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r <br /> l\�/ L W. \, v. Wheeler <br /> ' '` 1 & Associates , Inc . <br /> February 1, 2012 <br /> Ray Tenney, Senior Water Resources Engineer <br /> Colorado River District <br /> P.O. Box 1120 <br /> Glenwood Springs, CO 81602 <br /> Re: 1794.00— Proposal for Dam-failure Inundation Mapping Update for <br /> Ritschard Dam <br /> Dear Ray: <br /> Per your request, W. W. Wheeler and Associates, Inc. (Wheeler) is pleased to submit <br /> this proposal to update the dam-failure inundation mapping for Ritschard Dam. We <br /> understand that Dam Safety Branch of the Colorado Office of the State Engineer (SEO) <br /> has requested that the existing inundation mapping be updated to be consistent with the <br /> SEO's latest guidelines. Our firm has recently prepared numerous similar dam-failure <br /> inundation maps for Emergency Action Plans (EAPs) that have been reviewed and <br /> accepted by the SEO. This includes inundation mapping for Williams Fork Dam and <br /> Dillon Dam which drain into the Colorado River in some of the same areas that would be <br /> inundated by a dam-failure of Ritschard Dam. <br /> Scope of Work <br /> Our work will be initiated with a meeting at your office to collect key engineering data <br /> and drawings about the dam from your files. As we discussed previously, we propose to <br /> perform the dam-failure inundation mapping based on a worst case scenario that <br /> assumes dam failure at the maximum reservoir water surface associated with routing the <br /> Probable Maximum Flood (PMF) through the reservoir. It is our experience that this <br /> scenario is more useful to emergency planners than a simulated a sunny-day failure that <br /> is suggested in the SEO's guidelines. Regardless, we would discuss which scenario <br /> should be modeled with both your office and the SEO and model only one failure <br /> condition, either the PMF-plus-breach or the sunny-day scenario. The inundation limits <br /> and summary data will be shown for only the selected dam-failure scenario. The <br /> inundation mapping would extend downstream to a point on the Colorado River that <br /> 3700 South Inca Street Englewood, Colorado 80110 Phone (303) 761-4130 Fax (303) 761-2802 <br />