Aquatic Weed Control in the Tahoe Keys

Project Information

The Lahontan Water Board has been working with Tahoe Keys Property Owners Association (TKPOA), the Tahoe Regional Planning Agency (TRPA), and other stakeholders on a TKPOA project proposal that has developed into the Tahoe Keys Lagoons Aquatic Weed Control Methods Test Project. The Project, in part, evaluates the efficacy of two aquatic herbicides, ultra-violet light treatment, and laminar air flow treatment for rapidly reducing the biomass of two aquatic invasive plants species to levels that can subsequently be controlled with non-chemical control methods.

The Project is tentatively scheduled to be conducted in the Tahoe Keys Lagoons in spring 2022, pending agency approvals/authorizations. In order for the Lahontan Water Board to authorize the Project, the Lahontan Water Board must adopt the Resolutions and Orders identified in the section, below. The Lahontan Water Board will be considering the resolutions and orders below at it's January 12 - 13, 2022 Board meeting.

What's New - Documents for January 12-13, 2022 Board Meeting

The Lahontan Water Board’s January 12-13, 2022 meeting agenda is now available, which includes Agenda Item No. 2 – Tahoe Keys Property Owners Association, Tahoe Keys Lagoons Aquatic Weed Control Methods Test. During the meeting, the Lahontan Water Board will be holding a public hearing to receive public comment and consider issuance of the Tahoe Keys Lagoons Aquatic Weed Control Methods Test National Pollutant Discharge Elimination System Permit for the Tahoe Keys Property Owners Association. The Lahontan Water Board will also consider issuance of the following items related to the Tahoe Keys Lagoons Aquatic Weed Control Methods Test during the January 12-13, 2022 meeting.

  1. Resolution for Certification of the California Environmental Quality Act Final Environmental Impact Report for the Tahoe Keys Lagoons Aquatic Weed Control Methods Test;
  2. Resolution for Granting an Exemption to the Aquatic Pesticide Discharge Prohibition in the Water Quality Control Plan for the Lahontan Region for the Tahoe Keys Lagoons Aquatic Weed Control Methods Test;
  3. Waste Discharge Requirements and National Pollutant Discharge Elimination System (NPDES) Permit for the Tahoe Keys Lagoons Aquatic Weed Control Methods Test; and
  4. Mitigation Monitoring and Reporting Program for the Tahoe Keys Lagoons Aquatic Weed Control Methods Test.

The Resolutions and Orders, above, and the Summary of Comments and Responses on the September 15, 2021 tentative Resolutions and Orders can be viewed at: https://www.waterboards.ca.gov/lahontan/board_info/agenda/2022/jan/item2.pdf.

Instructions for participating in this agenda item can be viewed at: Notice of Public Hearing - Tahoe Keys Lagoon.

The Lahontan Water Board and Tahoe Regional Planning Agency (TRPA) have also prepared a Final Environmental Impact Report/Environmental Impact Statement (FEIR/FEIS) for the Tahoe Keys Lagoons Weed Control Methods Test.  The FEIR/FEIS includes responses to comments timely submitted on the Draft Environmental Impact Report/Environmental Impact Statement in sections 2 and 3. The complete FEIR/FEIS is comprised of four separate files and can be viewed by clicking on the links, below.

  1. FEIR/FEIS for the Tahoe Keys Aquatic Weed Control Methods Tests
  2. FEIR/FEIS Appendix A – Written Comments Received during Public Review
  3. FEIR/FEIS Appendix B – Mitigation Monitoring and Reporting Program
  4. FEIR/FEIS Appendix C - Draft Environmental Impact Report/Environmental Impact Statement

Earlier Announcements and Documents

Additional Supporting Documents

  • Staff Report on Exemption to the Aquatic Pesticide Discharge Prohibition for the Control Methods Test of Herbicides and Other Techniques to Reduce Aquatic Invasive Plants in the Tahoe Keys Lagoons
  • Peer Review documents on the Tahoe Keys Property Owners Association proposed monitoring program and whether the monitoring program is sufficient to assess recovery/restoration of non-target biological communities following pesticide application

For additional test project information, documentation and environmental review information, please refer to the project specific website at:http://tahoekeysweeds.org.

