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California F-;ional Water Qualifyontrol Board <br /> • Central Valley Region 1. <br /> Peter M.Rooney Sacramento Main Office -€ <br /> rna Ed'J.Schnabel <br /> Secretaryfor Inteet Address: http://www.swreb.ca.gov/—rwgcb5/hdme.hrml �rf �' ;' Chair r <br /> Environmental 3443 Routier Road,Suite A,Sacramento,California 95827-3003 1 <br /> Protection Phone(916)255-3000•FAX(916)255-3015' <br /> rp- <br /> TO: Gordon L.Boggs FROM: Mark R. List <br /> UST Program Manager . . -Engineering Geologist � <br /> DATE: l October 1998 Y 51GNATURE �' I r <br /> 4, <br /> SUBJECT: FILE REVIEW FOR CLOSURE CONCURRENCE, FORMER TOWN& COUNTRY <br /> CHEVRON SITE, 13336 E. HIGHWAY 88, LOCKEFORD SAN JOAQUIN COUNTY 1 <br /> -A ,. —. r.�,` •4=".p ,� =i ifs �... .y4 � -. �'; <br /> In response to the 29 December 1997 letter from San Joaquin County Environmental Health Division <br /> (SJCEHD), a file review was completed to determine if Regional Board staff agree with the SJCEHD Y <br /> determination of"No Further Action Required," (NFAR), at this sit"e'. In a letter dated 13 February 1998, <br /> Regional Board staff member Ms. Patricia Anderson, did not concur,`with the SJCEHD NFAR decision, <br /> and requested that the lateral and vertical extent of contamination be'determined, and that soil samples } <br /> be collected to determine the potential for leaching of contaminants into`groundwater. Additionally, <br /> Ms. Anderson directed that a water sample be collected to deterinin"Ie if site activities have impacted <br /> groundwater. Following the completion of the requested work, I have evaluated the results of recent site <br /> activities, as presented in the 13 July 1998 report, "Excavation for'One Soil Boring," submitted `x <br /> GeoSoly, LLC, and the historic site information in the casefileA The`following is the result of my 4 <br /> evaluation of this site. <br /> Background: ,^ <br /> In July 1991, one 10,000-gallon gasoline (regular) underground storage tank (UST), one 550-gallon <br /> waste oil UST, and two (a 5,000 and a 7,000-gallon) unleaded gasoline USTs were removed from the <br /> site. Approximately 400 feet of product piping was also removed _,The three gasoline USTs were �€ <br /> located in a.common tank..pit and the waste oil UST"was located in"a separate tank prt�Soi1 <br /> discoloration and petroleum odors were noted beneath tliegasolineErand waste oil'tanks. No <br /> discoloration or petroleum odors were noted below the product piping, and soil samples collected below <br /> the piping did not contain elevated concentrations of petroleum contaminants. However,'the'soil ` <br /> samples collected from,the UST excavations did contain significant petroleum contamination. <br /> Contaminated soil was excavated from portions of the former gasoline and waste oil tank locations.. <br /> In August 1991, soil samples were collected at.7.5 feet below ground surface (bgs) from the waste oil <br /> x. <br /> tank excavation, and at 13 to 14 feet bgs in the gasoline tank excavastion. Both pits were backfilled to ' " <br /> surface grade with pea gravel, and the contaminated.soil stockpile was sampled and disposed of off-site. <br /> The former gasoline tank pit was not covered with asphalt, allowing rain water to infiltrate and <br /> potentially allowing leaching of the remaining soil contamination into groundwater. <br /> In August 1997, one soil boring was advanced to 17 feet bgs near the former waste oil tank location, and <br /> five soil borings were advanced to between 26,and 30 feet bgs in the area of'the gasoline tank' <br /> excavation. The analytical results of soil samples collected fromtwo"of the borings revealed elevated <br /> California Environmental Protection`Agency. <br /> ��Recycled Paper <br />