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:. <br />uiiiiiiiiiiiiiiiiii <br />STATE, OF COLON-~U <br />• ~~~~ -~/ Roy Romer, Governor /////~ <br />+F 96• ~/ <br />DEPARTMENT OF NATURAL RESOURCES i~~~ <br />MIND LAND RECLAMATION DIVISION !; ,i~'T~; :'~ <br />FRED R. BANTA, Dvector ~, U ?~,~r (i <br />January 23, 1989 <br />Mr. Richard Mills <br />Supervisor Environmental Affairs <br />Cyprus Empire Corporation <br />P.O. Box 68 <br />Craig, Colorado 81626 <br />Re: Drainage Control and Diversion Structures for Coal Waste Piles <br />Dear Mr. Mills: <br />During the 1988 oversight year, the Federal Office of Surface Mining initiated <br />a special study in reviewing Colorado's approved program. The subject of the <br />study was drainage and diversion ditch design for coal waste piles. During <br />this review it became apparent that drainage and diversion structures for some <br />waste piles were designed and constructed to control a 10 year-24 hour storm <br />event. Colorado regulations require that these types of structures be <br />designed and constructed to safely pass a 100 year-24 hour storm event. <br />Specifically, see Colorado Rules 4,10.3(2) and 4.09.2(7}, During our original <br />re vievr, the Division interpreted the regulations such that these structures <br />were treated as temporary diversions only required to pass a 10 year event. <br />These structures were constructed in accordance with the approved plan, <br />however, the Division's interpretation was in error. <br />In order to resolve this problem without the use of enforcement actions, the <br />Division has entered into an agreement with OSM, To ensure that all coal <br />waste piles within the state meet the 100 year requirement, the Division has <br />reviewed the designs for all approved waste piles. All designs must be in <br />compliance by April 30, 1989 with actual on the around modifications completed <br />by May 30, 19E°. Revision of designs by technical revision and on the ground <br />modifications by these dates will avoid the possibility of an enforcement <br />action being taken. <br />Enclosed is 'a~memo yrhich details the specific potential problems relal:ed to <br />your mines' refuse disposal area. <br />215 Centennial Building, 1313 Sherman Street Denver, Colorado BC203-2273 Tel. (303) 866-3567 <br />