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Appendix B:Previous Environmental Activities <br /> 2. COPCs in a well must be stable or declining for at least eight consecutive events where <br /> the overall plume is defined. <br /> SAIC's review indicated that MW-4 and MW-5 should be destroyed. No COPCs were I <br /> historically detected above ESLs or WQOs in MW-5. Laboratory analytical results for all <br /> COPCs were at non-detect concentrations in MW-4 for the previous four sampling events. SAIC <br /> also recommended the destruction of MW-3, based on declining TPHd concentrations. <br /> The Central Valley RWQCB agreed that MW-3 and MW-4 should be destroyed, provided that <br /> the results of one additional groundwater sampling event satisfied the monitoring-well I <br /> destruction criteria. The Central Valley RWQCB also recommended a final sampling event for <br /> MW-5. However, SAIC was allowed to proceed with the destruction.of MW-5 without <br /> additional sampling and analysis because continued access to the well for this purpose was <br /> denied by Western Farm Service, and because the well was unaffected by crude oil from the <br /> former OVP or TAOC pipelines.14 <br /> SAIC ANNUAL 2009 GROUNDWATER MONITORING AND SAMPLING" ' <br /> Annual groundwater monitoring and sampling was performed on February 11, 2009. The <br /> oleophilic sock in well MW-1 was replaced because it exhibited separate-phase oil (SPO) <br /> staining. Staining was not observed on the oleophilic sock in MW-2, and therefore the sock did <br /> not require replacement. SPO has been observed in MW-1 and MW-2 since 1999, with a total of <br /> 0.5 gallon removed from these wells as of the 2009 sampling event. I <br /> The groundwater sample from MW-3 had detections of TPHd and chrysene above ESLs or <br /> WQOs. A duplicate sample from MW-3 also reported concentrations of benzo(a)anthracene, <br /> chrysene, and pyrene above ESLs or WQOs. ' <br /> SAIC 2008-2009 MONITORING WELL DESTRUCTION AND SOIL AND <br /> GROUNDWATER INVESTIGATION16 <br /> SAIC completed MW-4 and MW-5 well destruction activities on August 7 and 8, 2008. In <br /> addition, SAIC advanced a total of 27 borings in three separate mobilizations (August 2008, <br /> November 2008, and March 2009) to delineate the extent of affected soil and groundwater at the ' <br /> site. The borings were advanced to total depths ranging from 10 to 88 feet bgs. <br /> Soil analytical results for TPHc exceeded EPA Regional Screening Levels (RSLs)17 and/or ESLs <br /> in borings SB-18, SB-20 through SB-26, SB-28, SB-29, and SB-34 with concentrations ranging ' <br /> from 540 mg/kg to 26,000 mg/kg. BTEX concentrations in excess of screening levels were <br /> detected in SB-21. PAHs were detected in excess of screening levels in 18 of the 27 borings. <br /> Groundwater samples were not collected from SB-20, SB-21, SB-28, SB-34, SB-38 through ' <br /> SB-41, and SB-43 due to the presence of SPO. TPHd concentrations were detected in excess of <br /> WQO and/or ESL screening levels in the groundwater samples from SB-18, SB-19, SB-22 ' <br /> 14.RWQCB,2007. Review of Second Quarter 2007 Groundwater Monitoring and Sampling Report—US-Can Welty Road <br /> Property,Vemalis,San Joaquin County. August 16. <br /> 15.SAIC,2009. Annual 2009 Groundwater Monitoring and Sampling Report, US Can–Welty Road,35275 Welty Road, <br /> Vernalis,California. April. <br /> 16.SAIC,2009. Monitoring Well Destruction and Soil and Groundwater Investigation Report, US Can–Welty Road,35275 <br /> Welty Road, Vernalis,San Joaquin County,California.September 24. ' <br /> 17.EPA,2008. Regional Screening Levels for Chemical Contaminants at Superfund Sites. <br /> http://www.ega.gov/reL,ion9/waste/sfund/yrg,/index.html# r able. September. <br /> B-6 SAIE <br /> f <br />