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

Boring MW-2 and test pit PIT-2 were completed in a grassy median between the road and sidewalk on the south side of 128th Street SW about 120 to 200 feet east of 4th Avenue West. Boring MW-2 was completed to a depth of 211/2 feet bgs,and test pit PIT-2 was completed to a depth of about 8 feet bgs(after completion of the infiltration test). Fill consisting of loose to medium dense sand with varying amounts of silt was encountered to depths of 6 to 10 feet in these explorations. The fill is underlain by dense to very dense glacial till. Groundwater was not encountered during drilling boring GEI-14. Groundwater was measured in MW-2 at a depth of 10.7 feet on March 10, 2017. Airport Road/128th Street SW at East Gibson Road Boring GEI-15 was drilled in the eastbound existing bus stop lane on 128th Street SW and hand auger HA-6 was conducted in the grass south of GEI-15 as shown on site plan Figure 2N. GEI-15 and HA-6 were completed at depths of 61/2 and 21/2 feet bgs, respectively. Fill was encountered in both borings. The fill consisted of medium dense silty sand with gravel and sandy gravel with silt.The fill extended to the depth explored.A woven geotextile was encountered at a depth of about 6 feet in GEI-15.The drilling was stopped due to practical refusal at a depth of 61/2 feet because of large cobbles kicking the auger off-vertical. The hand auger encountered moderate groundwater seepage at a depth of 1 foot and groundwater was not observed during drilling of GEI-15. Airport Road at SR 99 Boring GEI-16 was drilled in the grass near the existing southbound bus stop on Airport road south of the intersection with SR 99, as shown on site plan Figure 20.We encountered medium dense silty sand fill to a depth of about 71 feet bgs overlying very loose to loose silty sand with occasional gravel.An approximate 3-foot thickness of medium dense sand with silt was encountered below the loose silty sand to a depth of about 15 feet. The boring was terminated in dense silty sand with occasional gravel interpreted to be weathered glacial till. Groundwater was encountered at approximately 12 feet bgs at the time of drilling. Airport Road at 112th Street SW and Airport Road at 100th Street SW Boring GEI-17 was drilled in the existing northbound bus stop lane on Airport Road north of the intersection with 112th Street SW as shown on site plan Figure 2P. Boring GEI-18 was drilled on the grass slope in the northeast corner of the intersection of Airport Road and 100th Street SW as shown on site plan Figure 2Q. GEI-17 and GEI-18 were each completed at depths of 111/2 feet. Fill was encountered in both borings to the depths explored.The fill consists primarily of loose to medium dense silty sand with variable gravel content. We did not encounter groundwater at either location during drilling. Airport Road at Kasch Park Road Boring GEI-19 was drilled in the southbound bike lane on Airport road south of the intersection with Kasch Park Road as shown on site plan Figure 2R. Fill was encountered to a depth of approximately 10 feet bgs. The fill consisted of loose to medium dense silty sand with occasional gravel and cobbles. An approximate 5-foot layer of loose to medium dense silty sand was encountered below the fill, and the boring was terminated in very dense glacial till at a depth of 161/2 feet bgs. Groundwater was not observed during drilling. GEOENGINEERS April 14,2017 Page 9 File No.2095-032-00