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r- <br /> L ARCADIS Ms..Lori Duncan <br /> January 5, 2010 <br /> at 12.47. ARCADIS believes the well is still viable for::groundwater sampling of the <br /> 115 foot water bearing zone with an approximate 6.5 foot screen interval,installed.in <br /> the sand unit.underlying the site. In addition, the elevated pH.measurements in <br /> r MW.-6D will not negatively affect future groundwater samples analyzed for the <br /> following list.of analytes: <br /> • Total petroleum hydrocarbons in the gasoline range [TPH-GRO (C6-C1o)1 <br /> total petroleum hydrocarbons in the diesel range [TPH-DRO (C,o-C28)1,total <br /> petroleum hydrocarbons as motor oil (TPH-MO) [C16-C3d, and methanol by. <br /> United States Environmental Protection Agency(USEPA)Method 80156 <br /> •. Benzene, toluene, ethylbenzene, .arid: total xylenes (BTEX) by :USEPA <br /> r Method-82606 <br /> 6•� Methyl tertiary butyl ether (MTBE), ethanol, dHsopropyl ether (DIPS), ethyl <br /> tertiary.butyl ether (ETBE), tertiary amyl methyl:ether (TAME), tertiary butyl <br /> alcohol (TBA), 1,2-dichloroethane(1,2-DCA) and ethylene dibromide (EDB), <br /> also known as 1,2-dibromoethane,and ethanol by USEPA Method 8260B <br /> It is unlikely that hydrolysis due to the pH will have significant effect on observed <br /> concentrations. The elevated pH may bias the concentrations slightly higher by <br /> increasing effective solubility;however, since this well is located near the <br /> L� downgradient edge of the.plume away from any source mass,we dobot expect <br /> significant high concentration bias. <br /> Groundwater samples were collected on November 17; 2.009 and.submitted to <br /> Lancaster Laboratories under chain of.custody docurrientation.(Attachment 2). <br /> Concentrations appear to be consistent with what would-be expected for the <br /> downgradient wells. <br /> Detailed'boring logs with well construction details for MW-6.and MW-6D are included <br /> in Attachment 3. Further well installation details will be reported under separate <br /> cover. <br /> If the SJCEHD approves, ARCADIS will add the installed wells to the groundwater <br /> and monitoring<program on a semiannual monitoring and sampling basis beginning <br /> With the first quarter of 2010. <br /> L <br /> L <br /> Page: <br /> 1\CA5FPOataWWcq c EMACHEVROM70907512 C==Ncafiw ConeWder kCmspondance Regulalog4We0 Install Lellet1309075 Deep Weft Install Approval Request4261010950.doc 2/3 <br />