2019-04-03_REVISION - C1981019 (3)

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1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http://mining.state.co.us John W. Hickenlooper, Governor | Mike King, Executive Director | Virginia Brannon, Director 1313 Sherman Street, Room 215 Denver, CO 80203 Interoffice Memorandum April 3, 2019 From: Leigh Simmons To: Zach Trujillo Subject: Colowyo Mine (Permit No. C-1981-019) TR-125 This memo is in response to the March 7, 2019 letter submitted by Tri-State Generation and Transmission Association Inc. (Tri-State) on behalf of Colowyo Coal Company (CCC). I have not attempted to provide a complete response to every point raised in the March 7 letter, or to thoroughly review the proposed revised pages, since the principal point of difference between Tri-State and the Division is fundamental rather than buried in the details. Tri-State appears to disagree with the Division’s interpretation of Rule 4.05.13, and continues to assert that there is no requirement for groundwater points of compliance (POC) in the alluvial aquifers of Wilson Creek, Taylor Creek and Good Spring Creek. The Division interprets 4.05.13(b) to mean that a POC is required (i) where a coal mining operation has the potential to negatively impact groundwater quality, (ii) where groundwater quality standards have been established by the Water Quality Control Commission (WQCC). In this case both conditions are satisfied, i.e. (i) all parties acknowledge the potential for negative impacts to alluvial groundwater in the Wilson Creek, Taylor Creek and Good Spring Creek drainages, and (ii) the Interim Narrative Standard from Regulation 41 applies (since WQCC has not classified groundwater in the vicinity of the Colowyo mine); so the rules require that POC be established. None of the additional factors for consideration mentioned in 4.05.13(b)(ii) negate the basic requirement to establish POC, although some of the factors may be pertinent in determining appropriate locations.