Tahoe Regional Planning Agency approves invasive weed control methods, including use of herbicide at Tahoe Keys
Submitted by Jeff Munson on Thu, 01/27/2022 - 10:20am
The Tahoe Regional Planning Agency Governing Board voted Wednesday unanimously to certify the Final Environmental Impact Statement and approve the Tahoe Keys Lagoons Aquatic Weed Control Methods Test Project.
Following the Lahontan Water Quality Control Board’s Jan. 13 unanimous vote to approve the project, TRPA’s decision clears the way for a range of proven and innovative weed control methods to be tested in targeted areas within the Tahoe Keys, located on the Lake’s south shore.
“TRPA and the Lahontan Water Board’s unanimous decisions highlight the strong scientific basis for the project’s methods, monitoring and safeguards for Tahoe’s natural environment,” said Darcie Goodman Collins, PhD, CEO of the League to Save Lake Tahoe (Keep Tahoe Blue). “This test will provide essential information for developing a long-term strategy to address the Tahoe Keys infestation and stop its spread to Lake Tahoe.”
An infestation of aquatic invasive weeds in the Tahoe Keys lagoons in South Lake Tahoe is accelerating and poses a serious threat to Lake Tahoe if not controlled, according to TRPA. The Tahoe Keys Property Owners Association proposed the test project in targeted areas of the 170 acres of waterways. The area is approximately seven times greater than all other Lake Tahoe marinas combined.
The unanimous board vote clears the path for a combination of weed treatments including ultraviolet light, a one-time application of EPA-certified aquatic herbicides, and a process to aerate the lagoon bottom with small bubbles to reduce plant growth. The association worked with scientists, community members, environmental agencies, and non-profit organizations in a multi-year collaborative process that was thorough, scientifically rigorous, and inclusive, the agency said.
“If left unchecked, aquatic invasive weeds in any part of Lake Tahoe threaten our entire ecosystem,” TRPA Executive Director Joanne S. Marchetta said. “With climate change increasing water temperatures, we have an urgent need to deploy science-based solutions to combat these emergent threats.”
Aquatic weeds cover more than 90 percent of the Tahoe Keys lagoons and provide sources of continuing infestations around the lake including popular recreation areas like Emerald Bay. Treating the Tahoe Keys lagoons is the number one priority for the multi-agency Lake Tahoe Aquatic Invasive Species Coordinating Committee.
Following decades of failed attempts to control the weeds with conventional methods, in 2017 the Tahoe Keys Property Owners Association applied to water quality agencies for a permit to explore what tools might “knock back” the infestation to a controllable level so it can be maintained by non-herbicidal methods. The environmental analysis determined that Lake Tahoe is not at risk from this test of mixed methods.
“The Tahoe Keys Property Owners Association has been actively managing this weed infestation for over 40 years and has invested millions while the infestation has only gotten worse,” association president David Peterson said. “One method alone is not going to work. For the sake of the entire Lake Tahoe ecosystem, we need to test all tools to address the scale of the invasive species problems in the Tahoe Keys.”
UC Davis professor emeritus Dr. Charles Goldman was among the scientists to speak in support of the project yesterday. “Aquatic herbicides have come a long way and this is the appropriate measure at this time,” he said. Goldman famously sounded the alarm of Lake Tahoe’s declining clarity in the 1960s and his work prompted the states to create the bi-state TRPA to stop harmful development practices.
“Collaboration over the course of many years brought us to this important vote,” TRPA’s Marchetta said. “It’s yet another example that if we trust each other and rely on science, we can collectively make the best decisions to protect Lake Tahoe for future generations.”
Earlier this month, California’s Lahontan Regional Water Quality Control Board voted unanimously to certify the environmental analysis and issue a special permit for the project. Following the approval, testing and monitoring could begin in cordoned areas of the Tahoe Keys lagoons this spring. Learn more about the project at www.tahoekeysweeds.org.
“Environmental study shows that continuing with the status quo, and not testing possible solutions, would result in the worst harm to Lake Tahoe’s water quality,” said Jesse Patterson, the League’s Chief Strategy Officer. “For 65 years, the League has worked to protect water quality, which means tackling the Keys’ infestation is our priority.”
For nearly a decade, the League to Save Lake Tahoe has taken a leadership role in efforts to address the invasive species problem in the Tahoe Keys, which includes helping develop, fund and implement innovative technologies. The Tahoe Keys Property Owners Association and TRPA have dedicated years to the effort and invited the community to get involved, improving the proposed project along the way. The League is a strong supporter of the Control Methods Test, relying on the best available science, results from their pilot projects, and investigations into emerging methods to guide their position.
“We will monitor the project closely and raise a red flag if the health of the Lake or those who enjoy it is ever in question,” said the League’s Goodman Collins. “We’ll also continue using our full set of tools to keep weeds contained in the Keys, and knock back infestations that pop up in the Lake.”
