"If you see large barges on the lake, this is what is happening." That was the City of Lake Stevens' whole explanation when its last alum treatment started on November 8, 2022. The work ran through the end of that week.
Four years later, another round is on the calendar. The City's November 2 Splash! update said consultants would treat the lake with alum to help control algal blooms during the second week of November, the week of November 9. The Davies Beach boat launch closes for one to two days during the treatment, and the City said it would announce exact dates with mailed notices and signs posted around the lake.
This treatment is routine upkeep for a lake that has relied on alum for more than a decade. It comes back now at the far end of the City's schedule, a few months after a spring algae advisory, and at the same moment the City Council is weighing how much lakefront owners should pay for it.
The machine the barges replaced
Before alum, Lake Stevens relied on a hypolimnetic aerator. According to a 2018 Snohomish County water quality update, it was installed in 1994. It pumped oxygen into the deep bottom water so phosphorus stayed locked in the sediment instead of feeding algae. The County says it was retired in 2012 as less effective and costly to operate.
The City's 2013 Phosphorus Management Plan describes how it ended. The float that supported the aerator failed in 2012, temporary repairs didn't get it running again, and a full repair was estimated at more than $100,000. That plan set up the replacement. It budgeted $100,000 a year for alum: $81,000 for the chemical and its application, $4,000 for permitting, $5,000 for monitoring and $10,000 for planning and administration. The money was to come from what used to be the aerator's operating and capital funds.
Alum does the same job by different means. The aerator kept phosphorus bound with oxygen. Alum binds it chemically. The goal hasn't changed since 1994: keep the nutrient that feeds algae out of the water column.
What a decade of treatments did to the water
The City hired Tetra Tech to measure whether the switch worked, and the 2022 Alum Treatment Effectiveness Study lays out the record:
- June 2013: the first alum treatment goes onto the lake.
- 2013 through 2020: treatments continue every year. Beginning in 2016 they move from spring to fall.
- Volume: 430,000 gallons applied over that stretch, usually at a dose of 0.15 mg of aluminum per liter, with 2020 at 0.12.
- 2021: a sediment-core study recommends keeping alum but applying it every other year.
- 2022: the most recent treatment, recorded in the City's 2023 Surface Water Management Program.
The outcome is easiest to see in phosphorus. In 2007 through 2012, the last years of aeration, summer phosphorus in the upper water averaged 12.8 micrograms per liter. In 2013 through 2021, the alum years, it averaged 7.0. That is a drop of roughly 45 percent. The study says the lake moved from mesotrophic, a moderately nutrient-rich state, to oligotrophic, the clearer, lower-nutrient end of the scale.
The bloom record moved too. The study logs occasional nuisance cyanobacteria since 2007 and toxic blooms in the winters of 2011, 2013 and 2015. It records no reported blooms after May 2016, through the end of its data in 2021.
The schedule stretched, and spring brought an advisory
Since the annual treatments ended, the gaps have grown. In February 2026 the City filed a SEPA notice with the Washington Department of Ecology for its Lake Stevens Aquatic Plant and Algae Management program. It calls for alum every two to four years to control toxic and non-toxic blooms, applied by a licensed applicator under Ecology's general permit. Lake monitoring and plant surveys guide the timing.
Coming four years after November 2022, this treatment falls at the outer edge of that window. In between, the City's spring Splash! update carried this notice:
"Due to increased algae activity, the City of Lake Stevens is advising a 'when in doubt, stay out' approach at Davies Beach and along the western shores of Lake Stevens. Some algae can be harmful to people and pets. If water looks scummy, discolored, or has a strong odor, avoid contact."
At a February 24 council briefing, City environmental staff described the lake as generally healthy, kept alum as the main management tool, and put a treatment's cost at about $150,000 to $200,000, according to a Citizen Portal summary of the meeting. The 2013 plan budgeted $100,000 every year. The current approach costs more per treatment but happens less often.
Don't mix this treatment up with the one in July. On July 28 the City treated the lake for Eurasian milfoil, curly-leaf pondweed and dense nuisance plants near public beaches. The City's notice for that treatment carried a 24-hour swimming precaution and a 48-hour irrigation precaution. Those precautions applied to that plant treatment. For the alum work, the mailed notices and the shoreline signs are the City's guidance.
Who pays for a clear lake is now on the council's table
The treatment arrives two weeks after the City Council took up a question that reaches every lakefront parcel. At the October 27 meeting, Deputy Public Works Director Shannon Frant and consultant FCS presented a draft surface-water utility rate study and a set of lake-management benefit assessment options, according to Citizen Portal's account of the meeting.
The figures in that account:
| Charge | Current | Range discussed Oct. 27 |
|---|---|---|
| Typical residential stormwater fee | $281 a year under current policy | Three rate scenarios, labeled Level 1 through Level 3 |
| Lake-management benefit assessment on lakefront parcels | $192 a year | Up to $545 a year by 2031 under full cost recovery |
Citizen Portal reported that council members and residents debated the assessment options. The figures are proposals in a draft study, not adopted rates. For scale, the City's initial 2026 budget estimated $5.45 million in surface-water fee revenue for 2026 and noted that those fees are restricted to the stormwater utility.
The budget hearings are on a separate track and run at the same time. The City scheduled the first for November 10 to take testimony on proposed 2027 General Fund revenue sources, including property taxes. The second is Tuesday, November 17, at 6 p.m. in the Sawyers Room at The Mill, 1808 Main Street, and on Zoom. That one takes testimony on the 2027 proposed budget as a whole. Written comments go to the City Clerk at [email protected] before the hearing.
Around the shoreline this month
The alum treatment isn't the only City project at the water's edge this fall. Here is what the City has posted for each spot:
- Davies Beach boat launch: closes for one to two days during the alum treatment. The City's annual launch pass, $75 a year or $60 for Lake Stevens residents, works at both Davies Beach and the North Cove boat launch.
- Davies Beach dock: the City set a September 21 start for resurfacing, with a closure of about 30 days. The old decking is being replaced with wood and pultruded fiberglass, which lets light through to the water below.
- Bayview Trail at West Lake Park: 12th Street SE between 87th and 89th Avenues SE is closed through a tentative end date of November 13. Crews are replacing the sidewalk with a 10-foot multi-use path that connects the existing Bayview Trail at West Lake Park to the next phase, which will run the paved trail from 12th Street SE to 8th Street SE. Pedestrians can still get through.
Questions about the treatment go to [email protected]. Public Works handles the trail closure at 425-622-9403.
This post is general information about public proposals and City notices, not legal, tax or financial advice. Lakefront owners should check how any assessment would apply to their parcel with the City or the right professional.
If you own on the lake and want to talk through what the City's lake program means for your property, the team at First And Main follows these decisions closely and is glad to sit down with you. Book an appointment and bring your questions about the shoreline.
