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