A private developer wants to build a new transmission line stretching 100 miles from The Dalles to Portland — pitching the project as a critical fix for one of the region’s most pressing energy problems.
But there’s a catch. Most of the high‑voltage cable would be buried beneath the Columbia River. It would be the first project of its kind in the Pacific Northwest.
The proposed line, dubbed the Cascade Renewable Transmission System, would bring wind and solar power from eastern Oregon, Washington, Idaho and Montana into western Oregon, helping to break a bottleneck that has long stymied efforts to move renewable energy to the population centers that need it most.
It’s potentially the fastest available option to get power from eastern Oregon into Portland, Hillsboro and other points west.
The technology has been used successfully in both the U.S. and Europe, said Chris Hocker, senior vice president with PowerBridge of Connecticut, the project’s lead developer.
“The need for more transmission in the region is clear,” Hocker said. “Our line is needed, and not just to serve load but also to help facilitate other transmission that is going to be built.”
The innovative proposal, though, has alarmed environmental groups, tribes and river advocates who worry it could pose major risks to the region’s dwindling salmon runs and infringe on treaty‑protected tribal fishing rights.
“This proposed project has the potential to disturb and degrade important salmon, steelhead, lamprey and other culturally important fish habitat and disrupt fishing practices, damaging significant cultural and historical resources,” said Teryn Yazdani, a staff attorney with the Hood River-based nonprofit Columbia Riverkeeper, which opposes the project.
An influential tribal commission has called the project “unprecedented” and withheld its opinion so far.
Commission officials said the developers must supply much more site-specific data on the effects to the river system and its fish, including whether heat generated by the cable could elevate water temperatures for cold water-loving salmon.
Dire need
It’s undeniable: Oregon is in desperate need of transmission infrastructure.
The state’s clean energy mandates require investor‑owned utilities to shift away from coal and natural gas generation and replace it with wind, solar and battery storage.
At the same time, power demand has surged, driven primarily by the rapid growth of data centers and high‑tech companies like Intel. While converting homes and businesses to electricity and more electric vehicles also contribute to the demand, it’s to a lesser extent.
The challenge is that most new wind and solar projects are being built east of the Cascades – not only in eastern Oregon but also in Montana or Wyoming, where large wind farms are concentrated.
Meanwhile, the fast-growing population centers and industrial hubs are on the west side of the state, in the Portland area, the Willamette Valley and coastal communities. And Oregon lacks sufficient high‑capacity transmission to move the new renewable power east to west where much of the demand is.
Historically, the Bonneville Power Administration has been the default on all things transmission. The federal agency markets hydropower from 31 federal dams in the Columbia River Basin and it owns and operates 75% of the Northwest’s high-voltage lines.
BPA built much of its 15,000-mile high-voltage system from the late 1930s to the 1970s but that has ground to a near-halt in recent decades.
BPA’s transmission system is now effectively maxed out. In recent years, the agency has been swamped with requests from developers and utilities to connect new solar and wind projects to its grid, with 68,000 megawatts of requests in its transmission service queue – enough to light up 68 cities the size of Seattle, which has an average consumption of roughly 1,000 megawatts.
Because the request queue has grown so large, BPA temporarily paused parts of its transmission‑planning process and halted new long‑term transmission service requests while it overhauls how it studies and approves those requests.
The agency is now working on more than 20 proposed transmission expansion projects totaling roughly $5 billion – but most are still at the planning stage and will take years to permit and build. Even once completed, those projects won’t be enough to meet the region’s rapidly growing appetite for power.
Would PGE use the power?
The under-river cable could be a faster, easier-to-complete project compared with other transmission projects in the works in the region, its backers argue.
It would be developed and owned by two Connecticut-based companies — PowerBridge, which specializes in underground and underwater high‑voltage transmission, and Sun2o, a solar and battery storage developer.
The project is now formally under state review after the developers submitted an application to Oregon’s Energy Facility Siting Council earlier this year. The state of Washington and the federal government are also reviewing the proposal.
