Thurston County Board of Health approves consolidated lakes IPM prescription after public questions about springs and chemicals

Thurston County public health staff and the county's pest and vegetation advisory committee persuaded the Board of Health to approve a consolidated integrated pest management (IPM) prescription for four county lakes — including Long Lake and Lake Lawrence — at the March 11 meeting, following public comment and a detailed staff presentation on alternatives to herbicides.

The board voted to approve the consolidated prescription after staff described the IPM decision process and monitoring requirements. The motion passed; one board member stated they were abstaining during the roll call. Names for each recorded yes vote were not provided in the transcript.

Why it matters: the consolidated prescription establishes a county-level framework that requires lake managers and contractors to evaluate prevention, manual removal, mechanical harvesting and other nonchemical approaches before using contact or systemic aquatic herbicides. Staff and the Pest and Vegetation Management Advisory Committee (PIVMACC) said the policy is intended to protect public health, water quality and recreation while allowing targeted control of nuisance aquatic vegetation.

Environmental Health Supervisor Kimberly Graham told the board the county's IPM policy requires written programs, monitoring, and active-ingredient reviews. “An action threshold … is a point at which pest populations or environmental conditions indicate that pest control action must be taken,” Graham said, adding that chemical controls are used only after other measures fail and that environmental health assigns each active ingredient a rating of “passed,” “conditional,” or “failed.”

Environmental Health Manager Stuart Rickford described the consolidated prescription as a rework of plans used previously in Long Lake and Lake Lawrence and said it requires managers to assess options in an ordered way: manual control, mechanical harvesting, contact herbicides, and — as a last resort — systemic herbicides. Rickford cited nuisance impacts such as impaired water access, hazards to swimmers and boaters, degraded habitat and odors when weed or algae growth becomes excessive.

Public commenters asked questions about local geology, treatment boundaries and product choices. Brent Trowbridge, who provided handouts to the board, said parts of Patterson Lake drain underground toward McAllister Springs and argued some parcels and the railroad trestle area were omitted from maps used in prior planning. He urged increased protection for McAllister Springs and cautioned about certain products listed as “conditional.”

Barry Halverson, a representative of local lake management districts, said his groups had updated prescriptions in 2023 and had briefed county commissioners and the county manager on the need to add specific products — including a formulation referenced in meeting materials — to the county toolkit to address an invasive species that the state lists as a Class C noxious weed.

Rickford said the county maintains contracts with licensed contractors for mechanical harvesting and herbicide application, including pre- and post-application sampling when herbicides are used. He emphasized that glyphosate and other products have documented occupational risks when used incorrectly, but added that, “if glyphosate is used according to its label instructions, then it should have no negative impact.”

Board members asked staff how the county ensures the prescribed decision steps are followed on a site-by-site basis. Graham and Rickford said Long Lake and Lake Lawrence have integrated aquatic vegetation management plans in place, and that state grants are funding development of similar plans for Patterson and Offutt lakes; monitoring and plan updates are part of that process.

The Board approved the consolidated prescription after PIVMACC review. The board's packet and staff presentation identify Grow Smart Grow Safe (the county's public IPM resource), active ingredient review summaries, and monitoring requirements as the basis for the recommendation. The board directed staff to continue monitoring, to update plans when new data require it and to answer detailed mapping questions raised by commenters.

Ending note: staff offered to provide a follow-up response about the specific parcel mapping and how McAllister Springs connections were addressed in the consolidated prescription. The newly adopted prescription can be updated through the plan-do-check-act cycle as monitoring data and lake management plans evolve.