SITE INFORMATION AND CORRESPONDENCE

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�. Super Center Mart 17 March 2016J 701 East Charter WayC_ip Stockton, San Joaquin County -JiR0NMEHTAL r-ALTH DEPARTA4PNT hydrocarbons were not detected beneath the 1,000-gallon UST. Site assessment began in June 1997. 3. A dual phase extraction (DPE) system operated at the Site from 24 January 2011 to 29 January 2014. The DPE system removed an estimated 5,587 pounds (894 gallons) of vapor phase gasoline (TPH-G). Approximately 3,010,490 gallons of groundwater was extracted and treated by the DPE system, removing approximately 408 pounds (68 gallons) of dissolved phase TPH-G. The estimated radius of influence of the DPE system was an approximately 119 foot capture zone for groundwater, while the soil vapor extraction component had an approximately 23 feet radius of influence. Concentrations in influent groundwater decreased from a maximum of 96,000 ug/L to 9,400 ug/L TPH-G, 5,300 ug/L to 550 ug/L benzene, and 270 ug/L to <0.50 ug/L MTBE during operation of the DPE system. Influent vapor concentrations decreased from 1,488 parts per million by volume (ppmv) to 34 ppmv for TPH-G, from a maximum of 66 ppmv to 8.7 ppmv for benzene, and from a maximum of 12 ppmv to <0.5 ppmv for MTBE. At the time of shut-down, the DPE system's influent vapor extraction rate had decreased from 66 pounds per day (ppd) per day to less than 2 ppd. DPE system operational data is presented in Attachment A. 4. The Site meets the general criteria of the State Water Resources Control Board's (State Water Board's) Low-Threat Underground Storage Tank Case Closure Policy (LTCP) as follows: • The site is within the service area of a public water system. The site is within the service area of the California Water Service. • The release consists only of petroleum. • The release has been stopped. The USTs were removed in February 1998. • Free product has been removed to the maximum extent practicable. Free product has never been observed. • A Site Conceptual Model has been developed. Submission of multiple reports has resulted in generation of a conceptual site model. Petroleum hydrocarbons were detected to the maximum depth explored of 150 feet bgs. The lateral extent of groundwater impacts in the shallow zone is less than 100 feet. • The secondary source has been removed to the extent practicable by DPE. At the time of shut-down, the DPE system's influent extraction rate had decreased from 66 ppd to less than 2 ppd, and concentrations of petroleum hydrocarbons in extracted groundwater had decreased by an order of magnitude.