Posted on October 11, 2022
Many of Louisiana’s efforts to rebuild portions of its rapidly eroding coastline are being overseen by Rudy Simoneanux, the chief engineer for the state Coastal Protection and Restoration Authority.
A graduate of LSU, Simoneaux has been working for the authority for nearly 20 years, helping design and oversee numerous projects, including the half-finished, $87 million, 1,600-acre reconstruction of wetlands and ridge at Spanish Pass in Plaquemines Parish, near Venice.
In an interview, Simoneaux explains how the project was chosen, designed and is being built. The interview has been edited for length and clarity.
How was the Spanish Pass project chosen?
Spanish Pass follows a historic ridge, which some call the Tiger Pass Ridge. It was part of a relic series of bayous that extended from the Mississippi River westward out into the lower parts of Barataria Bay. One of the focuses of the 2017 coastal Master Plan was the restoration of just such historic ridges. As we began to utilize BP oil spill settlement dollars that came to us in 2016, we identified several marsh and ridge projects that would be ideal for implementation, and Spanish Pass was one of those projects. It involves about 8 miles of emergent ridge as well as over 1,600 acres of marsh. And the other thing that made it an attractive project is that it had a renewable sediment source, the Mississippi River. Any time we ever have an opportunity to do a project using sediment dredged from the Mississippi River, we know that the river will, for lack of a better term, refill the hole from which it’s dug.
What issues are you addressing with this project?
The loss of the historic ridge in lower Plaquemines Parish, which was critical, not just from a storm surge standpoint, but in establishing the natural hydrology of that area. Eroded and breached ridges allow water into places it was never intended, leading to marsh loss and changes in fisheries.
How much will this project cost?
It’s a a huge project that required a good bit of lead time and it’s been under construction for about a year now. And we’re hoping to finish this up early next year for $87 million.
How was the project designed?
The first thing we look at is what caused this marsh to go away, and will that make a marsh creation project here go away just as quickly? We studied existing data, water levels, subsidence rates, sea level rise rates — all the forces that we were up against.
We also collected magnetometer surveys to see where there’s existing oil and gas infrastructure. And in this particular area, there was a lot. A lot of the oil and gas companies don’t want you operating near their infrastructure because these projects require a lot of digging and heavy equipment that could impact pipelines or wells. The project you envisioned as perfectly square polygons, easy to design and build, is transformed to something acceptable.
Next, we make sure private landowners whose property is currently degraded marsh and open water want you to build new marsh. We had some pretty receptive landowners on this particular project, and that actually went quite well. We’ve had other projects where landowners, for whatever reason, don’t want us to build the project.
Who owns the land when the project is completed?
The private landowner retains ownership of the property. We’re just getting a servitude that allows us to construct it and access it before and after construction.
How do you assure the marsh will be productive?
We look at the existing healthy marsh in the area. Most is intermediate marsh, in terms of salinity, between freshwater and saltwater marsh, which need to be flooded between 10 and 90% of the time to be productive. The design life for these projects is 20 years. So we look at how often is it going to flood, given the tidal conditions that exist today, as well as the tidal conditions that are going to happen 20 years from now. We determine that sweet spot for water surface elevation over the 20 year period, based on the combination of rising water levels affected by global warming, plus local land sinking rates.
What happens after 20 years?
If that ridge and marsh area is still a master plan priority then, we could potentially put a lift of new sediment on it.
How is inflation affecting restoration projects?
When we bid Spanish Pass, we had a pretty good degree of certainty on prices at that time, in the 2020 timeframe. I can tell you that’s not the case today. Cost estimating has become extremely difficult, unpredictable. Dredging relies heavily on fuel and fuel prices are as volatile as anything. In October 2020, marine diesel that runs these dredges was $2.15 a gallon. A year ago, it was $3.30 a gallon and this October, it’s $4.60 a gallon. So today’s projects are being run with numbers that are $2 a gallon higher, so we have to figure out a way to solve that problem.
How is the project being built?
They started by mobilizing a lot of 30-inch-wide dredge pipeline, beginning at Venice, as close to the river as possible, and adding more pipe as they moved westward. At the outfall, the pipe is pumping out river sand. It’s kind of like going to the beach and throwing chunks of wet sand around. So multiple pieces of earth-moving equipment push around that sediment to create a flat marsh platform. When complete, the ridge will be about 8 miles in length, and the combination of ridge and marsh will be about 1,600 acres of marsh, on the larger side of the projects we’ve constructed. The project is well over 50% complete and will probably be completed by the spring of 2023. The ridge will be planted with shrubs and trees after construction, by another contractor. We haven’t determined exact species of planting yet.