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1 <br />very low hydraulic conductivity for lined ponds. The high hydraulic conductivity values result in <br />' zones of "flat" water levels, the elevation of which is controlled by the water level in thy: aquifer, as <br />is the case in an unlined pond in connection with the ground water system. Lined ponds were <br />' modeled as zones of very low hydraulic conductivity, which effectively simulates a no-flow <br />boundary in the aquifer in the vicinity of the lined pond. Specific model inputs, inclLding stream <br />' and general head conductance values and hydraulic conductivity values, aze summazi:~ed in Table <br />2. <br />The bottom of the alluvial aquifer (top of bedrock) was included as a model input based on mapping <br />' provided by WMI, as shown in Appendix K. The hydraulic conductivity throughout the model was <br />based on aquifer chazacteristics determined from pumping test data, as previously discussed. With <br />' the exception of the azea near the upper reach of the model domain and modeled po:lds, a single <br />hydraulic conductivity value was blanketed across the model. A greater value of hydraulic <br />' conductivity was input for the upper reach of the model where the aquifer widens below the narrow <br />outlet of the stream channel where it flows out of the `'hogback". <br />' Water levels in the alluvial aquifer were modeled based on a map of water levels prepared by RMC. <br />Water level elevations were input using the general head and stream packages; the general <br />' configuration of the potentiometric surface throughout the aquifer was estimated basted on steady <br />state simulations. The various scenarios modeled included: calibration (1996), pre-mining, miniug, <br />' and post-mining. Each scenario was modeled by adding additional unlined and lined ponds in <br />accordance with the mining plan, as shown in Appendices L through O. Drains and constant head <br />' boundaries were also included in the mining and post-mining simulations to lower the water level <br />in the model and to simulate areas where the aquifer will be removed by mining. Water level <br />' changes at well locations were estimated based on the modeled water level differences between the <br />simulations. The water level changes at wells were classified into risk categories based on the water <br />' level changes at the well sites. <br />1 <br />' -14- <br />' 1 Ric/np-llrnl//.n .I~viriu/r. Ln. <br />