Corps Seeks Comment
by Eric Barker
Project would remove sediment clogging navigation channel
near confluence of Snake and Clearwater
The Army Corps of Engineers is planning to remove sediment clogging the navigation channel near the confluence of the Snake and Clearwater rivers as soon as next winter.
The agency is collecting public comments on the proposed project designed to restore the channel to a depth of 14 feet and a width of 250 feet.
Commercial shippers use the channel and the locks on the four lower Snake River dams to move grain grown on farms in Idaho and Washington to the Columbia River and eventually the Port of Portland. The channel and lock-and-dam system is also used by cruise boats that call on the Port of Clarkston.
The channel was last dredged during the winter of 2014-15 when American Construction Co. of Tacoma was paid nearly $10 million to remove 400,000 cubic yards of sand and silt. Since that time, sediment has accumulated in the channel and last year the corps kept the pool behind Lower Granite Dam 3 feet higher than normal to give commercial river traffic more room to maneuver. But that water level decreases the speed of the river and the survival odds of threatened and endangered juvenile salmon and steelhead during their downstream migration to the Pacific Ocean.
The Corps was given $6.1 million in the recent Infrastructure Investment and Jobs Act to do the work, which also is expected to remove 250,000 to 400,000 cubic yards of sediment and include dredging at Ice Harbor Dam near the Tri-Cities. The dredge spoils would be dumped in deeper areas of the river downstream of the confluence or disposed of on land.
Project leader Alex Colter, at the Corps's Walla Walla District, said next winter's dredging is expected to cover a smaller area compared to the work in 2015.
"We have had a really hard time acquiring funding to do that entire footprint like we did last time," he said. "We have had to reduce it this time and only commit to what would be considered the federal channel."
That could leave some areas between the channel and the Port of Clarkston too shallow for both barges and cruise ships. The port has asked the agency to seek additional funding and is itself seeking money from the state of Washington to expand dredging, said Port of Clarkston Manager Wanda Keefer.
Colter said the work, if approved, could start Dec. 15 and would need to finish by about the end of February -- a time when such work is considered to be least harmful to protected salmon and steelhead. But the agency first needs to complete an environmental assessment that could be elevated to a more complicated environmental impact statement if significant threats to fish and other resources are identified.
Ben Tice, a Corps biologist heading up the assessment, said the agency's Programmatic Sediment Management Plan, completed in 2014, examined the environmental impacts of dredging and was designed to head off the need for lengthy EIS studies each time maintenance dredging is performed.
Environmental groups and the Nez Perce Tribe were so concerned about the impacts to protected salmon, steelhead and imperiled Pacific lamprey that they went to court in an effort to halt the 2015 dredging. A federal judge declined to stop the work and eventually sided with the corps.
Judge Dismisses Suit Against Snake River Dredging by Laura Berg, NW Fishletter, 3/7/16
Clear Channel: Dredging Projects Preserve Shipping in the Columbia River by Edward Stratton, The Daily Astorian, 9/29/17
Corps Looking for Input into Dredging Plan by Don Patterson, The Chronicle, 9/11/17