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Quarterly Groundwater Monitorin Repgrt <br /> Former E-Z Serve Location 100966 <br /> 2537 Waterloo Road <br /> Stockton California <br /> • Delta Project No RPMSO-966 <br /> Page 4 <br /> 30 CONCLUSIONS AND RECOMMENDATIONS <br /> 3.1 Conclusions <br /> Groundwater table elevation data were used to approximate the flow direction and gradient across the site <br /> on December 29, 2004 by contouring Monitoring wells MW-1, MW-2, MW-3, MW-4, MW-5, MW-6, <br /> MW-7, MW-8, and MW-16 are twenty to thirty feet deeper than monitoring wells MW-9, MW-10, MW- <br /> 11, MW-12, MW-13, MW-14, MW-15, MW-17, VW-1, VW-2, and VW-3 Data from the deeper wells <br /> were excluded for contouring because the top of their screens are below the water table Based on the <br /> contours presented on Figure 2 — Groundwater Contour Map, the flow direction was toward the west at a <br /> hydraulic gradient of approximately 0 001 <br /> Reported analytical data for the groundwater samples collected on December 29, 2004 indicate that <br /> benzene concentrations have remained below laboratory reporting limits (BRL) in all the deeper <br /> monitoring wells, as well as four downgradient shallow wells Of the seven shallow wells surrounding <br /> the UST location that reported above laboratory limits, two downgradient wells decreased in benzene <br /> concentration, one upgradient increased in benzene concentration, the other four wells were dry dunng 3`d <br /> • quarter sampling leaving no data for comparison Reported MTBE concentrations decreased in the deep <br /> well located in the UST location and did not change for the equivalent shallow well MTBE <br /> concentrations increased in two shallow wells and decreased in five deep wells, all located downgradient <br /> from the UST's <br /> 32 Recommendations <br /> Based on the above conclusions, Delta recommends continued quarterly groundwater monitoring and <br /> sampling Delta has submitted a work plan for the installation of down gradient monitonng wells The <br /> work plan is pending review at the San Joaquin County Department of Environmental Health <br /> S\Remediation Unit\Active Clients\Restructure Petroleum\Project Files1100966 2537 Waterloo Road\GWM\4th Qtr <br /> 2004\100966 4th04QMR doc <br />