Falmouth Conservation Commission Approves Innovative Nitrogen Reduction Plan For Mill Pond
The Falmouth Conservation Commission has given the green light for a plan to reduce nitrogen entering Mill Pond in East Falmouth.
Kristen Rathjen, representing the Falmouth Water Quality Management Committee, went before the commission on June 16 to outline the committee’s plan for a detention pond in the cranberry bogs located upstream from Mill Pond, and to install a removable wood chip-based permeable reactive barrier that will intercept nutrients within the surface waters of Backus Brook.
Mill Pond has an extensive history of pollution problems, specifically due to the commercial cranberry bogs located upstream. The pond has been plagued with nitrogen and phosphorus from the bog, giving it an especially scummy appearance during the summer of 2018. The proposed plans will mitigate those nitrogen inputs by using permeable wood chip barriers, which have been shown to stimulate bacteria that reduce nitrogen levels in the water entering the pond.
The proposal was approved unanimously and Ms. Rathjen, who serves as a technical consultant for the committee, said the committee hopes to move forward with implementation as soon as possible.
“We need the order of conditions,” Ms. Rathjen said. “We have time of year restrictions for fish that are in the pond at the end of June and we have to work around the cranberry harvest. We don’t want to impede the cranberry operations in any way. We’re starting to coordinate with the bog owner and the DPW to see what our options are, but we’re hoping for this year.”
The committee is working with the University of Massachusetts Dartmouth to monitor the water levels of Mill Pond. The plan was initially piloted in Barnstable, to demonstrate to both the town and bog owners that this is a promising technique. It is an adaptive process that will likely change with the environment. Ms. Rathjen said a small-scale implementation has already been in place in the bog for about a month and though official nutrient analyses are yet to be completed, the numbers look encouraging.
“How the wood chips work is by stimulating the bacteria that’s there that converts the nitrogen,” Ms. Rathjen said. “To do that, you need anaerobic emissions, so no oxygen. We know that there’s something positive going on because when you’re measuring the oxygen in the stream before it hits these bags, you have good healthy oxygen. And then if you take the oxygen measurements within the bags [of wood chips], there’s next to no oxygen. So that’s a really good preliminary sign until we get those nutrient results back in a few weeks.”