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0 <br />TETRA TECH RMC <br />Page 3 <br />Ms. Kate Pickford <br />March 20, 2003 <br />groundwater levels but the zone of influence is likely on the order of 250 to 1,000 <br />feet. In general, the impacts are relatively local dissipating to background <br />conditions in a distance of 250 to 400 feet. <br />During mining, the lowering of the water table can impact resources that obtain <br />water from the aquifer within the zone of influence. We anticipate that the only <br />area that may be impacted by draw down associated with Pod 1 is the adjacent <br />riparian corridor. If measurements at monitoring wells and piezometers indicate <br />that the ground water levels have been lowered 2' below seasonal background <br />conditions, Hall-Irwin will mitigate impacts through the use of corrective <br />measures. Corrective measures may include discharging dewatering water <br />through recharge trenches or pits, discharge to irrigation ditches or the river, or all <br />a combination of the above. <br />10. Based on the stability analysis, draw down will not impact the structural integrity <br />of the surrounding wells and surface water drainages for pod 1. The remaining <br />pods will have slurry walls and will not cause draw down. <br />11. Tetra Tech RMC has evaluated the flood plain issues and is in the process of <br />preparing a Weld County Flood Hazard Development Permit. We will forward a <br />copy of the Weld County permit once it has been obtained. Base flood elevations <br />in a vertical datum consistent with the topography, have been added to the <br />Existing Conditions Map. Our initial evaluation indicates that mining within Pod <br />1 will not increase erosion potential on adjacent properties. Prior to mining in <br />Pod 3 and later phases, we will submit a Technical Revision detailing our <br />analysis of erosion potential and appropriate mitigation measures for the <br />remainder of the property. <br />Rule 6.4.12 Exhibit L -Reclamation Costs <br />12. Please notify us after you have estimated the cost to reclaim the site. <br />13. We have updated the quantities and revised the reclamation costs by applying the <br />administration cost to the sum of the direct costs. <br />Rule 6.4.13 Exhibit M -Other Permits and Licenses <br />14. Hall-Irwin will notify the Division of changes made to the mining or reclamation <br />through submittal of an amendment or technical revision application if necessary. <br />Rule 6.4.16 Exhibit P -Municipalities Within Two Miles <br />15. Town of Johnstown Town of Milliken <br />P.O. Box 609 Drawer 290 <br />Johnstown, CO 80534 Milliken, CO 80543 <br />(970) 587-4664 (970) 587-4331 <br />