Features: What We Build — September/October 2006

Damage Control

Replacement of Florida's Escambia Bay bridges on a fast track

By Bruce Buckley

Crews are pushing hard to replace the first of two Interstate 10 bridges over Escambia Bay near Pensacola, Fla., before a Dec. 29 contract milestone. Credit: photo courtesy of skanska

Crews replacing the Interstate 10 bridges over Escambia Bay in Florida's panhandle are hoping for a happy holiday season.

The design-build team, led by Tidewater Skanska, Virginia Beach, Va., and Flatiron Constructors, Longmont, Colo., is aiming for a Dec. 29 contract deadline to complete the first of two 2.6-mile-long bridges opening, two lanes of traffic in each direction across the bay.

The Escambia Bay bridges, east of Pensacola, were severely damaged by Hurricane Ivan in September 2004 when storm surge displaced several sections of decks into the bay. The Florida Dept. of Transportation then put out a request for design-build proposals in its effort to quickly restore traffic flow through one of the state's major arteries.

To help drive the urgent message home with construction firms, FDOT offered to award a lump-sum $10 million bonus for completing the eastbound span by Dec. 29, 2006. If the team misses the deadline, it will pay a penalty of $133,000 per day. The entire $243 million project is scheduled for completion in November 2007.

Soon after the storm, the state determined the bridge should be replaced rather than rehabilitated and that an incentive-driven, design-build contract would be best, says Steve Hunt, operations engineer with FDOT in Milton, Fla. It was in the best interest of taxpayers to open it as quickly as possible, he says. "Hang a $10 million carrot out there, and you get a lot of attention."

At any one time, the Escambia Bay bridge site is home to as many as 21 large-capacity cranes lifting pieces into place. Credit: photo courtesy of Parsons Brinckerhoff Quade & Douglas, Inc.

While plans for the new bridges were in the works, the state entered into an emergency contract with Gilbert Southern, Lakeland, Fla., an affiliate of Kiewit Corp., Omaha, Neb., to restore traffic across the existing bridges.
Undamaged spans from the eastbound bridge were removed and used to replace gaps in the westbound bridge, creating two lanes of traffic. A temporary steel-panel bridge system, supplied by Acrow Corp., Carlstadt, N.J., was placed in the eastbound gaps to carry 42,000 vehicles a day. The work was completed in 17 days.

While the quick fix got traffic moving, the deal with Tidewater Skanska and Flatiron aimed to provide new bridges that meet future hurricane requirements and traffic demands. Parsons Brinckerhoff Quade & Douglas, New York City, designed the two new bridges being built south of the existing bridges. They will have 10-ft shoulders and can accommodate three lanes of traffic, while the existing bridges have only two lanes with narrow shoulders.

To help the bridges weather future storm surge, the spans are being built no less than 25 ft above mean high-tide levels-more than twice the height of the existing bridges. Over the navigation channel, the spans will reach 65 ft above the water-10 ft higher than the existing bridges. The spans were also designed to meet current ship- impact requirements.

Picking Piles

To help the bridges weather storm surge, the new spans are no less than 25 ft above mean high-tide levels. At the navigation channel, the spans are 65 ft above the water. Credit: photo courtesy of Parsons Brinckerhoff Quade & Douglas, Inc.

PBQ&D designers had to scramble to create a new vision for the I-10 bridges, says John Poulson, design project manager at the firm. "We only had about three weeks to put the proposal together," he says. "In that time, we took the whole bridge to 30% design, with certain elements at 60 to 90%. It had to be at a level the joint venture was comfortable with."

Among the design highlights are the 36-in.-square precast piles, the first time piles that large have been driven on a FDOT project. The larger piles created several advantages, Poulson says. With wider piles, crews would have to drive only five piles for each substructure unit. Standard 30-in. piles would have required seven or more per unit. "Otherwise, we would've needed a pier structure that required more cast-in-place concrete," Poulson says. "There was efficiency in the total number of pieces that went into making a given span." The piles, precast beams and caps each weigh roughly the same. "There was some balance, so once you get your equipment out there, you can pick everything up with the same equipment," he adds.

Crews have battled geotechnical issues, with highly variable soil conditions recorded from pile to pile as they were driven. Credit: bottom photo courtesy of Parsons Brinckerhoff Quade & Douglas, Inc

While the team had a solid design to work from, geotechnical issues at the site were less certain, says Bryan Estock, senior project engineer with Parsons Brinckerhoff Construction Services, Tampa, part of the construction engineering and inspection team. As the first test piles were driven in July 2005, engineers noticed highly variable soil conditions. "It wasn't just varying from bridge to bridge or span to span," Estock says. "It was from pile to pile." As a result, longer piles were used. Most are 145 ft long, with the longest measuring 170 ft and weighing 80 tons.

The team has used a mix of barges and templates mounted on the bottom of the bay to drive the piles. Maneuverability in the shallows of the bay has been difficult, says Jay Erwin, project manager with Tidewater Skanska/ Flatiron Constructors. Nearly 15% of the bridge crosses water between 2 and 3 ft deep. To save time, crews first drove piles in the deepest areas while platforms were built in the shallows.

Coordinating equipment movement also has been tricky. At any one time, the site has 21 large-capacity cranes, two Raymond 60X air/steam hammers, two Conmaco air/steam hammers, a large fleet of barges and other floating equipment.

Hurricane Katrina in August 2005 did little damage at the site, but it disrupted the flow of materials. Precast concrete elements were coming from two yards-Standard Concrete Products in Tampa and Gulf Coast Prestress in Pass Christian, Miss. Standard was not severely impacted, but Gulf Coast was wiped out.

While the team looked for new suppliers, FDOT agreed to modify the design to meet the Dec. 29 deadline. "Under the original design, we would divert two lanes of eastbound traffic onto the new bridge and demolish the existing eastbound sections to complete the tie-in," Estock says. "With the modification, we widened eastbound farther south to carry four traffic lanes, without demolishing the existing eastbound bridge." When the new bridge is completed, crews will finish the westbound span and roadway approaches in time for the November 2007 opening.