Bridge 03513 supports 1400ft of I-684 over the Tamarack Swamp in Greenwich, CT and shows significant structural deterioration throughout its superstructure and substructure components. The prestressed concrete box beams exhibit multiple spalls, cracks, and exposed reinforcing steel. Elastomeric bearing pads are displaced, bulging, or missing entirely, leading to reduced bearing area and uneven load distribution. The bent caps and abutments show extensive spalling, hollow areas, and exposed rebar, some with visible corrosion. Expansion joints are deteriorated, with full-depth dropped sealant and spalled headers allowing water infiltration, accelerating structural degradation. These combined deficiencies, coupled with the structure’s location over a sensitive wetland and high-traffic corridor, pose risk to the commuters that use the bridge as well as the wetlands below. A complete superstructure replacement is proposed to address the widespread deterioration and restore the bridge’s structural integrity and service life. The conceptual design will evaluate several replacement alternatives, such as prestressed concrete I-girders, steel plate girders, or segmental concrete box girders. With each option we will be considering constructability, durability, environmental constraints, and traffic management. Each alternative will aim to minimize disruption to I-684 traffic and ecological impacts to Tamarack Swamp. The selected design will include new elastomeric bearings, improved drainage and joint systems to prevent leakage, and corrosion-resistant reinforcement materials. By replacing the aging superstructure while maintaining existing substructure components where feasible, the proposed project will enhance safety, reduce maintenance demands, and extend the bridge’s functional lifespan in compliance with current AASHTO and CTDOT standards.