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<br />. <br /> <br />. <br /> <br />Allowable nailv Flow Fluctuations- 5,000 cfs/24 hours for monthly release volumes less than <br />600,000 acre feet; 6,000 cfs/24 hours for monthly release volumes of 600,000 to 800,000 acre <br />feet; and 8,000 cfs/24 hours for monthly release volumes over 800,000 acre feet. <br /> <br />Maximum Ramo Rates- 4,000 cfslhour when increasing, and 1,500 cfslhour when decreasing, <br /> <br />. Emel'l!ency Exception Criteria-Normal powerplant operations will be altered temporarily to <br />respond to emergencies. These changes in operations typically would be of short duration <br />(usually less than '4 hours) and would be the result of emergencies at the dam or within the <br />intercoMected electrical system. Examples of system emergencies include: <br /> <br />. Insufficient generating capacity <br />· Transmission system: overload, voltage contro~ and frequency <br />· System restoration <br />· Humanitarian situations (search and rescue) <br /> <br />Flood 'reauency Reduction Measures- The frequency of unanticipated flood flows.in excess <br />of 45,000 cfs will be reduced to no more than 1 year in 100 years as a long-term average. This <br />will be accomplished initially through the Annual Operating Plan process and eventually by raising <br />the height of the spillway gates at Glen Canyon Dam 4.5 feet. <br /> <br />aabitat Maintenance Flows- Habitat maintenance flows are high, steady releases within <br />powerplant capacity (33,200 cfs) not to exceed 14 days in March, although other months will be <br />considered under the Adaptive Management Program. Actual powerplant release capacity may be <br />less 33,200 cfs under low reservoir conditions, These flows will not be scheduled when projected <br />storage in Lake Powell on January 1 is greater than 19,000,000 acre feet, and typically would <br />occur when annual releases are at or near the minimum objective release of 8,230,000 acre-feet, <br />Habitat maintenance flows differ from beachlhabitat-building flows because they will be within <br />powerplant capacity, and will occur nearly every year when the reservoir is low, <br /> <br />BeacbIHabitat-BuildiDl! F1ows- These controlled floods will occur as described in the EIS <br />(steady flow not to exceed 45,000 cfs, duration not to exceed 14 days, up-ramp rates not to <br />exceed 4,000 c:fsIhour, and down-ramp rates not to exceed 1,500 cfsIhour) except instead of <br />conducting them in years in which Lake Powell storage is low on January 1, they will be <br />accomplished by utilizing reservoir releases in excess of powerplant capacity required for dam <br />safety purposes. Such releases are consistent with the 1956 Colorado River Storage Project Act, <br />the 1968 Colorado River Basin Project Act, and the 1992 Grand Canyon Protection Act. <br /> <br />~ <br /> <br /> <br />FEB 2 4 I99T <br /> <br />Secretary of the Interior <br /> <br />Date <br />