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Soil and Groundwater Investigation Report and <br /> Second Quarter 2005 Monitoring and Sampling,US Can-Welty Road October 2005 <br /> former Vernalis Pump Station. SAIC does not recommend additional soil and groundwater investigation <br /> southeast of boring SB-17 since the ongoing Vernalis Pump Station investigation has progressed <br /> northeast across Highway 33. The vertical extent of affected soil has been defined. <br /> Groundwater in the vicinity of WFSMW-1 and MW-5 appears to be delineated based on the April 2005 <br /> sampling event. However, groundwater has not been fully characterized down gradient of soil boring <br /> GMX-6 and the grab groundwater sample collected in November 1999 indicates that the lateral extent of <br /> dissolved-petroleum constituents emanating from the former OVP pipeline has been defined and further <br /> investigation northeast of GMX-6 is not warranted. Based on the groundwater results from the April <br /> 2005 sampling event, it appears dissolved-petroleum constituents are not affecting groundwater in the <br /> vicinity of WFSMW-1 or MW-5 at concentrations over the WQO. The area northeast of GMX-6 has <br /> likely been affected by a refined fuel plume as a result of a leaking UST,which the current property <br /> owner is responsible for. <br /> Based on well completion reports,the domestic wells identified were constructed with sanitary seals 20 <br /> feet bgs or greater and have screen intervals deeper than 70 feet bgs. In addition,there are no domestic <br /> wells located down gradient(east)of the site. <br /> SAIC recommends continued quarterly monitoring and sampling of wells MW-1 through MW-5, and <br /> WFSMW-1 through the second quarter of 2005. During the next several monitoring and sampling events, <br /> SAIC will request low detection limits for use in a future health risk assessment(HRA). SAIC will also <br /> have a professional risk assessor schedule a review of the March 2005 soil and groundwater investigation <br /> results in addition to past chemical analytical data for use in a future HRA. <br /> U REFERENCES <br /> California Department of Health Services: Drinking Water Source Assessment and Protection Program, <br /> Program Document, Section 7, dated January 1999. <br /> Department of Water Resources. Revised Draft Bulletin 118. <br /> Geomatrix Consultants,Inc. Second Draft Revised Technical Approach to Site Evaluation and Decision- <br /> Making, Old Valley Pipeline Sites(CTA), dated December 18, 2002. <br /> Geomatrix Consultants,Inc.Report of Off-Site Soil and Groundwater Investigation,November 2003 <br /> Geomatrix Consultants,Inc. Technical Approach to Site Evaluation and Decision Making;Historical <br /> Pipeline Portfolio, Central Valley Region,February 2005. <br /> Science Applications International Corporation(SAIC) Work Plan for Additional Soil Borings and <br /> Implementation of Quarterly Monitoring and Sampling at US Can/Welty Road, located at 35275 <br /> Welty road, Vernalis, California,March 2004. <br /> RWQCB-CVR. Taste and Odor Thresholds-RWQCB-CVR A Compilation of Water Quality Goals, <br /> Marshack, dated August 2000. <br /> 10 From Science to Solutions- <br />