ARCHIVED REPORTS_HUMAN HEALTH SCREENING SUPPORTING DOCUMENTS

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Mr.M. Scott Mansholt—CEMC Presentation of Additional Metals Evaluation May 25,2007 Historic Pipeline Portfolio Page 2 of 5 METHODOLOGY In order to determine whether the crude oil carried in the OVP and the TAOC lines could be contributing metals to the soil of HPP sites, SAIC conducted the following: 1. Calculated average metals concentrations in the oil samples and compared them to the background concentrations and SSLs. 2. Compared metals concentrations in soil samples to background concentrations and SSLs. 3. Used correlation analyses to evaluate any relationship between the metals and TPHc. The metals in oil concentrations are likely more accurate indicators of the contribution of metals from oil releases because soil samples have been influenced by a number of other natural and anthropogenic sources of metals. Analytical results for metals in soil and oil samples are presented in Table 1. METALS IN OIL SAMPLES Figure 1 shows the average metals concentrations in oil compared to the lowest background concentrations presented in the two background documents referenced previously and the lowest SSLs. The lowest background concentrations represent the lowest background value noted in either study; conversely,the higher background concentration represents the highest value noted in either study for a particular metal. The background values are presented in Table 1. Figure 1 illustrates that the average concentration of metals in oil is below the lowest background concentrations,with some exceptions (antimony, cadmium, selenium, silver, and thallium). The average metals concentrations were derived by assigning a concentration equivalent to the detection limit for oil samples with no detectable metals. Figure 2 shows that when the higher background numbers are used for comparison none of the metals exceed their background concentrations. Note that certain metal analytes in the oil samples exhibited elevated detection limits (molybdenum, silver, and thallium), and these elevated detection limits were not used in calculating the average metals concentrations. The average molybdenum concentration was 2.36 milligram per kilogram(mg/kg)using the detection limits for all non-detect samples. However,molybdenum was detected in only one oil sample at a concentration below the lowest background level. The average is therefore derived from samples where molybdenum was not detected, and several of the detection limits were elevated. The average without these elevated detection limits was 1.08 mg/kg;this falls below the lowest background concentration. Omitting the high detection limits for the silver analyses changed the average concentration from 1.9 mg/kg to 0.88 mg/kg; this brings the average silver concentration in oil to just below the lower background level. For thallium,the average concentration changed from 6.3 to 0.71 mg/kg. While still within the background range,the average thallium concentration in oil fell below the lowest SSL. Further, average metals concentrations in oil are less than the lowest SSLs,with the exception of arsenic (EPA Region 9 Preliminary Remediation Goals4 and Cal/EPA DTSC California Human Health Screening Levels5). The average arsenic concentration in the oil is lower than the lowest background concentration. Further, in SAIC's experience,the arsenic concentrations observed in the oil samples are lower than commonly observed arsenic concentrations in soil, and therefore the oil is not likely to increase arsenic concentrations in soil beyond background concentrations. 4. EPA,2004. Region 9 PRGs Table.hiip://www.epa.gov/region9/waste/sfund/prWindex.html# rgtable. October. 5. Cal/EPA DTSC,2005. Use of California Human Health Screening Levels in Evaluation of Contaminated Properties. January.