a particular
sample. Grain size analyses was determined using D6913-04(2009) Standard Test Methods
for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis (ASTM D6913) on
three of the samples.
Project Name:Chambers-Bagnell Property Development
Project Number:2021-316-1
Client:Conner Homes
Test Pit No.: TP-1
Date(s) Excavated:May 18, 2021
Excavation Method:Test Pit
Excavator Type:Mini
Groundwater Level:7.5 feet
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 13818 152nd Avenue Southeast & 13929 154th Avenue Southeast, Renton,
Washington
Surface Conditions:Grass
Total Depth of Excavation:10 feet bgs
Approximate
Surface Elevation 382 feet
Compaction Method Bucket Tamp
USCS SymbolTPSL
Fill
SP-SM
SM
REMARKS AND OTHER TESTS
16% moisture
11% moisture, 31% fines
10% moisture
33% moistureGraphic LogMATERIAL DESCRIPTION
9 inches of topsoil
Brown to gray silty SAND with some gravel, medium
dense, moist (Fill)
Brown SAND with some silt, medium dense, moist
Becomes gray
Gray silty SAND with some gravel, dense, moist (Glacial
Till)
Becomes very dense
Becomes moist to wet
Light to moderate groundwater seepage
Becomes moist
Test pit terminated at 10 feetDepth (feet)0
5
10 Sample NumberSample TypeElevation (feet)382
377
372
Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Chambers-Bagnell Property Development
Project Number:2021-316-1
Client:Conner Homes
Test Pit No.: TP-2
Date(s) Excavated:May 18, 2021
Excavation Method:Test Pit
Excavator Type:Mini
Groundwater Level:Not encountered
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 13818 152nd Avenue Southeast & 13929 154th Avenue Southeast, Renton,
Washington
Surface Conditions:Grass
Total Depth of Excavation:5.5 feet bgs
Approximate
Surface Elevation 386 feet
Compaction Method Bucket Tamp
USCS SymbolTPSL
SM
SM
REMARKS AND OTHER TESTS
33% moisture
12% moisture, 24% finesGraphic LogMATERIAL DESCRIPTION
9 inches of topsoil
Brown silty SAND with some gravel, loose to medium
dense, moist
Becomes medium dense
Gray silty SAND with some gravel, dense, moist (Glacial
Till)
Becomes dense to very dense
Test pit terminated at 5.5 feetDepth (feet)0
5
10 Sample NumberSample TypeElevation (feet)386
381
376
Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Chambers-Bagnell Property Development
Project Number:2021-316-1
Client:Conner Homes
Test Pit No.: TP-3
Date(s) Excavated:May 18, 2021
Excavation Method:Test Pit
Excavator Type:Mini
Groundwater Level:Not encountered
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 13818 152nd Avenue Southeast & 13929 154th Avenue Southeast, Renton,
Washington
Surface Conditions:Grass
Total Depth of Excavation:4 feet bgs
Approximate
Surface Elevation 386 feet
Compaction Method Bucket Tamp
USCS SymbolTPSL
SM
SM
REMARKS AND OTHER TESTS
14% moistureGraphic LogMATERIAL DESCRIPTION
8 inches of topsoil
Reddish brown silty sand with some gravel, loose to
medium dense, moist
Gray silty SAND with some gravel, dense, moist (Glacial
Till)
Becomes very dense
Test pit terminated at 4 feetDepth (feet)0
5
10 Sample NumberSample TypeElevation (feet)386
381
376
Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Chambers-Bagnell Property Development
Project Number:2021-316-1
Client:Conner Homes
Test Pit No.: TP-4
Date(s) Excavated:May 18, 2021
Excavation Method:Test Pit
Excavator Type:Mini
Groundwater Level:Not encountered
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 13818 152nd Avenue Southeast & 13929 154th Avenue Southeast, Renton,
Washington
Surface Conditions:Grass
Total Depth of Excavation:6 feet bgs
Approximate
Surface Elevation 384 feet
Compaction Method Bucket Tamp
