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Evaluation of Potential Impacts <br />From The Proposed Nix Property Sand and Gravel Operation <br />On Shallow Groundwater Levels, Water Wells and Wetlands <br />considered the post-mining groundwater surface, upgradient of the pit, to be best represented by <br />the Theis non-equilibrium equations. Input values used for determining the drawdown (s) at a <br />given distance (r) from a pumping well (i.e., the gravel pit) include a pumping rate (Q), <br />transmissivity (T), time (t) and a specific yield (Sy). Aquifer properties of 200,000 gpd/ft and 0.2 <br />were used for transmissivity and specific yield, respectively. <br />Using a spreadsheet, an iterative process was used to assign a pumping rate (Q) that would create <br />a drawdown equivalent to the maximum elevation difference (described previously using <br />September 14, 2001 data) at the upgradient side of the mining azeas neazest the upgradient <br />wetland and wells after a period of 365 days (t). Using this assumed pumping rate and a period <br />of one yeaz, WWE calculated the drawdown effect (i.e., the difference between the pre-mining <br />groundwater surface and the post-mining groundwater surface) at various upgradient distances. <br />Table 4 is the spreadsheet used to evaluate potential reductions in groundwater levels ai various <br />distances from Mine Areas 1, 2, 3 and 6. <br />Using information developed in Table 4, it can be demonstrated that the greatest potential <br />reduction in groundwater level resulting from wet mining the Nix property is to the wells located <br />closest to the excavated pits. <br />In a fashion similar to that developed in Table 4, WWE completed an evaluation of anticipated <br />post-mining groundwater level changes at each well identified in Table 2. Table 5 has been <br />prepared to identify the nearest pit location to each of the wells, the maximum post-mining <br />elevation difference at the upgradient end of the pit due to lake leveling and the resulting <br />anticipated decrease in post-mining groundwater level at each well location based on September <br />14, 2001 conditions. In all cases, drawdown effects on wells greater than 600 feet from the <br />respective pits aze estimated to be less than 1 foot. Evaluation of the available saturated <br />thickness at the wells identified in Table 5 indicates that additional drawdown effects of less than <br />1 foot will reduce their available saturated thickness by no more than approximately 5 percent. <br />' s = Q W(u) where u = rZS <br />4rrT 4Ti <br />011-074.000 Wright Water Engineers, inc. Page 10 <br />April 2002 <br />