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Working To Restore Nature <br /> 5.5 Well Development and Groundwater Sampling <br /> Well development and groundwater sampling included surveying the top of the wellheads and <br /> measuring depth to water in the wells to evaluate the direction and magnitude of the groundwater <br /> ' gradient beneath the site, developing the newly installed groundwater monitoring wells by <br /> pumping until they were relatively sediment free, purging the existing well by removing a <br /> ' minimum of four casing volumes of groundwater and verifying the stabilization of pH, <br /> temperature and electrical conductivity, and sampling the existing and three new monitoring <br /> wells to evaluate the extent of petroleum hydrocarbons in the first-encountered groundwater at <br /> the site Collected water samples were analyzed by Sequoia Analytical for BTEX, TPHg and <br /> TPHd utilizing EPA methods 8020 and 8015, respectively Analytical results are summarized <br /> in Table 3 Laboratory reports are presented in Appendix D Well purge logs are presented <br /> in Appendix E <br /> 6.0 INVESTIGATION RESULTS <br /> ' 6.1 Soil Lithology <br /> Soils encountered beneath the site consist of primarily well graded sand and well graded sand <br /> ' with silt to approximately 40 feet below grade Below 40 feet interbedded lenses of well graded <br /> to poorly graded sand with silt and clay, and elastic silt and sandy clay are present to 85 feet, <br /> ' the total depth explored Soil stratigraphy beneath the site is shown on Plate 4 <br /> 6.2 Laboratory Results - Soils <br /> Analytical results of soil samples collected in October 1993 indicate that soil impaction <br /> ' associated with the former u/g gasoline storage tanks is apparently limited to the immediate <br /> vicinity of the former tank locations and beneath the former fuel pump island No hydrocarbons <br /> ' were detected in any soil samples collected from borings MW-2, MW-3, MW-4 or VW-1 Very <br /> low levels of petroleum hydrocarbons were detected in samples VW-2-15 5' (1 3 ppm TPHg), <br /> VW-3-15 5' (0 012 ppm benzene, 1 5 ppm TPHg), and VW-3-45 5' (1 1 ppm TPHg) Method <br /> detection limits for benzene and TPHg are 0 005 and 1 0 ppm, respectively Analytical results <br /> ' 1500471it-031594 FNL 7 <br />