At the recommendation of the Thornapple River SAD Ad-Hoc Committee, the Township solicited bids for a multi-year aquatic weed management program, which began. in 2022. Through that process, PLM Lake and Land Management Corp was selected to develop and implement a three-year program.  In 2025, Cascade Township signed a new multi-year contract with PLM.

View PLM's info sheet to learn more about what they can treat for as well as how to identify different exotic aquatic plant species.

2026 Weed Management Program Information

PLM surveyed the river on May 25, 2026 and determined that no treatment was needed at that time.  PLM surveyed the river again on July 7, 2026 to verify that nothing has changed and treatment was still unnecessary butt found a few areas of Eurasian watermilfoil and Curlyleaf pondweed that require treatment.  Treatment for the areas noted on this map is set to occur Thursday, July 9th. There will be a one day swimming restriction and a three day irrigation restriction within the posted areas, near shore, beginning on Thursday, July 9th.  This restriction is put in place by EGLE to ensure residents are not in the water at the time of treatment.  

The upriver section is ready for mechanical harvesting, which will July 13 and 14, 2026. Please monitor this webpage for updates, or subscribe to our Thornapple River SAD email updates.

Goals of the River Management Program

Remove Eurasian watermilfoil: The primary goal of aquatic plant management in the Thornapple River is to control the growth and spread of exotic aquatic plants. Eurasian watermilfoil, a highly invasive aquatic plant species, is the predominant invasive plant found in the SAD section of the Thornapple River.

Preserve and support native species diversity: Growth of native plants that support the Thornapple River fishery (by creating structure and habitat) will be encouraged, provided they do not excessively interfere with recreational uses of the river (e.g., swimming and fishing) in high-use areas.

Manage aquatic cover (native and invasive): In areas of the SAD where native aquatic plants reach recreational nuisance levels, management techniques that reduce the height of these plants without killing them (e.g., harvesting, contact herbicides) will be used whenever possible. Specific areas will be set aside where native plants will not be managed to provide habitats for fish and other aquatic organisms.  Many of the most noticeable plants are native to the river and are important for sediment stabilization and improving water quality.

PLM's river management permit, through EGLE, only allows treatment of approved target species and locations. While EGLE does allow very limited treatment of nuisance native aquatic vegetation (up to a 50' x 50' area per residential property), that type of treatment has generally not been part of the river management program. The only nuisance native vegetation that has been managed is in the upstream portions of the river that have historically been managed through mechanical harvesting in order to maintain navigation.

Please note: PLM Lake & Land Management Corp. does not manage or monitor levels of PFAS (Per- and Polyfluoroalkyl substances) in the Thornapple River. For more information on PFAS, visit the Township's PFAS webpage.

Methods

  • Herbicide and Algaecide treatments
  • Mechanical harvesting (removal) of nuisance species
  • Water quality analysis
  • Conduct pre- and post-treatment surveys

For more details, please read PLM's Letter to the Township for the 2026 season.

If you have any questions about the program, contact Township Manager Jade Smith at jsmith@cascadetwp.com or by phone at 616-949-1500.