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Report in Support of the Recertification of the <br />University of Colorado's Flood Control Levee <br />Page 3 <br />the Levee were raised as part of the University's ongoing maintenance program in April <br />2008, and May 2009. <br />• Based on flood velocities obtained from the 2 -D hydraulic modeling, the engineering <br />firm AMEC Earth and Environmental determined that the rip rap along a 640 -foot reach <br />of Levee needed to be replaced in order for the Levee to continue to meet the erosion - <br />resistance criteria of FEMA. The rip rap for that reach of the Levee was replaced as part <br />of the University's ongoing maintenance program in March 2009. <br />• It is the professional opinion of the author of this report that the upstream reach of the <br />Levee (about 4,970 feet from station 101 +00 to 150 +70) currently satisfies all of the <br />applicable criteria for FEMA recognition of levees, which are spelled out at 44 C.F.R. <br />Section 65.10 paragraphs (1) through (6). <br />III. LOCATION <br />The Levee is an existing flood control structure which is located in Section 9, of Township 1 <br />South, Range 70 West, of the 6th Principle Meridian, in Boulder County, Colorado. It is shown <br />on Figure 1 (USGS base map) and on Figure 2 (2002 aerial photograph). Colorado Highway 93 <br />is located to the west and south, US Highway 36 is located to the north, and South Boulder Creek <br />lies to the east. It sits on the natural flood plain of South Boulder Creek and it defines the <br />western edge of the existing base flood plain for a portion of its length. Figure 3 is a flood plain <br />information map (circa 1995) prepared by the UDFCD based on a flood hazard area delineation <br />report by G &O in 1986. Figure 4 is a portion of FEMA's 1990 Flood Insurance Rate Map <br />(FIRM) for Boulder, Community Panel Number 080024 0185 E. <br />The tributary area of South Boulder Creek is reported to be about 109 square miles at Eldorado <br />Springs, and 132 square miles at its confluence with Boulder Creek. The basin's boundary is <br />shown on Figures 5 and 6, which are taken from, "Climatology / Hydrology Report" prepared for <br />Boulder by HDR, CH2MHill, and DHI, February 6, 2007. <br />IV. REPORT SUPPORTING FEMA'S CERTIFICATION IN 2000 <br />The August 24, 1999 report previously submitted to FEMA by LRE contained a section that <br />describes how the Levee came to be, which entities gave permission for its construction, and <br />which agencies have historically considered it effective in controlling the 100 -year flood. The <br />reader is referred to the "Background and History" section the LRE August 24, 1999 report <br />(Appendix B) for the full discussion of those matters. The earlier LRE report also contained an <br />extensive discussion of the historical delineations of the 100 -year flood plain of South Boulder <br />Creek, and the engineering studies were undertaken to allow the Levee to be certified. <br />Certification of the upstream reach of Levee in 2000 was based on input from the following <br />engineering companies. Their reports were included as Appendices of the August 24, 1999 LRE <br />submittal, and they are included as Appendices B -8 through B -10 of this report. <br />• Evaluation of the freeboard was accomplished by LRE based on the difference in <br />elevation between the top of the Levee, from a 1998 as -built survey by Scott Cox and <br />Associates, Inc. (SCA) and the higher of the three flood profiles that existed at that time. <br />© Leonard Rice Engineers, Inc. June 2009 — 207F1P05 <br />