2024-08-29_PERMIT FILE - C1980007 (2)

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West Elk Mine 2.05-31 Rev. 06/05, 01/06, 03/06, 04&05/06- PR10; 01/09- MR350; 04/09- TR116; 05/09- MR354; 08/09- TR119; 5/20- MR443; 10/20- MR450; 10/21- MR456; 6/24-TR156 silt fence, natural vegetative debris, excelsior or straw waddles, and/or sediment traps. If a sediment pond is in the vicinity of the site, drainage could be routed to the pond. (4) Ponds, Impoundments, and Diversions During the course of construction and operation of the mine facilities at West Elk Mine, every effort is made to minimize water pollution. It is MCC's intent to discharge water from sediment ponds, Small Area Exemptions, and from the mine in compliance with all applicable effluent limitations. To fulfill this commitment, all surface drainage from the affected mine area is collected and treated prior to being discharged from the permit area. All surface runoff from undisturbed areas is directed away from the affected mine area through diversion channels. Maps 54, 54A, and 54B show the distribution of sediment control structures at West Elk Mine. Map 54 and Map 54A identify the sub-watershed drainage basins, tributary drainage basin information, and ditch/culvert layouts in conjunction with the main surface facilities area and Lone Pine Gulch, respectively. Maps 1E, 2E and 3E in Exhibit 66 identify the watersheds in the Sylvester Gulch Facilities Area. Map 54B shows the ditch and culvert locations in conjunction with the Sylvester Gulch Facilities Area. The following sections deal with each specific hydrologic protection measure. Hydrologic Studies and Methodology Studies have been completed to estimate the peak runoff and flood volume for storms having specific recurrence intervals for the West Elk Mine area. Exhibit 44 is the Merrick and Company report used in the design of the original sedimentation ponds MB-1 (converted to FW-2)), MB-2, and MB-3, and associated ditches and culverts. This report was submitted to the State Engineer for the approval of these three original sedimentation ponds, as well as freshwater pond FW-1. Approval was received on February 3, 1981, and is included in Exhibit 45. Exhibit 66 contains the current designs for ponds MB-3. The Exhibit 43 and Exhibit 44 designs are no longer valid for ponds MB-2 or MB-3. Exhibit 66 contains an as-built drawing that reflects the addition of a dike in pond MB-1 to create a north and south cell. However, the drawings included in Exhibit 43 do accurately reflect other structures associated with pond FW-2 (formerly pond MB-1) including the primary and emergency spillway designs. Exhibit 66 also contains the design information for SG-1 located at the Sylvester Gulch Facilities Area. See Exhibit 46 for the original design specifications and for the current designs for MB-4, Unit Train Loadout Sedimentation Pond. Pond MB-4 was relocated in 1998 from the east side of the train load-out to an area west of the load-out between two sets of train tracks. The relocated sediment pond is constructed of concrete and is preceded by an oil skimmer and a sediment trap. New sediment pond MB-5E replaces sediment ponds MB-1, MB-2R and MB-5. Design criteria for the original pond MB-5 are contained in Exhibit 47, and designs for the new pond MB-5E are located in Exhibit 47A and in Exhibit 66. Pond MB-1 was converted to Freshwater pond FW-2 and Ponds MB-2, MB-2R, MB-5 and MB-6 no longer exist. Design criteria for the Refuse Pile Expansion (RPE) pond, designated the "RPE" pond, are included in Exhibit 70. Hydrologic Design of Runoff Ponds Five stormwater sediment control structures are used as settling ponds for stormwater runoff from the mine site. These ponds have been designed according to CDRMS regulations (see Exhibits 43, 47, 66, and 70). These ponds have been constructed to contain an estimated three years of sediment storage volume and a runoff storage volume resulting from the 10-year 24-hour rainfall event. Sediment will be excavated, allowing for additional storage, when sediment has reached the maximum storage capacity. Sediment volumes are estimated by a quarterly visual evaluation. The smaller ponds, MB-3 and MB-4, are usually dry during a portion of the year and sediment levels, relative to the primary discharge structure elevations, can be visually determined. The larger ponds usually contain water and visual evaluations are less accurate. These ponds, MB-5E, SG-1 and RPE ponds, will be surveyed at least every three years to determine the actual sediment levels.