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Depths to groundwater were measured in each well prior to purging a n d sampling on October 12, 2000 with an electric water level sounder Depth to groundwater measurements are presented in Table Three On October 12, 2000, the groundwater flow direction based on potentiometric surface contours appeared to flow to the northwest at a gradient of approximately 0 0039-feet/foot A groundwater potentiometric surface map is presented as Figure 10 12 . 0 CONCLUSIONS The benzene and total xylenes concentrations detected in soil samples collected from 7-feet bgs in boring CPT-2 and 5 5-feet bgs in boring MW-2 were the only compounds that exceeded the US EPA PRGs for residential soil The benzene concentration in the soil samples collected at 5 5-feet bgs in boring MW-4 also exceeded the PRG for residential soil The benzene concentrations in groundwater samples collected from monitoring wells MW-2 and MW-4, and also the toluene concentration in groundwater samples collected from monitoring well MW-2, exceeded the DHS MCL for drinking water The MTBE concentrations in monitoring wells MW-1, MW-2, MW-4, and MW-5 exceeded the DHS MCL for drinking water The benzene concentration in groundwater samples collected from boring CPT-2 at 37-feet bgs was the only compound from the deeper borings that exceeded the DHS MCL for drinking water Based on the permeability of the lithology beneath the site there seems to be a hydrogeologic barrier to the northwest (downgradient) of the site (Figures 4 and 5) This hydrogeologic barrier may be directing groundwater to the west and northeast Soil beneath the first water bearing zone, the bottom of which is no deeper than 16-feet bgs, generally consists of low to very low permeability sediments to a total depth of at least 70-feet bgs Only a couple of very thin sand or sandy silt lenses, no thicker than 1-foot in thickness, were located in this very low permeability unit The soil samples collected from this low permeability unit, from depths ranging from 15 5 to 19-feet bgs, contained either low or non-detectable hydrocarbon concentrations Groundwater samples collected from a sandy silt lens in CPT-1 at 41-feet bgs contained only 056 ppb total xylenes with no detectable TPH-G, benzene, toluene, ethyl benzene, or oxygenate concentrations No groundwater samples could be recovered during a sampling attempt from the sandy silt lens at 57-feet bgs A groundwater sample collected from a 0 5-foot thick sand layer at 37-feet bgs contained 74 ppb TPH-G, 3 0 p p b 574 West Grant Line Road Report — October 2000 -]0-