HomeMy WebLinkAboutEX_11_RS_Drainage_Report_Contour_2208_v1PRELIMINARY TECHNICAL
INFORMATION REPORT
FOR
BENSON-PETROVITSKY
REDVELOPMENT
CITY OF RENTON, KING COUNTY, WASHINGTON
AUGUST 2022
Prepared For:
TA Acquisitions LLC
2600 N Dallas Parkway, Ste 370
Frisco, TX 75034
Prepared By:
James Rausch,E.I.T., Design Engineer
Approved By:
Brett M. Allen, P.E., Principal Engineer
PO Box 949
Gig Harbor, WA 98335
(253) 857-5454
Project #19-045
I hereby state that this Technical Information Report for Benson-Petrovitsky Redevelopment has been prepared by me or under my
supervision and meets the standard of care and expertise that is usual and customary in this community of professional engineers.
I understand that the City of Renton does not and will not assume liability for the sufficiency, suitability or performance of drainage
facilities prepared by Contour Engineering LLC.This analysis is based on data and records either supplied to, or obtained by,
Contour Engineering, LLC. These documents are referenced within the text of the analysis. The analysis has been prepared
utilizing procedures and practices within the standard accepted practices of the industry.
EXHIBIT 11
RECEIVED
12/21/2022 JDing
PLANNING DIVISION
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TABLE OF CONTENTS
PAGE
1.0 PROJECT OVERVIEW ..................................................................................................................................2
1.1 PURPOSE AND SCOPE ......................................................................................................................................2
1.2 PROJECT DESCRIPTION ...................................................................................................................................2
1.3 EXISTING CONDITIONS SUMMARY..................................................................................................................3
1.4 DEVELOPED CONDITIONS ...............................................................................................................................4
2.0 CONDITIONS AND REQUIREMENTS SUMMARY ...............................................................................5
3.0 OFFSITE ANALYSIS (LEVEL 2 DOWNSTREAM).................................................................................7
3.1 DEFINE AND MAP STUDY AREA .....................................................................................................................7
3.2 REVIEW ALL AVAILABLE INFORMATION OF THE STUDY AREA ......................................................................7
3.3 FIELD INSPECT THE STUDY AREA ...................................................................................................................7
3.4 EXISTING AND PREDICTED DRAINAGE AND WATER QUALITY ISSUES ............................................................7
4.0 FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) AND WATER QUALITY FACILITY
ANALYSIS AND DESIGN........................................................................................................................................8
4.1 EXISTING SITE HYDROLOGY...........................................................................................................................8
4.2 DEVELOPED SITE HYDROLOGY ......................................................................................................................8
4.3 PERFORMANCE STANDARDS ...........................................................................................................................8
4.4 FLOW CONTROL SYSTEM................................................................................................................................8
4.5 WATER QUALITY SYSTEM ..............................................................................................................................9
5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN ..............................................................................9
6.0 SPECIAL REPORTS AND STUDIES .........................................................................................................9
7.0 OTHER PERMITS ..........................................................................................................................................9
8.0 CSWPP PLAN ANALYSIS AND DESIGN ................................................................................................9
9.0 BOND QUANTITIES, FACILITY SUMMARIES & DECLARATION OF COVENANT .....................9
10.0 OPERATIONS AND MAINTENANCE MANUAL .................................................................................9
Appendix A General Exhibits
Appendix B Downstream Analysis
Appendix C Flow Control and Water Quality Calculations
Appendix D Geotechnical Report (By PanGEO)
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1.0 PROJECT OVERVIEW
1.1 Purpose and Scope
This Preliminary Technical Information Report accompanies the Benson-Petrovitsky
redevelopment preliminary site plan review application.The site is located at 12055 Slater
Avenue NE in Kirkland, Washington and is located within the northwest quarter of Section
28, Township 26 North, Range 5 East, W.M.See Appendix A for Vicinity Map.
The 2022 City of Renton Surface Water Design Manual,(RSWDM)establishes the
design methodology and design criteria used for this project.
1.2 Project Description
The proposed project includes the construction of a Chase Bank and 7-Eleven gas station.
The proposed Chase Bank is approximately 2,850 SF of floor space .The proposed 7-
Eleven is approximately 4,088 SF of floor space.The project will include new curb and
gutter, sidewalks,illumination, and lane widening along the frontage of Benson DR S and
SE Petrovitsky RD
Currently, stormwater is being collected and conveyed in a series of catch basins and
discharged directly offsite from the subject property with no mitigation.To meet flow
control requirements, a detention vault with a storage volume of approximately 27,000
CF is proposed under the parking lot.
The following is a description of pertinent site information associated with the proposed
project:
Site Address –17426 Benson Dr S, Renton, WA 98055
Parcel Number –2923059110, 2923059095, 2923059017
Site Area –73,002 SF (Prior to ROW dedications), 63,843 SF (Post)
Zoning –CA, Commercial Arterial
Maps and exhibits of the site location can be found in Appendix A.
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1.3 Existing Conditions Summary
Pre-Developed Conditions
The site is developed and currently includes a disused towing facility, abandoned fire
station, and associated paved parking and storage lots.There is no existing on-site
detention system under the current condition.
Topography
The site generally slopes down from southeast to northwest --SE Petrovitsky Rd is
sloping down from east to west, and Benson Dr S is sloping down from south to north,
around the subject parcels. Slopes onsite generally range from 2-5% in the parking
areas.
Groundcover
There is little vegetation on the developed portions of the parcels –but there is a clump
of trees in the areas between parking lots.
Soils
The USDA Natural Resource Conservation Service (NRCS) Web Soil Survey indicates that
the site is underlain by Arents Alderwood Material,6 to 15 percent slopes (AmC). This
gravelly sandy loam is moderately well drained.See Appendix A for a copy of the NRCS
Web Soil Survey map for the site area.
Per the geotechnical report prepared by PanGEO, the native soils under the site consist
of Vashon till –a dense composite of clay, silt, sand, and gravel. PanGEO recommends
alternative stormwater solutions from infiltration due to these soils. See Appendix D for
the geotechnical report.
Adjacent Land Uses
The site is bounded as follows:
North:Commercial buildings (incl church and lodgings)
South:SE Petrovitsky Road
East:Commercial buildings
West:Benson Drive S
Drainage Patterns
Currently, stormwater is being collected and discharged to the public storm mains in
Benson Dr S and SE Petrovitsky RD. It is conveyed in the city system northwest beyond
the site.
Critical and Sensitive Areas
The site does not have any known critical or sensitive areas.
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1.4 Developed Conditions
Developed Site Description
The developed site will consist of a covered gas fueling island, 7-Eleven, and Chase Bank
with associated parking and drive aisles, as well as widened frontage features with
sidewalks and street illumination.Stormwater will runoff from impervious frontage
features and be tightlined to or collected by catch basins on -site, which will be directed
to an 8’ detention vault with a volume of 27,000 CF. The stormwater will then be routed
through a water quality device and pump system, before being discharged off -site into
Benson Drive S.
Surface Coverage Type Area
Total Developed Parcel Area:63,843 SF (1.465 AC)
Proposed Roof Area 9,144 SF
Proposed Sidewalk Area:4,841 SF
Pavement Area:33,720 SF
Pervious Area:16,138 SF
The site meets the requirements for a ‘Full Drainage Review’ and Flow Control BMPs have
been implemented as feasible and applicable to the site based on the existing site
constraints of the parcel size/shape, topography and native soils.
This project is required to implement Flow Control BMP’s per the Large Lot BMP
Requirements. Below is the list of BMP’s which are required to be assessed –infeasibility
criteria is presented for all of these BMP’s.
1.Full Dispersion is infeasible due to the required impervious area to be dispersed
being over the 15% of the site.
2.Infiltration BMP’s are infeasible due to the underlying native soils on site –per the
geotechnical report by PanGEO, the site soils are comprised of Vashon Till, and
cannot support infiltration BMP’s.
3.Basic dispersion is infeasible for this site due to a lack of any location wi th which
to disperse on-site.
Therefore, the proposed runoff is being delivered to the city conveyance system via a
tightlined pipe system. Flow control is being provided by an on-site detention system.
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2.0 CONDITIONS AND REQUIREMENTS SUMMARY
According to Figure 1.1.2.A in the 202 RSWDM, the project will be subjected to a Full
Drainage Review. Projects subject to full drainage review are required to demonstrate
that they are compliant with all nine core requirements discussed in Section 1.2 of the
2022 RSWDM and all five special requirements in Section 1.3 of the 2022 RSWDM.
Core Requirement #1 Discharge at a natural location
The existing stormwater drainage discharge locations will be maintained.
Core Requirement #2 Offsite Analysis
The drainage system of this property will not be impacted by offsite flows –all offsite
flows are being routed around the on-site stormwater management system. Offsite
analysis is presented in 3.0 Offsite Analysis (Level 1 Downstream)
Core Requirement #3 Flow Control
Flow control is provided by a detention vault with a combined volume of 27,000 CF. See
4.4 Flow Control System for more information.
Core Requirement #4 Conveyance System
Conveyance analysis will be provided with the final TIR.
Core Requirement #5 Erosion and Sediment Control
A Construction Stormwater Pollution Prevention Plan (CSWPPP) is included with this
submittal and is under a separate cover.
Core Requirement #6 Maintenance and Operations
An On-site Stormwater Management Operations and Maintenance Manual is included in
this submittal and is provided under a separate cover.This system will be privately
maintained.
Core Requirement #7 Financial Guarantees and Liability
Does not apply for this project.
Core Requirement #8 Water Quality
This project is in the basic water quality treatment area, but is fully commercial uses.
Therefore, the enhanced water quality treatment menu is used. A modular wetland is
proposed post-detention to provide enhanced treatment.See Section 4.5 Water
Quality System for more info.
Core Requirement #9 Flow Control BMPs
Flow control BMP’s are not implemented for this project –A detention vault has been
designed for detain and release flow control.
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Special Requirement #1 Other Adopted Area-Specific Requirements
No other area-specific requirements are identified.
Special Requirement #2 Floodplain/Floodway Analysis
No flood hazard areas are located on or adjacent to the project site.
Special Requirement #3 Flood Protection Facilities
No flood protection facilities are proposed or required.
Special Requirement #4 Source Control
Source control BMP’s will be implemented as detailed in the O&M Manual, to be
provided with the final SSP.
Special Requirement #5 Oil Control
Oil control is not required for this project, but an oil-water separator is provided for the
runoff from the fuel pumps.
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3.0 OFFSITE ANALYSIS (LEVEL 2 DOWNSTREAM)
3.1 Define and Map Study Area
The parcel contains an underground storm drainage system that collects and conveys
stormwater runoff from the existing buildings and parking lot off-site to the south, to the
storm system in SE Petrovitsky RD. From there, it travels north along Benson DR S, and
then along SE 174th Street. It is conveyed until it is discharged into a forested area on
Parcel 810630TR-B per City of Renton GIS.This forested parcel is approximately 2,000
feet (0.38 miles) downstream from the site.
3.2 Review All Available Information of the Study Area
All available information regarding existing and potential water quality, runoff volumes
and rates, flooding and stream bank erosion problems within the study area have been
reviewed.Reviewed material included NRSC soil information,and City of Renton GIS.
