The navigation lock at Lower Monumental Dam near Kahlotus will be out of service Sept. 9 and 10 to allow work on valves used to fill the lock.
An inspection of one of the valves on August found cracks that were causing it to malfunction. Now the second valve is demonstrating similar symptoms, according to the Corps of Engineers.
The locks are expected to reopen Sept. 11, but work on repairs could continue through early October.
Recreational boaters will be allowed through the locks during the repair period just twice a day. Times will be 9 a.m. and 6 p.m. for upstream boats and 9:30 a.m. and 6:30 p.m. for downstream boats.
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The repairs also will limit vehicle crossings at the dam. Travelers should call 888-326-4636 to find out if cars are being allowed to cross.