2012-03-07_REPORT - M1977342 - Laserfiche WebLink

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J W. W. Wheeler and Assoc., Inc. 1 Water Resources Engineers February 3, 2012 Mr. Miguel Hamarat Climax Molybdenum Company, Henderson Mine P. O. Box 68 Empire, CO 80438 Re: #1333.0 - Henderson Mill Tailing Pond Flood Storage Dear Miguel: As requested, we have evaluated the availability of flood storage capacity in the Henderson tailing impoundment using information from the fall 2011 pond survey. The survey of the beach and pool area was performed in October. Figure 1 is the pond contour map that was generated by Wheeler from the survey point data. The survey shows that the average dam crest elevation of No. 1 Dam at the end of the spigot deposition season is about 8860.3 feet, which is a 5.3 -foot increase from last year. The minimum elevation surveyed along the dam crest was 8857.84 feet, which occurred on 3 Dam. This information, as well as other characteristics of the pond, is summarized in the table in the upper right -hand corner of the pond map drawing. Table 1 is the elevation - capacity data for the impoundment that was generated from the fall 2011 contour map. Note that this data is representative of the pond at the time of the pool survey and changes continuously as additional tailing is deposited. One of the primary uses of the fall survey data is to evaluate the flood storage capacity conditions in the water system. As summarized on Figure 1, at the approximate time of the survey (end of October) there was a total system surcharge storage capacity of about 8,716 acre -feet in the system. This capacity includes both the tailing pond and East Branch Reservoir and is based on the minimum dam crest elevation of 8853.8 feet. The current flood storage requirement for the system is 3,582 acre -feet. This requirement is based on a hydrologic analysis performed by Wheeler and described in report titled 3700 South Inca Street Englewood, Colorado 80110 Phone (303) 761 -4130 Fax (303) 761 -2802