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Ms. Cynthia Pazker <br />July 13, 2001 <br />Page 3 <br />Subsequent comments will be concerned with potential impacts to specific water <br />resources issues which you have identified. These are: <br />1. The possible impact of proposed mining operations on the wetland located directly <br />across WCR 28 on Sage Hill Farm. <br />2. The possible impact on your domestic water supply well. <br />3. The possible impact on your irrigation well. <br />4. The possible impact on your spring and the pond fed by it. <br />The most significant impacts on these resources are likely to be related to the aquifer <br />dewatering/drawdown proposed for the active operations period. We have therefore <br />carried out a preliminary analysis using a commonly employed procedure, as described <br />below. <br />Comments on local and practical considerations are provided at several points in the <br />discussion. <br />Analysis of Project Dewatering Impacts on Area Groundwater Levels <br />This analysis uses widely accepted theoretical formulations and principles requiring the <br />use of assumptions and simplifications The results provided here should be regarded as <br />indicative, and their application should incorporate professional judgement and <br />knowledge of local conditions. The approach and assumptions used in this analysis are <br />described below. <br />It would be reasonable to expect that the applicant to provide sufficient data, discussion <br />and analysis of relevant issues so that a satisfactory evaluation can be undertaken of the <br />matters discussed below. <br />Radial Approach -Modified Theis Nonequilibrium Equation <br />As groundwater is pumped from an aquifer, a cone of depression results which increases <br />in depth and extent over time. Drawdown at any point at a given time is directly <br />proportional to the pumping rate. Drawdown in response to well pumping can be <br />estimated using a mathematical procedure known as the Theis approach If aquifer <br />properties and the pumping rate are known, it is possible to predict drawdown in water <br />levels at any distance from a well and at any time after the start of pumping, assuming no <br />Hydrosphere Resource Consultants, 1002 Walnut Suite 200, Boulder, CO 80302 <br />