2005-01-04_REVISION - M1999120 (2)

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Kate Pickford Page 4 of 7 Division of Minerals and Geology January 3, 2005 accommodated, either hydroseeding or drill seeding will be used. Regarding water storage reservoirs, the applicant commits to implementing 3:1 slopes (or less steep) for the water storage reservoir. The applicant respectfully disagrees with the recommendation that reservoir slopes be 4:1 or 5:1 to accommodate wildlife. Decreasing the slope will reduce the water storage capacity in each reservoir, thus decreasing the economic feasibility of creating such reservoirs. The reclamation plan for this site is water storage, and the reservoirs are not designed to create wildlife habitat. Wildlife habitat is preserved within the 200 foot setback along the South Platte River. Regarding reclamation revegetation, the applicant had proposed seed mixes based on what was previously recommended by NRCS and approved in the application process for the existing operation. A comparison of seed species proposed by the applicant and by NRCS shows that 4 of 6 of the seed species are the same, and the applicant's seed mixes list an additional 3 species. We believe the applicant's proposed mix to be equivalent to that proposed by NRCS, and, based on Lynn Mayer's discussions with Gregg Squire of the Division during the preparation of this amendment application, slightly more cost effective. Regarding surface and subsurface water, the applicant has addressed the effects of the proposed amendment on water resources in the following section. In general, the applicant would like to point out that the proposed mining operation does not contribute to an overall loss of water resources, as any evaporative or other losses are required to be augmented by the Office of the State Engineer, through the approval of a Substitute Water Supply Plan (SWSP) and Gravel Well Permit. Rule 6.4.7 Exhibit G -Water Information 7) Disturbance to the Hydrologic Balance: Please note that the applicant is committing to the installation of a slurry wall in each phase prior to mining below the water table. Wright Water Engineers has addressed this issue in more detail in the attached letter report. 8) Mitigation Plan: Wright Water Engineers has performed modeling and research as to the potential effects of the slurry wall on surrounding wells, and their letter report is attached. The report concludes that there may be a shadow effect from the proposed operation, and that 5 registered alluvial wells may be located in the shadow zone. The report also recommends mitigation measures in the event that shadowing resulting from this operation affects the ability of a well owner to pump his adjudicated water rights. The applicant has committed to monthly well monitoring for the life of the operation, as described in the amendment application. The only change to this plan is that 14 wells are being monitored, instead of the 16 originally proposed. Piezometers #15 and #16 were damaged during slurry wall construction, and therefore will not be available for future monitoring. Exhibit G: Monitor Well Locations has been revised to show this change, and is included with this response.