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k <br /> 5TATE OF COLORADO <br /> DIVISION OF MINERALS AND GEOLOGY <br /> Department of Natural Resources <br /> 1313 Sherman St., Room 215 <br /> Denver,Colorado 80203 <br /> Phone:(303)866-3567 <br /> FAX (303)832-8106 <br /> DEPARTMENT OF <br /> NATURAL <br /> RESOURCES <br /> Roy Romer <br /> Governor <br /> DATE: April 4, 1996 <br /> James S Lochhead <br /> Executive Director <br /> TO: Dave Holm Michael B Long <br /> Division Director <br /> FROM: Allen Sorenson <br /> RE: Mine Pool Equilibrium, sunnyside Mine, Sunnyside Gold <br /> Corporation, MLRB Permit No. M-77-378, CDPS Permit No. CO-27529 <br /> It is a binding component of Sunnyside Gold Corporation's (SGC) <br /> reclamation permit that the rate of rise of the mine pool be tracked by <br /> reading pressure gauges at the American Tunnel and Terry Tunnel bulkheads. <br /> Mine flooding will be considered complete at the point in time when ground <br /> water inflows to the mine workings equilibrate with ground water outflows <br /> from the mine workings, i.e. , when the elevation of the top of the mine <br /> pool stabilizes. The point in time at which equilibrium occurs has a <br /> bearing on a number of requirements both in the reclamation permit and in <br /> the SGC/WQCD settlement agreement. <br /> The Division of Minerals and Geology (DMG) and SGC have agreed that the <br /> equilibrium point will be determined from mathematical relationships <br /> developed to the mutual satisfaction of both DMG and SGC (see enclosed <br /> letter dated 10/27/93) . The premise upon which the determination of <br /> equilibrium will be made has been established, however the specifics of <br /> the determination can only be anticipated until such time that data on the <br /> rate of rise of the mine pool are available. An example of an equilibrium <br /> determination is provided here: <br /> A best fit curve is applied to the scatter of data on the mine pool <br /> elevation against time from the point when the American Tunnel valve is <br /> closed. The curve, for the purposes of this example, takes the form <br /> f(x) = 1/ (x-a)2 <br /> where: x is mine pool elevation, <br /> y is time, and, <br /> a is the presumed equilibrium elevation. <br />