2010-03-29_REVISION - C1981019 (3)

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• • specifications to comply with the safety factor requirements of Rule 4.05.6 and 4.05.9; and Rule 2.05.3(4)(a)(vii) requires a stability analysis of the structure. Colowyo Response: Additional pond design information is provided with this submittal in Volume 18, Exhibit 7, Item 26. The associated geotechnical information for the embankment stability is included with the geotechnical report for the Collom Temporary Spoilpile design. This is provided in Volume 20, Exhibit 23, Item 1. Rule 2.05.3(6) - Overburden and Rule 4.09 - Excess Spoil 14. On page 89 of Section 2.05.3(6) Colowyo provides a brief description of a proposed temporary overburden stockpile. This stockpile is proposed to contain approximately 250,000,000 cubic yards of overburden, will be placed in the Little Collom Gulch drainage, covers more than 500 acres and will remain in place for more than 22 years. Colowyo states that the temporary spoil pile will be used to fill and recontour the final pit sequence in the final two years of mining. The discussion under Rule 4.09 also refers to the temporary fill and states, "no excess spoil is expected under the proposed mine plan. Should disposal of excess spoil be anticipated, a construction plan will be developed. The construction plan will follow methods approved in the previously approved permit." Colowyo has also proposed an inspection plan stating that, "Should plans change and permanent disposal of excess spoil occur out of pit, Colowyo will provide certified reports". A generalized description of the construction techniques has been provided. Given the large volume of material proposed to be stored in the temporary stockpile, the location in the drainage and the acreage involved; Colowyo must provide further justification that the temporary pile is needed for the duration of mining. A description and design of this temporary overburden should also be included. At this point the Division does not have sufficient information in the PR-3 application to evaluate this proposal. • Colowyo Response: Map 29C - Temporary Spoil Pile Design provides a plan view and two profiles of this spoil pile design. Map 23B - Mine Plan is being resubmitted due to a change in the Temporary Spoil Pile design. The geotechnical report for the Collom temporary spoil pile is provided in Volume 20, Exhibit 23, Item 1. The volume of spoil generated by mining the targeted seams proposed in the mine plan lead to the necessity of creating a large temporary spoil pile. Estimated overburden volumes are presented on Table 2.05.2-3 (Total Collom Coal Production). 15. On page 90 of Section 2.05.3(6) Colowyo provides a brief discussion regarding the overburden sampling program for each pit and special handling procedures. Colowyo states that based on the similarities between the South Taylor and Collom mining areas, no special handling procedures will be necessary and references Volume 1. Volume 1 has not been updated or edited to include any supporting site specific Colowyo Mine C-1981-019 page 6 of 16 25 March 2010 Permit Revision 03 - Collom Permit Expansion