See Appendix A for the delineated study area.
3.3 Field Inspect the Study Area
The field inspection of the site was conducted on 8/4/2022. There were no recognizable
issues with the roadway drainage systems, and any birdcage manholes found along the
way appeared to be free of debris and clogging. The downstream path was tracked
from the project site to parcel 810630TR-B and appears fully functional.
3.4 Existing and Predicted Drainage and Water Quality Issues
There are no predicted downstream drainage concerns. Enhanced treatment and oil
control is being provided on site, but there are no known water quality concerns in the
city system.
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4.0 FLOW CONTROL,LOW IMPACT DEVELOPMENT (LID)AND WATER
QUALITY FACILITY ANALYSIS AND DESIGN
4.1 Existing Site Hydrology
The parcel contains an underground storm drainage system that collects and conveys
stormwater runoff from the existing buildings and parking lot off-site to the south, to the
storm system in SE Petrovitsky RD. From there, it travels north along Benson DR S, and
then along SE 174th Street. It is conveyed until it is discharged into a forested area on
Parcel 810630TR-B per City of Renton GIS.This forested parcel is approximately 2,000
feet (0.38 miles) downstream from the site.
4.2 Developed Site Hydrology
See Section 1.4,Developed Conditions. See also the Plan Exhibits in Appendix B.
4.3 Performance Standards
The 2022 City of Renton Surface Water Design Manual established the methodology
and design criteria used for this project.
4.4 Flow Control System
A detention vault with a volume of 27,000 CF is proposed for this project.It is located
under the parking lot in front of the proposed Chase Bank.It discharges to the city
storm system via a pump system.See the design information for this vault below.
Stormwater Vault
Vault Bottom Elevation =394.00
Top of Sediment Storage =394.50
Design Water Surface =401.50 (7’depth)
Vault Inside Top Elevation =402.00 (0.5’ freeboard)
Vault Design Storage Volume (@401.50)=27,000 CF
Control Structure
Top of Riser Elev.=401.50
Riser Diameter = 18”
Restrictor Plate Orifice Diameter = 0.6”
Restrictor Plate Orifice Height = 394.50
Orifice #2 Diameter =0.25”
Orifice #2 Height = 397.50
Orifice #3 Diameter = 0.125”
Orifice #3 Height = 399.50
See Appendix C for WWHM calculations associated with the detention vault.
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4.5 Water Quality System
Basic treatment is required for this project.Basic treatment is being provided for the
stormwater being discharged from the detention vault by one Bayfilter water quality
system.Since water quality is proposed downstream from detention,the full 2-year
release rate from the detention facility from WWHM is being utilized to size the facility.
The two year release rate is 0.02 CFS –so a treatment rate of 8.976 GPM is required.
One Bayfilter 522 cartridge has the capacity for 22.5 GPM treatment, so one cartridge is
fulfilling this requirement.
5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN
A downstream conveyance system analysis has been conducted and is included in
Section 3.0 Offsite Analysis
6.0 SPECIAL REPORTS AND STUDIES
No special reports or studies are required for this project.
7.0 OTHER PERMITS
A demolition permit will be required for the existing improvements.
8.0 CSWPP PLAN ANALYSIS AND DESIGN
The full submittal will include CSWPPP and TESC plans meeting this requirement.
9.0 BOND QUANTITIES,FACILITY SUMMARIES &DECLARATION OF
COVENANT
Bond quantities are not required for this project.
10.0 OPERATIONS AND MAINTENANCE MANUAL
The full submittal will include an Operations and Maintenance Manual is included with
this submittal.
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APPENDIX A
General Exhibits
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Soil Map—King County Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/2/2022
Page 1 of 3525494052549505254960525497052549805254990525500052550105255020525503052550405255050525506052550705255080525494052549505254960525497052549805254990525500052550105255020525503052550405255050525506052550705255080560550560560560570560580560590560600560610560620560630560640560650
560550 560560 560570 560580 560590 560600 560610 560620 560630 560640 560650
47° 26' 47'' N 122° 11' 49'' W47° 26' 47'' N122° 11' 43'' W47° 26' 42'' N
122° 11' 49'' W47° 26' 42'' N
122° 11' 43'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84
0 35 70 140 210
Feet
0 10 20 40 60
Meters
Map Scale: 1:734 if printed on A portrait (8.5" x 11") sheet.
Soil Map may not be valid at this scale.
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MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: King County Area, Washington
Survey Area Data: Version 17, Aug 23, 2021
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jul 25, 2020—Jul 27,
2020
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Soil Map—King County Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/2/2022
Page 2 of 3
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Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
AmB Arents, Alderwood material, 0
to 6 percent slopes
0.4 17.8%
AmC Arents, Alderwood material, 6
to 15 percent slopes
1.9 82.2%
Totals for Area of Interest 2.3 100.0%
Soil Map—King County Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/2/2022
Page 3 of 3
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King County Area, Washington
AmC—Arents, Alderwood material, 6 to 15 percent slopes
Map Unit Setting
National map unit symbol: 1hmsq
Elevation: 50 to 660 feet
Mean annual precipitation: 35 to 60 inches
Mean annual air temperature: 50 degrees F
Frost-free period: 150 to 200 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Arents, alderwood material, and similar soils:100 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Arents, Alderwood Material
Setting
Landform:Till plains
Parent material:Basal till
Typical profile
H1 - 0 to 26 inches: gravelly sandy loam
H2 - 26 to 60 inches: very gravelly sandy loam
Properties and qualities
Slope:6 to 15 percent
Depth to restrictive feature:20 to 40 inches to densic material
Drainage class:Moderately well drained
Capacity of the most limiting layer to transmit water (Ksat):Very low
to moderately low (0.00 to 0.06 in/hr)
Depth to water table:About 16 to 36 inches
Frequency of flooding:None
Frequency of ponding:None
Available water supply, 0 to 60 inches: Very low (about 2.3 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 4s
Hydrologic Soil Group: B/D
Hydric soil rating: No
Data Source Information
Soil Survey Area: King County Area, Washington
Survey Area Data: Version 17, Aug 23, 2021
Map Unit Description: Arents, Alderwood material, 6 to 15 percent slopes---King County Area,
Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/2/2022
Page 1 of 1
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10'-0" FULLY LANDSCAPE BUFFER9
7
5
7
6
c
10
c
c
c
c
c
ALTERNATE TANK
LOCATIONPROPOSED PROP. LINE4 ISLAND STACKED
36' X 53' CANOPY
3+1
DSL 3+1
DSL
GRAPHIC SCALE
1 INCH = 50 FEET (8.5x11)
0 25 50 100
PHYSICAL ADDRESS: 4706 97TH ST NW, SUITE 100
GIG HARBOR, WA 98332
MAILING ADDRESS: P.O. BOX 949,
GIG HARBOR, WA 98335
PHONE: (253) 857-5454
EXHIBIT NO.
DATE:
PROJECT:
DRAWN BY:J. RAUSCH
19-045
2022.08.02
1
BASIN MAP
BENSON & PETROVITSKY
CITY OF RENTON, KING COUNTY, WASHINGTON
BASIN AREAS
PAVEMENT AREA=33,720 SF
ROOF AREA=9,144 SF
SIDEWALK AREA=4,841 SF
PERVIOUS AREA=16,138 SF
TOTAL SITE AREA=63,843 SF
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APPENDIX B
Downstream Analysis
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9,028
752
WGS_1984_Web_Mercator_Auxiliary_Sphere
City of Renton Print map Template
This map is a user generated static output from an Internet mapping site and
is for reference only. Data layers that appear on this map may or may not be
accurate, current, or otherwise reliable.
THIS MAP IS NOT TO BE USED FOR NAVIGATION
Notes
None
Legend
512 0 256 512 Feet
Information Technology - GIS
RentonMapSupport@Rentonwa.gov
08/08/2022
City and County Labels
Parcels
City and County Boundary
<all other values>
Renton
Water Gravity Pipe
Water Main
Water Main - Other System
Pump Station
Discharge Point
Surface Water Main
Culvert
Open Drains
Facility Outline
Streets
Parks
Waterbodies
2021.sid
Red: Band_1
Green: Band_2
Blue: Band_3
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APPENDIX C
Flow Control and Water Quality Calculations
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WWHM2012
PROJECT REPORT
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General Model Information
Project Name:19-045-Detention
Site Name:
Site Address:
City:
Report Date:8/4/2022
Gage:Seatac
Data Start:1948/10/01
Data End:2009/09/30
Timestep:15 Minute
Precip Scale:1.000
Version Date:2021/08/18
Version:4.2.18
POC Thresholds
Low Flow Threshold for POC1:50 Percent of the 2 Year
High Flow Threshold for POC1:50 Year
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Landuse Basin Data
Predeveloped Land Use
Basin 1
Bypass:No
GroundWater:No
Pervious Land Use acre
C, Forest, Flat 1.465
Pervious Total 1.465
Impervious Land Use acre
Impervious Total 0
Basin Total 1.465
Element Flows To:
Surface Interflow Groundwater
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Mitigated Land Use
Basin 1
Bypass:No
GroundWater:No
Pervious Land Use acre
C, Lawn, Flat 0.37
Pervious Total 0.37
Impervious Land Use acre
ROADS FLAT 0.822
ROOF TOPS FLAT 0.162
SIDEWALKS FLAT 0.111
Impervious Total 1.095
Basin Total 1.465
Element Flows To:
Surface Interflow Groundwater
Vault 2 Vault 2
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Routing Elements
Predeveloped Routing
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Mitigated Routing
Vault 2
Width:30 ft.
Length:130 ft.
Depth:8 ft.
Discharge Structure
Riser Height:7 ft.
Riser Diameter:18 in.
Orifice 1 Diameter:0.6 in.Elevation:0 ft.
Orifice 2 Diameter:0.25 in.Elevation:3 ft.
Orifice 3 Diameter:0.125 in.Elevation:5 ft.
