The Tahoe Keys has long been considered Lake Tahoe’s number one environmental disaster, having been developed on the mouth of the Upper Truckee River in the 1960s. The 760-acre development, which includes 11 miles of lagoons and channels, is what environmentalists point to as the reason environmental protection was needed at Tahoe. But the main problem affecting the Keys today is a problem that threatens the entirety of Lake Tahoe — aquatic invasive weeds.
While a plethora of programs have been implemented by various agencies around the lake to prevent the infestation of invasive species, nowhere is the problem as troubling or complicated as South Lake’s Tahoe Keys. Roughly 90 percent of the 172 acres of the Keys’ waterways are infested with Eurasian watermilfoil and curlyleaf pondweed, which were introduced in the 1980s. The aggressive weeds interfere with native species, harbor non-native fish species, create mosquito habitat, and interfere with boating and other recreational activities. They also can — and have — spread to other parts of the lake. The Tahoe Keys Property Owners Association, which includes more than 1,500 homeowners, has been working for 25 years to combat the issue, but have been unsuccessful at controlling the problem.
“Nowhere else in Lake Tahoe is the problem of invasive and nuisance aquatic weeds as great as in the Tahoe Keys, where shallow, protected waterways provide ideal conditions for infestation,” states the website for the Key’s weed management plan. “We must take action to reduce and manage aquatic invasive weeds before they spread.”
The Tahoe Keys Integrated Weed Management Plan looks to address the aquatic invasive weed issue by initiating a method never before used at Lake Tahoe — the use of herbicides. The draft plan, which was released in August, includes using mechanical harvesters, bottom barrier mats, and diver-assisted suctioning, but also emphasizes the use of chemicals to combat the weeds. The plan proposes using the methods simultaneously over a five-year period, in varying degrees. The hope is that by using the proposed methods, the Keys’ weed problem will be reduced by 75 to 80 percent in five years. And the scientists involved with the plan believe the only way to achieve that goal is with herbicides.
“Herbicides knock the plant down to a manageable level. They are so much more efficient and effective than other methods,” said Lars Anderson, a former U.S. Department of Agriculture aquatic weed specialist who co-authored the plan as a consultant to the association. “Herbicides are not all the same. We researched for the type of plants that are in the Keys.”
Joel Trumbo, a senior environmental scientist with the California Department of Fish and Wildlife, who has been the agency’s integrated pests management coordinator for 25 years, advising on approximately 60 projects statewide each year, believes herbicides are needed in the Keys.
“The chance of meeting the project’s objectives without the use of herbicides would be really low,” said Trumbo, who was one of five independent experts who reviewed the plan. “It is a well thought-out plan. It is looking at all options — both chemical and non-chemical. It has the high potential to reach their goals.”
Even Dr. Charles Goldman, the former director of the Tahoe Research Group and UC Davis limnologist, whose more than 40 years of scientific findings at Lake Tahoe served as the underlying basis for nearly all major policy decisions regarding water quality in the Tahoe Basin, supports the use of herbicides in the Keys.
“For many years, I have believed that the use of herbicides is warranted in the case of the Keys, although in general I am not keen on the use of herbicides,” Goldman wrote in an Aug. 11 letter to the authors of the management plan. “I hope the necessary permits can at last be obtained to use herbicides in the Keys. I have recommended this in the past with the plastic damming of two outlets to allow the chemicals to decompose to acceptable levels.”
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NOT IN OUR WATER
However, there is some fierce opposition to the Keys’ proposal, mainly from the Tahoe Water Suppliers Association, which consists of 11 of the municipal water suppliers in the Basin. The association fears if the herbicides left the Keys and got into the lake, that they could infiltrate Tahoe’s pure water. The Tahoe Keys lagoons have two narrow, direct openings to Lake Tahoe.
“We have exceptionally good drinking water at Tahoe,” said Madonna Dunbar, executive director of the water suppliers association. “We’ve had this history here of keeping things out of the water … The driving factor behind the opposition is that the plan does not include a plan on how to protect the drinking water.”
For eight years, the association has pushed its “Drink Tahoe Tap” campaign to encourage locals and visitors to drink Lake Tahoe water, but they believe even a perception that something is entering the drinking water could be detrimental. Dunbar believes not enough testing has been done on the five herbicides that are mentioned in the plan, and would like to see more done to protect the drinking water. Duane Whitelaw, North Tahoe Public Utility District’s general manager, agrees.
“What we all share is not letting those invasive weeds go unchecked. We recognize the cost of mechanical treatment. We sympathize with that, but we are first and foremost water purveyors,” Whitelaw said. “We want to protect the interests in the people we serve … If we had the choice of to do it or not, we would choose not.”
One key factor in using herbicides over other methods is the cost. The Tahoe Keys Property Owners Association has spent $400,000 a year using four harvester boats — basically, mowers — to combat the problem. Not only have the weeds increased, but the harvesters leave weed fragments that have gotten into Lake Tahoe. Some, including Dunbar, have suggested using only bottom barriers that cover the sediment like a blanket, compressing the plants while reducing or blocking light, but the Keys have estimated the barriers would cost more than $40 million. While a formal financial analysis has not been conducted, it is believed using herbicides will be significantly cheaper than other methods.
Rick Lind, president and owner of Sierra Eco System Associates, which is managing the project, estimates the five-year implementation plan will cost $2.5 to $4 million. The Keys paid for studies from 2010 to 2013 and split the $300,000 cost with the Tahoe Regional Planning Agency, and spent more than $250,000 from 2013 to 2015 in developing and preparing the draft plan. Yet, some believe the only acceptable outcome is total eradication of the weeds — even though scientists say that is nearly impossible — and that the Keys should be spending as much as possible to make that happen so herbicides don’t have to be considered.
