Hurricanes, Conquistadors, and Endangered Species—The Unique Challenges of Under-Bridge Pipe Replacement on Florida’s Historic Coast

Years of salt exposure from the Atlantic Ocean has taken its toll on two aged water and sewer pipes mounted under the Matanzas Inlet Bridge in St. Johns County, Florida. The inlet, named after the 1565 massacre of 245 French Huguenots by Spanish Conquistadors, is home to a National Monument, four different endangered species, and was hit by hurricanes during both the design and construction of this project. Replacing these pipes over the Matanzas Inlet combined unique technical, environmental, permitting, and construction challenges. The Matanzas Inlet is known for its swift currents and shifting sand bars. This limited construction options for replacing the pipes. The location of the water and sewer pipes was very difficult to access under the bridge—given safety and constructability concerns, the design team developed three different construction approach options for contractors to consider. Additionally, with these pipes being on the coast of Florida, the support structure had to be designed to withstand hurricane force winds and significant thermal variation. The beautiful coastal habitat of the National Monument is home to protected nesting sea turtles, gopher tortoises, the Anastasia Beach Mouse, and the Least Tern (a small ground nesting bird). With multiple endangered species present, the team coordinated closely with the National Park Service throughout the design and construction of the project. Additionally, the team included an environmental consultant that provided monitoring, protection, and educational presentations for the construction workers during the project. These environmental constraints created strict seasonal and daily construction constraints for the contractor. Besides the known environmental challenges of this project, Mother Nature provided two additional surprises. As the project was nearing bidding, the inlet was hit by Hurricane Matthew which impacted the base design information and further deteriorated the condition of the pipes—accelerating the need for the project. Then, during construction the site was hit by Hurricane Irma which required demobilization and stabilization of the site before the hurricane’s impact. This presentation explores the unique aspects of this project, the technical solutions the team developed, and the close collaboration with various stakeholders.