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Ms. Cynthia Parker July 13, 2001 <br />Page 5 <br />Weld County Road 28 neaz the southern edge of the Nix property, and pumps at a <br />constant rate every day. The required pumping rate was estimated by solving the Theis <br />equation such that the drawdown along the southern edge of the mining pit was equal to <br />the planned depth of the mine (47 feet) within 3 yeazs of commencement of mine <br />operations, and that the dewatering activities would go on for 20 years, as indicated in the <br />application. <br />Results of the Theis analysis are shown in Figure 1, Figure 2 and Figure 3 (attached.) <br />The initial development and the ultimate consequences of 20 years of dewatering on the <br />groundwater levels are shown in the figures. To illustrate the sensitivity of this approach <br />to various assumptions, the analysis has been done for three transmissivity values - <br />72,300 gpd/ft (used in the application to the State Engineer for the Substitute Supply <br />Plan), 100,000 gpd/ft and 200,000 gpd/ft. <br />This analysis does not take into account several factors which may change or diminish <br />the water table drawdown and related impacts. Although we have not quantified them, <br />they should be considered .Examples of such factors include: <br />• The actual dewatering facilities maybe different than those assumed in this analysis. <br />As the application does not provide any description of dewatering facilities and <br />procedures, we have assumed a very basic arrangement for the purpose of this <br />evaluation. <br />• The disposal of pumped water from the mine dewatering facilities could be designed <br />to partially mitigate water table declines. The application does not indicate how (or <br />whether) this will be implemented. We have assumed that this water would be <br />directly discharged from the mine site to St. Vrain Creek. <br />• There will be considerable aquifer recharge in the azea of concern because of the <br />existing Last Chance Ditch carriage losses and imgation activities in the azea. <br />• Because the proposed mine is relatively close to St. Vrain Creek, there will be <br />considerable rechazge from the creek. This will, however, generally be on the other <br />side of the proposed mine from Sage Hill Farm. <br />• There aze withdrawals from and recharge to the aquifer from other sources, including <br />irrigation and domestic wells, and domestic water/wastewater supplied by pipeline <br />external sources. <br />Our analysis indicates that, if pumping /dewatering for mining operations takes place in <br />the manner assumed in the analysis, the following general impacts maybe anticipated for <br />water-related facilities on your property: <br />Hydrosphere Resource Consultants, 1002 Walnut Suite 200, Boulder, CO 80302 <br />