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u.— <br /> Subsurface soils consist primarily of massive sand-based units with varying percentages of fine <br /> gravel, silt and clay. Soil impacted by greater than 100 mg/kg of TPH-as-diesel extends up to <br /> approximately 40 feet away from the former UST excavation. The lateral extent of impacted soil <br /> was not defined to the north of the site, under Highway 99. The vertical extent of impacted soil is <br /> undefined in the vicinity of the former UST. Vertically, petroleum hydrocarbons are concentrated <br /> in soil within the zone of groundwater fluctuation (i.e., capillary fringe). The greatest concentration <br /> of TPH-as-diesel (8,800 mg/kg) was detected in close proximity to the former UST excavation <br /> (SB-7) at a depth of 15 feet bgs. The soil sample collected at the total depth of SB-7 (20 feet) <br /> contained 460 mg/kg of TPH-as-diesel. The soil sample analytical results are summarized in <br /> Table 1 and the results of the physical soils testing are included in Table 5. <br /> 4 <br />