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<br />FLOODPLAIN REPORT - Tyro Tract D and Sawmill Gulch, Breckenridge, Colorado <br />(I.I.AFT>> <br /> <br />Preliminary investigations associated with the development of the Tract D parcel indicated that <br />out-of-channel flooding may occur in Sawmill Gulch just upstream of Four O'Clock Road, <br />particularly when the revised hydrology estimates are applied to the stream flows. As part of the <br />planning process for the Tract D site, a detailed floodplain assessment (culminating in this <br />report) was initiated. Also underway is the FEMA restudy of the lower reaches of Sawmill <br />Gulch, the area between Four O'Clock Road and the confluence with the Blue River. Lower <br />Sawmill Gulch is being studied by FEe, who's submittal is currently being reviewed by FEMA <br />for its appropriateness in redefining the floodplain for the lower gulch. <br /> <br />The portion of Sawmill Gulch upstream of Four O'Clock Road is the focus of this report. We <br />utilized revised hydrology, new topography mapping, and site-specific additional topographic <br />survey data to define the 100-year floodplain in the vicinity of the Tyra Tract D site. At the <br />request of the Town of Breckenridge and FEMA, the current study by Wright Water Engineers <br />(WWE) was extended further upstream on Sawmill Gulch to the Town of Breckenridge <br />boundary, some 4,800 feet southwest of the southern limit of Tyra Tract D. The new town <br />topographic mapping was used for this extension. <br /> <br />As will be discussed later in this report, WWE confirmed that out-of-channel flooding will occur <br />under current estimates of 100-year flood peak events for Sawmill Gulch. The channel capacity <br />of Sawmill Gulch is inadequate to carry the current estimate of 248 cfs for the IOO-year flood. <br />This is caused both by limited channel capacity as well as the capacity of the culvert at Four <br />O'Clock Road. The out-of-bank flooding generally follows Four O'Clock Road in an easterly <br />direction and does not rejoin Sawmill Gulch. This split flow situation comprises the existing <br />condition, and the development proposal for the area continue this existing condition in the <br />future. Both FEMA and the Town of Breckenridge directed that this split flow condition be <br />maintained, and therefore we have complied with those requests. <br /> <br />RELA TED STUDIES <br /> <br />For reference purposes, several other studies or reports are important for the understanding and <br /> <br />the delineation of the Sawmill Gulch floodplain. The 1979 FIS, Flood Insurance Study, Town of <br /> <br />971-055.010 <br /> <br />Wright Water Engineers, Inc. <br /> <br />Page 3 <br />