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California P egional Water Quality Vontrol Board N"1 Central Valley Region wu T Peter M.Rooney Sacramento Main Office Ed J.Schnabel Secretary for Internet Address: http://www.swrcb.ca.gov/--rwgcb5/home.htmi Chair Environmental 3443 Routier Road,Suite A,Sacramento,California 95827-3003 Protection Phone(916)255-3000•FAX(916)255-3015 TO: Gordon L. Boggs FROM: Mark R. List Engineering Geologist DATE: 6 August 1998 SIGNATURE: ' SUBJECT: REVIEW FOR NO FURTHER ACTION CONCURRENCE, STOCKTON DEVELOPMENTAL CENTER, SIO EAST MA_GN_ O_LL4 STREET,STOCKTON, SAN JOA QUIN COUNTY At the request of the San Joaquin County Environmental Health Department(SJCEHD), a file review was completed to determine if Board staff agree with the SJCEHD determination of no further action required at the above referenced site. The following information was obtained during my review of the Regional Board casefile and the SJCEHD casefile for the Stockton Developmental Center site. Background: Prior to 1991, eight underground storage tanks were located on the Stockton Developmental Center Property, and were used for the boiler plant operations. Five of the tanks, each 10,000-gallons, contained diesel fuel. The three remaining tanks,two 10,000-gallon, and one 8,500-gallon, contained fuel oil. The two 10,000 gallon fuel oil tanks were removed on 23 September 1991, with no indication of odor or staining. Confirmation soil samples indicated 1.2 and 1.4 parts-per-million(ppm) TPHd. SJCEHD did not require any further evaluation at the former location of these tanks. The 8,500 gallon fuel oil tank was investigated on several occasions. Soil samples collected in the vicinity of this tank contained elevated concentrations of TPHd and fuel oil to approximately 15 feet below ground surface (bgs). The soil sample results from soil borings in the vicinity of the 8,500-gallon fuel oil tank are as follows: Contaminant: Concentration: Sample Depth/Location: TPHd 6,900 ppm(mg/Kg) 15' bgs/below tank TPH Bunker Oil 9,600 ppm(mg/Kg) 15' bgs/below tank The concentration of TPHd and TPH Bunker Oil were not detected above the laboratory reporting limits at 20 feet bgs. Clay is indicated as the predominant soil type at 20 feet bgs. SJCEHD approved closure in place for the 8,500-gallon fuel oil tank. On 24 January 1997,the UST was closed in-place by filling the tank and associated piping with a cement slurry mix. Approximately 100 - 150 cubic yards of petroleum impacted soil is believed to be left in place below the closed in-place UST. California Environmental Protection Agency C4 Recycled Paper