Background

The Tahoe Keys Lagoons are located on the south edge of Lake Tahoe in the City of South Lake Tahoe. The lagoons were constructed in the 1960s as part of a residential development consisting of 1,529 homes and townhomes, a marina and a commercial center. The developer of the Tahoe Keys, and subsequently the Tahoe Keys Property Owners Association (TKPOA), have been working to control target aquatic weeds in the lagoons since the 1970s. In recent years, up to 90% of the wetted surface of the lagoons have been infested with aquatic weeds with the majority being non-native, aquatic invasive plant (AIP)species. The target aquatic weeds TKPOA seeks to control includes both native aquatic weeds and AIP.

The Lahontan Water Quality Control Board (Lahontan Water Board) regulates TKPOA with Waste Discharge Requirements (Order R6T-2014-0059) that requires control of non-point sources of pollution to the lagoons and control of plant fragments from aquatic weed harvesting operations. Order R6T-2014-0059 provides a mechanism for control of target aquatic weeds in the lagoons by requiring development of an Integrated Management Plan. The Lahontan Water Board also regulates the Tahoe Keys Marina under a general National Pollutant Discharge Elimination System (NPDES) Permit for Lake Tahoe Marinas (Order R6T-2016-0038), which requires AIP monitoring and AIP information sharing with the boating community.

TKPOA submitted application for an individual NPDES permit and Lahontan Basin Plan pesticide discharge prohibition exemption for the Tahoe Keys Lagoon Integrated Control Methods Test project in July 2017. The Tahoe Keys West Lagoon Integrated Control Methods Test project was designed to test the efficacy of three herbicides followed by several non-herbicide control methods to explore an integrated methods approach to bring target aquatic weeds under control within the test area of the West Lagoon of the Tahoe Keys in Lake Tahoe. An initial study under the California Environmental Quality Act (CEQA) was performed in 2017 and a determination to conduct a full CEQA analysis was made. TKPOA withdrew the initial NPDES application submitted in July 2017 pending securing funding for a full CEQA analysis.

TKPOA submitted a second individual NPDES application and Lahontan Basin Plan pesticide discharge prohibition exemption application for the Tahoe Keys Lagoons Restoration Project in July 2018. The Tahoe Keys Lagoons Restoration Project was designed as a long-term, full lagoons treatment project to control target aquatic weeds through initial use of aquatic pesticides for target aquatic weed knock down followed by non-chemical controls to prevent re-infestation of treated areas within the Tahoe Keys Lagoons and infestation of greater Lake Tahoe.

TKPOA subsequently revised the scope of the Tahoe Keys Lagoons Restoration Project to be a limited area test project more consistent with the project the initial study examined and, renamed the project to the Tahoe Keys Lagoons Aquatic Weed Control Methods Test project. The overall purpose TKPOA has for developing optimal target aquatic weed control methods to be utilized in the Tahoe Keys Lagoons is to reduce and control the abundant growth of target aquatic weeds that:

  1. Compromise the water quality and degrade the beneficial uses of the Tahoe Keys Lagoons,
  2. Threaten the future ecosystem and water quality of Lake Tahoe.

The 2015 Lake Tahoe Aquatic Invasive Species Implementation Plan listed the Tahoe Keys as one of the highest priority areas for control of AIP in Lake Tahoe. The Tahoe Keys Lagoons are estimated to be the source of more than 25% of all commercial, governmental, and private boating on Lake Tahoe. As a result, the Tahoe Keys Lagoons AIP infestation is likely a significant source of AIP spread to other Lake Tahoe nearshore areas.

A selection process to choose a facilitation services company for the test project was completed in July 2018. The facilitation services selection team was composed of Lahontan Water Board staff, a TKPOA representative, TRPA staff, a Tahoe Water Suppliers Association representative, and a League to Save Lake Tahoe representative. Following the interviews of all companies that responded to the facilitation services request for proposal, the selection team unanimously selected Zephyr Collaboration to provide facilitation services for the project in July 2018.

In October 2018, Lahontan Water Board staff and representatives from TKPOA, TRPA, the League to Save Lake Tahoe, and Tahoe Water Suppliers Association, led by Zephyr Collaboration, worked on establishing a collaborative process for environmental review and permitting of the test project. The collaborative process design addresses a wide range of topics from establishing a project review and permitting schedule and an EIS/EIR environmental analysis schedule, to reviewing the list of stakeholders and covering questions from those present on the collaborative process design.

