Stormwater basins built along the Barnegat Bay watershed may be harming the waterway, according to a new study.

The study, prepared for the American Littoral Society by Princeton Hydro, was designed to survey a cross-section of stormwater basins in the bay’s watershed, analyze their ability to treat stormwater and produce solutions to improve treatment.

The study, released on Friday, found that, during rain events, the stormwater basins were failing to provide adequate pollutant removal levels required to meet state surface water quality standards established under the federal Clean Water Act.

In Ocean County, the basins could not adequately remove total phosphorous, total suspended solids and total nitrogen.

The nitrogen levels, according to the study, exceeded concentrations triggering algae blooms and bay health impacts as recommended by federal agencies. 

Altogether, the presence in the bay of the three types of nutrients included in the study are known to degrade native grasses that sustain juvenile fish life, promote the growth of damaging grasses, such as sea lettuce, and help facilitate the invasion of the stinging sea nettle jellyfish.

“In some cases, they're making it worse,” said Helen Henderson, the Littoral Society’s policy advocate, referring to the stormwater basins. “In many of the areas, if they simply left more undisturbed natural land, it would naturally do its job filtering out pollutants.”

The issue with Ocean County’s 2,400 stormwater basins, Henderson said, is that they were built over the course of the last 50 years, normally without pollution controls in mind.

“It's not that they are broken, it's just that they were built, historically, for flood control,” Henderson said.

The solution, she said: Installing so-called ‘retrofits’ on each of the basins so they can better control runoff and prevent it from infiltrating the bay.

The retrofits would alleviate soil compaction and redesign basins so they promote “bio-retention,” where plants and other features would reduce the amount of pollutants that make it to the bay. 

“Stormwater is the most manageable source of pollution to the bay,” said Dr. Stephen Souza, of Princeton Hydro, the primary investigator on the project. “Two strategies are key to saving the bay: cleaning up the current polluting basins through retrofits and reducing the source of the pollution coming from current and future development.”

The retrofits would cost about $100,000 each – adding up to a $240 million total cost to tackle all of the bay’s basins.

“Unfortunately, we have to fix 50 years' worth of land use decisions that neglected the bay, but we will not succeed in restoring Barnegat Bay without it,” Henderson said.

Stormwater basin cleanups got a shot in the arm just last week. Gov. Chris Christie signed a bill Aug. 4 in Barnegat that provides $16 million to be allocated to 25 stormwater retention projects in the bay’s watershed. The same piece of legislation also makes additional grants and low-interest loans available to Ocean County municipalities to put towards stormwater management projects.