The Roslyn Viaduct Bridge Project was a full replacement of the existing Rte. 25A viaduct over the Hempstead Harbor with a new pre-cast concrete segmental bridge structure. Siefert Associates, LLC and Tully / NAB Construction utilized the innovative solution of a Dual Launching Girder System for the demolition of entire spans in order to minimize the construction time and costs of the project. Pin-connected (hung) spans were lowered to the ground using a jack-down scheme. In addition to demolition plans, Siefert Associates, LLC was responsible for structure lifting operations, temporary support systems, and many other construction engineering services.