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999 <br />STATE OF CULUKAllU <br />MINED LAND RECLAMATION DIVISION <br />Department of Natural Resources <br />t3t3 Sherman St., Room 275 <br />Denver, CO 80203 <br />303 866-3567 <br />RA x: 303 8328106 <br />November 5, 1991 <br />OF ~~(p <br />`e~' ~ v <br />. ~~~ . <br />18'!6 <br />Roy Romer <br />Governor <br />Fretl R. Banta. <br />DIV~S~On Director <br />Mr. Brian Archer <br />Sun Coal Company <br />10200 West 44th Avenue, Suit 120 <br />Wheatridge, CO 80033 <br />p..,, . , <br />RE: Preliminary Adequacy Review, T~~v11, Meador s No. 1 Mine, Permit C-B1-029 <br />Dear Mr. Archer: <br />The Division has completed the preliminary adequacy review for Technical <br />Revision Number 11. The technical revision proposes an emergency spillway for <br />the Yampa River sediment pond. <br />The pond meets the criteria of Rule 4.05.6 for function and capacity, with one <br />exception. The design for the outfall of the emergency spillway is not <br />addressed. According to Rule 4.05.6(3)(d), the spillway must be "...designed <br />to safely pass the applicable design precipitation event...". According to <br />data cited in Mr. 5hearer's report of July 10, 1990, embankment slopes are 1.7 <br />to 3.5 feet horizontal = 1 foot vertical. This translates to slopes of 29 to <br />59 percent. While the size of riprap, .3 to .5 feet in a matrix of .05 feet <br />gravel, for the portion of the emergency spillway designed to have a slope of <br />4 percent is acceptable, this same riprap grading will not sustain discharge <br />flows predicted if the slope of the outfall is significantly greater than 4 <br />percent. <br />Rule 4.05.6(7) states that "...all supporting calculations, documents and <br />drawings used to establish the requirements of Rule 4.05.6(3) above shall be <br />included in the permit application". Therefore, Sun Coal Company, Inc. needs <br />to provide a design for the emergency spillway outfall including dimensions, <br />slopes, grading of riprap and supporting calculations. <br />Please contact me with any questions. <br />Sincerely, <br />~, <br />,,,~__ <br />Ca Mount <br />eclamation Specialist <br />CBM/gaw <br />9251E <br />