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<br />. <br /> <br />. <br /> <br />. <br /> <br />FLOODPLAIN REPORT - Tyra Tract D and Sawmill Gulch, Breckenridge, Colorado <br /> <br />Finally, the proposed building is generally situated higher in elevation then the adjacent Four <br /> <br />0' Clock Road, and significant drainage capacity will exist in the roadside swale, thus directing <br />any surface water at Four O'Clock Road away from the proposed building. <br /> <br />SUMMARY <br /> <br />This report provides technical information regarding the floodplain extents for Sawmill Gulch <br /> <br /> <br />between Four O'Clock Road and the upstream Town of Breckenridge limits. The gulch is <br /> <br /> <br />currently a FEMA-designated floodplain for a short portion of the reach upstream of Four <br /> <br /> <br />O'Clock Road. The FEMA floodplain, however, is invalid due to revised hydrology estimates <br /> <br /> <br />for the Town of Breckenridge and new, revised topography. <br /> <br />This report redefines the floodplain for Sawmill Gulch according to current methodology and <br /> <br /> <br />estimates of hydrology and according to the existing topography. This report also presents <br /> <br /> <br />details of split flow flooding that occurs from Sawmill Gulch under the currently projected <br /> <br /> <br />increased estimates of the 100-year flow peak rate. Plans and analyses are included for hydraulic <br /> <br /> <br />structures that are anticipated to collect the out-of-bank channel flows in order to direct them <br /> <br /> <br />safely around the building proposed for the Tyra Tract D parcel, just above Four O'Clock Road. <br /> <br /> <br />The proposed facilities and channel evaluation provide for safe handling of the 100-year peak <br /> <br /> <br />flow of Sawmill Gulch without flooding the proposed building and without increasing flood <br /> <br /> <br />depths in Sawmill Gulch. The proposed development provides for excess capacity (or safety <br /> <br /> <br />factors) should the gulch overflows exceed the predicted amount. <br /> <br /> <br />The design of the system is in conformance with the desires of the Town of Breckenridge and the <br />local FEMA administrator, and it is believed that the proposed structure and analyses are <br /> <br />consistent with FEMA requirements. <br /> <br />The theoretical 100-year peak flow is safely <br /> <br />accommodated and discharges to the same location in essentially the same way as would occur <br />as in pre-project conditions. <br /> <br />C:\97 1-055\0 1 Okab\drainage.rpt.doc <br />Updated: 5/1/98 @4:20PM <br /> <br />971-055.010 <br /> <br />Wright Water Enginee~, Inc. <br /> <br />Page 20 <br />