Coral Relocation Completed for Miami Harbor Deepening; Project in the Final Stretch
In January, Great Lakes Dredge and Dock cutter suction dredge Texas and a spider barge work in Fisherman’s Channel on a deepening and widening project at the Port of Miami.
Photo courtesy of USACE, Jenn Miller
In November, as part of a major deepening and widening project at the Port of Miami, the port, along with the Corps of Engineers, Jacksonville District, and the National Marine Fisheries Service (NMFS) relocated coral colonies from the project area. Great Lakes Dredge & Dock is working to deepen the harbor channel from 42 feet to 50, and the project area encompasses the diverse Biscayne Bay, requiring extensive environmental monitoring and mitigation.
Laurel Reichold, project manager for the Jacksonville District, said in this last phase of the project, 3.1 million cubic yards of sediment have been removed so far, with another two million cubic yards remaining.
Acropora cervicornis (staghorn coral, an endangered species), relocated by CSA Ocean Sciences, Inc. scientific divers, seems to be adjusting. GPS coordinates will guide monitors directly to the relocation sites. (Photo courtesy of CSA Ocean Sciences, Inc.)
In May 2013, the Corps awarded a $122 million contract to Great Lakes Dredge & Dock (GLDD) to deepen Miami Harbor. GLDD also has two options, $51.9 million and $31.7 million, bringing the total contract value to $205.6 million.
The plan includes components to widen and deepen the entrance channel, deepen Government Cut, deepen and widen Fisher Island Turning Basin, relocate the west end of the Main Channel (no dredging involved), and deepen and widen Fisherman’s Channel and the Lummus Island Turning Basin.
Phase Three of the project, which began in 2012, culminates a process to deepen the harbor channel that began in the 1993.
In 1990, Congress authorized the deepening and expansion of the Port of Miami to 42 feet. Phase One of the project, which deepened the entrance channel and Fisher Island turning basin, was completed in 1993. While the $40 million Phase Two began in the mid-1990s at the South Harbor, the project was never completed. Initially, the contractor encountered difficulties with the limestone bedrock. The contractor subsequently went out of business.
In 2000, the port approached the Jacksonville District to complete the project and determined that rock blasting would be necessary.
The harbor is also home to a number of species that are protected under the Endangered Species Act (ECS) including the manatee, two species of sea turtles and the crocodile. Portions of Biscayne Bay, which surrounds the port, have been designated as a National Park, a Florida Aquatic Preserve and a state Critical Wildlife Area, and are habitat for other protected species.
A diver from CSA Ocean Sciences, Inc. carefully guides crates during transport of coral colonies. (Photo courtesy of CSA Ocean Sciences, Inc.)
Under a strict monitoring program to minimize impacts to the native species, the Corps used confined blasting techniques to break up the bedrock before dredging. In confined blasting, the hole in which the explosive material is placed is capped with an inert material, such as crushed rock. The Corps said this technique has up to a 60 to 90 percent decrease in the strength of the pressure released, compared to open water blasts. Construction on Phase Two began in June 2005 and was completed in July 2006.
In 2012, as part of its We Can’t Wait initiative, the White House Administration announced that seven nationally and regionally significant infrastructure projects would be expedited to help modernize and expand five major ports, including the Port of Miami.
The Port of Miami is one of the top 10 cargo container ports in the U.S. The port is also the “Cruise Capital of the World.” The expedited project would ensure that Florida’s largest port, also known as the “Cargo Gateway of the Americas,” would be completed in time for the Panama Canal expansion project.
Although authorized as a federal project, the Port of Miami deepening became the first federal dredging project to use non-federal dollars for funding. This was very significant for the project, Becky Hope, project manager, Port of Miami, said, and fast-tracked the project again.
In August 2012, a Project Partnership Agreement (PPA) was executed, which allowed the non-federal sponsor to advance the entire federal share of the project. The PPA between the state of Florida and Miami-Dade County, Port of Miami, provided all of the funds for the project, advancing the timeframe for its construction by years. The state of Florida committed $112 million to the project and Miami-Dade County put forth $108 million.
