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j . , Allowable Dailv Flow Fluctuations - 5,000 cfs/24 hours for monthly release volumes less than 600,000 acre. feet, 6,000 cfs/24 hours for monthly release volumes of 600,000 to 800,000 acre-feet, and 8,000 cfs/24 hours for monthly release volumes over 8,000 acre-feet. .-~ Maximum Ramp Rates - 4,000 cfstbr when increasing, and 1,500 cfslhr when decreasing. Emerl1encv Exception Criteria - Normal powerplant operations will be altered temporarily to respond to emergencies. These changes in operations typically would be of short duration (usually less than 4 hours) and would be the result of emergencies at the dam or within the interconnected electrical system. Examples of system emergencies include: 1. Insufficient generating capacity 2. Transmission system: overload, voltage control, and frequency 3. System restoration , , 4. Humanitarian situations (search and rescue) .'r .. . :-) Flood Frequencv Reduction Measures - The frequency of unanticipated flood flows in excess of 45,000 cfs will be reduced to.no more than 1 year in 100 years as a long-term average.' This will be accomplished initially through the Annual Operating Plan 'process and eventually by raising the height of the spillway gates at Glen Canyon Dam 4.5 feet. Habitat Maintenance Flows - Habitat maintenance flows are high steady releases within powerplant capacity (33,200 cfs) not to exceed 14 days in March, although .other months will be considered under the AMP. Actual powerplant release capacity may be less than 33,200 cfs under low reservoir conditions. These flows will not be scheduled when projected storage in Lake Powell on January 1 is greater than 19,000,000 acre. feet, and typically would occur when annual releases are at or near the minimum objective release of 8,230,000 acre-feet. Habitat maintenance flows differ from beachlhabitat-building flows because they will be within powerplant capacity, and will occur nearly every year when the reservoir is low. Beacb/Habitat-Buildin~ Flows - These controlled floods will occur as described in the EIS (steady flows not to exceed 45,000 cfs, duration not to exceed 14 days, up-ramp rates not to exceed 4,000 cfslhr, and down-ramp rates not to exceed 1,500 cfslhr) except instead of conducting them in years in which Lake Powell storage is low on January 1, they will be accomplished by utilizing reservoir releases in excess of powerplant capacity required for dam safety purposes. Such releases are consistent with the 1956 Colorado River Storage Project Act, the 1968 Colorado River Basin Project Act, and the 1992 Grand Canyon Protection Act. . ,f7}, W Isl Bruce Babbin Secretary of the Interior February 24. 1997 . Date