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Phase 11 Environmental Site Assessment Report Page 4 WESTLAKE SUBDIVISION VILLAGE E, G, H, I AND J Regatta Lane Stockton, California WKA No. 13221.02 July 27, 2021 soil were analyzed for OCPs and total arsenic. Table 1 — Sample Analysis Schedule lists the composited and discrete samples analyzed. CLS completed the analyses on a two-business day turnaround for providing laboratory reports. 5.0 FINDINGS Table 2 reveals that three OCPs, 4,4 dichlorodiphenyldichloroethylene (4,4 DDE), 4,4 dichlorodiphenytrichoroethane (4,4 DDT), and endrin aldehyde were present in some of the samples analyzed. Table 3 lists the maximum concentration of the three OCPs that were detected in soil and the HERO Note 4 exposure threshold concentration for residential soil. Table 4 shows no OCP detected in soil exceeded its HERO Note 3 threshold. Table 3 Comparison to HERO Note 3 Exposure Thresholds OCP Maximum Detection HERO Note 3 Threshold N9/k9 N9/k9 4,4 DDE 84 2,000a 4,4 DDT 28 1,900a Endrin aldehyde 99 19,000a Notes: OCP Organochlorine pesticide pg/kg micrograms per kilogram a HERO Note 3 residential cancer endpoint Table 4 shows the arsenic concentrations in shallow soil ranged between less than the reporting limit of 2 milligrams per kilogram (<2 mg/kg) to 4.4 mg/kg. Deeper soil revealed a range in arsenic concentrations between <2 mg/kg to 5.5 mg/kg. WKA compared the total arsenic concentrations in soil to data regarding the expected background arsenic concentration in soil within the area of California'. The comparison revealed the reported arsenic concentrations do 2 Smith, D.B., Cannon, W.F., Woodruff, L.G., Solano, Federico, and Ellefsen, K.J., 2014 Geochemical and mineralogical maps for soils of the conterminous United States: U.S. Geological Survey Open-File Reprot 2014-1082, 386 p., http://dxdoi.org/10.3133/ofr2Ol41082. NM