USCS SymbolTPSL
SM
SM
SM
REMARKS AND OTHER TESTS
22% moisture
11% moistureGraphic LogMATERIAL DESCRIPTION
11 inches of topsoil
Reddish brown silty SAND with trace gravel, loose, moist
Becomes medium dense
Tan silty SAND, medium dense, moist
Gray silty SAND with some gravel, dense, moist (Glacial
Till)
Test pit terminated at 6 feetDepth (feet)0
5
10 Sample NumberSample TypeElevation (feet)384
379
374
Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Chambers-Bagnell Property Development
Project Number:2021-316-1
Client:Conner Homes
Test Pit No.: TP-5
Date(s) Excavated:May 18, 2021
Excavation Method:Test Pit
Excavator Type:Mini
Groundwater Level:Not encountered
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 13818 152nd Avenue Southeast & 13929 154th Avenue Southeast, Renton,
Washington
Surface Conditions:Grass
Total Depth of Excavation:5 feet bgs
Approximate
Surface Elevation 390 feet
Compaction Method Bucket Tamp
USCS SymbolTPSL
SM
SM
REMARKS AND OTHER TESTS
10% moisture, 18% fines
12% moistureGraphic LogMATERIAL DESCRIPTION
10 inches of topsoil
Reddish brown silty SAND with some gravel, loose to
medium dense, moist
Gray silty SAND with some gravel, dense, moist (Glacial
Till)
Test pit terminated at 5 feetDepth (feet)0
5
10 Sample NumberSample TypeElevation (feet)390
385
380
Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Chambers-Bagnell Property Development
Project Number:2021-316-1
Client:Conner Homes
Key to Logs
USCS SymbolREMARKS AND OTHER TESTSGraphic LogMATERIAL DESCRIPTIONDepth (feet)Sample NumberSample TypeElevation (feet)1 2 3 4 5 6 7 8
COLUMN DESCRIPTIONS
1 Elevation (feet): Elevation (MSL, feet).
2 Depth (feet): Depth in feet below the ground surface.
3 Sample Type: Type of soil sample collected at the depth interval
shown.
4 Sample Number: Sample identification number.
5 USCS Symbol: USCS symbol of the subsurface material.
6 Graphic Log: Graphic depiction of the subsurface material
encountered.
7 MATERIAL DESCRIPTION: Description of material encountered.
May include consistency, moisture, color, and other descriptive
text.
8 REMARKS AND OTHER TESTS: Comments and observations
regarding drilling or sampling made by driller or field personnel.
FIELD AND LABORATORY TEST ABBREVIATIONS
CHEM: Chemical tests to assess corrosivity
COMP: Compaction test
CONS: One-dimensional consolidation test
LL: Liquid Limit, percent
PI: Plasticity Index, percent
SA: Sieve analysis (percent passing No. 200 Sieve)
UC: Unconfined compressive strength test, Qu, in ksf
WA: Wash sieve (percent passing No. 200 Sieve)
MATERIAL GRAPHIC SYMBOLS
AF
Silty SAND (SM)
Poorly graded SAND with Silt (SP-SM)
Topsoil
TYPICAL SAMPLER GRAPHIC SYMBOLS
Auger sampler
Bulk Sample
3-inch-OD California w/
brass rings
CME Sampler
Grab Sample
2.5-inch-OD Modified
California w/ brass liners
Pitcher Sample
2-inch-OD unlined split
spoon (SPT)
Shelby Tube (Thin-walled,
fixed head)
OTHER GRAPHIC SYMBOLS
Water level (at time of drilling, ATD)
Water level (after waiting)
Minor change in material properties within a
stratum
Inferred/gradational contact between strata
?Queried contact between strata
GENERAL NOTES
1: Soil classifications are based on the Unified Soil Classification System. Descriptions and stratum lines are interpretive, and actual lithologic changes may be
gradual. Field descriptions may have been modified to reflect results of lab tests.
2: Descriptions on these logs apply only at the specific boring locations and at the time the borings were advanced. They are not warranted to be representative
of subsurface conditions at other locations or times.
Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Chambers-Bagnell Property - Geotech SAMPLE ID/TYPE TP-1
PROJECT NO.2021-316-1 SAMPLE DEPTH 4 feet
TECH/TEST DATE EW/RT 5/18/2021 DATE RECEIVED 5/18/2021
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)389.7 Weight Of Sample (gm)351.4
Wt Dry Soil & Tare (gm) (w2)351.4 Tare Weight (gm) 15.8
Weight of Tare (gm) (w3)15.8 (W6) Total Dry Weight (gm) 335.6
Weight of Water (gm) (w4=w1-w2) 38.3 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 335.6 Cumulative
Moisture Content (%) (w4/w5)*100 11 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"15.8 0.00 0.00 100.00 cobbles
% C GRAVEL 10.0 3.0"15.8 0.00 0.00 100.00 coarse gravel
% F GRAVEL 14.5 2.5" coarse gravel
% C SAND 5.6 2.0" coarse gravel
% M SAND 9.2 1.5"15.8 0.00 0.00 100.00 coarse gravel
% F SAND 29.5 1.0" coarse gravel
% FINES 31.2 0.75"49.4 33.60 10.01 89.99 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"78.0 62.20 18.53 81.47 fine gravel
D10 (mm)#4 98.1 82.30 24.52 75.48 coarse sand
D30 (mm)#10 117.0 101.20 30.15 69.85 medium sand
D60 (mm)#20 medium sand
Cu #40 147.8 132.00 39.33 60.67 fine sand
Cc #60 fine sand
#100 220.8 205.00 61.08 38.92 fine sand
#200 246.8 231.00 68.83 31.17 fines
PAN 351.4 335.60 100.00 0.00 silt/clay
DESCRIPTION Silty SAND with some gravel
USCS SM
Prepared For:Reviewed By:
Conner Homes
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Chambers-Bagnell Property - Geotech SAMPLE ID/TYPE TP-2
PROJECT NO.2021-316-1 SAMPLE DEPTH 3 feet
TECH/TEST DATE EW/RT 5/18/2021 DATE RECEIVED 5/18/2021
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)342.5 Weight Of Sample (gm)306.7
Wt Dry Soil & Tare (gm) (w2)306.7 Tare Weight (gm) 15.8
Weight of Tare (gm) (w3)15.8 (W6) Total Dry Weight (gm) 290.9
Weight of Water (gm) (w4=w1-w2) 35.8 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 290.9 Cumulative
Moisture Content (%) (w4/w5)*100 12 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"15.8 0.00 0.00 100.00 cobbles
% C GRAVEL 7.4 3.0"15.8 0.00 0.00 100.00 coarse gravel
% F GRAVEL 11.6 2.5" coarse gravel
% C SAND 7.5 2.0" coarse gravel
% M SAND 15.0 1.5"15.8 0.00 0.00 100.00 coarse gravel
% F SAND 35.0 1.0" coarse gravel
% FINES 23.7 0.75"37.2 21.40 7.36 92.64 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"46.6 30.80 10.59 89.41 fine gravel
D10 (mm)#4 70.8 55.00 18.91 81.09 coarse sand
D30 (mm)#10 92.6 76.80 26.40 73.60 medium sand
D60 (mm)#20 medium sand
Cu #40 136.2 120.40 41.39 58.61 fine sand
Cc #60 fine sand
#100 214.4 198.60 68.27 31.73 fine sand
#200 237.9 222.10 76.35 23.65 fines
PAN 306.7 290.90 100.00 0.00 silt/clay
DESCRIPTION Silty SAND with some gravel
USCS SM
Prepared For:Reviewed By:
Conner Homes
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Chambers-Bagnell Property - Geotech SAMPLE ID/TYPE TP-5
PROJECT NO.2021-316-1 SAMPLE DEPTH 1.5 feet
TECH/TEST DATE EW/RT 5/18/2021 DATE RECEIVED 5/18/2021
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)346.5 Weight Of Sample (gm)316.2
Wt Dry Soil & Tare (gm) (w2)316.2 Tare Weight (gm) 16.0
Weight of Tare (gm) (w3)16.0 (W6) Total Dry Weight (gm) 300.2
Weight of Water (gm) (w4=w1-w2) 30.3 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 300.2 Cumulative
Moisture Content (%) (w4/w5)*100 10 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"16.0 0.00 0.00 100.00 cobbles
% C GRAVEL 18.9 3.0"16.0 0.00 0.00 100.00 coarse gravel
% F GRAVEL 23.9 2.5" coarse gravel
% C SAND 7.4 2.0" coarse gravel
% M SAND 11.4 1.5"16.0 0.00 0.00 100.00 coarse gravel
% F SAND 20.4 1.0" coarse gravel
% FINES 18.1 0.75"72.8 56.80 18.92 81.08 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"120.5 104.50 34.81 65.19 fine gravel
D10 (mm)#4 144.5 128.50 42.80 57.20 coarse sand
D30 (mm)#10 166.7 150.70 50.20 49.80 medium sand
D60 (mm)#20 medium sand
Cu #40 200.8 184.80 61.56 38.44 fine sand
Cc #60 fine sand
#100 244.2 228.20 76.02 23.98 fine sand
#200 262.0 246.00 81.95 18.05 fines
PAN 316.2 300.20 100.00 0.00 silt/clay
DESCRIPTION Silty Gravelly SAND
USCS SM
Prepared For:Reviewed By:
Conner Homes
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200