The Columbia and McNary Dam in Hermiston
Hermiston sits about 7 miles south of the Columbia River and McNary Dam, according to Wikipedia. The dam is the nearest large piece of river infrastructure to the city.
McNary Lock and Dam
The U.S. Army Corps of Engineers owns and runs McNary, on the Columbia River where Umatilla County, Oregon meets Benton County, Washington. The Corps' Walla Walla District describes a dam about 7,365 feet long with a powerhouse, a single-lift navigation lock, two fish ladders and a spillway. Construction began in 1947, and all generating units were running by 1957. The Corps lists the powerhouse at 14 generator units and 980 megawatts. Its purposes include navigation, hydropower and recreation.
Lake Wallula and the fish ladders
The dam creates Lake Wallula, which the Corps says reaches about 64 miles upstream and offers fishing, boating and camping. The National Park Service notes that the Corps works to keep Pacific salmon able to travel up and down the Columbia, and that the Pacific Salmon Visitor Information Center has exhibits and programs on salmon and hydropower. Hours and access change, so check with the Corps before a visit.