The High Bridge is a masonry and steel arch bridge that gets its name due to the fact that it rises almost 140 feet over the Harlem River, connecting the boroughs of Manhattan and the Bronx. It has been closed to pedestrian traffic since 1960, and was designated a landmark in 1970.
Re-opening the bridge would require the rehabilitation of the peeling paint, corrosion, loose mortar, and frozen expansion joints on the main span and on existing stairways; the construction of new bicycle ramps; and the installation of floodlights on the span.
The B. Thayer Associates survey team was contracted to produce a series of drawings depicting the planimetric and topographic features of the bridge span and gate house areas. Deliverables included cross-sectional data and mapping of the interiorstructure. Horizontal and vertical controls were established via Rapid Static GPS, conventional traversing, and differential leveling techniques.
Special measures were taken to protect historical surface finishes and structures. During interior mapping, challenges included the fact that access to the work area, 17 feet below the bridge surface, was provided by only two manholes approximately 500 feet apart. Therefore, control was set using a total station with an extreme plunge on the scope and elevations were checked via differential leveling and taping. Cross-sections to match the surface were collected with special attention paid to the clearance between the 90-inch aqueduct and the ceiling of the attic area.
High Bridge Restoration Survey Services
Location: New York, NY
Client: New York City Department of Parks and Recreation