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<br />CDM · <br /> <br />. <br /> <br />CAMP DRESSER & McKEE INC, <br /> <br />environmentsl engineers, scientists, <br />planners. & management consultants <br /> <br />Writer's Tower, Suite 1100 <br />1660 South Albion Sfreet Denver, Colorado 80222 <br />303758-4351 <br /> <br />October 16, 1981 <br /> <br />Dr. John Liou, FEMA <br />Building 710 <br />Denver Federal Center <br />Lakewood, CO 80225 <br /> <br />Iff) I;:; rr:/i72",~[-, , <br />j",(Y,-',!I;;',c:nr1lJ,II'N",r:::--.7 ' <br />I - .,' .../ ,-I r" <br />',,', j I' <br />- -, , <br />;' '1""_ - II J <br />'I l_'V ", L " J - <br />{, I. II J,_ 10i' 'I f' <br />'-J' '-',-,! '/1, <br />~_ '!jf <br />G ~~~;----, i i! I' <br />r,-" ,~~clR!1[]O I;/A:r"-~/c:::j <br />~. .' -1' '--" _, ,".,,''1 E/-; <br />'''1 - '~....... <br /> <br />Dear John: <br /> <br />Camp Dresser & McKee Inc. (COM) has comp1 eted the hydrologic anal yses for <br />the Douglas Creek, Mesa Basin, Peterson Field, Rockrimmon Basin, Templeton <br />Gap, Spring Creek, and Sand Creek basins, for the Colorado Springs Flood <br />I nsurance Study. <br /> <br />To predict the peak 10-, 50-, 100-, and 500-year flow rates for Douglas <br />Creek, Mesa Basin, Rockrimmon Basin, Templeton Gap, and Spring Creek, the <br />Soil Conservation Service, "Procedure for Determining Peak Flows in <br />Colorado," was util i zed. The development in each of the basins is <br />continuing at a constant rate and will be near full development at the time <br />of canp 1 eti on of the Flood I nsurance Study. It was therefore determi ned to <br />use future development conditions in the hydrologic analysis, as stated in <br />COM's letter of August 10, 1981. <br /> <br />For all basins a thorough search for existing up-to-date information was <br />performed by CDM. Current drainage basin studies were obtained fr~ the <br />City of Colorado Springs, a Flood Hazard Analysis was obtained from the <br />Soils Conservation Service (SCS), and a hydrologic analysis was obtained <br />which was prepared by the Corps of Engineers for Flood Insurance Studies in <br />E1 Paso County and Colorado Springs, Colorado. All reports were then field <br />checked by CDM to determine if conditions in each basin had changed to <br />warrant a new hydrologic analysis. <br /> <br />Below is a summary of the analysis for each flooding source. A detailed <br />summary of all flooding sources will be submitted with the review copy of <br />the Flood Insurance Study for Colorado Springs. <br /> <br />Dougl as Creek <br /> <br />All basin characteristics were obtained from the March, 1981, <br />"Douglas Creek Drainage Basin Study," by Leigh Whitehead Inc. <br />Only the 100-year discharge was calculated in this report. COM <br />calculated the 10- and 50-year frequencies using a 6-hour rainfall <br />obtained from the City of Colorado Springs 1979 "Determination of <br />Storm Runoff Criteria." The SOD-year rainfall was determined by <br />