But Naor and his partners argue the harbor's in such bad shape officials ought to be more willing to experiment. It's impaired by floating trash and plagued by sewage leaks and wet-weather overflows that make most of the Inner Harbor unsafe for swimming. In spring, it's often fouled with algae blooms and fish kills.

Joseph DaVia, a supervisor in the Army Corps of Engineers' Baltimore District office, which must approve anything put in the water, said Naor's proposed wetland is getting "a little more rigorous review" than the earlier floating marshes because it's so much larger. He said federal regulators have been "going back and forth" between city officials and Naor's representatives trying to resolve differences. He couldn't predict when the plan would get acted on.

The project has the backing of a pair of nonprofits working to improve the harbor.

"We can turn this into a big science and school project," said Scott Raymond, vice president for education at the Living Classrooms Foundation, which operates a charter middle school at its east Baltimore campus.

No one thing will to restore the harbor, said David Flores, water quality manager for Blue Water Baltimore, a watershed watchdog group, but the floating wetlands can provide much-needed wildlife habitat, raise public awareness about the harbor and give it a more natural appearance.

"Historically, the harbor was full of wetlands," said Ted Gattino, managing partner of Bluewing Environmental Solutions & Technologies, one of Naor's partners in the project. The local consulting firm provided the base for the small floating wetland put in the water two years ago by the National Aquarium.

Gattino said he's convinced floating wetlands can put a dent in the nutrient pollution afflicting the Inner Harbor and the larger Chesapeake from sewage treatment plants and urban and suburban storm-water runoff. Nitrogen and phosphorus from those sources feed algae blooms every spring that suck the oxygen out of the water and suffocate fish.

The Harborview marsh could extract more than 70,000 pounds of nitrogen and nearly 8,300 pounds of phosphorus from the water annually, Gattino calculated.

Scientists say floating wetlands can provide food and shelter for ducks and other waterfowl, and they'll give fish and crabs some place to hide from predators in a water body devoid of submerged vegetation. They've also proven effective at reducing nutrient pollution in ponds, lakes and reservoirs. Researchers question, though, whether floating wetlands would have much impact on open bodies of water, especially brackish ones like the harbor where tides can wash nutrient pollution in from elsewhere.

Daniel Terlizzi, a University of Maryland water quality specialist working at the Columbus Center in the Inner Harbor, said a student working under him had found some indication the aquarium's pocket wetland reduced nutrient levels in the water around it, but not enough to be sure.

With the benefits of floating wetlands far from settled, William Dennison, vice president for science applications at the UM Center for Environmental Science, suggested a larger experiment is needed, such as Naor's project.

"That's the right place to do it, in the harbor," he said.

The harbor is relatively enclosed, making it easier to assess the wetlands' impact, he pointed out. And the water there is so degraded that anything that could help ought to be tried.

"We don't have a lot to lose here," Dennison said. "This is a system in need of major intervention, let's go for it."

Even if Naor gets the regulators' OK, he still needs to figure out how to pay for the project, which he estimates could cost $6 million. He hopes to tap private, charitable and government sources.

"Once we get the permits, we'll go find the money,'' he said.

tim.wheeler@baltsun.com

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