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I I I I I I URS AN INTERNATIONAL PROFESSIONAL SERVICES ORGANIZATION URS COMPANY 3955 EAST EXPOSITION AVENUE DENVER. COLORADO 80209 TEL (3031 744-1861 NEW YORK SAN FRANCISCO WASHINGTON. 0 C DALLAS SEATTLE DENVER KANSAS CITY HONOLULU NEW ORlE:ANS SMJ ~Al 100 HONG KONG BOLiVIA December 19, 1977 Mr. l. Scott Tucker Executive Director Urban Drainage and Flood Control District 2480 West 26th Avenue, Suite 156B Denver, Colorado 80211 ,I Re: Sloans lake Basin Major Drainageway Planning URS No. 6007 I I I I 1 I I I I I I 1 Dear Mr. Tucker: Transmitted herewith is the Phase B Report of the Sloans lake Major Drainageway Planning Study. The submittal of this report represents completion of the Phase B portion of our original Agreement dated January 5, 1976. Our conclusions and recommendations are summarized as follows: Purpose The purpose of the Drainage Master Plan for the Sloans lake Basin was to: (1) Delineate drainage problems within the Basin, (2) Evaluate solutions to these problems, (3) Determine the best alter- native plan, and (4) Prepare preliminary plans for the selected alternative. The information prepared will be used for flood plain regulation and planning for future development. General Information The Basin lies generally between Colfax and 32nd Avenues and extends westerly from the South Platte River to Garrison Street in lakewood. The total Basin area is 5.475 square miles, which is generally appor- tioned to the local governmental entities included in the Basin as fo 11 ows : City of Denver City of Edgewater City of lakewood City of Wheat Ridge 2.688 0.491 1.086 1.210 (includes Crown Hill Cemetery) URS AN INTERNATIONAL PROFESSIONAL SERVICES ORGANIZATION The total study area is divided into 17 Sub-basins which include a direct flow area located in the City of Denver that drains directly into the South Platte River. Since the Basin is heavily urbanized, the major drainageways are not clearly identifiable. Recommended Alternative from Phase A The Phase A Study was reviewed and the recommendation developed there- in was found to be the best solution to the drainage and flood con- trol problems within the basin. The recommended plan for the Sloans lake Basin is a combination of detention facilities, underground con- duit (designed for 5-year flood frequency) and open grass lined channel (des i gned for 25-year flood frequency). Master Plan Drawings Master plan drawings were prepared on mylar plan and profile sheets at a horizontal scale of I" = 100' and a vertical scale of I" = 5'. The drawings are presented in the report at a reduced scale. Information shown on the drawings includes (I) Flood boundaries for the IOO-year storm under existing channel conditions and improved channel conditions, (2) Typical sections, (3) Right-of-way requirements,-(4) Existing utilities, (5) Water surface profiles, and (6) location and profile of proposed improvements. Improvement Costs A detailed cost estimate of the improvements for the selected alternative plan is presented in the report. The total capital cost of these im- provements is estimated to be $4,333,000. (1977 dollars) Recommendat ions The alternative plan selected for Sloans lake Basin improvements will re- duce the flood potential and we recommend that it be implemented. While the costs of the recommended improvements are considerable, they are not unexpected since problems within the basin were allowed to accumulate and compound over many years. Immediate action is required. Further delays will only lead to greater hazards and increases in costs of the recommended improvements.