Overcoming geotechnical challenges to expand Florida’s biggest port
GLF Design-Build Team / Tampa, Florida
Port Tampa Bay is Florida’s biggest port, and critical to the state’s economy. The port handles more than 34 million tons of cargo per year, about 40% of all cargo moving in and out of Florida.
This cargo includes phosphate, steel, petroleum, and vehicles from trade partners including Argentina, Australia, Brazil, Canada, India, Japan, Mexico, Russia, Trinidad, and Turkey. Tampa Bay is also among the top eight US cruise ports, handling almost a million passenger moves per year.
In 2014, Mott MacDonald was selected to lead the design for the Eastport Development, a major expansion and upgrade at Port Tampa Bay. A wharf and storage yard were projected to be built over the spoils of a dredging project, which posed complex geotechnical challenges.
About 45 feet below the spoils is a very hard layer of weathered limestone and calcareous clay, making it difficult to drive piles.
The Eastport Development includes a new 400-foot wharf, complete with breasting dolphins, high-strength mooring points, a hopper platform, and a 20- to 25-acre, high-capacity, concrete-paved storage yard. High-mast lighting, reconfigured roadways, and fire and potable water services are also included in the project scope.
Mott MacDonald was selected as the Lead Designer for a design-build team led by GLF Construction Corporation of Miami.
The mooring installations at the Eastport Development are being designed to be flexible enough to handle different sizes of ship and different types and weights of cargo.
Mott MacDonald worked with the Orlando company Ardaman & Associates to conduct geotechnical testing to determine the properties of the dredging spoils and their ability to carry loads.
Pending the full outcome of geotechnical testing, Mott MacDonald focused on the use of predrilled pipe piles, though these can produce extremely high vertical-load capacities coupled with the extremely low-tensile capacities of the piles. This can result in pulling upward on mooring structures rather than pushing down.
To cope with this problem, we suggested a system of “rock sockets.” Once the desired tip elevation is reached for the piles, material is excavated from the interior of the pile. A smaller-diameter casing is counterbored inside and filled with concrete to prevent the pile from being pulled out.
Because the Eastport Development will be able to accommodate a wide variety of ships, it can replace the function of several purpose-built facilities.
Eastport has a large site, but not much of it is paved with high-strength concrete that can carry heavy loads. The upgrade makes it possible to handle a range of products from steel to cars to construction equipment. Multiple vessels can use the same facility, resulting in cost savings.