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Home My WebLink AboutRS_Geotech_181008.pdf Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone 425.415.0551 ♦ Fax 425.415.0311 www.riley-group.com July 3, 2018 Mark Woodbridge Builders Capital 5601 6th Avenue South #350 Seattle, Washington 98108 Subject: Stormwater Infiltration Feasibility Study 134 Elma Avenue Northeast Renton, Washington RGI Project No. 2018-139 Dear Mr. Woodbridge: As requested, The Riley Group, Inc. (RGI) is pleased to provide the results of our recent subsurface characterization services at 134 Elma Avenue Northeast in Renton, Washington (Figure 1). Subsurface Conditions RGI observed the completion of four test pits (TP-1, TP-2, TP-3, TP-4) to assess shallow subsurface soil and groundwater conditions for potential infiltration of stormwater at the Site. The test pits were completed using a subcontracted mini-excavator. The location of the four test pits are shown on Figure 2. Review of the Geologic map of the Renton quadrangle, King County, Washington, by Mullineaux, D.R. (1965) indicates that the soil in the project vicinity is mapped as Vashon-age lodgment till (Qvt), which is a nonsorted mixture of very dense silty sand with gravel and cobbles. Review of the Preliminary Geologic Map of Seattle and Vicinity, Washington, by Waldron, H.H, et al (1962) indicates that the soil in the project vicinity is mapped as Vashon-age lodgment till (Qvt), which is a nonsorted mixture of very dense silty sand with gravel and cobbles. In general the site soils encountered were comprised of a surface layer of sod and topsoil underlain by very dense, silty sand with gravel interpreted to be glacially consolidated lodgment till soils. No groundwater was encountered in any of the test probe borings. Infiltration Feasibility As described above glacially consolidated soils were encountered in all of the test probes completed at the site. In test pits TP-1, TP-2, and TP-3 the unweathered very dense lodgment till was encountered at a depth of six inches. In test pit TP-4 the unweathered very dense lodgment till was encountered at approximately 18 inches. Based on the presence of hydraulically restrictive soils comprised of glacially consolidated lodgment till at very shallow depths below the topsoil at the site and separation distances prescribed in City of Renton stormwater manual infiltration is considered infeasible at the Site. USGS, 2014, Renton, Washington 7.5-Minute Quadrangle Approximate Scale: 1"=1000' 0 500 1000 2000 N Site Vicinity Map Figure 1 07/2018 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Builders Capital Elma Avenue RGI Project Number 2018-139 Date Drawn: Address: 134 Elma Avenue Northeast, Renton, Washington 98059 SITE TP-1TP-2TP-3TP-407/2018Corporate Office17522 Bothell Way NortheastBothell, Washington 98011Phone: 425.415.0551Fax: 425.415.0311Builders Capital Elma AvenueRGI Project Number2018-139Date Drawn:Address: 134 Elma Avenue Northeast, Renton, Washington 98059Site Plan with Test Pit LocationsFigure 2Approximate Scale: 1"=40'0204080N= Test pit by RGI, 6/19/18= Site boundary Project Name:Builders Capital Elma AVE Project Number:2018-139 Client:Builders Capital Test Pit No.: TP-1 Date(s) Excavated:06/19/18 Excavation Method:Backhoe Excavator Type:Mini-excavator Groundwater Level:Not encountered Test Pit Backfill:Native Soil Logged By SL Bucket Size: Excavating Contractor:Kelly's Excavating Sampling Method(s)Continuous Location 134 Elma Avenue Northeast, Renton, WA 98059 Surface Conditions:Sod Total Depth of Excavation:5 feet bgs Approximate Surface Elevation n/a Compaction Method n/a USCS SymbolTop soil SM REMARKS AND OTHER TESTSGraphic LogMATERIAL DESCRIPTION Top soil Gray, silty SAND with gravel, very dense, moist (lodgment till) Test pit excavated to 5 feet bgs No groundwater encounteredDepth (feet)0 5 10 15 Sample NumberSample TypeElevation (feet)Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name:Builders Capital Elma AVE Project Number:2018-139 Client:Builders Capital Test Pit No.: TP-2 Date(s) Excavated:06/19/18 Excavation Method:Backhoe Excavator Type:Mini-excavator Groundwater Level:Not encountered Test Pit Backfill:Native Soil Logged By SL Bucket Size: Excavating Contractor:Kelly's Excavating Sampling Method(s)Continuous Location 134 Elma Avenue Northeast, Renton, WA 98059 Surface Conditions:Sod Total Depth of Excavation:5 feet bgs Approximate Surface