By Kevin Wilcox
A team of engineers is mapping utilities infrastructure and examining the geophysical conditions of East Timbalier Island as the first phase of a project aimed at reconstructing this lost barrier island.
East Timbalier Island, as it stands today within the yellow outline, is badly eroded from its condition in 1989. The restoration will re-create lost habitat and contribute to flood risk management for coastal Louisiana. Courtesy of MWH Global
December 9, 2014—Field investigation work is under way on a coastal restoration project southwest of New Orleans to rebuild East Timbalier Island, part of a barrier island chain that separates Terrebonne and Timbalier bays from the Gulf of Mexico. These islands—and the crucial role they play in dissipating storm surges—came into sharp focus in the aftermath of Hurricane Katrina.
"This restoration project may be the last chance the island has," says Nina Reins, P.E., M.ASCE, a senior engineer in the New Orleans office of MWH Global. MWH is providing engineering services for the restoration project and Reins is serving as the project manager.
"The remains of East Timbalier Island are currently composed of two severely degraded segments of the island," Reins says. "The goal is to restore and sustain East Timbalier Island's beach, dune, and marsh habitats."
The project is being conducted by the Louisiana Coastal Protection and Restoration Authority (CPRA) with funding from the National Fish and Wildlife Foundation. The island, located within Lafourche Parish, once comprised several hundred acres of distinct ecological environments, including beach, dune, upland vegetation, tidal flat, marsh, shallow, and submerged aquatic habitats. Under the restoration plan, the opportunity to reconnect the two segments of the island and recreate these habitats will be explored.
"[The island] provides an important ecological habitat, coupled with what it does in providing some level of protection against wave energy and storm surges," explains Anthony Risko, P.E., M.ASCE, a principal engineer for MWH and the project's technical lead. "The ecological habitat component of the island is very important."
One of the key challenges the team will face in the early stages is identifying and cataloging an extensive network of both active and inactive oil and gas infrastructure, including pipelines and well heads, in the vicinity.
There is an extensive network of both active and inactive oil and gas infrastructure, including pipelines and well heads, in the vicinity of the island, which will required a vigorous field investigation. Courtesy of MWH Global
"This project really has a more comprehensive field investigation scope than similar barrier island restoration projects," Reins says. "We will do extensive topographic surveys and magnetometer surveys to identify all those existing infrastructure pieces in order to avoid any surprises."
Reins says that the team has secured a map of infrastructure from a local exploration company, but the data are not up to date and does not include all inactive infrastructure. "We're currently trying to get the data in a geo-referenced format so we can overlay it with our other field investigation results before performing final design," Reins says.
"As we go forward with building the project, we will have various types of platforms that will be used to get into those areas where we want to place material for building the marsh complex, the dunes, and the beach complex," Risko explains. "Some of that may require us to dredge an access channel. We also have some concerns that placing materials on top of some of that [subsurface] infrastructure may end up stressing [it] or interfere with the operators' maintenance access to the infrastructure. "
The project will restore the island so that it resembles a certain point in its history, but what point that is remains to be determined. Because the barrier islands are actually eroded remnants of ancient delta lobes, the team is more focused on the lasting nature of the restoration than in any specific past status. "[We are] not striving for an original condition, but for a condition that we can sustain for an amount of time and [that] benefits the overall system," Reins says. "Right now the island has been breached and is almost eroded entirely. [We are] just figuring out how we can best rebuild it with all the other pieces that are left out there in the system."
Once data from the field are collected and analyzed, the engineers will examine alternatives that involve different island sizes, alignments, configurations, and sustainability measures, Reins says. "At this point we don't want to be stuck [with] one thing in mind, because the data may say something different once we model the conditions," she says.
A key challenge will be identifying nearby sources for the large quantities of sand required to build the beach and dune features of the restoration project. The marsh areas of the project will comprise a mix of sand, silts, and clay. Reins says that the team currently doesn't anticipate employing rocks or other forms of foundation work on the project, but it is too early to rule them out.
"At this point it really depends on the constraints and the plans that we will end up formulating," Risko says. "We will need to do an analysis of the physical and coastal processes in the area and from there—as we formulate the alternatives—we may have a mix of structural and nonstructural solutions, or just nonstructural solutions."
The restoration will be phased, with some phases overlapping. Geophysical surveys and work to identify any potential cultural resources, such as shipwrecks or Native American artifacts, are under way and expected to continue through 2015. Geotechnical work will overlap, beginning in 2015 and lasting into 2016. Modeling and preliminary design will commence in 2015, with a final design and permitting expected to be complete in late 2017.
All elements of the project work are being led and managed by CPRA coastal professionals, in collaboration with experts from within various government agencies and stakeholder groups, and supported by the design team, which includes Coastal Engineering Consultants, of Naples, Florida (which has been intimately involved in several barrier island restoration designs in Louisiana); Coastal Technology Corporation, of Vero Beach, Florida; GeoEngineers, of Baton Rouge, Louisiana; Ocean Surveys Incorporated, of Old Saybrook, Connecticut; Fugro/John Chance Land Surveyors, of Lafayette, Louisiana; and R. Christopher Goodwin & Associates, Inc., of New Orleans and Fredrick, Maryland.