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RULE 4 PERFORMANCE STANDARDS <br />WAVOM <br />regional practices on similar rangelands. Since the source of water is surface runoff from <br />revegetated areas the quality of the water will meet the requirements of the intended use. <br />The post- mining impoundments have slopes of 3h:ly 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 Exhibit 7, Item 23. In addition, <br />sedimentation ponds that are subsequently approved as part of the post- mining land use, as shown <br />on the hydrology Map 41B, will remain as permanent impoundments after the requirements of <br />Rule 4.05.9 have been met. <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). <br />The Division granted Colowyo a waiver to the requirements of 4.05.9(17) for small <br />impoundments. The waiver applies only to impoundments which are not the primary sediment <br />control structure for a particular area; are constructed in reclaimed areas of the mine to enhance <br />the approved postmining land use; are completely incised, or have a storage capacity no greater <br />than two -acre feet and an embankment no greater than five feet in height. The small <br />impoundments will be inspected on a yearly schedule until removal of the structure or release of <br />the performance bond as directed in rule 4.05.9(14). The inspections will be performed by a <br />qualified registered professional engineer, or other qualified professional specialist under the <br />direction of a professional engineer, or a qualified person other than, and not under the direction <br />of, a professional engineer. <br />Colowyo successfully demonstrated that failure of the small impoundments would not create a <br />threat to public health and safety or threaten significant environmental harm. A written safety <br />demonstration completed by a professional engineer is located in Exhibit 7, Item 11 of the <br />existing permit document in accordance with rule 4.05.9(18)(b). None of the small post- mining <br />impoundments act as primary sediment control structure for a particular area; they are all <br />constructed in reclaimed areas of the mine to enhance the approved postmining land use; they are <br />all under two -acre feet. <br />All impoundments will be maintained according to the specifications set forth in this part. <br />Maintenance for impoundments may include (if necessary) mowing and cutting of excess <br />vegetative growth for the purpose of facilitating inspections and repairs including keeping <br />ditches, culverts, spillways, and other outflow structures free of debris. All combustible material, <br />other than mulch or other material needed for erosion control and surface stability (vegetative <br />growth) will be removed. <br />Plans for any modification of any sedimentation impoundments or dams will be submitted to the <br />Division, and no modification will begin until approval of the plans have been granted unless <br />such modification is necessary on an emergency basis for public health, safety or the environment <br />would be endangered. <br />Colowyo will inspect the condition of each pond annually with the reports submitted annually. <br />None of Colowyo's post- mining impoundments will meet the size criteria of 30 CFR <br />77.216(a)(1989). <br />Collom —Rule 4, Page 10 Revision Date: 1/23/09 <br />Revision No.: PR -03 <br />