Otherwise, progress on closing the former Go East Corp. landfill appears to be on track.
On Sept. 17 or 18, after water saturated the ground, part of a slope gave way and sent up to 700 cubic yards of dirt down the hillside, partially burying two excavators.
An estimated two feet of fill covered about an acre of land, extending across a wetland and to a stream, and touching properties north and east of the site, including a greenbelt owned by nearby homeowner associations, as well as an easement corridor for the Olympic Pipe Line Co.
No one was hurt in the mudslide and the excavators have since been recovered. And despite persistent heavy rainfall in November, no other slides have been reported.
The Snohomish Health District determined the slide consisted of a loose sandy material that contractors brought in to build an access path. It’s clean, the agency said, and no contaminants from the landfill itself have been identified.
The weight and rumbling of heavy equipment likely helped trigger the slide, according to the health district, which is overseeing the landfill’s closure.
On Sept. 23, the county issued a notice, requiring the owner, now called P&GE, to take immediate measures to assess and correct slope stability conditions. Geotechnical engineers were brought in to help with that.
The state Department of Ecology is investigating to see if the mudslide has affected the stream or wetlands.
A little bit of oil leaked from the excavators, as well, Ecology spokesperson Curt Hart said. Crews sopped it up with absorbent pads.
“Whatever happened it wasn’t a large spill,” Hart said.
Work was underway again shortly after the slide.
Crews condensed the landfill to 6.4 acres, down from 9.6 acres, and covered it with an impermeable cap to keep methane gasses from leaking.
Now, contractors are adding two feet of cover soil, installing a gas collection system and preparing to drill groundwater monitoring wells, according to the health district.
Eventually, nearly 100 homes will be built around the closed landfill. It will be called the Bakerview subdivision.
The 40-acre property east of Silver Lake became a landfill in the 1970s, first for construction debris, then for wood waste. Two fires broke out, in 1977 and in 1983. The latter smoldered for three years.
The site hasn’t been used as a landfill since 1983, when Go East Corp. stopped accepting wood waste. The company’s owner, Gary East, formed P&GE in 2009 to develop the property into housing.
When the landfill closed nearly 40 years ago, the owners covered it with two feet of soil. That’s all regulations required at the time. That sandy soil allowed methane gas generated by decaying wood to escape, according to the Department of Ecology. The Go East landfill doesn’t emit as much methane as ones used for human-generated trash.
Neighbors fought the Bakerview subdivision for over a decade, believing the plans didn’t go far enough to protect human and environmental health. Opponents argued there wasn’t enough data to prove landfill contaminants wouldn’t leach into the Snohomish River, and didn’t trust the developer’s methane collection system to prevent gas from leaking into houses built just a few feet from the landfill’s remnants.
Neighborhood associations appealed the project every step of the way, until the final permits were approved in 2019.
As part of a remedial investigation plan, crews will conduct further soil and water testing once the landfill closure is complete, to make sure hazardous materials don’t exceed regulatory limits. Monitoring for contaminants will be an ongoing effort.
This story has been modified to show the correct date the mudslide occurred.