A large green roof in Washington, D.C., and one of the largest on the East Coast is on the new headquarters building for the U.S. Department of Transportation (DOT).   Gordon Contractors Inc., Capitol Heights, Md., was asked to perform the green roof system installation, including roof membranes and waterproofing for the project. http://www.professionalroofing.net/Articles/Taking-initiative–11-01-2006/964