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Remediation Plan Cleanup and Abatement Order No 5-00-707 EAI Project No 1232 3.0 CURRENT GROUND WATER CONDITIONS ' 3.1 Ground Water Elevation Ground water beneath the Unocal and Wards sites has been segregated into shallow and deep water zones Shallow zone wells extend across the water table and generally are screened from 30 to 50 feet below grade surface (bgs), and deep zone wells are generally screened between 50 ' and 70 feet bgs (see Table 1) All Wards wells are screened in the Unocal deep zone Figures 3 and 4 present ground water elevation contour maps for both the shallow (Figure 3) and deep (Figure 4) zones at the sites Two additional wells designated as shallow (MW-23S and MW-24S) are screened between approximately 85 and 90 feet bgs and two additional wells designated as deep (MW-23D and MW-24D) are screened between approximately 98 to 103 feet bgs (see Figure 2 and Table 1) The shallow and deep screened intervals in these four wells do not correspond to the shallow and deep intervals in the other wells Therefore, data obtained from these four welts are not ' included in the shallow or deep zone ground water elevation maps or isoconcentration maps Ground water elevations in these wells indicate that they are screened in the same water bearing zone ' 32 Ground Water Flow Direction and Magnitude Figure 6 presents the historic ground water flow direction and magnitude for the two sites During the summer months when the RIW was formerly in operation, ground water flows from both the Unocal and Wards sites toward the RIW During the winter months when the RIW is not in operation, the natural ground water flow direction is easterly The RIW was shutdown on August 22, 2000, and has not been used since 33 Shallow and Deep Monitoring Yro ra Well H dhs g p Figures 7 and 8 present hydrographs for selected shallow and deep ground water monitoring wells These figures also indicate a reversal of ground water flow direction during summer months when the RIW was formerly in operation 3.4 TPH-G and Benzene Isoconcentration Maps P Fiuitreq A ani 10 nrPSQnt shallow and cif-(-n TPH-C isnrnnPntratlnn rnanc fnr the srtP respectively Figure 9 indicates that one shallow zone well had a detectable TPH-G ' concentration above the laboratory detection limit of <50 µg/L (MW-18 at 50 µg/L) In the deep zone, the highest concentration of TPH-G was in well MW-25D (136,000 µg/L on March 27, 2001 and 32,300 pg/L on May 30, 2001) Figures 11 and 12 present shallow and deep benzene i so concentration maps for the Site, respectively Benzene was detected in two shallow zone wells during the May 2001 sampling 135 1232P RAP Ano -4- ' ENVIRONMENTAL AUDIT, INC