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Attachment A:Previous Environmental Activities southeast of the former OVP and TAOC alignments and SB-17 was not fully characterized. The area northeast of GMX-6 had likely been affected by a refined-fuel plume as a result of a leaking UST at the former Union Oil Service Station at the eastern corner of Welty Road and Highway 33. The service station operated from 1972 to the mid-1980s. SAIC 2007 MONITORING WELL DESTRUCTION EVALUATION In September 2007, SAIC used the following criteria to evaluate historical groundwater monitoring well sampling analytical results to determine whether monitoring wells may be destroyed: 1. COPCs in a well must be less than WQOs and San Francisco Bay RWQCB Environmental Screening Levels (ESLs) 13 for at least last four sampling events; or 2. COPCs in a well must be stable or declining for at least eight consecutive events where the overall plume is defined. SAIC's review indicated that MW-4 and MW-5 should be destroyed. COPCs were not historically detected above ESLs or WQOs in MW-5. Laboratory analytical results for all COPCs were at non-detect concentrations in MW-4 for the previous four sampling events. SAIC also recommended the destruction of MW-3, based on declining TPHd concentrations. The Central Valley RWQCB agreed that MW-3 and MW-4 should be destroyed, provided that the results of one additional groundwater sampling event satisfied the monitoring-well destruction criteria. The Central Valley RWQCB also recommended a final sampling event for MW-5. However, SAIC was allowed to proceed with the destruction of MW-5 without additional sampling and analysis because continued access to the well for this purpose was denied by Western Farm Service, and because the well was unaffected by crude oil from the former OVP or TAOC pipelines.14 SAIC ANNUAL 2009 GROUNDWATER MONITORING AND SAMPLING15 Annual groundwater monitoring and sampling was performed on February 11, 2009. The oleophilic sock in well MW-1 was replaced because it exhibited separate-phase oil (SPO) staining. Staining was not observed on the oleophilic sock in MW-2, and therefore the sock did not require replacement. SPO has been observed in MW-I and MW-2 since 1999, with a total of 0.5 gallon removed from these wells as of the 2009 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. 13.San Francisco Bay RWQCB,2008 Screening for Environmental Concerns at Sites with Contaminated Soil and Groundwater(Interim Final). May. 14.RWQCB,2007. Review of Second Quarter 2007 Groundwater Monitoring and Sampling Report—US-Can Welty Road Property,Vernalis,San Joaquin County. August 16. 15.SAIC,2009. Annual 2009 Groundwater Monitoring and Sampling Report, US Can–Welty Road,35275 Welty Road, Vernalis, California. April.