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Alsmos~t RTVERKEEPERS~ <br />P.O. Box 75~, I,a Jara, CO 81140 <br />~19-Z74-4298 <br />June 17, 2008 <br />Linda Bfissi/Rick Brown <br />CWCB <br />1313 Sh~:rtnan St. <br />~ r.~ ~ <br />D~nver~ CO 80203 <br />RE: Fio.al Report for Rio Grande Bxein Rouedtable twnding <br />T'~e AJamo~a River Instream Flow Project: Tercace Reservoir Hydrologac Modeling, Site <br />S~uv~- ~~nd Mapping which was funded by the Rio Grande Basin Roun~table included <br />t~e follawing task: <br />Task A PMFA~ealys~s <br />product; Probable Maximum Fiood data for Terrace Reservoir spillway design and <br />reatorat:iota. EPAT software will be used tu estimatc Extr+eme Precipitation data ae an <br />iaput to the HEC-1 flood hydrology model, which will estimate the Pxobable Maximum <br />~lood. <br />The it~t,rnt was to develop en assessment of the PMP ~nd PMF valwes for Terrac~ <br />Reserv~~ir by using the new EPAT model. The project committse expected that the PMP <br />and PN[F values would be lower than the ones previously estimated by app~ying the new <br />tools available for the State of Colorado, including EPAT. However, the results ubtau-ed <br />did not shavv a sig~ificeat chsage in the values obtained previously. 'I~erefore, the <br />commi~ttee i~as apted to move ~orward with an Tracremental Damage Analysis (ll~A) for <br />Terrace; Reservoir~ rather t~sn formally subztutting the results to the SEO. Funding for <br />the TDA is financed by the Naiural Resource Damage Settlemont. <br />We vvere very disappointed by the PMF results and the i.mplications of construc9ing ffi <br />54.5 million spillway w~te outside tt~e Insheam F~ow Project's budget. The initial <br />budget for the spillway wes des,i~naLed fQr $2 million. The EPAT tool for this basin <br />proved pr~oblematic. Heing the first applicants to use this new taol, there were ~any <br />"bugs" in the saftware that needed to be tesolved with the State's contractor during the <br />course of the project_ This greatly affected the budget, schedule and tb~e progress. <br />The EF'AT B~in enalysis results are attached. <br />Ta~~r ~~ - Slte 5umy aMd 1~lapp~ieg <br />Produc~t: Descriptions of ground control points used for establishing swrvey con~ol, and <br />4opogn~phic mappi,ng in AutoCad or MicmStation digital format. <br />