ARCHIVED REPORTS HUMAN HEALTH SCREENING EVALUATION

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Human Health Screening Evaluation Surland Homes—Bridle Creek February 12,2009 benzo(k)fluoranthene, indeno(1,2,3-cd)pyrene, antimony, cadmium, hexavalent chromium, selenium, silver, and thallium. Arsenic was detected in every soil sample analyzed, at concentrations ranging from 3.6 milligrams per kilogram (mg/kg) to 5.8 mg/kg. Background concentrations in California have been reported ranging from 3.5 mg/kg to greater than 12 mg/kg (Bradford et al, 1996, Lawrence Livermore National Laboratory, 1995, DTSC, 2008). Arsenic is unlikely to be associated with crude oil. Arsenic concentrations in soil at the site were all within and nearer to the low end of the range of background concentrations. Arsenic concentrations detected in soil at the site are believed to represent background concentrations; therefore, arsenic was not evaluated quantitatively in this HHSE. ' 3.1 ON-SITE SOIL IMPACTS AND EXPOSURE POINT CONCENTRATIONS Impacts to on-site soils were characterized, with regulatory oversight provided by the RWQCB. Two site characterization studies were conducted: the first in 1998 and the second in 1999. These studies were followed by groundwater monitoring. Further site characterization was performed in 2007 at the request of the DTSC. A total of 23 soil samples were collected from 15 soil borings at depths ranging from 1 foot bgs to 12 feet bgs, and were used to evaluate risks and hazards in this HHSE. Soil samples were collected along the location of the former crude- oil pipeline, and within the area now part of the Surland Homes—Bridle Creek development. The 1 study conducted by SAIC in 2007 specifically included the collection of on-site soil samples to support the development of this HHSE. Data was collected at depths corresponding to requests from the DTSC. Soil samples were collected at 1 foot bgs, and between 9.5 and 12 feet bgs, which corresponded to the occurrence of groundwater during the 2007 investigation. Soil samples were analyzed using methods of sufficient analytical quality (e.g., low detection limits) to support this HHSE. A summary of the analytical results for BTEX, PAHs, and metals in soil is provided in Tables 1 through 3. Exposure point concentrations (EPCs) were calculated as the upper confidence limit (UCL) of the mean soil concentration for each of the COPCs. An EPA statistical software program, ProUCL Version 4.00.02 (EPA, 2007), was used to analyze the datasets presented in Tables 1 through 3. All COPCs (with the exception of some metals) had a high level of non-detect concentrations. Therefore, as recommended in the ProUCL User's Guide (EPA, 2007), nonparametric statistical methods were used to develop the EPCs where appropriate. For data sets with multiple detection limits, Kaplan-Meier nonparametric estimation methods were deemed most appropriate, as recommended by Singh et al. (EPA, 2007). The total number of soil samples analyzed, the total number of samples with detectable concentrations, and the EPCs for all soil COPCs evaluated in this HHSE are provided in Table 4. 3.2 ON-SITE GROUNDWATER IMPACTS Groundwater samples were also collected and analyzed for COPCs during the 1998 site characterization study, and during subsequent groundwater monitoring. The analytical results for BTEX and PAHs for all groundwater samples are provided in Appendix B. Analysis of the 5 � From Se)vxe fo Soiubons