I-275 at I-4 Downtown Tampa Interchange (DTI) Design-Build, FDOT District 7

The I-275 at I-4 Downtown Tampa Interchange was a critical part of Tampa Bay Next. The project was crucial to improving regional connectivity, congestion relief, traffic flow, interstate mobility, and travel time reliability. The project included five new bridges, seven bridge widenings/modifications, four existing bridge coatings, and two existing bridge railing retrofits. American Structurepoint provided several innovative Alternative Technical Concepts (ATC) that improved the original project concept. Most notably, we proposed a way to avoid the complex widening of the existing Ramp NE Flyover by instead constructing a new flyover bridge to carry the I-275 SB to I-4 EB movement and dedicate the existing flyover to neighboring Ybor City movement.

Our approach allowed for off-line construction of the new ramp and flyover bridge, which minimized disruption to existing Ramp NE traffic during construction. With the new flyover constructed, traffic uses this ramp while improvements to the existing ramp are completed, reducing the number of traffic shifts compared to the widening concept and providing three total lanes for these movements, compared to two lanes in the original concept.

Additionally, construction of a new ramp and flyover eliminated over 100 detours, totaling six months of nightly/weekend closures. Other significant ATCs included introducing tie-down slopes on Ramp NE to eliminate the need for an MSE wall and a temporary critical sheet pile wall; modifying the profile of Ramp B to eliminate the potential for drainage challenges and future deck cracking; replacing roadway construction at the North 10th Street and East 14th Street intersection with a two-way, stop-controlled intersection to eliminate drainage reconstruction and reduce road closures; and, using an alternate 60-inch drain pipe to reduce 100 feet of pipe length and keep operations within FDOT right-of-way. In addition, we lowered Ramp NE profile to enable a smoother transition of traffic shifts by expanding a pinch point, which also helped design a critical existing wall strengthening section. Our innovative designs ensure the timely completion of the project while reducing long-term maintenance, simplifying temporary traffic control plans, reducing overall system traffic delay, and minimizing construction complexities.