2012-10-29_PERMIT FILE - M2012045 (6)

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(c) Compliance with applicable federal and Colorado dredge and fill requirements: The Operator will comply with all applicable federal and Colorado dredge and fill regulatory requirements. Where necessary, a Corp of Engineers 404 permit will be obtained prior to any dredging or filling of wetlands. At this time the Operator /Applicant is not aware of any wetlands that could be affected by the proposed operation. (d) Remove temporary or large siltation structures from drainage ways after disturbed areas are revegetated and stabilized, if required by the Reclamation Plan: Some earthen structures may remain as part of the post mining land use, (low earthen dams surrounding the excavated cells and a zoned perimeter dam are examples.). In addition, other structures may be retained to control erosion during site reclamation and into post bond release in order to comply with storm water control requirements. (2) Earthen dams, if necessary to impound water, may be constructed if the formation of such impoundments will not damage adjoining property or conflict with water pollution laws, rules or regulations of the federal government, the State of Colorado or with any local government pollution ordinances: Earthen dams will be constructed as part of the post mining land use in order to provide for maximum capacity for the developed water resource. Following is a conceptual discussion of the designs for each of the earthen dam structures, one of which will be a zoned perimeter dam. It is anticipated that all structures will not encroach upon the FEMA 100 year flood limit. (Appendix IV is a copy of the Design Report prepared for the SEO for the Phase One Reservoir.) It is anticipated that the cells will be constructed similarly. The structures will have an embankment structural crest at their highest point of approximately 19 feet with a crest width of about 20 feet. The structures will employ slurry walls that will extend from into the Pierre Shale bedrock, to several feet above the original ground surface, into the constructed earthen embankment. There will be a layer of clayey soils between the constructed earthen embankment and a slightly excavated original overburden surface. This layer will tie into and surround the slurry wall to effectively seal off the structure. The slope of the embankment exterior to the cell will be no steeper than 3h: lv. On the in -slope of these two cells, the area subject to wave erosion will have a slope of 3h: lv and suitable riprap. The remainder of the slope to the original ground surface will be no steeper than 5h: lv. There will then be an overburden bench approximately 50 feet in width. From there, the in -slope of the cell will extend to the floor of the excavated cell at 3h: 1 v. It is anticipated that these structures will have a full structure freeboard of approximately five (5) feet. In order to construct the zoned perimeter dam, overburden will be removed down to the Pierre Shale. Following overburden removal, the Pierre Shale will be slightly excavated to achieve a clean, non - weathered surface. The zoned perimeter dam will have a maximum structure crest of approximately 33 feet from the original ground surface and a crest width of approximately 30 feet. It will probably consist of three zones, Zones I Core, Zone II Shell and Zone III Filter Drain. Zone I Core is intended to be constructed of clayey soils with "interior slopes no steeper than lh: lv. This component of the zoned perimeter dam will be appropriately keyed into the Pierre Shale. Zone II Shell will be in -slope (upstream) and out -slope (downstream) to Zone I Core. In -slope Zone II Shell will likely be constructed of sands, gravels, and clays. It will slope inward toward the cell at a slope of 3h: lv in the region where the structure is subject to wave erosion. It will then slope down to the Pierre Shale at 5:1v. The 3h: lv areas subject to wave erosion will have suitable riprap. Out -slope Zone II Shell will be constructed similar to in -slope Zone II Shell. Its final slope from the crest of the structure to the original overburden surface will be 3h: lv.