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Former Thrifty Co.Station No. 172 Workplan for Additional Soil and Groundwater Assessment May 8,2017 batch tank, a bag filter, a 1 HP transfer pump, four 1,000-pound granular activated carbon liquid phase vessels, and a groundwater extraction system control panel. The upgraded system was designed to extract vapor from wells VW-1, VW-3, VW-4, VW-5, and VW-6, and extract groundwater from wells MW-11 R and MW-12R. The system was restarted in December 2008. The vapor extraction system was shut down on March 19, 2009 for repairs. As of March 19, 2009, it was estimated that 210,156 pounds of hydrocarbons had been removed by the soil vapor extraction (SVE) unit. The groundwater extraction system was anticipated to be started during the first quarter 2009; however, the system remained shut down due to the system air compressor being stolen from the site. To date, 582,804 gallons of groundwater have been treated and discharged. In July 2007, GHC performed an ozone sparging bench scale test. Results indicated the site petroleum hydrocarbons in soil and groundwater were successfully destroyed with ozone treatment. Ozone sparging, however, generated concentrations of chromium VI and bromate that exceeded the California maximum contaminant levels (MCLs) for these compounds. Based on the results, ozone sparging was determined to not be a feasible method of groundwater treatment (GHC, 2008b). In July 2010, Stantec performed a 5-day SVE system shake down and radius of influence test. Results indicated there was no longer a need for vapor extraction at the site related to vadose zone treatment. Stantec subsequently submitted an Interim Remediation Action Plan, dated August 27 2010, that was approved by the SJCEHD on September 2, 2010. The IRAP proposed to run the groundwater extraction system on MW-11 R until site demolition activities began at the site. However, due to an accelerated redevelopment schedule, interim remediation was postponed in preparation for the site demolition. The remediation system has been removed and stored off-site, and the conveyance piping has been cut at the well boxes in preparation for redevelopment activities. Site redevelopment activities have since been completed; no remedial equipment is currently present at the site. In ATC's Site Conceptual Model and Human Health Risk Assessment, dated September 30, 2011, ATC recommended the completion of additional soil and groundwater delineation and soil vapor sampling activities be performed at the site prior to proposing any additional remedial activities. The additional site assessment activities were performed during first quarter 2012; and a report documenting the findings was submitted in July 2013. On January 14, 2014, Cardno ATC submitted a Corrective Action Plan and recommended a remediation strategy consisting of a combination of air sparging and soil vapor extraction. Cardno ATC submitted Air Sparge/Soil Vapor Extraction Pilot Test Work Plan dated July 7, 2014, and implemented the work in the first quarter 2015. The pilot testing indicated that vapor extraction and air sparging were viable methods for remediating impacted soil and groundwater at the site. Results were summarized in Cardno ATC's Pilot Test Summary Report dated August 4, 2015. 2.3 Sensitive Receptors In November 1992, SSB Environmental Consultants, Inc. (SSB) performed a well survey within a '/2-mile radius of the site. Results indicated that the City of Stockton well No. 11 was located at the corner of Inglewood and Leslie Avenues approximately 2,100 ft southeast of the site. In addition, a number of private wells were identified approximately 1,000 ft west of the site in a 5