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uranium ore, affecting the staging area and structures near the shaft. The surface of this area has not <br />undergone final reclamation nor been checked for adequate removal of traces of ore, and future use of the <br />site may again include the handling of ore. As such, the current presence of a toxic-forming material on the <br />permitted area justifies the Division's determination that this mine is a DMO. If Denison disputes that <br />uranium is a toxic-forming material or contends that uranium is not present in the permitted area please <br />provide the rationale explaining that position. <br />Environmental Protection Facilities (EPFs). In Section 6.0 Denison states, "...future EPFs are not planned to <br />be constructed, because neither designated chemicals, nor toxic- or acid-forming materials or acid rock <br />drainage are present at the Van 4 Mine." <br />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 Division believes that uranium is present, even if it is restricted to traces of ore and <br />low-grade ore that were stored or handled on the working surface of the staging area pad and ore bins where <br />it may be incorporated into the pad material. That area's surface is not lined and the subsurface material is <br />permeable, which allows leachate from the ore to potentially migrate into the ground. Please state whether <br />there are other areas of the site, based on the justification given above, that should be considered as EPFs and <br />if applicable, a plan for remediation or improvement. <br />Ore storage pad. The Division is not aware of any ore presently stored on the pad or in the ore bins, nor of <br />any new ore being mined, though the permit is approved for such activities when mining resumes. If and <br />when mining and stockpiling of ore resumes, the Division assumes that the residence time of the stockpiled <br />ore will be only a matter of days. Pursuant to Hard Rock/Metals Rule 6.4.20(7) it is appropriate that the ore <br />stockpile areas be considered EPFs. Prior to future stockpiling, Denison must demonstrate that the existing <br />ore stockpile areas provide adequate containment of runoff and leachate of the toxic-forming materials, or <br />perform the construction tasks necessary for the ore pad to provide such containment. Please see the <br />attached "General Ore Pad Construction Criteria." Please demonstrate that the ore pads have been properly <br />constructed and tested to meet those requirements, or propose a construction and certification plan, with a <br />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 requires that stormwater runoff originating from the affected <br />areas (pad surfaces and slopes, stockpile areas, and roads) be controlled adequately. In light of the thorough <br />treatment of these items, indicated in the Stormwater Management Plan (SWMP) prepared for CDPHE- <br />WQCD, the Division considers such runoff and its control during the mine's active and inactive phases to be <br />adequately addressed. However, the EPP states that certain stormwater control structures will be permanent, <br />and remain on the site after final reclamation. The SWMP document, included in this EPP within <br />Attachment D, reiterates the statement that certain Swales and Diversion Ditches will be permanent and