Laserfiche WebLink
COLORADO <br /> \/ Division of Reclamation, <br /> ® Mining and Safety <br /> Department of Natural Resources <br /> Date: July 20,2020 <br /> To: Peter Hays <br /> From: Zach Trujillo <br /> RE: Henderson Mine, DRMS File No.M-1977-342 <br /> TR-32 Adequacy Response Review <br /> Peter, <br /> I have reviewed Climax Molybdenum Company's 3 Dam, Phase II Buttress Design adequacy response to <br /> the Division's adequacy letter. Please see the following comments: <br /> Division Comment 1: <br /> Please have Henderson provide the additional stability analysis for the I Dam to ensure to the <br /> Division that long-term stability will remain if material is borrowed from the I Dam benches. <br /> Henderson/AECOM: <br /> There was a similar question posed during the review of the Phase I Buttress. The response <br /> provided below is excerpted from the 2018 TR-29 adequacy review response since it still applies. <br /> The original stability design of the I Dam was based on an overall design slope of 4:1 (horizontal <br /> to vertical). Steeper benches are constructed as part of normal operations as the impoundment <br /> steps upstream. These benches serve as access routes during operation until the following <br /> upstream step is constructed.A schematic showing the design slope and benches is provide in <br /> Figure 1. These benches are regularly grade as part of erosion and storm water control measures <br /> and are considered standard maintenance of the impoundment. The overall slope of 4:1 provides <br /> embankment stability and this slope is maintained during any bench regrading activities. <br /> Division: <br /> The material used from the 1 Dam as additional buttressing fill for the 3 Dam is in excess used <br /> for creating access for standard maintenance. The overall approved 1 Dam slope remains the <br /> same and the global stability should not be impacted with the use of this material. The Division's <br /> Comment 1 has been satisfied with no additional comments. <br /> Division Comment 2: <br /> Henderson Mine TR-32 Adequacy Response Review July 20,2020 <br /> 4F COlO <br /> I H o <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 * 187ra <br />