Q: What are the Tahoe Keys?

    A: For the purposes of the Integrated Management Plan and Nonpoint Source Water Quality Management Plan, the Tahoe Keys is a development complex, which includes seven primary private and public landowner groups. This includes a nonprofit residential association (Tahoe Keys Property Owners Association) comprised of 1,529 homes and townhomes, a commercial marina, a medium sized commercial business center, a nonprofit dock and boat moorage association, the privately owned Lake Tallac and the nonprofit California Tahoe Conservancy.


    Q: What is the Tahoe Keys Property Owners Association?


    A: The Tahoe Keys Property Owners Association (TKPOA) is a private community connected by 11 miles (172 acres) of interconnected waterways. The Tahoe Keys is located at the southern tip

    of Lake Tahoe in South Lake Tahoe, California. Most of the 1,500+ members who own homes, townhouses or vacant lots have a private boat dock and are located on its lagoons.


    Q: What are the aquatic invasive plants in Tahoe Keys, and why are they a problem?


    A: Aquatic invasive species including Eurasian watermilfoil and curly leaf pondweed, along with the native nuisance plant coontail, make up the bulk of the problem in the Tahoe Keys. They interfere with native species, harbor non-native fish species, create mosquito habitat and interfere with boating and other recreation.


    Q: How did these plants get into the Tahoe Keys? Where did they come from?


    A: Both invasive species are native to Europe and Asia, with Eurasian watermilfoil likely being introduced in the 1980s - curly leaf pondweed some time after that (first recorded in the Tahoe Keys in 2003). No one knows how they were introduced, but it is likely from home aquarium dumping or transported via boat.


    Q: What are you doing now to fight the weeds?


    A: Currently, the Tahoe Keys Property Owners Association is harvesting, using five harvester boats to cut as much weed mass as possible, spending as much as $400,000 a year. Despite these efforts, the volume of weeds is only increasing (The volume of weeds grew from 100 cubic yards in 1984 to 18,600 cubic yards in 2014). TKPOA has also entered the pilot phase of bottom barrier use, which is being expanded on with the proposed Integrated Management Plan (IMP).


    In 2016, the Association has begun to improve on harvesting techniques and technology, including fragment collection to reduce the weeds' spread, plan a more robust bottom barrier mat program, and field a number of studies or test runs, as detailed in the plan section above.


    In 2017, the Association has further improved harvesting, purchased an Omnicat skimmer boat to improve fragment collection, and implemented a boat backup station that is reducing the transport of fragments.


    Q: How are environmental and regulatory organizations involved in this process?


    A: We have been engaging local and regional agencies and stakeholder groups throughout the process for more than five years now, keeping them apprised of the planning process, jointly performing studies, and investigating proposed methods of weed management. Ultimately, the Plan will need to be approved by the Lahontan Regional Water Quality Control Board.


    Q: How do we know using herbicides will be safe for the lake, other species and drinking water?


    A: Extensive dye studies have been conducted in the Keys to determine water movement in different seasons, informing potential strategies for herbicide application. Because the herbicides break down rapidly in open waters (a matter of days), they become inert quickly and will not spread beyond the intended target locations in the Tahoe Keys. The herbicides under consideration are designed to become inert quickly and are specific to the problem plants found in the Tahoe Keys. These same herbicides have been proven to be effective elsewhere in California, in alpine lakes, and in other similar settings throughout the country.


    Further study of herbicides are being considered for 2016, with a possible demonstration test application in 2018, if approved by permitting agencies.


    Q: Why is the Tahoe Keys Property Owners Association preparing the Plan?


    A: TKPOA has been investigating long-term solutions to the weed problem since 2007. The severity and cost of the weed problems in the Tahoe Keys, combined with TKPOA’s support of regional efforts to maintain and improve the quality of the Tahoe Keys and Lake Tahoe for its members, along with the predominately private land ownership of the Tahoe Keys, prompted TKPOA in 2012 to begin preparing a Plan in cooperation with numerous public agencies, interest groups and other landowners. In 2014, the Lahontan Regional Water Quality Control Board made the Plan a formal requirement.


    Q: Can the Tahoe Keys just use bottom barriers to eliminate the problem?