Element Flows To:
Outlet 1 Outlet 2
Vault Hydraulic Table
Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs)
0.0000 0.089 0.000 0.000 0.000
0.0889 0.089 0.008 0.002 0.000
0.1778 0.089 0.015 0.004 0.000
0.2667 0.089 0.023 0.005 0.000
0.3556 0.089 0.031 0.005 0.000
0.4444 0.089 0.039 0.006 0.000
0.5333 0.089 0.047 0.007 0.000
0.6222 0.089 0.055 0.007 0.000
0.7111 0.089 0.063 0.008 0.000
0.8000 0.089 0.071 0.008 0.000
0.8889 0.089 0.079 0.009 0.000
0.9778 0.089 0.087 0.009 0.000
1.0667 0.089 0.095 0.010 0.000
1.1556 0.089 0.103 0.010 0.000
1.2444 0.089 0.111 0.010 0.000
1.3333 0.089 0.119 0.011 0.000
1.4222 0.089 0.127 0.011 0.000
1.5111 0.089 0.135 0.012 0.000
1.6000 0.089 0.143 0.012 0.000
1.6889 0.089 0.151 0.012 0.000
1.7778 0.089 0.159 0.013 0.000
1.8667 0.089 0.167 0.013 0.000
1.9556 0.089 0.175 0.013 0.000
2.0444 0.089 0.183 0.014 0.000
2.1333 0.089 0.191 0.014 0.000
2.2222 0.089 0.199 0.014 0.000
2.3111 0.089 0.206 0.014 0.000
2.4000 0.089 0.214 0.015 0.000
2.4889 0.089 0.222 0.015 0.000
2.5778 0.089 0.230 0.015 0.000
2.6667 0.089 0.238 0.016 0.000
2.7556 0.089 0.246 0.016 0.000
2.8444 0.089 0.254 0.016 0.000
2.9333 0.089 0.262 0.016 0.000
3.0222 0.089 0.270 0.017 0.000
3.1111 0.089 0.278 0.017 0.000
3.2000 0.089 0.286 0.018 0.000
3.2889 0.089 0.294 0.018 0.000
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3.3778 0.089 0.302 0.019 0.000
3.4667 0.089 0.310 0.019 0.000
3.5556 0.089 0.318 0.019 0.000
3.6444 0.089 0.326 0.020 0.000
3.7333 0.089 0.334 0.020 0.000
3.8222 0.089 0.342 0.020 0.000
3.9111 0.089 0.350 0.020 0.000
4.0000 0.089 0.358 0.021 0.000
4.0889 0.089 0.366 0.021 0.000
4.1778 0.089 0.374 0.021 0.000
4.2667 0.089 0.382 0.022 0.000
4.3556 0.089 0.390 0.022 0.000
4.4444 0.089 0.397 0.022 0.000
4.5333 0.089 0.405 0.022 0.000
4.6222 0.089 0.413 0.023 0.000
4.7111 0.089 0.421 0.023 0.000
4.8000 0.089 0.429 0.023 0.000
4.8889 0.089 0.437 0.023 0.000
4.9778 0.089 0.445 0.024 0.000
5.0667 0.089 0.453 0.024 0.000
5.1556 0.089 0.461 0.024 0.000
5.2444 0.089 0.469 0.025 0.000
5.3333 0.089 0.477 0.025 0.000
5.4222 0.089 0.485 0.025 0.000
5.5111 0.089 0.493 0.025 0.000
5.6000 0.089 0.501 0.026 0.000
5.6889 0.089 0.509 0.026 0.000
5.7778 0.089 0.517 0.026 0.000
5.8667 0.089 0.525 0.026 0.000
5.9556 0.089 0.533 0.027 0.000
6.0444 0.089 0.541 0.027 0.000
6.1333 0.089 0.549 0.027 0.000
6.2222 0.089 0.557 0.027 0.000
6.3111 0.089 0.565 0.028 0.000
6.4000 0.089 0.573 0.028 0.000
6.4889 0.089 0.581 0.028 0.000
6.5778 0.089 0.588 0.028 0.000
6.6667 0.089 0.596 0.029 0.000
6.7556 0.089 0.604 0.029 0.000
6.8444 0.089 0.612 0.029 0.000
6.9333 0.089 0.620 0.029 0.000
7.0222 0.089 0.628 0.082 0.000
7.1111 0.089 0.636 0.617 0.000
7.2000 0.089 0.644 1.434 0.000
7.2889 0.089 0.652 2.405 0.000
7.3778 0.089 0.660 3.417 0.000
7.4667 0.089 0.668 4.357 0.000
7.5556 0.089 0.676 5.128 0.000
7.6444 0.089 0.684 5.680 0.000
7.7333 0.089 0.692 6.045 0.000
7.8222 0.089 0.700 6.457 0.000
7.9111 0.089 0.708 6.796 0.000
8.0000 0.089 0.716 7.118 0.000
8.0889 0.089 0.724 7.427 0.000
8.1778 0.000 0.000 7.723 0.000
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Analysis Results
POC 1
+ Predeveloped x Mitigated
Predeveloped Landuse Totals for POC #1
Total Pervious Area:1.465
Total Impervious Area:0
Mitigated Landuse Totals for POC #1
Total Pervious Area:0.37
Total Impervious Area:1.095
Flow Frequency Method:Log Pearson Type III 17B
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period Flow(cfs)
2 year 0.043072
5 year 0.067647
10 year 0.081573
25 year 0.096327
50 year 0.105457
100 year 0.113223
Flow Frequency Return Periods for Mitigated. POC #1
Return Period Flow(cfs)
2 year 0.020247
5 year 0.028103
10 year 0.034328
25 year 0.04347
50 year 0.051286
100 year 0.060034
Annual Peaks
Annual Peaks for Predeveloped and Mitigated. POC #1
Year Predeveloped Mitigated
1949 0.042 0.017
1950 0.053 0.022
1951 0.095 0.029
1952 0.030 0.015
1953 0.024 0.021
1954 0.037 0.018
1955 0.059 0.017
1956 0.047 0.025
1957 0.038 0.018
1958 0.043 0.020
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1959 0.037 0.018
1960 0.064 0.025
1961 0.036 0.022
1962 0.023 0.015
1963 0.031 0.020
1964 0.041 0.022
1965 0.029 0.023
1966 0.028 0.020
1967 0.059 0.022
1968 0.037 0.019
1969 0.036 0.019
1970 0.029 0.021
1971 0.032 0.020
1972 0.071 0.027
1973 0.032 0.024
1974 0.035 0.020
1975 0.047 0.017
1976 0.034 0.019
1977 0.004 0.015
1978 0.030 0.021
1979 0.018 0.014
1980 0.067 0.029
1981 0.027 0.020
1982 0.051 0.024
1983 0.046 0.019
1984 0.028 0.015
1985 0.017 0.015
1986 0.075 0.021
1987 0.066 0.024
1988 0.026 0.017
1989 0.017 0.015
1990 0.138 0.025
1991 0.083 0.026
1992 0.032 0.021
1993 0.033 0.015
1994 0.011 0.013
1995 0.048 0.023
1996 0.101 0.028
1997 0.084 0.083
1998 0.019 0.016
1999 0.079 0.027
2000 0.033 0.021
2001 0.006 0.012
2002 0.036 0.022
2003 0.047 0.018
2004 0.060 0.027
2005 0.043 0.018
2006 0.051 0.026
2007 0.102 0.125
2008 0.132 0.027
2009 0.065 0.023
Ranked Annual Peaks
Ranked Annual Peaks for Predeveloped and Mitigated. POC #1
Rank Predeveloped Mitigated
1 0.1381 0.1252
2 0.1322 0.0829
3 0.1025 0.0290
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4 0.1009 0.0288
5 0.0948 0.0277
6 0.0844 0.0274
7 0.0831 0.0273
8 0.0791 0.0268
9 0.0747 0.0267
10 0.0706 0.0260
11 0.0669 0.0256
12 0.0660 0.0255
13 0.0649 0.0255
14 0.0641 0.0254
15 0.0603 0.0243
16 0.0592 0.0238
17 0.0586 0.0238
18 0.0528 0.0234
19 0.0515 0.0228
20 0.0510 0.0226
21 0.0479 0.0224
22 0.0472 0.0223
23 0.0471 0.0219
24 0.0466 0.0218
25 0.0461 0.0216
26 0.0432 0.0214
27 0.0428 0.0213
28 0.0423 0.0211
29 0.0407 0.0209
30 0.0380 0.0209
31 0.0371 0.0207
32 0.0367 0.0204
33 0.0365 0.0202
34 0.0365 0.0197
35 0.0362 0.0197
36 0.0357 0.0197
37 0.0348 0.0196
38 0.0341 0.0195
39 0.0334 0.0192
40 0.0333 0.0191
41 0.0321 0.0188
42 0.0321 0.0183
43 0.0315 0.0181
44 0.0309 0.0180
45 0.0299 0.0176
46 0.0299 0.0175
47 0.0295 0.0175
48 0.0291 0.0173
49 0.0285 0.0170
50 0.0280 0.0167
51 0.0268 0.0158
52 0.0261 0.0154
53 0.0242 0.0154
54 0.0225 0.0154
55 0.0191 0.0152
56 0.0181 0.0151
57 0.0170 0.0149
58 0.0169 0.0148
59 0.0112 0.0137
60 0.0060 0.0133
61 0.0041 0.0121
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Duration Flows
The Facility PASSED
Flow(cfs)Predev Mit Percentage Pass/Fail
0.0215 17562 15503 88 Pass
0.0224 16164 12429 76 Pass
0.0232 14964 9180 61 Pass
0.0241 13858 6451 46 Pass
0.0249 12816 5108 39 Pass
0.0258 11813 3662 30 Pass
0.0266 10900 2843 26 Pass
0.0275 10123 1794 17 Pass
0.0283 9388 1176 12 Pass
0.0292 8733 511 5 Pass
0.0300 8145 160 1 Pass
0.0309 7593 154 2 Pass
0.0317 7063 150 2 Pass
0.0326 6590 148 2 Pass
0.0334 6147 144 2 Pass
0.0343 5777 143 2 Pass
0.0351 5435 138 2 Pass
0.0359 5101 137 2 Pass
0.0368 4808 134 2 Pass
0.0376 4524 131 2 Pass
0.0385 4254 126 2 Pass
0.0393 4017 122 3 Pass
0.0402 3784 120 3 Pass
0.0410 3546 119 3 Pass
0.0419 3337 114 3 Pass
0.0427 3138 112 3 Pass
0.0436 2952 112 3 Pass
0.0444 2785 106 3 Pass
0.0453 2597 104 4 Pass
0.0461 2449 101 4 Pass
0.0470 2304 97 4 Pass
0.0478 2160 93 4 Pass
0.0487 2025 91 4 Pass
0.0495 1900 91 4 Pass
0.0504 1790 86 4 Pass
0.0512 1688 83 4 Pass
0.0521 1585 83 5 Pass
0.0529 1483 79 5 Pass
0.0537 1381 77 5 Pass
0.0546 1292 73 5 Pass
0.0554 1218 72 5 Pass
0.0563 1154 70 6 Pass
0.0571 1098 66 6 Pass
0.0580 1048 61 5 Pass
0.0588 997 59 5 Pass
0.0597 930 51 5 Pass
0.0605 883 45 5 Pass
0.0614 837 40 4 Pass
0.0622 789 37 4 Pass
0.0631 743 35 4 Pass
0.0639 713 32 4 Pass
0.0648 668 29 4 Pass
0.0656 630 28 4 Pass
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0.0665 595 23 3 Pass
0.0673 565 22 3 Pass
0.0682 539 21 3 Pass
0.0690 497 17 3 Pass
0.0699 473 16 3 Pass
0.0707 434 14 3 Pass
0.0715 399 14 3 Pass
0.0724 366 14 3 Pass
0.0732 348 14 4 Pass
0.0741 323 14 4 Pass
0.0749 296 11 3 Pass
0.0758 272 11 4 Pass
0.0766 256 11 4 Pass
0.0775 235 11 4 Pass
0.0783 217 9 4 Pass
0.0792 195 9 4 Pass
0.0800 180 9 5 Pass
0.0809 158 9 5 Pass
0.0817 145 7 4 Pass
0.0826 129 6 4 Pass
0.0834 119 4 3 Pass
0.0843 109 4 3 Pass
0.0851 97 4 4 Pass
0.0860 91 4 4 Pass
0.0868 82 4 4 Pass
0.0877 76 4 5 Pass
0.0885 69 4 5 Pass
0.0894 61 4 6 Pass
0.0902 54 4 7 Pass
0.0910 48 4 8 Pass
0.0919 41 4 9 Pass
0.0927 38 4 10 Pass
0.0936 33 3 9 Pass
0.0944 27 3 11 Pass
0.0953 22 3 13 Pass
0.0961 21 3 14 Pass
0.0970 20 3 15 Pass
0.0978 19 3 15 Pass
0.0987 17 3 17 Pass
0.0995 13 3 23 Pass
0.1004 12 3 25 Pass
0.1012 9 3 33 Pass
0.1021 4 3 75 Pass
0.1029 3 3 100 Pass
0.1038 3 3 100 Pass
0.1046 3 3 100 Pass
0.1055 3 3 100 Pass
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APPENDIX D
Geotechnical Report (By PanGEO, Dated May 2019)
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Geotechnical & Earthquake
Engineering Consultants
GEOTECHNICAL REPORT
BENSON DRIVE SOUTH AND
SOUTHEAST PETROVITSKY ROAD
Renton, Washington
PROJECT NO. 19-122
May 2019
Prepared for:
TA Renton BP, LLC
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________________________________________________
3213 Eastlake Avenue East, Suite B
Seattle, WA 98102
T. (206) 262-0370
F. (206) 262-0374
Geotechnical & Earthquake
Engineering Consultants
May 13, 2019
PanGEO Project No. 19-122
Ms. Michelle Woodward
TA Renton BP, LLC
2600 North Dallas Parkway, Suite 370
Frisco, Texas 75234
Subject: Geotechnical Report
Proposed Retail Development
Benson Drive South and Southeast Petrovitsky Road
Renton, Washington
Dear Ms. Woodward:
As requested, PanGEO, Inc. is pleased to present this geotechnical report to assist the
project team with the design and construction of the proposed retail development located
in the northeast corner of the intersection of Benson Drive South and Southeast Petrovitsky
Road in Renton, Washington.
