The John T. Brooks Bridge connects Florida's Fort Walton Beach and Okaloosa Island. Built in 1965, the four-lane bridge is the primary connection between Okaloosa Island and the mainland. The design-build team of Superior Construction and WSP is constructing a new John T. Brooks Bridge, a significant upgrade over the original.
Inciting Incident
The ADT on the bridge is more than 66,000, significantly more than when the bridge was constructed. Currently, drivers periodically experience slowdowns crossing the bridge.
Superior Construction photo
The bridge serves as the primary access route to and from Okaloosa Island, which crosses the Santa Rosa Sound near the Gulf of America. Hurricanes periodically hit the area, so the evacuation route is crucial.
Traffic counts, however, have been growing over the years. However, the project has been in the works for decades without moving forward. The urgency for moving forward on the project rose in 2013 when a barge hit the bridge.
The crash was not the first time a boat or barge struck the bridge. However, the 2013 incident damaged a water line that was the sole water source feeding Okaloosa Island, leaving the people without a potable water supply.
The two (eastbound and westbound) new parallel bridges will add capacity as they include three 11-ft. lanes each. The bridges also will have two 10-ft. shoulders and a 12-ft. shared use path, while the original Brooks Bridge had just a 4-ft. sidewalk and 1-ft.-4-in. wide shoulders.
The new bridge provides a vertical clearance of 65 ft., meeting U.S. Coast Guard regulations and offering 15 ft. more clearance than the original Brooks Bridge. The new bridge also is 800 ft. longer than the original, coming in at 2,111.
"Because we raised the vertical clearance, we needed to change an at-grade crossing [on Okaloosa Island] into an overpass," said Matt Durshimer, project design manager of WSP in the United States. "As part of that, we had to create two connector roads to restore what the at-grade crossing was providing."
Superior Construction photo
On the Fort Walton Beach side, the team is realigning a local road to accommodate the new bridge location.
The scope also includes substantial utility relocations as the existing bridge carries water, sewer and fiber optic infrastructure. There also were standard utility relocations that are part of many projects.
Ground Conditions, Coordination, Limited Right of Way
Both WSP and Superior are highly familiar with the area but have faced surprises, nonetheless. The surprise here is the ground conditions.
"One thing you can't fully anticipate until you're on site is the ground conditions that you'll have for driving pile," said Evan Lawrence, construction project manager of Superior Construction. "The piles are performing as we expected, but the driving conditions are challenging, making it more difficult to reach the target layer."
The team has had to adjust the means and methods to reach the necessary depth, which has added time to the task.
Superior Construction photo
"We have to stick the piles far enough into the ground for the design events of the bridge which is a 100-year scour condition and a 500-year scour condition, where the mudline would temporarily scour away during an extreme storm event, and then that mudline will restore after that event," said Durshimer.
There are twelve utility providers that the team needs to coordinate. Scheduling and coordinating utility relocation has been a challenge.
"Getting everybody on the same page to who goes first, and what needs to happen first," Lawrence said. "It's a big scheduling and coordination effort. We spent a lot of time in design, finding the exact homes where each utility can go here."
Limited right-of-way has increased the challenge of relocating utilities.
"We have a very limited distance [a few feet] between the edge of the new bridge and the right-of-way line," Durshimer said.
The limited right-of-way also has necessitated careful coordination of the cranes, equipment, and material delivery/storage.
Original Design
The 275-ft. spliced girder for the main span crossing will have a unique element. The team is using wax, not grout, to fill the annulus of the tendon duct.
Why wax?
"The flexible filler ‘wax' material is semi-solid at ambient temperature, but when heated to around 220 degrees Fahrenheit it becomes a flowing liquid, similar to water," said Durshimer. "This makes it an ideal material for completely filling the long post tensioning ducts. The flexible filler material serves as a means of corrosion protection of the steel strands, preventing oxygen and moisture from coming in contact with the steel strands.
Superior Construction photo
"Unlike a hardened cementitious grout, the wax allows bridge inspectors to readily test and inspect the condition of the strands, and if deemed necessary from signs of distress, allow for a complete replacement of steel strands. The bridge has been designed for strand replacement while remaining in service, avoiding impacts to traffic.
"The use of flexible filler in lieu of cementitious grout requires the structure to be designed differently. Using wax provides an unbonded post tensioning design, unlike grout which bonds the strand to the girder. An unbonded system changes the behavior of the structure and results in a hollow section of the girder where the tendon ducts are placed. This void in the girder is considered in design and required a wider girder web to satisfy the demands of the structure."
This method has been used before on other applications in the United States, but this is the first on a new construction of a spliced girder bridge.
Teamwork
WSP and Superior have teamed up on past projects such as I-20 at Savannah River Bridge Replacement and Roadway Widening project and the Tampa Westshore Interchange project, which is currently in design.
Superior Construction photo
"When we're pairing design, we look at the past relationship between the two companies, and then we evaluate the project specific as to what are our strengths, and for this one we seem to pair up very well," Lawrence said.
The pairing is clicking again as both Lawrence and Durshimer praised the work of the team.
One way the team's success is evident is that the project is on budget. The $171 million project has undergone some minor changes, which have added costs. However, the team also has proposed cost savings through some design and material changes to balance it out.
Construction on the project began at the end of 2022 and is scheduled to conclude in 2028. The date is later than the original completion date due to weather and holiday delays extending the contract time by approximately six months. Other issues involve permitting and the slow pile driving.
The team is trying to make up time.
"We've been doing shift work, so our superstructure crews are working nights. We have our other crews working during days, so it's a 24-hour cycle to get some time back on the job," Lawrence said. "The efforts have helped us gain back some time."
When the new Brooks Bridge is active, it will improve connectivity between Fort Walton Beach and Okaloosa Island and alleviate congestion. The unique structure also will be one that the community can be proud of. CEG
