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iii iiiiiiiiiiiiiiii <br />999 <br />blue <br />cb~bon <br />company <br />~~~~~~ <br />0 CT ? 5 1989 <br />Ivl!PBr.t~ l.ii;~:;~ <br />blue ribbon coal company <br />p.o. box 1352 <br />palisade, Colorado 61526 <br />(303) 464-7951 <br />October 23, 1989 <br />Matthew S. Hayes <br />Mined Land Reclamation Division <br />215 Centennial Building <br />1313 Sherman Street <br />Denver, Colorado 80203-2273 <br />Dear Mr. Hayes: <br />Your letter to Blue Ribbon dated October 3rd asked three ques- <br />tions about the installation of the ADS culvert installed to <br />handle the run-off from the 100 year storm event from the top of <br />the mine bench. Following are my replies to your questions. <br />1. At the design flow of 18.7 cfs, the inlet would be <br />subject to about nine inches of head. <br />2. The inlet of the pipe has been fortified. <br />3. Flow in the 18-inch pipe will only be about 10 inches <br />deep when it is handling the 100 ,year event. The force e>t- <br />erted on the pipe due to this flow, assuming the pipe <br />deflects the water up to 45 degrees, is less than 1000 <br />pounds. The tensile strength of the pipe is 4500 psi or <br />about 17,000 pounds. The manufacturer does not have any in- <br />formation on the strength of the couplings, however I <br />believe the couplings will withstand the calculated forces. <br />The free end of the pipe has been further restrained near <br />its outlet in order to keep it in the ditch. <br />If you wish to discuss this further, please give me a call. <br />Sincerely, <br />"`~C~o~ <br />Jim Stover, P.E. <br />Chief Engineer <br />