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Surface Water and Well Survey and CPT Investigation Report CAM B R 1A BP Oil Site No 11193 Stockton, California December 16, 1999 Short-Term Groundwater Extraction Groundwater extraction from wells MW-1R and MW-2R during four weekly events is planned Extracted groundwater will be pumped into a temporarily onsite storage tank and either discharged to the sanitary sewer or storm drain, or transported offsite for recycling To assess concentration trends and evaluate mass removal, groundwater samples will be collected prior to and following the four events, and analyzed for GRO using modified EPA Method 8015, and BTEX and MTBE using EPA Method 8020 Additional Investigation The results of this CPT investigation and recent groundwater monitoring indicate that the lateral extent of BTEX constituents and TAME have been defined to f detection limits, and GRO and MTBE have been defined to less than 140 µg/l Vertical profiling indicates that MTBE concentrations decrease with increasing depth The sampling results also indicate that MTBE is largely restricted to the upper 30 feet of the subsurface except near the underground storage tanks Additional vertical definition of the extent of MTBE below 30-35 feet bgs may be warranted and is recommended only following initial reduction of concentrations in shallow groundwater beneath the site ATTACHMENTS Figure 1 —Vicinity Map Figure 2—Soil Boring Location Map Table 1 --Well Survey Data Table 2--Soil Analytical Data Table 3 —Grab Groundwater Analytical Data Table 4—Groundwater Analytical Data Appendix A—Background Data Appendix B —Well Survey Data Appendix C—Standard Field Procedures for Cone Penetrometer Testing and Sampling Appendix D—Permits,Bonng Logs, and CPT Logs Appendix E—Analytical Results 11SERVER11R1Bntish Petroleum111193-StocktonlReportlCPT Investigation Report doc 10