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1.3 Objectives <br />The objective of this study is to provide site - specific PMP values based on analyses <br />of the most significant storms that have occurred over regions that are meteorologically <br />and geographically similar to the Climax Mine tailings ponds drainage basin. Historical <br />rainfall amounts associated with these events are adjusted using standard procedures for <br />PMP development. Using these rainfall amounts, PMP values are developed for the <br />Climax Mine tailings ponds drainage basin. <br />1.4 Approach <br />The approach for developing PMP values in this study follows the same procedures <br />that were used in the development of the NWS HMRs, as well as in other site - specific <br />PMP studies. The primary step in developing the PMP values is the identification of <br />extreme storms that are topographically and climatologically similar to the study basin. <br />Terrain features are examined to determine if major upwind barriers are present that <br />could reduce the amount of atmospheric moisture available to an extreme storm over the <br />basin. <br />Once the proper major storms are identified and the terrain surrounding the basin is <br />analyzed for significant features, the largest precipitation events are analyzed for storm <br />maximization, storm transpositioning over the study basin, and final rainfall adjustments. <br />This procedure increases the available atmospheric moisture for each of these extreme <br />storms using available dew point data. The result is an estimate of the maximum rainfall <br />that could have been produced by the storm at the location where it occurred. The <br />maximized storms are transpositioned into the Climax Mine tailings ponds drainage basin <br />to the extent supportable by similarity of topographic (terrain) and meteorological <br />conditions. Topographic effects are explicitly considered for storm moisture adjustments. <br />The final precipitation values are determined using procedures that provide both temporal <br />and spatial continuity of the rainfall events. <br />1.5 Basin Location and Description <br />The Climax Mine tailings ponds and drainage basin are located in central Colorado at <br />the eastern edge of what is referred to as the Western Slope region, just below the <br />ridgeline of the Continental Divide. The basin centroid is located at approximately 39.40 <br />degrees north latitude and 106.20 degrees west longitude. The drainage basin is located <br />northeast of the town of Leadville, and south of Copper Mountain Ski Resort at the <br />junction of Eagle, Lake, and Summit Counties. The basin slopes to the north, and is <br />surrounded on three sides by high mountain ridgelines and peaks with numerous <br />elevations exceeding 13,000 feet. The drainage basin is approximately 19.8 square miles <br />in area size. The three major tailings ponds in the overall Climax drainage basin are on <br />average approximately 11,100 feet above sea level. <br />13 <br />