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<br />area impacted by the severe rain and hail storm with measured <br />rainfall and duration of 1.0 inches of precipitation in 15 <br />minutes. The northern location is located at another <br />residence adjacent to the center of the mining area impacted <br />by the severe rain and hail storm with measured rainfall and <br />duration of 1.5 inches of precipitation in 25 minutes. <br />State Regulations and the design criteria accepted by DMG for <br />Colowyo temporary diversions require hydrologic sizing for the <br />10 year, 24 hour precipitation event, which for Colowyo, is <br />1.8 inches of precipitation in 24 hours. Colowyo actually <br />received 1.5 inches of precipitation in 0.42 hours (25 <br />minutes) which far exceeds the design criteria for the <br />temporary diversion. For additional comparison, the NOAA <br />Atlas 2, Volume III, Colorado, shows 1.35 inches of <br />precipitation for a 10 year, 6 hour event. Measurements <br />obtained by Colowyo showing 1.5 inches of precipitation in <br />' 0.42 hours surpasses both the 6 hour and 24 hour rainfall <br />events. The numbers are tabulated on Table 1. <br />This particular severe precipitation event was extremely <br />localized. The storm moved west to east and impacted a thin <br />corridor no wider than 2.5 miles wide. Storm duration was <br />extremely short but had great intensity. Thunder, lightning, <br />and hail accompanied the rainfall. <br />Therefore, factual data shows that the Colowyo minesite <br />experienced a severe precipitation event of magnitude greater <br />than the design criteria for temporary diversions required by <br />the regulations. <br />2. Prior DMG Inspection of the South Collection Ditch <br />On May 5, 1993, eleven (11) days prior to the severe <br />precipitation event of May 16, 1993, Steve Wathen and Larry <br />Routten of DMG performed a complete inspection of the Colowyo <br />minesite which included walking and inspecting the South <br />Collection Diversion in its entirety. A comment noted from <br />that inspection is that "As a whole, ditch performed well its <br />first runoff season". One minor breach in the entire ditch <br />had occurred, but was promptly corrected by the operator. <br />3. South Collection Diversion Ditch Sizing <br />SEDCAD sizing for the South Collection Ditch, obtained from <br />joint Colowyo and DMG modeling in accordance with the <br />regulations, shows a maximum design discharge of 6.99 cfs with <br />triangular ditch dimensions of 7.1 foot top width and 0.88 <br />foot depth. Colowyo's minimum as built design for the South <br />Collection Ditch results in a design discharge capacity of <br />25.49 cfs with triangular ditch dimensions of 10.4 foot top <br />width and 1.3 foot depth. For added safety, Colowyo <br />constructed the entire South Collection Ditch much larger than <br />the minimum as built design. High water flow depth measure- <br />