STARBUCK, Wash. – Little Goose Lock and Dam’s navigation lock will remain closed to all river traffic to allow workers to replace key gate components that were examined during annual maintenance and determined to be in critical condition requiring immediate replacement, according to U.S. Army Corps of Engineers navigation officials at the Walla Walla District.
District planners estimate the lock may be returned to service by May 1. With the Little Goose lock out of service, the 2014 FCRPS Supplemental Biological Opinion (BiOp) fish transportation scheduled to begin sometime in late April may be delayed. Coordination of fish transportation operations and related research will be addressed through BiOp adaptive management processes.
During a June 13, 2013, routine inspection of the downstream navigation lock gate, engineers first detected a problem with a gudgeon -- the metal arm at the top of the south gate leaf that hinges and holds the gate leaf to the lock wall -- small cracks appeared to be forming. Phased-array ultrasonic testing was performed on July 25 to determine the extent of the cracking. Conditions at that time indicated the gate could continue to be used with increased monitoring on the gudgeon assembly. On March 12, additional ultrasonic testing was performed to assess whether cracking had worsened, followed by load-testing of the gudgeon on March 24 to determine if the gate was safe to operate.
Results obtained Monday evening indicated that cracks were propagating in the 50-year-old gudgeon component of a depth and rate of growth that metal fracture might occur if it the 334-ton gate leaf was put back into regular operation. For safety, the lock will remain closed until repairs are completed.
The Corps placed the lock out of service until replacement parts could be installed. Spare gudgeon assemblies for both gate leafs were ordered Sept. 26, 2013, after the cracks were originally identified.
“We are doing everything we can to minimize this emergency outage period -- all work has been expedited,” said Steve Hartman, repair team project manager. “The Corps is committed to meeting our obligations under the BiOp and to providing safe commercial and recreational navigation services at our locks -- this delay in reopening is necessary to provide safe locking.”
Contractors accelerated production of one of the ordered gudgeon assemblies, rescheduling machining and fitting tests to allow shipment of expedited parts to the dam by the first week of April. Repair-project team members are preparing an emergency contract solicitation and have already identified several contractors that have the capability and schedule to perform the necessary installation work. The Corps anticipates it will take several weeks to complete the installation work, and are estimating reopening by May 1. To reduce the time needed for staging and set-up, Corps staff at Little Goose are preparing the lock for immediate access by whichever contractor receives the award to conduct installation work.
A miter gate looks like a giant set of French doors. One gate leaf at Little Goose lock is about 118 feet tall, 43 feet wide and weighs 334 tons -- from 1986 through 2013, the gate performed 35,713 lockages. A gate gudgeon linkage is a key component of this style of gate, holding the gate into position at the top while the gate pivots to open and close (a hinge-like assembly). The steel gudgeon assembly is an original component of the lock and has not been removed since installation in the late-1960s.
The Corps has notified commercial navigators, fish managers and other stakeholders, and will continue to provide updates as they become available. Public Notices and other navigation lock information are available on the Walla Walla District website at www.nww.usace.army.mil/Missions/Navigation.aspx.