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Executive Summary <br />This report was prepared by Applied Weather Associates (AWA) for the Climax <br />Molybdenum Mine Company, in Climax, Colorado. The objective of this study is to <br />provide site - specific probable maximum precipitation (PMP) values for the Climax Mine <br />tailings ponds drainage basin located to the north - northeast of Leadville, north and west <br />of the Continental Divide. This study incorporated results from several previous studies <br />in Colorado including the Extreme Precipitation Study completed by the Colorado <br />Climate Center, the Site - Specific Probable Maximum Precipitation (PMP) Study of the <br />Muddy Creek Drainage Basin completed in 1995 by North American Weather <br />Consultants, and the Site - Specific Probable Maximum Precipitation (PMP) Study of the <br />Elkhead Drainage Basin completed in 1996 by North American Weather Consultants, as <br />well as the National Weather Services' (NWS) Hydrometeorological Report (HMR) <br />No.50 and No. 57. <br />Approach <br />A storm search was completed to identify all significant extreme rainfall events that <br />have occurred in the regions surrounding the Climax Mine tailings ponds drainage basin, <br />along the Western Slope of Colorado. The CCC Extreme Precipitation Study was <br />utilized as the primary reference along with NCDC rainfall records from local weather <br />stations. This task identified the most extreme rainfall events that have occurred over <br />locations that are climatically and topographically similar to the Climax Mine tailings <br />ponds basin. Once the most extreme events were identified, storm characteristics were <br />determined for each event. Transposition, elevation, and storm maximization factors <br />were identified for each of these storms. <br />6 <br />This study incorporated geographic information system (GIS) technology to not only <br />create detailed terrain models of the region surrounding the Climax Mine tailings ponds <br />drainage basin, but also to quantify certain aspects of the terrain, including storm <br />moisture inflow barriers. These terrain analyses provided accurate numerical results that <br />were incorporated directly into the storm maximization and transpositioning process. <br />Storm maximization plays a significant role in determining PMP values, both for <br />generalized and site - specific PMP studies. This study utilized previously analyzed dew <br />points from earlier generalized and site - specific studies. These studies, along with 12- <br />hour dew point maps from HMR 50, provided the storm representative dew points for <br />each storm, as well as storm elevations and moisture inflow vectors. In one storm <br />analysis, newer dew point data was analyzed to determine an update storm representative <br />dew point and inflow vectors. <br />