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Appendix B:Previous Environmental Activities <br /> through SB-25, SB-29, and SB-42 at levels ranging from 110 gg/L to 130,000 gg/L. PAHs were <br /> detected above screening levels in five of 16 groundwater sampling locations. BTEX were not <br /> Idetected above screening levels. <br /> Borings SB-38 through SB-41 and SB-43 were transferred to the Ahern Road—Vernalis site (see <br /> below). <br /> SAIC 2009 CENTRAL VALLEY RWQCB SPLIT GROUNDWATER <br /> SAMPLING EVENT <br /> fPrior to issuing approval to destroy wells MW-1 through MW-3, the Central Valley RWQCB <br /> requested an additional event where split samples would be collected and submitted to an <br /> independent laboratory. On July 15, 2009, SAIC and Central Valley RWQCB staff collected <br /> isplit groundwater samples from MW-3. Concentrations of TPHd were reported at 63 gg/L and <br /> no compounds were reported above the respective screening levels in the SAIC sample. The <br /> Central Valley RWQCB sample indicated a TPHd concentration of less than 100 gg/L, which <br /> was similar to SAIC's result. No COPCs were detected in the Central Valley RWQCB sample. <br /> SAIC 2010 MONITORING WELL DESTRUCTION AND SOIL AND GROUNDWATER <br /> ' <br /> INVESTIGATION" <br /> SAIC completed MW-1 through MW-3 well destruction activities on July 14 through July 16, <br /> 2010. In addition, SAIC advanced a total of four soil borings(SB-44 through SB-47)to 45 feet <br /> bgs on July 20 through July 22, 2010,to delineate the extent of affected soil and groundwater at <br /> the site. <br /> Soil analytical results for naphthalene exceeded RSLs in borings SB-46 (44.5 feet bgs)and <br /> SB-47 (34.5 feet bgs)with concentrations of 0.00073 mg/kg and 0.00084 mg/kg, respectively. <br /> There were no other detections of TPHc, BTEX, or PAHs in excess of screening levels. <br /> TPHd concentrations were detected in excess of WQO and/or ESL screening levels in the <br /> groundwater samples from SB-46 and SB-47 at 3,100 µg/L and 100 gg/L, respectively. <br /> Benzo(a)pyrene was detected in excess screening levels in all of the groundwater samples with <br /> ' concentrations ranging from 0.0032 gg/L(SB-44)to 0.021 gg/L (SB-47). <br /> Dibenz(a,h)anthracene was detected in excess of screening levels in the groundwater sample <br /> from SB-47 at a concentration of 0.0068 gg/L. No other PAHs or BTEX were detected above <br /> screening levels. <br /> ADJACENT PROPERTIES <br /> ' • Ahern Road—Vernalis: SAIC proposed separating the off-site portion of the site <br /> investigation area northwest of the property boundary. Ahern Road—Vernalis includes <br /> borings SB-38 through SB-41 and SB-43. SAIC prepared a soil and groundwater <br /> ' investigation work plan 19 which was subsequently accepted by the Central Valley <br /> RWQCB 20. The site investigation is currently pending. <br /> 18.SAIC,2010. Monitoring Well Destruction and Soil and Groundwater Investigation Report, US Can—WeltyRoad,35275 <br /> Welty Road, Vernalis,San Joaquin County, California.December 28. <br /> 19.SAIC-Benham,2010. Soil and Groundwater Investigation Work Plan,Ahern Road-Vernalis, Vernalis,San Joaquin County, <br /> California. August. <br /> 20.Central Valley RWQCB,2010. Review—Soil and Groundwater Investigation Work Plan,Ahern Road—Vernalis,Vernalis, <br /> San Joaquin County. September 9. <br /> B-7 <br /> SAIC <br /> 1 <br />