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<br />HOWARD NEEDLES TAMMEN & BERGENDDFF
<br />
<br />August 26, 1976
<br />
<br />Mr. Mel Crompton
<br />U.S. Department of Housing and Urban Development
<br />Office of Procurement and Contracts (ACS)
<br />451 Seventh Street, Southwest, Room B-133 (711 Bldg.)
<br />Washington, D. C. 20410
<br />
<br />Re: Cont rac t No. H-4016
<br /> Hydrology
<br />Dea r Mr. Crompton:
<br />- \
<br />
<br />,
<br />The areas to be studied in detai 1 and by approximate methods in
<br />Douglas County, Colorado are shown in Attachment A (Part 1 - Tech-
<br />nical and Management Proposal). After research and study of various
<br />hydrologic methods, and discussion with representatives of HUD,
<br />Colorado Water Conservation Board, SCS, USGS, Corps of Engineers
<br />and Denver Urban Drainage and Flood Control District, we conclude
<br />the following:
<br />
<br />Oetai led Study:
<br />
<br />1. For the gaged streams, where suitable records exist, the peak
<br />flows for the 10, 50, 100 and 500 year floods will be computed
<br />by using the Log-Pearson Type I I I method as recommended by
<br />Flood Insurance Study Guidelines and Specifications, dated
<br />January 1976 and explained in Bulletin #17 of the Hydrology
<br />Committee dated March 1976.
<br />
<br />2. For non-gaged streams, the following methods have been considered
<br />in computation of 10, 50, 100 and 500 year flood peak discharges.
<br />
<br />A. Rational Method - Since this method is applicable for areas
<br />up to 200 acres, it cannot be used for thi s study.
<br />
<br />B. Colorado Urban Hydrograph Procedure (CUMP) - This method
<br />was developed to compute runoff in urban areas and the
<br />study areas in Douglas County, although developing, are
<br />mostly rural. Therefore, this method is not particularly
<br />suited to the study conditions. .
<br />
<br />Plllnning Engine",ing Architecturlll Service.
<br />
<br />1750 Gilpin Street, Denver, Color.do 80218, 303 322.9442 Robert W. Anzi.. Manager
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