H&H is currently finalizing engineering services for the superstructure replacement, foundation rehabilitation, and seismic retrofit of six bridges in the City of Mount Vernon, NY over the Metro-North Railroad New Haven Line. Each bridge was constructed in the late 1890s and is in poor physical condition with low load postings or closed to traffic. The existing single-span bridges are non-redundant through girder and/or truss. The assignment began with four bridge locations, and two additional bridges were later added to the contract as the project was advancing smoothly.
H&H provided complete engineering services from initial inspection and load ratings through final design documents. The 6th and 10th Avenue bridges were combined into a design-bid-build contract. The 14th Avenue, 3rd Avenue, Fulton Avenue, and South Street bridges were advanced to preliminary design and packaged into an RFP for advertisement as design-build contracts. H&H will act as the railroad’s engineer providing design and construction review. The initial scope of the project included field inspection, load ratings, soil & environmental investigation; bridge repair/replacement report, and HAER; preliminary bridge, geotechnical, and approach design; final design, construction cost estimate & schedule, specifications and, construction support services, and shop drawing review.
The 14th Avenue Bridge opened in July 2019; the 6th Avenue Bridge opened in November 2020; the 10th Avenue bridge opened in July 2021; and most recently, the 3rd Avenue Bridge opened in August 2021.
The rehabilitation includes removing the upper courses of the existing ashlar stone masonry abutments and constructing new bridge seats and redundant girder superstructures. The rehabilitated bridge abutments include micro piles, tiebacks, and mechanically stabilized earth elements to meet seismic demand requirements. The design integrates adjacent approach intersections to provide safety improvements (ADA compliant), traffic signals, and street lighting. The Fulton Avenue bridge included SHPO report and incorporation of interpretive panels into the bridge walkway.
Photo is the of the completed 3rd Avenue Bridge.