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3.0 SITE INVESTIGATION RESULTS 3.1 Geology and Hydrogeology In general, the soils beneath the site on fining-upward sequence f fine-grained 9 consist of a fining upwa d seq e o g siliciclastic sediments The uppermost sal is a light brown silty clay that grades into a light brown clayey silt, between 5 and 10 feet bgs Between 10 and 15 feet bgs, the clayey silt grades into a light brown silty fine sand In MW-2, silty clay was observed underlying the sility fine sand at the total depth of 20 feet bgs In MW-1 and MW-3, this silty clay sod was not present On October 29, 1998, saturated sod was encountered during drilling between 10 and 11 feet bgs Approximately 15 minutes after encountering saturated soil in each of the soil borings, groundwater was observed between 7 85 and 8 7 feet bgs On November 5, 1998, the static depth-to-groundwater ranged from 7 74 feet bgs in MW-3 to 8 16 feet bgs in MW-1 The corresponding groundwater surface elevation ranged from a high of 41 22 feet mean sea level (msl) at MW-1 to a low of 41 03 feet msl at MW-2 and MW-3 The resulting groundwater surface appears as a plane dipping to the north at a gradient of approximately 0 004 foot/foot A groundwater surface contour map is included as Figure 3 The well construction details, wellhead elevations and groundwater monitoring data are summanzed in Table 3 32 Analytical Results Only the groundwater sample collected from MW-2 contained detectable concentrations of petroleum hydrocarbons The only petroleum hydrocarbon compound detected in the MW-2 sample was TPH-as-diesel at a concentration of 140 micrograms per liter (µg11) TPH-as- ' gasoline, BTFX and the oxygenate compounds were not detected in MW-2 None of the analyzed compounds (TPH-as-diesel, TPH-as-gasoline, BTFX and oxygenates) were detected in the groundwater samples collected from MW-1 and MW-3 The results of the groundwater monitoring well samples are summarized in Table 4 The laboratory reports are included in Appendix F The physiochemical data indicate that nitrate concentrations beneath the site range from 4 84 to 21 2 ppm This was the only physiochemical parameter below normal concentration Both general and selective (contaminant-specific) microbial populations were low, however, the relative ' percentage of selective microorganisms to the total number of heterotrophs ranged from 21 05% in MW-2 to 41 18% in MW-3 The BioLogic laboratory report and written summary of analyses are also included in Appendix F �• 10