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Mr. Tom Schreiner, Division of Minerals and Geology `~ <br />Apri115,2005 <br />Paget ~ CIVIL RES'~U RCES,LLC <br />must have begun prior to beginning mining the third phase. Therefore, the control put on <br />the area being mined will limit the area effectively being dewatered to approximately 50 to <br />60 acres maximum, similar to completed groundwater modeling. <br />A pumping rate was not estimated for the site dewatering. The proposed dewatering or <br />GW phase was set to a constant head elevation equal to the top of bedrock ("dry" <br />condition) and allowed to equilibrate. This is more conservative than inserting wells with <br />pumping rates. The length of time that the pit is dewatered in each phase is immaterial <br />because the model was allowed to equilibrate to steady state (which is conservative). In <br />other words, it doesn't matter how long the pit is dewatered in each phase because our <br />model estimates an infinite time period (which is conservative). <br />The modeling completed in support of the Groundwater Report considered the maximum <br />extent of drawdown without mitigation measures and then inserted mitigation measures to <br />limit the area of impact. The mitigation measures included in the model include four sites <br />where 500 gallons per minute (gpm) will be recharged to the aquifer for a total of 2,000 <br />gpm. These recharge areas will be installed in advance of the mining activity in each <br />area. The recharge areas to be installed with each phase are summarized below: <br />Active Mining Area Active Recharge Area(s) <br />North Silt Pond North, North-Center <br />Pond 1 North, North-Center, South-Center <br />Pond 2 South-Center, South <br />South Silt Pond South <br />Additional mitigation measures will include recharge on the Yokooji and Wiant silt ponds, <br />however, we.conservatively ignored the benefits that are expected from this activity. Due <br />to the modeled decreases the applicant has proposed mitigation measures to help <br />alleviate the reduction in the groundwater table as a result of mining. To date, five more <br />monitoring wells have been installed and will be used to help monitor groundwater levels <br />to the north, south and east and will be used to determine the appropriate time that a <br />mitigation measure should be implemented. <br />Comment 4: Pumping Rate - to conformance wdh Rule 6.4.4 and Rule 3.1.6(1), please describe the <br />maximum pumping rate necessary to completely de-water the maximum disturbed area .. <br />Response 4: As indicated in Response 3 above, the modeling conservatively assumed constant head <br />nodes in the mining area (which implies 100 peroent drawdown to bedrock level), and <br />therefore no matter how high the pumpirig rates, there would be no negative affect on the <br />modeled results. <br />Comment 5: The applicant has stated that wetlands offsite will not be adversely affected ... . <br />Response 5: Walsh Environmental Scientists and Engineers is curently working with the US Army <br />Corp of Engineers to have this area classified as non-jurisdictional wetlands. Comparison <br />of ground surface contours provided on plan mapping and observed groundwater and <br />river elevations in the area indicate that the existing water table is over 4 feet from the <br />ground surface in this area. Further, this area will be used for storing overburden and <br />therefore will be filled to the height of the surrounding topography, If the USACE <br />