Abstract: Priest Rapids Dam is a large (955 MW) hydroelectric dam on the Columbia River in Washington State, USA. As part of regulatory requirements associated with its FERC (Federal Energy Regulatory Commission) license and other agreements, the Public Utility District No. 2 of Grant County, WA was required to design and install non-turbine fish passage for downstream migrating juvenile salmonids at the dam, for the purpose to help meet its pre-establish survival standards for salmonid smolts passing through the Priest Rapids Hydroelectric Project during their downstream migration. This presentation is a case study highlighting the numerous steps that went into the design of that nonturbine fish passage facility which started with a surface-spill test at Priest Rapids Dam in 2002, followed by a number of years of physical and CFD modeling. Throughout those years of design work on a fish bypass system, results from actively tagged salmonids smolts studies were used to guide and validate each step of the design process. In 2011, a construction contracted was awarded and the Priest Rapids Fish Bypass facility completed in the early spring of 2014. Final validation of this newly constructed facility came in the spring of 2014 with a survival and behavior study conducted using acoustic tagged yearling Chinook and juvenile steelhead smolts to evaluate the salmonid smolt survival rate through the bypass along with the fish passage efficiency (FPE) of the bypass facility.