WALLA WALLA, Wash. – All 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 of Engineers’ Walla Walla and Portland districts suspend navigation service at dams on the lower Columbia and lower Snake rivers to conduct annual inspections, repairs and maintenance on the navigation locks at the eight dams between Portland, Ore., and Lewiston, Idaho. Dams operated and maintained by the Walla Walla District include four on the Snake River -- Lower Granite (Mile 107), Little Goose (Mile 70), Lower Monumental (Mile 41), and Ice Harbor (Mile 10) -- and McNary Lock and Dam, located at Columbia River Mile 292. The Corps’ Portland District operates the remaining three dams on the Columbia River -- John Day (Mile 216), The Dalles (Mile 191) and Bonneville (Mile 145).
The Corps coordinates lock outages with inland commercial navigation companies. Annual maintenance outages typically last two to three weeks, depending upon the work to be performed.
The 2012 lock maintenance outage began on March 6. Navigation locks at Corps dams on the Columbia River reopened their navigation locks on March 20 after completing routine annual inspection and maintenance activities. Dams on the Snake River returned their locks to service on 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 Monumental’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 4 feet deep -- needed to be replaced to prevent further cracking, spalling and water intrusion to the interior of the monolith.
“The phased construction approach helped minimize impacts to the navigation industry while maximizing repairs within the work-windows and funding constraints,” noted Steve Thompson, Walla Walla District project manager for the wall repair.
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.
“This is about maintaining safe and reliable passage through the Columbia-Snake river navigation system,” said Thompson. “The completed repair project will improve safety conditions for vessels using the lock and help protect the monolith from potentially damaging water intrusion.”
Photographs of the Monolith 15 repair work are available on Walla Walla District’s Facebook page www.facebook.com/WallaWallaUSACE.
The Columbia-Snake river navigation system is vital to the economic health of the Pacific Northwest. The system accommodated the transportation of an average of 17.5 million short tons of cargo annually from 1999 to 2008, according to the Corps’ Waterborne Commerce Statistics Center. 10 million tons equals about 2,700 barges, 100,000 railcars or 350,000 semi-trucks.
Public Notices and other navigation lock information are available on the Walla Walla District website at www.nww.usace.army.mil/html/offices/op/t/navdata/default.asp, and on Portland District’s website at www.nwp.usace.army.mil/op/n/home.asp.