Bureau of Reclamation:

An Assessment of the Environmental Impact Statement on the Operations of the Glen Canyon Dam

RCED-97-12: Published: Oct 2, 1996. Publicly Released: Oct 2, 1996.

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Pursuant to a legislative requirement, GAO evaluated the Bureau of Reclamation's final environmental impact statement (EIS) on the operations of the Glen Canyon Dam, focusing on: (1) whether the Bureau's determination of the impact of various operating alternatives on selected resources was reasonable; and (2) key interested parties' concerns about the final impact statement.

GAO found that: (1) in general, Reclamation used appropriate methodologies and the best available information in determining the potential impact of the dam's various flow alternatives on selected resources; (2) GAO identified some shortcomings and controversy in Reclamation's application of certain methodologies, and some of the data Reclamation used in making its impact determinations were dated, preliminary, or incomplete; (3) these limitations, combined with the inherent uncertainty associated with making forecasts, reduce the precision of the impacts in the statements, and some uncertainty remains; (4) according to GAO's analysis and the opinions of experts, these limitations are not significant enough to alter the relative ranking of the flow alternatives or render the final EIS unusable as a decisionmaking document; and (5) Reclamation recognizes that uncertainties still exist and intends to initiate a process of adaptive management that would provide for long-term monitoring and research to measure the actual effects of the selected alternative. GAO also found that, many of the key interested parties affected by the Glen Canyon Dam's EIS support the process used by Reclamation to develop the EIS as well as the implementation of the preferred alternative; however, while expressing their support, some interested parties raised specific concerns that still exist about the final EIS, including: (1) achieving compliance with the Endangered Species Act; (2) the economic impact of reducing the dam's hydroelectric power capacity; (3) the consideration of other possible causes of adverse downstream impacts; (4) the difficulties in measuring the impact of changes in the dam's operations; (5) the adequacy of measures for reducing the frequency of unscheduled floods; (6) the need for installing multilevel water intake structures on the dam to raise the downstream water temperature; and (7) the implementation of the adaptive management program.

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