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Phase 11 Environmental Site Assessment Report <br />WESTLAKE SUBDIVISION VILLAGE E, G, H, I AND J <br />Regatta Lane <br />Stockton, California <br />WKA No. 13221.02 <br />July 27, 2021 <br />Page 4 <br />soil were analyzed for OCPs and total arsenic. Table 1 — Sample Analysis Schedule lists the <br />composited and discrete samples analyzed. CLS completed the analyses on a two -business <br />day turnaround for providing laboratory reports. <br />5.0 FINDINGS <br />Table 2 reveals that three OCPs, 4,4 dichlorodiphenyldichloroethylene (4,4 DDE), 4,4 <br />dichlorodiphenytrichoroethane (4,4 DDT), and endrin aldehyde were present in some of the <br />samples analyzed. Table 3 lists the maximum concentration of the three OCPs that were <br />detected in soil and the HERO Note 4 exposure threshold concentration for residential soil. <br />Table 4 shows no OCP detected in soil exceeded its HERO Note 3 threshold. <br />Table 3 <br />Comparison to HERO Note 3 Exposure Thresholds <br />OCP <br />Maximum Detection <br />p9/k9 <br />HERO Note 3 Threshold <br />p9/k9 <br />4,4 DDE <br />84 <br />2,000a <br />4,4 DDT <br />28 <br />1,900a <br />Endrin aldehyde <br />99 <br />19,000a <br />Notes: OCP Organochlorine pesticide <br />pg/kg micrograms per kilogram <br />HERO Note 3 residential cancer endpoint <br />Table 4 shows the arsenic concentrations in shallow soil ranged between less than the reporting <br />limit of 2 milligrams per kilogram (<2 mg/kg) to 4.4 mg/kg. Deeper soil revealed a range in <br />arsenic concentrations between <2 mg/kg to 5.5 mg/kg. WKA compared the total arsenic <br />concentrations in soil to data regarding the expected background arsenic concentration in soil <br />within the area of California 2. The comparison revealed the reported arsenic concentrations do <br />2 Smith, D.B., Cannon, W.F., Woodruff, L.G., Solano, Federico, and Ellefsen, K.J., 2014 Geochemical and <br />mineralogical maps for soils of the conterminous United States: U.S. Geological Survey Open -File Reprot <br />2014-1082, 386 p., http://dxdoi.org/10.3133/ofr2Ol41082. NM <br />