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<br /> ii iiiiiiiiiiiiiiiii <br />999 <br />STATE OF Cot OlP afyO w~ iiwini i• i n~nu ~~. v•.~•~•,~ <br />DEPAflTMENT OF NATURAL RESOURCES <br />D. Monte Pascoe. Executive Director <br />111 IN ED LAND RECLA~~ATIONt <br />423 Centennial Building, 13135herman Street <br />Denver, Colorado 80203 Tel. (30318663567 <br />David C. Shelton <br />Director <br />September 15, 1982 <br />Mr. Dennis Notovec <br />Colorado Department of Health <br />Waste Management Division <br />9210 E. llth Avenue <br />Denver, Colorado 80220 <br />Dear Mr. Notovec: <br />Per your request for comments on the report for the proposed silver ton Landfill, <br />I have the following comments: <br />1. Because this is proposed to occur within area of the operettor's <br />approved Mined Land Reclamation Board permit, it will require art amendment <br />to the permit to allow such use unless the operators wishes a with- <br />drawal of this area. I will contact Standard Metals and inform them <br />of this problem. <br />2. The toe of the existing tailings pond probably does not fall <br />within the 200-year floodplain of the Animas River. The expected <br />200-year discharge of the Animas River at Hermosa, north of Dur'ango~ <br />is Less than 30,000 cfs. Estimating the cross-sec tionaZ area and <br />expected velocity of tl~e Animas near the proposed site shows ttat <br />a discharge greater than 140,000 cfs would probably be required to <br />approach the toe of this debris. <br />3. We have no other data regarding the stability of this pond <br />other than the information provided by Fox's 1976 report. Fox <br />does question the stability of the tailings embankment if it <br />were increased over 6 feet above the existing height of the berm, <br />or if there were to be a 5+ feet rise in the ground water tab1= <br />at the toe. <br />Other things being equal, the density of trash compacted t•~ <br />1,000 lbs. x yrd.-3, 8-10 ft. thick, will produce less loading <br />than wet tailings with a density of 3,400-3,500 lbs. x yrd.-3 <br />raised 6 ft. in height. <br />The data is insufficient to indicate whether or not a S+ ftaet <br />rise in the ground water is probable. Typically, however, the <br />materials of alluvial fans and ground moraines are quite permeai~le <br />and transmissive (the report states the site was constructed on an <br />alluvial fan). AZ though it would be conjectural to predict a r(se <br />~~ <br />