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Report in Support of the Recertification of the <br />University of Colorado's Flood Control Levee <br />Page 19 <br />upper portion provides additional protection for floods larger than the 100 -year flood. The old <br />rip rap was to be replaced with 24 inches of a mixture of new Type M and H rip rap (UDFCD <br />standards) to achieve a minimum D50 of 15 inches. <br />Robert M. Sayre, P.L.S, laid out the line dividing the upper and lower portions using flood <br />elevations provided by LRE. Left Hand Excavating accomplished the rip rap maintenance <br />project for the University in March 2009. The finished rip rap is shown in Figure 32. It was <br />placed over a reach 210 feet longer that AMEC's Reach 2 (station 126 +50 to 135 +00, see Figure <br />33). While the finished result was not as large as specified by AMEC, it was larger than <br />required. AMEC concludes: <br />"Since the Dso for the newly placed rip rap (14.3 inches) is larger than that required <br />(12.8 inches) the erosion protection provides adequate protection against the water <br />velocities of the 100 year flood. " <br />"Based upon field inspections, both during and after construction, the levee embankment <br />erosion protection appears to have been placed in substantial conformance with the <br />Specifications and Drawings. <br />"This evaluation demonstrates the conformance of the levee erosion protection with the <br />applicable FEMA criteria for design and mapping of levees." ... "It has been <br />documented that the embankment meets this criteria. " <br />XII. INTERIOR DRAINAGE <br />The interior drainage facilities are shown on the Figure 34. The previous gravel mining <br />operation created a large excavation which is about 12 feet below the original grade. The Levee <br />was constructed on top of the natural ground along the south and east sides of the excavation. <br />The whole excavation has a change in grade of about 45 feet in elevation from the south to the <br />north. The majority of the site behind the Levee drains as overland flow, without being <br />intercepted by any specific drainage facility. The slope of the land is sufficient to move the <br />water through and off the site. At the present, there are only a few drainage facilities on the site. <br />All of them are operated by gravity; none have any mechanical or electrical components. When <br />the University develops the site in the future, it is probable that it will design and construct other <br />drainage features behind the Levee. <br />XII.1. Upstream Reach <br />All of the surface drainage from the area behind the upstream reach of Levee is generated from <br />rain falling on the immediate area, and on the adjacent area to the west. Some of the runoff from <br />the area to the west is intercepted in the South Boulder and bear Creek Ditch, which travels north <br />then northwest in this reach (see Figure 34). The majority of the area behind the upstream reach <br />of Levee drains northward as surface runoff without being intercepted by any drainage facility. <br />1 ° Ibid, page 8 (Appendix G). <br />11 Ibid, page 8 (Appendix G). <br />12 Ibid, pages 8 and 9 (Appendix G). <br />© Leonard Rice Engineers, Inc. June 2009 — 207FIP05 <br />