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<br /> FLOODPLAIN REPORT - Tyra Tract 0 and Sawmill Gulch, Breckenridge, Colorado <br />e SECTION FLOW IN CFS WATER SURFACE ELEVATION <br /> 69 248 9882.8 <br /> 70 248 9896.7 <br /> 70.5 248 9914.5 <br /> 71 248 9922.5 <br /> 72 248 9932.4 <br /> 73 248 9943.0 <br /> 74 248 9954.6 <br /> The floodplain mapping on Plate I is generally consistent with the pattern of flooding previously <br /> estimated in the 1988 Master Plan work by FLO Engineering. A detailed comparison of the <br /> floodplain estimates was not performed. <br /> Proposed Conditions Model- Tract D Reach <br />e Plate 2 presents the proposed floodplain for Tyra Tract D. Sheets I through 4 are <br /> permitting/design drawings for the major drainage facilities related to Tyra Tract D. Sheet I <br /> presents the floodplain of Sawmill Gulch across the Tract D site in the existing (pre-project) <br /> condition. Sheets 2, 3 and 4 present the facilities proposed for Tract D. Essentially, there are no <br /> changes to the main channel floodplain; only the overbank spills are modified. In the proposed <br /> condition, the main channel of Sawmill Gulch and its water quality and drainage setback are <br /> . <br /> respected and little or no construction is proposed. Simply, the proposed facilities that affect <br /> flows of Sawmill Gulch are merely collection points for the already identified out-of-bank flows <br /> that occur in the existing condition. These out-of-bank flows will be collected above and re- <br /> directed around the proposed building through a combination of concrete retaining walls and a <br /> 48-inch diameter culvert with an outlet structure. A lower collection system will capture the <br /> flooding that is anticipated to occur at Four O'Clock Road and will convey that water via a 30- <br /> inch diameter pipe to a location consistent with the historic flooding on Four O'Clock Road near <br />e the project eastern boundary. At that point, it will be joined by the flows from the 48-inch pipe <br /> 971-055.010 Wright Water Enginee~, Inc. Page 13 <br />