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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 213, <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(x)(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: 5/25/18 <br />Revision No.: RN -07 <br />