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appended SWMP. For all such permanent stormwater control structures, please confirm that they are <br />designed to handle 100-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.) <br />Stormwater detention ponds. A similar concern exists for the design and capacity of the runoff detention <br />ponds at the site. The specifications of the ponds were not found in the EPP or SWMP. Regardless of <br />whether the ponds are to be temporary or permanent, please verify that the slopes of the embankments are <br />constructed at a maximum gradient of 2:1, and what the size of storm event they are designed for (e.g., <br />interval and duration). <br />Existing underground water monitoring wells. The Division agrees that continued sampling from the <br />monitoring well "nest" is necessary to establish baseline water quality and to track future changes in the <br />quality. Note: Those wells are within the underground workings of the West Sunday Mine (another <br />permitted mine in Denison's Sunday Group), and they will be regulated, monitored and reported separately <br />under that other permit. <br />Proposed "compliance" monitoring wells. The Division agrees with Denison's choices for the proposed well <br />locations and geologic strata to be intercepted, being hydrologically downgradient from the underground <br />mine workings of the Sunday Mine Group. Note: Those wells are within the permitted area boundaries of <br />other permitted (112d) mines in Denison's Sunday Group, and will be regulated, monitored and reported <br />separately under those other permits. <br />Post-mining mine pool. There is a history of standing water in portions of the workings of the mines in the <br />Sunday Group, but the potential for the existence of and impacts from a post-mining mine pool have not <br />been adequately discussed. It appears from the groundwater margin depicted in Figure 1 that the mine pool <br />is in the workings of several of the mines of the Sunday Group, and this issue will therefore be handled under <br />another of the mine permits. <br />Post-mining use of the site. Denison defines the future use of the site as "non-motorized recreation." It is <br />unclear if this is a BLM land use designation or if this name stated herein is provided in a framework for the <br />reclamation plan under the DRMS permit. Non-motorized use, however, seems questionable to this office <br />because old mine sites are very popular with ATV users. Will there be an attempt made to restrict access to <br />ATV and other motorized recreationists in the post-mining condition? Is this future use in conformance with <br />the plan approved by BLM? <br />Division's decision date. The original decision date was set upon the Division's initial finding that the <br />amendment application was complete, but due to its complexity the decision date was extended to September <br />4, 2009. During further review the Division has identified several complex items that Denison must address <br />before the amendment may be considered adequate for approval. There are numerous issues discussed in the <br />preceding paragraphs that are also required to be answered under other permit amendments (among other <br />"Sunday Group Mines" permits) and an extension of this amendment decision will ensure that they will be <br />adequately resolved in a concurrent and consistent manner. The complex nature of this amendment requires <br />this office to again extend the decision date by 60 days, to be reset to November 3, 2009. Please be <br />reminded that the issues identified in this adequacy review letter must be adequately addressed for this office