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California RrIonal Water Quality F'iontrol Board <br /> Central Valley Region <br /> Peter M Rooney Sacramento Main Office Ed J,Schnabel <br /> 1aryf- Intemet Address http//www swrcb ca gov/—rwgeb5/home html Chan <br /> - <br /> r <br /> 3443 Routier Road,Sete A,Sacramento,Caltfomia 95827-3063 <br />' rotechon Phonc(916)255-3000-FAX(916)255-3015 <br />' TO: Gordon L Boggs FROM Mark R Last <br /> UST Program Manager Engineering Geologist <br /> DATE, 4 September 1998 SIGNATURE 14, - <br /> SUBJECT: FILE REVIEW FOR CLOSURE CONCURRENCE,MOORS PETROLEUM, <br /> FRANK'S EXXON#4, 148110 W. FRONTAGE ROAD (HWY. 99), MANTECA, <br /> ' SAN JOAQUIN COUNTY <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 undergr6und 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 /> 1 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 MW-4,occasionally in MW-5 through MW-8 and was not <br /> detected in MW-9 Remediation was initiated m October 1990,with the installation of soil venting <br /> components in the tank excavation Soil vapor and groundwater extraction systems were operated from <br /> ' January 1995 to November 1996 During this time, these systems extracted 23918 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 odor threshold 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 member Ms Patncia 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 /> 1 <br /> t California Environmental Protection Agency <br /> @�Keeycled Paper <br />