By Chrissy Ewald | Nov. 27, 2024 | Grants Pass Daily Courier
Demolition is complete of a concrete dam that used to arc 270 feet across the Illinois River near Cave Junction and blocked access to 100 miles of spawning grounds for salmon, steelhead, and other migratory fish.
The removal of the Pomeroy Dam marks the first time in at least 80 years, and possibly as long as 126 years, that the Illinois River has flowed freely from where its tributaries meet at Illinois River Forks State Park to where it flows into the Rogue River near Agness.
On Tuesday, high water levels from heavy rains made it hard to see any fish in the water at the former site of Pomeroy, a privately-owned dam built in the 1940s to seasonally divert water into irrigation canals for a local ranch. But the landscape is greatly changed from when demolition began in August.
Where the dam once created a reservoir is now, after heavy rains over the past week, a rushing river with whitecapped rapids. On the west bank, where water used to flow into an irrigation canal that brought water two miles from the dam to a system of canals at the ranch, the former canal entrance has been filled with rubble from the dam and covered with soil and branches.
“It’s really hard to know where the dam was,” said Jim McCarthy, Southern Oregon program director for WaterWatch of Oregon, an environmental nonprofit organization with offices in Portland and Ashland.
In 2022, a lawsuit by WaterWatch against dam owner Q Bar X Ranch led to an agreement to remove the dam, at no cost to the ranch. The ranch received two solar-powered irrigation pumps to replace the earthen irrigation canal that led from the dam to the ranch, also at no cost.
Oregon law requires anyone operating a dam to provide passage for fish. Pomeroy had no fish ladder, and the lawsuit alleged the dam was hurting endangered coho salmon by blocking or impeding access to upstream spawning habitat, raising water temperatures, and hurting or killing fish that tried to jump over the dam. The suit also alleged irrigation ditches weren’t screened properly, so salmon were getting into the ditches and dying.
“That’s why the dam was an issue. People aren’t allowed to make it tough for fish just because it’s convenient for them,” McCarthy said. “They’ve got to take steps under the law to build a fish ladder. If they can’t afford to do that, there are state and federal and private funds to rip the dam out. That’s what we did here.”
The dam did not provide flood control or generate hydroelectric power, McCarthy said.
This was the second dam removed in the Illinois Valley basin in the past two years. Last year, WaterWatch partnered with the Siskiyou Field Institute to remove a dam on the organization’s property on Takelma Creek, which flows into Deer Creek and then into the Illinois River. The Illinois, in turn, is a tributary of the Rogue River.
It’s part of an ongoing slate of dam removals in the Rogue River basin, including the 128-year-old Williams-Whalen Dam on Evans Creek near Wimer in June of this year, the Lovelace Dam on Slate Creek in the Applegate basin last year, and the biggest of all, Savage Rapids Dam in 2009 and Gold Ray Dam in 2010.
WaterWatch announced Tuesday the completion of the first phase of the $3.7 million Pomeroy Dam removal project. Funding comes from state, federal, and private conservation group grants.
Along with the removal of the dam and installation of the new pumps, the project includes replacement of three culverts. Two are already in place under West Side Road, which hugs the west bank of the river near the former dam site and crosses several creeks that provide habitat to fish. The new culverts are wide concrete arches that leave a natural, rocky streambed underneath. The third culvert, located on private property, is a project for the coming year, McCarthy said.
Crews also hacked away at blackberries on the riverside common area of a homeowners’ association located next to the former dam site, and McCarthy said they will return next year to attack the brambles again.
As far as data collection on how the dam removal is affecting fish populations, McCarthy said the project managers are required to check that fish passage is being maintained, but this project won’t have before-and-after counts of fish.
The removal of the dam means multiple species of fish, including endangered coho salmon, have unimpeded access to an average of over 100 miles of upstream spawning and rearing habitat. That figure was calculated by the Oregon Department of Fish and Wildlife in a 2019 inventory of barriers blocking fish across the state. Pomeroy Dam was in the highest-priority group for removal.
According to WaterWatch, research suggests there were dams before the Pomeroy dating to 1898. If that’s correct, removal of Pomeroy means the Illinois is now flowing freely for the first time in 126 years.
Before demolition in August, a crew of staff from the Oregon Department of Fish and Wildlife, U.S. Fish and Wildlife, Bureau of Land Management, and the U.S. Forest Service plus local volunteers scooped up and relocated fish from above the dam.
Some local residents, including members of the homeowners’ association abutting the dam, protested the dam removal. An 11th-hour legal challenge to the dam’s removal was quickly dismissed.
WaterWatch said Grants Pass-based Dietrich Construction did most of the work. The engineering firm River Design Group, based in Corvallis, provided field studies, design, and construction oversight.
McCarthy said dam removal projects can help build resilience against climate change.
“We don’t have control locally over climate change, but we do have control here over this dam. We had control over Takelma Dam,” he said. “We can take this old technology, replace it with new, reduce the overall stress level on these fish and keep them around longer. Hopefully forever.”
This article originally appeared in the Nov. 27, 2024, issue of the Grants Pass Daily Courier. Photo by Julie Anderson.