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Appendix B: Previous Environmental Activities through SB-25, SB-29, and SB-42 at levels ranging from 110 µg/L to 130,000 gg/L. PAHs were detected above screening levels in five of 16 groundwater sampling locations. BTEX were not detected above screening levels. Borings SB-38 through SB-41 and SB-43 were transferred to the Ahern Road—Vernalis site (see below). SAIC 2009 CENTRAL VALLEY RWQCB SPLIT GROUNDWATER SAMPLING EVENT Prior to issuing approval to destroy wells MW-I 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 µg/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 18 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 µg/L, respectively. Benzo(a)pyrene was detected in excess screening levels in all of the groundwater samples with concentrations ranging from 0.0032 µg/L (SB-44) to 0.021 µg/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. ADJACENT PROPERTIES • Ahern Road—Vernalis: SAIC proposed separating the off-site portion of the site investigation area northwest of the property boundary. Ahern Road—Vernalis includes borings SB-38 through SB-41 and SB-43. SAIC prepared a soil and groundwater investigation work plan 19 which was subsequently accepted by the Central Valley RWQCB 20. The site investigation is currently pending. 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. 19.SAIC-Benham,2010. Soil and Groundwater Investigation Work Plan,Ahern Road-Vernalis, Vernalis,San Joaquin County, California. August. 20.Central Valley RWQCB,2010. Review—Soil and Groundwater Investigation Work Plan,Ahern Road—Vernalis,Vernalis, San Joaquin County. September 9. B-7 SAIE.