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<br />- <br /> <br />COLORADO WATER CONSERVATION BOARD <br /> <br />Department of Natural Resources <br /> <br />721 State Centennial Building <br />1313 Sherman Street <br />Denver, Colorado 80203 <br />Phone: (303) 866-3441 <br /> <br />STATE OF COLORI\DO <br />~ <br /> <br />Richard D.lamm <br />Governor <br /> <br />J. William McDonald <br />Director <br /> <br />March 26, 1986 <br /> <br />David W. Walker <br />Deputy Director <br /> <br />Mr. Michael S. Dungan <br />Muller Engineering Company, Inc. <br />Consulting Engineers <br />7000 West 14th Avenue <br />Lakewood, CO 80215 <br /> <br />""'~-, <br />. ":':<:11'1", <br />., ~.. <br />'1".v . "'I <br />. ~, APp n n 19 <br />, 8 L,.. ' 86 .'~. <br />Mll11.ER ::;;;'-" 'c :1_ tJ; <br />U/tlNG CO., /Ne <br /> <br />Dear Mr. Dungan: <br /> <br />I have completed my review of the Preliminary Design "Phase <br />I," Rio Grande Levee Improvements, Alamosa, Colorado as <br />prepared by Muller Engineering Company, Inc. <br /> <br />It appears that Chen & Associates, - Muller's <br />Sub-Contractor - performed a complete analysis of the materials <br />and sub-surface formations; however, their design <br />recommendations are brief and lack specifics. They did not <br />address seepage flow rates or control measures. <br /> <br />My specific comments are denoted in red in the report which <br />is attached for your consideration. I find no problem with the <br />general plan lay-out and design concepts. Two comments <br />regarding estimated total project cost, first, I feel that a <br />unit cost of $20 per ton for rock riprap is more commonly used, <br />and secondly, it is not clear how riprap requirements were <br />calculated. <br /> <br />In the hydraulics analysis. it is not clear why a Manning <br />"n" of 0.012 was used. In the reconnaissance report, Manning <br />"n's" of n = 0.035 and n = 0.030 were used for the hydraulic <br />routings. In their design report. Manning's "n's" of 0.030 and <br />0.012 were used. I request a review of the flow velocities <br />used for establishing the riprap requirements. <br /> <br />0530E <br /> <br />David W. Robbins, Chairman - James S. lochhead, Vice Chairman <br />Michael K. Higbee. James P. Johnson, Richard W. Johnston Jr., David E. Meyring. Susan M. S.mfilippo, David H. Smith, Raymond 8. Wright <br />