Corps to Begin Inspecting
by Kristi Pihl
Inspection of the Tri-City levees for culvert breaks and seepage could begin within the next week.
The Army Corps of Engineers discussed its plans and safety ratings for the Tri-City levees, also known as the McNary Levee System, and the Lower Monumental and Ice Harbor locks and dams with about 30 people at a Wednesday meeting. The levees received the second lowest safety rating possible.
A national review identified the levees as an urgent risk, with possible seepage and erosion problems.
The two Snake River dams received the next highest rating, due to overtopping concerns and possible navigation lock gate failure.
In 2007, the Corps started a nationwide inventory of its dams and levees and began rating them using a system based on risk of failure and the consequence of risk, said Donna Street, chief of the engineering and construction division and dam safety officer for the Corps. Hurricane Katrina sparked the process.
The Corps has not seen evidence that the Tri-City levees have seepage or culvert breaks, she said.
But culvert breaks are a concern because the levees are more than 50 years old, and culverts have about a 50-year life cycle, she said.
Also, water could be seeping into the levee embankments along the culverts, Street said. If that seepage occurs, the levees could erode.
At the two Snake River dams, an extreme flood could cause water to go over the earthen embankment or the railway and cause the dams to fail, she said.
That much water is rare. The highest water measured on the Snake River at the dams was 300,000 cubic feet per second in 1974, and the dams are built to handle 840,000 cubic feet per second, said Jeremy Giovando, Corps hydraulic engineer.
Both dams also have metal fatigue and cracking at the navigation lock gates, which could cause failure, Street said. "We are repairing it on a regular basis," she said.
Nationwide, the Corps has about 40 years' worth of repairs to do, said Lt. Col. Michael Farrell, Walla Walla district commander and engineer. And that work will be prioritized for federal funding depending on the safety ratings.
The Corps just finished developing interim measures to deal with the possible risks found in the review, said Allen Pomraning, Corps senior project manager for Inter-Agency and International Projects. Those should be completed in the next three years.
And the Corps already is working with Benton, Franklin and Walla Walla counties on emergency management planning, he said.
"We experience an emergency, but the community responds," Street said.
The Corps needs to complete additional studies to confirm the possible failure risks, Street said. That may lead to long-term fixes, depending on what is found, she said.
In April, the levee system safety rating caused the Corps to deny a Pasco request to lower the levee between roads 54 and 72. The city wants to lower the levee to widen the path and complete the 22-mile Sacajawea Heritage Trail that loops through Kennewick, Pasco and Richland.
The request cannot be approved until the safety rating is lowered to being a priority or normal, rather than urgent, Street said. Corps headquarters would have to approve the lowering.
David Fort of Pasco said the Corps already has allowed the lowering of other levees in the Tri-Cities. If the levee was lowered, Fort, who lives along it, said he would be able to see the river from his home. The lowering would widen the levee and make that part of trail safer, he said.
Several landowners expressed concerns about wildlife burrowing in the levees.
Franklin County Commissioner Brad Peck said he has lost four trees to beavers migrating along the river, and has seen more than a dozen marmots on a sunny day.
Stacey Foraker of Pasco said she appreciated the Corps listening to landowner concerns and asked that landowners be notified when spraying is happening along the levees.
Foraker would like to see the Corps leave some of the vegetation, such as sagebrush, along the levees. Some people enjoy natural vegetation and wildlife along the levee, she said.
To report safety concerns along the levees, such as wildlife, call the Ice Harbor Natural Resources office at 509-547-2048.
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