In preparing this report, we observed and logged the drilling of eight test borings at the site
and conducted our engineering analyses. In summary, our test borings encountered up to
about 4 feet of fill overlying glacially consolidated soils and highly weathered bedrock.
In our opinion, the proposed buildings may be supported on spread footings bearing on
competent native soils or on structural fill placed on competent native soils.
We appreciate the opportunity to be of service. Should you have any questions, please do
not hesitate to call.
Sincerely,
Scott D. Dinkelman, LEG
Senior Engineering Geologist
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TABLE OF CONTENTS
Section Page
1.0 GENERAL .................................................................................................................1
2.0 SITE AND PROJECT DESCRIPTION .....................................................................1
3.0 SUBSURFACE EXPLORATIONS ...........................................................................3
3.1 SITE GEOLOGY ................................................................................................3
3.2 SUBSURFACE EXPLORATION ...........................................................................3
3.3 SOIL CONDITIONS............................................................................................4
3.4 GROUNDWATER ..............................................................................................5
4.0 INFILTRATION CONSIDERATIONS ....................................................................6
5.0 GEOTECHNICAL RECOMMENDATIONS ...........................................................6
5.1 SEISMIC DESIGN PARAMETERS ........................................................................6
5.2 BUILDING FOUNDATIONS ................................................................................7
5.2.1 Lateral Resistance ...........................................................................8
5.2.2 Perimeter Footing Drains ...............................................................8
5.2.3 Footing Subgrade Preparation .......................................................9
5.3 FLOORS SLABS ................................................................................................9
5.4 RETAINING WALL DESIGN PARAMETERS ........................................................10
5.4.1 Lateral Earth Pressures ..................................................................10
5.4.2 Surcharge ........................................................................................10
5.4.3 Lateral Resistance ...........................................................................10
5.4.4 Wall Drainage .................................................................................11
5.4.5 Wall Backfill....................................................................................11
5.5 PERMANENT CUT AND FILL SLOPES ................................................................11
6.0 EARTHWORK CONSIDERATIONS .......................................................................12
6.1 STRIPPING, CLEARING AND SUBGRADE PREPARATION ....................................12
6.2 PERCHED SEEPAGE CONTROL .........................................................................12
6.3 TEMPORARY EXCAVATIONS AND SHORING .....................................................13
6.4 MATERIAL REUSE ...........................................................................................13
6.5 STRUCTURAL FILL AND COMPACTION .............................................................13
6.6 WET WEATHER CONSTRUCTION .....................................................................14
6.7 EROSION CONSIDERATIONS .............................................................................15
7.0 ADDITIONAL SERVICES .......................................................................................16
8.0 CLOSURE .................................................................................................................16
9.0 REFERENCES ...........................................................................................................18
ATTACHMENTS:
Figure 1 Vicinity Map
Figure 2 Site and Exploration Plan
Appendix A Boring Logs
Figures A-1 and A-1a Terms and Symbols for Boring and Test Pit Logs
Figures A-2 to A-9 Logs of Test Borings PG-1 through PG-8
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GEOTECHNICAL REPORT
PROPOSED RETAIL DEVELOPMENT
BENSON DRIVE SOUTH AND SOUTHEAST PETROVITSKY ROAD
RENTON, WASHINGTON
1.0 GENERAL
As requested, PanGEO is pleased to present this geotechnical report for the proposed retail
development to be located northeast corner of the Benson Drive South and Southeast
Petrovitsky Road in Renton, Washington. This study was performed in general accordance
with our mutually agreed scope of services outlined in our proposal dated April 12, 2019.
Our scope of services included reviewing readily available geologic and geotechnical data,
drilling eight borings, conducting a site reconnaissance, and preparing this report.
2.0 SITE AND PROJECT DESCRIPTION
The subject is comprised of three separate parcels located at 17426 Benson Drive South,
10810 Southeast Petrovitsky Road and 10828 Southeast Petrovitsky Road in the northeast
corner of the intersection of Benson Drive South and Southeast Petrovitsky Road in
Renton, Washington. The approximate location of the site is shown on Figure 1, Vicinity
Map.
The three parcels have an aggregate area of approximately 1.67 acres. The layout of the
site is shown on Figure 2, Site and Exploration Plan. Plate 1, below shows an aerial view
of the site. The approximately L-shaped property is bordered to the northwest by a two-
story office building, to the north by a single-story church, to the east by two single-story
office buildings, to the west by Benson Drive South, and to the south by Southeast
Petrovitsky Road. The site slopes down from east to west, with about 8 feet of elevation
change across the approximate 300-foot length of the site.
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Geotechnical Report
Proposed Retail Development: Benson Drive S and SE Petrovitsky Road, Renton, WA
May 13, 2019
19-122 Benson Drive and Petrovitsky Road Page 2 PanGEO, Inc.
Plate 1: Aerial view
of the site.
Benson Drive is
along the left side of
photo. Southeast
Petrovitsky Road is
along the bottom.
(Bing Maps)
Plate 2: View from
northwest corner of
the site looking site to
the south-southeast.
The site is currently developed with three one-story buildings that are vacant or being used
as offices. We understand it is planned to demolish the existing structures and redevelop
the site with a bank building, a convenience store with a detached fueling island, and three
retail buildings. The proposed development layout is shown on Figure 2.
The proposed buildings will be one-story in height and will be constructed at or near
existing site grades and we anticipate cuts and fills of less than five feet will be required to
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Geotechnical Report
Proposed Retail Development: Benson Drive S and SE Petrovitsky Road, Renton, WA
May 13, 2019
19-122 Benson Drive and Petrovitsky Road Page 3 PanGEO, Inc.
achieve construction subgrade elevations. The proposed buildings will be surrounded by
asphalt paved parking and drive areas.
The conclusions and recommendations in this report are based on our understanding of the
proposed development, which is in turn based on the project information provided. If the
above project description is incorrect, or the project information changes, we should be
consulted to review the recommendations contained in this study and make modifications,
if needed. In any case PanGEO should be retained to provide a review of the final design
to confirm that our geotechnical recommendations have been correctly interpreted and
adequately implemented in the construction documents.
3.0 SUBSURFACE EXPLORATIONS
3.1 SITE GEOLOGY
General geologic information for the project area was obtained by reviewing the Geologic
Map of the Renton Quadrangle, King County, Washington (Mullineaux, 1965) and the
Geologic Map of the Tacoma 1:100,000-scale Quadrangle, Washington (Schuster et al,
2015). Based on our review, the geologic units in the vicinity of the site consist of Vashon
till – Geologic Map Unit Qgt, with Renton Formation sedimentary units mapped nearby –
Geologic Map Unit Ec2pg.
Vashon till is described as consisting of an unsorted deposit (diamict) of clay, silt, sand and
gravel that has been glacially transported and deposited. This soil has been directly
deposited by a glacier and overridden by several thousand feet of glacial ice and is typically
dense to very dense.
The Renton Formation sedimentary unit is locally classified as part of the Puget Group and
described as an interbedded sedimentary rock consisting of sandstone, siltstone, shale,
claystone, carbonaceous shale and coal beds. This unit is considered the bedrock unit in
this area.
3.2 SUBSURFACE EXPLORATION
We drilled and logged eight borings at the site on April 23, 2019. The borings were drilled
using a track-mounted EC95 drill rig owned and operated by Boretec Drilling, Inc. under
subcontract to PanGEO and were logged by a geologist with our firm. The borings were
drilled to a maximum depth of about 16 feet below existing grade. The approximate boring
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Geotechnical Report
Proposed Retail Development: Benson Drive S and SE Petrovitsky Road, Renton, WA
May 13, 2019
19-122 Benson Drive and Petrovitsky Road Page 4 PanGEO, Inc.
locations were located in the field by measuring from property corners and site features
and are shown on Figure 2, Site and Exploration Plan.
Standard Penetration Tests (SPT) were performed at 2½- to 5-foot depth intervals using a
standard, 2-inch diameter split-spoon sampler. The sampler was advanced with a 140-
pound drop hammer falling a distance of 30 inches for each strike, in general accordance
with ASTM D1586, Standard Test Method for Penetration Test and Split Barrel Sampling
of Soils.
The soils were logged in general accordance with ASTM D2487 Standard Practice for
Classification of Soils for Engineering Purposes and the system summarized on Figure A-
1 and Figure A-1a, Terms and Symbols for Boring and Test Pit Logs.
3.3 SOIL CONDITIONS
For a detailed description of the subsurface conditions encountered at each exploration
location, please refer to our boring logs provided in Appendix A. The stratigraphic contacts
indicated on the boring logs represent the approximate depth to boundaries between soil
units. Actual transitions between soil units may be more gradual or occur at different
elevations. The descriptions of groundwater conditions and depths are likewise
approximate. The following is a generalized description of the soils encountered in the
borings.
Asphalt: Test borings PG-1, PG-2, PG-5, PG-6, PG-7 and PG-8 were located in
asphalt paved parking and drive areas. At these locations we encountered between
two and five inches of asphalt surfacing.
Topsoil: Borings PG-3 and PG-4 were located outside of paved areas. In these areas,
we encountered a surficial layer of topsoil comprised of about six inches of silty sand
with organics and roots.
