Otego NY bridge
Norfolk Southern’s (NS) Bridge HA-558.83 crosses over the Susquehanna River in Otsego County, 2 miles northeast of Otego, New York. NS chose Hanson to provide engineering services for the bridge’s pier replacement when its center stone pier began to show signs of disintegration.
The Susquehanna is one of the state’s major waterways, with a ½-mile-wide floodplain and an 800-square-mile watershed area with a Federal Emergency Management Agency (FEMA)-designated regulatory floodplain and floodway.
Because the project site contains a defined floodway, the project team knew that flow obstruction beyond existing conditions could affect hydraulics and cause a rise in flood elevations. Hanson’s design considerations for the pier included size, shape and orientation to minimize hydraulic impacts and maintain regulatory flood elevation levels.
Because the deteriorating stone pier was the only element in need of replacement, Hanson chose to reuse the pair of 125-foot, steel, open-deck spans. A new cast-in-place concrete pier was designed to be supported on drilled shaft foundations placed outside the limits of the existing pier. The width needed to carry the double-track bridge resulted in a long concrete beam. Hanson also provided design and plans for replacing the abutment bearings.
The design included complex, temporary shoring to support the spans while the pier was removed and reconstructed. The shoring carried active rail traffic and was composed of steel pipe piles driven through the existing bridge with bracing and framing elements installed below the deck.
Hanson’s overall project scope encompassed a site survey; geotechnical services; hydraulic analysis of the river’s FEMA-designated regulatory floodplain and floodway, reporting and floodplain permitting support; environmental permitting, including a wetland delineation, an endangered species inquiry and a Section 404/401 permit application, a floodplain permit and agency coordination; bridge design and plan preparation; and construction-phase support.