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0 0 <br /> First Quarter 1993 Monitoring Report -2- 3 August 1993 <br /> DDRW, Sharpe <br /> basis in MW-407A. This area of Plume 3 should be captured by the Central Area <br /> extraction system. If the increases in arsenic, bromacil or other pollutants, <br /> are related to the dry wells and storm water runoff, Sharpe will have to develop <br /> a plan to prevent this in the future. This may require different management of <br /> the storm water runoff and may require wellhead treatment as pretreatment for <br /> this extraction well . Dilution with other extracted water is not an acceptable <br /> solution to the problem. Ground water treatment is estimated to last <br /> approximately 40 years, however, if Sharpe continues to use dry wells for <br /> management of the storm water runoff this ground water problem will remain after <br /> the cleanup of the VOC contamination. The dry wells should be addressed as a <br /> solid waste management unit (SWMU) in the comprehensive feasibility study (FS) <br /> in order to address this issue. <br /> 3 . The Quarterly Report provides a discussion on the capture zone analysis that <br /> states that capture in the South and North Balloon Areas is nearly complete. <br /> The leading edge of the plume in the South Balloon Area is planned to be <br /> captured by the Central Area extraction system. Sharpe indicates that a new <br /> extraction well , NB-5, installed in the North Balloon in April 1993, will <br /> provide capture for the leading edge of the plume in that area. It is premature <br /> to conclude that plume capture is nearly complete. Until the Central Area <br /> extraction system is installed and we have quarterly reports indicating the <br /> performance of NB-5, we cannot concur that plume capture is nearly complete. <br /> Areas of concern for complete plume capture are in the area of MW-505B which is <br /> off-site and the area between Plumes 1 and 3. This latter area is of particular <br /> concern because unless the cones of depression from both the South Balloon and <br /> Central Area extraction systems overlap, we cannot be assured that there will be <br /> cleanup in this area because of the monitoring data gap in this area. <br /> There are two other items that were observed in this quarterly report: <br /> 1. 707 Roth Road continues to have a TCE concentration slightly over the Primary <br /> MCL. <br /> 2. The TCE concentration in MW-509C has dropped significantly from about 80 p g/1 <br /> to 13 ug/l . This drop in concentration appears to be due to the lack of <br /> pumpage from the off-site agricultural supply wells. <br />