Milestone: No herbicides detected in Tahoe Keys final test area

Submitted to the Tribune
One of the Tahoe Keys turbidity curtains before being removed.

SOUTH LAKE TAHOE, Calif. — The project to test innovative methods to control the largest infestation of aquatic invasive weeds in the Tahoe Basin reached another milestone this week, officials announced Friday. 

Tahoe Keys Property Owners Association monitoring showed that herbicides were no longer present in the Area A test location and on Thursday divers removed the rubber barriers, called turbidity curtains, that since May had sealed off the test area to restrict herbicide movement. 

This ends all boating restrictions in the Tahoe Keys lagoons and marks the successful end of the herbicide portion of a rigorous, three-year Control Methods Test project. 

The test is the first of its kind in the United States and must meet high standards of safety, due in part to the designation of Lake Tahoe as an Outstanding National Resource Water. 

Years two and three of the project will focus on UV-C light treatment, laminar flow aeration, and other non-chemical methods such as diver hand pulling, with extensive monitoring to help create long-term management plans to battle the aquatic invasive weeds. No additional herbicide applications or boating restrictions will be part of the test moving forward. 

The project team next week will release the first report on the test project. The report will provide a summary of the activities that occurred in summer 2022 and will be available at

The three-year field test project was preceded by a multi-year collaborative public planning process and extensive environmental review by the Tahoe Regional Planning Agency and Lahontan Regional Water Quality Control Board. On May 25, TKPOA began trials of EPA-approved herbicides, followed by UV-C light treatments. 

The League to Save Lake Tahoe is monitoring the multi-year laminar flow aeration program, which is a technology that releases small air bubbles through sediments in the lagoon bottoms to stimulate biological activity and reduce plant growth in designated test areas. TRPA simultaneously launched independent rigorous monitoring for the project to collect data on the efficacy of treatments, water quality, and overall data on how the natural environment responds to the various treatments.

“This test project is producing an incredible amount of data that will help inform how we tackle the largest aquatic weed infestation in the lake,” TRPA Invasive Species Program Manager Dennis Zabaglo said. “It is encouraging to see this project move ahead after many years of planning and collaboration.”  

“After a promising start, the next two years focus on testing a range of innovative and proven weed control methods, including UV-C light and laminar flow aeration,” said Jesse Patterson, chief strategy officer for The League. “By evaluating every possible tool we have in one comprehensive test, the CMT can give us a formula for controlling ground zero for invasive weeds in Tahoe. And with that, we can protect the whole lake.”

Learn more about the CMT project at

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