SC Considering $1.75B Seawall
The United States Army Corps of Engineers has recently announced the preliminary proposal of a $1.75 billion seawall around the lower Charleston Peninsula in South Carolina.
However, with possible variations, the cost of the seawall could inflate to as much as $2.2 billion.
About the Project
Back in 2018, the Corps, Charleston District received $3 million in federal Emergency Supplemental Funding to study coastal storm impacts on the Charleston Peninsula. In partnership with the City of Charleston and its stakeholders, the Corps was also instructed to develop an economic- and environmentally-friendly solution to effectively mitigate long-term storm risks in the area.
According to reports, since the Charleston tide gauge was installed in 1899 on the peninsula, the sea level has increased by a foot, with predictions threatening a more significant increase by the end of the century.
The Army Corps and the City of #Charleston agree that plans for a multi-billion dollar seawall that will forever change the city's landscape need more public input. We wrote about it here: https://t.co/pCvYQWCNVS— SELC (Environmental Law) (@selc_org) April 30, 2020
In the ongoing study, research has revealed that multiple healthcare facilities are at substantial risk of significant damage and possible extended closure should a major storm or hurricane force high-levels of water into the city. Some of the possibly affected health facilities include the Medical University of South Carolina, Roper Hospital, and the Ralph H. Johnson VA Medical Center.
In addition, the Corps’ surveys reveal that over half of the historic structures on the Charleston peninsula are also at high risk of ruin from coastal storms.
As a response to the research findings, external scoping meetings and weekly Corp-organized team meetings that include city staff have been reported to take place. Team members involved in the Inter agency Coordination Team include U.S. Fish and Wildlife Service, the National Oceanic and Atmospheric Administration, SC Office of Coastal Zone Management, SC Historic Preservation Office, The National Park Service, The Historic Charleston Foundation and others.
Additionally, the city itself is also working to protect its residents, having launched Charleston’s second edition of its Flooding and Sea Level Rise Strategy and through its various recent an ongoing projects involving drainage improvements and rehabilitating the Low Battery seawall, among others.
In reaching this stage of the project’s development, the Corps initially proposed a 60-day comment period but, because of the COVID-19 health crisis, no engagement has been able to be made in person.
However, Southern Environmental Law Center (SELC) reports that since the announcement, Charleston Mayor John Tecklenburg issued a new timeline for the project’s consideration, increasing the opportunity for public input. Now, after the initial comment period has expired, the city will launch a six-month effort to more fully explain the project and to accept public input, which will be followed by an additional Corps 30-day comment period taking place sometime next year.
“Three hundred years ago, Charleston residents built a wall to keep out the sea,” said Chris DeScherer, Managing Attorney of SELC’s Charleston office. “Whether that is the best decision now is not as certain.”
Reports indicate that if built, the seawall would measure nine-miles-long and stand 12-feet-tall, consisting of two primary sections: an overland concrete barrier located along the eastern side of the peninsula from downtown to the Neck, and a metal barrier—called a combo wall—that would run through marsh and nearshore areas along the western side of the peninsula, in addition to a small portion on the eastern side.
When building the infrastructure, the Corps hopes it will be able to integrate the wall into existing structures and land features. The Corps also plans to install 40 water-tight gates along where the barrier crosses existing roads, railroad tracks, pedestrian paths, and other crossways. All of the gates would reportedly remain open most of the time, except in the event of an approaching coastal storm.
An additional 20 aquatic storm gates would also be placed along various storm water outfalls, tidal creeks, and marshes, but would remain closed during low tide while storms are approaching, so that the areas can continue to collect and store rainwater and other water sources.
Another aspect of the project calls for a stone breakwater structure, which would serve to protect against high waves in the Charleston Harbor. However, other measures involved in the project include installing several pump stations as to prevent water from being trapped within the walls, and the possible relocation or raising of certain structures. Already, approximately 100 structures have been identified as candidates for lifting.
If approved, the federal government and the city of Charleston plan to split the costs, with Charleston paying approximately $600 million.
Other Possible Seawall Projects
In July 2019, the Center for Climate Integrity—a project of the Institute for Governance and Sustainable Development—in partnership with engineering firm Resilient Analytics, released a study predicting that various U.S. coastal communities could be expected to pay $416 billion in seawall protection services over the next 20 years.
According to the CCI report, more than 50,000 miles of coastal barriers will be necessary in 22 states by 2040, resulting in over $1 billion in construction efforts in 132 counties and over $10 billion in 14 states. The top 10 state rankings are as follows:
Later that same year, the San Francisco International Airport announced that it would be constructing a $1.7 billion seawall around its facility.
According to the fiscal feasibility study, the project would include the construction of sheetpile walls at most of the reaches, new concrete walls at a number of channels and the removal of existing embankments would also be carried out. Wetland and Bay fill are also on the docket, though these require environmental permits.
In March, government-employed Dutch scientist and oceanographer Sjoerd Groeskamp proposed that two dams be built in the English Channel: one between France and England and the other between Scotland and Norway, enclosing the North Sea, in order to protect an estimated 25 million Europeans living in northern Europe from rising sea levels.
Combined, the two dams—referred to as Northern European Enclosure Dam (NEED)—are expected to measure 395 miles total, need roughly 51 billion tons of sand to build and would cost 250-500 billion euros ($274-549 billion).
And just last month, researchers from Princeton University reported to be looking at new designs for protective infrastructure to combat storm surges along the nation's coastlines.
Designed as oversized duel-purpose kinetic concrete umbrellas, the canopy-like structures serve as protection from sunlight by day, however, in the event of storm, can be transformed into a barrier to protect communities against heightened waves and incoming tides.
Through the research, the team found that the structures were able to remain stable when faced with a wall of water roughly 75% of their deployed height.