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TABLE OF CONTENTS
Section Title
1 Project Overview 1-1
2 Conditions and Requirements Summary 2-1
3 Offsite Analysis 3-1
4 Flow Control/Water Quality Facility Analysis and Design 4-1
5 Conveyance System Analysis and Design 5-1
6 Special Reports and Studies 6-1
7 Other Permits 7-1
8 SWPPP Analysis and Design 8-1
9 Bond Quantities, Facility Summaries 9-1
10 Operations and Maintenance Manual 10-1
Technical Information Report 1-1 LDC Job No. 16-137
1 PROJECT OVERVIEW
The Renton Special Care Community project proposes the construction of four
cottages, three for resident housing and the fourth to act as the administration/
kitchen building. Approximately 50,000 SF of impervious surface and roughly 21,000
SF of pervious surface is proposed onsite and within the Right-of-Way frontage. The
proposed development proposes four convalescent buildings, access drive aisles,
parking, associated utilities and ROW improvements on a 1.65 acre site. The subject
property is located on parcels 0087000285 and 0087000293 at 17033 108 th Avenue SE,
Renton, WA 98055. Access to the proposed project will be gained from the south and
east via SE 172nd St and 108th Ave SE respectively.
The subject property is comprised of two parcels, one is currently developed with a
vacant single-family residence, associated driveway and landscaped areas and the
other parcel is undeveloped with moderate to dense vegetation. Site soils are dense
to very dense Vashon Till, exhibiting low infiltration rates. Existing grades across the
property are moderate across most the site, ranging from 2 to 25%, sloping mainly
from the northeast to the southwest.
Runoff from the site currently flows to the southwest and exits the subject property
at the southwest corner of the site, entering the municipal storm drainage system
located in SE 172nd ST. Downstream flows eventually outlet into the Black River, a
tributary of the Duwamish River.
A lot combination will be completed to combine the two parcels to one. Offsite
frontage clearing activities will result in additional disturbed area impacts to the site.
See Developed Hydrology Map, Figure 4.2 for a graphical depiction of the proposed
development.
This report and calculations were produced in accordance with the 2016 King County
Surface Water Design Manual and the 2017 City of Renton Surface Water Design
Manual (2017 City of Renton SWDM).
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
__________________
__________________
__________________
Renton Special Care Community LLC Renton Special Care Community
98040
C17002683
2731 77th AVE SE, Suite #203 Mercer Island, WA
29
Mark Villwock 5E
LDC, Inc.29
425-806-1869 17033 108th AVE SE
Renton, WA 98055
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 ______________________
_____________________________________
none
none
none
none
none
N/A N/A
N/A N/A
N/A
N/A
N/A
N/A
N/A N/A
N/A
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: _________________________
Vashon Till 2-25%N/A
section 3 pg 3-1
section 3 pg 3-1
section 2 pg 2-2
N/A
N/A
N/A
Flows exit the site and proceed through a series of culverts and roadside ditches crossing state route 515.
All 9 requirements are required
12/6/16
Detention Pipe
N/A
Michael S. Place, PE
(425)409-2505
(253)255-7805
1
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:
N/A
N/A
Grease Interceptor Used
contech Filterra Enhanced Water Treatment Facility
Commercial
N/A
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 _______________________________
Detention Pipe
Porous Pavement
Grease Interceptor
Planning
Structural
Engineering
Survey
Planning Structural EngineeringSurvey
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Technical Information Report 2-1 LDC Job No. 16-137
2 Conditions and Requirements Summary
This report was produced in accordance with the 2017 City of Renton Surface Water
Design Manual (2017 City of Renton SWDM). Per Chapter I of the Manual, the
proposed development requires a Full Drainage Review, meeting all nine core
requirements as well as all six special requirements, since there will be more than
2,000 square feet of new impervious surfaces and more than 7,000 sf of land
disturbing activities. A summary of how each of the minimum requirements is met is
described in this section.
Core Requirement #1: Discharge at the Natural Location: The existing site runoff
discharges the site along the southern and western property boundaries. All site
runoff ends up in a roadside ditch located on the north end of SE 172nd ST. In the
developed condition all runoff will be conveyed to the previously described natural
discharge location.
Core Requirement #2: Offsite Analysis: No discernable upstream run-off flows onto
the subject property. Onsite runoff discharges as concentrated flow into a roadside
ditch and culvert located in the southwest corner of the property. Downstream flows
are conveyed in the westerly direction through a series of roadside ditch, culvert,
storm pipe, catch basins and natural and engineered drainage swales. No signs of
constrictions, capacity issues, erosion or sedimentation were noted along the
downstream investigation. See Offsite Analysis in Section 3 of this report.
