KAHLOTUS, Wash. – Lower Monumental Dam’s navigation lock suspended service to recreational vessels this morning after loose concrete was discovered on the wall at an existing repair site inside the lock, according to operations officials with the U.S. Army Corps of Engineers’ Walla Walla District.
The section of aging concrete along monolith 15 has a history of cracking and spalling in recent years, creating potentially unsafe conditions for vessels using the lock. The monolith face needs to be restored to prevent further cracking, spalling and possible water intrusion to the interior of the monolith, according to Walla Walla District officials. Two of three phases of repairs to the site are already complete, with planning for the final phase under way.
Maintenance staff at the dam are acquiring materials needed to remove the loose concrete. Commercial vessels will be able to use the lock while repairs are in progress, but may experience some delays. Operations officials at the dam will reopen the lock to recreational vessels once the loose concrete is removed.
More about the monolith 15 multi-phase concrete repair project: the concrete being removed and replaced along monolith 15 is more than 40 years old. Phase-1 of the project was completed during January and February 2010 and removed about 1,400 tons of concrete from of the upper portion of the lock wall along monolith 15 (an area approximately 100 feet by 60 feet). Phase-2 repairs, performed during December 2010 through February 2011, completed removal of that concrete section down to the navigation lock floor and installed new concrete up the wall to a level just above the water line at the downstream or “tail race” level. Phase-3 repairs will be scheduled to occur when funding becomes available. New concrete will be placed in the remainder of the repair area – a space on the lock wall that is approximately 90 feet high by 60 feet wide by 4 feet deep where concrete was removed during Phase 1.
Lower Monumental’s navigation lock, located at Snake River mile 41.6, is part of the federal inland channel system that provides navigation from the mouth of the Columbia River near Astoria, Ore., to port facilities on rivers in Lewiston-Clarkston. The lock went into service on April, 15, 1969. The entire lock chamber is 86 feet wide by 650 feet long by about 130 feet deep. When in operation, vessels on top of the water surface level are lifted\lowered about 100 feet. In 2010, traffic through Lower Monumental’s navigation lock consisted of 2,559,600 tons of grains, petroleum products, fertilizer, wood products and miscellaneous cargo.
Public Notices and other navigation lock information are available on the Walla Walla District Web site at www.nww.usace.army.mil/html/offices/op/t/navdata/default.html.