A northwest Oregon town is stepping up testing of the South Yamhill River, which supplies some of its drinking water, following reporting about a local wood-treating facility’s years of chemical spills and stormwater releases that state and federal regulators had documented but not widely disclosed. The Sheridan City Council has instructed staff to consult with environmental researchers and state regulators on a plan to test water samples for chemicals used by Canadian company Stella-Jones.
The city’s initiative highlights a gap between what environmental regulators know about water contamination and what municipalities learn about threats to public health and local ecosystems.
Mayor Cale George said the council moved to take control of the verification process after learning about the pollution.
“It would be nice to know what’s there, since we do have someone upstream dumping water that does have a chemical in it,” George said in an interview. “Unless we’re testing, we don’t know for sure.”
Years of Violations and Penalties
Investigative reporting in January 2026 disclosed that Stella-Jones had released stormwater tainted with toxic wood preservatives into the South Yamhill River over nearly four years. State and federal regulators had monitored these violations, but the public disclosure came through journalism rather than proactive regulatory communication.
The revelations prompted penalties totaling nearly $1.5 million. In August 2025, Stella-Jones pleaded guilty to state charges of unlawful water pollution and received a $250,000 criminal fine. The Oregon Department of Environmental Quality issued a separate $1 million penalty in September, which the company is appealing.
In its appeal, the company argued that Oregon DEQ misapplied hazardous-waste laws and failed to credit what it characterizes as corrective actions taken to mitigate environmental harm. Stella-Jones also pointed to contaminated groundwater on the property that predates the company’s ownership, arguing that state and federal regulators have failed to properly manage it.
The EPA had designated the facility as a Superfund location in 2001 and completed an initial environmental cleanup over several years. Pentachlorophenol, a likely carcinogen, was supposed to be contained within an underground wall the EPA maintains. In 2022, however, the agency reported that a plume of pentachlorophenol-contaminated groundwater was escaping containment and required investigation.
Regulators had banned pentachlorophenol use at the site during the Superfund cleanup but reauthorized its use in 2011. Stella-Jones was first cited for excessive pentachlorophenol in stormwater in 2015, a year after acquiring the property. Since early 2023, the company has exclusively used DCOIT, a less toxic preservative. The company has not violated its water permit since the Oregon DEQ penalty announcement. In December 2025, Stella-Jones added extra storage capacity to prevent untreated rainwater spills during atmospheric river events and is planning upgrades to its stormwater treatment system.
What EPA Found
The EPA’s investigation, documented in a 1,600-page report completed in January 2026, details contamination on and around the facility with potential impacts to aquatic life and wildlife. The report concluded that some contamination is attributable to Stella-Jones operations, while other contamination results from pre-existing migrating groundwater on the property.
The primary pollution sources identified were pentachlorophenol, copper, and dioxin. Testing of sediment samples from the South Yamhill River and Rock Creek, an adjacent waterway, found dioxin levels higher than EPA screening values by at least two orders of magnitude, suggesting potential population-level effects on benthic invertebrates such as crayfish, worms, and insect larvae.
A Sheridan resident reported to state regulators in August 2023 that crayfish had disappeared from the river downstream from the Stella-Jones site. Jim Buckles, Sheridan City Council president, said the observation raised serious concerns.
“I have a pretty strong concern about when something as simple as crayfish suddenly disappears from our water,” Buckles said. “That’s not a good sign. Because not only do we have an intake on the river that we get part of our city drinking water from in the summer, (but) kids go out and play in it, and people on their canoes and kayaks.”
Sheridan’s Testing Plan
Sheridan’s most recent required tests for pentachlorophenol and related compounds—conducted in September and October 2025—found no reportable level in drinking water. The city’s decision to conduct additional testing represents a choice to go beyond required regulatory monitoring.
Sheridan is consulting with environmental researchers at Oregon State University and state regulators on testing methodology. The city plans to test for both pentachlorophenol and DCOIT in the summer, when it is more likely to draw drinking water from the river. The effort is estimated to cost around $6,000.
The EPA’s cleanup plan for contamination near the drainage ditches where Stella-Jones discharges water is expected to be published in the second half of 2026.
Nina Bell, an attorney and founder of Northwest Environmental Advocates, cautioned that municipal testing focused on drinking water may not address broader ecosystem impacts.
“It would be unfortunate, I think, if it were determined that drinking water is not hazardous and they then cease to be concerned about the rest of the contamination,” Bell said. “Because, obviously, there are high levels of toxics that are going to affect something, even if they don’t affect the drinking water.”
As part of its August 2025 plea agreement, Stella-Jones agreed to remove contaminated sediment from the drainage ditch flowing to the South Yamhill and is required to submit a progress report to state prosecutors by March 2026.