Tobi Tyler: Herbicides in Lake Tahoe – A dangerous proposition

In mid-September, the Lahontan Regional Water Quality Control Board released a draft permit that would allow the Tahoe Keys Property Owners Association to apply aquatic herbicides for the very first time in the Tahoe Keys lagoons, which are connected to Lake Tahoe.

For decades, invasive aquatic weeds in the Tahoe Keys have been growing in the stagnant Tahoe Keys lagoons, which are fertilized by nutrients in stormwater pouring in from Keys residences and the nearby community. In addition, decades of attempts by TKPOA to reduce the weeds by mowing them have made the problem worse. Boats from the Keys have spread weed fragments (which can sprout into new plants) around the lake, creating new infestations. Now the weeds are out of control and threatening the health of Lake Tahoe, our national treasure. TKPOA is proposing to poison the lagoons without having first addressed the conditions in the Keys lagoons that promote weed growth and without having exhaustively tested non-chemical control methods.

TKPOA has made many claims about the need for their proposed one-time use of herbicides in the lagoons. However, numerous questions remain unanswered:

Why are the permitting agencies (Lahontan Regional Water Quality Control Board and Tahoe Regional Planning Agency) insisting on using herbicides when the draft environmental document clearly stated that testing non-chemical methods was the environmentally superior alternative?

Everywhere else, single applications of aquatic herbicides don’t successfully control weeds; repeated herbicide applications are required every year. In fact, TKPOA has previously applied for permits for control projects with up to 12 years of herbicide use. Why do TKPOA and the permitting agencies think that herbicide use in the Tahoe Keys would be an exception to the universal need for repeated annual applications? To be clear, herbicides have never been allowed in Lake Tahoe, because the EPA and California classify Tahoe as a Tier III Outstanding National Resource Water that must not be degraded.

Why use herbicides in this “test” project when the repeated use of herbicides going forward would cause degradation that is prohibited by federal regulations that apply to Lake Tahoe?

The answer to these questions is crystal clear: this “test” is TKPOA’s foot-in-the-door to permitting future, on-going, perpetual herbicide treatments, not just at the Keys but potentially elsewhere around the lake.

In proposing to allow this, the permitting agencies are attempting to bypass state and federal regulations with wholly inadequate justifications and analyses. Federal anti-degradation regulations and LWB’s Basin Plan regulations require proof that non-chemical methods don’t work before authorizing chemical methods. This has not been shown, and the draft LWB permit ignores this.

Nutrients from Tahoe Keys lawns and South Lake Tahoe stormwater have been accumulating in the unnatural lagoon waters and bottom sediments, fueling weed growth for 60 years. Herbicides don’t kill the weed turions and seeds (this has been proven elsewhere in the country). The only thing this one-time herbicide test will do is offer Tahoe Keys homeowners false hope for a convenient solution that will allow them to continue boating from their backyards to the lake, which endangers lake clarity and ecosystems by spreading weed infestations.

Everyone’s primary concern should be the health of the lake, which provides us all with clean water, fabled beauty, and supports a multi-billion-dollar tourist economy. LWB and TRPA need to find a longer-term solution to the Keys’ weeds nightmare that actually solves the weed problem, instead of managing it forever by use of herbicides, and which preserves Lake Tahoe’s nationally treasured beauty and clarity.

The TKPOA project applying herbicides is a dangerous proposal that will not benefit Lake Tahoe’s water quality or the public interest. We must demand better solutions. The comment period ends Nov. 1. You can provide comments to

Tobi Tyler is vice chair of the Tahoe Area Group, Sierra Club

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