Replacing an aging bridge connecting West Palm Beach with Palm Beach, the Florida Department of Transportation (FDOT) has built a temporary vertical lift span bridge to keep traffic flowing.
“In undergoing regular evaluations by the state, it came to light that it was becoming structurally deficient and functionally obsolete,”says Geoff Parker, Senior Project Engineer for FDOT. “This is an opportunity for the state to build a new, structurally and functionally sufficient bridge in its place.”
The former Southern Boulevard/SR 80 bridges were built in 1950. It had no bike lanes and narrow sidewalks and traffic lanes. The bridge’s vertical clearance does not meet current U.S. Coast Guard guidelines for bascule bridges, FDOT reports. The old bridge’s piles needed reinforcing with pile jackets.
FDOT is replacing the SR 80/Southern Boulevard bridges over the Intracoastal Waterway and Lake Worth Lagoon. The new bridges will feature a 12-foot-wide lane in each direction, 6-foot-wide sidewalks, 10-foot side pave shoulders and 7-foot-wide bike lanes. Permanent concrete barriers will separate pedestrians from traffic. The bascule bridge also will have four pedestrian balconies, where people can fish off of the bridge, and a new tender house.
The bridge over the Intracoastal Waterway will be a bascule, opening the channel to bridge traffic. The navigable channel will increase to 125 feet wide. Often as aging bascule bridges are replaced, departments choose to build a high bridge, however, FDOT did not have enough land in the urban environment to build such a bridge. The replacement bridge will have a higher vertical clearance of 21 feet. The higher vertical clearance will decrease the number of bridge openings for marine traffic, reducing traffic congestion on the bridge and nearby roadways, explains Angel Gardner, Spokesperson for FDOT.
The lagoon bridge or tide relief bridge will be a low-level, fixed bridge. Additionally, the project includes replacing the approaches and causeway over Bingham Island in between the two bridges. Mar-a-Lago is adjacent to and touches the eastern end of the project. When President Trump is in residence, security zones exist. The department would not discuss any security precautions.
AECOM of Tampa designed the project. Johnson Brothers Corp.,a division of Southland Holdings headquartered in Roanoke, Texas, received the $93 million contract to replace the Southern Boulevard Bridges. The length of the project is less than 1 mile. Work began in April 2017.
A Unique Temporary Bridge
Aiming to avoid congestion and multiple shifting of traffic during construction, FDOT decided to build a 176.5-foot-long temporary bridge to the north of the existing structure. That bridge represents about $15 million of the total cost.
“The new bridge will be built in the same alignment as the old bridge,” Parker says. “The temporary bridge is remarkable in that it is a lift span bridge. The movable portion, instead of teetering like a seesaw, lifts up and down in its entirety. It’s almost like an elevator.”
The temporary structure has one 12-foot travel lane in each direction, shoulders and a 5-foot sidewalk. It is founded on 162 piles for 22 piers. The temporary bridge has 21 spans and has a vertical clearance of 14 feet when closed and 65 feet when open. It opens to allow boats to pass at 15 minutes past the hour and 45 minutes past the hour.
The movable portion is made of steel trusses, and the approaches have steel beams. It has four 75-foot high towers, a 177.5-foot gantry and a control booth. The lift span was less expensive and easier to build than a temporary bascule bridge. FDOT used a similar structure while replacing the Bridge of Lions in St. Augustine.
Johnson Brothers purchased the temporary 30-foot-wide lift span from Acrow Bridge of Parsippany, New Jersey, where it was fabricated. It was shipped to Florida, assembled at the Port of Palm Beach, trucked to the site and lifted into place with two cranes.
“Lift bridges always pose technical challenges, and there were many steps involved in the planned installation of the temporary bridge, requiring close coordination between Acrow’s mechanical, structural and electrical team members and the contractor,” said Scott Patterson, Vice President of Engineering of Acrow Bridge. “The lift span, towers and machinery span were all assembled from Acrow truss panel components on-site and nearby. Large cranes were then used to lift them into place. Additionally, the tower top cross-beams and mechanical systems were installed using a crane.”
The approaches were built with a precast deck panel system. It has pipe piles and prefabricated structural steel slip-on caps.
Construction of Main Spans
With the temporary bridge open, crews began demolishing the main bridge and its bascule piers. The concrete parts of the old bridge were used to create artificial reefs. This was done in collaboration with Palm Beach County’s Department of Environmental Management, Gardner reports.
“The materials used from the bridges not only had to be concrete but they also had to be free of asphalt, a minimum of 500 pounds in size and the rebar cut flush,” she continues. “The material was transported by barge to the designated reef locations. The barge was anchored at the site to ensure maximum stacking of the material at the bottom to create a profile. A crane was used to deposit the materials. To accomplish stacking, a fixed buoy also was used at the site location to assist in marking and guiding the placement of the materials.”
Crews are working on barges. Johnson Brothers has been testing drill shafts for the new bridge’s foundations. Those tests will determine design for the production shafts. Some are 48-inch diameter and others will be 60-inch diameter drilled shafts. The bridge has cast-in-place segments. It will not have beams.
“The riding surface has a certain amount of depth,” Parker says. “It forms a box and gains its strength from the beam-like shape. The segments support vehicular traffic between spans.”
Parker called the bascule component the most critical aspect of the bridge. The contractor is addressing those first. Crews will bring concrete on barges to form the piers to form the foundations and segments.
The deck on the bascule portion of the bridge will be filled with a lightweight concrete to reduce traffic noise. The old bridge had open grating and vehicles passing over it created noise.
The department and Johnson Brothers are taking precautions to ensure no construction debris enters the water.
The lower lagoon bridge will be constructed in phases to minimize traffic delays. It will provide about 11 feet of vertical clearance. All construction activities take place during weekdays so as not to disturb nearby residents. Construction is expected to finish in early 2021.
“The contractor we have on the job, Johnson Brothers, is doing a wonderful job,” Parker concludes. “We look forward to completing a successful project with them.”
Our newsletter right to your inbox.
See stories from other regions.