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RULE 4 PERFORMANCE STANDARDS <br /> <br />Rule 4 Performance Standards 4-13 Revision Date: 4/9/25 <br /> Revision No.: MR-261 <br />4.05.9 Permanent and Temporary Impoundments <br /> <br />Colowyo constructs small impoundments on reclaimed areas in accordance with Rule 4.05.9. <br />These small impoundments are essential and basic to the management of the rangeland post- <br />mining land use of livestock grazing and wildlife habitat. The design of post-mining <br />impoundments provides for structures having a vertical height less than five feet from the bottom <br />of the channel to the bottom of the spillway and impound less than two acre-feet of water. As such <br />they are exempt from Division of Water Resources, Office of State Engineer requirements. Water <br />harvesting ditches may also be used to enhance the function of the impoundments, which is <br />consistent with practices employed on adjacent rangelands. <br /> <br />The impoundments collect surface runoff from precipitation events and snowmelt from reclaimed <br />areas. The impoundments do not result in the diminution of the quality or quantity of water for <br />downstream water users. Colowyo is the holder of water rights immediately downstream. During <br />periods of low precipitation, the impoundments may be dry, which is consistent with regional <br />practices on similar rangelands. Since the source of water is surface runoff from revegetated areas <br />the quality of the water will meet the requirements of the intended use. <br /> <br />The post-mining impoundments have slopes of 3h:1v or less to provide easy access to both <br />livestock and wildlife. These impoundments and any associated ditches, while intended to be <br />permanent, will be classified as temporary until the requirements of Rule 4.05.9 are met. Prior to <br />construction, all designs are submitted to the Division. A copy of the as-built design information <br />will be submitted after construction for inclusion into the permit document. In addition, <br />sedimentation ponds that are subsequently approved as part of the post-mining land use, as shown <br />on Map 12, will remain as permanent impoundments after the requirements of Rule 4.05.9 have <br />been met. Please refer to Section 4.05.6 for additional information regarding compliance with <br />Rule 4.05.9(7)(a thru e). <br /> <br />All embankments, impoundments, and associated structures will be revegetated if construction <br />materials are conducive to plant growth. If not, rock or gravel will be used on the embankments. <br />The quarterly routine inspections of these structures will be conducted as required by Rule <br />4.05.9(17) if and until a waiver is granted to allow for annual inspections of these structures in the <br />future. As per Rule 4.05.9(14) requirements, inspections performed during and after construction <br />of these structures will be performed by a qualified registered professional engineer or other <br />qualified professional specialist under the direction of a professional engineer. The inspections <br />will be made regularly during construction, at completion of construction, and at least annually <br />(quarterly until such a time as annual inspections are requested from granted by DRMS) until <br />removal of the structure or release of the performance bond. The qualified registered professional <br />engineer shall provide the Division with a certified report that the impoundment has been <br />constructed and/or maintained as designed, and in accordance with the approved plan and the <br />applicable regulations. As per Rule 4.05.9(15), certified inspection reports shall include discussion <br />of: <br /> <br />1) Any appearance of erosion, instability, structural weakness or other hazardous <br />conditions; <br />2) Existing and required monitoring procedures and instrumentation;