Two Marstons Mills bog restoration projects are the work of the Barnstable Clean Water Coalition. Field Operations Manager Luke Cadrin led a recent tour of the first project, which got underway this month.
"So, I guess we should start with what the problem is that we’re trying to solve through this restoration. So, I’m not sure if you guys know about this, but we have a nutrient pollution problem on Cape Cod," Cadrin quipped.
That nutrient pollution problem comes from urine, leaching out of septic systems. To address the problem, Barnstable and other towns on the Cape are installing or expanding municipal sewer systems. But the Barnstable Clean Water Coalition believes restoring these wetlands can be another solution.
Barnstable Clean Water purchased two bog parcels near the headwaters of the Marstons Mill River in 2023, totaling over 64 acres. The goal is to reduce the nitrogen flowing downstream and polluting the Three Bays estuary. The bays have been severely degraded from nutrient pollution, wiping out eelgrass beds and causing fish kills and shellfish closures.
Cadrin said experiments at the smaller of the two bog sites will inform the larger project, as well as other restorations around the region.
"You know, this is a very in vogue thing right now, is bog restorations," he said. "It’s happening all over the place. And we think that the information we find here can advise future ones on water quality restoration. We’re also going to do cost/benefit analysis."
Cadrin said there will be a series of experimental plots, to test which wetland environment removes the most nitrogen.
"We’re gonna have a shallow marsh with mostly cattails," he explained. "We’re gonna have a deep marsh with more like pickerelweed and things like that. We’re gonna see side-by-side exactly how much each attenuates and then have a better idea of which does best."
Zenas Crocker is Executive Director of the Barnstable Clean Water Coalition. He said they worked with scientists at the U.S. Geological Survey and the Environmental Protection Agency to home in on these particular bogs as a potential solution.
"The concentration [of nutrient pollution] that's coming from the groundwater and moving into this area from a fairly large area of heavy population and lots of septic systems, just creates an area that can be used as really a treatment center and remove a great deal, thousands of kilograms, potentially, of nitrogen. And so that's the goal."
Crocker said the idea is to give the water ample time to interact with the wetland.
"The simple concept here is, spread the water out and slow it down," he said.
From there, Crocker said, the wetlands will do the rest.
"Hardly anything is as successful at removing contaminants of any kind as wetlands," he said. "Wetlands, wetland plants, the biological microscopic activity that happens in wetlands – nothing works better at removing everything from heavy metals to pharmaceuticals to nutrients, like nitrogen and phosphorus."
In addition to building filtering wetlands, the restoration will include settling ponds, as Crocker explained.
"We're going to have a combination of ponds," he said. "And if you look at a regular wastewater treatment system, there are settling tanks. And we'll have wetlands, and the wetlands will do a lot of the biological activity that would be occurring in a municipal plant using other approaches. But we can do that naturally."
The water flowing out of the settling ponds will spread out over a large area of wetlands for natural filtration. Crocker likened it to a “mini Everglades.”
Crocker said they are also tapping into the expertise of the cranberry farmers who have been working the land.
"We're not looking to put farmers out of business. We really want to work hand in hand with farmers," he said. "Farmers are, you know, critical to what we're doing, our understanding of everything. They know what the water is. They know how it moves. They know what the conditions are. And so they've been really, really helpful, the local farmers, in helping us understand the system and how to build it.”
Beneath a mat of cranberry vines built up over 150 years of farming, and the layers of sand that farmers added over the years to improve drainage, is a treasure trove of peat. Once exposed, the peat will naturally filter the groundwater and repopulate the bog with native plants. But, as Crocker explained, first the mat must be dismantled and much of the sand removed.
"And so, you build up anywhere from one to three feet of compressed matting," he said. "And so, we want to remove that or chop it up, depending on what we're doing, and really unleash a seedbed that's still there from a couple hundred years ago. And so, you don’t have to do that much. The plants are going to come back naturally."
Crocker said they will plant some beneficial species, but many wetland plants will return on their own.
“At first it'll look like a mud pit," he said. "... But pretty quickly the plants will come back and it'll grow up and look healthy very quickly. And we've seen this at these other sites, so, it's exciting to think you could do something that way and really just let nature take over."
And, Crocker said, this could be the second time these wetlands have helped save the Cape from the looming problems of the day.
"The cranberry bogs in the 1850s probably helped save Cape Cod economically," said Crocker. "Today, we could help save Cape Cod environmentally."
Work on the experimental bog began this month. Work on the larger Marstons Mills bog project will get underway next fall.
