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[~ <br />Although the initial hydraulic head employed in the model is somewhat lower than the <br />expected equilibrium water level, the estimated drawdown and recovery rates would <br />not be significantly affected by the difference. In spite of the simplifying <br />assumptions, the model is useful for obtaining a rough approximation of the flooding <br />schedule. <br />The American Tunnel began draining the Sunnyside Mine in early 1961 (approximately <br />33 years prior to estimated bulkhead construction). During modeling the mine was <br />allowed to dewater the surrounding fractured rocks for a modeled time interval of 33 <br />years via a drain at the American Tunnel Level. The drain in the model was calibrated <br />so that the average discharge from the drain was 899 gpm (compared to a present <br />discharge of approximately 930 gpm). The model predicted head after 33 years of <br />draining also corresponds well to the observed heads near the 0700 and 1500 <br />runarounds (Section 5.3). After the 33 years of dewatering the drain was "plugged" <br />to simulate bulkhead construction. The model-estimated rate of mine flooding is <br />shown on Figure 9. The mine is modeled as being 86% filled with water in 10 years. <br />Reasonable estimates of hydraulic parameters were employed in the model. If the <br />actual average porosity is greater than the modeled value (0.01) the mine will refill <br />somewhat more slowly than modeled. If the actual average hydraulic conductivity is <br />less than the modeled hydraulic conductivity (0.15 ft/day) then the mine will also refill <br />somewhat more slowly than modeled. These effects should be more than offset by <br />sunny\wp\traci1225 i IMar 1993. Rpt <br />37 <br />N.`6 SIRIO~ HYDRO-SEARCH <br />