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s <br /> California Rional Water Quality fontrol Board <br /> Central Valley Region s <br /> Peter M.Rooney Sacramento Main Office Ed I Schnabel <br /> Secretaryfor Internet Address: http://www.swrcb.ca.gov/—rwgcb5/home.httnl Chair <br /> Errvironmental 3443 Routier Road,Suite A,Sacramento,California 95827-3403 <br /> Protection Phone(916)255-3000•FAX(916)255-3015 <br /> '.j' <br /> TO: Gordon L. Boggs. FROM: Mark R. List <br /> UST Program Manager ; Engineering Geologist <br /> DATE: 4 September 1998 SIGNATURE: <br /> SUBJECT: FILE REVIEW FOR CLOSURE CONCURRENCE, MOORS PETROLEUM, , <br /> FRANK'S EXXON#4, 14800 W. FRONTAGE ROAD (MWY. 99), MANTECA, <br /> JOACO QUINCUNTY--t <br /> At the request of the San Joaquin County Environmental Health Division(SJCEHD), a file review was <br /> completed to determine if Regional Board staff agree with the SJCEHD determination of no further <br /> action required at this site. This information was obtained during my review of the Regional Board <br /> casefile, and following discussions with APEX Envirotech, Inc. (APEX), the consultant for the site. <br /> Background: <br /> A detection of petroleum hydrocarbons in the soil adjacent to an underground storage tank prompted an' <br /> investigation of the lateral and vertical extent of contamination at the site. Four groundwater monitoring <br /> wells were installed in 1988 and 1989. In November 1989,three 10,000-gallon underground storage <br /> (regular,unleaded and diesel)tanks (USTs)were removed and contaminated soil was excavated to <br /> 17 feet below ground surface (bgs). All soil samples collected from the pit confirmed contamination. <br /> In November 1989 and June 1992, five additional monitoring wells were installed. Quarterly <br /> groundwater sampling of the monitoring wells conducted between April 1992 and January 1995 showed ! <br /> contamination consistently in MW-1 through MW74, occasionally in MW-5 through MW-8 and was not <br /> detected in MW-9. Remediation was initiated in October 1990, with the installation oofsoil venting. _ <br /> compoi eats iri&tank excavation:Soil vapor and groundwater extraction systems were operated from <br /> January 1995 to November 1996. During this time' these systems extracted 2391.8 lbs. of TPHg and <br /> 8.17 lbs. of benzene. <br /> Since the remediation system has been shut off, 1,2-DCA continues to remain above the MCL, and <br /> TPHd and MTBE remain above the taste and odorlthreshold. MTBE is also above the proposed State <br /> Action Level. , <br /> On 29 April 1998, we received a letter from the SJCEHD recommending "No Further Action Required" <br /> at the site. On 26 May 1998, Regional Board staff inember Ms. Patricia Anderson sent a letter to the <br /> SJCEHD, which proposed to delay the"No Further Action Required" decision until specific information <br /> was provided. <br /> .. �E� .. .3 y ..r - -♦ p -.. <br /> • i <br /> ' I <br /> California Environmental Protection Agency <br /> Recycled Paper 1' <br /> I <br />