11831 AIRPORT RD WHOLE SITE FILE Geotech Report 2022-10-25

SR 527 at 196th Street SE Boring GEI-5 was drilled in the southbound existing bus stop lane on SR 527; hand auger HA-2 was completed in the grass behind the fence west of GEI-5 as shown on site plan Figure 2E. GEI-5 and HA-2 were completed to depths of 2% feet bgs. At GEI-5, a thin layer of fill was encountered underlying the asphalt. The fill consisted of silty sand with gravel. Underlying the fill was a thin concrete slab and a 4 inch PVC pipe. We stopped GEI-5 because of the PVC pipe encountered. We understand WSDOT has no records of this PVC pipe. Surficial soils encountered in HA-2 consisted of medium dense silty sand with gravel,which became dense to very dense at the bottom of the boring.The hand auger met practical refusal at 21/2 feet. We did not encounter groundwater at this location during drilling. SR 527 at 180th Street SE Boring GEI-6 was drilled in the parking lot in the southwest corner of the intersection of SR 527 and 180th Street SE,as shown on site plan Figure 2F. Boring GEI-6 was completed at a depth of 101/2 feet bgs. Glacial till was encountered directly beneath the thin asphalt section to the depth explored. The glacial till varied in composition, but was generally very dense silty sand with gravel and sandy silt with gravel. We did not encounter groundwater at this location during drilling. SR 527 at 164th Street SE Explorations completed in the vicinity of SR 527 and 164th Street SE include boring GEI-24 located in the right lane of northbound SR 527 south of the intersection; hand auger HA-3 located on the grass slope south of the southwest corner of the intersection; boring GEI-8 in the right turn lane from eastbound Mill Creek Road onto northbound SR 527; and boring MW-3 about 200 feet south of GEI-24.The locations of the explorations are shown on site plan Figure 2G. Boring MW-3, GEI-24, hand auger HA-3 and boring GEI-8 were completed at depths of 21%, 16/, 4, and 161/2 feet bgs, respectively. In general, medium dense gravel and sand with variable silt content was encountered below the pavement surfacing in the borings. Medium dense to dense silty sand was encountered in both borings at a depth of about 10 feet to the bottom of the borings. Hand auger HA-3 also encountered medium dense silty sand below the topsoil, which became dense at a depth of about 3 feet. Boring MW-3 encountered very stiff silt below the surficial fill at a depth of approximately 10 feet,and very dense silty sand (glacial till)at a depth of about 13 feet. Groundwater was observed at approximately 4 to 5 feet bgs in GEI-8 and HA-3 at the time of drilling. Groundwater was not observed in GEI-24, but a wet soil sample was encountered at the bottom of the boring.Groundwater was measured in MW-3 at a depth of 4 feet on March 10, 2017. GEOENGINEERS_g April 14,2017 Page 6 File No.2095-032-00