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Soil Vapor Extraction & In-Situ Air Sparging Pilot Test Work Plan MCBILLIN REAL ESTATE INVESTMENT 2154 South El Dorado Street, Stockton, California 1.0. INTRODUCTION Advanced GeoEnvironmental, Inc (AGE) has prepared this work plan for performance of a soil vapor extraction (SVE)/in-situ air sparge (IAS) feasibility pilot study at 2154 South El Dorado Street, Stockton, California (site). The scope of work includes installation of three (3) SVE and two (2) IAS wells, performance of an 8-hour SVE/IAS pilot test, and preparation of a report of findings with recommendations. The location of the site is illustrated on Figure 1. A plan of the site is illustrated on Figure 2. In a Corrective Action Plan, dated 16 April 2018, AGE made recommendations for a field scale pilot test to evaluate feasibility of SVE and IAS at the site. On 20 April 2018, the California Regional Water Quality Control Board - Central Valley Region (RWQCB) approved AGE's recommendation for an SVE/IAS pilot test and directed by letter that a work plan for an SVE/IAS pilot test be submitted to the SJCEHD for review (Appendix A). The purpose of this work plan is to detail the installation of three SVE wells, two IAS wells and performance of an SVE/IAS pilot test at the site. This work plan has been prepared in accordance with guidelines issued by the (RWQCB) for investigation of underground storage tank (UST) sites. A summary of previous investigations at the site was included in the AGE-prepared Corrective Action Plan discussed above. Based on groundwater monitoring data collected at the site between August 2013 and April 2018, the average depth to groundwater is approximately 23 feet bsg. For modeling purposes, soil samples collected at depths less than 25 feet bsg are considered to be representative of the site's vadose zone conditions. Analytical results of soil samples collected in the vadose zone are summarized in Table 1. Analytical results of groundwater monitoring well samples and monitoring well construction details are summarized in Tables 2 and 3, respectively. The plan view of the lateral extent of vadose zone and saturated zone petroleum hydrocarbon-impact to soil is depicted in Figures 3 and 4, respectively. The estimated extent of petroleum hydrocarbon-impact to soil is depicted in cross sectional views A-A', B-B' and C-C' (Figures 5,6 and 7, respectively). The estimated extend of petroleum hydrocarbon-impact to groundwater is depicted in Figure 8. 2.0. SCOPE OF WORK Significant gasoline-impacted soil extends vertically beneath the former UST areas to depths of at least 45 feet bsg, and has spread laterally towards the northeast at least 175 feet (Figures 3 and 4). Therefore, to evaluate the feasibility of SVE in the vadose zone,