Core Requirement #3: Flow Control: Historic site conditions, assuming all forested,
must be used for the predeveloped conditions. Flow control will be provided by a
detention pipe facility located beneath the parking and access drive aisle along the
western and northern property boundaries. See Flow Control/Water Quality Facility
Analysis and Design, section 4 of this report for additional information.
Technical Information Report 2-2 LDC Job No. 16-137
Core Requirement #4: Conveyance System: The new pipe system for this project
will be sized to meet the 100-year peak flows. See Conveyance System Analysis and
Design, section 5, for additional information regarding conveyance analysis and
conveyance capacity.
Core Requirement #5: Erosion and Sediment Control: See SWPPP Analysis and
Design, Section 8 of this Report for the SWPPP BMP Elements.
Core Requirement #6: Maintenance and Operations: The stormwater detention and
water quality facilities will be maintained by the property owner. An emergency
access easement will be granted to the City of Renton. See Operations and
Maintenance in Section 10 of this report.
Core Requirement #7: Financial Guarantees and Liability: Any required
performance or assurance bonds will be posted with the City as required.
Core Requirement #8: Water Quality: Based on the 2017 City of Renton SWDM, this
project must meet the requirements of the Enhanced Basic Water Quality Treatment.
The proposed enhanced treatment facility is a Filterra Bioretention Systems an
approved method by 2017 RSWDM section 14-A. See Flow Control/Water Quality
Analysis and Design in Section 4 of this report for additional information.
Core Requirement #9: On-site BMPs: The 2017 City of Renton SWDM requires that all
target surfaces must provide onsite BMPs to the maximum extent feasible to mitigate
impacts of increased stormwater surface runoff per Large Lot BMP Requirements,
section C.1.3.2. Permeable Pavement is the only feasible BMP applied to the site per
section C.2.7, satisfying the onsite BMP requirements. Additionally all pervious
surfaces will be protected in accordance with the soil amendment BMP detailed in
Appendix C, Section C.2.1.3. See Flow Control/Water Quality Analysis and Design in
Section 4 of this report for additional information.
Technical Information Report 2-3 LDC Job No. 16-137
Special Requirement #1: Other Adopted Area-Specific Requirements: There are no
Critical Drainage Areas, Master Drainage Plans, Basin Plans, Salmon Conservation
Plans, Stormwater Compliance Plans, Lake Management Plans, Flood Hazard
Reduction Plan Updates, or Shared Facility Drainage Plans within the vicinity of this
project. Therefore, this requirement does not apply to the project.
Special Requirement #2: Flood Hazard Area Delineation: Per the FEMA Flood
Insurance Rate Map 53033C0979 F, the site is located in Zone C corresponding to an
area outside of the 500-year flood plain. Therefore, there are no flood hazard areas
(100-year floodplains, zero-rise flood fringe, zero-rise floodway, FEMA floodway, or
channel migration zones) on or adjacent to this site. Therefore, this requirement
does not apply to the project.
Special Requirement #3: Flood Protection Facilities: There are no levees or
revetments on or adjacent to this site. Therefore this requirement does not apply to
the project.
Special Requirement #4: Source Controls: Source controls such as wheel wash
stations and utility corridor maintenance are proposed within the SWPPP and TESC
plan.
Special Requirement #5: Oil Control: Based on the Traffic Analysis report by Gibson
Traffic Consultants, Inc dated June 2016 there are an estimated 150 ADT for the
whole site which is a total of 65,715 sf. The threshold for requiring oil control is 100
ADT per 1,000 SF , since our site will only bring in a total of 150ADT for the site the
proposed site does not exceed the threshold.
Special Requirement #6 Aquifer Protection Area: This project is not within an
aquifer protection area and is therefore not applicable to this project.
Technical Information Report 3-1 LDC Job No. 16-137
3.0 OFFSITE ANALYSIS
Task 1. Study Area Definition and Maps
King County LiDAR, survey, and 2012 aerial photography were the best topographical
references available for the area containing the site. The limits of downstream
analysis extended roughly 0.25 miles from the site’s natural discharge location. Please
reference Task 3 below for a detailed description of the downstream flow path (See
Figure 3.0 Downstream Analysis Map).
Task 2. Resource Review
All of the resources below have been reviewed for existing and potential issues near
the project site:
Adopted Basin Plans
No Adopted Basin Plans were located that include the project site.
Drainage Basin
This site is located within the Panther Creek drainage sub basin. The sub
basin flows are tributary to the Black River and ultimately to the Duwamish
River.
Floodplain / Floodway (FEMA) maps
According to FEMA mapping this project is not within a floodplain.
Sensitive Areas
Sensitive areas are not located on the site.
Drainage Complaints and Studies
According to email correspondence with Ann Fowler, on 10/13/2017, there are
not any drainage complaints of concern in or near the subject property’s
downstream flow path.
Road Drainage Problems
No issues were identified near the proposed site.