“If herbicides are the only solution, we should ask ourselves if the Keys are sustainable,” said Incline Village resident Bob Vidra, who has spearheaded the Facebook group Keep Tahoe Drinkable. “I understand it is going to be a lot more expensive to do it another way, but it is to their benefit … We don’t need the foot in the door on herbicides. Taking herbicides off the table means they have to be more creative.”
Anderson conducted liquid dye studies in the Keys to determine how the herbicides might move and dilute over time. He noted that the herbicides would only be applied in the late spring and early summer at a few parts per million for some herbicides and as low as a few parts per billion, and the concentrations would decline after 24 and 48 hours. Trumbo also points out that only 14 aquatic herbicides have been approved by the Environmental Protection Agency, and none have any toxilogical risk, meaning they do not pose a significant threat to fish, wildlife, or humans. But, they are heeding the criticisms, and will likely make changes to the final management plan due out in January, including the potential of using herbicides in small demonstrations and the use of barriers.
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“Our intent is to monitor that the herbicides will never get into Lake Tahoe,” Lind said. “That will not happen.”
Scientists point to warm water lakes in California where herbicides have been successful at controlling invasive weeds — Clear Lake, Big Bear Lake, and Discovery Bay, to name a few. Although the Tahoe Keys are connected to Lake Tahoe, the water bodies differ because the Keys’ lagoons have shallow waters, are warmer than Tahoe, are more turbid than Tahoe’s clear waters, and are composed of fine sediments. So, while scientists say these are prime conditions for herbicide use, there are still those that are skeptical.
“It’s not going to work. I am dead certain it will fail,” said Truckee resident Steve Urie, who has been critical of Tahoe’s aquatic invasive programs. “There is no way you are going to kill all those weeds.”
Dan Shaw, an environmental scientist with California State Parks, saw success with invasive weed control in Emerald Bay by using hand pulling, diver-assisted suctioning, and bottom barriers, but it took four years to control 6 acres, while the Keys are 172 acres. State Parks was able to remove a million stems, and saw only 12 stems return in 2014, and none in 2015. The project was the first comprehensive aquatic invasive weed removal effort in Lake Tahoe, and considered a success. While Shaw does not think a similar solution would work in the Keys, he is still skeptical about the use of chemicals.
“It would be hard to lay barriers because weeds are so tall and the water clarity is not good,” Shaw said of the Keys. “Personally, I think there are too many chemicals in our environment already … It seems hard to believe that chemicals aren’t going to be used for a long time. There are potential costs with chemicals that would be borne by everybody in Tahoe.”
Conservationist groups have remained relatively silent on the issue, including the League to Save Lake Tahoe. Many look to the non-profit for guidance on environmental issues concerning Lake Tahoe, but the creators of the “Keep Tahoe Blue” mantra have yet to take a stance on the plan. The organization says it is waiting for a formal plan to be presented to the regulatory agency before taking a position. There are still too many questions, they say, like what will happen after the five years and how long will herbicides be used for.
“We would never approve the use of herbicides in perpetuity. In regards to the Tahoe Keys, and only the Tahoe Keys, herbicides may need to be considered to manage aquatic invasive species,” said Jesse Patterson, the League to Save Lake Tahoe’s deputy director. “Until we see a plan, we really don’t know. There needs to be numerous safeguards, barriers, pilot programs, etc. Herbicides are an absolute last resort, but you can’t exclude it from the conversation.”
What Patterson, and everyone else interviewed for this story, point out is that something needs to happen in the Keys, and it needs to happen soon.
“What is happening now can’t continue to happen,” Patterson said. “We want to make sure what is done is done right.”
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NEXT STEPS
While the merits of the Keys’ plan are being debated in newspaper columns, online, and in meeting rooms, it is ultimately up to the regulatory agencies on whether or not herbicides will be used in the Tahoe Keys. The integrated weed management plan is required by the Lahontan Regional Water Quality Control Board as part of a 2014 waste discharge permit that allows the Keys to operate its weed harvesters, use bottom barriers up to 5 acres at a time to control weeds, and operate its circulation system. The weed management plan, as well as a non-point source plan that will tackle runoff and fertilizer from going into the lagoons that contribute to weed growth, are both due to Lahontan by Jan. 31, 2016.
Lauri Kemper, Lahontan’s assistant executive officer, said the agency will take 30 to 60 days to review the final plans and then the executive officer will either accept or reject them. If accepted, the Tahoe Keys Property Owners Association would have to begin the environmental review process through California, TRPA, and possibly the federal government, to enact a specific project. To use herbicides, the Lahontan Water Board must grant a separate exemption and issue a permit. If approved, parts of the plan could be initiated by 2016, while herbicide use is not likely until 2017.
The regulatory agencies are explicit in that pesticide use is currently not allowed in Lake Tahoe and that a strong case would have to be made to do so.
“Our code does say the use of herbicides should be discouraged,” said Dennis Zabaglo, TRPA’s aquatic resources program manager. “They are identifying all potential tools. It doesn’t give them approval to do anything.”
It wasn’t until 2011 when Lahontan amended its Water Quality Management Plan for the Lake Tahoe Basin to add an exemption for the possible use of herbicides. The state approved the amendment in 2012, and the EPA sent a letter to Lahontan Sept. 10 approving it, which was the final approval needed to allow the exemption. Now, the Tahoe Keys could be the first in Tahoe to use herbicides, so all eyes are on them.
“I was originally thinking I would never put pesticides or herbicides in the lake,” said Sudeep Chandra, an associate professor of limnology at the University of Nevada, Reno, who has been studying Lake Tahoe since 1997. “It’s a new paradigm at Tahoe. We have to think in a progressive and novel manner. This is a global issue, but we are struggling with it philosophically locally.”
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