Breaking News
More () »

Deep Debate | Poisons tested at Lake Tahoe

A controversial test to poison invasive underwater weeds is dividing people and environmental groups in Lake Tahoe.

SOUTH LAKE TAHOE, Calif. — Locals and environmental groups are split over a plan to respond to one of the most serious environmental problems in Lake Tahoe with a controversial solution: poison.

Similar to using chemotherapy to kill cancer cells, authorities approved a test of chemical herbicides to kill underwater weeds threatening to ruin Tahoe’s shoreline if left unchecked.

Herbicides triclopyr and endothall were applied last year to developed lagoons connected to the lake in a subdivision known as the Tahoe Keys. The test could lead to a larger-scale application of herbicides.

“This was wrong,” said Tobi Tyler, a volunteer with the Sierra Club, which sued the Lahontan Water Board for approving the test. “This was very wrong, this project.”

The League to Save Lake Tahoe, known for its “Keep Tahoe Blue” bumper sticker, has taken the opposite position. It endorsed the Tahoe Keys herbicide test.

“You have to be pragmatic about what's possible politically,” said league representative Jesse Patterson. “The biggest threat to keeping Tahoe Blue, instead of it turning green, is this development.”

Supporters point to climate change as part of the reason herbicides must be considered: the invasive aquatic plants have spread around the lake in recent years, something that happens more easily when water gets warmer.

Opponents worry about unintended consequences, arguing the idea of using herbicides embodies the same kind of rash thinking that got us into this mess.

There’s little debate about the problem. Both sides see it as an existential threat to Lake Tahoe, brought about by destruction of nature done decades ago in the name of progress.

“This is the biggest ecological disaster in California,” said opponent Laurel Ames, who’s lived at the lake since the 1940s and ran the League to Save Lake Tahoe during the decades when the Tahoe Keys was developed.

“If we were to see a massive infestation around the lake, we could potentially lose the lake,” said Jeff Cowen with the bi-state Tahoe Regional Planning Agency, which supports the herbicide test.


The “cancer” of these weeds isn’t new. It’s progressed slowly for decades, incubating in the damaged remnants of Lake Tahoe’s "lungs."

Lake Tahoe owes its famous deep blue color to a natural water filtration system that created some of the clearest lake water on Earth: 99.994% pure.

As the snowpack high in the Sierra melts each spring, raging rivers carry murky sediment toward the lake. Just as your lungs filter the air you breathe, wetlands filter this water.

Nature blessed Tahoe with large meadows and marshes that slow the flow, allowing sediment to fall out of the water. The biggest marsh in all the Sierra served as a filter for the lake’s largest tributary: the Upper Truckee River.

But today, most of the Upper Truckee Marsh is gone.

“In the 1960s, it was destroyed,” Tyler said. “The owner came in and started dredging.”

In the wake of the 1960 Olympics, developers channeled the Upper Truckee River around the marsh and built a housing development.

The Tahoe Keys has 1,200 homes and 300 condos. Each has its own boat dock and a waterway to Lake Tahoe, thanks to a 172-acre network of artificial lagoons carved out of the former marsh.

Then someone dumped out their fish tank. It’s one popular theory for where the weeds first came from.

“Eurasian watermilfoil, one of the weeds we’re battling here, was a super common plant for aquariums,” Patterson said. “In large part because it grows super easily and spreads really rapidly.”

The milfoil became established on the keys during the 1980s and '90s. In 2003, another plant called curlyleaf pondweed showed up, likely carried in by boat from another lake.


The Tahoe Keys used to have its own system to recirculate and treat the lagoon water, but it was allowed to shut down decades ago.

Today, the water sits stagnant. The ends of the lagoons look like golf course ponds.

“It's a nursery for invasive weeds,” Tyler said.

Each summer, the stagnant canals warm and the weeds burst forth from the muck below.

The Tahoe Keys Property Owners Association operates a fleet of harvester boats to keep the canals open each summer.

“These are big floating lawn mowers, they chop the top four feet of the plants up onto a conveyor belt,” Patterson said. “The problem is: These plants spread by fragment, and chopping them off with a harvester creates millions of fragments.”

Every year, these harvesters chop out enough weeds to fill a thousand dumpsters, costing millions to the Tahoe Keys Property Owners Association. It exacts an even greater cost on Lake Tahoe’s health.

Despite the installation of a double-layer curtain of bubbles designed to knock weeds off of boats as they leave the Tahoe Keys, fragments continue to escape.

This season, volunteers will attack the latest in a string of infestations to hit iconic Emerald Bay. Divers will use plastic sheets to smother weeds, which has proven effective outside of the Tahoe Keys.

Where the weeds take root, they do multiple kinds of harm to Tahoe’s fragile ecosystem.

Invasive plants provide cover to invasive fish. Tahoe now has established populations of huge goldfish and largemouth bass, which compete with and eat native fish.

The weeds also break down into nutrients which feed a growing problem on Tahoe’s lakeshore: toxic algae blooms.


The same factors causing the Tahoe Keys to serve as an aquatic weed greenhouse also make it a pleasant place to live.

