Engineering students use plastic to bridge environment, design

By Kate Becker

Take a pristine gully just east of Ithaca, add 8,000 pounds of plastic milk jugs and soda and detergent bottles, and what do you get? Usually, the answer is a trash heap. But recent civil and environmental engineering graduates Jennifer (Jenny) Grubb and Jennifer (Jenn) Preston have a different answer: the Gully Bridge.

Design engineer Jenny Grubb, left, and construction manager Jenn Preston, both recent Cornell civil and environmental engineering graduates, show off the Gully Bridge during its official opening, May 21. On the bridge above them are volunteers, members of Level Green Institute, friends and family. Robert Barker/University Photography

Opened at a ribbon-cutting ceremony May 21, the bridge is made of environmentally friendly Ecoboard (manufactured by American Ecoboard Inc.), a wood alternative produced from these plastic cast-offs and reinforced with fiberglass. Although they resemble pressure-treated lumber, the nearly maintenance-free Ecoboard planks, which on the bridge are connected with aluminum and stainless steel fasteners, do not leach chemicals into the environment as lumber does.

All of which makes Ecoboard perfect for the Gully Bridge's biologically rich site, 10 acres of former farmland owned by Level Green Institute, an Ithaca nonprofit group. The site is on Slaterville Road (Route 79), just past Pine Tree Road.

The land, which Level Green hopes will be used for environmental education programs, is sliced in two by a gully, which in places reaches a depth of 30 feet. The 40-foot long bridge allows access to about one third of the land that previously was inaccessible.

Level Green Director Patricia Haines -- a Ph.D. candidate in Cornell's education department -- approached Grubb, then a junior, about the site in February 2002. Grubb, who had long dreamed of designing a bridge, jumped at the chance to make her dream a reality. A talk by civil and environmental engineering graduate Malcolm McLaren '73, the designer of the first vehicular bridge made of recycled plastic at Hudson River Interpretive Trail, New Baltimore, N.Y., convinced Grubb that recycled plastic was the right material for the job.

Grubb honed the bridge's design while she was a summer intern at the engineering firm of Simpson Gumpertz & Heger Inc. Working late hours off the clock, she wrestled with the challenges presented by her chosen material.

"The plastic lumber industry is very new," Grubb said, and "does not yet have design codes or a design manual." With the help of her colleagues, Grubb adapted traditional wood-design techniques to suit the more flexible, denser Ecoboard.

Preston and Grubb worked together to order materials (provided by American Ecoboard at a considerable discount), obtain a building permit and recruit experts to help them prepare for construction. Anthony Ingraffea, the Dwight C. Baum professor of engineering at Cornell, signed on as the project's faculty adviser and technical consultant. McLaren, who is president of M.G. McLaren Consulting Engineers of West Nyack, N.Y., and Anthony Conte, chief executive of American Ecoboard, also lent their expertise to the project.

Preston headed construction of the Gully Bridge, overseeing excavation, concrete pouring and measurement before the Ecoboard could be put in place. Then, under her guidance, more than 30 Cornell and Ithaca College student volunteers logged a combined 569 hours constructing the bridge.

Their volunteer labor helped keep the project's price tag to a moderate $13,500, supported by 16 local and national donors, including Simpson Gumpertz & Heger, Turner Construction Co. and the School of Civil and Environmental Engineering. The month-long construction phase was completed on May 18.

Gully Bridge is one of Level Green's first projects. A nonprofit group combined with a consulting firm, Level Green seeks to support collaborative initiatives between Cornell and the surrounding rural community. The bridge is both a symbolic and a practical model for projects to come.