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EPA Comments <br /> DDJC-Tracy Well Monitoring Program <br /> Quarterly Monitoring Report <br /> Fourth Quarter 2001 Sampling Round <br /> February 2002 <br /> SPECIFIC COMMENTS <br /> 1. Figures 2-2 and 2-3: Figures 2-2 and 2-3 appear to contain errors in how the <br /> groundwater contours are drawn to reflect all available data. For example, on Figure 2-2 <br /> EW033AU, 52.61 feet above mean sea level (msl), LM062AU, 56.03 feet msl, <br /> EW005AUA, 55.19 feet msl, and EW044AU, 55.41 feet msl, are all within in the 55 foot <br /> msl contour and should be within the 52 and 53 foot msl contours, 56 and 57 foot msl <br /> contours, 55 and 56 foot msl contours, and between the 55 and 56 foot msl contours, <br /> respectively. On Figure 2-3 LM077A, 51.49 feet msl, should be between the 51 and 52 <br /> foot msl contours, not between the 50 and 49 foot msl contours. Please correct and label <br /> the groundwater contours on the figures mentioned above so they accurately reflect the <br /> groundwater level in their respective horizons, or mark the wells as not being used to <br /> determine groundwater level contours. <br /> 2. Figure 2-3: On Figure 2-3 the overland flow area appears to be influencing groundwater <br /> flow in the Upper Horizon, but the data are subject to alternate interpretations. The 54 <br /> foot msl contour has been moved up almost 0.5 miles to well OW018A, which appears to <br /> exert a large degree of control on the contours in the central portion of the Tracy Annex. <br /> However; there is no control between wells OWOI8A and LM072A, and the well density <br /> is not sufficient to clearly establish any effect from the overland flow area on the Upper <br /> Horizon. The well density in this area is even less in the overlying Above Upper Horizon <br /> and the underlying Middle Horizon, making definitive interpretation even more difficult. <br /> Another possible interpretation of the data, which can be drawn using the current wells, is <br /> that there is a groundwater mound forming in the Upper Horizon beneath the overland <br /> flow area. Please consider the possibility of a groundwater mound beneath the overland <br /> flow area in future quarterly monitoring reports, or provide an explanation of why the <br /> available data do not support such an interpretation. <br /> 1 <br />