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COLORADO <br />Division of Reclamation, <br />Mining and Safety <br />Department of Natural Resources <br />Date: Decembter 21, 2020 <br />To: Rob Zuber <br />CC: Jason Musick <br />From: Zach Trujillo <br />RE: Bowie No. 2 Mine, DRMS File No. C-1982-056 <br />Bowie No. 2 Mine TR-122 Adequacy Review Memo <br />Rob, <br />As requested I have reviewed Bowie No. 2 Mine's (Bowie) TR-122, specifically the changes to the Bowie <br />Gob Pile 93 (Gob Pile) underdrain. In addition to the changes to the underdrain, TR-122 also proposes to <br />update the Bowie PAP with adjusted surface hydrology networking to the Gob Pile which is not part of <br />my review. Please include the following comments to Bowie TR-122 adequacy comments: <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 93 <br />Drying/Placement Location Operational Sedimentation Control Plan on proposed Volume XI, <br />page 4b shows a typical section of 2 ft. x 1 ft. Please have Bowie update the typical section on <br />proposed 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 />This concludes my review of Bowie's TR-122 and if you have any questions, feel free to contact me. <br />Sincerely, <br />Foidel Creek Mine TR-94 Memo <br />November 6, 2020 <br />pF COLO <br />H <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 ** <br />