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Posted Thursday, July 18th, 2019

Residents Advised to Avoid Swimming in N.J. Portion of Greenwood Lake


The New Jersey Department of Environmental Protection is advising the public to avoid swimming in or coming in contact with water in the New Jersey portion of Greenwood Lake  following water monitoring and aerial remote-sensing surveillance today that confirmed the extensive presence of a Harmful Algal Bloom, or HAB.

This is the second major recreational lake in northern New Jersey to be placed under a swimming and contact advisory this summer. Lake Hopatcong, to the south, remains under a similar advisory that has been in place since June 27.DEP: Greenwood Lake Also Suffering from Algal Bloom -- Similar to Lake Hopatcong

There is no scientifically sound treatment to eliminate HABs from water bodies, so advanced and continuous monitoring is the key element in protecting health and assessing when the lake is safe for swimming and recreational activities.

The DEP’s advisory urges the public to avoid swimming or water sports that may result in contact with the water, such as water-skiing, tubing, canoeing and kayaking. There is no recommended limitation on fishing or passive recreational boating that does not have the potential for splashing. However, fish caught in the New Jersey portion of the lake should not be eaten. The public is further advised that pets should not be allowed in the water or to drink it.

The DEP and the New Jersey Department of Health have also advised the closure of public swimming beaches on the lake in New Jersey. The DEP is working closely with the New York Department of Environmental Conservation. The nine-mile-long lake straddles Passaic County in New Jersey and Orange County in New York.

Exposure to cyanobacteria, which causes Harmful Algal Blooms, can result in a range of health effects, including rashes, allergy-like reactions, flu-like symptoms, gastroenteritis, respiratory irritation and eye irritation. Symptoms can occur in sensitive individuals even at levels below the New Jersey Health Advisory Guidance.

If members of the public suspect a bloom, they should avoid any contact with the water and contact the DEP’s hotline at 877-WARN DEP (877-927-6337).

The DEP will continue to monitor water quality through sampling and aerial surveillance. Updates will be provided to the public. It is difficult to predict how long a Harmful Algal Bloom will last. For information on Harmful Algal Blooms and DEP testing and aerial surveillance data, visit