Projects under way to prevent and mitigate Harmful Algal Blooms on Lake Hopatcong

State funding, supplemented by local governments and organizations, will support a variety of efforts on New Jersey’s largest lake

Aeration systems, phosphorus-locking technologies, stormwater infrastructure upgrades, and newly planted rain gardens are among the projects residents might see popping up in and around Lake Hopatcong this spring and summer, as the Lake Hopatcong Commission moves forward on implementing a variety of projects to help prevent and mitigate algae growth on New Jersey’s largest lake.

“Since the news of our grant award in early March we have been working with our grant partners to make sure projects are implemented in time for the 2020 season,” said Lake Hopatcong Commission Chairman Ron Smith.  “Our lake community cannot sustain another year like 2019 and we are excited for the installation of the first projects in June.”

These projects, which are supported by $500,000 in harmful algal bloom (HAB) funding provided by a N.J. Department of Environmental Protection Corporate Business Tax and 319(h) grant awarded to the Lake Hopatcong Commission, have been prepared with the technical assistance of Princeton Hydro LLC.

The projects span all four towns around the lake and include a medley of different technological approaches. In addition to the state funding, they are funded through local matches of more than $330,000, including contributions of $75,000 from the Lake Hopatcong Commission, $30,000 from the Lake Hopatcong Foundation, $25,000 each from Morris and Sussex counties, and in-kind contributions from the four lake municipalities: Hopatcong Borough, Jefferson Township, Mt. Arlington Borough, and Roxbury Township. In all, $833,000 worth of projects will be undertaken over the next two years.

The projects follow a 2019 HAB outbreak that resulted in a swimming and watersports advisory on Lake Hopatcong that lasted through much of the summer, an issue that popped up at dozens of lakes in the state and throughout the region. That crisis led to an announcement by Gov. Phil Murphy of $13 million in state funding to support measures that would reduce the likelihood of such blooms in the future. The $500,000 for Lake Hopatcong, announced in March, is part of the first round of state funding available following that announcement, and was secured by the Lake Hopatcong Commission in partnership with the Lake Hopatcong Foundation.

Projects that are slated to be implemented are mostly focused in local, nearshore areas where people have the highest degree of direct contact with the water. They include new types of materials for existing stormwater devices that remove phosphorus, three types of aeration systems, application of a nutrient inactivating product, a treatment of a non-copper-based algaecide, and the use of a compostable Biochar filter media, which will be objectively and critically evaluated by Princeton Hydro through water quality monitoring. Additionally, a rain garden rebate program offered through Rutgers Cooperative Extension will be available for residents within the Lake Hopatcong Watershed.  To register for the free virtual rain garden program on June 4, visit

In addition, the Borough of Hopatcong will be performing a parallel demonstration on the effectiveness of bottom-diffused aeration to document its impact on the Crescent Cove section of the lake. The Lake Hopatcong Commission will also have access to the results from other technologies being tried elsewhere in the state under this HABs initiative. The goal is to find the best solutions to prevent HABs on both a short- and long-term basis.

“Over the past couple months, Princeton Hydro has been conducting field investigations to obtain the necessary permits and approvals to implement these trial projects,” said Princeton Hydro Director of Aquatic Resources Dr. Fred Lubnow. “The first project to be implemented in the coming weeks will be the installation of Biochar, a processed wood product which removes pollutants from the water.”

Princeton Hydro will evaluate specific site conditions prior to recommending proposed project locations in consultation with the Lake Hopatcong Commission and other grant partners.

Cyanobacteria, also known as blue-green algae, are naturally present in lakes and streams in low numbers that can form dense blooms under suitable environmental conditions, such as optimal sunlight, elevated nutrients from stormwater and other runoff, warm temperatures, and calm water. These blooms can discolor water and produce floating mats or “scums’’ on the surface. Under the right conditions, these HABs also can produce cyanotoxins, which can be dangerous to the health of humans, pets and wildlife.

Although Lake Hopatcong never reached the threshold for the cyanotoxins in 2019, some or all of the state’s monitoring stations on the lake showed cyanobacteria numbers above the then threshold for a swimming and water contact advisory during the summer, which resulted in a devastating season for local residents and businesses.

“We hope the lake community doesn’t ever have to go through a summer like 2019 again,” said Lake Hopatcong Foundation Interim Executive Director Lauren Rossi. “These projects are an encouraging start to what we hope will be a long-term investment in the well-being of Lake Hopatcong.”


The Lake Hopatcong Commission is an independent state agency created in, but not of, the New Jersey Department of Environmental Protection. The LHC is recognized as a steward of the lake and watershed. The 11-member Board of State and local appointees include representatives of the four municipalities and two counties surrounding Lake Hopatcong. The LHC is responsible for fulfilling the obligations of the Lake Hopatcong Protection Act, to safeguard Lake Hopatcong as a natural, scenic, and recreational resource. To learn more, visit

The Lake Hopatcong Foundation (LHF), acting as a partner in this project, is a non-profit 501(c)(3) organization, established in 2012 that has worked to improve the Lake Hopatcong region through programs and initiatives centered on the environment, education, community and historical preservation, recreation, arts, and culture. Their mission is dedicated to protecting the lake environment and enhancing the lake experience, bringing together public and private resources to encourage a culture of sustainability and stewardship on and around New Jersey’s largest lake, for this and future generations. To learn more, visit