Algae Bloom Closes Manasquan Reservoir To Water Activities

HOWELL, NJ — A harmful algae bloom has prompted authorities to ban water activities at Manasquan Reservoir until further notice. Drinking water pulled from the reservoir is being treated to remove the algae and any of its byproducts, a New Jersey Water Supply Authority official said.

The Monmouth County Park System announced the ban on wading and other water sports at the 1,208-acre park on Wednesday and shut down its boat rentals until further notice on Thursday, according to notices on the park system website. The shutdown followed testing of water at the reservoir by the New Jersey Department of Environmental Protection.

"A confirmed Harmful Algal Bloom is present at the Manasquan Reservoir with levels quantified at or above the NJ Health Advisory Guidance," the notice on the parks system website says. "Do not drink or have contact with the water including, but not limited to, swimming, wading, and watersports."

Swimming by people and pets is banned at the reservoir under Monmouth County Parks System rules.

The notice said fish caught in the reservoir should not be eaten and pets should not contact or drink the water.

The algae is the same type that caused Lake Hopatcong and Swartswood Lake to be closed to swimming earlier this summer. In both of those instances, harmful algae blooms developed when cyanobacteria overproduced in the lakes, the DEP said. In the right situations (sunlight, hot and calm waters and high nutrients) the bacteria can cause a bloom that's toxic to humans and animals.

The 770-acre reservoir is as much as 40 feet deep and can hold up to 4 billion gallons of water as part of the Manasquan River system. Water from the river enters and exits the reservoir through the inlet/outlet tower in the front of the main dam.

The 4-million-gallon Manasquan Water Treatment Plant treats the water from the reservoir and provides 60 percent of the potable water used in Brielle, Sea Girt, Spring Lake, Spring Lake Heights, and Wall Township, according to the New Jersey Water Supply Authority website.

That treatment process includes destroying the algae and removing it from the water before it is released as drinking water, said Paul McKeon, manager of the Manasquan Water Treatment Plant.

The process in the treatment plant uses ozone, which destroys the algae, and the dead algae is then removed from the water with a coagulant, McKeon said.

"The processes of ozone and coagulation should remove anything that is a byproduct of the algae," McKeon said. The water treatment plant draws its water from a few feet down in the reservoir, he said.

Reservoir officials posted on the reservoir's Facebook page that those with additional concerns should contact the Monmouth County Health Department at 732-431-7456 or health@co.monmouth.nj.us.

Manasquan Reservoir experienced an algae bloom closure in 2016 that lasted about two weeks.

This article has been updated with contact information for the Monmouth County Health Department. It has been additionally updated to reflect that swimming is not permitted at the reservoir at any time.

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