Grant County PUD

Operational Excellence

Wanapum Dam Fish Bypass


The Wanapum Dam Fish Bypass project is one of the largest construction projects undertaken at the Priest Rapids Project since Wanapum Dam was built in the early 1960s. This structure is the first of its kind on the Columbia River and in the United States. The project is the result of a collaborative effort among diverse stakeholders.

The new fish bypass is essentially a 290-foot water slide that provides a non-turbine passage route past the dam for downstream migrating juvenile salmon.   After completing two years of testing, the Wanapum Dam Fish Bypass results reveal a remarkable 98 percent survival rate for sockeye salmon and a 99 percent survival rate for steelhead.  The outcomes of this project demonstrate a blend of sound economic practices, biological protection and enhancement of natural resources and greater engineering efficiencies for hydroelectric generation.


Grant PUD has been involved in researching alternative fish passage through Priest Rapids and Wanapum dams since the 1980s. A component of the recently acquired 44-year license includes a stated goal of at least 95 percent fish survival past the dams. Until recently, nearly 75 percent of downstream migrating smolts (juvenile salmon) entering into the Priest Rapids Project passed through turbines. Of those passing through turbines, 92.6 percent survived. To achieve this new 95 percent survival target Grant PUD set out to evaluate a number of fish passage alternatives.

For the past ten years, engineers, biologists, academicians and consultants worked to create a detailed analysis of how fish approached and passed through Wanapum Dam.  Grant PUD worked in concert with federal, state, local and tribal parties to develop and review study plans designed to examine various fish passage alternatives.  These efforts led to Grant PUD’s fish passage solution now known as the Wanapum Dam Fish Bypass.


The main focus throughout this project was set on improving downstream migrating juvenile salmon passage survival. The best way to achieve this was by providing an alternative route past the dam. The challenges associated with this lay in attracting and safely passing the smolts through a route other than the turbines while using less water than spillway passage.

In addition to the need for improved fish passage results, consideration of other stakeholders was also weighed. Staff incorporated the best possible outcomes for: increased hydroelectric generation, flood control, tribal considerations, federal reliability and compliance standards, recreation constraints, economic limitations and impacts to wildlife.  Beyond these issues, were also a number of logistical and engineering constraints.


The dimension, design, and fish passage water depth are all very unique to the project and a model for other hydro facilities. The design also incorporates an innovative air supply near the entrance gates which prevents adverse water pressures for passing fish. Many fish passage systems force fish through narrow channels of deep water that often involve human collection and transport past dams, yet the Wanapum Dam Fish Bypass utilizes natural falling water.


The plant reached its 10-year operating anniversary in 2009. Between the six plant employees, over 150,000 person-hours were worked through November 2009 without a lost time accident. The plant employees have now proven to be experts in their field. As AMP undertakes construction of new hydroelectric projects, it notes with pride that the staff and employees working at the Belleville Hydroelectric Plant have set the bar high for the operators of these future plants.

Stakeholder Quotes

“The survival and fish passage efficiency numbers being generated by the Wanapum Dam Fish Bypass facility speak for themselves.  What is likely not so obvious is the process Grant PUD employed to get to final construction. The utility engaged some of the best minds in the business and made use of state-of-the-art tools to develop a safe and effective route of passage for juvenile salmon and steelhead at Wanapum Dam. The utility also worked in close partnership with the agencies and tribes at nearly every step of development. So, while the new bypass is certainly a success, the process Grant PUD employed to develop the bypass should not be overlooked as a model for others to consider.”- Scott Carlon, Fish Biologist, National Marine Fisheries Service