Thursday, May 22, 2008

Planting Rain Gardens Can Cut Neighborhood Pollution

SPM Wire Homeowners can help eliminate neighborhood pollution simply by planting an easy-to-construct garden on their property.

According to new research, properly designed "rain gardens" can effectively trap and retain up to 99 percent of common pollutants in storm runoff, potentially improving water quality and promoting the conversion of some pollutants into less harmful compounds.

The affordable, easy-to-design gardens could help solve one of the nation's most pressing pollution problems, say University of Connecticut researchers who have been studying the issue.

More than half of the rainwater that falls on a typical city block, one with 75 percent or more impervious cover - such as roads or parking lots - will leave as runoff, according to the Environmental Protection Agency. This runoff includes metals, oils, fertilizers and other matter.

Easy-to-construct rain gardens - shallow depressions in the earth landscaped with hardy shrubs and plants such as chokeberry or winterberry surrounded by bark mulch - offer a simple remedy to this problem.

The gardens are designed to replicate the natural water cycle that existed before roads and other impervious surfaces were built, say Michael Dietz and John Clausen, the two researchers who conducted the new study.

"Rain gardens are pleasing to look at, while they are performing an important function," Dietz says.

As the water collects and soaks into the rain garden, it infiltrates into the ground rather than draining directly into sewers or waterways. The gardens work well year-round.

Information about designing and constructing rain gardens can be found on the Internet on such Web sites as http://clean-water.uwex.edu/pubs.

In their two-year study of roof-water runoff, the researchers found that rain gardens significantly reduced concentrations of nitrates, ammonias, phosphorous and other pollutants reaching storm drains. In addition, design tweaks that allowed polluted rainwater to pool at the bottom of the gardens permitted bacteria in the soil to convert harmful nitrates into nitrogen gas, preventing them from entering the groundwater.

Dietz and Clausen hope their results will encourage developers and homeowners to create these low-tech rain water collectors. Their research is being published by the American Chemical Society, the world's largest scientific society and a nonprofit organization chartered by the U.S. Congress.

Michael Dietz, University of Connecticut

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