The developers said they chose the Columbia River because it aligns perfectly with where the power needs to travel. The river already functions as the Northwest’s “power highway,” they said, with hundreds of hydroelectric dams and nearby substations producing over half of the Northwest’s electricity. Existing BPA high‑voltage transmission lines also run parallel to the river.
If developed, the 320-kilovolt high-voltage direct current line would run mostly under the riverbed for about 100 miles, from the Big Eddy substation near The Dalles in Wasco County to Portland General Electric’s Harborton substation in Portland. It would bring 1,100 megawatts (slightly over 1 gigawatt) of clean electricity east to west – enough to power roughly 825,000 homes.
Hocker said he expects that PGE would be the principal customer for the transmission capacity. The developers have formally asked to connect the project to PGE’s system through the grid‑interconnection process, Hocker said, and the utility is now studying that request and its impacts.
PGE’s spokesperson Andrea Platt said it’s “premature to speculate that this project will serve PGE customers,” adding that the utility continues to conduct its analysis of the project.
In its long-range planning documents, PGE projects that by the mid-2030s it will need more than 4 gigawatts of additional transmission capacity to reliably deliver clean power to its customers. The utility includes the Cascade Renewable Transmission Project among a number of project options that could allow it to expand access to much-needed solar and wind resources to help satisfy demand for power and clean electricity mandates.
Burying a cable under the river wouldn’t necessitate any additional transmission system upgrades, wouldn’t require a shutdown of any part of the existing system during construction and could facilitate other future transmission upgrades, the developers said.
Hydroplow, dredging and berm
If the transmission under the river is approved, it would be installed in the riverbed using a hydroplow — a machine that uses high‑pressure water jets to loosen up sediment, cut an 18‑inch trench, lay the cable and let the sediment settle back over it. Some pre‑installation dredging would likely be needed in shallow areas so the plow can reach the burial depth required by federal rules.
Where burial isn’t possible, a concrete rock berm would be used to weigh down the cable and protect it from damage.
The line would come onto land for about 7 miles near Stevenson, Washington — where it would be buried out of sight – to avoid the Bonneville dam, locks, juvenile fish passage and tribal fishing areas, the application shows.
The developers rejected alternative transmission routes along Interstate 84, Washington’s Route 14 and railroad rights of way as unworkable.
The Oregon Department of Transportation said long, linear utility installations aren’t allowed in state highway rights of way. Unstable or basalt rock terrain ruled out Route 14 and the railroad corridors. Other overland routes across the Columbia River Gorge – a federally protected scenic area – also proved non-starters, given potential impacts on bridges and strict scenic vista rules.
Burying the line under the river would preclude running long wires and massive steel towers across the land, the developers said, avoiding disputes over visual impacts to rural landscapes and conflicts over buying or seizing private land – which have bogged down other recent projects such as the Boardman to Hemingway transmission line in eastern Oregon.
“The project will be invisible,” Hocker said. “It doesn’t involve either expanding existing overhead lines or creating new ones, which historically has always attracted a lot of opposition.”
That also removes wildfire risks and strengthens the entire grid, he said, because if another line goes down due to weather or fire, the under-river line would continue to operate.
Potential fish impacts
Environmental groups and tribes counter that the transmission line won’t be invisible to the fish and the river ecosystem that it could disrupt – nor to the people who depend on those fish for sustenance and spiritual practices.
The tribes in the region and the Columbia River Inter-Tribal Fish Commission, a Portland-based organization that manages tribal fishing sites and fisheries for local tribes, have yet to take an official position on the project “given how much information is missing that would be needed to make a fully informed decision,” said Jeremy FiveCrows, a commission spokesperson.
But in extensive comments filed last month with the U.S. Army Corps of Engineers, the tribal commission outlined a long list of concerns about the potential impacts to salmon and steelhead.