Fill: Below the asphalt at the locations of PG-1, PG-5, PG-7 and PG-8, we
encountered fill. The fill generally consisted of a few inches of gravel over sandy silt
with varying amounts of gravel and cobbles. This unit ranged from 2½ to 4½ feet
thick. The approximate fill thicknesses are identified on the boring logs and on Figure
2.
Weathered Vashon Till (Qgt): The native soil below the fill and in areas where fill
was not encountered consists of medium dense to very dense silty fine to medium sand
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Geotechnical Report
Proposed Retail Development: Benson Drive S and SE Petrovitsky Road, Renton, WA
May 13, 2019
19-122 Benson Drive and Petrovitsky Road Page 5 PanGEO, Inc.
with gravel and which we classified as Vashon Till. At the base of this unit, from
approximately 10 to 14 feet below grade, the till graded to dense to very dense.
Perched groundwater was encountered throughout this unit.
The Vashon till encountered at our boring locations is consistent with the geologic
mapping of this area. Test borings PG-4 and PG-6 were terminated in this unit.
Renton Formation (Ec2pg): With the exception of borings PG-4 and PG-6, all of our
other test borings encountered a hard sandy silt with gravel below the weathered
Vashon Till. We classified the hard silt as the Renton Formation (bedrock). The
Renton Formation was identifiable with the increase in coal fragments present in the
samples. This unit is highly weathered to a residual soil (relative weathering RVI) at
the top and graded to less weathered with depth.
The Renton Formation encountered at our boring locations is consistent with the upper
unit of the Puget Group mapping of the region. In test boring PG-1 this unit was only
slightly weathered at approximately 13 feet (relative weathering RII) and in test boring
PG-7 this unit was highly weathered at approximately 15 feet (relative weathering
RIV). Test borings PG-2, PG-3, PG-5, and PG-8 terminated in the residual soil
(relative weathering RVI) portion of this unit.
Our subsurface descriptions are based on the conditions encountered at the time of our
exploration. Soil conditions between our exploration locations may vary from those
encountered. The nature and extent of variations between our exploratory locations may
not become evident until construction. If variations do appear, PanGEO should be
requested to reevaluate the recommendations in this report and to modify or verify them in
writing prior to proceeding with earthwork and construction.
3.4 GROUNDWATER
Increased soil moisture and light groundwater seepage was encountered beginning at
approximately 4 feet below grade during drilling. This moisture is likely perched
groundwater that has developed in lenses of highly permeable soil within the weathered till
formation. If seepage is encountered, we anticipate seepage rates will be light to moderate.
Groundwater levels will change depending on the season, amount of rainfall, surface water
runoff, and other factors. Generally, the water level is higher and seepage rates are greater
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in the wetter, winter months (typically October through May). During periods of
significant precipitation, perched groundwater may also be present at the fill-till contacts.
4.0 INFILTRATION CONSIDERATIONS
The native soils underlying the site consist of Vashon till, a medium dense to very dense
deposit comprised of clay, silt, sand, and gravel. Till is generally not a suitable receptor
soil for infiltration due to the high fines content and density. Where loosened by
weathering infiltration rates of about ½ inch per hour may be obtained. Where
unweathered, infiltration rates are typically less than 0.1 inch per hour. Perched
groundwater, which can limit infiltration, also develops in till soils during wet season at
the transition from weathered to unweathered soils.
The site is also underlain by a surficial layer of fill. Fill soils are not suitable for infiltration
due to their variable nature and the potential for them to consolidate we wetted, changing
their infiltration characteristics over time.
In summary, it is our opinion that non-infiltration alternatives should be considered to
manage the surface runoff at the site.
5.0 GEOTECHNICAL RECOMMENDATIONS
5.1 SEISMIC DESIGN PARAMETERS
The 2015 International Building Code (IBC) seismic design section provides a basis for
seismic design of structures. Table 1 below provides seismic design parameters for the site
that are in conformance with the 2015 IBC, which specifies a design earthquake having a
2% probability of occurrence in 50 years (return interval of 2,475 years), and the 2008
USGS seismic hazard maps.
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Table 1 – Seismic Design Parameters
The spectral response accelerations were obtained from the USGS Earthquake Hazards
Program Interpolated Probabilistic Ground Motion website (2008 data) for the project
latitude and longitude.
Liquefaction Potential: Liquefaction is a process that can occur when soils lose shear
strength for short periods of time during a seismic event. Ground shaking of sufficient
strength and duration results in the loss of grain-to-grain contact and an increase in pore
water pressure, causing the soil to behave as a fluid. Soils with a potential for liquefaction
are typically cohesionless, predominately silt and sand sized, must be loose, and be below
the groundwater table. The site is predominantly underlain by very dense silty sand with
gravel and hard sandy silt without a defined groundwater table. Based on these conditions,
in our opinion the liquefaction potential of the site is negligible and design considerations
related to soil liquefaction are not necessary for this project.
5.2 BUILDING FOUNDATIONS
Based on the subsurface conditions encountered at the site and our understanding of the
planned development, it is our opinion the proposed buildings may be supported on
conventional footings. The footings should bear on the medium dense to very dense,
undisturbed native soil below the fill, or on properly compacted structural fill placed on
undisturbed native soil.
We encountered up to about 4½ feet of fill at our test boring locations. If fill is encountered
at the foundation subgrade elevation, the fill should be overexcavated and replaced with
properly compacted structural fill. The overexcavation width should extend at least one
foot beyond the width of the foundation elements.
Site
Class
Spectral
Acceleration
at 0.2 sec.
[g]
SS
Spectral
Acceleration
at 1.0 sec.
[g]
S1
Site
Coefficients
Design Spectral
Response
Parameters
Control Periods
[sec.]
Fa Fv SDS SD1 TO TS
C 1.396 0.520 1.000 1.300 0.931 0.451 0.096 0.484
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Exterior foundation elements should be placed at a minimum depth of 18 inches below
final exterior grade. Interior spread foundations should be placed at a minimum depth of
12 inches below the top of concrete slabs.
A maximum allowable soil bearing pressure of 3,000 pounds per square foot (psf) should
be used for sizing foundation elements bearing on dense to very dense native soil, or on
structural fill. PanGEO should be retained to determine the adequacy of footing subgrade
during construction.
The recommended allowable soil bearing pressure is for dead plus live loads. For
allowable stress design, the recommended bearing pressure may be increased by one-third
for transient loading, such as wind or seismic forces. Continuous and individual spread
footings should have minimum widths of 18 and 24 inches, respectively.
Footings designed and constructed in accordance with the above recommendations should
experience total settlement of less than one inch and differential settlement of less than ½
inch. Most of the anticipated settlement should occur during construction as dead loads
are applied.
5.2.1 Lateral Resistance
Lateral loads on the structure may be resisted by passive earth pressure developed against
the embedded portion of the foundation system and by frictional resistance between the
bottom of the foundation and the supporting subgrade soils. For footings bearing on the
dense to very dense silty sand, a frictional coefficient of 0.35 may be used to evaluate
sliding resistance developed between the concrete and the subgrade soil. Passive soil
resistance may be calculated using an equivalent fluid weight of 350 pcf, assuming
foundations are backfilled with structural fill. The above values include a factor of safety
of 1.5. Unless covered by pavements or slabs, the passive resistance in the upper 12 inches
of soil should be neglected.
5.2.2 Perimeter Footing Drains
Footing drains should be installed around the perimeter of the buildings, at or just below
the invert of the footings. Under no circumstances should roof downspout drain lines be
connected to the footing drain systems. Roof downspouts must be separately tightlined to
appropriate discharge locations. Cleanouts should be installed at strategic locations to
allow for periodic maintenance of the footing drain and downspout tightline systems.
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5.2.3 Footing Subgrade Preparation
At our boring locations, we encountered 2½ to 4½ feet of fill. The fill is variable and would
not be suitable for direct support of foundation loads. If fill is encountered at the foundation
subgrade elevation, the fill should be overexcavated and replaced with structural fill. The
overexcavation width should extend at least one half the overexcavation depth beyond the
width of the foundation elements.
All footing subgrade should be properly prepared and in a dense and unyielding condition
prior to setting forms and placing reinforcing steel. Any loose or softened soil should be
removed from the footing excavations. The adequacy of the footing subgrade soils should
be verified by a representative of PanGEO, prior to placing forms or rebar.
5.3 FLOORS SLABS
The floor slabs for the proposed building may be constructed using conventional concrete
slab-on-grade floor construction. The floor slab should be supported on competent native
soil or on structural fill. Any over-excavations, if needed, should be backfilled with
structural fill.
If the existing fill is encountered in slab-on-grade areas, the fill should be removed to a
depth of 12 inches below the capillary break, the surface compacted to the requirements of
structural fill, and the grade restored using structural fill.
Interior concrete slab-on-grade floors should be underlain by a capillary break consisting
of at least of 4 inches of pea gravel or compacted ¾-inch, clean crushed rock (less than 3
percent fines). The capillary break material should meet the gradational requirements
provided in Table 2, next page.
Table 2 – Capillary Break Gradation
The capillary break should be placed on the subgrade that has been compacted to a dense
and unyielding condition.
Sieve Size Percent Passing
¾-inch 100
No. 4 0 – 10
No. 100 0 – 5
No. 200 0 – 3
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A 10-mil polyethylene vapor barrier should also be placed directly below the slab.
Construction joints should be incorporated into the floor slab to control cracking.
5.4 RETAINING WALL DESIGN PARAMETERS
Retaining walls, if needed, should be designed to resist the lateral earth pressures exerted
by the soils behind the wall. Proper drainage provisions should also be provided behind
the walls to intercept and remove groundwater that may be present behind the wall. Our
geotechnical recommendations for the design and construction of retaining walls are
presented below.
5.4.1 Lateral Earth Pressures
Cantilever walls should be designed for an equivalent fluid pressure of 35 pcf for a level
backfill condition behind the walls assuming the walls are free to rotate. If the walls are
restrained at the top from free movement, such as basement walls with a floor diaphragm,
an equivalent fluid pressure of 45 pcf should be used for a level backfill condition behind
the walls. Permanent walls should be designed for an additional uniform lateral pressure
of 7H psf for seismic loading, where H corresponds to the buried depth of the wall.
The recommended lateral pressures assume the backfill behind the walls consists of a free
draining and properly compacted fill with adequate drainage provisions.
5.4.2 Surcharge
Surcharge loads, where present, should also be included in the design of retaining walls.
We recommend a lateral load coefficient of 0.3 be used to compute the lateral pressure on
the wall face resulting from surcharge loads located within a horizontal distance of one-
half the wall height.
5.4.3 Lateral Resistance
Lateral forces from seismic loading and unbalanced lateral earth pressures may be resisted
by a combination of passive earth pressures acting against the embedded portions of the
foundations and by friction acting on the base of the wall foundation. Passive resistance
values may be determined using an equivalent fluid weight of 350 pcf. This value includes
a factor of safety of 1.5, assuming the footing is backfilled with structural fill. A friction
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coefficient of 0.35 may be used to determine the frictional resistance at the base of the
footings. The coefficient includes a factor of safety of 1.5.
