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r California R-aional Water Quality Contr^11 Board � Central Valley Region Karl E. Longley, ScD, P.E.,Chair Linda S.Adams Arnold 11020 Sun Center Drive tt200.Rancho Cordova.California 91670-6 1 1 4 Secreiun'jor Schwarzenegger Phone(916)464-3291 •FAX(916)464-4645 kin n�onmen m! Governor Prorecrrat httpl/ww" xNaterboards-ca.gov/centralvalleN TO: Jim Munch FROM: Jim Barton Senior Water Resources Control Engineering Geologist Engineer Underground Storage Tanks Enforcement Unit II DATE: 3 December 2008 SIGNATURE: SUBJECT: CLOSURE MEMO, TONY GONZALES TRUCKING, 1855 JACKSON AVENUE, ESCALON, SAN JOAQUIN COUNTY (CASE #390220) Background The subject site (Site) was a small trucking company which operated out of the backyard and a garage at a residence in Escalon (enclosed Figure 1). On 31 March 1988, one 10,000-gallon and one 500-gallon diesel, and one 1,000-gallon gasoline underground storage tanks (USTs) were removed from the Site. The San Joaquin County Environmental Health Department (SJCEHD) observed evidence of a release of petroleum hydrocarbons to soil beneath the gasoline UST. The maximum soil confirmation results were reported as total petroleum hydrocarbons as diesel (TPHd), 3,100 milligrams per kilogram (mg/kg); toluene, 49 mg/kg; xylenes, 390 mg/kg; and lead, 51.5 mg/kg. An additional soil sample result from beneath the 500-gallon diesel tank reported TPHd, 66 mg/kg. In a letter dated 7 March 1994, the SJCEHD directed the Site owners to conduct corrective action for the USTs release. By SJCEHD letter dated 27 November 1996, the Site was placed in the Local Oversight Program. On 18 January 2000, the State Water Resources Control Board UST Cleanup Fund (CUF) approved the Site claim and issued a letter of commitment. However, all work stopped at the Site and, on 22 March 2000, the CUF sent a 90-day letter for non-compliance with SJCEHD directives. On 1 August 2000 the SJCEHD referred the case to the Regional Board for enforcement action. The Regional Board Executive Officer issued a 13267 Order on 28 August 2000, requiring a workplan to investigate the unauthorized release. On 10 October 2000, Regional Board staff conditionally approved the submitted workplan. In November 2000, four soil borings (SB-1 through SB-4) were advanced (enclosed Figure 2) and grab groundwater samples were collected from two borings (SB-1 and SB-4). The 16 February 2001 Subsurface Investigation Report identified petroleum hydrocarbons in soil under the 1,000-gallon gasoline UST (SB-1) and near the 10,000-gallon diesel UST (SB-3) at depths ranging from 15' to 40' below ground surface (bgs). A cross-sectional representation of the soil lithology and contamination (enclosed Figure 3) show the known distribution of the soil contamination. Maximum soil boring concentrations were TPHd, 630 mg/kg; TPHg, 31,000 mg/kg; benzene, 70 mg/kg; toluene, 900 mg/kg; ethylbenzene, 800 mg/kg; xylenes, 3,800 mg/kg; and lead, 38 mg/kg. Analysis of two grab groundwater samples taken at first water, 60' bgs, reported total lead at 120 micrograms California Environmental Protection Agency �a�Rerveled Purer