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_pg_ <br />Use of these stations allows determination of approximate inflows to <br />the North Fork of the Gunnison River contributed by the study watershed <br />boundary located on Figure 1. The average monthly flows are <br />illustrated on Table 2, along with the inflows to the North Fork of the <br />Gunnison River from Minnesota Creek. These figures were used to <br />determine the amount of outflow via the North Fork of the Gunnison <br />River from the basin. Obviously, such predictions are not absolutely <br />accurate. For example, less than 3 years of data existed for Minnesota <br />Creek and 1 year (1977) experienced drought conditions. However, for <br />purposes of this assessment, such figures provide a rough approximation <br />of flows through the general area. <br />PROBABLE HYDROLOGIC CONSEQUENCES <br />Ground Water <br />As the Mt. Gunnison No. 1 Mine begins operation, waters from the F <br />seam, saturated beds in the Barren Member immediately above the F-seam, <br />and some fractures will be intercepted and appear as mine inflows. As <br />mining in the F-seam expands, it is likely that continually greater <br />mine inflows will be encountered as the F-seam, Barren Member, and <br />fractures are dewatered. As larger blocks of the area influenced by <br />mining become dewatered, inflow into the mine will likely decline until <br />equilibrium is reestablished between the various components, including <br />mine inflow, aquifer recharged spring discharge. <br />To estimate mine inflows, exclusive of spurious inflows encountered in <br />fracture zones, the applicant assumed the mine to be a single well <br />source and applied the straight line solution technique of Jacob and <br />Lohman. Using this procedure, and assuming unconfined conditions in <br />the aquifer, the applicant determined the maximum inflow to the mine, <br />again excluding fracture flows, to be 45 gpm by year 5, with the <br />average inflow over the life of the mine to be 30 to 70 gpm. However, <br />in making this determination, it is not clear whether all restrictions <br />on use of the Jacob-Lohman equation were realized. This equation is an <br />approximation valid only when the variable of integration "u" is less <br />than .01. Insufficient data and explanation are given in the permit to <br />check these calculation. Furthermore, the transmissivity, "T" and <br />storativity, "S", values use in these calculations are questionable. <br />However, ongoing monitoring data collected at the mine to date, <br />supports the operator's predictions of inflows. <br />To estimate the extent of the cone of depression caused by mining, a <br />variation of Jacob's Modified Non-Equalibrium equation was utilized. <br />Using a transmissivity of 10 g/d/ft and a storage coefficient of .001 <br />(confined conditions), it was determined that the cone would expand 0.2 <br />miles in 1 year and 0.4 miles in 5 years. However, in conducting these <br />calculations, the basic assumption of Jacob's technique (that u = .O1) <br />has been violated. In both the first year and fifth year <br />determinations, the value of variable of integration "u" exceeds the <br />