SITE INFORMATION AND CORRESPONDENCE_FILE 2

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RECEIVE® JIMCO TRUCK PLAZA— REQUEST FOR PUBLIC COMMENTS FACT SHEET MAR 09 2012 The Jimco Truck Plaza is located at 1022 Frontage Road in Ripon, California. The 7!R% a truck service facility with a convenience store, restaurant, laundry facility, officeHEAlTF1warehouse that contains a truck wash and truck service bay. Other site structures �ES dispensers, one split 8,000-gallon and 12,000-gallon gasoline underground storage tank (UST), a diesel pump station, four 30,000-gallon diesel aboveground storage tanks (ASTs), a propane tank, and a truck scale. In 1998, three gasoline and diesel USTs and associated piping and dispensers were removed from the site. Evidence of a petroleum hydrocarbon releases from the UST system was discovered. A total of approximately 1,180 tons (600 cubic yards) of hydrocarbon-impacted soil was excavated and transported offsite for landfill disposal. In 2004, a 1,000-gallon waste oil UST was removed from the site. In 2005, a small diesel release occurred from the underground diesel piping near the diesel pump station/ASTs. From 1999 through 2010, a series of subsurface investigations were conducted consisting of 43 borings and 21 wells to delineate the full extent of hydrocarbons in soil and groundwater. In the vicinity of the former USTs, soil is impacted by gasoline and diesel range hydrocarbons at the groundwater table, primarily between 20 and 25 ft below grade surface (bgs). Low levels of total petroleum hydrocarbon as gasoline (TPHg) and as diesel (TPHd) are present in groundwater near the former USTs. During the August 2011 groundwater sampling event, TPHg concentrations ranged from 93 to 190 µg/L and TPHd concentrations ranged from 61 to 220 µg/L. Benzene was detected in only one well at a concentration of 0.69 tag/L and MTBE concentrations ranged from 1.0 to 46 µg/L. The TPHg, TPHd, benzene and MTBE plumes are of limited extent and do not extend offsite. In the vicinity of the diesel pump station/ASTs, soil is impacted by diesel-range hydrocarbons primarily between 15 to 20 ft bgs. Low levels of TPHd are present in groundwater near the diesel pump station/ASTs. During the August 2011 groundwater sampling event, TPHd concentrations ranged from 54 to 210 µg/L. The TPHd plume is of limited extent and does not extend offsite. A sensitive receptor survey identified one municipal supply well and three commercial/domestic supply wells within a 2,000 ft radius of the site. Municipal Supply Well #12 is located approximately 750 feet (ft) west of the site and is screened from 165 to 190 ft bgs, with additional screened intervals below this depth. The well completion report indicates a conductor casing and seal from 0 to 150 ft bgs. A commercial supply well (DW-1) is located onsite next to truck wash and is screened from 160 to 200 ft bgs. No hydrocarbon concentrations have been detected in DW-1 since sampling was initiated in 1998. Another supply well is located 175 ft southeast of the site on the Ripon Farm Service property and is screened from 176 to 196 ft bgs with a surface seal to 50 ft bgs. A domestic well is located at 23066 South Highway 99 and is screened from 180 to 200 ft bgs with a surface seal to 110 ft bgs. Based on the deep well screen intervals, well construction, and intervening distance from the site, potential impact to the four identified wells is very unlikely. The closest surface water body to the site is the Stanislaus River located approximately 9,000 ft south of the site. Based on the limited extent of onsite hydrocarbon plumes and intervening distance to the Stanislaus River, environmental impact to this sensitive receptor is very unlikely. The Jimco Truck Plaza case is under consideration for a low risk site closure by the Central Valley Regional Water Quality Control Board. Information for the site or public comments can be submitted to Mr. James Barton by email at (ibarton(a�waterboards.ca.gov), by phone at 916-464- 4615, or by mail to Central Valley Regional Water Quality Control Board (CVRWQCB) at 11020 Sun Center Drive, #200, Rancho Cordova, California 95670. Written comments must be submitted to the CVRWQCB no later than April 10, 2012.