With Coal in the Rearview, Future of Skookumchuck Dam in Question


On clear, sunny days, Mount Rainier can be seen in all its glory from atop the Skookumchuck Dam.

Birds glide steadily across the water in similar fashion to the Joint Base Lewis McChord aircraft that hums above. Wildlife — elk, deer, cougars and others — are often seen in the thick forests lining the reservoir.

This is quintessential Pacific Northwest wilderness, and it comes with a history.

Since 1970, TransAlta has operated the Skookumchuck Dam — a 190-foot high, 1,340-foot long earthfill structure — along the namesake river at its midpoint.

Located 9 miles east of Bucoda, the structure forms the rainwater base of the 4-mile long Skookumchuck Reservoir, which itself establishes the outflows from which the company draws water for its Centralia coal plant.

With TransAlta set to retire its second and final coal burner in 2025, interest in both the dam’s future and the company’s water rights has grown.

The Office of Chehalis Basin is currently conducting a wide-ranging study looking at whether alterations of any kind to the dam — including even a full removal — would improve either fish habitat or flood mitigation downstream.

Meanwhile, city and county municipalities are champing at the bit to purchase some of TransAlta’s water rights through its water bank, a system allowing the company to offload its existing year-round rights directly to those willing to pay for them.

But those rights are contingent on the dam remaining in its current operational form. And despite its divestment from fossil fuels, TransAlta Centralia employees say the current plan is to remain involved with the dam.

“We felt like there was some scuttle that TransAlta was driving the dam-removal train, and that’s not the case,” said Cody Duncan, a business developer for TransAlta. “I think the reality is we’re just agreeing to provide information for the study and that our intention is that the dam stays and we’re operating it as such.”

When The Chronicle toured the site Wednesday with TransAlta employees, outflows from the dam were at about 385 cubic feet per second (cfs), which includes a constant 20 cfs that gets pumped to a nearby state Department of Fish and Wildlife fish hatchery.

Per federal regulation, the dam is required to sustain a minimum outflow of 140 cfs, an easy task during Washington’s rainy months. During the month of November — which was historically wet for some parts of Washington — 11.9 inches of rain fell upon the reservoir.

In contrast, water flows out of the dam dipped to a low 45 cfs — half of which went to the hatchery — during last summer’s drought. The reservoir volume dried up to just 10 feet above the minimum level required per the dam’s federal permit, said Paul Hoebing, senior specialist for TransAlta.

“In order for there to be enough flow in the river to pull water out of it, the dam has to be here because in the summer months the flows coming into the reservoir are sub-20 cfs, they get down very, very low,” Duncan explained. “So, in order for a water right to exist downstream, the water physically has to be in the river. And so, without the dam, you would (only) have water in the winter months.”

Duncan said TransAlta established the water bank within the past few months, and it already has at least one joint-sale agreement from the cities of Centralia and Chehalis.

The company’s priority, Duncan said, is to make sure it has enough water at its one coal burner, then identify the rights that have gone unused from the second burner and market those.

“The way the water right process works in the state of Washington, if you don’t use the water you lose the water. By creating the water bank, basically, it preserves the water right in its entirety for the long term. By setting up the bank, the water can be utilized downstream by farmers or municipalities or businesses that have access to pull the water out of the river, is basically what it boils down to,” Duncan said.

The Skookumchuck Dam is not a designated water retention facility, meaning the primary purpose of the dam isn’t to reduce flood hazards downstream. The only retention aspect is the top of the structure at 477 feet, which during rainy events gets topped over, and by adjusting the discharge rate through a number of intake valves.

The dam has overtopped just once this season.

Below the dam, a small water basin serves as a rearing pond for more than 100,000 juvenile steelhead. Alan Boerner, a TransAlta hydro operator and the only employee who maintains the dam on a part-time basis, tosses small meal pellets out into the water.

A few seconds after the toss, the water splashes violently as the fish scurry to the top for an afternoon snack.

Boerner said he comes out to the dam twice a week, when he’s not working back at the coal plant. It’s something of a dream job for him, he said as the river hummed in the background.

Once a year, he gets to serve as the “gatekeeper,” opening a small waterway and releasing all 100,000 steelhead into the river. From there, they’ll swim down the Skookumchuck River into the Chehalis River, then take that stream into the salty waters of Grays Harbor.

After spending time at sea, the steelhead eventually migrate back up the Skookumchuck and spawn at the base of the dam before dying. Duncan said a 3% annual return — only about 3,000 fish — would be considered a healthy run.

There’s been some debate about whether or not Skookumchuck steelhead can make it further upstream from the dam. But even decades before TransAlta established roots — back when logging was king and the river was used as part of the economic opportunity — splash dams likely impacted fish migration along the river.

Hoebing said last year TransAlta trucked up about 1,000 fish to the reservoir in a rare experiment to see how they would interact with the habitat and if they would swim further upstream. The spawning potential upstream of the dam and its habitat still remains unknown, though.

“The Skookumchuck River is kind of unique in that, one, it’s got this dam right in the middle of it and, two, it’s one of the two major places where spring Chinook spawn in the basin. It’s got a ton of potential benefits. The dam was really helpful in the 2007 flood and spring Chinook is really important to local folks,” said Nat Kale, aquatic species restoration plan project manager with the Office of Chehalis Basin.

At the behest of the Chehalis Basin Board, Kale’s office is currently in second-phase research studying what improvements to the dam could be made to improve aquatic species habitat and flood retention.

They’re keeping an open mind about all options — from leaving the dam as is, to small improvements, to a complete removal of the dam.

“We’re so early in this process that we don’t want to take anything off the table,” he said.

At a bare minimum, an improved dam fish sluice is likely.

Much of the phase 2 research will collect data from hydrologic and hydrogeologic modeling. The Office of Chehalis Basin contractor is currently getting river cross sections, creating a model of the reservoir and flows, and getting a really detailed model on a section of the spillway to better understand the level of ease for fish passage.

Kale said they’re also looking to finalize approval this summer to get access to land owned by Weyerhaeuser Company along the reservoir. The critical work will allow them to further study the habitat potential for upstream fish rearing.

The conclusion of this phase of research in 2023 will also likely lead to some action by the Chehalis Basin Board, which may likely court TransAlta about dam alterations in the leadup to its 2025 divestment. But establishment of the company’s water bank may also prove impossible with any major demolition.

Put simply, the dam may remain long after its primary purpose has ended.