The former site of a Weyerhaeuser mill along the Snohomish River in north Everett is covered by grass and a parking area (center) used by an adjacent Amazon warehouse. (Chuck Taylor / The Herald)

The former site of a Weyerhaeuser mill along the Snohomish River in north Everett is covered by grass and a parking area (center) used by an adjacent Amazon warehouse. (Chuck Taylor / The Herald)

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Is pollution at old mill site reaching the Snohomish River?

Over 20 years after an initial cleanup, the state isn’t sure arsenic on a 9-acre lot is contained.

EVERETT — There’s not enough data to show if contamination from a former mill site in Everett is leaking into the Snohomish River, according to the state Department of Ecology.

The state made that call in 2016, but just this week announced a plan to take a closer look at the 9 acres just southeast of the Highway 529 bridge between Everett and Marysville.

“Due to workload issues and various other issues we haven’t pursued any more active cleanup activities,” said Ron Timm, cleanup project manager with the Department of Ecology.

The land was first cleaned up by former owners in 1999. Since then, Ecology has reviewed the site every five years on top of annual monitoring.

Now Ecology is calling for a year-long study to determine if arsenic in the soil is at risk of reaching the Snohomish River.

“It’s still not certain that we need to be concerned about the containment,” Timm said. “We just need more evidence to confirm it.”

In its Mill Town days, Everett’s waterfronts were lined with industrial plants churning out pulp, lumber, and other products.

Today, most of those buildings are gone, but some environmental impacts of their operations linger.

To the west, crews are set to kick off cleanup of the 60-acre Kimberly-Clark site near the Port of Everett.

To the east, the proposed pollution study would take place along the Snohomish River, where the Weyerhaeuser Co. mill operations once stretched along its banks.

As mill operations began to slow down in the mid-1900s, Weyerhaeuser leased the 9-acre site to American Lumber and Treating Corporation. The company treated lumber there using arsenic, a pesticide called Pentachlorophenol, petroleum and other chemicals.

“Which is when the problems started,” Timm said.

The land changed hands a few more times to an engine maintenance shop, sawmill and wood pallet storage throughout the years. Today, it’s zoned as heavy industrial and is used as overflow parking and storage for the nearby Amazon distribution center.

Ecology sued Weyerhaeuser in 1998, leading to a settlement that required Weyerhaeuser to clean up the Snohomish River site.

While petroleum and some of the other contaminants present will break down over time — arsenic will not, Timm said.

So in 1999 Weyerhaeuser paved about four acres to trap arsenic in the soil.

Asphalt reduces rainfall infiltration, which helps reduce the chance arsenic will leach.

“…But when you have other chemicals in the soup it tends to want to be mobile,” Timm said. “It’s a very unpredictable chemical and it doesn’t usually break down, it just changes forms.”

In 2016, Ecology wasn’t convinced the arsenic was sufficiently contained.

Now they’re asking current owner M.A.P. #2, LLC and past owners of the land to collect more data.

“The soil has been covered so there’s no real threat to human health through direct contact,” Timm said. “It’s just how the contaminates could still be moving through groundwater and getting to the river sediments.”

Over the next year, Seattle environmental consulting agency Floyd|Snider will test groundwater and soil at the site four times, once each season. To do so, they’ll dig 10 groundwater monitoring wells and five soil probes in other parts of the lot.

The full work plan is open for public comment through July 21.

Once the year-long data collection period is complete, Ecology will determine a path forward.

“One of the concerns we’ve had in the past is that we didn’t have a thorough knowledge of what was going on at the site,” Timm said. “We want to solve that problem and collect as much data as we can to fully understand (it).”

How to comment

To make public comment, visit the state Department of Ecology’s website at or email You may also mail comments to: Dept. of Ecology; Attn Ronald Timm, Site Manager; 3190 160th Ave. SE; Bellevue WA 98008-5452.

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