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f <br /> page 2, 640 N. EI Dorado <br /> evaluate the potential of increasing the rate of recovery of the free product into the well by <br /> drawing down the water table to between 24 and 25 feet bsg. The performance of this <br /> test is approved, but care should be taken to avoid drawing free product down into <br /> unimpacted or slightly impacted soil. However, this addresses only one issue at the site. <br /> In addition to the free product in the source area, there is the soil contamination in the <br /> vadose zone, and the vertically and laterally undefined groundwater contamination. <br /> Feasibility studies for both of these issues will need to be addressed. <br /> In correspondence dated April 16, 2002 SJC/EHD approved the proposed installation of <br /> three wells for investigation of the lateral extent of the shallow contaminant plume. In the <br /> revised work plan Ground Zero changed the number to two wells. SJC/EHD does not <br /> approve this proposed change. All four monitoring wells onsite are impacted with volatile <br /> organic compounds. Two additional shallow wells would not be adequate to surround the <br /> known extent of the plume. As noted above, vertical assessment should precede <br /> additional lateral assessment; well designs may need modification before installation. <br /> Deep, discretely screened wells may also be required. <br /> If you have any questions or comments please call Lori Duncan at (209)468-0337. <br /> Donna Heran, REHS, Director <br /> Environmental Health Department <br /> C'M'" 6�C�,� -OO �e5 - <br /> Lori Duncan, Senior REHS Nuel C. Henderson, Jr., R.G. <br /> LOP/Site Mitigation Unit IV LOP/Site Mitigation Unit IV <br /> cc: Marty Hartzell, CVRWQCB <br /> John Lane, Ground Zero Analysis, Inc. <br />