This high-profile design-build project involves the replacement of the existing Dupont Bridge on SR 30 (US 98) over the St. Andrews Bay Intracoastal Waterway in Bay County, Florida. The current 4-lane, 2,750-foot bridge will be replaced with twin 4-lane bridges on a new alignment. The new bridges will have a minimum 75 ft vertical clearance over the navigational channel, which is 25 ft higher than the existing vertical clearance. Key considerations include addressing deep water and scour depths around the channel, designing for significant vessel collision loads, and recognition and accommodation of the glide path for Tyndall Air Force Base, located just 2 miles away.

Project Features:

• Enhanced Traffic Flow: The new bridges will each feature four 12-foot travel lanes addressing current and anticipated traffic demands.
• Share-Use Path: Each bridge will have a barrier separated 12 ft wide shared-use path for bicyclists and pedestrians, along with two overlooks.
• Structural Challenges: The main channel span features a 375-foot-long steel plate girder structure, an exceptional length requiring advanced finite element modeling and careful planning for construction sequencing.
• Erosion Protection: Designed to withstand soil loss due to erosion from major storm events, ensuring long-term structural integrity.
• Resilience & Future-Proofing: Elevated bridge deck to mitigate wave impacts from storm surges and designed to accommodate future sea level rise. Additionally, the bridge is designed to current AASHTO LRFD Bridge Design Specifications requirements for vessel collision loading, with the maximum force being up to 3900 kips at the channel piers.
• Safety Improvements: Design considerations include deep scour mitigation and compliance with Tyndall AFB’s glide path requirements, ensuring both structural safety and operational compatibility.
• Environmental Sensitivity: The project includes the construction of stormwater management facilities and drainage systems designed to protect the surrounding bay ecosystem, along with multiple environmental permits.
• Special Permitting: Involves acquiring a US Coast Guard Bridge Construction Permit.
• Aesthetic Features: Incorporation of design elements that reflect the local environment and community, enhancing the visual appeal of the bridge.