2018-03-20_PERMIT FILE - C1981019A (3)

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RULE 4 PERFORMANCE STANDARDS pass the 25 -year, 24-hour storm event in accordance with Rule 4.05.9(2)(c)(i). The design requirements for existing ponds can be found on each of the pond as -built drawings or in Exhibit 7, Item 15. All sedimentation ponds will provide a non -clogging dewatering device or conduit spillway to remove water storage from inflow. Design requirements for all sediment ponds associate with the Collom Pit be found in Exhibit 7, Item 23. 4.05.8 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. 4.05.9 Permanent and Temporary Impoundments Colowyo constructs small impoundments on reclaimed areas in accordance with Rule 4.05.9. 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 are 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 areas. 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 similar rangelands. Since the source of water is surface runoff from revegetated areas the quality of the water will meet the requirements of the intended use. The post -mining impoundments have slopes of 3h:Iv 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 are met. Prior to construction, all designs are submitted to the Division. A copy of the as -built design information will be submitted after construction for inclusion into the permit document. In addition, sedimentation ponds that are subsequently approved as part of the post -mining land use, as shown on the hydrology Maps, 41A and 4113, will remain as permanent impoundments after the requirements of Rule 4.05.9 have been met. Please refer to Section 4.05.6 for additional information regarding compliance with Rule 4.05.9(7)(a thru e). All embankments, impoundments, and associated structures will be revegetated if construction materials are 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) if and until a waiver is granted to allow for annual inspections of these structures in the future. As per Rule 4.05.9(14) requirements, inspections performed during and after construction of these structures will be performed by a qualified registered professional engineer or other qualified professional specialist under the direction of a professional engineer. The inspections will be made regularly during construction, at completion of construction, and at least annually (quarterly until such a time as annual inspections are requested from granted by DBMS) until removal of the structure or release of the performance bond. The qualified registered professional engineer shall provide the Division with a certified report that the impoundment has been constructed and/or maintained as designed, and in accordance with the approved Rule 4 Performance Standards 4-11 Revision Date: 1/31/18 Revision No.: TR -119