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Former Beacon Station No. 474 May 15, 2000 <br /> Stockton, California Results of Additional Subsurface Investigation <br /> below surface grade (bsg) in 1993 to approximately 68 feet bsg in 1996. Quarterly <br /> imonitoring in March 2000 indicated an average groundwater depth of approximately 55 feet <br /> bsg and a groundwater flow direction generally to the south and southeast under a gradient of <br /> approximately 0.004 feet/foot. <br /> ADDITIONAL SUBSURFACE INVESTIGATION <br /> The existing site-specific Health and Safety Plan was updated for the proposed fieldwork. <br /> Well permits were obtained from the SJCEHD (Appendix A). Prior to mobilization, <br /> Underground Service Alert (USA) was notified to identify and mark the locations of <br /> underground utilities. <br /> The additional subsurface investigation consisted of the drilling and installation of monitoring <br /> wells MW-10, MW-11, MW-12, vapor extraction well VW-7, air sparge well AS-1, as <br /> shown on Figure 2, and vapor extraction and air sparge well testing. The original proposed <br /> location for monitoring well MW-10 in the Work Plan Addendum letter was in the East Main <br /> Street right-of-way. Because of location conflicts with underground utilities and <br /> encroachment permit limitations, monitoring well MW-10 was re-located inside site property <br /> lines adjacent to the proposed location. <br /> The installation of the groundwater monitoring, vapor extraction and air sparge wells was <br /> completed on October 18 to 22, 2000. Horizon Environmental Inc. Field Methods and <br /> Procedures are contained in Appendix B. Boring/Well Completion Logs and Boring Log <br /> Symbol Key are contained in Appendix C. <br /> Monitoring wells MW-10 and MW-11 were located northwest and south of the dispenser <br /> island area to delineate the lateral extent of gasoline constituents in groundwater. Soil boring <br /> B7 (monitoring well MW-12) was drilled north of the dispenser islands to investigate vertical <br /> extent of soil environmental conditions to depths of the historical low groundwater level at <br /> 1474.22rpt 3 HORIZON ENVIRONMENTAL INC. <br />