Lahontan Water Board approves testing of herbicides and non-chemical treatments for Tahoe Keys

Laney Griffo

SOUTH LAKE TAHOE, Calif. – In an effort to control invasive aquatic weeds that could threaten water quality in Lake Tahoe, the Lahontan Regional Water Quality Control Board took action last Thursday to allow for the testing of chemical and non-chemical treatment methods on aquatic weed infestations within the Tahoe Keys Lagoons.

The meeting was continued into the second day due to large numbers of public comments.

“The Tahoe Keys Lagoons holds the largest infestation of aquatic invasive weeds in Lake Tahoe,” said Mike Plaziak, executive officer of the Lahontan Water Board in a press release. “The board’s decision today will help experts determine the most effective means of weed eradication before the infestation outpaces our ability to deal with the issue.”

The controls method test (CMT) is a three-year test which will use several different techniques to attack and knock-back the aquatic invasive weeds that have been prevalent in the Tahoe Keys since the 1980s.

Year one will include a one-time use of herbicides, as well as laminar flow aeration and ultraviolet light. Laminar flow aeration bubbles air through several diffusers on the bottom of the lagoons which causes the water to circulate, increasing the amount of oxygen at the bottom of the lagoons. The goal after year one is for the weeds to be knocked back by 75%.

Years two and three will continue using laminar flow aeration and ultraviolet light, as well as bubble curtains and bottom barriers. Those years will not include the use of herbicides.

The board meeting started on Wednesday Jan. 12 but due to the amount of public comment, it had to be continued into the next day.

Public comment consisted of an almost even split of support and opposition of the plan, and most of the opposition centered on the use of herbicides specifically.

One large concern for the community is that if herbicides can be approved for use once, it opens the door for them to be approved again in the future.

Sierra Club Tahoe has been one of the biggest opponents of the test. Tobi Tyler, a member of Sierra Club’s board, noted that these methods don’t address the root issues which include unnatural lagoon configuration, stagnant water, and nutrient build-up from South Lake Tahoe and Tahoe Keys stormwater.

Another member of the public, Elise Fett, echoed Tyler’s comments, referring to the methods test as “band aids.”

“Focus has been on killing weeds, not mitigating and eliminating nutrient sources,” Fett said.

Fett added that fertilizers are not banned for Tahoe Keys lawns, so those nutrients continue to flow into the water, providing nutrition for the aquatic invasive weeds.

After hearing nearly seven hours of public comment, the board voted unanimously to approve the CMT.

The board adopted a National Pollution Discharge Elimination System (NPDES) permit for the Tahoe Keys Property Owners Association and an exemption to the aquatic pesticide discharge prohibition in the Water Quality Control Plan for the Lahontan Region.

A press release from the water board said, “The authorization is narrow, allowing for the discharge of the herbicides triclopyr and endothall on a one-time basis only to reduce weed populations to levels that can be managed with non-chemical methods.”

“In reaching its decision, the board considered input from many stakeholders and ultimately made a decision that supports a forward-looking approach using the best available science, while upholding our duties to protect water quality in Lake Tahoe,” said Plaziak.

The League to Save Lake Tahoe is one of TKPOA’s partners in developing the plan. The non-profit released a statement from Darcie Goodman Collins, PhD, CEO following approval of the plan.

“To Keep Tahoe Blue, we urgently need to solve the invasive species problem in the Tahoe Keys. This morning’s approval of the Tahoe Keys Control Methods Test puts us on the right path. The unanimous decision by the Lahontan board recognizes the rigorous scientific basis, innovative design and strict environmental safeguards of the test, which were crucial to earning the League’s support,” Collins said.

The statement continued, “For nearly a decade, the League has been a leader, working tirelessly to develop solutions, but also to find common ground for battling invasive species in the Tahoe Keys with all key stakeholders. Years of dedication from the Tahoe Keys Property Owners Association, Lahontan, the Tahoe Regional Planning Agency and members of the community helped get us to this point, where we are poised to learn from the wide range of tools and approaches in the Control Methods Test. The League will continue to collaborate to solve the problem in the Keys and protect Tahoe’s water quality.”

The plan still needs to be approved by the Tahoe Regional Planning Agency during the TRPA Governing Board Meeting on January 26, 2022. While the decision does not lie on TRPA Executive Director Joanne S. Marchetta’s shoulder, Marchetta has been openly in-support of the plan.

“This is not a TKPOA problem, this is a lake-wide issue,” said Marchetta in a press release. “We’ve seen public and private partners come together to improve and fund elements of this environmental process because everyone understands that we are at a tipping point. The results of this decision will influence the future of Lake Tahoe for years to come.”

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