Dalles Dam

The Dalles Dam is located on the Columbia River at the town of The Dalles, Oregon and is operated by the U.S. Army Corps of Engineers (USACE). Changes in spill to improve the survival of juvenile salmon passing through the dam was one of the actions identified in the Federal Columbia Power System 2000 Biological Opinion that the USACE must take. Sapere was hired by the USACE to develop a strategy for making decisions about spillway changes at the Dalles Dam to improve fish survival while maintaining compliance with requirements for navigation, water quality, flood control, and dam safety.

Sapere facilitated workgroups at USACE and with the Regional Agencies to define the monitoring for evaluating performance of a recently constructed spillwall and the decision strategy for selecting likely alternatives to mitigate risks. This strategy resulted in a plan that:

• Evaluated alternative technologies to address potential performance problems that may remain after spillwall construction
• Developed a strategy for determining what alternatives to implements for each possible performance gap
• Defined monitoring plans to determine if the spillway meets performance objectives
• Identified the engineering, design, and planning tasks necessary to implement an alternate technology to ensure there weren't any delays in making necessary modifications to meet performance objectives.

Two years of testing following the monitoring defined in the Strategy has led to consideration of an alternative to lengthen the spillwall to further improve fish survival.