What do you call thousands of gallons of soymilk pumped in a vertical line, 15 feet into the Earth?

Hint: it has nothing to do with a new vegan breakfast option. 

Last week, the Martha’s Vineyard Commission, in coordination with their contractor Environmental Strategies & Management, installed a state-of-the-art "permeable reactive barrier" at the base of Lagoon Pond in Vineyard Haven.

The geoprobe machine is used to drill wells. — Mark Alan Lovewell

The barrier, which uses a soy-based solution to essentially trick bacteria into absorbing and removing excess nitrogen in the groundwater, is the first of its kind on the Vineyard, and was made possible by a $250,000 federal Department of Environmental Protection grant that the commission received in 2018.

After 18 months of comprehensive site testing that involved hand-drilling hundreds of wells to determine the best location for the barrier, as well as $75,000 matching town grants from Vineyard Haven and Oak Bluffs, the permeable reactive barrier finally went into the ground over the course of last week.

At the site UMass Dartmouth graduate student Jessica Thomas explained that the “soymilk” is actually a chemical solvent that reacts with the groundwater, creating a low-oxygen environment for bacteria. When bacteria don’t have oxygen to eat up, they go for their second choice, nitrogen — a process that gets initiated as water flows through the barrier.

The property is located right on the edge of Lagoon Pond. — Mark Alan Lovewell

While PRB’s date back to the eighties, the use of them for denitrification is still a young science.

“The way the PRB’s work for nitrate, is that you inject the soymilk, and it creates this wall effect,” Ms. Thomas explained. “Using it for nitrogen is a newer application of this technology.”

Commission executive director Adam Turner said that he hoped the barrier could serve as one of many tools in the "commission’s arsenal” to help fight pollution in the Island’s ponds. And as the first of its kind on the Vineyard, Island water experts and scientists plan to study the barrier’s effectiveness, testing how its denitrification process impacts the quality of the groundwater entering the pond.

The Lagoon is one of the most impaired coastal ecosystems on the Island, and excess nitrogen from septic systems can lead to harmful algae blooms that suffocate the pond’s benthic habitat, leading to shellfishing closures and other, more long-term environmental impacts, such as eel grass die-offs.

Adam Turner thanked homeowner Emily Hambrecht for her cooperation. — Mark Alan Lovewell

Located just off Lagoon Pond road near the Martha’s Vineyard Museum, the barrier’s site is actually on private land owned by Emily Hambrecht. Mr. Turner thanked Ms. Hambrecht for her cooperation during the research and installation process.

“We wouldn’t have been able to do it if she wasn’t so fantastic,” Mr. Turner said.

Last week, the faint tut-tut of a pump indicated that the soymilk solvent was being injected into the ground, while a ten-foot tall, remote-controlled well-drilling machine called a “geoprobe” was prepped for use. Although Ms. Hambrecht’s yard looked like a barren, almost extra-planetary construction site, Mr. Turner and project manager Brooke Paulsen ensured that the land would be back to its original condition after the installation.

The PRB is expected to last between ten and 20 years, although its exact lifespan is unknown. 

The commission and Ms. Thomas hope to eventually figure out the most efficient locations that they could put PRB’s around the Lagoon to get the pond below the TMDL, or total maximum daily nitrogen load. Until then, they plan to study the impacts of this particular PRB. It is the first, after all.

“It’s not a silver bullet fix,” Ms. Paulsen said. “It’s one of many options that we now have.”