Tumwater LMD amends scope to add full-lake fluridone treatment for Barnes Lake

The Tumwater Lake Management District (LMD) steering committee voted to amend the contractor scope of work to include a full-lake fluridone (Sonar) treatment for Barnes Lake and a subsequent ClearCast application to address nuisance emergent plants such as water shield and white water lily.

The committee approved the change by voice vote after staff recommended the two-step approach. Consultant Scott told the panel, “I am recommending for the sonar treatment for, this year, instead of doing the aquifol or the diquat, but still doing, the clear cast for, water shield and white water lily.”

The change shifts the LMD’s recommended primary systemic treatment from spot or contact herbicides to fluridone, a systemic product marketed as Sonar. Committee members discussed operational and environmental implications before voting. Participants raised concerns that pellet-style or other treatments could release carbon dioxide and reduce dissolved oxygen — a particular risk in shallow portions of the lake — and urged caution about applying systemic products to very shallow or highly mixed areas.

Staff said the amended scope will also note the operational need for two applications so the treatment can maintain an effective concentration for the required period (discussants described maintaining a target concentration for roughly 30 consecutive days). Scott and staff also advised that application timing would depend on permitting and scheduling with the contractor; the group discussed likely treatment windows in May for surveys and initial treatment and a later-season follow-up.

Next steps: staff will draft a written amendment to the current contract/scope of work, include a more detailed budget estimate for the fluridone and ClearCast work, and circulate it to committee members. Scott said, “I’ll try to get that to you by next week,” and the committee agreed to review the amendment and either hold a short Zoom meeting (15 minutes) on Feb. 12 or Feb. 19 or to approve electronically so the project can be put into the contractor’s scheduling queue. Committee members repeatedly noted that a green light by March would be necessary to secure timely treatment scheduling.

The committee also directed staff to confirm permit implications. Members noted that switching to a full-lake fluridone application will require amending the existing permit and completing or updating a lake treatment plan (staff referred to this as a treatment management plan) before large-area applications can proceed.

The motion to amend the scope of work to include fluridone (Sonar) full-lake treatment and subsequent ClearCast application for emergent plants was moved by committee member Kathy and seconded (second name not specified in the record). The motion passed in a voice vote; the meeting record shows the motion approved but does not list a roll-call tally.

Committee members also discussed trial locations and cautioned starting in narrow, shallow channels or smaller neighboring lakes before treating large sections of Barnes Lake. Suggested trial sites included the narrow channel between the north basin and main part of Long Lake, parts of Lake Lawrence, and the Lorna Canal where sediments concentrate. Staff said they would attempt to identify a local site with relevant conditions and include any monitoring or mitigation language in the scope of work.

Other business noted during the meeting included a planned RFQ for the IVAMP update (staff said $15,000 is budgeted as a placeholder), continued work on the 2025 annual work plan and budget, boat-launch temporary solutions while a signature is pending, and clarifications requested on the draft budget tables that staff said they would correct before submission to the city council. Those items were discussed but not decided as part of the scope amendment vote.

The committee recorded the amendment as documented guidance to proceed with drafting the contract change; staff will return the written scope and budget for committee review and approval prior to authorizing contractor work.