Kinston greenroof aids new research |
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With greenroofs becoming a new tool for stormwater management, an extensive greenroof was installed on the Neuseway Planetarium, Health and Science Museum in Kinston in April 2002. The 290-square-foot greenroof now serves as a research and demonstration site for the North Carolina State University Biological and Agricultural Engineering Department and City of Kinston/Lenoir County Parks and Recreation’s Neuseway Nature Center. NC State University’s Biological and Agricultural Engineering Department headed early research efforts to study plant growth and runoff quantity and quality associated with greenroofs. Through these efforts, America. Rainwater leaving the 290-square-foot greenroof is compared to that of the conventional roofing on the building. “The data collected at this site and its sister site in Goldsboro indicated 62 to 63 percent water retention,” says Bill Hunt, NC State BAE stormwater specialist. Peak flow was also significantly reduced. In other words, the volume of stormwater flowing into storm sewers is not only lowered, but is slowed — therefore reducing stream erosion and flooding. An increase in nitrogen and phosphorous loads in runoff from these greenroofs has also been observed, which is bad news for the nutrient sensitive Neuse River. Researchers predict that the increase in nutrients is connected with the media used and the amount of compost it contains. “It means that more research needs to be done to try different types of media to see if other media do a better job of removing nutrients from stormwater runoff,” explains Hunt. The soil media being utilized for the study is four inches deep, lightweight, and composed of a Roof Garden Soil Mix of 55 percent expanded slate, 30 percent sand, and 15 percent compost, according to Amy Moran, NC State BAE graduate research assistant. With the unique soil media, unique vegetation is required. Succulents — low water requirement plants — survive well in the hot, dry, desert-like conditions of the extensive greenroofs. Sedum and Delosperma species were planted. A $5,000 mini-grant through the Neuse Education Team, part of the N.C. Cooperative Extension Service, funded greenroof construction and research. American Hydrotech, Carolina Stalite, Emory Knoll Farms, NCCES, the City of Kinston/Lenoir County Parks and Recreation and NC State BAE all provided either services or materials at a free or reduced price. As a result, the cost of the Kinston greenroof was low — only about $4 per square foot — compared to the average extensive greenroof BMP that ranges from $8 to $15 per square foot. Cooperators were willing to aid in the greenroof construction because there was so little known about greenroof function and because the Nature Center welcomes approximately 60,000 visitors a year. Bill Ellis, Kinston/Lenoir Parks and Recreation Department director, explains the Nature Center’s willingness to house the greenroof: “We wanted to be environmentally friendly, and we wanted to show the general public ways to help the environment that didn’t cost a whole lot.” Greenroofs as stormwater BMPs, while utilized in Germany over the past 30 years, are just starting to catch on in the U.S., according to Moran. And the future for greenroofs looks bright, as demand for them grows alongside increasing urbanization. “Greenroofs have the most potential in downtown high land-cost areas where there isn’t as much space,” explains Moran. Visit the Kinston greenroof at the Neuseway Nature Center, located at 401 W. Caswell Street, Kinston, N.C. 28501 (on highway 11/55 next to King Street Bridge and off of Highway 70/258 Bypass in Kinston). Contact Bill Ellis at 252/939-3335 for more information. -- Lilly Loughner |
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