Tahoe Water Suppliers Association is Greatly Concerned by Potential Herbicide Use at Tahoe Keys to Control Aquatic Weeds
The following article was submitted by the TWSA March 12, 2018.
For More Information contact: Madonna Dunbar, TWSA, mod@ivgid.org 775-832-1212
The Tahoe Water Suppliers Association wants the public to know that it is greatly concerned about the impact of potential herbicidal usage at Tahoe Keys to control aquatic invasive weeds on the quality of Lake Tahoe’s drinking water and the infrastructure used to procure and deliver that water.
The Tahoe Water Suppliers Association (TWSA) is an organization whose members are the 11 principal Tahoe Basin municipal drinking water providers with intakes that draw water from Lake Tahoe, plus one groundwater utility. These providers serve the majority of water consumers in the Lake Tahoe Basin.
TWSA’s mission is “to develop, implement and maintain an effective watershed control program in order to satisfy recommendations in watershed sanitary surveys, advocate for the protection of Lake Tahoe as a viable source of drinking water, and to satisfy additional state and federal requirements.”
Consistent with this mission, TWSA has been actively engaged in the public process with state and federal regulatory agencies working to address the proliferation of aquatic invasive weeds at Lake Tahoe and the impact potential control strategies may have on the quality of Lake Tahoe’s drinking water and the infrastructure used to procure and deliver that water.
TWSA believes there are multiple non-chemical methods that should be explored on a greater scale, with better project design which are outlined here.
The Problem
Nuisance non-native and native aquatic plants have been observed in marinas and other recreational areas in Lake Tahoe and the Lake Tahoe Basin. Dense coverage of aquatic plants can degrade the water quality and aquatic habitat by making the ecosystem less favorable for native organisms that are adapted to the pristine water of Lake Tahoe. The excessive growth of these nuisance plants interferes with boating and recreational access to Lake Tahoe when they become entangled in propellers and keels. Plants can also ensnare swimmers and divers and compromise their safety. Various agencies, experts and observers agree that the greatest single concentration of aquatic plant and weed problems are in the Tahoe Keys development on the Lake’s southwest shore. The Keys is a residential subdivision that includes inland waterways and coves and is home to the Tahoe Keys Marina, Tahoe’s largest marina facility. The Keys totals 172 acres of water surface accessible to and from Lake Tahoe through two boating channels.
Tahoe Keys Property Owners Association (TKPOA) Integrated Weed Management Plan
By order of the California Lahontan Regional Water Quality Control Board, the TKPOA has funded preparation of an Integrated Weed Management Plan for the Tahoe Keys Lagoons. The stated purpose of the Plan is to “present a strategy to control and manage invasive and nuisance aquatic plants.” One of the control strategies identified in the Plan is the use of aquatic herbicides.
Aquatic Plants and Weeds of Greatest Concern
The multi-agency Lake Tahoe Aquatic Invasive Species (AIS) Coordination Committee continues to inventory and track the presence and growth of aquatic nuisance and invasive plants and weeds and guide their management and control at Lake Tahoe. Specific to the Tahoe Keys, the Tahoe Keys 2014 Aquatic Plant Survey is another document prepared by the TKPOA. Three species are considered to be the most significant threat.
- Curlyleaf Pondweed - This plant is extremely adaptable and its spread beyond marinas to sections of Tahoe’s nearshore is very visible. It is considered the main threat to Lake Tahoe’s aquatic habitat. Pondweed “turions” spread as seed packets and can survive harsh conditions.
- Eurasian Water Milfoil - Colonization in Lake Tahoe itself is more limited, so this plant is more a threat to marinas and other areas where water is more shallow, sheltered and warmer. The plant spreads via fragments.
- Coontail - This species is native to Lake Tahoe. It thrives in deeper water. It becomes a safety and nuisance factor for boating, swimming, and diving due to its floating and matting nature.
TWSA Perspectives and Concerns
Our members provide water service to all manner of users, rate payers, tax payers and visitors to Lake Tahoe. We are dedicated to the protection of Lake Tahoe’s pristine water quality and healthy ecosystem. We also appreciate recreational boating and water-based sports in the world-renown destination resort region. We recognize that the growth of invasive plants and weeds is a serious problem. Prompted by the exponential growth of invasive weeds, federal and state water quality regulators have lifted a previous prohibition against the use of aquatic herbicides in the waters of Lake Tahoe as one of the control strategies for invasive weeds. The chemicals proposed for use have been tested and used primarily in lower quality waters. TWSA believes Lake Tahoe’s special status as a Tier 3 Outstanding National Resource Water (ONRW) warrants a priority focus on non-chemical methods before the use of chemical herbicides is considered. TWSA also urges the IWMP to include a more detailed analysis of the potential impacts of herbicides on drinking water supply.
TWSA members share concerns about the potential impact of herbicides on our water intake systems and quality of the water we provide to our customers. Tahoe’s municipal water treatments systems are not specifically designed to remove chemical contaminants. Six TWSA members hold “filtration exemption” status from the U.S. Environmental Protection Agency (US EPA). This is a rare status, usually granted only to a “non-contact” watershed. It has been granted based on the fact that Tahoe “tap water” is some of the cleanest and purest drinking water in the world. The treatment process of ultra- violet and ozone disinfection used by members with “filtration exemption” status is designed for the deactivation of potential biological contaminants, not chemicals. Their effectiveness and efficiency at removing chemical compounds is unknown. In addition to TWSA members, a number of water systems owned by private companies and individuals also draw water from Lake Tahoe. If chemical contaminants begin to be detected near Lake Tahoe water intakes, our ratepayers and the owners of small private water systems may face costly infrastructure upgrades.
The purpose of this TWSA background and fact sheet is to help educate the public about the challenges of aquatic invasive weed management and control and our concern about the potential impact of aquatic herbicides on Lake Tahoe’s pristine drinking water and our drinking water delivery systems. In 2016, the TKPOA Integrated Weed Management Plan (IWMP) was submitted to the Lahontan Water Board. In January 2017, the Application for Exemption to the Basin Plan Prohibition on the Use of Pesticides for the Tahoe Keys West Lagoon Integrated Control Methods Test, was submitted to Lahontan staff. The proposal is to test 3 different herbicides (Triclophyr, Endothall, Penoxsulam) in 9 locations within the Keys, a total of 13.7 acres, about 8% of the Keys water area, during one season, with follow-up in years 2/3 by diver handpulling, bottom barriers and harvesting. Mitigations are proposed to physically separate the treatment area from Lake Tahoe. Water quality sampling mitigation is also proposed.
The proposal is currently under TRPA and Lahontan staff review, with anticipated public comment in
2018, after CEQA environmental documents are prepared.
Learn More, Get Involved: To review the proposals, visit http://www.keysweedsmanagement.org./#methods
Comments are requested for the review process. Final documents will post at: http://www.waterboards.ca.gov/lahontan/public_notices/bp_prohibition_exemptions.shtml
SUBMIT COMMENTS AT ANY TIME TO:
Lahontan Regional Water Quality Control Board (LRWQCB)
- Bruce Warden bruce.warden@waterboards.ca.gov
- Russell Norman russell.norman@waterboards.ca.gov
Tahoe Regional Planning Agency (TRPA)
- Dennis Zabaglo dzabaglo@trpa.org
- Paul Nielsen pnielsen@trpa.org
