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' Mr.Michael Oliphant—CEMC <br /> HHSE Addendum February 22,2012 <br /> Surland Homes-Bridle Creek Page 2 of 6 <br /> • Residential Scenario 1: DTSC requested this scenario utilize the maximum <br /> detected concentration of each constituent as the exposure point concentration <br /> (EPC). <br /> ' • Residential Scenario 2: DTSC requested this scenario utilize the second highest <br /> concentration of each constituent as the EPC. <br /> • Construction Worker Scenario: DTSC requested that this scenario evaluate site <br /> data from a construction worker exposure scenario. <br /> DTSC requested that the maximum and second highest concentrations of constituents of <br /> ' potential concern (COPCs) from the UPRR ROW sampling be selected as the EPCs for <br /> the residential scenarios to provide a conservative estimate for risk for the residential <br /> area. <br /> ADDITIONAL SCENARIOS <br /> SAIC evaluated cancer risks and non-cancer hazards under the three additional <br /> scenarios utilizing analytical data from borings B-1 through B-7 (Tables 1 through 3; <br /> Figure 1), advanced in 2007. SAIC analyzed soil samples collected from borings <br /> located in the UPRR ROW for metals in 2007 at the request of the DTSC. <br /> ' Metals are not standard analytes at Historical Pipeline Portfolio—Bakersfield to <br /> Richmond (HPP-BTR) sites because an evaluation of metals concentrations in San <br /> Joaquin Valley crude oil (SJV crude) and background soil samples indicated that the <br /> average metals concentrations in the SJV crude samples are similar or lower than metals <br /> concentrations in typical site soils, and metals concentrations in soil do not show a <br /> ' correlation with total petroleum hydrocarbons quantified as crude oil (TPHc) <br /> concentrations. SAIC concluded that metal concentrations in soil are not associated <br /> with crude oil (SAIC, 2007)2. <br /> ' SAIC compared the analytical results from borings B-1 through B-7 at the Site with the <br /> metals data presented in the metals evaluation for HPP-BTR sites, and found that the <br /> metals concentrations at the Site are typical of HPP-BTR sites. Nonetheless, at the <br /> ' request of the DTSC, metals were included in the risk evaluations presented below. <br /> However, arsenic concentrations detected in soil at the Site are believed to represent <br /> ' background concentrations; therefore, arsenic was not evaluated quantitatively in this <br /> HHSE addendum. Background concentrations in California have been reported ranging <br /> from 3.5 milligrams per kilogram (mg/kg)to greater than 12 mg/kg3; and arsenic was <br /> detected in every soil sample analyzed, at concentrations ranging from 3.7 mg/kg to <br /> 1 5.8 mg/kg. Arsenic concentrations in soil at the Site were all within and nearer to the <br /> ' 2. SAIC,2007. Presentation of Additional Metals Evaluation,Historical Pipeline Portfolio. May. <br /> 3. Bradford et al, 1996.Background Concentrations of Trace and Major Elements in California Soil,Kearny <br /> Foundation Special Report.University of California.March. <br /> ' Lawrence Livermore National Laboratory, 1995.Protocol for Determining Background Concentrations of Metals <br /> in Soil at Lawrence Berkeley National Laboratory.University of California.August. <br /> DTSC,2008.Determination of a Southern California Regional Background Arsenic Concentration in Soil. <br /> March. <br />