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~ ~ III IIIIIIIIIIIII III C. VERKAIK & ASSOCIATES, Inc. ENGINEERS & ARCHIT~.CTS Novembe~~4, 19~J I ~k, P.E. Department of Mines & Geology 1313 Sherman Street, Room 215 Denver, CO 80203 Attention: Mr. Berhan Keffelew Subject: Parkdale Project at Tallahasse Creek Crossing Fremont County, Colorado Our Project No. 970807CD Dear Mr. Keffelew, James P. Verkaik, A.I.A. RECFIVEp NOV 13 1997 Divisinn ni rv+ineiais n i ~r.;i~,._, Following is a listing of the parameters we have used and briefly discussed by telephone for the Tallahassee Drainage Basin. 1. Storm durations and rainfall intensities: a. 100 year 24 hour event; rainfall intensity: 3.5 inches b. 10 year 24 event; rainfall intensity: 2.5 inches 2. The entire Tallahassee Drainage Basin has been broken down into 73 sub-basins. 3. The SCS Synthetic Curvilinear Unit method was used to establish Flood Hydrographs. 4. The hydrological soils classification used is between classification "A" & "B". 5. The soil cover conditions vary from poor to fair to areas well protected by vegetation. 6. The Muskingum Routing Methods was selected. Curve No. 71 has been used throughout the basin. The "x" coefficient varies from 0.18 to 0.45 depending upon the stream conditions. 7. Afrer establishing the total flow at the lower end of the basin, the equation Q = 0.4A°" is used to establish the area "A", velocity "V" and the factor "K" = L/V, where "L" is the length of the stream reach. - 8. The Tallahassee Creek Crossings will be designed to 10 year 24 hour storm. R / is-z3-~7 / 1 would appreciate any comments you may have. S aJKe~°' njer1~~^ i Sincerely, G. VERKAIK & ASSOCIATES, INC. ~._ Gerard Verkaik, President cc: Mitch Albert Ken Kclo ~ e~ ~.S o k z,.,~ t~,j fig StliD~ ~ ~~ % ~ ~ h e ~auJ P 7~ z ~r~yyef, ~y~~ /J 831 Royal Gorge Blvd., Suite 418 Canon City, Colorado 81212 Telephone (719) 275-2394 FAX (719) 275-5321