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Mr. James Brathovde <br /> February 28, 1997 <br /> Page 2 <br /> W. Rempel,!nay not be aware that in addition to the upgradient wells, <br /> there are nine drinki4g water wells located downgradieit from the Site within 8000 <br /> feet radius with the closest being within 2800 feet. Gro undwater is the sole source <br /> for drinking water supply in the City. The average groundwater table in the City is <br /> 55 feet bgs. The 1,2-DCA detected at the site is of serious concern because it may <br /> pose threats-to the Gjty's downgradient drinking water,.wells. <br /> Based on the on-site hydrogeology, the nature of 1,2-DCA, and the <br /> groundwater flow directions,DTSC believes that the 1,.2-DCA may have migrated <br /> off-site and into the deeper aquifer. To protect the City's downgradient drinking <br /> water wells, efforts to monitor the horizontal and vertical movement of 1,2-DCA <br /> and other VOCs in shallow and deeper aquifers have been initiated. Upon <br /> executing a plume containment and remediation agreement with the City, <br /> additional groundwiter sampling at downgradient locations will be conducted to <br /> determine the horizontal and vertical extent of the 1,2-UCS:and other VOCs <br /> found at the Site. Capon determining the 1,2-DCA and;'other VOCs pose threats <br /> to the City's downgradient drinking water wells, work to contain and-remediate <br /> the contamination will be inifiatedimm <br /> 2. Page 2. Conclusions. The first paragraph the distance to nearest <br /> water supply well(2000 feet upgradient). <br /> Comment: <br /> The distance of 2000 feet to:the ndlitgt upgradient well is inaccurate. The <br /> nearest water supply well, CW#3R, is located.less thai)'-600 feet upgradient. The <br /> nearest downgradi4t well, CW#6, is located within 28b0 feet southeast from the <br /> Site. <br /> 3. Recommendation. The second paragraph. "While these wells may provide <br /> supplementA spatial geocheImc al data regarding the distribution of <br /> concentratiAs=in the:dry cleaner solvents plume, no data or technical <br /> analyses have been provided to indicate that any of these sampling points <br /> are,parti6l4ily relevant(let alone critical)for that purpose. ..., <br /> a <br />