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Flood Control Levee August 24, 1999 Page 1 <br />the levee is constructed of, and that of the. naturally occurring sand and gravel under it are not <br />conducive to piping. CTL /Thompson, Inc. concludes: <br />"In our- opinion, the seeps are notpresently affecting the sir-uctity-al in eg ty ofthe levee and <br />the in egfity of the levee will not be affected by the I 00-yew-flood event. --' "o <br />Based on the CTL Thompson investigations, It is the opin*on of the author of this report that the <br />seeps do not pose a problem for the levee, but it is recommended that they be monitored annually, <br />and after any major flood which may reach the levee, as part of the University's Operation and <br />Maintenance na Manual (Appendix 11). <br />EROSION slo TECTIOl <br />Over the years, large rock was installed by the gravel mining company gn the southern end (most <br />upstream part of the upstream reach) of the levee from about S CA station 1 3 5+00+1- to 148+5 0. The <br />. <br />nprap: <br />is poorly graded (missing the smaller rock sizes), <br />D <br />s not toed into the ground, and <br />it does not rest on a filter layer. <br />In other locations along the upstream reach, the erosion protection which existed in September 1997 <br />consisted of: <br />• a mixture of rock and grass; <br />* reasonable stand of grass; <br />0 a poor stand of grass; and <br />a no grass cover at all. <br />Expected base -flood velocities in the upstream reach were determined by L CVVE by interpreting <br />the output of the recreated USAGE G& C-2 computer model. They are summarized in the <br />table below, and have a range from 4 to 9.4 feet per second (fps). <br />"o Page 9, CTL /Thompson, Inc.'s August 6, 1999 report "Levee at Ice p a Farm Pit <br />Boulder, Colorado "' (Appendix 9. <br />Cl_ck) LEONARD RICE CONSULTING WATER ENGINEERS, INC. <br />