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SUPPLEMENTAL SITE INVESTIGATION WORK PLAN South Pointe Property Stockton, California Conceptual Site Model identified several areas of modest accumulation of VOCs in the subsurface. Subsequent sampling via `active' methods (i.e. installation of soil vapor sampling probes and collection of soil vapor samples into Summa canisters for subsequent analysis) identified low concentrations of VOCs including benzene and other fuel-related compounds that exceeded conservative, risk- based screening criteria. Stantec concluded that soil vapor data did not suggest the presence of significant onsite source(s) of VOCs in soil vapor; observed concentrations likely represented ambient conditions attributable to multiple documented sources of petroleum hydrocarbon impacts to groundwater and the cumulative effects of over 100 years of industrial use at the site and surrounding areas; and soil vapor conditions can likely be managed effectively during future redevelopment via typical vapor mitigation techniques (i.e. vapor barrier systems). 3.4 HISTORICAL SOIL EXCAVATION AND DISPOSITION OF SOIL STOCKPILES The Phase I ESA references several episodes of soil removal at the site related to remediation and redevelopment of the adjacent Promenade property. Additional details regarding these operations are provided below. 3.4.1 2008 Soil Stockpile - Promenade and South Pointe Properties In September 2008, approximately 3,400 cubic yards (cy) of material were generated during grading operations associated with the Promenade redevelopment. Contractors removed soil from a 100-foot-wide perimeter of the Promenade property and adjoining South Pointe property (the site) in preparation for landscaping associated with construction of the Promenade.This excavation area is illustrated on Figure 3. The 3,400 cy of material were stockpiled in the central area of the South Pointe site. As documented in "Power Pile" Disposal and Confirmation Sampling, Stockton Promenade and Portions of the Southpointe Property (WKA, 2009), the stockpile was subsequently subdivided into 14 cells and sampled for COCs. One portion of the stockpile (cell 7) contained toxaphene at a concentration exceeding the Total Threshold Limit Concentration of 5.0 mg/kg. Based on subsequent solubility testing, the soil qualified as Class I non-RCRA hazardous waste. This material, equating to approximately 340 cy, was subsequently removed and disposed of at Chemical Waste Management's facility in Kettleman Hills, California. Following removal of the soil, the area beneath the cell 7 soils was sampled at a depth of 1 to 6 inches below grade, and all samples tested non-detect for toxaphene. The remaining approximately 3,000 cy of material generated during this effort remains at the site and is evident by the elevated topography in the central portion of the property, the elevation of which lies 2 to 5 feet above street grade. The extent of the soil stockpile is illustrated on Figure 3, which includes a topographic overlay. 3.4.2 Removal of 500 Cubic Yards of Promenade Soil In May 2011, WKA prepared the document entitled Work Plan for Removal of Stockpiled Soil and Offsite Disposal (WKA, 201 1) which proposed the removal of approximately 500 cy of soil that 3.3