Billion-dollar seawall around Charleston proposed to battle future hurricane storm surge

CHARLESTON, S.C. (WCIV) — Federal officials are proposing a billion-dollar seawall around the lower Charleston peninsula to battle back potentially catastrophic storm surge from inevitable hurricanes in the future.

The proposal was released Monday by the U.S. Army Corps of Engineers. Initial cost estimates place the funding needed conservatively at $1.75 billion, with certain variations that could drive costs as high as $2.2 billion, according to the USACE draft report.

The federal government and the City of Charleston would be splitting costs, the Army Corps says. Charleston would pay for approximately $600 million of the bill.

• REVIEW & GIVE FEEDBACK ON THE PROPOSAL | CLICK HERE

Should the project be approved by Congress and agreed to by the City of Charleston after public input and years of further study, Charleston again in the coming decades could be a walled city, as it was in the 18th century.

But instead of invading enemies, this proposed 9-mile, 12-feet-tall fortification would serve to keep out potentially catastrophic storm tide inundation.

An ongoing three-year study by the Army Corps finds critical healthcare facilities such as the Medical University of South Carolina, Roper Hospital, and the Ralph H. Johnson VA Medical Center are at substantial risk of significant damage and possible extended closure should a major hurricane force a wall of water into the city.

Additionally, Army Corps surveys predict more than half of the historic structures on the Charleston peninsula are at high risk of ruin from storm surge should a major storm strike along the Charleston coast.

Sea level rise is playing a part in the bleak projections from the Army Corps. Average sea level in the harbor is expected to rise at least six inches in the next 50 years, and possibly more than 2 feet. It's already risen more than a foot in the last century.

Higher status quo water levels would mean greater impacts from storm surge if a major hurricane were to make landfall in the immediate area of Charleston, as with Hurricane Hugo in 1989.

Army Corps project researchers say erecting the seawall would help to greatly mitigate potential storm surge damage in that event.

The seawall would consist of two primary sections: an overland concrete barrier erected primarily along the Battery and the eastern side of the peninsula from downtown to the Neck, and a metal barrier known as a combo wall traveling through the marsh and nearshore areas on the western side of the peninsula, and for a short stretch on the eastern side.

The wall would begin near the rear of the Charleston Sk8 skate park, which is adjacent to the Rutledge Avenue exit (MM 119) along Interstate 26.

From there, it would proceed along the western side of the peninsula past Waegner Terrace and Hampton Park, then along Lockwood Boulevard under the U.S. Hwy. 17 bridges down to the Coast Guard station.

The wall then would be integrated into the existing Low Battery structure, which currently is being raised to a height of 9 feet amid the City of Charleston's local efforts to battle increasingly frequent coastal flooding amid sea level rise.

Converting to a concrete structure along the Battery, the seawall would continue on the waterfront along Murray Boulevard to White Point Gardens, then adjacent to East Bay Street from south of Broad up past the Columbus Street port terminal.

Finally, the wall would run under the Ravenel Bridge overpass and shift inland along Morrison Drive, concluding somewhere behind the ILA Hall near the intersection of Morrison and Meeting Street.

The Army Corps says it hopes to integrate the wall into existing structures and land features where possible for both aesthetic and community footprint reasons. The Low Battery wall, for example, could be retrofitted rather seamlessly to meet the 12-foot height of the proposed seawall, according to the Army Corps of Engineers.

Because of the age and unknown construction history of the High Battery, however, the Army Corps says the existing wall there likely will not meet criteria to be part of the new wall construction. That would mean erecting a portion of the seawall in the marsh below the High Battery, according to USACE plans.

Roughly 40 water-tight gates would be installed where the barrier crosses existing roads, railroad tracks, pedestrian paths, etc. The gates will be open the majority of the time and would be closed only when coastal storms approach, the Army Corps says.

Additionally, another 20 aquatic storm gates would be placed along waterways such as storm water outfalls, tidal creeks, and marshes.

All these gates would be closed at the low tide as hurricanes or tropical storms draw near, leaving marsh areas inside empty and available to store water from rainfall and other sources.

Another aspect of the plan calls for a stone breakwater structure in the Charleston Harbor parallel to shore along the Battery on both sides of Oyster Point. It would serve to diminish the effects of high waves experienced during past storms.

The Army Corps plan also calls for other measures, including relocating certain structures, raising them higher off the ground, or taking steps to thoroughly flood-proof them.

Approximately 100 structures have been identified so far that are candidates for lifting should other alternatives be exhausted, the Army Corps says. Raising those structures would cost around $6.725, agency officials said.

The initial proposed path and height of the wall are subject to change pending further study, public input, optimization and other developments, the Army Corps says. The plan will be refined in the coming years.

There are immediate concerns about the project's negative impacts to the community, the Army Corps admits. Chief among them would the use of eminent domain.

So far, the Army Corps says it hasn’t identified the need for eminent domain as part of its plan, let alone buyouts of property owners, which would be the first course of action should the need arise to traverse personal property.

Buyout offers would be negotiated according to fair market value as determined by real estate appraisals, the Army Corps says. If negotiation fails, eminent domain could be utilized, but the Army Corps says it hopes to avoid that if at all possible.

Another issue of concern is a so-called bathtub effect, in which the wall would prevent water that comes in the form of rainfall from draining out. This could be a particular problem during normal rainfall events, exacerbating Charleston's already prevalent street flooding problems.

The Army Corps' proposal addresses that by planning for the installation of several pump stations to disperse rainwater accumulation. This would prevent the "bathtub" effect, the agency says.

You can CLICK HERE to read the Army Corps' full proposal, or pick up hard copies at the USACE Charleston office.

Public input is being sought, and due to COVID-19, the public comment period has been extended from the normal 30 days to 60 days, the agency says.

Additionally, virtual office hours have been set aside throughout May to answer anyone's questions.

Charleston Mayor John Tecklenburg said Monday the city will sponsor a larger public engagement process throughout the upcoming year once the federal public comment period has ended.

“I encourage all of our citizens to review this plan carefully and offer comments," Tecklenburg said. "The next 60 days of public input will be vital to refining the plan, and helping to ensure that it meets the high standards set by our recent Dutch Dialogues Charleston project.”

The Coastal Conservation League, however, feels 60 days simply isn't long enough, given the current state of affairs brought on by the COVID-19 pandemic, along with the shear scope and magnitude of the project.

The conservation group says the comment period should be extended to 120 days.:

“For a project of this magnitude, a comment period of 60 days would be a short period during ideal times. These aren’t ideal times," CCL Executive Director Laura Cantral said. "The public will spend much of the next 60 days figuring out how to stay healthy and get back to work safely. This study took 18 months to complete, while construction could take decades, and cost hundreds of millions of dollars. And the result itself will alter Charleston forever. There is no reason to rush this process, especially during the health crisis we’re facing.”