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At the flush of a toilet, sewage is out of sight, out of mind for most Lynnwood residents. But that might not be the case for long.
It’s been over 30 years since the Lynnwood Wastewater Treatment Plant updated or increased capacity on some of its vital systems. In that time, the city’s population grew from around 28,000 to nearly 38,000 in 2020, according to U.S. Census data. Lynnwood’s sewage treatment plant is expected to serve around 54,000 people by 2030, with that number rising to 74,000 in 2050, per city documents.
In an attempt to keep up with sewage demands, Lynnwood unveiled its Lynnwood Wastewater Treatment Plant Facility Plan in 2022. The plan was just approved by the Washington State Department of Ecology, Lynnwood Wastewater Treatment Plant Project Manager Ehsan Shirkhani said at a Lynnwood City Council work session Oct. 7.
In 2022, it was estimated a revamped sewage plant could cost around $250 million and take at least 10 years to complete. Those figures are likely to change in the future, but the “guaranteed maximum price” will be available about 30-60% through the design process, Shirkhani told the council.
During that Oct. 7 report, councilmembers learned that regulatory requirements, capacity and aging equipment are the main drivers for an upgrade at the plant.
Vital systems such as the headworks and the primary clarifiers – systems meant to filter foreign objects out of incoming wastewater – are nearing peak capacity. The city’s solid’s handling process exceeded capacity following equipment failure and unusual weather conditions earlier this year, Lynnwood spokesperson Nathan MacDonald said.
“By doing this upgrade we’re buying the city time for another 20 to 30 years to consider more long term plan and regional level solutions,” Shirkhani said.
Lynnwood has already faced serious delays in operations and multiple fines from the federal government as a result of the plant’s aging equipment.
Earlier this year, Lynnwood paid $550,000 in fines to the Environmental Protection agency after the agency found that the plant’s 60-year-old sewage sludge incinerator was emitting an illegal amount of pollutants into the air.
In August, Lynnwood faced another fine from the EPA – this time paying $4,350 for violations of the Clean Water Act, according to a settlement notice.
The proposed upgrades will commence in phases – a move necessary to keep the plant in operation amid construction. That work will be a challenge “logistically,” Deputy Public Works Director Jared Bond told the council Oct. 7.
“You’re building a new car while you’re driving it, there’s no off switch,” Bond said to the council. “Sewage keeps coming and we have to continue to treat it while we are building new sections. So the phasing is critical on this.”
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Lynnwood Wastewater Treatment Plant upgrade timeline:
2024: Planning.
2025: Pre-design and permitting.
2026-2027: Phase 1 design.
2026-2028: Phase 2 design.
2027-2028: Phase 1 construction.
2028-2031: Phase 2 construction.
2029-2030: Phase 2 design.
2031-2033: Phase 3 construction.
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Despite the challenges ahead, the plant is on track to keep up with rapidly changing local and federal laws and population growth, Lynnwood Wastewater Treatment Plant Supervisor Tanner Boyle said in an interview.
“I think we have a really good plan going over the next 10 years. We have good people in the right spots,” Boyle said.
In the latest move to comply with these requirements, the city has a cleaner way to dispose of solid waste. Following EPA orders, the plant shut off its sewage sludge incinerator in late April. In its place is a modernized system that compresses the solid waste to drain the liquid and ships the remaining matter to a federally approved landfill site in Arlington, Oregon.
The incinerator, originally installed in 1962, was later upgraded in 1993, according to a press release from the city. It was the first of its kind in the United States, city documents say.
The usable lifespan for incinerators like these are about 30 years, Boyle added.
The compliance issue was related to the incinerator’s scrubbers – the part of the machine tasked with removing pollutants from incinerator emissions. In this case, the scrubbers failed to remove the desired amount of pollutants.
Replacing the incinerator was among many tasks necessary to ensure that the sewage treatment plant reaches – or exceeds– its efficient lifespan.
“Due to the age of the facility, major improvements are warranted to rectify the current conditions of the equipment and structures needed to perform vital treatment functions,” the facility plan reads.
Located under the sewage treatment plant, a new headworks system is set to be built uphill from the current one, according to the facility plan. Additionally, the plan recommends the plant add new aeration basins and replace the plant’s existing effluent chlorination system, among other improvements.
The wastewater treatment plant facility plan has been in the works since 2020, when the city contacted RH2 Engineering and BHC Consultants to look into the state of the plant.
Lynnwood officials and residents say a sewage treatment plant expansion has been needed for some time.
During his run for Lynnwood City Council in 2023, David Parshall said he was concerned about the sewage plant’s incinerator. This was weeks before the EPA fined the city for the incinerator’s air quality violations.
“We’re a smaller but rapidly growing city and updating the waste treatment plant represents a significant capital investment,” Parshall said in an email.
When he took office in January, Councilmember Parshall said he joined other city officials to “lobby federal, state, and county representatives for investments in a new cleaner and greener treatment plant.”
Eventually, Parshall said he would like to see the city put its solid waste to use.
“I mentioned to you last October that I would love to see the city be able to convert its biosolids into fertilizer grade material,” he wrote. “…With a new treatment plant we may be able to sell fertilizer for agricultural uses instead of seeing it go into a landfill. As I said last year, we can do the environment a double favor by ceasing carbon emissions from incineration and instead create useful fertilizers for farmers.”
Those living near the plant have reported a sewage smell that appeared earlier this summer, City Council President George Hurst said at the Oct. 7 meeting.
It was unclear whether the smell came from the plant or from an unrelated origin. Odor tests were done in and around the plant, and didn’t show any signs of odor outside of the plant, Boyle said in an email response to the complaints.
“We have done odor testing with our hydrogen sulfide meter to get a baseline and any time we get complaints we also do testing. Treating odors is no easy feat, It’s a step-by-step process to see what works, what doesn’t, and let the process of reducing odors run its course,” Boyle said.
To mitigate the smells, solid waste containers are removed from the plant as soon as possible, including weekends and holidays, Boyle said. Additionally, plant staff changed deodorizing levels and worked with the Department of Ecology and another company to find the “best approach to treat excess odors.”
“The staff here is working their hardest to do what’s best for our community,” Boyle wrote. The plant’s outflow to Puget Sound is the cleanest he’s seen in “some time” based on the data they’ve collected.
“I wish it was as easy as flipping a switch to shut off any excess odors but these things take time,” Boyle continued. “I appreciate all the neighbors that have voiced their concerns and been patient with us as we figure out what’s best for everyone.”
— By Ashley Nash
Thank you Ashley for the research. I think all the neighbors affected my the sewage smells this summer would agree it was not from another source. True there could have been smells from the sea lettuce baking on the beach on a very hot day, but that is not what neighbors consistently complain about. The smell is still there off and on, but now more mild.
My concern, moving forward in upgrading the plant, is how the disruption will affect the neighbors and what kind of smells might develop. We are happy there is admittance that the plant cannot treat all the sewage due to Lynnwood’s growth. I am happy that after living next door to the plant, now 29 years, that the city is actually forced to upgrade the plant. I am not looking forward to the next 10 years of construction.