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~~~.;~~ III January 9, 1996 rrcr~l\/F~~ JAN 10 1991; Mr. Allen C. Sorenson Department of Natural Resources 1313 Sherman Street Rm. 215 Denver, CO 80203 Re: Water Storage Capac;ty fer,l~lodr~~ed Tailings Pond and Hazel A Permit No. M-94-117, COMInc: Al: Division of ~wmerais 8 Geo~oyy The following chart and table were developed Gom the tailings pond survey that was completed on December 21, 1995. The pond points were shot using a theodolite and stadia, shooting level shots. A map of the tailings pond showing the contours and survey shot locations is attached. The total volume above the current surface level of the tailings and ice is 0.52 ace-feet to the decant risers and 0.76 acre-feet to the low point on the embankmrnt. There is also an estimated volume of 0.12 acre-feet of water storage volume from the low point of the tailings to the top of the ice. With this extra 0.12acre-feet of capacity, the dry pond volume is 0.64 acre-feet to the riser inlet and 0.88 acre feet to the top of the embankmrnt. These aze two reasons that the capacity of the pond is lower than the estimated volume shown in my letter of December 18, 1995. 1) The pond azea is smaller than the area of Matit Stern's original pond design map. 2) After my survey of the embankment last summer to make slue that there was two feet of fill added to the embenlanent, additional work on the embenlmtent was done to add additional material on the downstream side of the embankment The additional material was placer! to allow erc•.:glt room for fence post installation after an anchor trench was made. The additional equipment travel on the emberilaarnt probably compacted the material more and deceased the effective height of the fill. My December 18 letter to you calculated the stonnwater nmoff into the pond from the 100-year, 24 hour storm to be 0.45 acre-feet. The survey shows that the incremental storage capacity currently in the pond to the decant risers (0.52 acre-feet) can contain this storm event with more than a l 5°io surplus. Your permit adequacy letter dated June 25, 1995 (Item 2), said that this storage capacity would be acceptable prior to construction of the penttanent dam raise with continuing use of the Haul A decant system. Below, I have calculated the curent storage capacity behind the Hazel A bulkhead to be an additional 0.148 acre-feet. I also estitnete that the water and ice in the pond occupy 0.12 acre-feet. Therefore, the total dry capacity of the pond and the Hazel A storage is 0.788 ace-feet to the decant risers, compared to 0.45 acre-feet runoff from the 100-year, 24hour storm. illlllliiiill 111 ., "~