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Former Thrifty Co.Station No.172 Workplan for Additional Soil and Groundwater Assessment May 8,2017 In February 2012, Cardno ATC (now ATC Group Services) supervised the advancement of soil boring SB-1 and the installation of monitoring wells MW-17 and MW-19 through MW-22 and temporary soil vapor probes SV-1 through SV-5. Soil and groundwater samples collected from wells MW-17, MW-19, and MW-20 did not contain detectable concentrations of petroleum hydrocarbons. Soil and groundwater samples collected from wells MW-21 and MW-22 contained elevated concentrations of petroleum hydrocarbons. Additionally, soil gas samples collected from temporary soil vapor probes SV-3 and SV-4 contained concentrations of benzene that exceeded environmental screening levels (ESLs). Results of the well installation activities and soil vapor sampling are documented in Cardno ATC's Additional Site Assessment Report, dated July 30, 2013. On October 15 and 16, 2014, Cardno ATC supervised the installation of three soil vapor wells (SVE-1 through SVE-3) and one air sparge well (AS-1) at the site. The work was performed in accordance with Cardno ATC's Workplan For An Air Sparge/Vapor Extraction Pilot Test, dated July 11, 2014. On January 5 through 7, 2015, Cardno ATC conducted the pilot test described in the above workplan. The results of the sampling conducted during the well installation and the results of the pilot test will be submitted under separate cover. On January 13, 2015 Cardno ATC supervised the installation of monitoring well MW-23 into the deep water bearing zone to 60 feet bgs. No hydrocarbons were detected in soil samples collected. The work was performed in accordance with Cardno ATC's Workplan For Additional Soil And Groundwater Assessment, dated August 12, 2014. 2.2 Site Remediation On September 14, 1995, on behalf of Thrifty, Alton Geoscience (Alton) performed a soil vapor extraction (SVE) test at the site to assess the possibility of using this technology for soil remediation. Results of the test indicated an effective radius of influence of approximately 33 ft with a flow rate of approximately 16.8 standard cubic feet per minute (scfm) and a pressure drawdown of approximately 0.10 inches of water (H2O); therefore, SVE was identified as a feasible remediation option for the mitigation of hydrocarbon affected soil in the vadose zone beneath this site. In March 1999, a 12-hour groundwater extraction test was performed by Park on monitoring well MW-11 at a maximum sustainable flow rate of 4-gallons per minute (gpm) to evaluate the site for potential groundwater extraction remediation as required by the SJCEHD. A groundwater capture zone for the extraction well was estimated at approximately 110 ft. Based on the data collected during the pump test and the previous vapor extraction test, groundwater pump and treat and SVE technologies were capable of removing high concentrations of hydrocarbons from soil and groundwater beneath the site. A soil vapor and groundwater extraction and treatment system was started on April 26, 2001. The remediation system was connected to soil vapor extraction wells VW-1, VW-2 (A,B), VW-3, VW-4 (A,B,C), VW-5 (A,B,C), and VW-6 (A,B,C). The system operated until November 2007, when it was shut down for the fourth quarter sampling activities and kept off for the 2008 UST removal and well destruction activities. The system conveyance lines were reconnected and the system was restarted in April 2008. GHC upgraded the soil vapor and groundwater treatment system in September 2008. The system pad was expanded to include a 350-gallon 4