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The remaining quality control samples (trip blanks, matrix spikes, and matrix <br /> spike duplicates) did not reveal any problems with the shipping or analytical <br /> procedures <br /> 3.2 Subsurface Conditions <br /> The drilling of the HydroPunch II0 and monitoring well borings indicated <br /> predominantly a sandy gravel from the surface to a depth of 1 to 15 feet The <br /> ' exception to this is the HP-6 boring which was drilled in an area surfaced with 6 <br /> inches of concrete which overlies a 6-inch layer of sand No petroleum odor or <br /> ' staining was observed in this material Field screening with an organic vapor analyzer <br /> did not indicate the presence of volatile organics <br /> Layers of silty clay, clay, clayey silt, and silt were observed beneath the gravel <br /> ' and sand to depths of 12 to 15 feet bgs in the HydroPunch He and monitoring well <br /> borings Silt, sandy silt, and silty sand were observed from 12 5 to 25 5 feet bgs, and <br /> clay was observed at 25 5 feet bgs in MW-8 Silt, sandy silt, and silty sand were <br /> observed from 8 5 to 26 5 feet bgs with a thin sandy clay lens at 25 feet bgs in MW-9 <br /> t These results are consistent with the findings of previous assessments <br /> Hydrocarbon odors and soil discoloration were observed while drilling the <br /> boring for HP-4 An odor was also observed while drilling HP-5 Low organic vapor <br /> analyzer readings were recorded from head space analysis of moist soil from 12 feet <br /> bgs in HP-1 <br /> ' Water level measurements taken in the seven existing groundwater monitoring <br /> wells and the two new groundwater monitoring wells indicate that groundwater is <br /> ' approximately 12 feet bgs The direction of the groundwater flow appears to be <br /> southwest with a gradient of 0 002 feet per foot (Figure 5) <br /> 1 <br /> 931122 East Bay Municipal Utility Distnct <br /> 40-329500 asa 9 Stockton Svc Ctr -Site Assessment/Remedial Options <br />