Overview

LiRo-Hill provided engineering services on a replacement for a major bridge carrying a highly-traveled route in Brookhaven, New York. LiRo-Hill first assessed the viability of the existing CR16 Horseblock Road Bridge that extends over the Long Island Railroad and Long Island Avenue, then recommended and designed a replacement for the existing deficient bridge.

About the Project

To evaluate the viability of the existing CR16 Horseblock Road Bridge, a four-span, steel-framed structure, LiRo-Hill began gathering information regarding current conditions. LiRo-Hill determined that the bridge’s deficiencies included inadequate width, deficient load capacity, substandard vertical alignment resulting in inadequate sight distance, seismic vulnerability, and non-redundant structural elements. Since the issues with the bridge could not be easily corrected through repairs, LiRo-Hill recommended replacing the bridge. LiRo-Hill then determined project needs and objectives, evaluated the consequences of proposed project actions, and prepared a design for the bridge replacement.

The final design provided a new, more efficient two-span continuous bridge on the same alignment with additional width using steel plate girders. The bridge is located within an existing roadway network, which can accommodate a detour that will allow the bridge to be closed to traffic during construction so the demolition of the current structure and installation of the new structure can be completed during a single stage.

Project Challenges & Solutions

LiRo-Hill collaborated with the LIRR and NYSDOT as well as with the town of Brookhaven and utility owners to come up with the final design solution. NYSDOT’s involvement included approval of waivers for proposed vertical and horizontal clearances, and conducting a public hearing to determine whether the project is in the public’s interest. LiRo-Hill developed and provided a tentative construction schedule to LIRR so it could prepare an estimate of costs associated with flagmen and bus service during the periods of construction when the track will not be operating so the existing bridge can be demolished and the new superstructure steel can be placed.

Due to the proximity of the existing structure to the LIRR track, partial demolition of the existing substructure and construction of new high abutment and wingwalls were coordinated with the LIRR to ensure the track was protected and not impacted. Removal of substructure units and excavation for new abutment footings required the design and installation of braced sheeting and cantilever sheet piles for temporary support of excavation.

Alternatives for Maintenance and Protection of Traffic during construction were developed and evaluated. Keeping CR16, Horseblock Road open to traffic would require multi stage construction, extensive temporary bridge supports, longer construction duration and narrow temporary traffic lanes. The use of an offsite detour using the Long Island Expressway and CR101, Sills Road was recommended and accepted and allowed for construction in a single stage. Existing ramps connecting CR16, Horseblock Road with Long Island Avenue were utilized to create a local detour, allowing for unimpeded use of the area for staging and construction activities. Temporary pavement was constructed in the grassed median on CR16, Horseblock Road and was removed and the disturbed area restored upon completion.

Outcome

Construction contract bids were opened in 2018, with the construction contract awarded and construction started the following year. Construction was successfully completed and CR16, Horseblock Road was opened to traffic in fall 2020, with Long Island Avenue reconstructed and reopened to traffic.