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4 <br /> Additional Site Assessment Report and Corrective Action Work Plan 6 <br /> The Southland C lon Store#20632 4627 DaVinct Drive Stoeidon CA January 8 1997 <br /> 7 3 ORC Installation <br /> Following removal of the USTs and subsequent excavation at the site, a thin layer of Oxygen Release <br /> Compound (ORC) in powder form wil[ be placed on the groundwater in the resultant excavation pit The <br /> ORC will increase oxygen supply to the subsurface and enhance natural degradation of the residual <br /> dissolved BTEX, MTBE, and TPH-G Approximately 150 pounds of ORC will be placed in the excavation <br /> over a surface area of approximately 480 square feet Attachment 5 contains ORC Technical Bulletin#5- <br /> 6 0 which discusses the remedial effectiveness of ORC with BTEX and MTBE compounds <br /> 7.4 Off-Site Well Search <br /> Fluor Daniel GTI will conduct a well survey to identify any water producing wells within a 2,000 foot radius of <br /> the site Information will be reviewed at the Department of Water Resources(DWR)in Sacramento, CA <br /> 7.5 Report Preparation <br /> A letter report will be submitted upon completion of the tank removal and field activities described above <br /> The report will document the methods and results of the work completed The report will be reviewed and <br /> signed by a California registered geologist <br />• 8.0 CLOSURE ABSTRACT <br /> Following the excavation of hydrocarbon-Impacted soils and placement of ORC in the backfill material, <br /> Fluor Daniel GTI, on behalf of the Southland Corporation,will propose no further action at the site for the <br /> following reasons- <br /> 1 )The source, USTs and fuel dispenser island,will have been upgraded in compliance with current <br /> UST regulations and no longer represent a continued source of hydrocarbons <br /> 2)The excavation of the soil underlying the fuel dispensers and surrounding the USTs will effectively <br /> remove the soil source of the dissolved hydrocarbon plume <br /> 3)The addition of ORC to the subsurface will enhance the natural biodegradation of residual dissolved <br /> hydrocarbons near the former source area The remaining dissolved BTEX,MTBE,TPH-G will <br /> naturally attenuate with time <br /> 4) If no water supply wells are found to be In hydraulic conductivity with the monitoring wells at the site <br /> from the off-site well search,the site will be proposed for closure as low risk to utilized groundwater <br /> sources <br /> FLUOR DANIEL GTI <br /> 2DO32at rpt <br />