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COLORADO <br />Division of Reclamation, <br />Mining and Safety <br />Department of Natural Resources <br />Date: January 27, 2020 <br />To: Rob Zuber <br />CC: Jason Musick <br />From: Zach Trujillo <br />RE: Bowie No. 2 Mine, DRMS File No. C-1996-083 <br />Bowie No. 2 Mine TR-122 Second Adequacy Review Memo <br />Rob, <br />As requested I have reviewed Bowie No. 2 Mine's (Bowie) TR-122 responses to the Divisions adequacy <br />letter dated December 21, 2020. The following comments were part of my original adequacy memo: <br />When reviewing the discussion regarding the East underdrain for the Gob Pile on proposed <br />Volume XI, page 7, it states the "rock drain" will be mostly 4 square feet and this is also shown <br />on typical sections with proposed maps associated with TR-122. However, Gob Pile #3 <br />Drying/Placement Location Operational Sedimentation Control Plan on proposed Volume XI, <br />page 4b shows a typical section of 2 ft. x I ft. Please have Bowie update the typical section on <br />proposed Volume XI, page 4b. <br />This item has been addressed with corrected typical sections found on Volume XI, page 4b. <br />The proposed location for the underdrain along the eastern side of the Gob Pile is located up <br />gradient of the pile running parallel to the Fire Mountain Canal. As stated on proposed Volume <br />XI, page 7, "The seepage from the Fire Mountain Canal does not have perceptible flow. <br />Therefore, even if the rock drain can only pass 1.2 gallons per minute, it is adequate for the <br />seepage from the Fire Mountain Canal. " While the proposed underdrain can handle potential <br />seepage from the Fire Mountain Canal, there is no discussion or information regarding the <br />additional flow from potential ground water intrusion. Additionally, it is unclear to the Division <br />on how the proposed underdrain location will intercept and convey potential groundwater that <br />may intrude the Gob Pile at lower elevations. Please provide the Division additional information <br />regarding the proposed underdrain and how it will handle and intercept potential groundwater. <br />Bowie No. 2 Mine TR-122 Memo <br />January 27, 2021 <br />COlO <br />1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http://mining.state.co.us I <br />Jared S. Polis, Governor I Dan Gibbs, Executive Director I Virginia Brannon, Director * 1876 <br />