Technical Information Report 3-2 LDC Job No. 16-137
Wetland Inventory Maps
There are no wetland areas located on or downstream of the proposed subject
property. This has been verified in the critical areas study as completed by
others
Section 303d List of Polluted Waters
The proposed subject property is not tributary to any 303d listed waters
within ¼ of a mile from the subject property.
Stormwater Compliance Plans
Not applicable to the proposed project.
Task 3. Field Inspection
On Tuesday December 6th, 2016 upstream and downstream analyses were performed
at the site. The following observations were verified during this visit. Please refer to
Figure 3.0, Downstream Analysis Map, for reference locations.
Upstream Analysis
As observed on December 6th, 2016 site visit, there is no discernable upstream flow
entering the proposed site.
Downstream Analysis
Runoff from the subject property discharges the site at the southwest property
boundary and enters a 12” concrete driveway culvert located on the northern side of
SE 172nd St. Flows continue westward through the roadside ditch and are redirected
southerly, crossing SE 172nd St via a 12” concrete culvert, and are discharged into an
open densely vegetated parcel to the south. Flows then enter an 18 inch concrete
culvert, flow westerly, crossing State Route 515 Benson Dr. S, and are discharged into
an engineered open channel located on a private parcel. Open channel flows are
mitigated via 12”+ riprap and flows enter an 18” PVC pipe. Tightlined flows are
conveyed westerly via 18” PVC pipe along S 36th St., crossing the ¼ mile downstream
analysis extent boundary.
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3.0FIGURE:
PROJECTION: WASHINGTONSTATE PLANE, NORTH ZONE,NAD 83 HARN, FEET
JOB NUMBER: 16-137DRAWING NAME: 16-137F03
DRAWING BY: T.ABBOTTDATE: 12-07-16SCALE: AS SHOWNJURISDICTION: RENTON
DESIGNER: T.ABBOTT
REVISION:
S O U R C E
I N F O R M A T I O N
D E S C R I P T I O N
S O U R C E
A G E N C Y
1 6 -1 3 7 D o w n s t r e a m A n a l y s i s M a p .m x d | M O D : 1 2 /0 7 /2 0 1 6 | D E W
VICINITY MAP
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10 Foot Contour
Contours (LiDAR)
2 Foot Contour
LEGEND
Subject Property
Downstream Flowpath
Storm Node
Parcel Boundary
Storm System
!(
Parcel Boundary
Technical Information Report 3-3 LDC Job No. 16-137
Image 1: Downstream flow conveyed in SE 172nd St roadside ditch
Image 2: Concentrated flows are discharged from 18” concrete culvert crossing Benson Dr S (State
Route 515) into an open channel heading westward
Technical Information Report 3-4 LDC Job No. 16-137
Image 3: Open channel flows are mitigated with riprap and collected and conveyed westward via
18” PVC storm drain pipe
Image 4: Downstream flows are conveyed westerly through a series of catch basins and 18” storm
drain pipe located in S 36th St, crossing the ¼ mile downstream analysis extent threshold
Technical Information Report 4-1 LDC Job No. 16-137
4.0 FLOW CONTROL/WATER QUALITY FACILITY ANALYSIS AND DESIGN
The flow control and water quality requirements are identified in the 2017 City of
Renton Surface Water Design Manual.
Pre-Developed Conditions:
See the following page, Figure 4.1 Existing Hydrology Map, for a graphical depiction of
the pre-developed hydrology. See below for the areas as modeled in WWHM4:
Targeted Basin:
Forested 1.65 Acres
Total 1.65 Acres
Developed Conditions:
See the following page, Figure 4.2 Developed Hydrology Map, for a graphical depiction
of the developed hydrology. See below for the areas as modeled in WWHM4:
Basin A (tributary to detention facility):
Pervious landscape 0.39 Acres
Impervious 0.96 Acres
Total 1.25 Acres
Pervious Pavement (tributary to detention facility):
Pervious Pave 4,556 SF
Total 0.10 Acres
Detention Bypass:
Pervious 0.23 Acres
Impervious 0.07 Acres
Total 0.30 Acres
4 1 0
410
3 9 0
4
0
0
390
4 0 0
4
0
0
4 1 0
4
1
0
4.1FIGURE:
PROJECTION: WASHINGTONSTATE PLANE, NORTH ZONE,NAD 83 HARN, FEET
JOB NUMBER: 16-137DRAWING NAME: 16-137F04
DRAWING BY: D.WESTLEYDATE: 9-6-17SCALE: AS SHOWNJURISDICTION: RENTON
DESIGNER: D.WESTLEY
REVISION:
S O U R C E
I N F O R M A T I O N
D E S C R I P T I O N
S O U R C E
A G E N C Y
1 6 -1 3 7 P r e d e v e l o p e d H y d r o l o g y M a p .m x d | M O D : 9 /0 6 /2 0 1 7 | T P A
VICINITY MAP
R E N T O N S P E C I A L C A R E C O M M U N I T Y , L L C
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K I N G
C O U N T Y
G I S
C O N T O U R S
G E N E R A T E D
F R O M
B A R E
E A R T H
L i D A R
(K I N G
C O U N T Y ).
