Reducing the volume of weeds helps to ensure that other methods are more effective and fragments do not enter Lake Tahoe. TKPOA's best management practices that are used to reduce weeds include:

Harvesting and fragment collection: In 2017, TKPOA staff removed 9,996 cubic yards (that's more than 900 dump trucks) of aquatic invasive plants and fragments from its lagoons.
Boat back up station: The boat back-up station is designed to ensure that invasive weeds don't make their way to Lake Tahoe on a boat propeller to propagate and spread.
Bubble curtain: In 2018, a bubble curtain was installed across the west channel entrance. Using bubbles to create a barrier, it reduces the potential for movement of fragments into Lake Tahoe.
Sea Bins

TKPOA's current methods:

Bottom Barriers:

Synthetic mats are installed to block out sunlight and smother aquatic invasive weeds on the floor of the lagoons. These barriers are installed at locations requested by homeowners who volunteer for this program. The Association is allowed a total of five acres of bottom barrier coverage.

Non-Point Source (NPS) Plan/ Lake Friendly Landscaping

As part of the Waste Discharge Requirements (WDRs) issued to TKPOA by the Lahontan Regional Water Quality Control Board, TKPOA created a homeowner education program, Lake Friendly Landscaping, to ensure residents were following the required policies.

The Lake Friendly Landscaping program summary

Prohibits the use of phosphorus-containing fertilizers.
Encourages the reduction of lawn irrigation.
Conducts “lunch and learn” seminars for landscaping companies to educate them on ways to reduce the release of nutrients and other contaminants into the lagoons.

TKPOA's proposed methods:

The following methods are currently being tested or evaluated by TKPOA as solutions to our invasive weeds problem:

Floating Islands: This technology uses native wetland plants on a floating matrix. The roots extend into the water providing a very large surface area through which nutrients are absorbed and removed from the water. The islands may also be deployed with fine-bubble aerators to create water circulation to push more water through the root system. In the summer of 2020 the TKPOA installed 15 Floating Islands in Lake Tallac to address their efficacy in improving water quality.

Circulation System Reactivation

EcoSoar: EcoSoar utilizes an all-natural scientific process to both create and inject superoxide anion radicals (SOAR) into the water column and sediment to clean and restore the water body to a natural, healthy state. Status: The EcoSOAR vendor has agreed to provide a 3-month test of their unit along with installation and technical support, at no cost. TKPOA will need to pay for permitting, electricity and monitoring.

Laminar Flow Aeration: Laminar Flow Aeration (LFA) involves bubbling air through several small diffusers on the bottom of the lagoons. The air bubbles cause the water to circulate, increasing the amount of oxygen at the bottom of the lagoons, which in turn facilitates changing the form of some of the nutrients in the sediment and “muck”. This change is intended to make the nutrients less available for the weeds and algae, which should reduce the rate and amount of weed growth in the area of the LFA test. Status: TKPOA is applying for permits from various regulatory agencies to test a technology called Laminar Flow Aeration (LFA). TKPOA has received financial support for this project from The League to Save Lake Tahoe. The TKPOA currently has 2 LFA sites, one adjacent to Christie Dr. North of Venice Dr and another in the West Channel entrance.

UV Light Treatment: UVC light damages the DNA and cellular structure of the plants, causing them to die. The light energy goes into the plant and essentially sunburns and scars the outer tissue. It also causes a cell fusion and they can no longer reproduce. Status: This method is currently being tested at the Lakeside Marina. Depending on the outcome of the UV light test, this method could also be one of TKPOA’s many tools in their integrative approach to managing the invasive plants.

Well-monitored, localized use of EPA and Cal/EPA approved selective herbicides in specific areas of the lagoon: While TKPOA is committed to the integrative and long-term control of invasive plants, the reality is that the current approved methods are not enough to reduce the infestation to the point where the methods can keep up with the growth across the 170 or so acres that make up the lagoons. Along with other proposed methods outlined earlier, TKPOA is proposing a short-term, highly managed spot use of herbicide in specific areas of the lagoons, away from the main channel and far from the entrance to Lake Tahoe. The aim is to efficiently reduce invasive plant growth to a level where all methods can be integrated effectively and thereby reduce the need for harvesting.

Further information on the proposed EPA approved herbicides

The herbicides would only be used in a series of controlled and careful applications to reduce the volume of plants to a manageable level, and then replaced with other methods for long-term weed management.
Target the specific aquatic invasive plant species but do not affect native aquatic plants, fish, wildlife, or recreation.
Proposed rate of application would be well below the EPA-approved maximum allowable concentrations and at that application rate is nontoxic to fish, wildlife and humans.
Projected to quickly degrade after application and not exit the Tahoe Keys lagoons during those limited application periods.
Endorsed by a number of independent national and regional experts including the California Department of Food and Agriculture, UC Davis, US Army Corps of Engineers, University of Nevada, Reno and the California Department of Fish and Wildlife.

The proposed aquatic herbicide treatment, as outlined in the Tahoe Keys Lagoon Restoration Project proposal, is as follows:

Year 1: While continuing to apply all other controls, apply herbicide to 13.7 acres in Tahoe Keys Lagoons and 4.5 acres of Tallac Lagoon to test effectiveness of treatment.
Year 2: Apply only other integrative methods (non-herbicide) and evaluate the efficacy of herbicide treatment test.
Year 3: While continuing to apply all other controls and based on the learnings of the tests in Year 1 and Year 2, apply herbicide up to 72 acres in Tahoe Keys Lagoons and Tallac Lagoon. (8-15 acres/day for 5-10 day period)
Year 4: While continuing to apply all other controls, apply herbicide up to 64 acres in Tahoe Keys Lagoons and Tallac Lagoon. (8-15 acres/day for 5-10 day period)
Years 5-12: Apply all other controls. If needed, apply herbicide to maximum of 35 acres in Tahoe Keys Lagoons and Tallac Lagoon, in any one year.

The project performance criteria for the herbicide use is as follows:

Achieve and maintain at least 75% reduction of invasive plant biomass from the baseline.
Achieve and maintain a minimum of three feet of vessel hull clearance within navigation channels.
Increase native plants in treatment areas from the baseline.

Eyes on the Keys