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General Order R5-2015-0012-044 - 2 - 26 July 2018 The Transmission Store San Joaquin County Project Description: Previous use of a UST at the Site resulted in petroleum hydrocarbon impact to soil and groundwater. The primary constituents of concern include total petroleum hydrocarbons as gasoline, benzene, toluene, ethylbenzene, and total xylenes (BTEX), and methyl tert butyl ether (MTBE). The Site is currently used as an automotive repair facility by Lucky Auto Repair and Tire. AGE operated a soil vapor extraction (SVE) system at the Site from 2000 to 2004, removing 3,248.9 pounds of hydrocarbons. Additionally, the AGE operated an SVE and air sparge (AS) system at the Site between 2011 and 2013, with the AS portion of the system continuing to run to the present, though the effects have been limited as compared to those observed between 2000 and 2004. In a 14 March 2014 letter, Central Valley Water Board staff requested that AGE optimize the existing remedial system, and potentially propose an additional remedial technology. Having determined that the existing system had been optimized to its fullest potential, AGE proposed an in-situ chemical oxidation (ISCO) pilot test in a work plan and several addendums between May 2014 and January 2015, as noted below. Central Valley Water Board staff approved the scope of work in a letter dated 23 February 2015. For this project, AGE submitted the following documents: In-Situ Chemical Oxidation Pilot Test Work Plan (Work Plan), dated 28 May 2014 In-Situ Chemical Oxidation Pilot Test Work Plan — Addendum (Addendum), dated 12 December 2014 In-Situ Chemical Oxidation Pilot Test Work Plan — Addendum Response (Addendum Response), dated 22 January 2015 Background groundwater analytical data from wells MW-2 and MW-3 submitted by email 22 April 2015 ISCO Pilot Test Remediation Well Installation Report (Installation Report), dated 9 November 2015 Background groundwater analytical data from wells MW-2 and MW-3 submitted by email 22 April 2015 Notice of Intent and Monitoring and Reporting Plan (N01), dated 19 February 2015 o Central Valley Water Board believes the 2015 date is an error as the document was received on 22 February 2016. AGE installed injection well ISCO-1 on 12 June 2015 which will be used for the injection of a 5% hydrogen peroxide (H202) solution into the shallow aquifer. For the purpose of the pilot test, AGE will complete a single 200-gallon injection event, witn an average injection rate of 1.5 gallons per minute (gpm) and a maximum rate of 5 gpm. For full-scale remediation, injection will occur in batches of approximately 200 gallons, at the same average and maximum injection rates used during the pilot test, with a maximum total monthly injection volume of 800 gallons. AGE calculated the maximum injection volume using recent groundwater and soil analytical data for the site, and the calculated injection area, groundwater plume mass, and total organic carbon mass. Based on a proposed pilot test injection of 200 gallons of H202 solution, calculations indicate that there is 1:2.4 Stoichiometric ratio between the available 02 injected and the mass of TPHg to be remediated and the organic carbon load in site soil. However, AGE's calculations indicate that approximately seven to eight times more 02 will be needed to completely remediate the entirety of the petroleum hydrocarbon impact at the site while it competes with the organic carbon load. Base on positive pilot test results, this would require a minimum of six to seven 200-gallon injection events.