Beyond construction disturbances, the tribes’ top issue is that the cable’s operating temperature will continuously discharge heat into a river already exceeding temperature standards. Additional heat could kill salmon, steelhead, lamprey and white sturgeon, which are highly valued tribal First Foods and protected by treaty rights.
The underwater transmission cable’s magnetic fields could also interfere with migration and spawning, the tribal commission said in its letter to the U.S. Army Corps of Engineers. Salmon use the Earth’s magnetic field as a compass to navigate and research has shown their behavior can change when magnetic fields are altered.
Of the 16 salmon and steelhead stocks that historically returned above Bonneville Dam on the Columbia, four are now extinct and more than half of those remaining are listed under the Endangered Species Act. Some of those fish runs have fewer than 50 wild fish returning to spawn.
River modeling
PowerBridge’s Hocker acknowledged those and other concerns are legitimate but previous analysis – over 150 studies in total – has shown the impacts on salmon and other fish will be “temporary and negligible,” he said.
That includes a study in the San Francisco Bay area, where a 53‑mile high‑voltage direct current transmission line, the Trans Bay Cable, runs underwater. The study, commissioned by the U.S. Department of Energy and the Department of the Interior, was done by the Electric Power Research Institute, a Palo Alto-based organization that conducts scientific and technical research for the electric power industry.
The study showed that once the cable was activated, some fish showed changes in movement patterns, including approaching or crossing the cable area and occasionally deviating from their migration path. The changes sometimes increased migration time but didn’t prevent fish from completing their migrations. The study also found that the magnetic field impact from bridges was far greater than that from the transmission cable but also didn’t pose a barrier to fish migration.
Preliminary results of current modeling undertaken as part of the Columbia River proposal also show “zero temperature impact to the water and that the electromagnetic field impact is extremely localized,” Hocker said.
Because the cable will be buried 10 or more feet under the riverbed, the field will dissipate by the time it reaches the river, he said.
“There’s no study I’m aware of that indicates the cable would harm fish,” he said.
The technology is well-established, Hocker said.
That includes the Neptune Regional Transmission System, a 65‑mile transmission line running mostly underwater and underground from New Jersey to Long Island; the Hudson Transmission Project, a 10-mile underground and underwater transmission line from New Jersey to Manhattan and the Cross‑Sound Cable, a 40‑mile submarine line from Connecticut to Long Island.
The Champlain Hudson Power Express, another underwater and underground transmission line, is scheduled to come online next year to bring Canadian hydropower to New York City. The technology also is common in Europe where high voltage direct current transmission lines are used to connect offshore wind farms and cross‑border grids, the developers said.
But the tribal commission said the developer will need to provide more analysis tied to the Columbia because available studies and data are derived from marine transmission systems and other river systems that have different species and conditions than those here.
The commission also said the project’s approval would set a precedent that could transform the river into a utility corridor for other infrastructure projects and more industrial uses and risks repeating a hurtful history of harm to the tribes.
“The region has a troubling history of federal infrastructure development that disregarded tribal treaty rights and resources,” the commission wrote, referring to the construction of dams and the building of the Pacific Northwest-Pacific Southwest Intertie, a transmission line built in the 1960s from the Columbia River to the Los Angeles area.
“This pattern of development that displaced tribal communities and destroyed fisheries while providing benefits to others at the expense of tribal communities should not be repeated on top of the cumulative unfilled promises made to tribal communities along the Columbia, including housing, restoration of salmon and lamprey and cleanup of contaminated sites.”
What’s next
The Columbia River project is under state and federal review.
The developers turned down fast-tracked federal permitting approval offered by a Trump administration executive order.
The Army Corps of Engineers is expected to release a draft environmental impact statement by the end of this year.
“Obtaining approvals from Oregon, Washington and the Army Corps are equally important and necessary, so we saw no advantage in trying to fast-track the federal process as a separate effort,” Hocker said.
He said he expects the agency and the two states to wrap up their reviews in the next two years.
If the project is approved, construction would take up to three years to complete because cable installation can occur only during seasonal work windows to protect migrating and spawning fish.
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