MVC installs Permeable Reactive Barrier near Lagoon Pond

First-of-its-kind on the Island, PRB was funded by state grant 


In 2018, the Martha’s Vineyard Commission (MVC) received a $250,000 Southeast New England Program (SNEP) grant from the Environmental Protection Agency (EPA) to foster clean water in Lagoon Pond. Working with the University of Massachusetts Dartmouth, the commission studied several locations to install a permeable reactive barrier (PRB), finally settling on 187 Lagoon Pond Road in Vineyard Haven.

The PRB will be the first of its kind on the Vineyard. It’s being installed on the front lawn of a private waterfront residence facing Lagoon Pond.

The grant was part of a local match of $75,000 from both Tisbury and Oak Bluffs, who share the pond. The site was chosen by the commission because it was near a critically impaired pond, could help shellfishing, and could become a model for other Island ponds.

The project involved drilling into the ground 30 feet to install pipes that inject wells in the surrounding area with a mixture of 3,400 gallons of soy milk diluted with 12,000 gallons of water. This mixture attaches itself to the soil, creating a wall that captures nitrogen from the groundwater flowing down into the pond. The bacteria in the ground then use the soy in the ground to grow, which cancels out the oxygen. The bacteria then feed off the nitrogen and release it into the atmosphere as a gas — all through a natural process. The groundwater then passes through the PRB with a significantly lower nitrate level.

MVC Executive Director Adam Turner, who was at the site Thursday, said that PRBs are site-specific, and can’t work for every area, but that it’s one way to address the nitrogen problem in coastal ponds. Excess nitrogen is a problem in every pond on the Island. “This is one arsenal in our toolbox,” Turner said.

Eutrophication — the buildup of excess nutrients — in the pond is the main culprit behind algal blooms, the rapid increase of algae in freshwater and saltwater that comes to dominate an ecosystem. When the large biomass of algae dies, it sinks and blankets the bottom of the pond, where it is then broken down by bacteria. Those bacteria take oxygen out of the pond estuary that other organisms need to survive.

Nitrogen occurs naturally in the environment, but excess nitrogen enters the pond primarily through septic systems and fertilizers from densely populated areas. Excess nutrients cause blooms, blooms cause oxygen starvation, and oxygen starvation smothers other organisms such as fish, shellfish, and plants in the ecosystem.

The PRB was installed by Environmental Strategies & Management, using a remotely operated geoprobe drill. Installation began on Monday, and is expected to wrap up Friday.

Jessica Thomas from UMass Dartmouth, who was part of the project, said the PRB will be studied and monitored for the next two years to determine its effectiveness. Injecting PRBs is not a new technology, but using it for nitrate is a newer application. 

Thomas said the property owner and the neighbors have been accommodating through the entire process. “This is an ideal site, and [they’ve] been amazing,” Thomas said of the surrounding property owners, including Amelia Hambrecht, who owns the home abutting the project site.