T H I S
D A T A
H A S
A
S T A T E D
V E R T I C A L
A C C U R A C Y
O F
A P P R O X I M A T E L Y
1
F O O T .
T H E C I V I L E N G I N E E R I N G G R O U P
C o m m e r c i a l
I n f r a s t r u c t u r e
R e s i d e n t i a l
1 4 2 0 1 N E 2 0 0 t h S t ., #1 0 0
W o o d i n v i l l e , W A 9 8 0 7 2
P h . 4 2 5 .8 0 6 .1 8 6 9
w w w .L D C c o r p .c o m
F x . 4 2 5 .4 8 2 .2 8 9 3
q
Scale in Feet
0 40 80
10 Foot Contour
Contours (LiDAR)
2 Foot Contour
LEGEND
Subject Property
Parcel Boundary
P A R C E L
B O U N D A R Y
C I T Y
O F
R E N T O N
G I S
S
R
-
5
2
2
MAPPED EXTENT
Watercourse
1 0 8 t h A v e S E
1 0 8 t h A v e S E
SE 172nd St
A E R I A L S
E X P R E S S ,
I N C .
A E R I A L
I M A G E R Y
DEVELOPED BASIN ATOTAL = 1.69 AC
DEVELOPED BASIN ATOTAL = 1.69 AC
GRIND AND OVERLAY
410
3 9 0
4
0
0
390
4 0 0
4
0
0
4 1 0
4
1
0
4 1 0
4.2FIGURE:
PROJECTION: WASHINGTONSTATE PLANE, NORTH ZONE,NAD 83 HARN, FEET
JOB NUMBER: 16-137DRAWING NAME: 16-137F4.2
DRAWING BY: D.WESTLEYDATE: 9-06-2017SCALE: AS SHOWNJURISDICTION: RENTON
DESIGNER: D.WESTLEY
REVISION:
S O U R C E
I N F O R M A T I O N
D E S C R I P T I O N
S O U R C E
A G E N C Y
1 6 -1 3 7 D e v e l o p e d H y d r o l o g y M a p .m x d | M O D : 9 /0 6 /2 0 1 7 | T P A
VICINITY MAP
R E N T O N S P E C I A L C A R E C O M M U N I T Y , L L C
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M
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P
K I N G
C O U N T Y
G I S
C O N T O U R S
G E N E R A T E D
F R O M
B A R E
E A R T H
L i D A R
(K I N G
C O U N T Y ).
T H I S
D A T A
H A S
A
S T A T E D
V E R T I C A L
A C C U R A C Y
O F
A P P R O X I M A T E L Y
1
F O O T .
T H E C I V I L E N G I N E E R I N G G R O U P
C o m m e r c i a l
I n f r a s t r u c t u r e
R e s i d e n t i a l
1 4 2 0 1 N E 2 0 0 t h S t ., #1 0 0
W o o d i n v i l l e , W A 9 8 0 7 2
P h . 4 2 5 .8 0 6 .1 8 6 9
w w w .L D C c o r p .c o m
F x . 4 2 5 .4 8 2 .2 8 9 3
q
Scale in Feet
0 40 80
10 Foot Contour
Contours (LiDAR)
2 Foot Contour
LEGEND
Subject Property
Parcel Boundary
P A R C E L
B O U N D A R Y
C I T Y
O F
R E N T O N
G I S
S
R
-
5
2
2
MAPPED EXTENT
Watercourse
1 0 8 t h A v e S E
1 0 8 t h A v e S E
SE 172nd St
A E R I A L S
E X P R E S S ,
I N C .
A E R I A L
I M A G E R Y
DEVELOPED BASIN A1.35 AC
DEVELOPED BASIN AREAS
DEVELOPED BASIN A TOTAL
TOTAL =1.35 ACPERVIOUS0.39 AC
LID PERMEABLE PAVEMENT 0.10 AC
IMPERVIOUS 0.96 AC
BYPASS BASIN TOTAL = 0.30 AC FLOW CONTROL MITIGATION TRADE*
NON-TARGET EXISTING PAVEMENT TO FLOW CONTROL FACILITY=3,500 SF
ROW PAVEMENT FLOW CONTROL BYPASS =200 SF
PRIVATE DRIVE PAVEMENT FLOW CONTROL BYPASS =1,800 SF
FLOW CONTROL BYPASS
TOTAL =0.30 AC
PERVIOUS 0.23 AC
IMPERVIOUS 0.07 AC
NON-TARGET IMPERVIOUS SURFACE
EXISTING PAVEMENT 3,500 SF
TARGET SURFACE AREA BYPASS
TOTAL =3,500 SFPRIVATE DRIVE PAVEMENT 1,800 SF
ROW PAVEMENT 200 SF
MITIGATION TRADE NET
TOTAL =0 SFTARGET (BYPASS)- 3,500 SF
NON-TARGET (TO FC)3,500 SF
* ALL AREAS NOTED ARE PGIS.CALCULATIONS REFLECT PGIS TRADE CALCULATIONS.
