The project specified a “blind side” waterproofing application that bonds chemically to concrete during the curing process, the first of its kind for a mass concrete roadway. The membrane was applied to the stabilized subgrade prior to rebar installation. This sequence required extreme care to be taken during rebar and concrete placement to insure that the membrane was not ruptured or damaged.
The tunnel was designed to include four 63,000-cubic-feet-per-minute (CFM) custom-built jet fans for ventilation and smoke evacuation. Heat detectors and gas detectors were placed at specific points throughout the tunnel and were networked to communicate with a master ventilation control panel. In the event of a fire, the heat detectors would isolate the zone within the tunnel, and the fans would then collectively apply 252,000 CFM of air movement in the appropriate direction to allow occupants to evacuate the tunnel and firefighters to approach the fire without fear of the flames.
The project was constructed on the active airfield with strict limits of disturbance and a 20-foot ceiling due to overhead aircraft. Daily communication with Airfield Operations was necessary to coordinate runway closures and any alteration to the site limits and ceiling. All crews required security badged supervisors for access to the site.
The project required an intensive dewatering effort as the bottom of excavation was 24 feet below the water table. All materials were sorted and stockpiled on site for use as backfill material. The excavation, dewatering, concrete construction, and backfill operations were underway during the peak Central Florida rainy season due to the mandatory completion date. In order to meet the Owner’s schedule requirements, construction took place 24-hours-per-day during this challenging sequence.