Update: Lake Treatments to Begin September 15

September 12, 2025| Environment

By: Holly Odgers

Water treatments will begin next week as part of the ongoing pilot project to reduce harmful algal blooms (HABs) in shallow, near-shore areas. These efforts are being led by Princeton Hydro in partnership with the Lake Hopatcong Foundation, Lake Hopatcong Commission, and the New Jersey Department of Environmental Protection (NJDEP), with funding from the U.S. Army Corps of Engineers.

Starting Monday, September 15, boats will be working in the northern area of Woodport, applying a treatment designed to improve water quality by reducing the nutrients that fuel algae growth (see treatment details below). These algae overgrowths, called harmful algal blooms (HABs), can affect water quality and make the lake unsafe for people, pets, and wildlife. The treatment is expected to take several days.

There are no temporary use restrictions for this treatment; however, Princeton Hydro recommends not drawing water from the lake within the treatment zone within 24 hours of treatment, out of an abundance of caution, and to ensure a successful and even application. Equipment and boats for the Woodport area treatment will be staged in Ashley Cove, so you may notice activity there.

Starting September 22, crews will move to Landing Channel for several more days. Princeton Hydro will post signs in the treatment area with details and any temporary use restrictions, if they apply. Additional treatments are planned in Great Cove and Van Every Cove this fall. 

All products are commonly used as water clarifiers and have been approved by NJDEP.

You can read more about the pilot program at Exploring Solutions to Combat Algal Blooms on Lake Hopatcong’s Shorelines

Water Treatment Details 

Starting September 15, in the northern area of Woodport, a “floc and sink” treatment strategy will be conducted over an area of 47 acres. The floc component will use aluminum sulfate (alum), followed by the sink component, which will be EutroSORB G, a clay and lanthanum-based product. It is anticipated that the treatment will take at least four days to complete. There are no temporary use restrictions during or after treatment; however, it is recommended by Princeton Hydro not to draw water from the lake within the treatment zone within 24 hours of treatment, out of an abundance of caution, and to ensure a successful and even application. 

Starting September 22, in Landing Channel, a “floc and lock” treatment strategy will be conducted over an area of 50 acres. The floc component will use the coagulant LiquiFloc 1% (active ingredient chitosan), followed by the lock component, which will be EutroSORB G. It is anticipated that treatment will last for approximately 4 – 5 days. Princeton Hydro will post signs in the treatment area with details and any temporary use restrictions, if they apply.