PAVEMENT FLOW CONTROL BYPASS = 1,500 SF
ROW PAVEMENT 1,500 SFGRIND AND OVERLAY
Technical Information Report 4-2 LDC Job No. 16-137
4.1 Flow Control Facility
Based on the City of Renton’s flow control map and City of Renton Municipal Code 4-
6-030.c., the site falls within the Flow Control Duration Standard (for Forested Site
Conditions). Flow control standards shall be according to the 1.2.3.B of the 2017
RSWDM. Flow control performance “shall match the predeveloped site’s discharge
duration for the discharge rates between fifty percent (50%) of the two (2) year peak
flow through the fifty (50) year peak flow and the two (2) and ten (10) year peak
discharge assuming forested site conditions as the predeveloped site condition”.
The proposed detention pipe facility has been designed in accordance with the City of
Renton SWDM design criteria in section 5.1.2.1, general requirements for Detention
Tanks. Flow control compliance modeling and analysis has been assessed using WWHM
4 in accordance with the 2017 City of Renton SWDM section 5.1.2.2.
WWHM Modeled Detention Pipe
Pipe Diameter: 8’
Pipe Length: 480’
Bottom of Pipe: 390.00
Sediment Storage: 0.5’
Begin Live Storage: 391.50
Live Storage Depth: 7.0’
Top of Riser Elevation: 398.50
Freeboard: 0.5’
Top of Pipe Elevation: 399.00
See the following pages for the WWHM 4 project report containing predeveloped and
mitigated land use description, detention facility hydraulic table, predeveloped and
mitigated hydrology and release rates, and analysis passing report summary.
Flow Control Mitigation Trade
A flow control facility mitigation trade is utilized per 2017 City of Renton SWDM
section 1.2.3.2.G, Mitigation Trades. The project’s onsite flow control facility has
been designed to mitigate for an area of existing non-targeted impervious surface
area located in the 108th AVE SE frontage road in trade for not mitigating part of the
Technical Information Report 4-3 LDC Job No. 16-137
project’s targeted impervious surfaces that cannot be vertically routed to the
proposed flow control facility. The target impervious surface areas being traded are a
portion of the 108th AVE SE ROW and a portion of the private drive aisle at the
southwestern portion of the site. The proposed mitigation trade meets or exceeds
conditions, #1 through #5, per section 1.2.3.2.G.
Condition 1: Both the non-targeted existing pavement and both ROW pavement flow
control bypass areas are made up of roadway runoff. The non- target pavement flow
are similar in peak flow and volume as the ROW pavement control bypass as seen in
Figure 4.2.
Condition 2: The non-targeted existing pavement, and area identified to be traded is
all within the same drainage basin and all flows converge without an easement.
Condition 3: The same amount of PGIS is being traded both from ROW which results
in a similar amount of runoff volume which means the net effect will essentially be
zero for this trade.
Condition 4: There are no sensitive downstream drainage systems downstream of the
project site thus there would not be a significant adverse impact downstream to this
trade.
Condition 5: The area proposed to be traded is ROW pavement and will not be
developed further in the future besides pavement restoration.
Condition 6: Mitigation trade proposals must be reviewed and approved with input
from the City of Renton. Please see Figure 4.2, Developed Hydrology Map, for a
graphical depiction of the proposed flow control mitigation trade areas.
Technical Information Report 4-4 LDC Job No. 16-137
Additional target surfaces that cannot be routed to the onsite flow control facilities
will be modeled in WWHM as bypass, per the conditions listed in the 2017 City of
Renton SWDM section 1.2.3.2.E all the conditions are met as follows:
Condition 1: The bypass trade both onsite and offsite are both within the same
drainage basin and converge within a quarter mile downstream.
Condition 2: The bypass increase does not exceed 0.4 cfs as seen in the WWHM 4
output.
Condition 3: There are no sensitive downstream drainage systems downstream of the
project site thus there would not be a significant adverse impact downstream due to
the bypass.
Condition 4: The bypass trade will be collected and treated for water quality.
Condition 5: The difference between the peak 100-year discharge using 15-min time
steps compared to the existing site conditions does not exceed 0.15 cfs. The flow
control facility provides additional storage volume to account for the bypass flows
without receiving the bypass flows.
