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pertaining to Colowyo's discharges..." It is important to note that this statement does not reflect <br />the regulatory authority of the Division and Rules that relate specifically to surface water <br />discharges from disturbed areas include Rules 2.05.6(3)(b)(ii), 4.05.2(2), 4.05.2(7), and <br />4.05.13(2)(a)(11). The Division is always open to discuss the regulatory authority pertaining to <br />discharges and their impacts on water quality in receiving waters. <br />9. Within the Letter, Tri-State alludes to toxicity impacts based on WET testing of the discharge <br />from Outfall 010. However, no additional detail was provided. Per Rule 4.05.8(3), "... [a]cid- <br />forming or toxic -forming spoil or underground development waste to be stored shall...... <br />minimize impacts to surface water...". Details regarding toxicity impacts of the discharge should <br />be shared with the Division in order to ensure compliance with Rule 4.05.8(3). Additionally, the <br />Division should be included in discussions between Tri-State and the Water Quality and Control <br />Division (WQCD) concerning a non-compliant discharge and plans for the treatment. Please <br />provide the Division with a summary of the discussions between Tri-State and WQCD, <br />including details of the proposed treatment plan and justification for the proposed timescale <br />(greater than three 3 years before implementation). <br />10. Tri-State notes on page 1 of the Letter that an increase in TDS "is being minimized." Please <br />provide additional information, data, or discussion concerning the accomplishment of <br />minimizing the increases in TDS in the past and any procedures that minimize TDS <br />concentrations currently. <br />Alluvial Groundwater Points of Compliance <br />11. The Division concurs with the approach proposed in the Tri-State and anticipates resuming the <br />discussion at a meeting in fourth quarter of 2020. <br />This concludes the Divisions review of the Letter from Tri-State Generation and Transmission Association <br />Inc. on behalf of the Colowyo Mine, dated June 8, 2020. If you have any questions, feel free to contact me at <br />any time. <br />If you have any questions, feel free to contact me. <br />Sincerely, <br />Zach Trujillo <br />Environmental Protection Specialist <br />(303) 866-3567 ext. 8164 <br />Zach.Truj'illo@state.co.us <br />