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12 <br />25 lone '95 DMG (Sorenson) !u m COM, lac. (Hartley); adequacy of Application. Allows use of <br />a repaired Hazel A bulkhead and decant system to handle storm water as par[ of the <br />interim water management plan; requires a ttmctioaal water pump-back system to <br />empty Hazel A edit into t-pond; requires all tailings to be removed from the Hazel <br />A (but no deadline, not done as of 95111/5); requires Hazel A bulkhead be repaired and <br />water tight alt ]uly 12, 1995 (A brisk (i.e. > 1 GPM est.) leak exists as of 97/9/2, and ~ <br />has existed for momhs); regaires that only small amoums of water will be stored in <br />the Hazel A edit except during storm (presumably, this means thunderstorm) events. <br />Note: Experience has shown that, during extended wet spells such as are typical <br />from March through June in this area, the phreatic surface can and does intercept <br />the gxound surface nest the mouth of the Hazel A alit. This condition is <br />accompanied by rapid inflows in excess of ten GPM into this adit_ Under these <br />conditions, the edit cannot accept additional water from the tailings pond; in fact, brisk <br />pumping from the edit to the pond will be required in order to maintain azero-discharge <br />posture overall. Thin Las serious implications for the analysis given as part of item <br />3, pp 3-4 of this letter. <br />2ti lone '95 Staff (A. Sorenson) Memo to File regarding storage capacity Hader the Interim Tailing <br />Pond Configuration, Metter identifies roughly 57,500 cu. ft. of available storage <br />capacity with the approved interim two foot dam raise, and assuming a 14i upward edit <br />gradient and initially dry edit. (See, however, the COM, lac. estimate of 14 Dec. '95, <br />exhibit B, p. 3). <br />Note: Given the conditions described in the mte above, m more than 46,700 c~». ft. ~ <br />(57,463 - 10,763) of pond storage capacity is available, assuming the pond to be initially - <br />dry, an unlikely condition during the wet weather or Spring thaw implicit in these notes. <br />Further, assurttiag s 10 GPM average pumping tare to the pond required to balance edit <br />groundwater inflow (and thus prevent edit bulkhead overtopping) results in a 1,920 cu. <br />ft./day (10 x 60 x 24 / 7.5) inflow w the pond in addition to any volumes rtpotdag to <br />it due to precip. events in progress. Since such conditions could well persist over periods <br />of ten to thirty days, total edit coetribntions to the pond could amoant to 19,000 W <br />58,000 eu. ft. COME has no objective data upon which to base a calculation of the <br />probability of occurrrnce of thesce conditions, but artecdotally (based oa thirty four years' <br />trsidence in Gold Hill) can suggest that they represent roughly a ten (10) year event, the <br />most recent of which probably occurred in April -May -June of 1995. (Accompanied <br />by extensive illegal discharges to Cash Gulch) See also our discussion dated 3 July '95 <br />noted below. <br />28 June '95 Colorado Department of Public Health sod F~viranment Water Quality Control Division <br />(WQCD) (P. Nelson) ltr to COM, Inc. (T. Hartley) requesting application for a water <br />discharge permit alt September 1, 1495. <br /> <br /> <br />