Please see Figure 4.2, Developed Hydrology Map, for a graphical depiction of the
proposed flow control bypass areas. See WWHM4 model output for just bypass
predeveloped and developed pre-mitigated (701) flows following WWHM4 Project
Report.
WWHM4
PROJECT REPORT
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General Model Information
Project Name:20170918_ConstructionSizing
Site Name:
Site Address:
City:
Report Date:9/20/2017
Gage:Seatac
Data Start:1948/10/01
Data End:1998/09/30
Timestep:15 Minute
Precip Scale:1.000
Version Date:2016/11/23
POC Thresholds
Low Flow Threshold for POC1:50 Percent of the 2 Year
High Flow Threshold for POC1:50 Year
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Landuse Basin Data
Predeveloped Land Use
Basin 1
Bypass:No
GroundWater:No
Pervious Land Use acre
C, Forest, Flat 1.64
Pervious Total 1.64
Impervious Land Use acre
Impervious Total 0
Basin Total 1.64
Element Flows To:
Surface Interflow Groundwater
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Mitigated Land Use
Basin 1
Bypass:No
GroundWater:No
Pervious Land Use acre
C, Pasture, Flat 0.29
Pervious Total 0.29
Impervious Land Use acre
ROADS FLAT 0.35
ROOF TOPS FLAT 0.39
SIDEWALKS FLAT 0.21
Impervious Total 0.95
Basin Total 1.24
Element Flows To:
Surface Interflow Groundwater
Tank 1 Tank 1
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Bypass
Bypass:Yes
GroundWater:No
Pervious Land Use acre
C, Pasture, Flat 0.23
Pervious Total 0.23
Impervious Land Use acre
ROADS FLAT 0.03
SIDEWALKS FLAT 0.04
Impervious Total 0.07
Basin Total 0.3
Element Flows To:
Surface Interflow Groundwater
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Routing Elements
Predeveloped Routing
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Mitigated Routing
Porous Pavement 1
Pavement Area:0.1031 acre.Pavement Length: 67.00 ft.
Pavement Width: 67.00 ft.
Pavement slope 1:0.03 To 1
Pavement thickness: 0.5
Pour Space of Pavement: 0.35
Material thickness of second layer: 2
Pour Space of material for second layer: 0.35
Material thickness of third layer: 0
Pour Space of material for third layer: 0
Infiltration On
Infiltration rate:0.05
Infiltration safety factor:1
Total Volume Infiltrated (ac-ft.):12.312
Total Volume Through Riser (ac-ft.):0.073
Total Volume Through Facility (ac-ft.):12.384
Percent Infiltrated:99.42
Total Precip Applied to Facility:0
Total Evap From Facility:1.011
Element Flows To:
Outlet 1 Outlet 2
Tank 1
Porous Pavement Hydraulic Table
Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs)
0.0000 0.103 0.000 0.000 0.000
0.0333 0.103 0.001 0.000 0.005
0.0667 0.103 0.002 0.000 0.005
0.1000 0.103 0.003 0.000 0.005
0.1333 0.103 0.004 0.000 0.005
0.1667 0.103 0.006 0.000 0.005
0.2000 0.103 0.007 0.000 0.005
0.2333 0.103 0.008 0.000 0.005
0.2667 0.103 0.009 0.000 0.005
0.3000 0.103 0.010 0.000 0.005
0.3333 0.103 0.012 0.000 0.005
0.3667 0.103 0.013 0.000 0.005
