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AM ruga Working to Restore Nature Appendix D The depths to groundwater in the monitoring wells were measured during i each sampling event These depths to groundwater were combined with the top of the well casing elevations to evaluate the elevation of the groundwater surface in each well We then used these data to prepare potentiometnc maps depicting the groundwater gradient and direction of groundwater flow Potentiometnc information is presented in the Site Hydrogeology section of this report. 4_3 Vapor Extraction Well Installation In May 1992, three vapor extraction wells (VW-1 through VW-3) were installed in borings B-9, B-10, B-11, respectively Following the vapor extraction test on July 14, 1992, four vapor extraction wells (VW-4 through VW-7) were installed in borings B-13 and B-17 through B-18, respectively. Well locations are shown on Plate 2 Details on the construction of the vapor extraction wells are described in Table 3 and shown on the Logs of Borings (Appendix B). 4 4 Vapor Extraction Test On July 14, 1992, RESNA performed a vapor extraction test to collect site-specific data and evaluate the feasibility of vapor extraction as a remediation alternative for vadose soil (RESNA, December 18, 1992) RESNA used an internal combustion(I.C) engine and wells VW-1, VW-2, VW-3, and MW-3 during the test. Results of the test indicated the I C engine has a destruction efficiency greater than 95 percent Based upon the vacuum response data and the analytical results of soil gas samples, vapor extraction in the vicinity of the groundwater surface and within the sand zone (33 to 40 feet bsg) appears feasible with wells VW-1 through VW-3 We estimate that an effective radius of influence in excess of 50 feet can be expected for this zone, using an extraction flowrate of 25 cubic feet per minute or greater +� 31009-10 6 r