The U.S. Army Corps of Engineers will repair erosion damage to a section of one of Bonneville Lock and Dam's fish ladders without delay, Corps officials said.
The damage is located near the spillway under the fish ladder that flows past the Bradford Island Visitor Center.
The erosion was caused by the record high flows experienced on the Columbia River this year, said Lt. Col. Glenn Pratt, Portland District deputy commander.
"Two sections of the fish ladder are not properly supported, so the fish ladder must be dewatered to decrease the weight on the sections," Pratt said.
There are fish ladders on both the north and south side of the Columbia River and the closure of one section should not significantly affect the migration, Pratt said.
"We are only closing one section of one fish ladder near the spillway," he said. "All others will remain open to provide safe passage for migrating fish."
In coordination with its regional partner agencies, the Corps decided to close the fish ladder Sept. 17. Next, engineers will inspect the dewatered section and prepare an action plan for repairs. The work is expected to be completed by mid-October.
Meanwhile, water levels may be up to three feet higher behind the John Day Dam from Oct. 1 to Oct. 31, when the Corps begins storing additional water for power generation.
Members of the public using Lake Umatilla between the John Day and McNary dams on the Columbia River should be aware of higher than normal reservoir levels during October.
Bonneville Power Administration has requested that the Corps allow additional water to be stored if necessary for power generation or water management purposes, as long as there is storage available that will not impact seasonal flood storage requirements. Higher water levels may also be seen on the nearby wetland areas of the Umatilla National Wildlife Refuge.
The operating levels allowed during October are based on Corps operating documents, and are significantly higher than those between April and September, when reservoir levels are kept lower to help juvenile fish move down river.
In order to balance the needs of juvenile fish migration with the needs of power generation and its other missions, the Corps manages the John Day pool (Lake Umatilla) in a manner that allows flexibility within an operating range for October of between 262.5 feet to 268.0 feet. The Corps has coordinated this water level increase with its federal, tribal and local partners.
Water levels above 267 feet have not been seen in October since about 1995, Corps officials said.