Order R6T-2014-0059

TKPOA is currently implementing Waste Discharge Requirements (Order R6T-2014-0059) adopted by the Lahontan Water Board on July 14, 2014.  The Findings in Order R6T-2014-0059 state, in part, the following:

“Excessive growth of aquatic plants within the [Tahoe Keys] Facility impairs beneficial uses of water, such as Cold Freshwater Habitat, Navigation, Water Contact Recreation, Non-contact Water Recreation and possibly Rare, Threatened, or Endangered Species.  The excessive aquatic plant growth has caused several adverse effects to cold water ecosystems: impaired navigation of vessels, potential health and safety risk associated with entanglement of swimmers in aquatic vegetation and lack of visibility of submerged swimmers, impairment of fishing and aesthetic quality, and increased predation of native fish species by invasive fish species.”

Consistent with Order R6T-2014-0059, TKPOA has developed, implemented and continues to refine a Non-Point Source Water Quality Management Plan to address potential land-based sources of nutrients contributing to target aquatic weed infestations and harmful algal bloom outbreaks. In addition, TKPOA has developed, implemented and continues to refine an Integrated Management Plan to address the growth of target aquatic weeds. Per conditions of Order R6T-2014-0059, and prior permits issued to TKPOA, only non-chemical methods have been permitted and implemented for target aquatic weed control. TKPOA has been implementing seasonal harvesting and other non-chemical controls since the mid-1980s with limited success in target aquatic weed control. Recent aquatic plant surveys (2014, 2015, 2016, and 2017) have shown that up to ~160 of the 172 acres in the Tahoe Keys Lagoons are infested with target aquatic weeds during the peak growth season.

The following are links to documents related to Order R6T-2014-0059 and its implementation by TKPOA:

Regulatory Considerations

Pursuant to Section 13260 of the California Water Code, a Report of Waste Discharge (ROWD) is required to be submitted for all new discharges.  Section 13260 states that any person discharging or proposing to discharge waste that could affect the quality of the waters of the state, other than into a community sewer system, shall file an ROWD containing information that may be required by the specific Water Boards.

In accordance with Title 40§122.21(a) of the Code of Federal Regulations, any person who discharges or proposes to discharge pollutants to waters of the U.S. must submit a complete application for NPDES permit coverage.

The Applicant must comply with the pesticide prohibition exemption criteria in Chapter 4.1 of the Lahontan Basin Plan and submit all required documents and plans specified in Chapter 4.1. The project requires an appropriate CEQA document, as granting of an exemption for the use of algaecides or aquatic herbicides is a discretionary action of the Water Board. Additionally, the Applicant must comply with requirements of the Antidegradation Policy given in Chapter 5.1 of the Lahontan Basin Plan. 

Outstanding National Resource Waters

As noted in the Lahontan Basin Plan, Lake Tahoe has been designated a Tier III, Outstanding National Resource Water (ONRW). The Water Board has consistently considered the Tahoe Keys Lagoons to be part of Lake Tahoe. Following are some facts and arguments in support of this finding.

  • Waters of the Keys Lagoon are hydrologically connected to waters of Lake Tahoe, and exchange freely. Research by the University of California Davis Tahoe Environmental Research Center on Exchange flows between Lake Tahoe and Tahoe Keys Lagoons correctly refers to the Tahoe Keys Lagoons as “semi-enclosed lacustrine embayments,” not as separate waterbodies. 1
  • Mean hydraulic residence time within the area of active water exchange was estimated to be only 2-6 days.  Water Board staff have determined the Tahoe Keys Lagoons are functionally part of Lake Tahoe and are subject to Tier III requirements of State and federal antidegradation policies for ONRWs. 
  • Additionally, the ONRW designation for Tahoe Keys is consistent with TRPA policy that allows motorized boats only in Lake Tahoe and not its tributaries.

The practical importance of this designation is that no permanent or long-term degradation of water quality is allowed in Tier III waters. Short-term degradation is generally defined as “weeks to months, not years” of water quality degradation.


1 La Plante, Alexa C., 2008. Exchange Flows Between the Tahoe Keys Embayments and Lake Tahoe, California-Nevada. Master of Science Thesis, Department of Civil and Environmental Engineering, UC Davis.

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Russell Norman
Email: Russell.Norman@waterboards.ca.gov
Phone: (530) 542-5435