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Division of Minerals and Geology 9 November 2000 Page 2 Exhibit G -Water Information Section 8.02 -Surface Water System 1. Reference to the flood boundary was incorrectly stated as appearing on Exhibit C (Pre- mising Plan) map. The flood boundary is depicted on the air photomap designated as Exhibit G (Water Information Map). Additional flood boundary information, as well as responses to technical adequacy items 2a and 2b under this section, are being sent under separate cover from Pickett Engineering, Inc. Section 8.03 -Groundwater System Dewatering trenches are typically located around the perimeter of the current mining phase. Settling will occur in the trenches, and if necessary, settling ponds will be constructed at a point prior to discharge. Discharges will be to the Cache La Poudre River at various points as designated within the NPDES Permit for this site. As indicated in our application, a copy of the NPDES permit will be submitted to DMG when the permit is issued. 2. The proposed gravel mining operations will impact the alluvial groundwater aquifer at the proposed facility. This is because dry mining operations are proposed to a depth below ground surface of 30 fl. The alluvial aquifer system at the proposed facility is in close proximity to the Cache La Poudre River. The aquifer is generally characterized by coarse, well graded gravels extending from a few feet below ground surface to a total depth of approximately 70 feet. Within these alluvial materials, groundwater generally occurs between 8 and 10 feet below ground surface. Therefore, there appears to be an approximately 62 foot saturated thickness within the alluvial aquifer in the vicinity of the facility. Groundwater gradients and horizontai flow direction are somewhat difficult to determine based on existing well data. This is because existing well data indicate a relatively flat groundwater surface in the vicinity of the facility. However, it can reasonably assumed that there is a gentle horizontal gradient toward the Cache La Poudre River in the vicinity of the facility. Aquifer ttansmissivity is estimated based on a total samrated aquifer thickness of approximately 62 feet and assumed hydraulic conductivity of the gravel materials of 1 x 10-2 cm/sec. This yields a calculated aquifer transmissiviry of approximately 19 cm/sec. 3. The applicant proposes to use "Option C" to demonstrate that impacts to surface and groundwater will be minimized both during mining and reclamation for the proposed facility. The applicant commits to mitigating any adverse impacts to ground water levels surrounding the facility during operation and reclamation of the facility. Because the mine plan calls for dry mining down to 30 feet, it is anticipated that this dry mining will produce the maximum groundwater drawdown in the vicinity of the proposed facility \\DEN Vnnunon\PRO)ECrS\20167 Greeley\RCSpon< io iech Rev2.da