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<br />'. <br /> <br />... <br /> <br />STATE OF COLORADO <br /> <br />eOLOllADO WATER CONSERVATION BOARD <br />Dq).)rllllcnl uf N.llur.lllh'~our(e~ <br />H21 51 ,lit, \('tllpnni,ll Ruilding <br />11-1.J ~IH'rlllolll Sln'I'1 <br />Denver. Colorado 80203 <br />Phot1\': (303) 866~3441 <br /> <br /> <br />August 27, 1981 <br /> <br />Rkh.ud D. la1llm <br />(.OVNnor <br />I. Willi,unMlll'lll.tl(1 <br />Dire'llm <br />D.1vid Walker <br />Deputy Direclor <br /> <br />11 r. Sid Fox <br />Floodplain Management AdmInistrator <br />Environmental Health, Eagle County <br />P.O. flox 850 <br />Eagle, CO 81631 <br /> <br />Dear f1r, Fox: <br /> <br />The staff of the Colorado Water Conservation Board (CWCB) <br />has made a technical review of the floodplaIn map and supporting <br />hydraulic calculations (Hec-2) submitted by Mr. Larry Dezman for <br />the Eagle River opposite Peterson Ranch ncar Edwards, Colorado. <br />You will recall form Mr. Jencsok's letter of May 21, 1981, that <br />the CWCB feels the water surface profile and floodplain boundary <br />calculated by the developer's engineer are less than the true <br />100-year flood since both discharge and roughness coefficients <br />were est imated too low. <br /> <br />From our review of the additIonal information furnIshed by <br />Mr. Dezman, we have come to the fol lowIng conclusions: <br /> <br />1, Hydrology <br /> <br />The 100-year discharge of 4500 cfs which Initially <br />appeared too low is actually consistent with other <br />previously designated (Redcllff and Minturn) and <br />undesignated (Gypsum) studies on the Eagle River <br />prepared by Gingery Associates for the Federal Insurance <br />Administration (see attached graph). However, we are <br />not comfortable with these discharges downstream of <br />Minturn and we are not yet convinced that the records at <br />the gaging stations at Eagle and Gypsum have been <br />properly evaluated. Frequency-di~charg data pubLished <br />in TM-1 for these stations tends to Indicate a higher <br />discharge (6200 cfs) for Edwards. <br /> <br />In preparing the wal er surface profi Ie for Peterson <br />Ran c h , Mr. De z man i n fa c t plot t d the 95 - per c e n I. <br />confidence 1 imi I which corresponds to a discharge of <br />5600 cfs. In taking this conservative approach, he has <br />reduced th(' sign i ri Cdnc(' of hydro logy as an issue. The <br />difference in water surface profiLe due to hydroLogy Is <br />small and is estimdtf'd to be on the order of about 0,2 <br />feet for this redch. <br /> <br />COLORADO WATER CONSERVATION BOARD, Frederick V. Kroeger, Chairman <br />Robert A, Jackson, Vice Chairman. John R, Fetcher, Steamboat Springs <br />C,M, Furneaux, Walden' Floyd L, Getz, Monte Vista' Patrick A, Gormley, Grand Junction <br />Richard W, Johnston, Montrose' David W Robbins, Denver. Herbert H, Vandemoer, Sterling <br />