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2.6 Site HydroaeQlQay Groundwater was encountered during monitor well drilling at five to six feet below ground surface (BGS). This is believed to be an unconfined aquifer since no confining layer or aquitard was found during drilling. The thickness of this aquifer is not known. The depth to water was recorded in each of the monitoring wells prior to each groundwater sampling event. This depth, together with the relative elevations of the well E head measuring points, yields the groundwater elevations in each well. As mentioned previously, the elevations of the well heads were surveyed with respect to an arbitrary datum elevation of 25 feet. Consequently, the groundwater elevations are also relative. The groundwater gradient was calculated from groundwater Elevation data obtained during each of the two sampling rounds. On March 8, 1991, the gradient was calculated to be 0.0016 ft/ft at a direction of north 200 west. On April 11, 1991, the gradient had a magnitude of 0.0017 ft/ft at a direction of north 22° west. Figure 3 presents the groundwater elevations and gradient as of March 8, 1991. 3.0 ANALYTICAL RESULTS Analytical results are summarized in Table 1. The complete analytical report is presented in Appendix B. 3.1 Groundwater_SampleResull;.g As noted in Section 2.2, groundwater samples were collected from monitoring wells MW- i Y 1, MW-2 and MW-3 during two separate sampling rounds. Samples collected March 8, 1991 were analyzed for BTEX, TPH-G and Total Lead. None of these samples exhibited detectable concentrations of BTEX or TPH-G. MW-1 and MW-3 exhibited trace concentrations of total lead, containing 0.0082 mg/L and 0.0075 mg/L, respectively. The second round of samples collected April 11, 1991 confirmed the results of the first sampling round. These samples were analyzed for BTEX and TPH-G and no detectable concentrations of these compounds were found. 3.2 QUalily Control/Quality Assurance Results The trip blank sample which accompanied the March 8 samples was analyzed for BTEX and showed no detectable concentrations. During the April 11 sampling, an equipment decontamination sample EB-1 was collected. This sample was analyzed for BTEX and exhibited no detectable concentrations, indicating that the equipment decontamination procedures were thorough. - 6 -