Local firm to remake river valley

River Design Group will oversee construction of a new Clark Fork River channel east of Missoula

By RICHARD HANNERS / Whitefish Pilot

River Design Group, a Whitefish company that oversees river restoration projects across the Pacific Northwest, was recently awarded the implementation contract for restoration of the Milltown Reservoir site east of Missoula.

"This is one of the largest projects of this type, possibly in the world," said Matt Daniels, a hydraulic engineer and River Design Group co-owner. "We're completely reconstructing a river valley."

The company landed the design contract for the restoration of the Clark Fork River in 2006 — one of the most prestigious contracts in their field. River Design Group is also involved in dam removal projects in Oregon.

Remediation work, including removal of contaminated sediments, and construction of a temporary bypass channel is being done by other contractors.

The restoration site is part of the largest Superfund site in the United States — 150 miles long and 150 years old, the result of hard-rock mining and smelting operations in Butte and Anaconda.

Milltown Dam was built in 1907 by William Clark, one of Montana's three Copper Kings. Clark blocked flow in the Clark Fork River at Hellgate Canyon to generate electrical power for his sawmills at Bonner and Missoula.

The very next year, a 500-year flood swept Butte and Anaconda clean of mine tailings, depositing much of the toxic, heavy-metal laden material behind Milltown Dam.

Clean-up and restoration of the site is overseen by the Montana Department of Justice's Natural Resource Damage Program under a consent decree with Atlantic Richfield Co. and NorthWestern Energy, the two companies found liable for the contamination.

According to the project schedule, this year will see the dam's spillway removed and the Highway 200 bridge replaced. Sediment removal will continue through 2009 while restoration and redevelopment begin.

Before a new channel could be designed, soil tests and core drilling were conducted and pits were dug in an attempt to locate where the Clark Fork River flowed before the dam was constructed.

The discovery of 100-200 year-old ponderosa pine stumps up to 24 inches in diameter beneath the sediments was an important find. A lithograph from the 1880s shows forest covering parts of the reservoir site.

The pines had replaced cottonwoods over time, indicating that vegetation succession was occurring and that the riverine system in this area was probably not a frequently disturbed, braided channel system, Daniels said. The pines might have been cut down to build the crib-style dam.

"This discovery led to the decision to lower the overall floodplain by four more feet," Daniels said. "It also proved the river bed meandered back and forth across the valley at a very slow pace."

The draft restoration plan went through a six-month public review process in 2005 that included input from U.S. Fish and Wildlife Service, Confederated Salish and Kootenai Tribes, Montana Fish, Wildlife and Parks, and the Clark Fork River Technical Assistance Committee.

At times, the discussion was contentious. An early plan to build a whitewater park at the site was rejected, and the discovery of the ponderosa-pine stumps bolstered the River Design Group design.

"One of the state's main objectives is to make the confluence of the Blackfoot and Clark Fork rivers reflect the morphology of the valley," Daniels said.

But with so many historical changes, the river cannot be recreated as it once was. Highways, railroad tracks, farmland and housing now occupy portions of the restoration site.

In addition, some of the contaminated sediments will be not be hauled off to Opportunity Ponds, near Anaconda. They will be left behind in locations outside the 500-year floodplain and outside of the groundwater flow path.

Digging out the new channel could take 4-5 years. The 1908 flood was the largest on record for the Clark Fork River, and the new channel must be capable of withstanding a very large flood. The short-term objective is make the channel functional and stable, Daniels said.

"We don't want it moving from side to side, taking out the revegetation work we do," Daniels said. "In 15 to 20 years, when the vegetation matures, we want our bank-stabilization structures to decompose and the channel to be free to move."

River Design Group has teamed up with Gary Decker, a hydrologist with Corvallis-based WestWater Consultants, and Tom Parker, an ecologist with Hamilton-based Geum Environmental Consulting.

Revegetation work could go on through 2011, including irrigation, monitoring and noxious weed control. Parker said 100,000 nursery plants might be used at the site, but they're also looking at products from Native Sod Solutions, a company in Driggs, Idaho.

Coconut-fiber mats measuring 3-by-15-feet and six inches thick could be used in places. They come complete with various sedges, willows and dogwood plants in place. Ten-foot long coconut-fiber "logs" with dogwood and alder plants rooted inside could also be used.

The coconut fibers last about seven years and help hold both soil and moisture. They're expensive, Parker said, so they'll likely be used in critical areas. Extensive seeding with grasses, forbs and wetlands species will also take place.

The implementation contract also includes a monitoring plan to ensure the project meets its objectives, Daniels said.

"The monitoring plan sets the bar for the project," he said. "People won't just be walking away from this."