New lock gate arrives at Lower Monumental Dam

The massive replacement part will be installed beginning next week.


The arrival of a replacement part usually isn't a big deal. But there are exceptions.

What's happening today at Lower Monumental Dam on the Snake River qualifies as one of those cases. In this case, the replacement part is about eight stories high and weighs about 700 tons.

Those are the dimensions of the dam's new lower lock gate, which is scheduled to be offloaded starting at noon today. Fabricated in Vancouver, Wash., the huge steel structure arrived at the dam last night after being floated up the Columbia and Snake rivers.

Replacement of the 41-year old lower lock gate is one of three major rehabilitation projects at dams operated by the U.S. Army Corps of Engineers slated to start Dec. 10.

The repair work will close the entire Columbia and Snake rivers transportation system through March.

Along with Lower Monumental, lower lock gates will also be replaced at The Dalles and John Day dams on the Columbia River. Other locks in the system will be put out of service during the extended closure for routine maintenance or for more extensive repair work.

Hoisting the parts of the replacement gate, which has been fabricated in three sections, will require the services of an equally-huge crane that was assembled at the dam earlier this year. The Lampson Transi-Lift LTL-1200, which has a 1,200-ton lift capacity, will be used to take the old gate out of its mountings and then slip the new structure into place.

The $13.6 million project at Lower Monumental Dam is being paid for by funds from the American Recovery and Reinvestment Act.

Andy Porter can be reached at or 526-8318. Check out his blog at


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