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Fourth Quarter 2001 Groundwater Monitoring and Sampling Report-CAO#5-00-707,Stockton,CA January 15,2002 ANALYTICAL TESTING The samples were delivered for analytical testing to Sequoia Analytical in San Carlos, California, a state certified laboratory (Certificate No 2360) Sequoia is certified for all tests completed as part of this investigation The samples were for analyzed for BTEX, MTBE, TBA, DIPS, ETBE, TAME, 1,2-DCA, and EDB by EPA Method 8260B, and TPH-G by modified EPA Method 8015 According to EAI in their Third Quarter 2001, Groundwatei Monitoring Report, dated November 9, 2001, "Pursuant to discussions with the RWQCB, the samples were not tested for ethanol or methanol" Analytical results are summarized in Tables I through 3, which include the historical and current analytical data for the sites The laboratory analytical report is included in Appendix B DISCUSSION Groundwater Elevation Contour Maps Unocal has segregated water at the sites into shallow and deep zones All Ward wells are screened in the Unocal deep zone Figures 3 and 4 present groundwater elevation contour maps for both the shallow (Figure 3) and deep (Figure 4) zones at the sites Shallow zone wells extend across the water table and • generally are screened from 30 to 50 feet bgs Deeper zone wells are generally screened between 50 and 70 feet bgs Table 1 A and Figure 5 present the well construction details in tabular form and graphically, respectively Two additional wells designated as shallow (MW-23S and MW-24S) are screened between approximately 85 and 90 feet bgs and three additional wells designated as deep (MW-8D, MW-23D and MW-24D) are screened between approximately 97 to 103 feet bgs The shallow and deep screened intervals in these five wells do not correspond to the shallow and deep intervals in the other wells Therefore, data obtained from these five wells are not included in the shallow or deep zone groundwater elevation maps or isoconcentration maps Groundwater Flow Direction and Magnitude Figure 6 presents the historic groundwater flow direction and magnitude for the two sites Dunng the summer months when the RIW was in operation, the groundwater flow direction for the Wards site was southwest and for the Unocal site it was generally south to southwest Figure 6 indicates that during the winter months when the R1W is not in operation, the natural groundwater flow direction is easterly, and during the summer months when the RIW was formerly in operation, groundwater flows from both sites toward the RIW Since operation of the RIW has been terminated, groundwater flow direction has been easterly during all seasons 240022 01-001 4