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Sampling and Analysis Plan for Phase II Environmental Site Assessment South Pointe Property: 701, 705, 833, 855 West Weber Avenue Stockton, California Background May 17, 2021 The distribution of elevated concentrations of OCPs and lead in shallow soils was observed to be non- uniform, with elevated concentrations generally observed at various depths between ground surface and 5 ft bgs. WKA attributed this condition to mixing of surface soils with building demolition debris during previous building demolition and site grading activities. This is supported by field observations whereby unconsolidated building debris was found to be mixed with apparently native soils in the upper 5 ft bgs across the site. Several areas were identified where OCPs and/or lead extend deeper than 5 ft bgs, and as deep as 9 ft bgs. Based on these data, WKA developed a conceptual remediation plan for the site, which is illustrated on WKA Figure 7, included in Appendix A. This figure illustrates portions of the site (and the adjacent Promenade property)where COCs in soil exceeded then-current risk-based screening criteria. Summary data tables produced by WKA are also included in Appendix A; however, please note that Stantec has edited the tables to compare data against current screening criteria (DTSC Screening Levels [SLs], June 2020). For compounds with no established SLs, Stantec has substituted USEPA Regional Screening Levels (RSLs). Concentrations of COCs that exceed screening criteria are highlighted in yellow on the tables included in Appendix A. Based on review of the 2008 investigation report, sampling was performed using standard and appropriate methods, samples were collected into laboratory-supplied containers, and chemical analyses were performed using appropriate USEPA-approved analytical methods by an accredited analytical laboratory. The 2007 data set is therefore considered to be of sufficient quality for reliance as a basis for scoping additional assessment activities. Maximum detected concentrations of each analyte, and pertinent risk-based screening criteria, are summarized in Table 2-1 below. Table 2-1 Maximum Detected Concentrations of Constituents of Concern Soil Matrix Analytical Parameter Laboratory (Contaminants of Analytical Results Regulatory Limit(specify) Concern) (units) Motor oil 920 mg/kg 12,000 (Residential ESL) Acetone 170 pg/kg 6.1E+07 pg/kg (Residential RSL) Methylene Chloride 10 pg/kg 2.2 pg/kg (Residential SL) Anthracene 2,300 pg/kg 17,000 pg/kg (Residential SL) Benzo(a)anthracene 1,100 pg/kg 1,100 pg/kg (Residential SL) Benzo(a)perylene 560 pg/kg Not Established Benzo(b)fluoranthene 2,200 pg/kg 1,100 pg/kg (Residential SL) Benzo(a)pyrene 1,600 pg/kg 110 pg/kg (Residential SL) �1 Project No.: 185704833.5.3&5.4 2.4