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DRMS response: Again, it is the Division's position that uranium is a toxic-forming material and that this <br />permit is a DMO. The uranium on the surface may be restricted to its presence in the ore and low-grade ore, <br />that are stored on the pad, and the working surface of the pad. There may be more locations and/or <br />structures within the permitted area which are affected by or come in contact with this material, and should <br />be identified by the operator to demonstrate that they are compliant with the minimum applicable standards <br />of EPFs. Please state whether there are additional EPFs that can be identified at the site, based on the <br />justification given above, that should be considered for inclusion and if applicable, a plan for structural <br />improvement. <br />Ore storage pad. Denison has provided documentation of the residence time of the ore while stockpiled, <br />which appears to be only a matter of days. The low-grade ore, however, remains exposed on the pad surface <br />for a longer period of time. The stockpile areas themselves are on the unlined surface of the development <br />rock of the staging area. Pursuant to Hard Rock/Metals Rule 6.4.20(7) it is appropriate that the ore stockpile <br />areas be considered EPFs. Denison must demonstrate that the existing ore stockpile areas provide adequate <br />containment of runoff and leachate of the toxic-forming materials, or perform the construction tasks <br />necessary for the ore pad to provide such containment. Please see the attached "General Ore Pad <br />Construction Criteria." Please provide a statement as to whether the ore pads have been properly constructed <br />and tested to meet those requirements, or propose a construction and certification plan, with a timeframe. <br />Unsaturated (UNSAT-H) model and percolation estimation. Denison has provided information showing the <br />limited mobility and reduced threat from various minerals in the mined and unmined rock material, based on <br />the geologic characteristics as well as the and climate at the mine. The wettest months are August through <br />October, which suggests that precipitation during those months is delivered via thunderstorms - potentially <br />high intensity events. It is known that plumes can form beneath waste rock facilities in and climates in <br />response to seasonal patterns of such high intensity events. Please address the following: Does the model <br />account for high-intensity, short-duration precipitation events such as thunderstorms? If not, what effect <br />would these have on percolation estimates? <br />Permanent stormwater structures. The Division has questions regarding control of stormwater runoff <br />originating from the affected areas (pad surfaces and slopes, stockpile surfaces, and roads). Such runoff and <br />its control during the mining phase (including periods of temporary cessation, if any) are considered by this <br />office to be adequately addressed. However, the EPP states that certain stormwater control structures will be <br />permanent, and remain on the site after final reclamation. The Stormwater Management Plan (SWMP) <br />prepared for CDPHE-WQCD, and included in this EPP within Attachment F, reiterates the statement that <br />certain Swales and Diversion Ditches will be permanent and remain onsite, though which specific structures <br />are not identified. It is the Division's concern that there may be some such structures onsite that are planned <br />to remain after reclamation (understood to be after monitoring and maintenance by the operator have ceased) <br />that may not be able to continue functioning adequately to control, convey or divert their designed working <br />capacity. The design capacity and the design storm event were not found described in the EPP or in the <br />appended SWMP. For all such permanent stormwater control structures, please confirm that they are <br />designed to handle I00-year, 24-hour events. If such statement cannot be made, please provide a <br />commitment to construct and certify the necessary structure capacity, with a timeframe. (Please be aware <br />that approval to leave this type of structure may also have to be obtained from the BLM. If so, please <br />provide copy of such approval.)