The Walla Walla District of the U.S. Army Corps of Engineers is constructing improvements to the Lower Granite Lock and Dam Juvenile Bypass System (JBS). The improvements are an important part of the Corps’ mission to save salmon and other endangered or threatened species.
The overall upgrade includes “daylighting” the current below-ground juvenile fish transportation piping from the dam to the juvenile fish facility to an above-ground flume; enlarging selected gatewell orifice openings to the juvenile collection channel; reconfiguring the transportation channel so it will transition to an exterior elevated concrete channel connecting to a new elevated concrete dewatering unit; and diverting excess water to new piping and valves to enhance adult fish ladder attraction, emergency facility water supply, and fish trap water supply.
Millions of juvenile fish pass over, around or through Lower Granite each year, with an average juvenile survival rate of about 93 to 96 percent. Any additional improvement in juvenile fish survival gained as a result of this facility upgrade is significant considering how many fish pass through the dam.
The Corps previously upgraded its lower Snake River juvenile fish facilities at Ice Harbor Lock and Dam, Lower Monumental Lock and Dam, and Little Goose Lock and Dam during the 1980s and 1990s. These improvements contributed to juvenile survival improvement, which leads to the ultimate goal of improved adult fish returns when those juveniles return from the ocean several years later.
Upgrades are planned to occur in phases with the intent of improving juvenile fish survival and increasing operational reliability of the bypass and collection system. When upgrades are complete, long-term operations and maintenance costs should also be reduced.
Construction of Lower Granite JBS improvements is divided into two phases, termed “Phase 1a” and “Phase 1b.”
More information is available at the fact sheet link "Lower Granite JBS Improvements" on the right-hand side of this page.