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Soil and Groundwater Investigation Report <br /> Mountain House Development Site#6 February 25,2010 <br /> It is important to note that,based on past experience at HPP-BTR project sites, attenuation of <br /> crude-oil constituents in groundwater occurs a very short distance from HPP-BTR facilities, and <br /> it is improbable that affected groundwater extends from the site as far as the Foster Well. In <br /> addition, the up-gradient position of the Foster Well in relation to the areas of known affected <br /> groundwater suggests that it is unlikely it will be affected by crude oil related to the former OVP <br /> or TAOC pipelines. <br /> 6. CONCLUSIONS AND RECOMMENDATIONS <br /> SAIC-Benham evaluated the results of this investigation and concludes the following regarding <br /> the nature and extent of affected soil and groundwater at the site: <br /> • Field observations and laboratory analytical results indicate that there are two areas of <br /> affected soil and groundwater which have been delineated, as shown on Figures 4a <br /> through 4c. <br /> • The extent of affected groundwater is stable or decreasing, and concentrations of <br /> dissolved constituents will gradually decrease as the petroleum hydrocarbon mass is <br /> depleted. The lack of BTEX in groundwater samples indicates that intrinsic <br /> biodegradation has been, and continues to be, active at this site. <br /> • Groundwater samples submitted during the current and previous investigations for <br /> General Minerals analysis had detections above the minimum WQOs or ESLs, and are <br /> thus considered to contain certain taste- or odor-producing substances in concentrations <br /> that cause nuisance or adversely affect beneficial uses. These exceedances indicate that <br /> the uppermost water-bearing zone is not suitable for drinking water use. <br /> Soil and groundwater have been effectively delineated at the site, and SAIC-Benham <br /> recommends performing a human health screening evaluation as a further step in the process of <br /> moving the site toward no further action required status. <br /> 7. REFERENCES <br /> California Office of Administrative Law, 2008. Official California Code of Regulations, Title <br /> 22, Division 4. July. <br /> Condor, 2001. Chevron Pipeline Easement Assessment Report-Mountain House, California, <br /> Volume I and 2. November. <br /> DWR, 2003. California's Groundwater Bulletin 118, Update 2003. October(specific basin <br /> update January 20, 2006). <br /> 2006. Lines of Equal Elevation of Water in Wells, Unconfined Aquifer, San Joaquin <br /> Valley. Spring. <br /> EPA, 2008a. Region 9 Preliminary Remediation Goals Regional Screening Level Table. <br /> http://www.epa._og v/region09/superfund/prg/index.html. September. <br /> 2008b. Test Methods for Evaluating Solid Waste, Physical/Chemical Methods. Update <br /> IV of the Third Edition. January. <br /> Geomatrix, 2005. Technical Approach to Site Evaluation and Decision Making, Historical <br /> Pipeline Portfolio, Central Valley Region. February. <br /> 9 <br /> Fmin Science to Solutions <br />