The public will have a chance to provide input for a proposed plan to revamp La Conner’s 50-year-old wastewater treatment plant this month before the La Conner Town Council convenes for a vote.
A preliminary project plan, developed by Bellingham-based Wilson Engineering and funded by the Washington State Department of Ecology, was released in September and looks into different options to address the facility’s aging infrastructure, as well as future capacity needs and anticipated changes in environmental standards.
A public hearing about the determination of nonsignificance for the plan will take place at 6:00 p.m. on Nov. 25 at Maple Hall. Town will seek input on the plan itself at a later date.
Town Administrator Scott Thomas said the current facility “has been a good investment” for the town.
“Now that it is time to upgrade that facility, we want to carefully consider our options so that the rebuilt facility lasts at least until 2075,” he wrote in an email.
While there is no exact construction timeline, the plan assumes that significant upgrades will be completed in 2028.
Membrane bioreactor conversion favored
The engineering firm recommends converting the current oxidation ditch system into a membrane bioreactor conversion — or MBR — system that would continue to serve the Town and the Swinomish Indian Tribal Community, including the Swinomish Village, Westshore and the Hope Island area.
The two other design alternatives that were evaluated in the study include upgrading the existing oxidation ditch system or transforming it into an aerobic granular sludge conversion system, which are slightly more expensive to build but slightly cheaper to maintain and operate, according to a cost comparison table included in the plan.
Scott Wilson, the principal engineer in charge of the study, said oxidation ditch systems are effective but MBR systems perform significantly better and produce much cleaner water.
He explained MBRs use, among other processes, a membrane with holes so thin that the wastewater filtered through comes out “very clean,” but added that “slightly higher” electrical costs can be a disadvantage when compared to oxidation ditch systems.
Thomas said the recommendation is not surprising as Evan Henke, the town’s former engineer, had also suggested the treatment plant transition to an MBR system. Additionally, he has seen many plants convert to MBR systems in recent years.
“With (the Department of Ecology)’s focus on nutrient reduction, it seems likely that standards will continue to be more stringent and therefore an MBR makes sense so that we can avoid having to make further costly improvements a short time later,” he wrote.
Water quality at issue
While the Department of Ecology has not documented any water quality impairments associated with the plant in the Swinomish Channel, there have been some exceedances, including, between February and April 2024, seven instances of violating the average monthly concentration of ammonia and four instances of violating daily limits, according to the plan.
High levels of ammonia are toxic to aquatic organisms and can be fatal to them, the Environmental Protection Agency reports.
Cost breakdown
The study identified the MBR system as the most advantageous for its “competitive” capital costs, projected to be around $19.98 million to serve La Conner and the Swinomish Tribe, with the Town covering about $13.386 million of that amount. Maintenance and operation would cost around $706,000 every year, $473,000 of which would be contributed by the Town.
The proposed plant’s 20-year life cycle cost is projected to reach a total of $33.39 million. The Town would need to find ways to increase revenue and afford its $22.371 million share of this price tag.
The 20-year planning period is typical for sewer plans, Wilson wrote in an email, but expects the plant will “very likely” last much longer than 20 years, “likely closer to 30 years depending on growth, maintenance, and regulations.”
As reported by the plan, the Town anticipates total expenses ranging from $83 million to $102 million over the next 20 years, while revenue projections for that same period range from $78 million to $95 million, depending on grant awards and loan forgiveness.
The Town might begin discussing the possibility of increasing sewer rates after a vote, though Mayor Marna Hanneman said this would require a lengthy series of meetings before the council makes a decision.
Tribal partnership could offset costs
A 4.5% annual sewer rate increase from 2026 to 2031 would increase revenue to roughly $93.5 million, closing the anticipated funding gap, the plan reports.
The Town does not qualify for financial hardship assistance from the Department of Ecology but is planning to conduct an income survey that would also include the Swinomish Indian Tribal Community. This might help the Town qualify for up to 50% loan forgiveness or grants of up to $5 million, according to the plan.
The Tribe has been sending its wastewater to the La Conner plant since 1984 and its flows are nearing their contracted limits. According to the plan, the Tribe has been considering the possibility of building its own wastewater treatment plant.
The study also evaluated scenarios in which the plant would take waste from La Conner only, as well as the idea of serving Shelter Bay in addition to the Town and the Tribe.
The Tribe did not respond to a request for comment, though Wilson said there has been communication between the firm, the Town and the consultants that the Tribe hired to conduct its own evaluations.
Luisa Loi is a general assignment reporter for La Conner Community News.
Correction: A previous version of this story inaccurately stated community members would provide feedback on a proposed plan to improve La Conner’s Wastewater Treatment Plant at a Nov. 25 public hearing. The meeting will actually be an opportunity to share comments about the determination of nonsignificance for the plan, while the plan itself will be discussed at a later date.