5.4.4 Wall Drainage
Provisions for wall drainage should consist of a 4-inch diameter perforated drainpipe
placed behind and at the base of the wall footings, embedded in 12 to 18 inches of clean
crushed rock or pea gravel wrapped with a layer of filter fabric. A minimum 18-inch wide
zone of free draining granular soils (i.e. pea gravel or washed rock) is recommended to be
placed adjacent to the wall for the full height of the wall. Alternatively, a composite
drainage material, such as Miradrain 6000, may be used in lieu of the clean crushed rock
or pea gravel. The drainpipe at the base of the wall should be graded to direct water to a
suitable outlet.
5.4.5 Wall Backfill
Wall backfill should consist of imported, free draining granular material or a soil meeting
the requirements of Gravel Borrow as defined in Section 9-03.14(1) of the WSDOT
Standard Specifications for Road, Bridge, and Municipal Construction (WSDOT 2014).
In areas where space is limited between the wall and the face of excavation, pea gravel may
be used as backfill without compaction.
In our opinion, the predominately silty sand and sandy silt soils underlying the site are not
suitable for use as wall backfill.
Wall backfill should be moisture conditioned to within about 3 percent of optimum
moisture content, placed in loose, horizontal lifts less than 8 inches in thickness, and
systematically compacted to a dense and relatively unyielding condition and to at least 95
percent of the maximum dry density, as determined using test method ASTM D1557.
Within 5 feet of the wall, the backfill should be compacted with hand-operated equipment
to at least 90 percent of the maximum dry density.
5.5 PERMANENT CUT AND FILL SLOPES
Based on the anticipated soil that will be exposed in the planned excavation, we
recommend permanent cut and fill slopes be constructed no steeper than 2H:1V
(Horizontal:Vertical).
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6.0 EARTHWORK CONSIDERATIONS
6.1 STRIPPING, CLEARING AND SUBGRADE PREPARATION
Foundation and pavement areas, and areas to receive structural fill, should be stripped and
cleared of surface vegetation, organic matter, existing pavements, and other deleterious
materials. In no case should stripped materials be used as structural fill nor should they be
mixed with materials to be used as structural fill. Outside of construction areas, the existing
site pavement may be left in-place to provide an all-weather construction surface.
In areas where existing foundations, slab-on-grade floors, and pavements are removed, it may
be possible to crush the existing materials for re-use as structural fill. Materials reclaimed by
crushing to be re-used as structural fill should have a maximum particle size of four inches
and should be mixed with soil to provide a well-graded fill material.
Existing underground utilities to be abandoned should be plugged or removed so they do not
provide a conduit for water and cause soil saturation and stability problems.
Following the stripping operation and excavations necessary to achieve construction
subgrade elevations, the ground surface where structural fill, or pavements are to be placed
should be observed by PanGEO. Proofrolling using a fully loaded dump truck should be
performed to identify soft or unstable areas.
Soft or yielding areas identified during proofrolling should be moisture conditioned as
needed and re-compacted in place. If soft areas are still yielding after re-compaction, they
should be overexcavated and replaced with structural fill to a depth that will provide a stable
pavement base. The optional use of a geotextile subgrade stabilization fabric, such as
Mirafi 600X, or an equivalent product placed directly on the over-excavated surface may
help to bridge excessively unstable areas.. Overexcavated areas should be and backfilled
with WSDOT 9-03.9(3) Crushed Surfacing Base Course, or WSDOT 9-03.14 (1) Gravel
Borrow (WSDOT, 2018) compacted to the requirements of structural fill. The subgrade
preparation should be observed by an individual experienced with earthwork construction,
to verify the adequacy of the prepared subgrade.
6.2 PERCHED SEEPAGE CONTROL
Perched groundwater was encountered in our borings at four to eleven feet below grade.
The seepage encountered appeared to be perched and likely develops during the wet
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season. Groundwater seepage may be encountered in site excavations, especially deep
excavations, such as for underground utility trenches.
Where seepage is encountered, the base of the excavation should be sloped to one or more
shallow sump pits. The collected water can then be pumped from these pits to a positive
and permanent discharge point. The spacing of the sumps should be determined during
construction based on field observations at the time of construction.
Where loose soils are encountered in conjunction with groundwater seepage the excavation
subgrade bottom may become soft. In these areas, remedial measures such as
overexcavating soft soils or tamping quarry spalls into the base of the excavation may be
required.
6.3 TEMPORARY EXCAVATIONS AND SHORING
Temporary excavations should be constructed in accordance with Part N of WAC
(Washington Administrative Code) 296-155. The contractor is responsible for maintaining
safe excavation slopes and/or shoring. It is our opinion temporary excavations in the fill
soils and underlying native soils may be cut at a maximum 1H:1V inclination.
Temporary excavations should be evaluated in the field during construction based on actual
observed soil conditions. If seepage is encountered, excavation slope inclinations may
need to be reduced. During wet weather, the temporary slopes may need to be flattened to
reduce potential erosion or should be covered with plastic sheeting.
6.4 MATERIAL REUSE
The native soils underlying the site are moisture sensitive, and will become disturbed and
soft when exposed to inclement weather conditions. We do not recommend reusing the
native soils as structural fill. If it is planned to use the native soil in non-structural areas,
the excavated soil should be stockpiled and protected with plastic sheeting to prevent it
from becoming saturated by precipitation or runoff.
6.5 STRUCTURAL FILL AND COMPACTION
Structural fill, should be free of organic and inorganic debris, be near the optimum moisture
content and be capable of being compacted to the recommendations provided below. The
site soils are relatively fine grained and, in our opinion will not be suitable for re-use as
structural fill and an imported structural fill will be needed. Fill for use during wet weather
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should consist of a well graded soil free of organic material with less than 5 percent fines
(silt and clay sized particles passing the U.S. 200 sieve).
Structural fill should be moisture conditioned to within about 3 percent of optimum
moisture content, placed in loose, horizontal lifts less than 8 inches in thickness, and
compacted to at least 95 percent maximum density, determined using ASTM D1557
(Modified Proctor). The procedure to achieve proper density of a compacted fill depends
on the size and type of compacting equipment, the number of passes, thickness of the lifts
being compacted, and certain soil properties. If the excavation to be backfilled is
constricted and limits the use of heavy equipment, smaller equipment can be used, but the
lift thickness will need to be reduced to achieve the required relative compaction.
Generally, loosely compacted soils are a result of poor construction technique or improper
moisture content. Soils with high fines contents are particularly susceptible to becoming
too wet and coarse-grained materials easily become too dry, for proper compaction. Silty
or clayey soils with a moisture content too high for adequate compaction should be dried
as necessary, or moisture conditioned by mixing with drier materials, or other methods.
6.6 WET WEATHER CONSTRUCTION
The wet season in Western Washington typically extends from October through May.
Earthwork during the wet season requires planning and may require the use of imported
wet weather fill materials that can increase earthwork costs. General recommendations
relative to earthwork performed in wet weather or in wet conditions are presented below.
The following procedures are best management practices recommended for use in wet
weather construction:
• Earthwork should be performed in small areas to minimize subgrade exposure
to wet weather. Excavation or the removal of unsuitable soil should be followed
promptly by the placement and compaction of clean structural fill. The size and
type of construction equipment used may have to be limited to prevent soil
disturbance.
• During wet weather, the allowable fines content of the structural fill should be
reduced to no more than 5 percent by weight based on the portion passing the
0.75-inch sieve. The fines should be non-plastic.
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• The ground surface within the construction area should be graded to promote
run-off of surface water and to prevent the ponding of water.
• Geotextile silt fences should be installed at strategic locations around the site to
control erosion and the movement of soil.
• Excavation slopes and soils stockpiled on site should be covered with plastic
sheeting.
6.7 EROSION CONSIDERATIONS
Surface runoff can be controlled during construction by careful grading practices.
Typically, this includes the construction of shallow, upgrade perimeter ditches or low
earthen berms in conjunction with silt fences to collect runoff and prevent water from
entering excavations or to prevent runoff from the construction area leaving the immediate
work site. Temporary erosion control may require the use of hay bales on the downhill
side of the project to prevent water from leaving the site and potential storm water detention
to trap sand and silt before the water is discharged to a suitable outlet. All collected water
should be directed under control to a positive and permanent discharge system.
Permanent control of surface water should be incorporated in the final grading design.
Adequate surface gradients and drainage systems should be incorporated into the design
such that surface runoff is collected and directed away from the structure to a suitable
outlet. Potential issues associated with erosion may also be reduced by establishing
vegetation within disturbed areas immediately following grading operations.
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7.0 ADDITIONAL SERVICES
To confirm that our recommendations are properly incorporated into the design and
construction of the proposed development, PanGEO should be retained to conduct a review
of the final project plans and specifications, and to monitor the construction of geotechnical
elements. PanGEO can provide you a cost estimate for construction monitoring services
at a later date.
8.0 CLOSURE
We have prepared this report for TA Renton BP, LLC and the project design team.
Recommendations contained in this report are based on a site reconnaissance, a subsurface
exploration program, review of pertinent subsurface information, and our understanding of
the project. The study was performed using a mutually agreed-upon scope of services.
Variations in soil conditions may exist between the locations of the explorations and the
actual conditions underlying the site. The nature and extent of soil variations may not be
evident until construction occurs. If any soil conditions are encountered at the site that are
different from those described in this report, we should be notified immediately to review
the applicability of our recommendations. Additionally, we should also be notified to
review the applicability of our recommendations if there are any changes in the project
scope.
The scope of our work does not include services related to construction safety precautions.
Our recommendations are not intended to direct the contractors’ methods, techniques,
sequences or procedures, except as specifically described in our report for consideration in
design. Additionally, the scope of our services specifically excludes the assessment of
environmental characteristics, particularly those involving hazardous substances. We are
not mold consultants nor are our recommendations to be interpreted as being preventative
of mold development. A mold specialist should be consulted for all mold-related issues.
This report has been prepared for planning and design purposes for specific application to
the proposed project in accordance with the generally accepted standards of local practice
at the time this report was written. No warranty, express or implied, is made.
This report may be used only by the client and for the purposes stated, within a reasonable
time from its issuance. Land use, site conditions (both off and on-site), or other factors
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including advances in our understanding of applied science, may change over time and
could materially affect our findings. Therefore, this report should not be relied upon after
24 months from its issuance. PanGEO should be notified if the project is delayed by more
than 24 months from the date of this report so that we may review the applicability of our
conclusions considering the time lapse.
It is the client’s responsibility to see that all parties to this project, including the designer,
contractor, subcontractors, etc., are made aware of this report in its entirety. The use of
information contained in this report for bidding purposes should be done at the contractor’s
option and risk. Any party other than the client who wishes to use this report shall notify
PanGEO of such intended use and for permission to copy this report. Based on the intended
use of the report, PanGEO may require that additional work be performed and that an
updated report be reissued. Noncompliance with any of these requirements will release
PanGEO from any liability resulting from the use this report.
Sincerely,
PanGEO, Inc.
Scott D. Dinkelman, LEG, LHG Siew L Tan, P.E.
Senior Engineering Geologist Principal Geotechnical Engineer
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9.0 REFERENCES
International Code Council, 2015, International Building Code (IBC), 2015.
