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Appendix A:Previous Environmental Activities <br /> The estimated excess lifetime cancer risk of 2E-06 for potential on-site residents is within the <br /> lower end of the risk management range of 1 E-06 to 1 E-04 established by Cal/EPA and EPA. <br /> Potential non-cancer health hazards are below the de minimis levels. The results of the HHSE <br /> indicated that exposure to chemicals present in on-site soils and groundwater at the Site should <br /> not result in unacceptable health risks for a potential adult or child resident. The ecological <br /> screening evaluation indicated that threatened or endangered species have not been historically <br /> observed within 1 mile of the Site. Therefore, SAIC concluded no remedial action is necessary <br /> at the Site to protect human or ecological health, and a risk management decision of no further <br /> action required(NFAR) can be made for on-site affected soils and groundwater. <br /> The Central Valley RWQCB concurred with the findings of the HHSE and supporting <br /> documentation that the Site is a candidate for closure,and recommended that a soil and <br /> groundwater management plan be developed. The Central Valley RWQCB also requested <br /> preparation of an NFAR Request Report2 . <br /> SAIC 2012 SUPPLEMENTAL WELL SEARCH REPORT 23 <br /> SAIC conducted additional research to establish the locations of three wells identified in DWR <br /> Well Drillers Reports during a well search in 2010. Enough additional information was obtained <br /> to approximate the locations of two of the wells. The third well could not be located due to <br /> insufficient and conflicting information. <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 24 which was subsequently accepted by the Central Valley <br /> RWQCB 25. A subsurface investigation was conducted in 2012 and a soil and <br /> groundwater investigation report submitted in early 2013 26. An HHSE was <br /> recommended as the next step in moving the Ahern Road-Vernalis site towards closure. <br /> • Vernalis Pump Station: The former Vernalis Pump Station is located at the southeast <br /> corner of Highway 33 and Welty Road. The former pump station,part of the former <br /> OVP system, was investigated by SAIC and others between 1995 and 2008. Five <br /> groundwater monitoring wells associated with the site were properly destroyed by SAIC <br /> in 2009.27 SAIC completed an HHSE of the subject property in 2010, in which results <br /> 22. Central Valley RWQCB,2012. Review-Human Health Screening Evaluation, US Can—Welty Road, Vernalis,San Joaquin <br /> County.May 8. <br /> 23. SAIC,2012. Supplemental Well Search Report, US Can—Welty Road,35275 Welty Road, Vernalis,San Joaquin County, <br /> California.November 20. <br /> 24.SAIC-Benham,2010. Soil and Groundwater Investigation Work Plan,Ahern Road-Vernalis, Vernalis,San Joaquin County, <br /> California. August. <br /> 25.Central Valley RWQCB,2010. Review—Soil and Groundwater Investigation Work Plan,Ahem Road—Vemalis,Vemalis, <br /> San Joaquin County. September 9. <br /> 26.SAIC,2013. Soil and Groundwater Investigation Report,Ahern Road-Vernalis,35500,Vernalis,San Joaquin County, <br /> California. March 29. <br /> 27.SAIC,2009. Groundwater Monitoring Well Destruction Report, Vernalis Pump Station,35500 Welty Road,Vernalis, <br /> California. August. <br /> A-9 SAIC <br />