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Harding Lawson Associates December 20, 1994 256661 ' San Joaquin County Mr Harlin Knoll Page 5 ' locations After removing the concrete core, a slide hammer was used to drive a sample tube into the sail below the bunker The sample tube was than removed, sealed, and labeled and placed in an cooler containing ice for delivery to the analytical laboratory The two soil samples were submitted ' for analyses by EPA Method 8015, 8020, and 418 1 for Total petroleum hydrocarbons as diesel (TPHd), BTEX, and total recoverable petroleum hydrocarbons (TRPH) ' SITE CONDITIONS Soils encountered during the drilling and installation of monitoring well MW-A1 consisted of brown to dark grey sandy clay to a depth of approximately 12 feet bgs From 12 to 17 feet bgs, an olive brown ' sand was observed Groundwater was first encountered during drilling at a depth of 9 feet bgs PID readings above background levels were recorded for only one sample from this borehole The sample collected at 10 feet bgs was reported at 10 parts per million (ppm) ' Soils encountered during the drilling of MW-Bl consisted gravelly sand fill material to a depth of 3 feet bgs and dark olive grey clay to 14 feet bgs Brown sandy clay was observed from 14 feet bgs to the bottom of the borehole at 20 feet bgs Groundwater was first encountered during the drilling of MW-B1 at approximately 15 feet bgs PID readings were measured in the 5-foot sample (100 ppm) and 10 foot samples (150 ppm) Static water level data are presented below The overall direction of groundwater flow based on this data at the HSC facility is presented on Plate 1 Well No Top of Casing Elevation Depth to Water Groundwater Elevation ' (feet Mean Sea Level) (feet) (feet Mean Sea Level) MW-A1 274 963 -689 MW-B1 406 1214 -808 WP-1 5 19 1213 -694 WP-2 627 1531 -904 Two groundwater flow directions were calculated, using either MW-A1 or WP-1 and the two ' remaining wells (Plate 1) Groundwater flow was calculated to be toward the northeast using both sets of data Gradients for the two solutions vary from 0 003 using MW-A1 to 0 001 using WP-1 The local groundwater flow in the vicinity of each site may vary from this data At Site A, the ' elevation of the water table was higher in monitoring well MW-A1 than that in the assumed upgradnent well WP-1 This data may indicate an anomalous groundwater mound or flow conditions may occur in the vicinity of Site A ' RESULTS S><te A Analytical results of the groundwater/sod gas survey and groundwater samples collected from the ' monitoring wells are summarized in Tables 1 and 2, respectively Laboratory reports are attached At Site A only samples WS-1 and WS-3 contained detectable concentrations of TVHC and benzene The