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DATA GAP ASSESSMENT WORK PLAN AND PATH TO CLOSURE REVIEW Chase Chevrolet, 424 N. Van Buren Street Background January 2, 2018 In February 1996, an in-situ air sparging (IAS) pilot test was performed at the site. An increase in induced pressure, organic vapors, groundwater elevation, and dissolved oxygen were generally measured at monitoring wells throughout the test. Procedures and results of this pilot testing were documented in AGE's December 1996 Corrective Action Plan. In June 1998, groundwater monitoring wells MW-19, MW-20, and MW-21 were installed with dual- completed casings near the former location of UST no. 8. Based on the groundwater sample collection dates, wells MW-22, MW-23, and MW-24 were installed in 2001 down gradient of the former 10,000 gallon UST at the site. In May 2001, a groundwater extraction feasibility test was performed at the site to obtain general groundwater aquifer characteristics and to evaluate aquifer response to groundwater extraction at a constant pumping rate. Results from the extraction feasibility test were documented in AGE's Groundwater Extraction Feasibility Test Report, dated December 10, 2001. Quarterly groundwater monitoring was performed at the site between January 1991 and October 2003. The most recently documented groundwater monitoring event was documented in AGE's Quarterly Report - Fourth Quarter 2003 dated April 2, 2004. This was the last groundwater monitoring event to occur before site wells were destroyed in 2004. Results from this monitoring event indicated concentrations of total petroleum hydrocarbons as gasoline (TPHg) and benzene that were in excess of established water quality objectives (WQ0s) of 5.0 and 1.0 micrograms per liter (pg/L), respectively. In April and May of 2004, Treadwell and Rollo (T&R) performed an excavation in the vicinity of former UST no. 7. Approximately 715 cubic yards of impacted soil were removed from the site and disposed of at Forward Landfill in Stockton. A summary of excavation activities was documented in T&R's Soil and Groundwater Remediation Report dated November 18, 2004. Historical soil boring logs and cross-sections (those located in the available historical record) are provided in Appendix B, historical tables summarizing soil and groundwater data collected from the site are included in Appendix C, and historical figures depicting former site features are included in Appendix D. Stantec bm \\us1312- f02 \ workgroup \ 1857 \active \ 185703766 \ 05_report_deliv \ deliverable \ work_plan \185703766_20180102_424_van_buren_work_plan_final.docx 2.3