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W. W. WHEELER <br /> & ASSOCIATES, INC. <br /> Water Resources Engineers WWW.WWWHEELER.COM <br /> January 29, 2016 <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 /> Tailing Pond Flood Storage <br /> Dear Miguel: <br /> As requested, we have evaluated the availability of flood storage capacity in the Henderson <br /> tailing impoundment using information from the spring and fall 2015 pond surveys. The <br /> spring survey of the beach and pool area was performed in May and the fall survey was <br /> performed in October. Figure 1 is the pond contour map that was generated by Wheeler <br /> from the fall survey point data. The survey shows that the average dam crest elevation of 1 <br /> Dam at the end of the spigot deposition season is about 8875.5 feet, which is a 2.7-foot <br /> increase from last year. The minimum elevation surveyed along the dam crest was 8874.24 <br /> feet. This information, as well as other characteristics of the pond, is summarized in the <br /> table in the upper right-hand corner of the pond map drawing. Table 1 and Figure 2 is the <br /> elevation-capacity data for the impoundment that was generated from the fall 2015 contour <br /> map. Note that this data is representative of the pond at the time of the pool survey and <br /> 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 11,869 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 8,874.24' and a <br /> water level of 8,856.29'. 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 -2BO2 <br />