Mullineaux, D.R., 1965, Geologic Map of the Renton Quadrangle, King County,
Washington – U.S. Geological Survey Geologic, Quadrangle Map GQ-405, scale
1:24,000.
Schuster, J.E., Cabibbo, A.A., Schilter, J.F., and Hubert I.J., 2015, Geologic Map of the
Tacoma 1:100,000-scale Quadrangle, Washington – Washington Division of Geology
and Earth Resources, Map Series 2015-03, scale 1:100,000.
WSDOT, 2018, Standard Specifications for Road, Bridge and Municipal Construction, M
41-10.
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Figure No.Project No.19-122
Proposed Retail Development
Benson Drive South and
Southeast Petrovitsky Road
Renton, WA 1
Base Map: Google Maps
VICINITY MAP
Approx. Scale:
Not to Scale
19-122 Fig 1 - Vicinity Map.grf 4/30/19 (14:00) SPSDocuSign Envelope ID: AA4FA6BA-AA72-4A92-A78C-D1916105F712
Project No. Figure No.SITE AND EXPLORATION PLAN19-122219-122 Fig 2 Site & Exploration Plan.grf 5/9/19 SPSLEGEND:Approx. Scale(feet)Note: Site plan modified from ALTA/NSPS Land Title Survey, prepared by Terrane dated January 11, 2019Proposed Retail DevelopmentBenson Drive South andSoutheast Petrovitsky RoadRenton, WAApproximate Boring Locations,PanGEO, Inc., April 2019(Approximate Thickness of Fill)Approximate ProposedDevelopmentsDocuSign Envelope ID: AA4FA6BA-AA72-4A92-A78C-D1916105F712
APPENDIX A
BORING LOGS
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MOISTURE CONTENT
2-inch OD Split Spoon, SPT
(140-lb. hammer, 30" drop)
3.25-inch OD Spilt Spoon
(300-lb hammer, 30" drop)
Non-standard penetration
test (see boring log for details)
Thin wall (Shelby) tube
Grab
Rock core
Vane Shear
Dusty, dry to the touch
Damp but no visible water
Visible free water
Terms and Symbols for
Boring and Test Pit Logs
Density
SILT / CLAY
GRAVEL (<5% fines)
GRAVEL (>12% fines)
SAND (<5% fines)
SAND (>12% fines)
Liquid Limit < 50
Liquid Limit > 50
Breaks along defined planes
Fracture planes that are polished or glossy
Angular soil lumps that resist breakdown
Soil that is broken and mixed
Less than one per foot
More than one per foot
Angle between bedding plane and a planenormaltocoreaxis
Very Loose
Loose
Med. Dense
Dense
Very Dense
SPT
N-values
Approx. Undrained Shear
Strength (psf)
<4
4 to 10
10 to 30
30 to 50
>50
<2
2 to 4
4 to 8
8 to 15
15 to 30
>30
SPT
N-values
Units of material distinguished by color and/orcomposition frommaterial unitsabove andbelow
Layers of soil typically 0.05 to 1mm thick, max. 1 cm
Layer of soil that pinches out laterally
Alternating layers of differing soil material
Erratic, discontinuous deposit of limited extent
Soil with uniform color and composition throughout
Approx. Relative
Density (%)
Gravel
Layered:
Laminated:
Lens:
Interlayered:
Pocket:
Homogeneous:
Highly Organic Soils
#4 to #10 sieve (4.5 to 2.0 mm)
#10 to #40 sieve (2.0 to 0.42 mm)
#40 to #200 sieve (0.42 to 0.074 mm)
0.074 to 0.002 mm
<0.002 mm
UNIFIED SOIL CLASSIFICATION SYSTEM
MAJOR DIVISIONS GROUP DESCRIPTIONS
Notes:
MONITORING WELL
<15
15 - 35
35 - 65
65 - 85
85 - 100
GW
GP
GM
GC
SW
SP
SM
SC
ML
CL
OL
MH
CH
OH
PT
TEST SYMBOLS
50%or more passing #200 sieve
Groundwater Level at time of drilling (ATD)Static Groundwater Level
Cement / Concrete Seal
Bentonite grout / seal
Silica sand backfill
Slotted tip
Slough
<250
250 - 500
500 - 1000
1000 - 2000
2000 - 4000
>4000
RELATIVE DENSITY / CONSISTENCY
Fissured:
Slickensided:
Blocky:
Disrupted:
Scattered:
Numerous:
BCN:
COMPONENT DEFINITIONS
Dry
Moist
Wet
1. Soil exploration logs contain material descriptions based on visual observation and field tests using a systemmodified from the Uniform Soil Classification System (USCS). Where necessary laboratory tests have beenconducted (as noted in the "Other Tests" column), unit descriptions may include a classification. Please refer to thediscussions in the report text for a more complete description of the subsurface conditions.
2. The graphic symbols given above are not inclusive of all symbols that may appear on the borehole logs.Other symbols may be used where field observations indicated mixed soil constituents or dual constituent materials.
COMPONENT SIZE / SIEVE RANGE COMPONENT SIZE / SIEVE RANGE
SYMBOLS
Sample/In Situ test types and intervals
Silt and Clay
Consistency
SAND / GRAVEL
Very Soft
Soft
Med. Stiff
Stiff
Very Stiff
Hard
Phone: 206.262.0370
Bottom of BoringBoulder:
Cobbles:
Gravel
Coarse Gravel:
Fine Gravel:
Sand
Coarse Sand:
Medium Sand:
Fine Sand:
Silt
Clay
> 12 inches
3 to 12 inches
3 to 3/4 inches
3/4 inches to #4 sieve
Atterberg Limit Test
Compaction Tests
Consolidation
Dry Density
Direct Shear
Fines Content
Grain Size
Permeability
Pocket Penetrometer
R-value
Specific Gravity
Torvane
Triaxial Compression
Unconfined Compression
Sand
50% or more of the coarse
fraction passing the #4 sieve.
Use dual symbols (eg. SP-SM)
for 5% to 12% fines.
for In Situ and Laboratory Testslisted in "Other Tests" column.
50% or more of the coarse
fraction retained on the #4
sieve. Use dual symbols (eg.
GP-GM) for 5% to 12% fines.
DESCRIPTIONS OF SOIL STRUCTURES
Well-graded GRAVEL
Poorly-graded GRAVEL
Silty GRAVEL
Clayey GRAVEL
Well-graded SAND
Poorly-graded SAND
Silty SAND
Clayey SAND
SILT
Lean CLAY
Organic SILT or CLAY
Elastic SILT
Fat CLAY
Organic SILT or CLAY
PEAT
ATT
Comp
Con
DD
DS
%F
GS
Perm
PP
R
SG
TV
TXC
UCC
LOG KEY 09-118 LOG.GPJ PANGEO.GDT 11/12/13Figure A-1
DocuSign Envelope ID: AA4FA6BA-AA72-4A92-A78C-D1916105F712
Terms and Symbols for
Boring and Test Pit Logs
Phone: 206.262.0370LOG KEY 09-118 LOG.GPJ PANGEO.GDT 11/12/13Figure A-1a
DocuSign Envelope ID: AA4FA6BA-AA72-4A92-A78C-D1916105F712
- Approximately 4 inches of asphalt over gravel.
Medium dense, moist, brown, silty SAND; trace gravel and cobbles.
[FILL].
- Inflated blows due to cobble at approximately 2.5 feet.
Medium dense to dense, wet to very moist, grey brown to light brown,
silty fine SAND; trace gravel, trace iron-oxide staining.
- Groundwater at approximately 5 feet during drilling.
[WEATHERED VASHON TILL - Qgt].
Hard, very moist to moist, grey-brown to blue-grey, sandy SILT; trace
gravel, trace iron oxide staining in fragments.
- Relative Weathering: Residual Soil RVI.
[RESIDUAL SOIL/RENTON FORMATION - Ec2pg].
- Gravel-sized coal fragments.
- Relative Weathering: Slightly Weathered RII.
Boring terminated at about 13.5 feet below grade. Groundwater
observed at about 5 feet at time of drilling.
S-1
S-2
S-3
S-4
S-5
31
22
24
8
9
9
19
32
50/6
19
41
50/2
45
50/6
Remarks: Borings drilled using an EC 95 track mounted drill rig. Standard penetration test
(SPT) sampler driven with a 140 lb safety hammer. Hammer operated with a rope and
cathead mechanism. Surface elevations (NAVD88) estimated from ALTA/NSPS Land
Title Survey by Terrane dated January 11, 2019.
0
2
4
6
8
10
12
14
16
18
20
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-2Other TestsSample No.Completion Depth:
Date Borehole Started:
Date Borehole Completed:
Logged By:
Drilling Company:Depth, (ft)Proposed Retail Development
19-122
Benson Drive South and Southeast Petrovitsky, Renton, WA
Northing: , Easting:
13.5ft
4/23/19
4/23/19
S. Scott
Boretec 1
Sheet 1 of 1
Project:
Job Number:
Location:
Coordinates:SymbolSample TypeBlows / 6 in.~ 404 ft
N/A
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING PG-1
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
>>
>>
>>
DocuSign Envelope ID: AA4FA6BA-AA72-4A92-A78C-D1916105F712
- Approximately 5 inches of asphalt over gravel.
Medium dense, moist, brown, silty SAND; trace gravel.
[WEATHERED VASHON TILL - Qgt].
- Perched groundwater at approximately 4 feet.
Medium dense, wet to very moist, blue-grey, silty fine SAND; trace
gravel.
- Hydrocarbon odor in Sample S-2.
Very dense, moist, light brown, silty fine SAND; trace gravel, trace
iron-oxide staining in gravel.
- Perched groundwater at approximately 11 feet.
Hard, moist, light grey, sandy SILT; trace gravel, laminated, trace
iron-oxide staining.
[RESIDUAL SOIL/RENTON FORMATION - Ec2pg].
- Gravel-sized coal fragments.
- Relative Weathering: Residual Soil RVI.
- Coarse sand pocket at approximately 13 feet.
Boring terminated at about 13.3 feet below grade. Perched
groundwater observed at about 4 feet and 11 feet at time of drilling.
S-1
S-2
S-3
S-4
S-5
8
8
7
4
4
7
18
23
34
24
25
50/5
37
50/4
Remarks: Borings drilled using an EC 95 track mounted drill rig. Standard penetration test
(SPT) sampler driven with a 140 lb safety hammer. Hammer operated with a rope and
cathead mechanism. Surface elevations (NAVD88) estimated from ALTA/NSPS Land
Title Survey by Terrane dated January 11, 2019.
0
2
4
6
8
10
12
14
16
18
20
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-3Other TestsSample No.Completion Depth:
Date Borehole Started:
Date Borehole Completed:
Logged By:
Drilling Company:Depth, (ft)Proposed Retail Development
19-122
Benson Drive South and Southeast Petrovitsky, Renton, WA
Northing: , Easting:
13.3ft
4/23/19
4/23/19
S. Scott
Boretec 1
Sheet 1 of 1
Project:
Job Number:
Location:
Coordinates:SymbolSample TypeBlows / 6 in.~ 402 ft
N/A
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING PG-2
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
>>
>>
DocuSign Envelope ID: AA4FA6BA-AA72-4A92-A78C-D1916105F712
- Approximately 6 inches of topsoil, concrete rubble near surface.
