Corps to use man-made islands to corral Toutle River sediment

2010-08-11T21:30:00Z 2012-05-15T14:56:58Z Corps to use man-made islands to corral Toutle River sedimentBy Andre Stepankowsky / The Daily News Longview Daily News

TOUTLE — Years from now, the upper Toutle River may be dotted by tree-covered islands sporting names with a decidedly informal touch — Si Island. Kim Island. Eagar Island.

If their origins get lost in the mists of time, this will be the clue to remembering them: The islands were named for the workers whose efforts will help create them.

Under a $3.5 million contract with the U.S. Army Corps of Engineers, a Woodland-based contractor over the last month has driven more than 1,000 pilings into the broad floodplain of the north fork of the Toutle River.

The pilings will support a series of weirs that, if all works according to plan, will mimic the way nature controls and regulates rivers. If the plan works, the corps may have a new, flexible and comparatively low-cost way to control the flow of Mount St. Helens sediment into the Cowlitz River.

LKE Corporation is building two types of sediment-control works about a mile upstream of the big sediment-control dam the corps built across the river in the 1980s:

• Fourteen so-called "island creating structures," which are horseshoe-shaped weirs to which workers are bolting tree root wads and logs. The river eddies these structures create are expected to cause sediment to accumulate on their downstream sides, just like islands form in rivers below a log jam.

• A long "cross valley structure" made of piles and joined together by heavy planks. It will steer the river through a labyrinth of turns, or baffles. Slowing the current in this way will force the river to drop some of the thousands of tons of silt it carries downstream daily during a strong winter storm. Nature does the same thing when a big tree falls and wedges into place in a stream.

The project has turned a section of the floodplain into an eerie-looking zone that somehow resembles Medieval or Roman-era battlements or a stockade for monster bovines. Each 35-foot pile is driven about 25 feet deep, and the tops are shaven into a cone pattern and look like the blunted ends of broken pencils.

Core officials say the pilot project is testing whether the structures can help trap more silt behind the 125-foot sediment retaining dam. The dam has trapped 100 million cubic yards — a stack 9 miles high on a football field - but has capacity to trap more than twice that over the next several decades. The agency is hoping the pile structures make that happen more quickly, so less volcanic debris escapes into the Cowlitz River, where it can clog the channels and increase flooding odds.

If the pilot project works, corps officials say they may adopt the strategy on a much grander scale.

"We're trying to accelerate the speed with which silt accumulates" behind the dam, said Tim Kuhn, the Portland-based Cowlitz-Toutle project coordinator for the corps.

When it was first built, the sediment dam trapped about 90 percent of the material the Toutle brought to it. As the reservoir behind the dam filled up, though, its efficiency diminished, and now the dam stops only about 10 percent of the material. The corps would like to boost that to about 40 percent to 50 percent, Kuhn said.

"We don't have to trap all of it," because the Cowlitz can naturally flush some of the silt away on its own, Kuhn said.

The contractor selected for this pile dike structures is confident they will work. She's seen it before.

LKE Corp. has built similar structures on rivers across the West, though they're usually constructed to blend in with the environment, said President/Owner Kim Erion, 41, who grew up in a Woodland logging family.

The company has worked from the Canadian border to Yosemite National Park and as far east as South Dakota. According to Erion, LKE (which stands for Lorraine Kim Erion, her whole name) specializes in environmental restoration projects and has reclaimed more than 1,000 miles of logging roads and helped restore wetlands and hundreds of miles of stream habitat.

It has also built an island at Tule Lake National Wildlife Refuge in Northern California to help attract salmon-gulping Caspian terns away from the mouth of the Columbia River, Erion said.

The Toutle project is funded with federal stimulus dollars, and Erion said she's trying to keep the job as local as possible. About half her Toutle project work force - which has ranged from 30 to 50 workers — consists of people hired from the Cowlitz County area. They're working 10-hour shifts, six days a week, and collectively earning about $60,000 a week, according to Erion.

She said pilings are coming from a supplier in Sherwood, Ore. Parr Lumber in Woodland is the broker for the thousands of board feet of planks needed for the job, and a Vancouver company is supplying the hardware.

Workers are enthusiastic about the project. They've already begun naming the islands that will form behind the horseshoe-shaped weirs, which are different sizes. The biggest is called "Si Island," for a veteran who works on Erion's crew, she said.

Kim Island is named for Erion, and Eagar Island is for Stephen Eagar, the corps' technical lead on the project.

The islands eventually should become vegetated and serve as wildlife habitat. Long-term, though, they may be obliterated as sediment accumulates around them. That would be OK with her, Erion said.

"I know that if this disappears that (the project) worked," she said, pointing to one of the weirs under construction.

Kuhn said the corps will monitor the project closely this winter and decide whether it can be part of its long-range sediment-control strategy, now scheduled for adoption next year. The agency has considered simply raising the sediment dam, but that would cost hundreds of millions of dollars and would complicate the effort to eventually rebuild the north fork's salmon run.

By contrast, the weirs don't block fish and can be built in stages, giving engineers the flexibility to adjust to silt flow over time, Eagar said.

"It's an adaptive system."

Copyright 2014 Longview Daily News. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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