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reporting limits are also tabulated. These limits are generally below Industrial Thresholds but above Protection of Groundwater SSLs. Subsequent soil and groundwater samples were conducted during installation of Monitoring Well MW-13, which was located approximately 30 feet northwest of an OU 11 rail spur. Soil samples were collected at depths of 10 and 15 feet and analyzed for industrial solvents (Table 0U8-P, soil sample 23-1), and a groundwater sample was also collected and analyzed for industrial solvents (Table 0U8-P, water sample 23-1). Results are all ND. Laboratory reporting/detection limits are not tabulated. Petroleum/Solvents: Recommendations While there are only 14 detections out of 624 results, the combination of unidentified extractable hydrocarbons at concentrations exceeding Protection of Groundwater SSLs and tentatively identified semi-volatile organic compounds at concentrations up to 2.2 mg/kg indicates uncertainty with respect to potential petroleum- or solvent-related contamination. Because Kleinfelder already recommends sampling this area for metal-related contamination, Kleinfelder recommends including petroleum- and solvent-related analyses to resolve this uncertainty. It is anticipated that potential identified contamination would be mostly surf icial, assuming the likely rail-spur source, and would therefore be relatively easily removed sufficiently to obtain closure should it become necessary. Pesticides/Herbicides: Existing Data Eight soil samples were analyzed for organochlorine pesticides and chlorinated herbicides (Table OU11-PH, soil samples 6-6 through 6-13). These analyses yielded 288 results. Most were ND. Detections included 4,4'-DDE (1,500 ug/kg and 90 ug/kg), 4,4'-DDT (2,700 ug/kg), 2,4-0 (120 ug/kg), and 2,4-DB (240 ug/kg and 220 ug/kg). These concentrations are below industrial soil limits, but the DDE, DDT, and 2,4-D results are above Protection of Groundwater SSLs. Most ND reporting limits have not been tabulated. Those limits that have been tabulated are generally below Industrial Thresholds, except for those associated with a single sample that had anomalously high reporting limits. Reporting limits, however, are above Protection of Groundwater SSLs. Pesticides/Herbicides: Recommendations Pesticide/herbicide concentrations are below Industrial Thresholds and proposed construction includes a concrete cap; however, metal concentrations in soil exceed Protection of Groundwater SSLs. Kleinfelder therefore recommends collecting groundwater samples to confirm that these pesticide/herbicide concentrations have not impacted groundwater. It is anticipated that potential identified contamination would be mostly surficial, assuming the likely rail-spur source, and would therefore be relatively easily removed sufficiently to obtain closure should it become necessary. 20173951.001A/SAC17R68420 Page 22 of 26 November 2, 2017 © 2017 Kleinfelder www.kleinfelder.com KLEINFELDER 2882 Prospect Park Dr., Suite 200, Rancho Cordova, CA 95670 p 916.366-1701 f 916.366-7013