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Rebuttal Statements of Upper Yamps Conservancy District (no exhibits), Morrison Creek Metropolitan District
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Rebuttal Statements of Upper Yamps Conservancy District (no exhibits), Morrison Creek Metropolitan District
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Last modified
1/26/2010 4:42:06 PM
Creation date
8/11/2009 10:41:56 AM
Metadata
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Template:
Water Supply Protection
File Number
8230.21A2
Description
CWCB Hearing: Objectors' Prehearing Statements
State
CO
Basin
Yampa/White
Water Division
6
Author
Margaret O'Donnell, Robert G. Weiss, John Redmond, Mike Newmann, Jason Yanowitz, Chester Thorton
Title
Rebuttal Statements of Upper Yamps Conservancy District (no exhibits), Morrison Creek Metropolitan District
Water Supply Pro - Doc Type
Court Documents
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MAY-19-04 14:24 FROM-WEISS AND VAN SCOYK 970 879 6U58 T-286 P.029/033 F-562 <br />Of parlicular concem is the laelc of documentation presented to satisfy Section <br />26.163(c)(1), Standards for Floodways, that states; <br />"Ericroachmenrs, including fill, ftebV constracceion, <br />sitbsrantial imProvements nnd orher developrrients are prohibiteil, <br />zrnless cerlication by a regislered professiortal engineer is provided <br />demonsrrnting thut encroctcytrne?2FS shall not res2tlt in any increase in <br />flood levels dterirtg the occxerrence of the bczse flood discharge. " <br />Examining Attact-unent D oF Mr. Browning's memorandum, significant fill has <br />apparently been placecl wiUiin the flooclway. Additiflnally, not only the boat chutes, but <br />each of the habitat structures described in the 404 permic appl.ication represent fill williin <br />the floodway. Conducting an a.nalysis that meets the current standard of practice within <br />the engineering community requires a quantitative, not qualitativc, assessmenl of a <br />proposed projecc. This type of analysis is typically conducted prior ta the onsec of <br />constniction. In addition, requirements set forth in the National Flood Insurance <br />1'rogram dictate that anaiysis For fill within a iloodway be conducced in aecordance wit11 <br />standard engineering practice. <br />As a member of the Larimer Couniy Flood Review Board, stanciard engineering <br />practice ror Larimer County requires a numeric analysis compaiing FL-MA ilood plain <br />dclineations and waier surface elevations to those resulling from a proposed projecl. NIr. <br />Lacy's qualitative analysis based on ", ..numerous IIEC-RAS models of similar stntctures <br />in similar rivers..." falls significantly shoR of demonstrating an analysis chat mects the <br />typical requirement of standard of cngineering practice. <br />Preliminary examinaiion of the only quantitative hydraulic analysis provided <br />indicates that there is, in fact, an adverse impac[ on the 100-year water surface elevation <br />due eo the constructed boak chute structures. Compari.ng the ITEC-RAS resulcs ohtained <br />by the CWCB staff for the effective, corrected effcctive and proposed, or in this casE as <br />built, conditions indicate that the boat chute structures result in a rise in the 100-year <br />ilood elevation in the immediate vicinity of the structures. While the CWCB analysis <br />sho«ld Ue considared preliininary until the model can be calibrated witlz a field survey of <br />actual wacer surf.ace elevations, the impact of placing •fill in the t7oodway 11as been <br />demonstrated. In addicion, it is recommended that the polential impact oF incrEases in <br />water surface elevatiou upstream of "C-Hole" on Soda Creelc be examined <br />In addition to assessing the hydraulic performance of the boat chute and habiEat <br />stntcttires immediately following construetion, an assessment of long-tenn perfonnance <br />and overall aFfect on loeal hydraulies should be conducted. As observed during the site <br />visit, and shown in Figure I, a point bar is beginning to form upstream of the "C-Hole <br />near the confluence of the Yan-ipa River and Soda Creek. Sediment deposition witliin tlle <br />floodway will serve to providz ineffective now arca wi[hin the cross section and <br />ihere:Care affect the ilow velocity and water surface elevation. Not only will the local <br />hydraulics of the Yampa River be influenced, the potzntial for impacc to Soda Creek also <br />exists. Both the boat chutes and the habital structures, construcied downstream or the <br />cliuees, stiould be analyzed in an efforc to document the long-tenn effects and impacts oF <br />4
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