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Mr. Crellin Scott <br />July 30, 2002 <br />Paee 2 of 2 <br />3. SEDCAD 4, Taylor Pump Holding Pond TR-60 Emergency Spillway Freeboard <br />Evaluation. The Taylor Pump Holding Pond was as:;umed to be a Class B pond for a <br />TR-60 Emergency Spillway Freeboard Evaluation. The freeboard is adequate to <br />withstand the runoff from the 100-year. 6-hour rainfall plus 0.4 times the difference <br />between the PMP-6-hour and the 100-year, 6-hour amount. The SEDCAD 4 analysis <br />indicates the peak elevation will not overtop the embankment. <br />Based on the information provided by Colowryo Coal Company, the Taylor Pump <br />Holding Pond meets the (SCS) TR-60 classification criteria for a Class A Dam. The pond is <br />located in an agricultural area where failure is limited to damaging farm buildings, agricultural <br />]and. or county roads. However, the dam classification system considers several factors that are <br />objective (Earth Dams and Reservoirs, Technical Release No. 60, Page 1-t). For example, <br />consideration is given for existing and future development and the effect of failure on public <br />confidence. Future development in the mountains of Colorado is difficult to predict. Dams are <br />classified as Class B Dams if failure may damage isolated home:>, main highways or railroads or <br />interrttpt service of relatively important public utilities. <br />As a Class A structure, the Taylor Pump Holding Pond is not necessarily required to meet <br />the TR-60 Emergency Spillway Evaluation and the TR-60 Emergency Spillway Freeboard <br />Evaluation conditions (items 11 and 12 above). However, the SEDCAD 4 models demonstrate <br />that the Tay]or Pump Holding Pond meets the criteria for a Class B structure. <br />Sincerely, ;~ <br />Steve Linse. <br />Colorado P.E. 35009 <br />Project Engineer <br />SL:sb <br />Enclosures <br />cc: Dale Brown <br />File: 99-642 <br />• <br />W <br />wC Engineering <br />