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Emma, which formerly would have been leaking to the ground-water system through low <br /> permeability lacustrine clays. <br /> 4.1.6 Discharge from the Ground-Water System <br /> The discharge from the groundwater flow system may be temporarily enhanced by the presence <br /> of the Sunnyside Mine. As discussed in section 3.1.7 the base flow of Eureka Creek below the <br /> Terry Tunnel is now somewhat greater than 170,000 gpd. The base flow of the North Fork of <br /> Cement Creek above Gladstone is approximately 230,000 gpd. However, at Gladstone the <br /> American Tunnel discharges a Mow of approximately 3,100,000 gpd (based on an October 1991 <br /> measurement). Most of the flow from the American Tunnel originates as ground water from <br /> permeable fractures. The Sunnyside Mine has removed ground water from storage and induced <br /> an irregular cone of depression in the potentiometric surface. When recharge to the fractures <br /> equals discharge from the frac ures an equilibrium will exist in which no more water will be <br /> removed from storage. Amer�can Tunnel flows mentioned in letters from D. Hutchinson to <br /> Messrs. McCormick and Hurstl in 1961 are greater (up to 2,500 gpm) than the flow measured <br /> by SJCMV in October, 1991 (2,160 gpm), but it is likely that the system is now nearly at <br /> equilibrium. If the drainage of these fractures has not yet reached equilibrium, then discharge <br /> from the ground-water flow system has been temporarily enhanced. <br /> As discussed in section 3.1.7 th , discharge of springs and seeps in the Cement Creek watershed <br /> may have decreased due to de watering of the Sunnyside Mine. However, the base flow of <br /> sanjuan\sunny\110361\oct91.Rpt 34 <br /> esg snon !HYDX0=8ERRCH <br />