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S E C 0 R 2003 Feasibility Test Summary Report • September 18, 2003 Page 1 1.0 INTRODUCTION SECOR International Incorporated (SECOR), on behalf of Chevron Environmental Management Company (Chevron), has prepared this report to present results of feasibility testing at the former Chevron service station located at 139 South Center Street in Stockton, California. The activities ' described in this report were performed in accordance with SECOR's Work Plan for Feasibility Testing/Corrective Action Plan Preparation (Work Plan), dated June 1, 2001, and two subsequent addendums to the Work Plan, dated November 28, 2001 and January 4, 2002, respectively. The Work Plan and subsequent addendums were approved by the San Joaquin County Environmental Health ' Division (SJCEHD) as indicated in the letters dated June 11, 2001 and January 15, 2002. Copies of the approval letters are included in Appendix A. ' 2.0 SITE DESCRIPTION The subject site is a former Chevron branded service station located at 139 South Center Street in Stockton, California (Figure 1). The station was demolished in early 2003. Former station facilities ' included two pump islands under a common canopy, four double-walled, fiberglass underground storage tanks (USTs), and a station building. Locations of former station facilities are shown on Figure 2. ' The area surrounding the site consists of primarily commercial land uses. Topography in the area of the site is relatively flat, and is approximately 12 feet above mean sea level (msl). The nearest surface water bodies are the Mormon Slough located approximately 114-mile south of the site, the Yacht Harbor located . approximately 114-mile north of the site, and the Port of Stockton located approximately one mile west of ' the site. 3.0 FEASIBILITY TESTING ' From October 29, 2001 through December 20, 2003, SECOR performed testing of several remedial alternatives in order to assess their feasibility for mitigating petroleum hydrocarbon impacts to soil and groundwater beneath the site. Feasibility testing included the performance of aquifer testing, a two-phase ' extraction (TPE) test, and an ozone sparge (OS) test. This section details these activities and their results. ' 3.1 Aquifer Testing In order to assess aquifer properties beneath the site, slug tests and a pumping test were performed. The purpose of these tests was to evaluate hydrogeologic conditions beneath the site and to determine whether groundwater extraction is a feasible alternative for remediation of dissolved hydrocarbons in groundwater beneath the site. 3.1.1 Slug Test On October 29 and 30, 2001, slug injection and removal tests were performed on wells MW-3, MW-9, and ' MW-12. The tests were performed by inserting or removing a PVC slug in the well. The hydraulic response was measured, using a pressure transducer with a built-in data logger (TROLL), until the groundwater elevation equilibrated to static conditions or until sufficient data was collected for analysis. Copies of slug test data sheets are included in Appendix B.