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C-s <br />COLORADO <br />Division of Reclamation, <br />Mining and Safety <br />Department of Natural Resources <br />Date: March 17, 2021 <br />To: Rob Zuber <br />From: Zach Trujillo <br />CC: Jason Musick, Michael Cunningham <br />RE: Bowie No. 2 Mine, DRMS File No. C-1996-083 <br />Waste Bank Review <br />'M <br />As requested, I have reviewed Bowie Resources, LLC's Bowie No. 2 Mine 2020 Yd Quarter Waste Bank <br />Inspection Report (Report) for compliance under Rules 4.09.1(11), 4.10.2, and 4.10.4. as well as your <br />question provided within your request. Overall, I agree with your review and have no concerns with the <br />provided Report. <br />To answer your question in comment 3d., in a general sense, there isn't a single specific value that would <br />indicate a stability problem. The values provided from the piezometer readings are used as an indicator <br />for a potential issue in combination with (in Bowie's case) inclinometer readings and visual inspections. <br />The piezometer values are compared to baseline information and expected normal fluctuations (seasonal). <br />Reviewing the last 2 — 3 years of piezometer values provided by Bowie, it appears that average <br />fluctuation range is around +/- 0.4 psi with some instances of up to +/- 0.9 psi. However, these changes <br />are consistent with typical seasonal snowmelt/rainfall. Ultimately, looking for a continual <br />increasing/decreasing trend or abnormal spikes beyond "normal" values for Bowie may indicate a <br />potential stability issue. <br />Hopefully this gives a little more insight and answers your question. Feel free to contact me if you have <br />any more questions or concerns. <br />Sincerely, <br />Zach Trujillo <br />Environmental Protection Specialist <br />(303) 866-3567 ext. 8164 <br />Zach.Trujillogstate.co.us <br />Bowie No. 2 Mine 2020 3rd Quarter Waste Bank Inspection Report Memo <br />March 17, 2021 <br />1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http://mining.state.co.us <br />Jared S. Polis, Governor I Dan Gibbs, Executive Director I Virginia Brannon, Director <br />