2008-05-29_PERMIT FILE - C1981019A (4)

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RULE 4 PERFORMANCE STANDARDS __ ~_- .~:.~~ ~_~_ ~ __. „~_-._x~~-r~ ,~ ~ `~~__:: M 4.OS.S Acid-forming and Toxic-Forming Spoil Acid forming materials do not exist within the overburden to be removed by the mining operations. A discussion on the overburden at the Colowyo operation has been conducted as set forth in Section 2.04.6. A discussion of the overburden monitoring plan is set forth in Section 2.05. Acid-Base Accounting shows that almost none of the encountered interburden has a net acid-generating potential, and the average acid-neutralizing potential to acid-generating potential ratio ranges from about 50 to about 90 in each borehole in the proposed pit, indicating that there is 50 to 90 times more acid-neutralizing potential than there is acid-generating potential in the interburden (Exhibit 6, Item 6). 4.05.9 Post-Mining Impouudmeuts Colowyo constructs small impoundments on reclaimed areas in accordance with Section 4.05.9 of the CMLRD regulations for Coal Mining, 3/21/01. These small impoundments are essential and basic to the management of the rangeland post-mining land use of livestock grazing and wildlife habitat. The design of post-mining impoundments provides for structures having a vertical height less than five feet from the bottom of the channel to the bottom of the spillway and impound less than two acre-feet of water. As such they aze exempt from Division of Water Resources, Office of State Engineer requirements. Water harvesting ditches may also be used to enhance the function of the impoundments, which is consistent with practices employed on adjacent rangelands. The impoundments collect surface runoff from precipitation events and snowmelt from reclaimed azeas. The impoundments do not result in the diminution of the quality or quantity of water for downstream water users. Colowyo is the holder of water rights immediately downstream. During periods of low . precipitation, the impoundments may be dry, which is consistent with regional practices on similaz rangelands. Since the source of water is surface runoff from revegetated azeas the quality of the water will meet the requirements of the intended use. The post-mining impoundments have slopes of 4h:ly or less to provide easy access to both livestock and wildlife. These impoundments and any associated ditches, while intended to be permanent, will be classified as temporary until the requirements of Rule 4.05.9 aze met. Prior to construction, all designs aze submitted to the Division. A copy of the as-built design information will be submitted after construction for inclusion into Exhibit 7, Item 20. In addition, sedimentation ponds that are subsequently approved as part of the post-mining land use, as shown on the hydrology -South Map (Map 12), will remain as permanent impoundments after the requirements of Rule 4.05.9 have been met. All embankments, impoundments, and associated structures will be revegetated if construction materials aze conducive to plant growth. If not, rock or gravel will be used on the embankments. The quarterly routine inspections of these structures will be conducted as required by Rule 4.05.9(17). The Division granted Colowyo a waiver to the requirements of 4.05.9(17) for small impoundments. The waiver applies only to impoundments which are not the primary sediment control structure for a particulaz area; are constructed in reclaimed azeas of the mine to enhance the approved postmining land use; are completely incised, or have a storage capacity no greater than two-acre feet and an embankment no greater than five feet in height. The small impoundments will be inspected on a yearly schedule until removal of the structure or release of the performance bond as directed in rule 4.05.9(14). The inspections will be performed by a qualified registered professional engineer, or other qualified professional specialist under the direction of a professional engineer, or a qualified person other than, and not under the direction of, a professional engineer. South Taylod[.ower Wilson-Rule 4, Pale IS Revision Date: 3/30/07 Revision No.: PR-02