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<br />,- <br />III IIIIIIIIIIIII III <br />999 <br />U. S. Department of Labor Mine Sa~eri and Health Ad~nlmstrauon "" " <br />P.O. Box 25367 ~ ' <br />Denver, Colorado 80225-0367 <br />:;,' <br />March 1, 1991 Report No. D7175-W3059 <br />File: SUB-C77 <br />MEMORANDUbI FOR WILLIAM E. HOLGATE RECEIVE D <br />District Manager, District 9 <br />Coal Mine Safety and Health <br />Denver, Colorado MAR 0 4 1991 <br />Mined Land <br />THROUGH: JOHN L. ODELL ., `' Reclamation Division <br />Chief, Mine Wast and Construction Di~lsion <br />Safety and Health Technolog~~ Center <br />FROM: ]• HEN W. D;VI/W, P.E. <br />Civil Engineer, Mine Waste and Construction Division <br />SUBJECT: Preliminary Evaluation, Sedimentation Control Dam 006, <br />Seneca II, Hayden, Colorado, Peabody Coal Company <br />Subsequent to my memorandum of February 15, 1991, in which I stated, "... (it <br />appears that) the structure falls under MSHA jurisdiction with regard to height and <br />volume stored", Lee Smith, Glenwood Springs, field oflice supervisor, visited the site on <br />February 22. At the request of Mr. Smith, Peabody Senior Engineer, Ronald J. Gehrke, <br />P.E., provided a design report and four engineering drawings. The submittal was <br />received February 27 under a cover letter from Mr. Gehrke dated February 26, 1991. <br />The report addresses hydrologic and hydraulic design information and flood routing <br />calculations which shows that the embankment will not be overtopped during the design <br />event. As such, the designer contends that the open channel spillway with a crest at <br />7075.1 is properly designed. In addition, the cover letter clearly states that the <br />upstream toe (dam heal) is elevation 7068 and that reservoir volume below this <br />elevation is incised. Mr. Gehrke therefore concludes, since the dam height is less than <br />20 feet high (7075.1 - 7068 = 7.1) and storage volume is less than 20 acre-feet <br />(approximately 16 acre-feet calculated from area capacity curve furnished), the facility <br />does not fall under MSHA jurisdiction with regard to size. Both height and volume <br />were measured from the heal to the crest of the properly designed open channel. This <br />approach reflects the MESA Solicitor's Office opinion of September 1976 which has been <br />adopted into current MSHA guidelines. <br />The first step in evaluating the Company's allegation was to establish the heal elevation <br />of the embankment. To accomplish this end, I examined the four drawings provided <br />