MITIGATION AND MONITORING
The massive dredging project among endangered species and protected habitat required extensive environmental mitigation, including construction of artificial reefs, coral relocation and the creation of seagrass habitat.
In 2014, the Corps and its contractor, CSA Ocean Services, Inc., and the National Oceanic Atmospheric Administration (NOAA) completed all of the coral relocations for the project. Divers relocated more than 1,059 fragments from 211 colonies of staghorn corals from October 26 to November 8 to local coral nurseries at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science. Terry Jordan-Sellers, project lead biologist for the Jacksonville District, said the coral fragments will remain in a nursery for a year before they’re transplanted back to natural reefs near Miami.
Earlier in the project, more than 1,000 scleractinian (hard) corals were relocated from the artificial reef to natural reef sites. Thirty-eight staghorn coral colonies located within 50 feet of the channel edge were relocated outside the project area.
Staghorn corals are a threatened species found throughout South Florida and the Keys. The Corps said many of these coral colonies have survived and thrived since the last major dredging of the harbor that took place in 1993.
DEEPENING AND WIDENING
The project includes widening and deepening most of the major channels and turning basins within Miami Harbor, in five steps: flaring the existing 500-foot wide entrance to provide an 800-foot wide entrance channel, and deepening the entrance channel from a depth of 44 feet to 52 feet; widening the southern intersection of Cut 3 and the Lummus Island Channel, and deepening the area from 42 feet to 50 feet; extending the existing Fisher Island turning basin to the north by approximately 300 feet near the west end of Cut 3, and deepening the area to 50 feet; increasing the width of the Lummus Island turning basic to a diameter of 1,500 feet, and deepening the to 50 feet. The first step widening the entrance channel has been completed and the rest is on schedule to be completed by July 2015.
Great Lakes’ cutter suction dredge Texas is performing the brunt of the work on the project. GLDD President Bill Hanson said the Texas is the most powerful rock cutter dredge in the U.S. “It has been modified specifically to dredge projects like Miami without having to blast,” Hanson said. While the project is permitted for rock blasting, GLDD does not anticipate the need for explosives.
Hanson said after purchasing the dredge Texas, GLDD upgraded it with increased cutter horsepower, a heavier ladder, added buoyancy and more powerful swing winches, improvements to accommodate the extra stress from rock dredging. It was a “huge investment” for a “unique tool for the marketplace,” Hanson said.
In addition to the dredge Texas, GLDD used the trailing suction hopper dredge Terrapin Island, during an initial phase in late 2013, stripping soft material off the rock prior to the arrival of the Texas. The clamshell dredge 55 also arrived on-site in February 2014 to assist with the removal of soft materials off the bedrock and to load chopped rock into scows for placement at the seagrass mitigation site.
The dredging contract also includes seagrass mitigation, for an affected area along the south side of Fisherman’s channel widening area. The Julia Tuttle Seagrass Mitigation Site is approximately four nautical miles up the Intercoastal Waterway from the dredging sites. GLDD created a base fill for the site from approximately 560,000 cubic yards of dredged fill transported to the site via barges. The seagrass will be planted in a two-foot thick sand select fill that is being placed on top of the base fill now.
Hanson said in addition to the Texas, quite a few other innovations have played a part in the success of the project so far. “The GLDD project team, led by Russ Zimmermann, vp and area manager, and Chris Pomfret, project manager, have used many new methods, including advanced technology in cutterhead and teeth design, pipeline wear management, and float hose design,” Hanson said. The project also gave way to new pipeline connection hardware, barge mooring protection systems and improved turbidity management system.
“These types of projects always bring out the best in Great Lakes, and this project is no exception,” Hanson said.
The rock cutterhead design considers many variables, such as the number of vanes, pitch of the vanes, the number and spacing and angle of the teeth, as well as the type of materials used on the wear faces of the cutter and teeth.
The abrasive sands and rock all wear parts of the dredge and slow its production. GLDD closely monitors the impact of the dredged material on the operating parts of the dredge. “Our engineers work hard to find the right materials to use in our pipeline and other wear parts, so that we can execute our projects as efficiently as possible,” Hanson said.Edit Module