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Report in Support of the Recertification of the <br />University of Colorado's Flood Control Levee <br />Page 6 <br />VI.1. Upstream Reach <br />The upstream reach now includes the upstream 4,970 feet of the Levee (station 101 +00 to <br />150 +70). This is about 400 feet longer than was included in the August 24, 1999 LRE report. <br />The reach includes about 4,100 feet where the Levee is in contact with and defines the limit of <br />the main flood plain of South Boulder Creek (station 146 +50 to 105 +50). Below (downstream <br />of) station 105 +50, the main flood plain falls away from the Levee. The Dry Creek Ditch No. 2 <br />follows along the outside of the Levee for another 400 feet. Boulder's consultant included a thin <br />ribbon of flood plain along this alignment of the ditch at the toe of the Levee in the 2007 version <br />of the flood plain (see Figures 7 through 9), but this was eliminated in the 2008 version of the <br />flood plain (see Figure 11). <br />This upstream reach of Levee ties into high ground on its upstream and downstream ends. The <br />new upstream reach extends from the Levee's upstream limit to a point below (downstream of) <br />where the Dry Creek Ditch No. 2 separates from the Levee to head northeast. See Figures 8 and <br />9. As mentioned above, the University (as part of its ongoing maintenance program) raised the <br />Levee to reestablish the required Levee freeboard in this area because of how the flood <br />elevations and flood plain was delineated in 2007. The author of this report believes that the <br />freeboard criteria are again satisfied for this reach. <br />At about station 149 +50, the South Boulder and Bear Creek Ditch passes through the Levee in a <br />30 -inch high by 48 -inch wide corrugated metal arch culvert. This culvert has been fitted with a <br />closure device that was designed by Love and Associates (see picture at Figure 14). It is the <br />opinion of the author of this report that this closure device satisfies the FEMA criteria at 44 <br />C.F.R. 65.10(2). The culvert is approximately 300 feet west of the base -flood plain limit. After <br />the ditch passes through the Levee, it continues in a northerly direction along the high ground on <br />the west side of the University's property (see Figure 2). During the base flood, the culvert <br />could convey the upstream bank -full capacity of the ditch through the Levee, or it could be <br />closed to prevent any flow through the Levee. There are no other "openings" in the Levee. <br />VI.2. Middle Reach <br />The middle reach of the Levee is now about 1,300 feet long, which is about 400 feet shorter than <br />identified in our August 24, 1999 report. For this middle reach, the base flood plain is not in <br />contact with the Levee (see Figure 9). The main flood plain falls away from the Levee at about <br />station 105 +00 (the old upstream limit of this reach) and the thin ribbon of flood plain (the Dry <br />Creek Ditch No. 2) that was included in the 2007 version of the flood plain falls away from the <br />Levee at about station 101 +00 (the new upstream limit of the middle reach). The main flood <br />again comes in contact with the Levee at about station 88 +00, the downstream limit of this <br />middle reach of Levee. <br />While this middle reach of Levee is described and included in this report, the base flood is <br />controlled by the land mass (i.e., the high ground) upon which this portion of the Levee sits. The <br />base flood plain is controlled by the naturally occurring high ground, and the Levee simply <br />provides an additional level of protection. <br />Since the flood plain does not come in contact with the Levee in this reach, it does not need to be <br />recognized by FEMA. We believe that the Levee does satisfy FEMA's criteria in the areas of <br />© Leonard Rice Engineers, Inc. June 2009 — 207FIP05 <br />