HomeMy WebLinkAboutRS_Technical Information Report_220318_v1.pdf.
Maple Highlands
Preliminary Plat #LUA-XXXXXX
Drainage Report
March 2022
Maple Highlands – Conner Homes
i
Drainage Report
March 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
03/18/2022
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 .......................................................................................................... 5
Core Requirement No. 4: Conveyance System ............................................................................................. 7
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 ............................................................................................................................... 6
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 .......................................................................................................... 8
Appendices
Appendix A – TIR Worksheet
Appendix B – Existing Conditions Map
Appendix C – Proposed Conditions Map
Appendix D – Peak Flow Control Application Map and MGS Flood Calculations
Appendix E – On-Site BMPs Credits and Calculations (To Be Provided With Future Submittal)
Appendix F – Pipe Conveyance (To Be Provided With Future Submittal)
Appendix G – Erosion Control Plan and Details (To Be Provided With Future Submittal)
Appendix H – SWPPP (To Be Provided With Future Submittal)
Appendix I – Bond Quantity Worksheet (To Be Provided With Future Submittal)
Appendix J – Operation and Maintenance Manual (To Be Provided With Future Submittal)
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 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. This scope of work includes construction of 12 single-
family homes, construction of SE 139th Place and 153rd Ave SE onsite, and associated frontage improvements,
grading, utilities, 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.
KPFF Consulting Engineers
2
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.
Maple Highlands – Conner Homes
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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 following tasks were completed as part of the offsite
analysis:
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.
KPFF Consulting Engineers
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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
Maple Highlands – Conner Homes
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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.
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 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.
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. 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.
KPFF Consulting Engineers
6
Figure 3-1: Predeveloped Areas
Figure 3-2: Developed Areas
Maple Highlands – Conner Homes
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Table 3-2: On-Site Area Summary
Impervious (Acres) Pervious (Acres) Total (Acres)
Predeveloped Conditions 0.00 4.16 4.16
Developed Conditions 2.01 2.15 4.16
Table 3-3: MGSFlood Peak Flow Rate with 15-Minute Time Step
Predeveloped Peak
Flows (cfs)
Developed Peak Flows
(cfs)
2-Year Peak Flow 0.105 0.052
10-Year Peak Flow 0.205 0.143
CORE REQUIREMENT NO. 4: CONVEYANCE SYSTEM
The development is required to convey the 25-year, 24-hour peak flow without overtopping. Pipe system
structures may overtop for runoff events exceeding the 25-year design capacity, provided overflow runoff from
a 100-year event does not create or aggravate a severe erosion or flooding problem downstream.
The proposed conveyance system has been designed to convey the 25-year peak flow without overtopping
any pipe system structure. The minimum proposed pipe has a capacity of 0.928 cfs, more than four times
greater than the 25-year developed peak flow of 0.197 cfs. See Figure 3-3 for a Manning’s calculation of the
capacity of the minimum proposed pipe and Appendix D for additional peak flow calculations.
Figure 3-3: Manning’s Calculation for Minimum Capacity Pipe
KPFF Consulting Engineers
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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. Additional BMP Operation and Maintenance guidelines will be provided with a future submittal.
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.
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 2H: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.
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
Maple Highlands – Conner Homes
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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 and insufficient
flow paths.
Where full dispersion of target impervious areas is not feasible or applicable, or will cause flooding or erosion
impacts, the feasibility and applicability of full infiltration must be evaluated. Full infiltration has been
determined to be unfeasible due to poor soil infiltration characteristics.
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.
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
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, Native Growth Retention Credit, and Tree Retention Credit will be
evaluated along with implementation of the soil amendment BMP as detailed in Section C.2.13 of the RSWM
and roof drain perforated pipe connection as detailed in Section C.2.11 of the RSWM in a future submittal.
KPFF Consulting Engineers
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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 revised delineations of aquifer protection areas within the city, the project site is not located
within any aquifer protection area or wellhead protection zone.
