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Introduction The reclaimed channel design for the Nucla Mine (Area 1) was based on CMLRD regulations pertaining to diversions and conveyance of overland flow and ephemeral streams draining a watershed less than one square mile. The location of the reclaimed channel is shown on Exhibit 20-3 and depicted as profile K-K'. Please refer to Exhibit 20-5 for the profile of this channel. The postmining drainage channel is not in the same location as the premining channel.. This situation occurs as a result of taking advantage of the existing pit and ramp locations. The premining channel slope was 3.3 percent. The postmining channel slope will be 1.1 percent. Design The computer program SEDCAD Version 3.0 was used in the design of the postmining stream channel. Please refer to the end of this attachment for a complete printout of input and output. The design was based on the runoff resulting from the 10-year, 24-hour precipitation event. The peak flow was evaluated just upstream of existing Culvert C-3 (under Road A-A). The channel downstream from this culvert has already been constructed. The channel design also considered the possibility that some day the surrounding area could be irrigated. The channel could potentially have to handle irrigation flow plus the runoff from the 10-year, 24-hour precipitation event. During the 1989 irrigation season, the Second Park Irrigation Ditch, which is just upstream of the reclaimed channel, had an average flow of 8 mgd or approximately 12 cf s. Therefore, 12 cfs was added to the channel design as a baseflow condition. It should be noted that this is a very conservative approach due to the fact that the entire flow would have to be diverted to achieve this condition. The water rights situation would probably preclude this from ever happening. The following represents the main input parameters for the SEDCAD computer hydrology model. J