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GeolagualTufucfeslicc Page 13 Site Conceptual Model Report(2006 Revision) Valentine(Castle Motors) Project No 723 2 June 16,2006 ' the volume of water (ft) within each contour The cubic feet of water, in each zone, is then converted to liters and then multiplied by the average contaminant load within the contour This produces the mass of contaminant in each contour interval Table 2 in Appendix E contains the calculations for the three aquifer horizons ' A mass balance of 264 kg (582 lbs or 94 gal) of TPH-G contamination in groundwater was calculated 2.7 Groundwater Beneficial Uses The Regional Water Quality Control Board-Central Valley Region's Basin Plan designates ' the beneficial uses of groundwater in the San Joaquin Valley as domestic, municipal, industrial and agricultural supply Documentation of uses of the area's groundwater was completed in July 2000 when GTI performed a well survey for a 2,000-foot radius around the site The purpose of the survey was to locate any municipal, domestic, or agricultural wells within the 2,000-ft radius and to determine, if possible, the construction of these wells The well survey data is included as Appendix F ' To meet the survey objective,ective, the following tasks were performed o Geological Technics Inc personnel reconnoitered the site on July 18, 2000 to make a physical search for any wells in the area o Specific well logs were requested from the State of California Department of Water Resources (DWR) both to aid in identifying local wells and to specify their ' construction details The DWR well logs that were available for this area are included in Appendix F o Mr Eric Mar of the California Water Services Company (CWSC) was contacted regarding municipal wells serving the area Two active wells (including one CWSC municipal well) were located within the 2,000-foot ' radius search area Well details are shown in Table 1, Appendix F, and the approximate well positions are plotted on Map 1, Appendix F A designation for the beneficial use of groundwater in the vicinity of the subject property as domestic supply is appropriate based on the results of the receptor survey outlined above ' 2.8 Potential Effects of Residual Contamination The contamination described in Section 2 0 will persist in the environment if left in place ' When petroleum hydrocarbons are released to the soil they move deeper under the primary influences of gravity, groundwater flow patterns, and capillary action As the product reaches a fine grained unit or the water table it concentrates on the top of the unit or on the ' groundwater surface due to its lesser density In groundwater, petroleum constituents then dissolve from the pool into the groundwater to form a dissolved contaminant plume that migrates under the control of the groundwater gradient At the same time the dissolve