Protecting Spring Lake

We asked the same question — and pursued the answer thoroughly. In February 2026, the Spring Lake Community Club held a meeting with three King County representatives: the current Aquatic Noxious Weed Specialist, the former Aquatic Noxious Weed Specialist, and the Lake Stewardship Program chairman. Here is what we learned:

King County has no legal mandate to treat Eurasian Watermilfoil. Under Washington State law, the only aquatic weed King County is legally required to control is purple loosestrife. Eurasian milfoil is classified as a "non-regulated noxious weed," meaning landowners and lake communities bear the responsibility — and the cost — of controlling it. The County can sponsor permits and provide technical guidance, but cannot fund the treatment itself.

A state Ecology grant exists, but it wasn’t a realistic option. Washington State Department of Ecology offers grants of up to $75,000 for implementation (with a required community match) and $30,000 for planning. However, applications are due each fall and decisions are announced in February or March — by the time we organized in early 2026, the window had already closed. More importantly, county representatives advised us directly that grant funding for lake weed control has been declining year over year, and that Spring Lake would be unlikely to receive funding even if we applied. Private residential lakes are not a priority in the current grant cycle. Pursuing a grant would have meant waiting until at least summer 2027 with no guarantee of success — another full year of infestation spreading.

We chose to act now. The treatment window for ProcellaCOR is narrow — plants must be actively growing, and WDFW timing restrictions apply. Waiting another year risks further spread around the lake perimeter and into previously unaffected areas. The community voted to self-fund this season’s treatment and pursue grant options in parallel for future years. We are actively exploring a Lake Management District as a long-term funding mechanism so that future treatments don’t rely solely on community fundraising.

Eurasian Watermilfoil has been present in Spring Lake since at least 2001, when King County’s regional survey classified the lake as "moderately infested." The county’s 2002 Regional Eurasian Milfoil Control Plan — co-authored by AquaTechnex, the same firm treating our lake today — identified Spring Lake as a priority for immediate action.

The lake was treated with herbicide in 2002–2003, and the results were remarkable: Spring Lake remained largely milfoil-free for approximately 20 years. This is an encouraging precedent — it demonstrates that a well-executed treatment can deliver lasting protection. Unfortunately, re-infestation is an inherent risk with this species, as fragments spread via boats, trailers, and waterfowl from nearby lakes. By the mid-2020s the milfoil had returned and spread significantly around the lake perimeter.

In early 2026, our community organized, held public meetings, commissioned a new professional survey, and secured a state permit. This treatment is the result of that sustained community effort.

At two community meetings in early 2026, neighbors reviewed all available control options and reached consensus that targeted herbicide treatment is the most effective and practical approach for Spring Lake's level of infestation. The alternatives were evaluated and ruled out for the following reasons:

Mechanical harvesting acts like a lawn mower in the water. It doesn't address the root system, so regrowth is rapid. Worse, Eurasian Watermilfoil spreads aggressively through fragmentation — any small piece cut by a harvester can become a new plant, potentially spreading the infestation to previously unaffected areas of the lake.

Diver-assisted suction harvesting (DASH) is effective for small pioneer infestations but is not economically viable at our scale. A licensed dive crew quoted us a capacity of approximately 2,000 square feet per day at a day rate of $4,000. Given the extent of the milfoil beds mapped around Spring Lake's perimeter, full treatment would require many weeks of work and cost hundreds of thousands of dollars.

King County's own Regional Milfoil Control Plan confirms that systemic herbicide treatment is the appropriate strategy for lakes at Spring Lake's level of infestation, and specifically recommends ProcellaCOR-class treatments for their selectivity and effectiveness.

ProcellaCOR (active ingredient: florpyrauxifen-benzyl) is a systemic aquatic herbicide first registered with the U.S. EPA in 2017. It works by mimicking the plant growth hormone auxin, causing excessive elongation of plant cells throughout the entire plant — including the roots — ultimately killing it. This is critical: unlike contact herbicides or mechanical methods, ProcellaCOR kills the whole plant, not just the above-ground portion.

Initial effects become visible within a few days of treatment, with full plant decomposition occurring over two to three weeks. The herbicide is applied directly into the water at low concentrations by licensed professionals; the effective dose is roughly equivalent to one ounce in a typical swimming pool.

ProcellaCOR is labeled specifically for control of invasive Eurasian Watermilfoil and has an excellent selectivity profile — it targets the invasive milfoil while being far less harmful to many native aquatic plants compared to older generation herbicides.

Yes. According to the Wisconsin DNR's Chemical Fact Sheet and EPA toxicology studies, florpyrauxifen-benzyl is practically nontoxic to freshwater fish, invertebrates, birds, bees, reptiles, amphibians, and mammals. There are no risks of concern to human health — no adverse short- or long-term effects, no carcinogenicity or mutagenicity were observed in toxicological studies. Drinking water exposures do not pose a significant human health risk, and the EPA established no maximum allowable drinking water concentration.

The product has a short half-life of 4–6 days in aerobic aquatic environments and breaks down rapidly in sunlight (photolytic half-life of approximately two hours in surface water). It does not persist in groundwater and is not expected to cause environmental impacts beyond the treatment area.

Swimming & fishing: No restrictions on the federal EPA label. Out of caution, we recommend avoiding swimming directly in treatment areas for 24 hours after application.

Drinking water: No restrictions. ProcellaCOR has been authorized for use in public drinking water supplies.

Turf irrigation: No restrictions — established lawns can be irrigated immediately.

Non-turf / food crop irrigation: Treated water should not be used for non-agricultural irrigation for a short waiting period (dependent on application rate), typically around 14 days or until the active ingredient dissipates to non-detectable levels.

Livestock watering: Treated water should not be used for livestock drinking water or agricultural irrigation. This restriction does not apply to household pets.

AquaTechnex will post public notices on docks and at the boat launch before treatment and will provide specific guidance on exact timelines as part of their permit compliance process.

Possibly not — and we want to be transparent about that. King County's Regional Milfoil Plan and decades of lake management experience in the Pacific Northwest show that while a single treatment can dramatically reduce an infestation, follow-up treatments in subsequent seasons are often needed to address regrowth from the seed bank or re-introduction from other infested lakes in the area.

The plan also recommends rotating herbicides over time to prevent the development of resistant plant populations. This means long-term management of Spring Lake will likely involve a combination of approaches and ongoing monitoring — not a one-and-done solution.

This is exactly why our fundraising goal includes a $2,000 contingency buffer and why any surplus beyond the $28,000 goal will be held in our Invasive Plant Fund. Think of your contribution as the beginning of a long-term stewardship commitment for Spring Lake, not just a single treatment.

Fragrant Water Lily is a separate species that has also been spreading in Spring Lake and was documented in our 2026 survey. We have now received a quote of $6,000 for a fall treatment, and this is included in our $28,000 fundraising goal. Milfoil treatment is the immediate priority — water lily treatment will proceed this fall as funds allow. Unlike milfoil, Fragrant Water Lily requires a different herbicide and treatment approach, which AquaTechnex will apply under the same state permit.

The treatment is being performed by AquaTechnex, LLC (Centralia, WA), a licensed professional aquatic management firm with deep roots in King County lake management — they co-authored King County's Regional Eurasian Milfoil Control Plan in 2002 and have been working on area lakes for over two decades.

The application is authorized under Washington State Department of Ecology Aquatic Plant and Algae Management (APAM) General Permit #WAG994746, issued July 16, 2026. King County has also been notified and involved throughout the permitting and planning process.