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Non-Tributary Support: Cash Mine Borehole AdrianBrown <br />for approximately 3 months with the current pump, and the water production in the year in which the <br />mine dewatering took place would be 16.4 acre feet (13.9 acre feet to dewater the mine plus 2.5 acre feet <br />inflow during the year). <br />2.8 Use <br />Currently the water produced by mine dewatering is not used. The water is pumped to the currently <br />unused lined tailings pond on the property from which it evaporates. <br />When operation of the mine mill restarts, which is expected in. early 2007, the dewatering water <br />produced after that time will be used for milling operations at the mine. Some of the water may be <br />returned to the mine void with mine backfill, although this technology has not yet been demonstrated to <br />be effective in this mining environment. <br />3. DETERMINATION OF NON-TRIBUTARY WATER <br />3:1 Basis <br />Section 37-90-103(10.5) C.R.S. defines non-tributary ground water in material part as: <br />(10.5) "Nontributary ground water" means that groundwater, located outside the boundaries of any <br />designated ground water basins in existence on January 1, 1985, the withdrawal of which will not, <br />within one hundred years, deplete the flow of a natural stream, including a natural stream as defined in <br />sections 37-82-101 (2) and 37-92-102 (1) (b), at an annual rate greater than one-tenth of one percent of <br />the annual rate of withdrawal. " . <br />3.2 Impact to Natural Streams <br />The impact to the natural streams in the vicinity of the mine is assessed by well hydraulics. The <br />extraction of water from the mine affects the surrounding rock aquifer by creating drawdown which <br />increased over time, and decreases with distance from the mine.. <br />The flow impact occurs to Mill Run. This is the only stream with any generally sustained flow in it in <br />the vicinity of the mine, and is at the base .of the slope on which the mine is located. <br />The flow impact to Mill Run resulting from the dewatering of the mine, sustained for 100 years, is <br />computed as follows: <br />1. The flow domain is divided up into six sectors, each subtending lengths of the stream at different <br />distances from the mine. These sectors are shown in Plate 5. <br />2. The flow withdrawn from (or denied to) each sector by the. dewatering flow from the mine is <br />computed by use of the Glover equation for the stream depletion per unit length of the stream <br />(Glover, 1974, Equation 9-2)21: <br />20 Glover, R.E., 1974. Transient Ground Water Hydraulics. Monograph CEP73-74REG6S, Department of Civil Engineering, College of <br />Engineering, Colorado State University, Fort Collins, Colorado, January 1974. <br />1601A-20070125 9