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%,/ ✓ <br /> JJW GEOSC/ENCES Inc. <br /> Envirarrmant&1 Consults"& <br /> Be"91neering Contractor <br /> FACSIMILE TRANSMITTAL MEMO <br /> To: Pieter Crosby Page 1 of 2 <br /> P.C. Toxic, Inc. March 29, 1999 <br /> Fax: (208)748.5437 <br /> From; Dan Dottai <br /> Subject: JC Trucking <br /> Per our c iscussion earlier today, the following information may help justify the cost for conductor <br /> casing in tallation to the UST Cleanup Fund. Generally, our costs to install the two deeper wells <br /> has doub led with the addition of conductor casings. <br /> As you 2 re aware, San Joaquin County wants two wells installed within the second (deeper) <br /> aquifer, ' one is encountered within 70 feet below ground surface (bgs)_ They want the wells <br /> installed hin and directly through the areas of highest detected contamination_ Our preliminary <br /> findings iuggest that the contamination is quite significant. Further, it is possible that free <br /> product r tight exist. <br /> If a sego d aquifer truly exists, then it is imperative that any well installed into the second aquifer <br /> be const=ted with a conductor casing. This is necessary, as it is generally impossible to <br /> adequatf ly seal the upper aquifer from the deeper aquifer by means of only a downhole seal. <br /> Given th known high concentrations of contamination at this site, this becomes particularly <br /> important <br /> Our wo will corsntficrm <br /> onsist of drilling a pilot hole. The pilot hole will serve two purposes. First, the <br /> pilot hole will whether a second (deeper) aquifer exists. If we do not encounter a second <br /> aquifer b F our target depth (apparently 70 feet bgs in this case), then the installation of conductor <br /> casings i All not be necessary. Should this be the case, we will notify San Joaquin County, and <br /> re-evalu a the meed for the deeper wells. <br /> Should second aquifer be encountered, then the pilot hole will give us a handle on the <br /> thickness of the aquitard which separates the two aquifers. The aquitard thickness is required in <br /> order for is to know the optimum depth for founding the conductor casing. <br /> The pilot hole will be drilled outside of the known upper aquifer contaminant plume. It will be <br /> continuously coned from approximately 40 to 70 feet bgs. Once completed, a groundwater grab <br /> sample will be collected from the pilot hole (if a deeper aquifer is encountered), and the pilot hole <br /> will be im ediatety grouted. It is important that the pilot hole be immediately grouted as it will be <br /> a temporary Conduit Connecting the two aquifers during the short time that it remains open. This <br /> is why it Beds to be drilled outside of the upper aquifer contaminant plume_ <br /> 11350 Monier Park Place, Rancho Cordova, CA 95742 Tel: 916.853.8025 Fax: 916.853.8029 <br />