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Home My WebLink AboutRS_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. 1 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) 2 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. 3 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. 4 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. 5 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. 6 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. 7 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. 8 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. 9 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. APPENDIX A General Exhibits 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. 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 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 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 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 APPENDIX B Downstream Analysis 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 APPENDIX C Flow Control and Water Quality Calculations WWHM2012 PROJECT REPORT 19-045-Detention 8/4/2022 4:30:41 PM Page 2 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 19-045-Detention 8/4/2022 4:30:41 PM Page 3 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 19-045-Detention 8/4/2022 4:30:41 PM Page 4 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 19-045-Detention 8/4/2022 4:30:41 PM Page 5 Routing Elements Predeveloped Routing 19-045-Detention 8/4/2022 4:30:41 PM Page 6 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 19-045-Detention 8/4/2022 4:30:41 PM Page 7 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 19-045-Detention 8/4/2022 4:30:41 PM Page 8 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 19-045-Detention 8/4/2022 4:31:29 PM Page 9 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 19-045-Detention 8/4/2022 4:31:29 PM Page 10 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 19-045-Detention 8/4/2022 4:31:29 PM Page 12 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 19-045-Detention 8/4/2022 4:31:29 PM Page 13 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 APPENDIX D Geotechnical Report (By PanGEO, Dated May 2019) 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 ________________________________________________ 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 19-122 Benson Drive and Petrovitsky Road Page 1 PanGEO, Inc. 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 19-122 Benson Drive and Petrovitsky Road Page 1 PanGEO, Inc. 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. 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 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 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 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 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 6 PanGEO, Inc. 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. 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 7 PanGEO, Inc. 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 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 8 PanGEO, Inc. 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. 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 9 PanGEO, Inc. 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 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 10 PanGEO, Inc. 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 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 11 PanGEO, Inc. 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). 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 12 PanGEO, Inc. 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 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 13 PanGEO, Inc. 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 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 14 PanGEO, Inc. 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. 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 15 PanGEO, Inc. • 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. 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 16 PanGEO, Inc. 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 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 17 PanGEO, Inc. 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 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 18 PanGEO, Inc. 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. 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) SPS 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 ProposedDevelopments APPENDIX A BORING LOGS 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 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 - 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 >> >> >> - 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 >> >> - 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 >> - 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 - 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 - 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 >> - 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 >> - 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 >>