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1 <br />' mgfkg to 7 4 m The Residential and Industrial PRGs for arsenic are 0 06 mg/kg and <br /> lig <br />' 0 25 mg/kg respectively These values are considered to be very conservative The range <br /> of concentrations of arsenic detected in soil at the site is not uncommon for naturally <br /> occurring arsenic in California soils and is not considered indicative of a release <br />' 6.2 GROUNDWATER R WATER ANALYTICAL RESULTS <br />' For purposes of this discussion, groundwater analytical data has been compared to <br /> California Maximum Contaminant Levels (MCLs) MCLs are components of the <br />' drinking water standards adopted by the California Department of Health Services (DHS) <br /> pursuant to the California Safe Drinking Water Act Primary MCLs are derived from <br />' health-based criteria (Public Health Goals or from one-in-a-mullion (10 6) incremental <br /> cancer risk estimates for carcinogens and threshold toxicity levels for non-carcinogens) <br />' MCLs also include technologic and economic considerations based on the feasibility of <br /> achieving and monitoring for these concentrations in drinking water supply systems and <br /> at the tap MCLs have been used as screening level criteria only to assess the potential <br />' impact to groundwater beneath the site from a beneficial use standpoint <br /> As indicated previously in Section 5 3 the organic constituents detected in the <br />' groundwater samples analyzed included the following <br />' • TPH-diesel, • bis (2-ethylhexyl) phthalate, <br /> • PCE, • cis-l,2-dichloroethene, and <br />' <br /> * TCE, • trans-1s 2,-dichloroethene <br />' TPH as diesel was detected in two monitoring wells, MW-1 and MW-2, at concentrations <br /> of 55 µg11 and 75 µg11 respectively There is currently no established Primary MCL for <br />' TPH as diesel in groundwater <br /> PCE was detected in groundwater samples from all four monitoring wells at <br />' concentrations ranging from 5 1 µg/l in MW-1 to 150 µgll in MW-4 All four PCE <br /> concentrations exceed the Primary MCL of 5 0 µg11 for PCE Additionally TCE was also <br />' detected in all four groundwater samples at concentrations ranging from 0 98 11g11 in <br /> MW-3 to 6 3 µg11 in MW-4 The concentration of TCE to MW-4 (6 3 µg11) exceeds the <br />' Primary MCL for TCE of 5 0 µg11 In addition to PCE and TCE, cis-l,2-dichloroethene <br /> and trans-l,2-dfchloroethene were detected in the groundwater sample from monitoring <br />' 12 V\Goodwin ProctoAFinalReport doc <br />