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Milfoil Control Efforts

Eurasian Watermilfoil (EWM) was first identified near the public fishing access in Lake Iroquois around 1990. Various efforts were made to control the infestation including hand pulling, use of weevils, and establishment of the LIA Greeter Program.   However, by 2014, it was clear that the EWM infestation was spreading out of control, seriously impeding boating, swimming, fishing, and causing an alarming decline in native aquatic species. In order to understand what was happening and what our options were, the LIA Board began to study and research options for reducing and controlling EWM.

The result of this work has been the development of an EWM Long-Range Management Plan that involves a multi-faceted approach. The plan includes a careful and judicious use of the herbicide, ProcellaCOR.  This approach is balanced by historic and continued use of other methods such as diver-assisted suction harvesting (DASH), use of benthic (bottom) barriers in certain limited areas, hand pulling, and ongoing work to continue to reduce nutrient levels in the lake. These efforts serve as an integrated approach that when combined with LIA’s Greeter and Boat Wash Program, aim to prevent further introduction of invasives into the lake and to control and reduce the EWM invasive that is already there. 

The plan proposes to treat up to 40% of the littoral zone (‘near shore’ areas where these aquatic plants grow) with ProcellaCOR. This is slightly less than 16% of the entire lake. The concentration rate to be used will be no more than 3 PDUs (Prescription Dose Units) which is equal to a rate of 1.93 ppb (parts per billion). At this rate on this proportion of the lake it is expected that the concentration level in the entire lake would be no more than 0.47 ppb on the day of application.  For reference, imagine 1-2 drops in an Olympic-sized swimming pool. 

ProcellaCOR was granted Reduced Risk Status by the US EPA in early 2016 because of its promising environmental and toxicological profiles. This product has been widely analyzed by universities, federal and state governments, and health departments. Findings show that professional application of ProcellaCOR in accordance with the label will not cause adverse effects on human health or the environment.  Studies also indicate that chronic exposure did not result in carcinogenicity, mutagenicity, nor genotoxicity effects. In addition, ProcellaCOR breaks down quickly in the environment (hours to days).  It was used on four lakes in Vermont in 2019 and on six lakes in 2020.  The detailed permit application, including supporting documentation and data, the issued permit, the treatement plan, notifications, and other materials can be found below.  

Watershed partners unite to develop Watershed Action Plan for Lake Iroquois

This picture is from a Lake Iroquois stream remediation and erosion control project from 2017-2018. This watershed action plan will identify similar sources of erosion which contribute to poor water quality in the watershed and work to stabilize soils and improve habitat.

The Winooski Natural Resources Conservation District (WNRCD) is pleased to announce the awarding of Lake Champlain Basin Program funds to develop a Watershed Action Plan for Lake Iroquois and the Patrick Brook watershed. WNRCD has partnered with Lake Iroquois Association (LIA) and Lewis Creek Association (LCA) to identify and address priority opportunities that remediate stormwater runoff and phosphorus pollution to improve water quality, wildlife habitat, and climate change resilience. 

“This project is a really exciting opportunity to work collaboratively with watershed partners and the public to identify and address a number of the water quality concerns in the Lake Iroquois and Patrick Brook Watershed.” says Remy Crettol, WNRCD District Manager. He continues, “A big priority of ours is to get the public involved. We will have outreach events including public forums and walking tours of LakeWise and Ahead of the Storm properties. Hopefully, this will inspire residents to consider stormwater assessments on their own properties.”

As a popular recreational destination in burgeoning Chittenden County, Lake Iroquois has seen an increase in visitors. A rise in seasonal camp conversions to year-round use, and neighborhood expansion, place high stress on private road systems and increase stormwater, sediment, and phosphorus runoff to the lakes, ponds, and streams (Patrick Brook, which drains into the LaPlatte River and on to Lake Champlain). Currently, the watershed lacks any recent comprehensive analysis of water quality and habitat stressors.

In completing this project, watershed residents will have increased knowledge of their impacts on water and habitat quality. Communities will have improved planning tools and a holistic road map with clearly prioritized projects as a guidepost for design and implementation. Regional partners can then target limited funds toward high priority projects that benefit the watershed and its residents.