2019-03-06_REVISION - C1981019 (2)

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TRI-STATE GENERATION AND TRANSMISSION ASSOCIATION, INC. HEADQUARTERS: P.O. BOX 33695 DENVER, COLORADO 80233-0695 303-452-6111 March 7, 2019 Mr. Zach Trujillo Environmental Protection Specialist Colorado Division of Reclamation, Mining & Safety Department of Natural Resources 1313 Sherman Street, Room 215 Denver, CO 80203 RE: Colowyo Coal Company L.P. Permit No. C-1981-019 Technical Revision No. 131 Adequacy Response Dear Mr. Trujillo, Tri-State Generation and Transmission Association Inc. (Tri-State), is the parent company to Axial Basin Coal Company, which is the general partner to Colowyo Coal Company L.P. (Colowyo). Tri-State received your adequacy letter dated March 6, 2019 and is providing the response below to your adequacy concern on behalf of Colowyo. The Colowyo Mine operates under Permit No. C-1981-019. 1. When reviewing Table I — SCS Curve Numbers on Exhibit 7, Page 4, it is observed that Note 5 has been removed from the table. However, the superscript still exists attached to "Reclaimed" cover for a cover type of "3+ Year Growth ". Please provide the Division a reason for Note 5 removal and please send a corrected proposed Table 1 — SCS Curve Numbers either removing the superscript or including Note 5. Response: The superscript for note 5 was mislabeled and should have been note 4. It has been corrected and the page resubmitted herein. 2. It appears to the Division that there are some acreage discrepancies between the currently approved watershed area associated with the Section 28 Pond, the proposed acreage adjustments included with the proposed Exhibit 7, and what has been stated under the Colowyo Mine TR -131 Application for Revision. As requested under the TR -131 application, Colowyo noted an 8.1 acre reduction in disturbance. However, when comparing the proposed Exhibit 7 changes provided with TR -131 to the currently approved Exhibit 7, there is a 0.4 disturbed acre increase within the hydrology model as well as a 20.9 acre reduction to the total watershed boundary associated with the Section 28 Pond. Please provide the Division more information for these acreage discrepancies. Response: The 0.4 acres increase in disturbance reflected in the hydrology model submitted under TR -131 was based on "actual" on the ground disturbance that was not accounted for, nor had occurred, prior to Exhibit 7 being updated under TR -131. The 20.9 acres reduction is because the previously approved watershed boundaries for the Section 28 Pond watershed were not entirely correct. The major reduction occurred south of the Section 28 and Section 29 ditches that was previously modeled to be contributing AN EOUAL OPPORTUNITY/AFFIRMATIVE ACTION EMPLOYER CRAIG STATION ESCALANTE STATION NUCLA STATION t P.O. BOX 1307 P.O. BOX 577 P.O. BOX 698 A Touchstone Energy'Cooperative � ` CRAIG, CO 81626-1307 PREWITT, NM 87045 NUCIA, CO 81424-0698 II \\ 970-824-4411 505-876.2271 970-864-7316