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Appendix A:Previous Environmental Activities WFSMW-l. Sampling of WFSMW-1 was discontinued in August 2007. Wells MW-4 and MW-5 were destroyed in August 2008. The final annual groundwater monitoring and sampling event was performed on February 11, 2009. The oleophilic sock in well MW-1 was replaced because it exhibited SPO staining. Staining was not observed on the oleophilic sock in MW-2, and therefore the sock did not require replacement. SPO had been observed in MW-1 and MW-2 since 1999, with a total of 0.5 gallon removed from these wells as of the final sampling event. The groundwater sample from MW-3 had detections of TPHd and chrysene above ESLs or WQOs. A duplicate sample from MW-3 also reported concentrations of benzo(a)anthracene, chrysene, and pyrene above ESLs or WQOs. SAIC 2009 CENTRAL VALLEY RWQCB SPLIT GROUNDWATER SAMPLING EVENT Prior to issuing approval to destroy wells MW-1 through MW-3,the Central Valley RWQCB requested an additional event where split samples would be collected and submitted to an independent laboratory. On July 15, 2009, SAIC and Central Valley RWQCB staff collected split groundwater samples from MW-3. Concentrations of TPHd were reported at 63 gg/L and no compounds were reported above the respective screening levels in the SAIC sample. The Central Valley RWQCB sample indicated a TPHd concentration of less than 100 gg/L, which was similar to SAIC's result. No COPCs were detected in the Central Valley RWQCB sample. SAIC 2010 MONITORING WELL DESTRUCTION AND SOIL AND GROUNDWATER INVESTIGATION'8 SAIC completed MW-1 through MW-3 well destruction activities on July 14 through July 16, 2010. In addition, SAIC advanced a total of four soil borings(SB-44 through SB-47) to 45 feet bgs on July 20 through July 22, 2010,to delineate the extent of affected soil and groundwater at the Site. Soil analytical results for naphthalene exceeded RSLs in borings SB-46 (44.5 feet bgs) and SB-47 (34.5 feet bgs) with concentrations of 0.00073 mg/kg and 0.00084 mg/kg,respectively. There were no other detections of TPHc, BTEX, or PAHs in excess of screening levels. TPHd concentrations were detected in excess of WQO and/or ESL screening levels in the groundwater samples from SB-46 and SB-47 at 3,100 gg/L and 100 gg/L, respectively. Benzo(a)pyrene was detected in excess screening levels in all of the groundwater samples with concentrations ranging from 0.0032 gg/L(SB-44) to 0.021 gg/L(SB-47). Dibenz(a,h)anthracene was detected in excess of screening levels in the groundwater sample from SB-47 at a concentration of 0.0068 gg/L. No other PAHs or BTEX were detected above screening levels. SAIC conducted a search of DWR files to identify water-supply wells within a 2,000-foot radius of the Site. A total of nine water-supply wells were identified within the search area. Two of the wells could not be accurately located due to insufficient information. A third well was presumed 18.SAIC,2010. Monitoring Well Destruction and Soil and Groundwater Investigation Report, US Can—Welty Road,35275 Welty Road, Vernalis,San Joaquin County, California. December 28. A-7 SAIL