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W. W. WHEELER <br /> & ASSOCIATES, INC. <br /> Water Resources Engineers WWW.WWWHEELER.COM <br /> March 7, 2017 <br /> Mr. Miguel Hamarat <br /> Climax Molybdenum Company, Henderson Mine <br /> 1746 County Road 202 <br /> Empire, CO 80438 <br /> Re: #1333.0- Henderson Mill <br /> TSF Flood Storage <br /> Dear Miguel: <br /> As requested, we have evaluated the availability of flood storage capacity in the Henderson <br /> tailing storage facility (TSF) using information from the spring and fall 2016 pond surveys. <br /> The spring survey of the beach and pool area was performed in June and the fall survey <br /> was performed in October. Figure 1 is the pond contour map that was generated by <br /> Wheeler from the fall survey point data. The survey shows that the average dam crest <br /> elevation of 1 Dam at the end of the spigot deposition season is about 8876.7 feet, which is <br /> a 1.2-foot increase from last year. The minimum elevation surveyed along the dam crest <br /> was 8875.41 feet. This information, as well as other characteristics of the TSF, is <br /> summarized in the table in the upper right-hand corner of the TSF map drawing. Table 1 <br /> and Figure 2 is the elevation-capacity data for the impoundment that was generated from <br /> the fall 2016 contour map. Note that this data is representative of the TSF at the time of the <br /> pool survey and changes continuously as additional tailing is deposited. <br /> One of the primary uses of the survey data is to evaluate the flood storage capacity <br /> conditions in the water system. As summarized on Figure 1, at the approximate time of the <br /> fall survey there was a total system surcharge storage capacity of about 9,951 acre-feet in <br /> the system. This capacity includes both the TSF and East Branch Reservoir and is based <br /> on 0.5 feet of residual freeboard below the minimum dam crest elevation of 8,875.41' and a <br /> water level of 8,862.4'. The flood storage requirement for the system is 3,582 acre-feet. <br /> This requirement is based on hydrologic modeling of the probable maximum precipitation <br /> (PMP) event. The available flood storage capacity in the system at the time of the survey <br /> 3700 S. INCA STREET I ENGLEWOOD, CO BO1 1 0-3405 <br /> 303-76 1 -41 30 1 FAX 303-76 1 -2602 <br />