Expert Interview with James Costello, Marine Structures Expert

James Costello has more than 30 years of experience in structural and marine design. A registered professional engineer, Mr. Costello’s expertise includes the design and retrofit of buildings, locks, dams, bridges, tunnels, and marine structures and extensive design work for floating and float-in structures. Structure types also include in-the-wet hydraulic steel and concrete structures such as floating lock guide walls, dams, and gates. James has completed a significant amount of work on high-profile projects for the U.S. Army Corps of Engineers, and his diverse experience includes habitation modules for the United States Space Station. Mr. Costello holds a Master of Science degree in Civil Engineering from the University of Washington and a Bachelor of Science in Civil Engineering from the University of California.

What are some of the challenges of marine structural design?

Design durability to meet the needed design life is one of the greatest challenges we face. The salt water marine environment, which degrades many materials, combined with aggressive loads is a recipe for a high-corrosion environment. I am constantly challenged with selecting the right material and coating for our structures to mitigate corrosion and loads. Design life expectations are growing—in the past we designed structures for a 50-year life, but now a 100-year life is more common.

What’s the most challenging project you have worked on and what was the outcome?

The most geographically challenging project I have worked on was the Dahla Dam Rehabilitation project for the U.S. Army Corps of Engineers Middle East District. Dahla Dam, the second largest dam in Afghanistan, was constructed in the 1950s, and lack of maintenance caused siltation in the dam. The lack of maintenance, coupled with seismic challenges and dangerous site conditions, made the project extremely challenging. For this project, we used a redundant truss design to help prepare for future strains and build resiliency. The successful outlet works structure now provides water for the farmers, reestablishes farming in the region, and allows for more economic stability for the country.

How have Tetra Tech’s marine structure designs helped create more sustainable communities?

A good example of work that benefited both the client and the region is our design-build Inner Harbor Navigation Canal hurricane risk reduction barrier project in New Orleans for the U.S. Army Corps of Engineers. The Corps’ goal was to reduce the risks associated with hurricane events for New Orleans residents after Hurricane Katrina. Our design of the Lake Borgne surge barrier allowed residents to rebuild in the flooded region, reduced insurance rates, stimulated economic growth, and increased quality of life for residents. These large marine projects are substantial infrastructure for the region, and the benefits extend beyond the client and into the community.

How does Tetra Tech help clients manage risk through resilient design?

Structural resilient design is best defined by investigating the response to the structure beyond minimum design loads. For the Inner Harbor Navigation Canal project design, we managed risk by not only meeting the 100-year storm event standards but also analyzing effects beyond these storm events. We investigated larger storm events and how they would affect the structure including how much water overtopping would occur and future sea level rise. We designed the walls to have reserve capacity so wall extensions could be added in the future.

As the engineer of record for the complex Inner Harbor Navigation Canal project, what lessons did our team learn and what innovations did we apply that would be beneficial information for coastal cities considering large scale coastal protection projects?

One of the lessons we have learned from our marine work is that establishing redundancy in the design is essential early in the design process. We designed the Inner Harbor Navigation Canal hurricane risk reduction barrier project as a redundant truss, so it could withstand any element in the gate failing, remaining safe and fully operable. This design gives the owners the resiliency to operate the gate in the event of an issue such as a storm. Through our work on the Inner Harbor Navigation Canal, we also learned we can mitigate environmental impacts to a harbor or near shore environment by adding environmental gates to large surge barrier protection projects.