- Associated Press - Thursday, July 22, 2010

ANNAPOLIS, MD. (AP) - Floating wetlands, porous asphalt and living walls are some of the ideas that universities, federal laboratories and private companies are developing to restore the Chesapeake Bay.

Those ideas and others were presented Wednesday in Annapolis at a “Technologies That Can Save the Bay” event sponsored by the Maryland Technology Development Corporation and the Chesapeake Bay Foundation.

Many of the ideas focus on keeping pollutants like nitrogen, phosphorous and sediments out of waterways. Others would remove them once they reach the Chesapeake, where sediments cloud the water and bury grasses, and nitrogen and phosphorous act as nutrients feeding light- and oxygen-robbing algae.

Floating wetlands, for example, are floating mats, rafts or other structures on which plants grow with the roots dangling into the water, removing the nitrogen compounds that come from sewage, fertilizer runoff and other sources. Living walls are made of masonry but have voids in which plants can grow. And porous asphalt allows water to trickle through it into the ground, where pollutants are filtered out and consumed by bacteria, instead of running off into nearby waterways.


Kent Hansen of the National Asphalt Pavement Association said porous asphalt is just like traditional asphalt but doesn’t have sand added to the gravel and thick petroleum byproduct that binds it together. While it is more expensive to install because it is normally laid over a thick gravel bed, it helps eliminate the need for stormwater retention ponds, he said.

“You’re already building this pavement at a site, you may actually eliminate or reduce the size of a detention basin, saving land,” Hansen said, as a video played behind him showing a hose running onto pavement but not off.

Michael Furbish, of The Furbish Company, discussed his firm’s Smartslope system for reinforcing hillsides and other sloping areas that often are subject to erosion. The system uses what he calls “concrete drawers” that are stacked, filled with soil and plants, reinforcing the slope, consuming runoff and nutrients.

Keith Bowers, of Baltimore-based Biohabitats, discussed floating wetlands. Biohabitats has installed four systems, including a small demonstration system at the Living Classrooms Foundation campus in downtown Baltimore. While they have been used effectively on ponds and lakes, in an ecosystem as large as the Chesapeake Bay, they serve primarily as an educational tool, Bowers said.

“What makes ours unique is we are actually harvesting trash, debris, mainly plastic bottles from waterways, urban waterways, and using that as the flotation device,” Bowers said.

The bottles are compacted into a mesh tub and wrapped with coconut husk fiber and plants are plugged into perforations in the mesh. As the plants grow, their roots reach down into the water absorbing nitrogen, he said.

Dr. Bill Hunt, an associate professor of biological and agricultural engineering at North Carolina State University, said they can be effective, opening wider areas than planting only on the bottom near the shoreline.

“The biggest thing is it’s expensive to do the earthwork to get the soil close enough to the surface,” said Hunt, who was not among those presenting ideas on Wednesday. “What’s really nice about these things is they float and it doesn’t matter what the water depth is beneath them.”

Hunt said floating wetlands have been used for wastewater treatment in the western United States and in New Zealand, and their use for removing nitrogen from other waterways is being increasingly investigated. However, not enough data has been collected to justify incentives for developers and others to use them on stormwater containment ponds or other waterways, he said.

Hunt is currently studying floating wetlands on two ponds in Durham, N.C., and says he expected nitrogen removal and water temperature reduction will be the primary benefits.

Chuck Fox, the federal Environmental Protection Agency’s senior bay adviser, spoke at the event, saying regulators can’t “pick the horse to ride,” but can define expectations and let the market respond with appropriate technologies. Fox noted the federal Clean Air Act mandated air pollution reductions and automakers later developed catalytic converters.

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