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Mr. Tom Scnreiner, Division of Minerals and Geology April 15, 2005 Page 2 ~~ CIVIL RES"JU RCES,LLC must have begun prior to beginning mining the third phase. Therefore, the contra(put on the area being mined will limit the area effectively being dewatered to approximately 50 to 60 acres maximum, similar to completed groundwater modeling. A pumping rate was not estimated for the site dewatering. The proposed dewatering or GW phase was set to a constant head elevation equal to the top of bedrock ("dry" condition) and allowed to equilibrate. This is more conservative than inserting wells with pumping rates. The length of time that the pit is dewatered in each phase is immaterial because the model was allowed to equilibrate to steady state (which is conservative). In other words, it doesn't matter how long the pit is dewatered in each phase because our model estimates an infinite time period (which is conservative). The modeling completed in support of the Groundwater Report considered the maximum extent of drawdown without mitigation measures and then inserted mitigation measures to limit the area of impact. The mitigation measures included in the model include four sites where 500 gallons per minute (gpm) will be recharged to the aquifer for a total of 2,000 gpm. These recharge areas will be installed in advance of the mining activity in each area. The recharge areas to be installed with each phase are summarized below: Active Mining Area Active Recharge Area(st North Silt Pond North, North-Center Pond t North, North-Center, South-Center Pond 2 South-Center, South South Silt Pond South Additional mitigation measures will include recharge on the Yokooji and Wiant silt ponds, however, we conservatively ignored the benefits that are expected from this activity. Due to the modeled decreases the applicant has proposed mitigation measures to help alleviate the reduction in the groundwater table as a result of mining. To date, five more monitoring wells have been installed and will be used to help monitor groundwater levels to the north, south and east and will be used to determine the appropriate time that a mitigation measure should be implemented. Comment 4: Pumping Rate - to conformance with Rule 6.4.4 and Rule 3.1.6(1), please describe the maximum pumping rate necessary tocompletely de-water the maximum disturbed area ... Response 4: As indicated in Response 3 above, the modeling conservatively assumed constant head nodes in the mining area (which implies 100 percent drawdown to bedrock level), and therefore no matter how high the pumping rates, there would be no negative affect on the modeled results. Comment 5: The applicant has stated that wetlands offsite will not be adversely affected ... Response 5: Walsh Environmental Scientists and Engineers is currently working with the US Anny Corp of Engineers to have this area classified as non-jurisdictional wetlands. Comparison of ground surface crontours provided on plan mapping and observed groundwater and river elevations in the area indicate that the existing water table is over 4 feet from the ground surface in this area. Further, this area will be used for storing overburden and therefore will be filled to the height of the surrounding topography. If the USACE