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k <br /> December 16, 1992 ���� <br /> Unocal Service Station No 6981, Stockton, California Working To Restore Nature <br /> I <br /> Vapor-F traction Well Installation <br /> our va or-extraction- wells (VW-1 through VW-4) were installed in Four borings near t4d' <br /> stank c6rnplel— d-disptns-e- 1sTan_s (Plate 2) These wells were used to conduct a vapor- <br /> extractlon test (discussed in Vapor-Extraction Test section) Details on the construction of <br /> the vapor-extraction wells are summarized in Table 2 and are shown on the Logs of Borings <br /> (Appendix B) <br /> Assessment of Ground Water <br /> Ground-Water Monitoring Well Construction <br /> ro delineate the extent of dissolved hydrocarbons in ground yvater. eight gr_ouxid-water? <br /> O l monttoting wells (MW-1 through MW-B) were installed onsite and five .ground-wafer <br /> monitoring wells were installed offsite (MW-9 through MW--M (Jrne onsrte boring was 7 <br /> (converted to a pumping test well (PTW-1)1 Monitoring wells MW-1 through MW-5 were <br /> installed in January and February 1990 MW-6 through MW-8 were installed in March 1992 <br /> and MW-9 through MW-13 and PTW-1 were installed in August 1992 Details on the <br /> construction of the wells are summarized in Table 2 and are shown on the Logs of Borings <br /> (Appendix B) <br /> Before ground-water monitoring wells MW-10, MW-11, and MW-12 were installed, the <br /> borings were drilled to dust above ground water and a Hydropunch sampling device was <br /> driven into the saturated sediments Ground-water samples were collected with the <br />! Hydropunch and analyzed for hydrocarbons prior to the completion of the wells Because <br /> dissolved hydrocarbon concentrations were below the laboratory's limits of detection for all <br /> petroleum analytes, the borings were completed as monitoring wells to establish a"zero-line" <br /> for the dissolved hydrocarbon plume <br /> • <br /> 38032-10 6 <br /> 1 <br />