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Tumwater lake managers propose small trial of microbial treatment after reported biomass drop
Summary
Steering committee heard a lake management report showing large reductions in biomass after recent treatments and discussed a focused trial of a microbial product near Dana's boat launch to test muck reduction; staff will present a detailed acres/cost table at the March 4 meeting.
Dave Congeyser, a staff member who presented the lake's annual monitoring material, told the Tumwater Lake Management District steering committee that maps in the contractor's report show a marked decline in plant biomass after treatment. "You can see we greatly reduced biomass that was there," he said, summarizing before-and-after survey results.
Congeyser recommended limited, spot treatments this coming season rather than a full-lake application and proposed running a small trial of a proprietary microbial product (referred to in the meeting as "Macbiotics" or "NuttBiotics," manufactured by Natural Lakes) near the publicly accessible boat launch on Dana's parcel so results could be measured and shared. He said the microbes work when water temperatures rise above about 55 degrees and would likely be applied monthly through the warmer months if approved. "We're gonna have to update the permit a little bit trying to get those on there," he added.
Committee members asked for more detail on coverage and cost. Congeyser gave a ballpark figure of about $600 per month for a small application area and said that would likely cover roughly a quarter-acre per application; he also emphasized that large-scale application risks local oxygen depletion and fish impacts, which is why the group should start with a small plot. "If it works well, then we can figure out a strategy for future years," one member said.
No formal vote on the trial was taken at this meeting. The committee asked staff to provide a clear table at the March meeting showing proposed acres, number of applications, and estimated costs so members can consider a budget cap and decide whether to authorize a pilot. Congeyser also noted the contractor's spring GPS-based survey missed some very shallow north-end points because the software does not report in extremely shallow water; members agreed to review the full written report before March.
