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Or,,', J.. S 1 lJ_ _, certain periods during the year. With Crystal Dam there will be a minimum flow of at least 200 second-feet in the river below the diversion tunnel for maintenance of the fish habitat. Slightly over 10 miles of transmission line to convey the power generated at Crystal Power plant have already been constructed. The line is of wood-pole type and extends from the Curecanti Substation near Cimarron, Colorado, to the canyon rim. This line cannot be seen from any public road nor the Black Canyon of the Gunnison Na.tional Monument. The section of ll5-kv transmission line from the canyon rim to the powerplant has not been constructed. Alternative methods of construction are being investigated at the present time, as well as the location of a transmission route to the powerplant. The first proposal is a wood pole line line running down a draw upstream from the dam. The alinement would not be visi- ble from the public area below the dam. The overhead line would extend to the crest of the dam where the conductors would be transferred to cable tunnels to the power plant at the base of the dam. The second alternative is an armored cable laid on the surface of the ground up the side of the canyon to the rim and then on to wood pole structures to the exist- ing line. The third possibility would require slant drilling of a cable tunnel from the top of the canyon rim down to the bottom of the canyon at the switchyard location and installing a cable in the tunnel for transmission of power. This would be the most costly alternative. When all details, economics, and environmental impact have been analyzed, a selection will be made. , The following are considered the primary impacts of construc- tion activity. In the diversion tunnel specifications, the contractor will be required to pass all waste and drainage water through a turbidity control plant or system to remove all suspended sediments before it is discharged into the river. The effectiveness of this procedure will be observed for pos- sible application under later contracts. Even with these pre- cautions it will be difficult to prevent additional sediment from entering the stream from construction activities such as aggregate processing, cofferdam construction, and excavation for channelization. Under the specifications, turbidity in- creases above the natural turbidities in the Gunnison River that are caused by construction activities must not exceed the limits of the Colorado Water Quality Standards and will be per- mitted only for the shortest practicable period required to complete such activities. Turbidity of the natural river has been measured regularly during the summer of 1971, and will continue to be measured in order to establish a base line upon which to make these determinations. Particularly during river 13