0.4000 0.103 0.014 0.000 0.005
0.4333 0.103 0.015 0.000 0.005
0.4667 0.103 0.016 0.000 0.005
0.5000 0.103 0.018 0.000 0.005
0.5333 0.103 0.019 0.178 0.005
0.5667 0.103 0.020 0.252 0.005
0.6000 0.103 0.021 0.308 0.005
0.6333 0.103 0.022 0.356 0.005
0.6667 0.103 0.024 0.398 0.005
0.7000 0.103 0.025 0.436 0.005
0.7333 0.104 0.026 0.471 0.005
0.7667 0.104 0.027 0.504 0.005
0.8000 0.104 0.029 0.535 0.005
0.8333 0.104 0.030 0.564 0.005
0.8667 0.104 0.031 0.591 0.005
0.9000 0.104 0.032 0.617 0.005
0.9333 0.104 0.033 0.643 0.005
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0.9667 0.104 0.035 0.667 0.005
1.0000 0.104 0.036 0.690 0.005
1.0333 0.104 0.037 0.713 0.005
1.0667 0.104 0.038 0.735 0.005
1.1000 0.104 0.039 0.756 0.005
1.1333 0.104 0.041 0.777 0.005
1.1667 0.104 0.042 0.797 0.005
1.2000 0.104 0.043 0.817 0.005
1.2333 0.104 0.044 0.836 0.005
1.2667 0.104 0.046 0.855 0.005
1.3000 0.104 0.047 0.873 0.005
1.3333 0.104 0.048 0.891 0.005
1.3667 0.104 0.049 0.909 0.005
1.4000 0.104 0.050 0.926 0.005
1.4333 0.104 0.052 0.943 0.005
1.4667 0.104 0.053 0.960 0.005
1.5000 0.104 0.054 0.976 0.005
1.5333 0.105 0.055 0.993 0.005
1.5667 0.105 0.057 1.009 0.005
1.6000 0.105 0.058 1.024 0.005
1.6333 0.105 0.059 1.040 0.005
1.6667 0.105 0.060 1.055 0.005
1.7000 0.105 0.061 1.070 0.005
1.7333 0.105 0.063 1.084 0.005
1.7667 0.105 0.064 1.099 0.005
1.8000 0.105 0.065 1.113 0.005
1.8333 0.105 0.066 1.128 0.005
1.8667 0.105 0.068 1.142 0.005
1.9000 0.105 0.069 1.155 0.005
1.9333 0.105 0.070 1.169 0.005
1.9667 0.105 0.071 1.183 0.005
2.0000 0.105 0.073 1.196 0.005
2.0333 0.105 0.074 1.209 0.005
2.0667 0.105 0.075 1.222 0.005
2.1000 0.105 0.076 1.235 0.005
2.1333 0.105 0.077 1.248 0.005
2.1667 0.105 0.079 1.261 0.005
2.2000 0.105 0.080 1.273 0.005
2.2333 0.105 0.081 1.286 0.005
2.2667 0.105 0.082 1.298 0.005
2.3000 0.105 0.084 1.310 0.005
2.3333 0.106 0.085 1.322 0.005
2.3667 0.106 0.086 1.334 0.005
2.4000 0.106 0.087 1.346 0.005
2.4333 0.106 0.089 1.358 0.005
2.4667 0.106 0.090 1.370 0.005
2.5000 0.106 0.093 1.381 0.005
2.5333 0.106 0.097 1.393 0.005
2.5667 0.106 0.100 1.404 0.005
2.6000 0.106 0.104 1.415 0.005
2.6333 0.106 0.108 1.562 0.005
2.6667 0.106 0.111 1.822 0.005
2.7000 0.106 0.115 2.154 0.005
2.7333 0.106 0.118 2.546 0.005
2.7667 0.106 0.122 2.988 0.005
2.8000 0.106 0.125 3.477 0.005
2.8333 0.106 0.129 4.007 0.005
2.8667 0.106 0.132 4.575 0.005
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2.9000 0.106 0.136 5.179 0.005
2.9333 0.106 0.140 5.817 0.005
2.9667 0.106 0.143 6.488 0.005
3.0000 0.106 0.147 7.188 0.005
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Tank 1
Dimensions
Depth:8 ft.
Tank Type:Circular
Diameter:8 ft.
Length:470 ft.
Discharge Structure
Riser Height:7.5 ft.
Riser Diameter:18 in.
Orifice 1 Diameter:0.5 in.Elevation:0.5 ft.
Orifice 2 Diameter:1.125 in.Elevation:5.73 ft.
Orifice 3 Diameter:0.5 in.Elevation:6.5 ft.
