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Tahoe Keys Water Quality Board Update

From Board Chair, Andy Kopania

Printed in Keys Breeze, October Edition

Update on Plans to Combat Weeds in the TKPOA Lagoons

As aquatic invasive plants have increasingly become an urgent, Lake Tahoe-wide threat to water quality, the environment and the economy, the Tahoe Keys Property Owners Association has been hard at work on implementing strategies to control the plants both today and well into the future. As the Chair of the Water Quality Committee I wanted to give an update to the members as to where we are at in the process.

What we are doing today:

Harvesting + Fragment Collection:

In 2017, TKPOA staff removed 9,996 cubic yards (that's more than 900 dump trucks) of aquatic invasive plants from its lagoons, an undertaking that totaled more than 6,000 man-hours of work.

We have also installed a bubble curtain across the west channel entrance. The bubble curtain, together with the boat back-up station, is designed to significantly reduce the number of weed fragments that leave the Tahoe Keys lagoons and enter Lake Tahoe.

Bottom Barriers:

Bottom barriers were once again installed this spring in the lagoons at locations requested by homeowners who volunteered for this program.

Non-Point Source (NPS) Plan:

As part of the Waste Discharge Requirements (WDRs) issued to TKPOA by the Lahontan Regional Water Quality Control Board (Lahontan), we have prohibited the use of phosphorus-containing fertilizers, encourage the reduction of lawn irrigation, and have conducted “lunch and learn” seminars for contractors to educate them on ways to reduce the release of nutrients and other contaminants (e.g. from construction work or from draining spas) into our lagoons.

Laminar Flow Aeration:

We are also in the process of applying for permits from various regulatory agencies to test a technology called Laminar Flow Aeration (LFA). 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 changes 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, which should reduce the rate and amount of weed growth in the area of the LFA test. The test will be conducted in the lagoons adjacent to Christie Drive, north of Venice Drive. TKPOA has received financial support for this project from The League to Save Lake Tahoe.

Before we can start this test, we need to receive permits and regulatory approvals from the Tahoe Regional Planning Agency (TRPA), the California Department of Fish and Wildlife, the U.S. Army Corps of Engineers, and Lahontan. The number of regulatory approvals needed for this simple test illustrates some of the challenges that TKPOA faces in finding and implementing solutions to the aquatic invasive weed infestation. A similar test was recently approved and installed at Ski Run Marina so we are hopeful that we will also receive approval soon.

Plans for the Future:

While we are committed to non-chemical methods for 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 those methods can keep up with the growth across the 170 or so acres that make up our lagoons.

To get the plant growth to a level where non-chemical methods can be effective and the need for harvesting will be substantially reduced, we are 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. In short, our expert panel and consultants have indicated that short-term herbicide use will provide the most promising option at this point to truly curtail and treat the aquatic invasive plants in the Tahoe Keys and minimize the potential for spread throughout the lake and beyond the control of resource managers.

In order to move forward with controlled herbicide use, a joint Environmental Impact Statement (EIS)/Environmental Impact Report (EIR) must be prepared by TRPA and Lahontan. In step with this process, we have applied for a permit from both agencies to allow use of safe, EPA-approved herbicides to combat the weeds. The herbicides that our experts have recommended target the specific invasive weed species but do not affect native aquatic plants, fish, wildlife, or recreation. The proposed rate of application would be well below the EPA-approved concentrations and are expected to quickly degrade. 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 non-herbicide methods for long-term weed management.

Despite the documented safety of using the proposed herbicides to combat the invasive weeds, we understand that herbicide use can be a divisive and contentious topic. To ensure transparency and constructive dialogue, key stakeholders have agreed to engage in a collaborative process over the next 12 months. Several stakeholders, including TKPOA, worked with TRPA to hire Zephyr Collaboration to conduct the facilitation and mediation work during the EIS/EIR process to ensure there is input from all stakeholders. Our hope is that by engaging in a robust collaborative process to design the most effective path forward, we will get to a solution faster.

We will keep the TKPOA membership updated as we move forward through the process.

If you would like to know more about the EIR/EIS process, herbicides or the invasive weed management plan in the Tahoe Keys, please visit or attend one of our monthly Water Quality committee meetings.

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