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What happens when you turn a reservoir town into a river town?

Ten years ago, Bonner got to find out.

On March 28, 2008, a backhoe breached the earthen wall of Milltown Dam and allowed the Clark Fork River to flow freely for the first time in a century. The confluence of the Clark Fork and Blackfoot rivers got many things from the transformation, and it gave away many as well. Those aren’t the same as wins and losses. But they certainly changed the score.

The most obvious entry in the “give” column was the giving away of not one but two dams. Milltown Dam hogged the spotlight as the plug that retained nearly 7 million cubic yards of toxic sludge and turned the area east of Missoula into a federal Superfund site.

Just months after it was completed in 1908, a massive flood washed tons of mining waste from the smelters at Butte and Anaconda down the Clark Fork. Most of it flowed to Bonner and settled beneath the placid waters of the Milltown Reservoir.

In 1981, inspections prompted by the recently passed federal Clean Water Act detected high levels of arsenic in Milltown’s drinking water wells. Previous floods and ice jams had sent surges of copper and other heavy metals over the dam, killing up to 75 percent of the fish downstream. But arsenic was known to cause cancer in humans, and the levels were hundreds of times higher than allowable limits.

Butte’s Berkeley Pit got Superfund status in 1985, shortly followed by Milltown Reservoir. Further study eventually got the 140 miles of the Upper Clark Fork River drainage included in the federal cleanup program.

But solutions came slowly. For a while, the plan was to simply fence off the reservoir and pump new water to the Milltown residents. A catastrophic ice flow down the Blackfoot River in 1996 put the problem in a whole different light.

“That dam was 100 years old,” said Karen Knudsen, executive director of the Clark Fork Coalition which got its start rallying support for improving the river. “It was aging, slumping, with structural problems and it was the only thing keeping a huge waste repository from the rest of the river. It was a major accident waiting to happen. There’s no worse place for a waste repository than smack dab in the confluence of two rivers.”

So Milltown Dam had to go away, along with the sediments poisoning the residents and fish. That brought up the second dam — a fixture of the Champion International plywood plant that once formed the log pond capturing tree trunks floating down the Blackfoot River. It was barely noticed when the reservoir flooded the confluence. Once exposed, it presented a hazard to downstream floaters and upstream migrating fish. So it came out, too.

That allowed us to “get” two free-flowing rivers. The state Natural Resource Damage Program capitalized on the restored confluence by underwriting a new Milltown State Park.

A public recreation and education site was part of the redevelopment plan for Milltown Reservoir from the beginning. Some ideas, like a whitewater play wave just above the confluence, got lost along the way. Lots of others got combined into what’s now Montana’s second-largest state park. On June 23, Milltown State Park Manager Mike Kustudia plans to cut the ribbon after years of legal and planning delays.

“We’re seeing so much new activity out here,” Kustudia said while strolling through the recently paved parking area at the mouth of the Blackfoot River.

His jurisdiction sprawls in every direction. It includes the Black Bridge pedestrian crossing a quarter-mile upriver, and an undeveloped 40-acre parcel even farther up across from Weigh Station Fishing Access Site. Over the Clark Fork River and high on the bluff where Milltown Dam once anchored perches the Overlook area, with a parking lot, restrooms, educational displays and trails leading down to the floodplain.

Upstream from the confluence, the Bonner Development Group is in negotiations with Montana Fish, Wildlife & Parks to donate a picnic shelter and 36 acres of river frontage. The Confluence portion below the Blackfoot mouth will also have picnic facilities, interpretative displays and a trail to the river for people to hand-launch boats.

Additional plans call for trails connecting the Black Bridge and Confluence areas, better access to the Bonner Development Group parcel, a land path to reach the upstream Blackfoot parcel and development of a plot where the Kim Williams Nature Trail dead-ends at an old railroad tunnel.

With luck and future funding, Kustudia hopes that railroad tunnel might be made safe enough for public travel. About 600 of its 700-foot length is in decent shape, but the remainder has dangerous structural issues. A footbridge connecting the Overlook and Confluence sides of the park also awaits a source of money.

Draining the reservoir meant giving away a population of non-native pike that depended on the stagnant water behind the dam. It also eliminated some fine sand beaches that became popular swimming holes upstream from Bonner. Once the sediments were exposed, the Superfund project paid for hauling 2.2 million cubic yards of it to a repository at Opportunity, near the historic Anaconda mining waste piles that caused the problem in the first place.

It also means we get a very different aquatic environment.

“With the removal of the dam, we now have a nice section of river to fish for trout,” said FWP Fisheries Director Pat Saffel. “We’ve already seen a bump in bull trout numbers in the North Fork of the Blackfoot, and a bump in cutthroat in the Clark Fork, especially between Rock Creek and Drummond. That happened immediately after the dam removal, and it suggests that large numbers of trout were caught below the dam. What we saw in Rock Creek is probably occurring in similar habitats like the lower Blackfoot.”

Biologists also radio-tagged a lot of large suckers before the dam was removed, Saffel said. Those fish migrated as far as Deer Lodge.

“That’s a massive redistribution of nutrients,” Saffel said. “They’re a prey species for other fish, as well as mink and river otters.”

The newly exposed floodplain has sprouted descendants of century-old trees that grew there before the dam was built. Unfortunately it’s also become home to some invasive weeds that require constant suppression.

“A flood in 2011 resulted in thousands of willows compared to what we could have established — it was insta-veg,” said Geum Environmental Consulting restoration ecologist Amy Sacry. But it also brought perennial pepperweed, leafy spurge, Dalmatian toadflax and knapweed. A groundcover called Reed canary grass has been particularly hard to keep at bay.

Flotillas of old logs also emerged from the mud. State and private contractors pulled more than 16,000 from the riverbanks, and thousands more have floated down to Superior and beyond.

We gave away a 3-megawatt hydroelectric generator in Milltown Dam, although it didn’t produce enough income to pay for the two-person staff maintaining it, according to Knudsen. And we gave away a source of arsenic in the drinking water. Of the 10 monitoring wells drilled in Milltown, six are now arsenic-free and levels have significantly fallen in the remaining four.

Paradoxically, cleaning up the reservoir meant we got more things to clean up. Missoula County Environmental Health Supervisor Peter Nielsen said that as the backwater was getting drawn down in 2006, an oily slick started appearing in a service pond inside the plywood mill property. That turned out to be a petroleum deposit that needed removal. When the water level got below a cooling pond along the Blackfoot, more trouble popped up.

“We sampled that and found PCBs (a powerful carcinogen),” Nielsen said. “We did more sampling, and found even more. They cleaned that up, but when we drilled a monitoring well, we found even worse deposits. It ended up being one of the biggest PCB cleanups for the EPA in this region. It wouldn’t have happened if all this Milltown cleanup didn’t transpire.”

Doug Martin was the Milltown restoration program manager for the state Natural Resource Damage Program. He said the big thing we gave up was the belief that rebuilding a river confluence after a century of damage was impossible.

“We can’t say anymore ‘that’s too large, too complicated, it can’t be done,’” said Martin, who now heads the NRDP in Helena. “If you put the right people together, with a common goal of getting things done, it can happen.

"When I talk to people and Milltown comes up, people who drive by on the interstate say it doesn’t look like a construction site. There was a dam there? People will question that. We all came together, removed 2 million cubic yards of contaminated material, took out a dam structure and rebuilt it, and people don’t recognize that something happened there. Now when I see somebody floating down it, it makes me smile.”

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Natural Resources & Environment Reporter

Natural Resources Reporter for The Missoulian.