Maple Highlands – Conner Homes
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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
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
01/19/2022
Soil Amendment
TBD
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-4
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet
per Threshold Discharge Area)
Maintenance and Operation Responsibility (circle one): Private / Public
If Private, Maintenance Log Required: Yes / No
Financial Guarantees and Liability Provided: Yes / No
Water Quality (include facility
summary sheet)
Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog
or Exemption No. _______________________
Special Requirements (as applicable):
Area Specific Drainage
Requirements
Type: SDO / MDP / BP / Shared Fac. / None
Name: ________________________
Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None
100-year Base Flood Elevation (or range): _______________
Datum:
Flood Protection Facilities Describe:
Source Control
(commercial / industrial land use)
Describe land use:
Describe any structural controls:
Oil Control High-Use Site: Yes / No
Treatment BMP: _________________________________
Maintenance Agreement: Yes / No
with whom? _____________________________________
Other Drainage Structures
Describe:
None
None
REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
2017 City of Renton Surface Water Design Manual 12/12/2016 Ref 8-A-5
Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS
MINIMUM ESC REQUIREMENTS
DURING CONSTRUCTION
Clearing Limits
Cover Measures
Perimeter Protection
Traffic Area Stabilization
Sediment Retention
Surface Water Collection
Dewatering Control
Dust Control
Flow Control
Control Pollutants
Protect Existing and Proposed
BMPs/Facilities
Maintain Protective BMPs / Manage
Project
MINIMUM ESC REQUIREMENTS
AFTER CONSTRUCTION
Stabilize exposed surfaces
Remove and restore Temporary ESC Facilities
Clean and remove all silt and debris, ensure
operation of Permanent BMPs/Facilities, restore
operation of BMPs/Facilities as necessary
Flag limits of sensitive areas and open space
preservation areas
Other _______________________
Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch)
Flow Control Type/Description Water Quality Type/Description
Detention
Infiltration
Regional Facility
Shared Facility
On-site BMPs
Other
________________
________________
________________
________________
________________
________________
Vegetated Flowpath
Wetpool
Filtration
Oil Control
Spill Control
On-site BMPs
Other
________________
________________
________________
________________
________________
________________
________________
Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS
Drainage Easement
Covenant
Native Growth Protection Covenant
Tract
Other ____________________________
Cast in Place Vault
Retaining Wall
Rockery > 4′ High
Structural on Steep Slope
Other _______________________________
X
X
X
X
X
X
X
X
X
X
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
03/18/2022
Maple Highlands – Conner Homes
Appendix B
Appendix B
Existing Conditions Map
612 Woodland Square Loop SE,
Suite 100
Lacey, WA 98503
360.292.7230
www.kpff.com
612 Woodland Square Loop SE,
Suite 100
Lacey, WA 98503
360.292.7230
www.kpff.com
612 Woodland Square Loop SE,
Suite 100
Lacey, WA 98503
360.292.7230
www.kpff.com
612 Woodland Square Loop SE,
Suite 100
Lacey, WA 98503
360.292.7230
www.kpff.com
Maple Highlands – Conner Homes
Appendix C
Appendix C
Proposed Conditions Map
380
376 378
382 384
386
39
0
384
38
6
38
8
39
2
39
4388
384384
38
6
386
386386386
3
8
6
3861
BPE 388.4
2
BPE 387.4
3
BPE 386.4
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 139TH PL
154TH AVE SEROCKERY
ROCKERY
CIP RETAINING WALL
CB #13
RIM=385.15
8" CPEP IE IN=381.68 (E)
EX 12" CPEP IE IN=381.34 (N)
EX 12" CPEP IE OUT=381.34 (S)
CB #12
RIM=385.50
8" CPEP IE IN=381.95 (SE)
8" CPEP IE OUT=381.95 (W)
CB #11
RIM=385.81
8" CPEP IE OUT=382.21 (NW)
CB #5
RIM=384.51
8" DI IE OUT=381.15 (N)
CB#4
RIM=384.32
8" DI IE IN=381.01 (S)
8" DI IE OUT=381.01 (E)
CB #1
RIM=383.68
8" DI IE OUT=381.03 (W)
CB #2
RIM=383.68
8" DI IE IN=380.91 (W)
8" DI IE OUT=380.91 (SE)
CB #3
RIM=384.53
8" DI IE IN=380.73 (NW)
8" DI IE IN=380.73 (W)
8" DI IE OUT=380.73 (E)
CB #6
RIM=385.28
8" CPEP IE IN=380.55 (W)
8" CPEP IE IN=380.55 (S)
8" CPEP IE OUT=380.55 (E)
CB #7
RIM=385.31
8" CPEP IE OUT=380.79 (N)
CB #8
RIM=386.82
8" CPEP IE IN=379.30 (W)
8" CPEP IE OUT=379.30 (S)
CB #9
RIM=390.91
8" DI IE
OUT=388.16 (E)
CB #10
RIM=390.98
8" 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 #14
RIM=382.64
12" CPEP IE IN=378.52 (W)
12" CPEP IE OUT=378.52 (E)
35 LF 8" CPEP @ 0.7%
37 LF 8" CPEP @ 0.7%28 LF 8" DI @ 0.5%
56 LF 8" DI @ 0.5%
23 LF 8" DI @ 0.5%
36 LF 8" DI @ 0.5%
36 LF 8" CPEP @ 0.5%
24 LF 8"
CPEP @ 1.0%
150 LF 8"
CPEP @ 1.5%
77 LF 8"
CPEP @ 1.5%
36 LF 8" CPEP @ 0.7%
26 LF 8" CPEP
@ 0.7%
27 LF 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 387.16386380376378382384386TOP OF POND 385.45
BOT OF POND 374.08
INTERIOR SLOPES 2:1
EX TREE TO REMAIN, SEE
LANDSCAPE PLANS FOR
ADDITIONAL DETAIL (TYP)
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-XXXX03/18/2022
10MAPLE HIGHLANDSLUA22-XXXXXXC22-XXXXXXPR22-XXXXXXC4.0DRAINAGE CONTROL PLAN
5
0
1 INCH = 40 FEET
20'40'80'
LEGEND
ROAD CENTERLINE
LOT LINE
EASEMENT
ROW/PROPERTY LINE
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
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.
