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RULE 4 PERFORMANCE STANDARDS <br /> applicable regulations. As per Rule 4.05.9(15),certified inspection reports shall include discussion <br /> of: <br /> 1) Any appearance of erosion, instability, structural weakness or other hazardous <br /> conditions; <br /> 2) Existing and required monitoring procedures and instrumentation; <br /> 3) The depth and elevation of any impounded waters at the time of the certified report; <br /> 4) Existing storage capacity of the impoundment; and <br /> 5) Any other aspects of the structure affecting stability, or requiring maintenance. <br /> Colowyo will maintain a copy of each certified report at the mine site. <br /> Colowyo successfully demonstrated that failure of small impoundments would not create a threat <br /> 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, Volume 2B, <br /> in accordance with rule 4.05.9(18)(b). None of the small post-mining impoundments act as <br /> primary sediment control structure for a particular area; they are all constructed in reclaimed areas <br /> of the mine to enhance the approved postmining land use; they are 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 ditches, <br /> culverts, spillways, and other outflow structures free of debris. All combustible material, other <br /> than mulch or other material needed for erosion control and surface stability (vegetative growth) <br /> 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 such <br /> modification is necessary on an emergency basis for public health,safety or the environment would <br /> be endangered. <br /> Colowyo will inspect the condition of each pond quarterly (until a waiver for annual inspection is <br /> granted) with the reports submitted quarterly as well. None of Colowyo's post-mining <br /> impoundments will meet the size criteria of 30 CFR 77.216(a)(1989). <br /> 4.05.10 Underground Mine Entry and Access Discharges <br /> Colowyo currently conducts surface coal mining exclusively. <br /> 4.05.11 Ground Water Protection <br /> There are no aquifers or continuous sources of ground water within the stratigraphic section from <br /> which the Colowyo Mine mines coal using surface mining techniques. This is also noted in Section <br /> 2.04.7. In addition, there are no continuous aquifers of regional extent within the entire Williams <br /> Fork Formation in the location of the Colowyo Mine. Occasionally, a minimal amount of water <br /> is found under perched conditions in noncontiguous lenticular sandstones and in fractured coal <br /> Rule 4 Performance Standards 4-14 Revision Date: 12/20/19 <br /> Revision No.: TR-135 <br />