The navigation lock at Bonneville Dam was closed on Thursday, Sept. 5, after lock operators detected problems with the lock during operation. Engineers dewatered the lock Sept. 6, performed an inspection and discovered that the downstream concrete sill, against which lock gates create a water-tight seal, had cracks.
The U.S. Army Corps of Engineers — which operates the navigation locks, dam and associated hydroelectric project — closed the lock to vessels on the river on Sept. 6. They determined after the inspection that continuing operation posed the possibility of damage to other lock components. According to the Portland District engineering team, the damage was unusual, and the annual inspections of the dam, last performed January 2017, did not reveal any abnormalities.
“This lock closure is significant, which is why our engineers, experts and contractors are working tirelessly to ensure we get the locks back in service as quickly as possible,” said Portland District Commander Col. Aaron Dorf. “It is not lost on anyone in the Portland District that this outage has tremendous impacts to Columbia River users. “Between now and Sept. 30, our teams will be working around the clock to construct the new sill to restore Columbia River traffic.”
The Portland District awarded the emergency repair contract to Advanced American Construction, based in Portland, and crews began demolition and removal of the concrete sill, which measures about 5 ft tall, 9 1/2 ft wide and 100 ft long. Work on the lock will include demolition, drilling holes for rebar, forming the new sill structure and allowing time for the concrete to cure.
The Corps says the lock will return to service on Sept. 30.
For the duration of the repairs, the Bradford Island Visitor Center and recreation areas on Bradford and Robins islands on the Oregon side are temporarily closed.
The fish hatchery at Bonneville is unaffected by the navigation lock. The Corps’ Washington Shore Visitor Complex is also open, and features interactive exhibits, powerhouse tours and fish viewing.
The 1,050-MW Bonneville facility is the last dam on the Columbia River before it enters the Pacific Ocean. The first powerhouse, spillway and original navigation lock were completed in 1938 to improve navigation on the river and provide hydropower to the Pacific Northwest. A second powerhouse was completed in 1981 and a larger navigation lock in 1993.