Element Flows To:
Outlet 1 Outlet 2
Tank Hydraulic Table
Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs)
0.0000 0.000 0.000 0.000 0.000
0.0889 0.018 0.001 0.000 0.000
0.1778 0.025 0.003 0.000 0.000
0.2667 0.031 0.005 0.000 0.000
0.3556 0.035 0.008 0.000 0.000
0.4444 0.039 0.011 0.000 0.000
0.5333 0.043 0.015 0.001 0.000
0.6222 0.046 0.019 0.002 0.000
0.7111 0.049 0.023 0.003 0.000
0.8000 0.051 0.028 0.003 0.000
0.8889 0.054 0.032 0.004 0.000
0.9778 0.056 0.037 0.004 0.000
1.0667 0.058 0.043 0.005 0.000
1.1556 0.060 0.048 0.005 0.000
1.2444 0.062 0.053 0.005 0.000
1.3333 0.064 0.059 0.006 0.000
1.4222 0.066 0.065 0.006 0.000
1.5111 0.067 0.071 0.006 0.000
1.6000 0.069 0.077 0.007 0.000
1.6889 0.070 0.083 0.007 0.000
1.7778 0.071 0.089 0.007 0.000
1.8667 0.073 0.096 0.007 0.000
1.9556 0.074 0.102 0.008 0.000
2.0444 0.075 0.109 0.008 0.000
2.1333 0.076 0.116 0.008 0.000
2.2222 0.077 0.122 0.008 0.000
2.3111 0.078 0.129 0.009 0.000
2.4000 0.079 0.136 0.009 0.000
2.4889 0.079 0.143 0.009 0.000
2.5778 0.080 0.151 0.009 0.000
2.6667 0.081 0.158 0.010 0.000
2.7556 0.082 0.165 0.010 0.000
2.8444 0.082 0.172 0.010 0.000
2.9333 0.083 0.180 0.010 0.000
3.0222 0.083 0.187 0.010 0.000
3.1111 0.084 0.195 0.011 0.000
3.2000 0.084 0.202 0.011 0.000
3.2889 0.084 0.210 0.011 0.000
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3.3778 0.085 0.217 0.011 0.000
3.4667 0.085 0.225 0.011 0.000
3.5556 0.085 0.232 0.011 0.000
3.6444 0.086 0.240 0.012 0.000
3.7333 0.086 0.248 0.012 0.000
3.8222 0.086 0.255 0.012 0.000
3.9111 0.086 0.263 0.012 0.000
4.0000 0.086 0.271 0.012 0.000
4.0889 0.086 0.278 0.012 0.000
4.1778 0.086 0.286 0.013 0.000
4.2667 0.086 0.294 0.013 0.000
4.3556 0.086 0.301 0.013 0.000
4.4444 0.085 0.309 0.013 0.000
4.5333 0.085 0.317 0.013 0.000
4.6222 0.085 0.324 0.013 0.000
4.7111 0.084 0.332 0.013 0.000
4.8000 0.084 0.339 0.014 0.000
4.8889 0.084 0.347 0.014 0.000
4.9778 0.083 0.354 0.014 0.000
5.0667 0.083 0.362 0.014 0.000
5.1556 0.082 0.369 0.014 0.000
5.2444 0.082 0.376 0.014 0.000
5.3333 0.081 0.384 0.014 0.000
5.4222 0.080 0.391 0.015 0.000
5.5111 0.079 0.398 0.015 0.000
5.6000 0.079 0.405 0.015 0.000
5.6889 0.078 0.412 0.015 0.000
5.7778 0.077 0.419 0.023 0.000
5.8667 0.076 0.426 0.028 0.000
5.9556 0.075 0.433 0.032 0.000
6.0444 0.074 0.439 0.035 0.000
6.1333 0.073 0.446 0.037 0.000
6.2222 0.071 0.452 0.040 0.000
6.3111 0.070 0.458 0.042 0.000
6.4000 0.069 0.465 0.044 0.000
6.4889 0.067 0.471 0.046 0.000
6.5778 0.066 0.477 0.050 0.000
6.6667 0.064 0.482 0.052 0.000
6.7556 0.062 0.488 0.055 0.000
6.8444 0.060 0.494 0.057 0.000
6.9333 0.058 0.499 0.059 0.000
7.0222 0.056 0.504 0.061 0.000
7.1111 0.054 0.509 0.063 0.000
7.2000 0.051 0.514 0.064 0.000
7.2889 0.049 0.518 0.066 0.000
7.3778 0.046 0.522 0.068 0.000
7.4667 0.043 0.526 0.069 0.000
7.5556 0.039 0.530 0.279 0.000
7.6444 0.035 0.533 0.941 0.000
7.7333 0.031 0.536 1.830 0.000
7.8222 0.025 0.539 2.831 0.000
7.9111 0.018 0.541 3.830 0.000
8.0000 0.000 0.542 4.717 0.000
8.0889 0.000 0.000 5.410 0.000
DR
A
F
T
20170918_ConstructionSizing 9/20/2017 8:30:05 AM Page 12
Analysis Results
POC 1
+ Predeveloped x Mitigated
Predeveloped Landuse Totals for POC #1
Total Pervious Area:1.64
Total Impervious Area:0
Mitigated Landuse Totals for POC #1
Total Pervious Area:0.52
Total Impervious Area:1.123053
Flow Frequency Method:Log Pearson Type III 17B
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period Flow(cfs)
2 year 0.041538
5 year 0.063061
10 year 0.074565
25 year 0.086168
50 year 0.093021
100 year 0.098633
Flow Frequency Return Periods for Mitigated. POC #1
Return Period Flow(cfs)
2 year 0.036604
5 year 0.049231
10 year 0.058611
25 year 0.071678
50 year 0.082332
100 year 0.093809
Annual Peaks
Annual Peaks for Predeveloped and Mitigated. POC #1
Year Predeveloped Mitigated
1949 0.046 0.034
1950 0.067 0.059
1951 0.104 0.089
1952 0.032 0.028
1953 0.025 0.029
1954 0.037 0.034
1955 0.064 0.034
1956 0.051 0.061
1957 0.039 0.039
1958 0.045 0.033