2011-06-30_REVISION - M1981302 (12)

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Flood Control Levee August 24, 1999 Page Taggart flood profiles. The actual freeboard for the n*prap is summarized ed on Table ; at several locations, only 1. 8 feet of freeboard was achieved over the Taggart profile. Freeboard for the designed ri rap over the base -flood profile ranges from 2.0 to 7.5 feet. . f~ib rrnesh reinforced concrete cutoff wall was constructed at the toe of the South- Boulder - Creek side of the levee from SCA station 106+00 to 135+30. It extends to a depth of three feet below the elevation of the bottom of Dry Creek Ditch No. 23 which parallels the levee. No specifically - constructed Filter layer is required. The typical section of the levee and -its erosion protection are shown on the Ayres' as- constructed drawm* gs. Certifications for the design and installation of the ri rap and cutoff wall are included with Appendix 10. CROSS SE TI OI The cross section of the levee is a minimum often feet vide at the top, with a 0r�Nr_n_urn of :1 side slopes on the interior and outside faces. The top vidth ofthe upstream reach averages 16.8 feet, with a range of from ten to 23 feet. The side slopes average 3.9:1 on the outside slope and 3.5:1 on the *Inside slope between S A stations 105+00 and 150+70. The cross sections for the upstream portion of the upstream reach (station 1 3 5+00 to 1 50+70), and for the middle and downstream reaches, are shown on a 9/27/96 SCA drawing (Appendix , For the remah f ng portion. of the upstream reach between S CA stations 104 +0o and 1 +03 the final cross sections are shown on the 1998 Ayres as- built drawings (Appendix 10. INTERIOR DRAINAGE The interior drainage facilities are shown on the Site Flan Map Figure 2 (and Appendix . Gravel mining has created a large excavation north and west of the levee, which is about 12 feet below the original grade. The whole site, however, falls about 45 feet in elevation from the south to the north. The majority of the site behind the levee drains as overland flow, without being intercepted by any specific drainage facility. The slope of the land is sufficient to move the water through and offthe site. At the present, there are only a few drainage facilities on the site. All of them are operated by gravity; none have any mechanical or electrical components. When the University develops the site in the future, it is probable that it Will design and construct other drainage features behind the levee. J stir am Reach All of the surface drainage from the area behind the upstream reach of levee is generated from rain falling on the immediate area, and on the adjacent area to the vest. The majority of the area behind the upstream reach of levee drains northward as surface runoff without being intercepted by any drainage facilities. A 1.9 -acre pond located near the middle of the site intercepts a small amount of LEONARD RICE CONSULTING WATER ENGINEER S9 INC.