Dams open after maintenance closure

Navigation locks along the 350-mile-long federal Columbia-Snake river navigation system are back in business after a temporary closure to perform annual maintenance, according to U.S. Army Corps of Engineers navigation officials at the Walla Walla District.

Each year, the Corps suspends navigation service at the eight dams between Portland and Lewiston for inspections, repairs and maintenance on navigation locks.

The 2012 maintenance outage began March 6. Navigation locks on the Columbia River dams reopened March 20. Dams on the Snake River returned their locks to service March 27. The extra week was needed to replace downstream lock gate cables at Ice Harbor and perform lock wall repairs at Lower Monumental.

The concrete wall work at Lower Monument’s navigation lock marks the completion of a three-year phased project to repair cracking and spalling occurring along monolith 15 inside the lock.

Monolith 15 has a history of cracking and spalling which created unsafe conditions for vessels. Old concrete from the entire monolith surface — an area approximately 130 feet high by 60 feet wide by four feet deep — needed to be replaced to prevent further cracking, spalling and water intrusion to the interior of the monolith.

Phase 1, conducted in 2010, removed old concrete from about 100 by 60 feet of the surface. Phase 2, conducted during the 2011 extended lock outage, removed the remaining 30-by-60 feet of surface, and replaced it with new concrete up to 40 feet from the bottom of the lock using cast-in-place concrete. The Corps awarded a $969,716 construction contract to Mowat Construction Company of Woodinville, Wash., to conduct Phase 3 repairs which involved anchoring pre-cast concrete blocks into the repair area.

Additional work associated with the multi-year project included installing waterstops, grouting cracks and repairing culvert cavitation.