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Ccn$irel~~:. ~ cr Facsimle <br />W. W. Wheeler and Associates, Inc. <br />Water Resources Engineers <br />August 13, 2003 <br />Ms. Maureen Jacoby <br />Banks and Gesso, LLC <br />720 Kipling Street, Suite 117 <br />Lakewood, CO 80215 <br />Re: # 648.01 - Guane//a Dam/Empire Pif <br />Adequacy Review Lefter <br />OMG Fi/e No. M-1977-534 AM-01 <br />Dear Maureen: <br />We are providing this letter to provide further clarification of a couple of <br />technical issues raised in the August 4, Division of Minerals and Geology IDMGI <br />adequacy review letter for the above-mentioned project. <br />Item 2 - In response to Allen Sorenson's July 29 Floodplain Impacts <br />memorandum, our analysis indicates that the flood levee will have no impact on the <br />floodplain because the flood levee is being constructed well above the 100-year <br />floodplain. <br />The purpose of the flood levee is to prevent the discharge of extreme West Fork <br />Clear Creek flood flows into Guanella Reservoir. More frequent flood flows will be <br />passed below the toe of the flood levee. As part of the design evaluations for Guanella <br />Dam, W. W. Wheeler and Associates, Inc. (Wheeler) developed a detailed HEC-RAS <br />water surface profile to evaluate flooding effects on the West Fork Clear Creek <br />floodplain adjacent to the flood levee. This model and the flood levee design was <br />reviewed and approved by the Colorado Office of the State Engineer, Dam Safety <br />Branch (SEOI. The flood levee was designed for the peak Probable Maximum Flood <br />(PMF) discharge of 43,300 cfs upstream of the confluence with West Fork Clear Creek <br />and Mad Creek, and 46,000 cfs downstream of the West Fork Clear Creek/Mad Creek <br />confluence. Mad Creek enters West Fork Clear Creek approximately 400 feet north of <br />the flood levee at about Station 20+00 of the flood levee. Our design also evaluated <br />the effects of a peak 100-year flood flow of 760 cfs above the Mad Creek confluence <br />and 844 cfs downstream of the Mad Creek confluence. A comparison of maximum <br />3700 South Inca Street Englewood, Colorado 80110 (303) 761-4130 fRX (303) 761-4804 <br />