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t CaliforniSegional Water Quality Cot*ol Board <br /> L\j Central Valley Region <br /> r Karl E. Longley,ScD,P.E.,Chair <br /> Linda S.Adams Arnold <br /> Secreraryfor Sacramento Main Office Schwarzenegger <br /> Environmental 11020 Sun Center Drive#200,Rancho Cordova,California 956706114 Governor <br /> Protection Phone(916)464-3291 •FAX(916)4644645 <br /> hUp:H/ .waterbOuds.ca.gov/centralvalley <br /> TO: Antonia K. J. Vorster FROM: Kathleen Amaru <br /> Site Cleanup Unit Engineering Geologist <br /> Program Manager Site Cleanup Unit <br /> SIGNATURE: <br /> Cori Condon <br /> Senior Engineering Geologist <br /> DATE: 30 April 2008 Site Cleanup Unit <br /> SIGNATURE: <br /> SUBJECT: RATIONALE FOR CONSIDERING NO FURTHER ACTION, MCMULLIN <br /> DEHYDRATOR STATION NATURAL GAS PROCESSING FACILITY, PACIFIC <br /> GAS AND ELECTRIC COMPANY, MANTECA, SAN JOAQUIN COUNTY <br /> Rationale: Soil impacted by petroleum hydrocarbons has been excavated. The maximum <br /> remaining concentration of gasoline (TPH-g) in soil is 20 mg/kg, and maximum remaining <br /> concentration of diesel (TPH-d) is 7.7 mg/kg. During the last four sampling events, <br /> groundwater was non-detect for all of the constituents of concern with the exception of <br /> diesel (TPH-d) impacts in well PZ-3 which fluctuated between 140 and 58 ug/L. The water <br /> quality objective for taste and odor for diesel is 100 ug/L. These contaminant <br /> concentrations are limited to well PZ-3. <br /> Issues: Soil and grab groundwater samples taken as part of a Preliminary Environmental <br /> Assessment (PEA) conducted in April 1997 revealed that soil and groundwater were polluted <br /> with benzene, toluene, ethylbenzene and xylene (BTEX) and total petroleum hydrocarbons <br /> in the gasoline (TPHg), diesel (TPHd) and kerosene ranges. Grab groundwater samples <br /> collected from the source area contained 80 ug/L benzene, 890ug/L ethylbenzene, 240 ug/L <br /> xylenes, 6,000ug/I TPH-d, 180,000 ug/L kerosene and up to 5,000 ug/L TPH-g. Soil <br /> contained up to 1400 mg/kg diesel, 880 mg/kg gasoline and between 1-6 mg/kg BTEX <br /> constituents <br /> Setting: This site is the location of a former natural gas processing facility. The Site is located <br /> on Airport Way and Perrin Road, approximately two miles south of Manteca in San Joaquin <br /> County (see Attachments 1 and 2 for location map and site plan). As seen in photo 1, the <br /> Site now consists of a metering shed and above-ground piping, surrounded by a chain-link <br /> fence. The nearest wells include a dairy production well located 200 feet to the east and <br /> two domestic water wells located with 0.5 miles of the Site. <br /> California Environmental Protection Agency <br /> Q*Recycled Paper <br />