HARRISON — Those hanging out on the water in the Friendly Village have likely noticed the floating blue curtain-like barriers, which project members say appear to be doing what they’re intended to do — filter out phosphorus and prevent it from entering the town’s lakes.

The project — which studies Crystal and Long lakes — is a partnership between University of Southern Maine professor Karen Wilson and her student Aaron Riccardi, the Lakes Environmental Association in Bridgton and Scarborough-based Mackworth-Enviro. It is funded through a matching $24,000 grant awarded by the Maine Technology Institute.

One temporary, experimental barrier was placed in each body of water on June 18 — around the culvert drainage inlet at the Long Lake boat launch and the ditch drainage inlet by the Crystal Lake boat launch. On Tuesday, Assistant Director of the Lakes Environmental Association Colin Holme said the barriers catch run off water from the moderately developed residential areas on the lake and partially from Route 117.

Holme said his organization was in contact with Wilson, who put him in touch with Andrew McCusker, president of Mackworth-Enviro, which specializes in making aquatic barriers and screening solutions.

“They were looking at trying out this new experimental barrier for treating more rural stormwater, not urban,” Holme said.


This was a perfect fit for the town’s two major bodies of water. 

McCusker said his company has worked with technology called aquatic filter barriers and has had success in reducing bacteria in drinking water reservoirs and at beaches. But instead of reining in bacteria, this project collects phosphorus and other sediments as they run into the lake.

The roughly 600-foot long barriers for the Harrison project weigh upwards of 800 pounds and have curtains that float on the surface and filters — six two-by-two-foot windows — that allow water to pass through while catching particles. There’s a ballast at the bottom of the barrier to keep it anchored.

“We design them so the way they sit, they enclose an area so that the water that’s coming through there has to pass through (the filter). It can’t get under it, it can’t get around it,” he said.

Elevated levels of phosphorus can wreak havoc on lake ecosystems.

“It is a primary concern. …  Stormwater is carrying the nutrient phosphorus into the lake and sediment. The more phosphorus you put into the system of the lake, you get more algae growth. People don’t want to recreate on the lake because it’s murky. … And at some point, it becomes a health problem,” Holme said.


He noted there isn’t any health concerns because of phosphorus levels in the Harrison lakes. But higher amounts of phosphorus cause blue green algae blooms and a component of the algae can make people sick in various ways. High levels of algae also result in anoxia, or depleted oxygen levels at the bottom of lakes, which can affect drinking water. This isn’t an immediate concern for Harrison as Long and Crystal lakes aren’t a source of drinking water, he added.

Wilson and Riccardi are in charge of sampling the water inside and outside the barriers, according to Holme and McCusker. While McCusker hasn’t been able to fully analyze the data yet, the signs look positive.

“We started to see some results,” he said. “Generally speaking, we’re getting really good reductions in total phosphorus and phosphates.”

Riccardi said he, Wilson and other colleagues are still crunching the numbers, but knows the barriers are doing their jobs.

“So far it looks like most of the lakes are reducing the nutrients. We haven’t had a lot of rainfall this year so it’s one of these things we’re trying to catch up with some of these storm events,” he said, noting during the last rain storm, he witnessed the sediments going into the screens. “The outside of the barrier content is a lot cleaner than in the barrier (where nutrients and sediments are caught).” 

The barriers will remain in the water until the end of this month or sometime in September, Holme said. Once the data is tabulated, he hopes it will be a filtering system to use in the future.

“It’s been a great partnership with (Wilson) and Macworth and hopefully we will find some really interesting data …  and see whether this is a viable way to treat stormwater in the lake for some certain types of projects,” he said.

Riccardi said formal results will be presented after the data has been reviewed and the barriers removed from the water. 


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