Medium dense, very moist to wet, brown to grey-brown, silty fine to
medium SAND; trace gravel, iron-oxide staining.
[WEATHERED VASHON TILL - Qgt].
- Perched groundwater at approximately 6 feet.
Hard, moist, light grey, sandy SILT; trace gravel, laminated.
[RESIDUAL SOIL/RENTON FORMATION - Ec2pg].
- Sand-sized coal fragments.
- Relative Weathering: Residual Soil RVI.
Boring terminated at about 15.9 feet below grade. Perched
groundwater observed at about 6 feet at time of drilling.
S-1
S-2
S-3
S-4
S-5
2
6
11
5
7
10
7
12
13
4
6
10
31
50/3
Remarks: Borings drilled using an EC 95 track mounted drill rig. Standard penetration test
(SPT) sampler driven with a 140 lb safety hammer. Hammer operated with a rope and
cathead mechanism. Surface elevations (NAVD88) estimated from ALTA/NSPS Land
Title Survey by Terrane dated January 11, 2019.
0
2
4
6
8
10
12
14
16
18
20
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-4Other TestsSample No.Completion Depth:
Date Borehole Started:
Date Borehole Completed:
Logged By:
Drilling Company:Depth, (ft)Proposed Retail Development
19-122
Benson Drive South and Southeast Petrovitsky, Renton, WA
Northing: , Easting:
15.9ft
4/23/19
4/23/19
S. Scott
Boretec 1
Sheet 1 of 1
Project:
Job Number:
Location:
Coordinates:SymbolSample TypeBlows / 6 in.~ 408 ft
N/A
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING PG-3
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
>>
DocuSign Envelope ID: AA4FA6BA-AA72-4A92-A78C-D1916105F712
- Approximately 6 inches of topsoil, concrete rubble near surface.
Medium dense, very moist, grey to light brown, silty fine to medium
SAND; trace gravel.
[WEATHERED VASHON TILL - Qgt].
Medium dense to dense, very moist to wet, brown to grey-brown, silty
fine SAND with gravel; trace coarse sand pockets, laminated,
iron-oxide staining in gravels.
- Perched groundwater at approximately 9 feet.
Boring terminated at about 11.5 feet below grade. Perched
groundwater observed at about 9 feet at time of drilling.
S-1
S-2
S-3
S-4
2
9
12
8
7
7
8
6
6
9
15
32
Remarks: Borings drilled using an EC 95 track mounted drill rig. Standard penetration test
(SPT) sampler driven with a 140 lb safety hammer. Hammer operated with a rope and
cathead mechanism. Surface elevations (NAVD88) estimated from ALTA/NSPS Land
Title Survey by Terrane dated January 11, 2019.
0
2
4
6
8
10
12
14
16
18
20
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-5Other TestsSample No.Completion Depth:
Date Borehole Started:
Date Borehole Completed:
Logged By:
Drilling Company:Depth, (ft)Proposed Retail Development
19-122
Benson Drive South and Southeast Petrovitsky, Renton, WA
Northing: , Easting:
11.5ft
4/23/19
4/23/19
S. Scott
Boretec 1
Sheet 1 of 1
Project:
Job Number:
Location:
Coordinates:SymbolSample TypeBlows / 6 in.~ 408 ft
N/A
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING PG-4
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
DocuSign Envelope ID: AA4FA6BA-AA72-4A92-A78C-D1916105F712
- Approximately 5 inches of asphalt over gravel.
Very loose, moist, grey to orange-brown, GRAVEL with silt; trace
iron-oxide staining.
[FILL].
Medium dense, very moist to wet, light brown to light-grey, silty fine
SAND; trace gravel, coarse sand pockets.
- Perched groundwater at approximately 5 feet.
[WEATHERED VASHON TILL - Qgt].
Hard, moist, grey-brown, sandy SILT; trace gravel, iron-oxide staining
in gravel.
[RESIDUAL SOIL/RENTON FORMATION - Ec2pg].
- Sand-sized coal fragments.
- Relative Weathering: Residual Soil RVI.
Boring terminated at about 11.5 feet below grade. Perched
groundwater observed at about 5 feet at time of drilling.
S-1
S-2
S-3
S-4
3
1
3
6
6
7
5
6
8
17
20
22
Remarks: Borings drilled using an EC 95 track mounted drill rig. Standard penetration test
(SPT) sampler driven with a 140 lb safety hammer. Hammer operated with a rope and
cathead mechanism. Surface elevations (NAVD88) estimated from ALTA/NSPS Land
Title Survey by Terrane dated January 11, 2019.
0
2
4
6
8
10
12
14
16
18
20
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-6Other TestsSample No.Completion Depth:
Date Borehole Started:
Date Borehole Completed:
Logged By:
Drilling Company:Depth, (ft)Proposed Retail Development
19-122
Benson Drive South and Southeast Petrovitsky, Renton, WA
Northing: , Easting:
11.5ft
4/23/19
4/23/19
S. Scott
Boretec 1
Sheet 1 of 1
Project:
Job Number:
Location:
Coordinates:SymbolSample TypeBlows / 6 in.~ 407 ft
N/A
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING PG-5
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
DocuSign Envelope ID: AA4FA6BA-AA72-4A92-A78C-D1916105F712
- Approximately 2 inches of asphalt over gravel.
Very loose, moist, grey to grey-brown, silty SAND; trace gravel, trace
iron-oxide staining.
[WEATHERED VASHON TILL - Qgt].
- Manganese staining.
Medium dense, very moist to wet, grey-brown, silty SAND; trace
gravel, trace iron-oxide staining, slightly laminated.
- Perched groundwater at approximately 6 feet.
Very dense, moist, grey-brown, silty SAND; trace gravel, trace
iron-oxide staining in gravel.
- Large gravel crushed in tip of splitspoon at approximately 10 feet.
Boring terminated at about 11.5 feet below grade. Perched
groundwater observed at about 6 feet at time of drilling.
S-1
S-2
S-3
S-4
4
1
3
6
11
16
31
28
50/5
23
36
36
Remarks: Borings drilled using an EC 95 track mounted drill rig. Standard penetration test
(SPT) sampler driven with a 140 lb safety hammer. Hammer operated with a rope and
cathead mechanism. Surface elevations (NAVD88) estimated from ALTA/NSPS Land
Title Survey by Terrane dated January 11, 2019.
0
2
4
6
8
10
12
14
16
18
20
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-7Other TestsSample No.Completion Depth:
Date Borehole Started:
Date Borehole Completed:
Logged By:
Drilling Company:Depth, (ft)Proposed Retail Development
19-122
Benson Drive South and Southeast Petrovitsky, Renton, WA
Northing: , Easting:
11.5ft
4/23/19
4/23/19
S. Scott
Boretec 1
Sheet 1 of 1
Project:
Job Number:
Location:
Coordinates:SymbolSample TypeBlows / 6 in.~ 410 ft
N/A
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING PG-6
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
>>
DocuSign Envelope ID: AA4FA6BA-AA72-4A92-A78C-D1916105F712
- Approximately 4 inches of asphalt over gravel.
Medium dense, moist, dark grey to brown, silty SAND; trace gravel.
[FILL].
Medium dense, very moist to wet , grey-brown, silty fine to medium
SAND; trace gravel, coarse sand pockets, trace iron-oxide staining,
slightly laminated.
- Perched groundwater at approximately 5 feet.
[WEATHERED VASHON TILL - Qgt].
Hard, very moist to moist, grey-brown to grey, sandy SILT with gravel;
iron-oxide staining in gravel, slightly laminated.
- Relative Weathering: Residual Soil RVI.
[RESIDUAL SOIL/RENTON FORMATION - Ec2pg].
- Gravel-sized coal fragments.
- Relative Weathering: Highly Weathered RIV.
Boring terminated at about 15.8 feet below grade. Perched
groundwater observed at about 5 feet at time of drilling.
S-1
S-2
S-3
S-4
S-5
8
9
8
5
10
9
5
12
10
14
19
27
29
50/4
Remarks: Borings drilled using an EC 95 track mounted drill rig. Standard penetration test
(SPT) sampler driven with a 140 lb safety hammer. Hammer operated with a rope and
cathead mechanism. Surface elevations (NAVD88) estimated from ALTA/NSPS Land
Title Survey by Terrane dated January 11, 2019.
0
2
4
6
8
10
12
14
16
18
20
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-8Other TestsSample No.Completion Depth:
Date Borehole Started:
Date Borehole Completed:
Logged By:
Drilling Company:Depth, (ft)Proposed Retail Development
19-122
Benson Drive South and Southeast Petrovitsky, Renton, WA
Northing: , Easting:
15.8ft
4/23/19
4/23/19
S. Scott
Boretec 1
Sheet 1 of 1
Project:
Job Number:
Location:
Coordinates:SymbolSample TypeBlows / 6 in.~ 409 ft
N/A
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING PG-7
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
>>
DocuSign Envelope ID: AA4FA6BA-AA72-4A92-A78C-D1916105F712
- Approximately 5 inches of asphalt over gravel.
Medium dense, moist, grey to grey-brown, silty fine to medium SAND;
trace gravel, iron-oxide staining, appears reworked.
[FILL].
Medium dense, very moist to wet, grey-brown, silty fine to medium
SAND; trace gravel, trace coarse sand pockets, trace iron-oxide
staining, slightly laminated.
[WEATHERED VASHON TILL - Qgt].
- Perched groundwater at approximately 6 feet.
- Perched groundwater at approximately 10 feet.
Hard, very moist, grey-brown to grey, sandy SILT with gravel; trace
coarse sand pockets.
[RESIDUAL SOIL/RENTON FORMATION - Ec2pg].
- Gravel-sized coal fragments.
- Relative Weathering: Residual Soil RVI.
Boring terminated at about 15.8 feet below grade. Perched
groundwater observed at about 6 feet and 10 feet at time of drilling.
S-1
S-2
S-3
S-4
S-5
7
11
14
8
6
6
10
10
10
5
6
6
30
50/4
Remarks: Borings drilled using an EC 95 track mounted drill rig. Standard penetration test
(SPT) sampler driven with a 140 lb safety hammer. Hammer operated with a rope and
cathead mechanism. Surface elevations (NAVD88) estimated from ALTA/NSPS Land
Title Survey by Terrane dated January 11, 2019.
0
2
4
6
8
10
12
14
16
18
20
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-9Other TestsSample No.Completion Depth:
Date Borehole Started:
Date Borehole Completed:
Logged By:
Drilling Company:Depth, (ft)Proposed Retail Development
19-122
Benson Drive South and Southeast Petrovitsky, Renton, WA
Northing: , Easting:
15.8ft
4/23/19
4/23/19
S. Scott
Boretec 1
Sheet 1 of 1
Project:
Job Number:
Location:
Coordinates:SymbolSample TypeBlows / 6 in.~ 411 ft
N/A
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING PG-8
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
>>
DocuSign Envelope ID: AA4FA6BA-AA72-4A92-A78C-D1916105F712