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S 14Th OF COI ORAfJO uu nnNh U I~. vn n III IIIIIIIII I'11111 <br />DEPARTMENT OF NATIIRAL RESOURCES 1999 <br />D. Monte Pascoe, EKecui~~e Director <br />11'IINEU LANll RE(;LAMA'I'ION <br />423 Centennial8uilding, 1313 Sherman Street <br />Denver, Colorado 80203 Tel. (303) 839-3567 <br />David C. Shelton <br />Director <br />MEMORANDUM <br />T0: Mike Savage <br />FROM: R.A. Domingue <br />RE: TBM's Interim Application C-048-81 <br />DATE: February 27, 1981 <br />Immediate Hydrologic Concerns: <br />1. Loadout Facility Sediment Control Structures: Ponds 1 and 2 do not <br />have sufficient information for evaluation. We require information on de- <br />watering devices, principle and emergency spillways, design flows and <br />structure dimensions. This information must be submitted before we can <br />evaluate the proposal. <br />2. Culvert C-6: The statement in the October 7, 1980 amendment that an <br />18" culvert had been installed ir6incorrect. No culvert was in place <br />as of January 30, 1981. Culvert design diameter of 18" is acceptable only <br />if the entrance is carefully mitered to conform to the,~oad embankment. <br />The conveyance factor method used by TBM is an ina~C`l~rx~`te method for <br />determining culvert diameters as it ignores head losses due to entrance <br />configuration and friction losses which may occur in outlet controlled <br />pipes. TBM must ta.k~e these losses into account when designing culverts. <br />PnU 1n~~w+tar <br />3. Ditches 22-D5 and 22-D6: The method used by TBM to estimate peak flows <br />is still incorrect as it assumes that no watershed shape correction is <br />necessary. This is not the case. Using a correction factor for watershed <br />shape gives values approximately 20% larger for peak flows than estimates <br />generated by TBM. However, due to the use of 0.5 ft. of freeboard instead <br />of the required 0.3 ft. the ditches as designed will safely pass the 10 <br />year, 24 hour peak flow. <br />e~lsa ~'_~ s 5 P ~, <br /> <br />