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)
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: 03/16/2022 11:48 AM
Report Generation Date: 03/16/2022 11:48 AM
—————————————————————————————————
Input File Name: 2022-03-16 Wetpond.fld
Project Name: Chambers Plat
Analysis Title: 2022-03-16
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) 4.160 4.160
Area of Links that Include Precip/Evap (acres) 0.000 0.000
Total (acres) 4.160 4.160
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
C, Forest, Flat 4.160
----------------------------------------------
Subbasin Total 4.160
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1 ----------
-------Area (Acres) --------
C, Lawn, Mod 2.150
ROADS/FLAT 0.710
ROOF TOPS/FLAT 1.300
----------------------------------------------
Subbasin Total 4.160
************************* 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
Prismatic Pond Option Used
Pond Floor Elevation (ft) : 100.00
Riser Crest Elevation (ft) : 105.00
Max Pond Elevation (ft) : 105.50
Storage Depth (ft) : 5.00
Pond Bottom Length (ft) : 133.4
Pond Bottom Width (ft) : 66.7
Pond Side Slopes (ft/ft) : Z1= 2.00 Z2= 2.00 Z3= 2.00 Z4= 2.00
Bottom Area (sq-ft) : 8898.
Area at Riser Crest El (sq-ft) : 13,300.
(acres) : 0.305
Volume at Riser Crest (cu-ft) : 55,163.
(ac-ft) : 1.266
Area at Max Elevation (sq-ft) : 13784.
(acres) : 0.316
Vol at Max Elevation (cu-ft) : 61,934.
(ac-ft) : 1.422
Hydraulic Conductivity (in/hr) : 0.00
Massmann Regression Used to Estimate Hydralic Gradient
Depth to Water Table (ft) : 100.00
Bio-Fouling Potential : Low
Maintenance : Average or Better
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 18.00
Common Length (ft) : 0.023
Riser Crest Elevation : 105.00 ft
Hydraulic Structure Geometry
Number of Devices: 2
---Device Number 1 ---
Device Type : Circular Orifice
Control Elevation (ft) : 100.00
Diameter (in) : 1.07
Orientation : Horizontal
Elbow : No
--- Device Number 2 ---
Device Type : Vertical Rectangular Orifice
Control Elevation (ft) : 102.90
Length (in) : 0.28
Height (in) : 25.19
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
********** 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 101.683
1.11-Year 101.840
1.25-Year 102.131
2.00-Year 102.913
3.33-Year 103.328
5-Year 103.704
10-Year 104.097
25-Year 104.549
50-Year 104.692
100-Year 104.807
***********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 1 791.675
_____________________________________
Total: 791.675
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 276.908
Link: New Structure Lnk2 0.000
_____________________________________
Total: 276.908
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 5.011 ac-ft/year, Post Developed: 1.753 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): 12526. cu-ft
Computed Large Wet Pond Volume, 1.5*Basic Volume: 18789. cu-ft
2-Year Discharge Rate : 0.052 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.32 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.18 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 1534.88
Inflow Volume Including PPT-Evap (ac-ft): 1534.88
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): 1534.66
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 0.105 2-Year 5.214E-02
5-Year 0.165 5-Year 0.104
10-Year 0.205 10-Year 0.143
25-Year 0.283 25-Year 0.197
50-Year 0.311 50-Year 0.216
100-Year 0.337 100-Year 0.231
200-Year 0.498 200-Year 0.279
500-Year 0.716 500-Year 0.343
** 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%): -27.6% PASS
Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -19.6% PASS
Maximum Excursion from Q2 to Q50 (Must be less than 10%): -16.8% 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
(To Be Provided With Future Submittal)
Maple Highlands – Conner Homes
Appendix F
Appendix F
Pipe Conveyance
(To Be Provided With Future Submittal)
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
(To Be Provided With Future Submittal)
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
(To Be Provided With Future Submittal)
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.
Geotechnical Engineering Report 3 June 14, 2021
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.
Geotechnical Engineering Report 5 June 14, 2021
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
Geotechnical Engineering Report 6 June 14, 2021
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
Geotechnical Engineering Report 7 June 14, 2021
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.
Geotechnical Engineering Report 8 June 14, 2021
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