Corps of Engineers gets OK to dredge

LEWISTON – Parts of the lower Snake and Clearwater rivers will be dredged for the first time in seven years starting next week.

The National Wildlife Federation and other environmental groups agreed not to sue the U.S. Army Corps of Engineers over the dredging work in exchange for a promise that the corps will perform a long-term study of sediment problems in the river.

The agreement is part of a settlement reached after the groups sued and successfully blocked dredging work planned for the winters of 2002 and 2004.

Congress has mandated that the Corps of Engineers maintain a 14-foot shipping channel, but parts of the channel are as shallow as 8 feet in some places.

That has prevented the port and barge operators from filling barges to capacity. Last spring two barges got stuck.

“We won’t have to contend with that for a couple of years,” Arvid Lyons, general manager of the Lewis-Clark Terminal at the Port of Lewiston, told the Lewiston Tribune.

“We can load them full. We won’t have to worry about light-loading them,” he added.

Under a $5.1 million contract with the Corps of Engineers, Manson Construction Co., of Seattle, plans to dredge about 400,000 cubic yards of sand and silt from the shipping channels. The work is set to begin Thursday and finish by the end of March.

The company will use a clamshell dredge with a hinged bucket to scoop the sediment. Jack Sands, the corps’ project manager in Walla Walla, said hydraulic, submerged pipe dredges could not be used.

“We are not allowed to use that because of environmental concerns and endangered species,” he said. “They don’t want it sucking up endangered salmon.”

The dredged sediment will be carried by barge about 23 miles downriver to Noxway Canyon, where it will be used to create shallow-water rearing habitat for juvenile salmon and steelhead.

“We are taking essentially a mid-depth area and bringing it up to a shallow depth so it’s better habitat,” Sands said.

Stirring up the silt will likely produce a sediment plume, Sands said, but it shouldn’t turn the entire river muddy.

The work will be monitored to make sure it does not violate state and federal standards for turbidity and levels of pH, ammonia and dissolved oxygen.

“We don’t anticipate any problems,” he said. “Most of the material we will be removing will be of a sandy consistency instead of a fine silt or clay.”

The Ports of Lewiston and Clarkson will be billed for dredging work in their berthing areas. The Port of Lewiston expects to pay about $200,000. The Port of Clarkston said it’s expecting its bill to run between $180,000 and $225,000.