River bed mats filter, cap pollution: Dredging alternative both less expensive, disruptive

By JASON G. HOWE, Foster's Daily Democrat jghowe@fosters.com June 23, 2008 DOVER: Watching Jeffrey Melton spread mat after mat of textured material across the Cocheco River's muddy flats doesn't look much like groundbreaking research. But those mats — composed of activated carbon and "geotextile" fabric — are part of a revolutionary way to treat sediment pollution. And Melton, with other researchers from the University of New Hampshire's Contaminated Sediments Center, is now testing the mats just outside of downtown Dover, where they will eventually be buried by layers of mud and monitored by a group of UNH students. Federal researchers estimate that 20 percent of the top 6 inches of all sediment in U.S. rivers, lakes, streams and estuaries is contaminated. In 2004, the U.S. Environmental Protection Agency reported there were 3,221 fish consumption advisories in state waters. Despite a growing awareness of "green" initiatives and the nation's many environmental woes, sediment pollution does not score high on the "green glamour" scale, Melton said. But the impact is constantly felt by the regular closure of shellfish beds and warnings against eating fish contaminated by heavy metals and persistent organic pollutants. The sum result is long-term damage to the nation's waterways. "You can enjoy a great day of fishing, but if you can't eat the catch, there's a problem," said Melton, who helped create the mats as an alternative. Rather than dredging up the problem, or burying it under several feet of sand, the mats can be used to cap and stabilize pollution where it exists. As it rests beneath layers of sediment, it filters chemicals that pass through it. The mats provide an alternative approach to remediation, while more common treatments include dredging or capping sediment beneath several feet of sand. But dredging is expensive, disrupts habitats and leaves cities and towns with the problem of what to do with toxic sediment. Sand caps have not been proven to be a long-term form of remediation and can hinder boat traffic and impact aquatic life. "There's no silver bullet," said Melton. "What we are exploring is potentially a great tool to add to the tool box." For entire article, see website.