The marsh had no trees, so the properties get expansive mountain views and abundant sunshine.

“It’s always 10 degrees warmer right here,” said Pete Wolcott, standing on his boat dock in the backyard of his Tahoe Keys home. “This place is magic.”

That (and the boat dock, of course) attracted Wolcott and his wife to buy a home here.

“We didn't know about the weeds back then," he said. “If we were developing this today, it wouldn't happen.”

Wolcott ended up on the board of his HOA as it won the first-ever permit to allow herbicides in Lake Tahoe waters.

Last spring, in a one-time test run, the Tahoe Keys Property Owners Association hired contractors to apply two different chemicals: triclopyr and endothall.

“We're using 50-year-old California and federal EPA approved products,” Wolcott said. “They're really not that dangerous.”

The tested lagoons were walled off behind double barriers called turbidity curtains, meant to contain the herbicides until they reached undetectable levels.

Wolcott believes these testing restrictions were too strict, arguing they did more harm than good.

The triclopyr applied last spring took the whole boating season to break down beyond detectable levels: one part per billion.

“It took until September 22. 15 weeks,” Wolcott said.

The turbidity curtains made the water more stagnant and cloudy, he argues, making it harder for sunlight to help the chemical break down.


The idea of destroying a vast wetland to make waterfront housing would be patently offensive today.

The Tahoe Keys is a legacy of decisions made back before there was a bi-state agency tasked with protecting the lake: The Tahoe Regional Planning Agency.

The TRPA was created partially in response to the development of the Keys. Today, the agency supports the herbicide test.

“All of the analysis that we've had on this particular subject is saying that we have to act now in order to save the lake in the future,” said TRPA spokesperson Jeff Cowen. “We have to really start with feasibility.”

“We're here and we're a neighborhood,” Wolcott said. “We're not going anywhere.”

He sees the need for balance: to control the weeds, protect the property rights of Keys owners, and to do so at a price the community can afford to pay.

To him, chemicals show a lot of promise to satisfy those needs.

“It's a private Marina with 2,000 slips, it's a $15-20 million business,” Wolcott said. “It probably doesn't make sense to spend $30 million a year on the solution… but it might make sense to spend $3-5 million a year.”

Opponents view it as upside-down thinking prioritizing boating over the health of Lake Tahoe.

“It's all about the money. It's all about lakefront owners and their property rights,” said Sierra Club volunteer Tyler.

Find more stories from ABC10 Originals here

The Sierra Club and California Sportfishing Protection Alliance jointly sued California’s Lahontan Regional Water Quality Control Board for approving the permit for the herbicide test.

They argue the water board broke its own rules by failing to fully test non-chemical methods first.

“When I've talked to the public about this, everyone says, ‘What? What! They can't do that to Lake Tahoe,’” said Tyler.

ABC10 didn’t interview water board officials. Board spokesperson Edward Ortiz wouldn’t agree to an interview without knowing our questions in advance, citing the Sierra Club’s lawsuit.

Tyler, a former employee of the water board, has a list of other steps she feels need to be considered before resorting to herbicides: repair the circulating pump for the Keys, eliminate lawns to reduce nutrients, install a lock between the Keys and the rest of the lake, and even restore some of the most stagnant parts of the lagoons to wetlands.

Patterson, with the League to Save Lake Tahoe, hears those suggestions. He just doesn’t see them happening, especially if they require eliminating some of the boat docks.

“Property rights have some standing in this country,” Patterson said, explaining why the League to Save Lake Tahoe supports the test. “There's over $2 billion in real estate here.”


Patterson and other supporters of the test say they’re hoping the test can find a way to use herbicides differently in Lake Tahoe.

Aquatic herbicides are generally applied on a seasonal, ongoing basis to control weeds like those growing in the Keys.

The Tahoe Keys will examine whether weeds can be “knocked back” with one application of herbicides and then kept back using other methods in years two and three.

Laminar aeration and UV light methods are being tested in conjunction with the herbicides. Opponents call it “magical thinking.”

“One application of the herbicide? Yeah, right. Once you do it, you have to keep doing it,” Laurel Ames grumbled. “To put herbicides in this lake just upsets me so much.”

She’s been here long enough to remember the Upper Truckee Marsh, the lungs of the lake, before it was destroyed to build the Tahoe Keys.

To Ames, this idea of using chemicals comes from a rash mindset: looking for a quick buck, a quick fix. She sees it as the same mentality that allowed the Keys to be built.

“It was a marsh, but the developer called it a swamp,” recalled Ames. “We are loving the lake to death.”

The existential threat to the lake and the urgency added to it by climate change undergirds the arguments on both sides of the debate over herbicides.

It hints at a question deeper than whether to treat Tahoe’s cancer with chemo: Nature gave us this jewel of the Sierra, how long can we keep it?

ALSO FROM ABC10 ORIGINALS: As Gov. Gavin Newsom seeks to raise his national profile, local news organizations are finding it increasingly difficult to obtain responses from his administration. 

Before You Leave, Check This Out