Elevation n/a Compaction Method n/a USCS SymbolTop soil SM REMARKS AND OTHER TESTSGraphic LogMATERIAL DESCRIPTION Top soil Gray, silty SAND with gravel, very dense, moist (lodgment till) Test pit excavated to 5 feet bgs No groundwater encounteredDepth (feet)0 5 10 15 Sample NumberSample TypeElevation (feet)Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name:Builders Capital Elma AVE Project Number:2018-139 Client:Builders Capital Test Pit No.: TP-3 Date(s) Excavated:06/19/18 Excavation Method:Backhoe Excavator Type:Mini-excavator Groundwater Level:Not encountered Test Pit Backfill:Native Soil Logged By SL Bucket Size: Excavating Contractor:Kelly's Excavating Sampling Method(s)Continuous Location 134 Elma Avenue Northeast, Renton, WA 98059 Surface Conditions:Sod Total Depth of Excavation:5 feet bgs Approximate Surface Elevation n/a Compaction Method n/a USCS SymbolTop soil SM SM REMARKS AND OTHER TESTSGraphic LogMATERIAL DESCRIPTION Top soil Brown, silty SAND with gravel, dense, moist (weathered lodgment till) Gray, silty SAND with gravel, very dense, moist (lodgment till) Test pit excavated to 5 feet bgs No groundwater encounteredDepth (feet)0 5 10 15 Sample NumberSample TypeElevation (feet)Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name:Builders Capital Elma AVE Project Number:2018-139 Client:Builders Capital Test Pit No.: TP-4 Date(s) Excavated:06/19/18 Excavation Method:Backhoe Excavator Type:Mini-excavator Groundwater Level:Not encountered Test Pit Backfill:Native Soil Logged By SL Bucket Size: Excavating Contractor:Kelly's Excavating Sampling Method(s)Continuous Location 134 Elma Avenue Northeast, Renton, WA 98059 Surface Conditions:Sod Total Depth of Excavation:5 feet bgs Approximate Surface Elevation n/a Compaction Method n/a USCS SymbolTop soil SM SM REMARKS AND OTHER TESTSGraphic LogMATERIAL DESCRIPTION Top soil Brown/gray, silty SAND with gravel, dense, moist (weathered lodgment till) Gray, silty SAND with gravel, very dense, moist (lodgment till) Test pit excavated to 5 feet bgs No groundwater encounteredDepth (feet)0 5 10 15 Sample NumberSample TypeElevation (feet)Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name:Builders Capital Elma AVE Project Number:2018-139 Client:Builders Capital Key to Logs USCS SymbolREMARKS AND OTHER TESTSGraphic LogMATERIAL DESCRIPTIONDepth (feet)Sample NumberSample TypeElevation (feet)1 2 3 4 5 6 7 8 COLUMN DESCRIPTIONS 1 Elevation (feet): Elevation (MSL, feet). 2 Depth (feet): Depth in feet below the ground surface. 3 Sample Type: Type of soil sample collected at the depth interval shown. 4 Sample Number: Sample identification number. 5 USCS Symbol: USCS symbol of the subsurface material. 6 Graphic Log: Graphic depiction of the subsurface material encountered. 7 MATERIAL DESCRIPTION: Description of material encountered. May include consistency, moisture, color, and other descriptive text. 8 REMARKS AND OTHER TESTS: Comments and observations regarding drilling or sampling made by driller or field personnel. FIELD AND LABORATORY TEST ABBREVIATIONS CHEM: Chemical tests to assess corrosivity COMP: Compaction test CONS: One-dimensional consolidation test LL: Liquid Limit, percent PI: Plasticity Index, percent SA: Sieve analysis (percent passing No. 200 Sieve) UC: Unconfined compressive strength test, Qu, in ksf WA: Wash sieve (percent passing No. 200 Sieve) MATERIAL GRAPHIC SYMBOLS Silty SAND (SM) TYPICAL SAMPLER GRAPHIC SYMBOLS Auger sampler Bulk Sample 3-inch-OD California w/ brass rings CME Sampler Grab Sample 2.5-inch-OD Modified California w/ brass liners Pitcher Sample 2-inch-OD unlined split spoon (SPT) Shelby Tube (Thin-walled, fixed head) OTHER GRAPHIC SYMBOLS Water level (at time of drilling, ATD) Water level (after waiting) Minor change in material properties within a stratum Inferred/gradational contact between strata ?Queried contact between strata GENERAL NOTES 1: Soil classifications are based on the Unified Soil Classification System. Descriptions and stratum lines are interpretive, and actual lithologic changes may be gradual. Field descriptions may have been modified to reflect results of lab tests. 2: Descriptions on these logs apply only at the specific boring locations and at the time the borings were advanced. They are not warranted to be representative of subsurface conditions at other locations or times. Sheet 1 of 1 The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011