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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 Sampling Design and Rationale May 17, 2021 4.0 SAMPLING DESIGN AND RATIONALE The purpose of the proposed investigation is to provide vertical delineation of OCPs and lead in soil and assessment of the presence of VOCs in soil vapor. Data will be compared to risk-based screening criteria protective of human health to allow for appropriate land-use planning associated with future redevelopment of the site. A secondary objective of proposed soil assessment activities is visual examination of subsurface materials for visual assessment of fill materials identified during previous investigations. Assessment activities will be completed by Stantec field staff working with an earthwork contractor(for soil sampling). Any cultural resource discoveries during field activities will follow the unanticipated discovery plan included as Appendix B. 4.1 SOIL SAMPLING Soil assessment activities will focus on areas where previous assessment did not fully define the vertical extent of OCPs in subsurface soils and fill materials. Lead concentrations will also be assessed based on historical data indicating the presence of elevated concentrations of lead in subsurface materials. Figures illustrating the previous assessment effort, as well as identified locations where vertical assessment is incomplete, are presented in Appendix A. To assess concentrations of OCPs and lead in soil, and to visually assess the presence of fill materials present above native materials, Stantec will advance 20 test pits at locations illustrated on Figure 4. Test pits will be advanced using a backhoe and recovered materials visually assessed for the presence of fill materials. Soils will be examined and samples collected from the backhoe bucket or from temporary soil piles placed on the ground. Samples will be collected into laboratory-supplied sample jars using a stainless-steel trowel. Three samples will be collected from each test pit: one sample from the mid-point of observed fill materials (or approximately two feet below grade if fill is not observed); one sample from the first foot of encountered native materials (or from approximately five feet below grade if fill materials are not encountered); and a third sample from the bottom of the test pit. The upper two samples will be analyzed for OCPs and lead. The third (deep)sample will be held by the analytical laboratory pending results of the sample collected from shallow native materials (or five feet below grade). If the `shallow native' sample reports concentrations of OCPs and/or lead exceeding screening criteria, the deep sample will then be analyzed. The holding time for OCP analysis in soil via EPA Method 8081 is 14 days, and the holding time for lead analysis in soil via EPA Method 6010 is six months. Stantec will coordinate with the laboratory and arrange for daily pickup of samples, ensuring results are reported within seven days of collection, allowing time for extraction and processing of additional samples within acceptable hold time. The proposed soil sampling schedule is summarized in Table 4-1. B Project No.: 185704833.5.3&5.4 4.1