    A: Plants can easily grow on the barriers unless they are cleaned or removed and replaced every year. Experiments testing the barriers in the Tahoe Keys also showed that watermilfoil begins to inhabit the sediment that deposits over time on the bottom barriers. And curlyleaf pondweed does not require roots to grow, reproduce, or expand, thereby making bottom barriers of limited effectiveness for the highest threat invasive plant. A significant portion of the lagoons cannot be treated with barriers effectively due to the presence of hundreds of structures like docks, pilings and platforms (divers would have to work the barrier mats around these obstructions in turbid water). From a practical standpoint, widespread use of bottom barriers is not effective due to boat traffic that dislodges bottom barriers, which then become a safety hazard. For these and other reasons it has been estimated that complete coverage of the Tahoe Keys with bottom barriers, including placement, maintenance and removal, would cost more than $40 million.


    Q: Can the Tahoe Keys be drained to eliminate the problem?


    A: Realistically, no, due to a combination of variable waterway depths, structural threats to bulkheads, local groundwater conditions, seed bank of invasive species present in the sediments evolved to tolerate drought, the amount of energy/pumping required, and the need to filter, treat and dispose of the aquatic animals/plants/waters drained from the waterways. From a groundwater perspective, because the Tahoe Keys lands are built on highly porous materials (sand), draining the waterways is likely not possible. With the environmental impacts, prohibitive costs, problematic groundwater conditions, extensive seed bank in the sediments, and economic/recreation impacts of this method, draining is considered infeasible. Again, for curlyleaf pondweed, turions have evolved to survive extended drought periods and would come back even after drying the lagoons.


    Q: Have herbicides been used in similar lakes or bodies of water?


    A: First, it’s important to be clear that the herbicides will not be used in Lake Tahoe, they will be limited to the Tahoe Keys Lagoons. These lagoons are similar in bathymetry (underwater equivalent to topography), ecosystem function, habitat, depth, temperature and water quality to hundreds of similar shallow, warm water lakes in California. In addition, the lagoons are connected to Lake Tahoe by two channels. The herbicides can be controlled and prevented from entering Lake Tahoe.


    Herbicides have been and are currently being used in many California water bodies, including Clear Lake, Big Bear Lake, Discovery Bay, and the Sacramento-San Joaquin Delta in California, as well as lakes in Washington, Oregon, Minnesota and Florida.


    Q: What risks do these herbicides pose to the natural environment and humans?


    A: Aquatic herbicides control aquatic vegetation without posing significant threat to fish, and have been approved for aquatic systems after extensive studies for efficacy and toxicology. These herbicides are regulated by the US Environmental Protection Agency and California EPA. They were required to be tested for potential harm to human health and the environment, and deemed as non-toxic to fish and humans when applied at proper concentrations by licensed applicators. because their modes of action affect plant processes like photosynthesis. The herbicides are not classified as carcinogens. They have been studied in the lab and in the field to find out what happens to their active ingredients in water, plants, fish and soil.


    Each of the herbicides under consideration for the Tahoe Keys has been rated for fishing, recreation, livestock and pet consumption as: No restriction. Because herbicides are broken down by microbial action, photolysis and hydrolysis, they have half-lives from a few days to a few weeks.


    Q: How will you prevent herbicides from getting into Lake Tahoe and potentially into drinking water?


    A: A Rhodamine WT dye study analyzed the movement of water in the Tahoe Keys in different seasons, modeling the potential spread of herbicides from application sites over time. Applications will be made at times and locations that preclude movement from the Tahoe Keys lagoons to Lake Tahoe. Impermeable barriers will be used at some sites to prevent dissipation. Pre- and post-application water sampling and analysis will occur with each application. Because herbicides are broken down by microbial action, photolysis, hydrolysis, they have half-lives from a few days to a few weeks. So, as shown by the dye studies, by the time the herbicides could move out of a selected lagoon, they will have broken down to an inert state.


    Q: Would the use of herbicides in the plan, if approved, open the door to herbicide use elsewhere in Lake Tahoe?


    A: No, a permit for herbicide use in the Tahoe Keys could not be used for herbicide use anywhere else in Lake Tahoe. The TKPOA is not promoting use of herbicides in Lake Tahoe.


    Tahoe Keys is a unique situation within the Lake Tahoe region: the lagoons are shallow and narrow, the weed problem is severe (and thus the control measures are needed) and it is physically isolated from the lake except for two small connecting channels (which make herbicides much easier to control than elsewhere). Any future weed management plan proposing the use of herbicides would have to undergo rigorous environmental review and permitting.

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