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David Wang, P.E. , Chief <br /> Page 7 <br /> March 6, 1991 <br /> Recommendation: The available data along with the additional <br /> work that has been proposed in the RI Report be submitted upon <br /> availability. The Department reserves the right to recommend <br /> additional work based on the results of the available data. <br /> SPECIFIC COMMENTS <br /> A. Chapter 4, RI Field Investigation <br /> 1. Page 4-10, Table 4 .2-1, Summary of Well Data at DDRW <br /> Sharpe <br /> Based on tabulated values for ground and top of casing <br /> elevations, most wells were located to the nearest one- <br /> tenth of a foot vertically. <br /> Recommendations: To accurately determine ground water <br /> flow directions, top of casing elevations should be <br /> determined to +0. 01 foot at a permanent mark on the rim <br /> of 'the casing. The wells should be resurveyed to ±0 . 01 <br /> foot vertically. If Table 4 . 2-1 is incorrect, it should <br /> be corrected. <br /> 2 . Page 4-20, Paragraph 4 <br /> The report states "The average water-level reading in <br /> 514A appeared to be higher than it should because it did <br /> not show the same downward trend in water-level elevation <br /> as nearby wells. " <br /> Recommendation: The report should clarify how an average <br /> water level value can be expected to show a downward <br /> trend. <br /> 3 . Page 4-21, Paragraph 2 <br /> The report states "The plume extents determined from <br /> these recent data were compared to previous plume maps <br /> based on earlier data. " <br /> Recommendation: The older TCE concentration contour maps <br /> should be presented to illustrate the stability and/or <br /> control of the plumes. <br /> 4 . Page 4-23 , Plume 1 <br /> The report states "Contaminant concentrations in almost <br /> all wells in this plume are generally trending lower due <br /> to the operation of the South Balloon Area Groundwater <br /> Treatment System. " <br />