Floating islands a pollution solution

DURHAM -- At Hillandale Golf Course and the Museum of Life and Science, the Falls Lake cleanup has begun.

That's the idea, anyway.

N.C. State University and the city of Durham launched 16 "floating islands" this week in an experiment to see whether a Carrboro company's product helps rid ponds of nitrogen and phosphorus pollution.

"If it does, you might be able to start seeing more and more of these across the Triangle because it's a relatively easy fix," said Bill Hunt, an agricultural engineering professor and extension specialist at NCSU.

The islands were finished and floated Wednesday and Thursday, and right now they look like 400-square-foot mats of green fiberglass, studded with sprigs of greenery. What interests the scientists and city officials is that, as the plants grow, they take nutrients out of the water.

Nutrients, that is, such as the nitrogen and phosphorus with which Jordan and Falls lakes are over-supplied, posing a cleanup dilemma that could cost Durham and other local governments in their watersheds hundreds of millions of dollars to fix.

Floating islands could be a lot of help.

Twelve islands now float in a pond at the golf course and four in a much smaller pond at the museum.

The islands are mats of polymer fiber, about 10 inches thick and buoyant enough to support several people, into which "obligate wetland plants" - plants that naturally occur in wetlands - are set.

Both ponds drain into Ellerbe Creek, the Falls Lake tributary that carries the highest levels of nitrogen and phosphorus downstream.

"It's really simple technology," said Rob Crook, co-owner of Floating Island Southeast. "We're just creating an environment for what already exists in nature."

Crook contacted Hunt, who hears from lots of vendors who want the university to test their "whiz-bang products." He usually remains a skeptic, but when he investigated the biological basis of the floating islands, he figured that they could work.

"Could work at least to the point we should test it," he said. "I contacted my colleagues with the city of Durham ... and asked if they'd be interested."

They were. The greatest public expense in ridding the reservoirs of excess nutrients is fitting out existing subdivisions, shopping centers, office parks and so on with new, state-of-the-art stormwater-control and filtering systems.

"All of the cities of the Jordan Lake watershed, they have a monumental task in front of them to figure out ways of retrofitting," said NCSU scientist Ryan Winston, and requirements for cleaning Falls Lake take effect in January.

"This would be a great retrofit for a lot of these [stormwater-retention] ponds around here," said Dave Brown, an engineer with Durham's stormwater division.

"We're real excited," he said, "because a study like this has never been done."

A Montana inventor named Bruce Kania came up with the idea for floating islands and founded Floating Island International LLC in 2000. Out West, they've become common, but primarily for their aesthetic value, Hunt said.

"We're concentrating on water quality," said Crook, the dealer.

Crook said he saw the islands in a TV program and thought, "That's a really cool idea." He contacted Kania, who put him in touch with the similarly minded Triangle resident Ed Davis. Crook and Davis started their business in 2009 as a licensee of Kania's company.

Cost is low

Islands cost around $30 per square foot, said Hunt. The city of Durham, the state Department of Environment and Natural Resources and the federal Environmental Protection Agency are together spending about $180,000 on the test, in which water will be tested flowing into and out of the subject ponds for a year.

If they work, the islands could be put in existing retention ponds with no need for new construction or re-engineering the ponds, and no need to acquire land for new installations at taxpayers' expense, Hunt said.

Another advantage is "a really pretty one," said Winston. "When all the plants have grown up, you don't actually see any of the green plastic. It's just a lush green environment on top of the pond, so in theory there's a habitat for fish, frogs, wildlife as well."

With two polluted reservoirs in the Triangle, the N.C. State-Durham experiment has near-term implications close to home. But it is being watched elsewhere too, Hunt said.

"People have heard we're actually studying this here in North Carolina, and people in Alabama, Georgia, Virginia, Maryland, they're very curious as to what we find."

Time and data will tell.

"If it doesn't work," he said, "then we've learned that."