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_lj- <br />• <br />TIPTON AND KALMBACH, INC. <br />04E =>Fa cEaTFS~.E~ITe Lc~ <br />151e .F.. FpnOE STF[!T <br />C LItiT04 Y/. NEMF Vi G. PR ESICENT <br />E R. N~GVfLL. E%EC. v~CE PFESIDE VT <br />R. F. a e:.po,yKE Pqf GAO rpT <br />•. J.CE'JTSC ~.TP EneUFE9 <br />J. H. TUF.4 Eq,cECgET:=Y <br />DENYER,COLORADO 80fl02 <br />FNOVE f3J]15~2 ~CGBI <br />May 14, 1981 <br />cneLS. <br />•gTIP - CEYV ER <br />TN%' <br />9109 Ji'25a.G <br />Mr. Richard Atkinson <br />Colon;yo Coal Company <br />5731 State Hichv,ny 13 <br />Meeker, Colcrcdo 81641 <br />Subject: Celo~r+yo Permit Application <br />Colorado Mined Land <br />Reclamation File No. C-019-81 <br />Decr M.r. Atkinson: <br />• <br />• <br />In occordcnce with your request v:e hove reviewed those portions of the Colcredo !.iirled <br />Land Reclametign's Adecuacy Review, Celo:ryo Coal Company - Colowyo Strip, April 10, <br />1981, that relcte to cur eaci.^.eeriny- work for Celo•.v}•o's Permit Acplic::tion. Our res=ars=s to <br />spacific points i,^. toe ~:=cuccy P,eview ore cs fclla•+rs: <br />. ~2.OJ p3 ~~~ F^. 5, I: ~DOL7nG?iEntS Crid DIVE'SIOr~S <br />1 . Culvert Designs:', the Adeeuccy P.eview stated that in using the Mclvieth <br />formula for peak flov+ estimates that incorrect rainfall intensities were used. <br />We have reviewed the peak flov+.calculctions for the 23 culverts, and in <br />consultation with Mr. P,ici~~cr~ A. Domingue, P,eclamaticn Specialist, Colorado <br />Alined Land Reclamation Divisian have concluded that the method outlined <br />in Colorado 41'ater Conservation board technical Manual No. 1 "Manual for <br />Estimating Flood Characteristics of Natural-Flow Streams in Coloreda" is a <br />more applicable method for determining culvert discharges for drainage arecs <br />of the size and loo~tion of these culverts. The discharges were then computed <br />for each of the culverts, and all cf the 18" to 48" diemeter culverts v+ere found to <br />be of adequate size to pcss the design 10-year frequency discharges, and the <br />120" diameter Taylor Creek culvert v+cs found to be adequate to pass its 20-year <br />design frequency discharge p Table 1 presents data on the culverts including <br />drainage area, discharge for 10-year or 20-year design frequency, culvert <br />diameter, inlet head required for the design discharge, cnd recommendation <br />for outlet riprap. Table 2 presents constructed culvert layout details. <br />2. USLE Calculations: The Adeauccy Revie•,v.asked for justification for use of the <br />method out fined in "Hydrolocy cnd Sedimentology of Surface Alined Lands" by <br />Haan and Earfield in determining the sediment delivery ratios. In the calculations <br />submitted v+ith the mine permit applicotion we had computed the delivery ratio <br />