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California " -%gional Water Quality Clorol Board <br /> Central Valley Region a <br /> Katherine Hart, Chair <br /> Linda S.Adams Edmund G. Brown Jr. <br /> Acting Secretary for 11020 Sun Center Drive#200, Rancho Cordova,California 95670-6114 Governor <br /> Environmental Phone(916)464-3291 •FAX(916)464-4645 <br /> Protection http://www.waterboards.ca.gov/centralval ley <br /> TO: File: Chapin Brothers, Inc. FROM: Jim Barton <br /> 1766 Monte Diablo Avenue Engineering Geologist <br /> Stockton, San Joaquin Co. UST Unit 2 <br /> DATE: 5 January 2011 SIGNATURE: <br /> i <br /> SUBJECT: UST CASE CLOSURE, CHAPIN BROTHERS INC., 1766 MONTE DIABLO <br /> AVENUE, STOCKTON, SAN JOAQUIN COUNTY, CASE NO. 390577 <br /> Site Background <br /> Chapin Brothers Inc. (Site) is currently an auto repair shop located on the southeast corner of <br /> Buena Vista Avenue and Monte Diablo Avenue, at 1766 Monte Diablo Avenue in Stockton, <br /> San Joaquin County (Figure 1). The neighborhood is mixed residential and commercial, with <br /> an elementary school located on the northwest corner of Buena Vista Avenue and <br /> Monte Diablo Avenue. A former Shell owned station operated at the Site from the 1930's to <br /> 1985. Chapin Brothers Inc. leased and later subleased the Shell station from 1941 until <br /> purchasing the property in 1985. The Site operated as a Shell-branded service station until <br /> December 1990, when a leak in the underground storage tank (UST) system was indicated by <br /> groundwater monitoring, and the service station closed. The USTs were tested and reported <br /> tight in January 1990. <br /> On 5 December 1990, one groundwater monitoring well (MW-1) was installed in the northeast <br /> corner of the Site, north of the USTs. Based upon sample results the San Joaquin County <br /> Environmental Health Department (SJCEHD) issued an Unauthorized Release Form on <br /> 5 March 1991. Maximum 1990 and final 2010 groundwater monitoring concentrations are <br /> listed below in Table 1. <br /> Table 1 Groundwater Monitoring Results' <br /> Date TPHg benzene toluene eth (benzene xylenes MTBE TAME DIPE <br /> 12/7/1990 200,000 31,000 11,000 1,900 5,200 NA NA NA <br /> 7/20/2010 4,000 2,000 15 160 462 4.4 43 65 <br /> 1 =concentrations given in micrograms per Liter(ug/L) TPHg=total petroleum hydrocarbons as gasoline MTBE =methyl tert butyl ether <br /> TAME=tertiary amyl methyl ether DIPE=di isopropyl ether NA=not analyzed until November 1997 <br /> In August 1993, one 550-gallon waste oil, and two 4,000-gallon and two 8,000-gallon gasoline <br /> USTs (installed in 1975) USTs were removed from the Site. Three additional, older <br /> 1,000-gallon gasoline USTs, located west of the 1975 USTs, appeared to be previously sand <br /> filled and abandoned in place, and were also removed at that time. Approximately 150 yd of <br /> the excavated soil was transported offsite to a private property owned by Chapin Brothers Inc. <br /> California Environmental Protection Agency <br /> CYecycled Paper <br />