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. Equipment and boats for the Woodport area treatment will be staged in Ashley Cove, so you may also notice activity there.
Starting the week of September 22, crews will move to Landing Channel for several more days. Equipment and boats for the Landing Channel area treatment will be staged on Kingsland Road, so you may also notice activity there.
There are no temporary use restrictions for the Woodport or Landing Channel treatments; 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.
All products are commonly used as water clarifiers and have been approved by NJDEP. Signs will be posted in the treatment areas.
Additional treatments are planned in Great Cove and Van Every Cove this fall.
You can read more about the pilot program at Exploring Solutions to Combat Algal Blooms on Lake Hopatcong’s Shorelines
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. Signs will be posted in the treatment area.
Starting the week of 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. 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. Signs will be posted in the treatment area.
The following FAQs were prepared by Princeton Hydro to provide additional details about the pilot project water treatments to reduce harmful algal blooms (HABs) in shallow, near-shore areas.
Q: What are the benefits of this project?
A: These are demonstration projects to evaluate the cost-effectiveness of proactive and innovative measures to prevent, control, and/or mitigate harmful algal blooms (HABs). By evaluating these treatments here, Lake Hopatcong gains the immediate benefits of nutrient reduction and improved water quality, while also contributing valuable data that will guide future HAB management decisions and inform long-term strategies to help prevent and mitigate shoreline HABs.
Q: What will the lake be treated with?
All of the products being used are commonly used as nutrient inactivators and/or water clarifiers that have been fully approved by the NJDEP. Permits have been obtained from NJDEP for all applied products prior to the start of treatment.
In Spring 2025, Crescent Cove and Ashley Cove received treatments that were placed on the lake bottom to stop algae before it forms. One used a chelated, copper-based product, and the other used an oxidizer (a product that breaks down algae).
In September and October, four types of treatments will be conducted. In Landing Channel and the northern part of Woodport, non-pesticidal products will be used to trap phosphorus (a nutrient that feeds algae) and cyanobacteria in the sediments. In Van Every Cove and Great Cove, which are both known for algae issues, the treatments start by killing the cyanobacteria in the water with an oxidizer, then adding materials to settle and trap nutrients in the sediment below.
Q: How will the treatments be monitored?
Princeton Hydro will monitor each treatment area after one week, one month, and one year to track results and effectiveness.
Q: Can the lake still be used during/after the treatments?
A: There are no temporary use restrictions for any of the treatments; 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.
Q: Who is conducting the treatment?
A: Princeton Hydro and Ready Scout, LLC are conducting the treatments. Ready Scout will conduct the GreenClean applications, and Princeton Hydro will apply all other products.
Q: Are the treatment applicators wearing Hazmat suits?
A: No, they are not wearing hazmat suits. You may see applicators wearing personal protection equipment (PPE) (i.e., gloves, respirators, long pants). Depending on the product used, different PPE may be required. Additionally, you may see the contractors in bright yellow rain gear to stay dry if it is raining or warm if it is windy, which might look like a Hazmat suit.
For example, one of the treatment methods uses the liquid oxidizer algaecide GreenClean 5.0 formula, which is highly concentrated, so PPE is required. Once the formula reacts with the water, it begins to break down into water and oxygen immediately, and is not hazardous. This is the same product that was used to effectively treat the harmful algal bloom in Crescent Cove a few years ago.
Q: How was the public notified?
A: Signs were posted in the treatment areas and/or at the staging locations, and ads were posted in the New Jersey Herald, as required in the project’s Harmful Algal Bloom Management Permit and Pesticide Application Permit. In addition to the requirements, the Lake Hopatcong Foundation and Lake Hopatcong Commission posted information on their respective Facebook pages. Lake Hopatcong Foundation also posted blogs (April, September, October) with detailed information about the treatments before commencement.
Q: Who is funding this project?
A: The cost of a project of this scale, which can often be prohibitive, is being fully funded by the U.S. Army Corps of Engineers’ Engineer Research and Development Center, through funding secured by Princeton Hydro. The Lake Hopatcong Commission and Lake Hopatcong Foundation are supporting the project through coordination and outreach, but no local funds are being used.
