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' STATE OF COLORADO Pickard D. Lamm, Governor DEPARTMENT OF NATURAL RESOURCES `pW R.t po IVISION OF WILDLIFE ~ ' Jack R. Grieb, Director ~ v0~ RECEIVED ~ ~ 6060 Broadway ~'y OF Denver, Colorado 80216 (825-1192) JUN '~J 19d3 ' June 26, 1983 ih1PWMAau COA! CO, ' Mr, Scott Jones ' Environmental Coordinator Snowmass Coal Company ' PO Box 980 Carbondale Colorado 81623 ' Dear Scott, ' I.have reviewed some additional literature concerning fish passage .and structures •: ~ ;which may impede fish passage, Some of the information applies to the Thompson "' Creek weirs so I thought I would pass the highlights along to you in this letter for ' Snowmass Coal Company's consideration, The information is from The McConauehv Rainbow... Life History and a Manaeement Plan for the North Platte River Valley by Rodney C, Van Velson (A Contribution of the Federal Aid in Sport Fish Restoration ' •"A pool of quiet water should be located immediately below any instream obstacle. this pool provides a resting area and a 'good start' for the fish to bypass the obstacle. A take-off pool below- any obstacle across the stream should be ly to 2 times deeper than the barrier is high, " ' "Any structure which creates a vertical drop over one foot should be avoided if possible," (If not possible several guidelines should be followedl. "All verticle drops over one foot should be investigated to make sure the water velocities and the water depth both in the ' pools below and over the structure are within the recommended guidelines, " "A minimum water depth of eight inches is necessary to insure unimpeded rainbow ' trout migrations, " Notches in the weirs should be designed to maintain the eight inches, "Maximum water velocities caused by any stream alteration should not exceed four ' feet per second, " I note in your letter of May 20, 1983, that the maximum velocities will be 2, 2 feet per second, ' "Construction activity should be limited to May through September, No construction should take place from October through April when rainbow trout migrations are under way, Every effort should be made during construction to keep debris and siltation ' at a minimum level, If a cement apron is necessary in an area immediately below .. . it should be placed below the stream grade. 1 • ' DEPARTMENT OF NATURAL RESOURCES, Harris Sherman, Executive Director • WILDLIFE COMMISSION, Michael Higbee, Chairman Wilbur Redden, Vice Chairman Sem Ceudilt, Secretary • Jean K. Tool, Member Vernon C. Williams, Member James Smith. Member Donald Fernandez, Member • Richard Divelbiss, Member