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US Army Corps of Engineers Charleston Peninsula Sea Wall
The Army Corps of Engineers has proposed protecting the city of Charleston from flooding caused by storm surge by encircling the city's historic peninsula with an eight-mile seawall and building a 4,000-foot wave attenuating structure in Charleston harbor.
On June 19, 2020, the Coastal Conservation League and the Southern Environmental Law Center, along with Charleston Waterkeeper, the South Carolina Wildlife Federation, Audubon South Carolina, and the South Carolina Environmental Law Project submitted comments to the Army Corps on its seawall proposal. (See our full comment letter at the bottom of this page.) In our comments, we pointed out some significant flaws and concerns, including:
The lack of a robust environmental review. The Corps inexplicably concluded that the seawall will not have a "significant" impact on the human environment, and therefore doesn't need an Environmental Impact Statement (EIS) that would require the Corps to rigorously explore and objectively evaluate reasonable alternatives. In fact, because the current proposal would end up destroying or impairing national historic landmarks, significant wetlands, essential fish habitat, and more, the Corps is legally required to prepare a full EIS to thoroughly examine and describe its plans to avoid and minimize harm to these precious resources.
A reliance on "grey infrastructure." The proposal focuses only on human-engineered solutions like concrete seawalls, ignoring nature-based solutions or green infrastructure that could deliver multiple benefits, including buffering from storms and added flood storage capacity. Instead of building a single-purpose, uniform wall, the Corps should carefully evaluate solutions that create multiple benefits and are tailored to the unique needs of different areas of the peninsula.
Incomplete or inaccurate data and assumptions. The proposal ignores important sources of flooding on the peninsula which are also tied to strengthening coastal storms, such as more intense rainstorms, tidal flooding, and groundwater inundation. It also underestimates likely future sea level rise, creating the danger of building a costly seawall that can't even achieve its stated goal of protecting the peninsula from storm surge.
Uncertainty about unprotected areas. The Army Corps doesn't explain how communities outside the proposed seawall will be protected. The exclusion of a number of working class communities from the seawall perimeter shows that the Corps has not appropriately considered environmental justice issues. It also hasn't adequately evaluated the potential for damage from wave deflection to communities west of the Ashley River or east of the Cooper River, the risks of catastrophic failure or overtopping of the seawall, or the damage to wetlands.
High cost. The proposal is biased toward costly, environmentally damaging grey infrastructure when less expensive, nature-based solutions are available, and the projected cost is incomplete and probably underestimated.
The nearly $2 billion proposal from the Corps, of which the city would have to pay just over a third, is focused solely one problem: defending the peninsula from storm surge. While storm surge is a major concern, Charleston faces many other flood threats that interact with and exacerbate damages in coastal storms. With a price tag this massive, the Corps should take a more holistic approach to flooding and should find solutions that create greater benefits for the community.
A year ago, the citizens of Charleston chose a broader approach than just a wall, adopting the "Dutch Dialogues" as guiding principles for living with water. The proposed wall design is inconsistent with the Dutch Dialogue principles, but we remain hopeful that this process and the discussions that will continue between the Corps, Charleston's leaders, and, most importantly, the city's residents will result in an approach that addresses the proposal's shortcomings and results in effective solutions. The best way to ensure that outcome is to engage in a robust review that a proposal of this magnitude deserves.
With increasing frequency every year, the City of Charleston finds itself under water. We are on the front lines of a changing climate and sea level rise. Stronger and more frequent rain events, higher seas pushing water further inland with extreme high tides, dangerous storm surges from hurricanes, and groundwater inundation from a rising water table all contribute to one of the most urgent threats of our time: flooding.
Charleston is no stranger to catastrophic storms or flooding. Since its settlement by Europeans three-and-a-half centuries ago, man has tried to battle nature in an attempt to keep water from getting onto the land and flooding homes. Creeks and marshes have been filled, walls have been constructed, and massive tunnels and pump stations have been engineered to try and keep our city dry. And now, Charleston faces projects that amount to billions of dollars to try and keep up with this pace.
Corps of Engineers Proposes a Seawall around the Charleston Peninsula
In April 2020, the US Army Corps of Engineers released a draft feasibility report and environmental assessment to address coastal storm risk for the Charleston Peninsula. The initial comment period to provide feedback on the proposed project closed June 19th, 2020. A second comment period is slated for late in the first quarter of 2021.
This study is the result of the federal planning process referred to as the 3x3x3 process consisting of a study that costs $3 million to complete within three years and includes three concurrent levels of review. In Charleston, the Army Corps was tasked with identifying a buildable project to protect the peninsula from flooding caused specifically by storm surge.
Following 18 months of data collection, modeling, and analysis the Army Corps is proposing to construct a nearly eight-mile seawall around the perimeter of the peninsula approximately three feet higher than the current height of the High Battery seawall. The seawall would require at least five pump stations to be constructed to pump water outside the wall. In total, the project would impact nearly 111 acres of marsh.
Also included in the USACE recommendations is a 4,000-foot long breakwater located offshore by the Battery. In addition, nonstructural measures are being proposed to address nearly 100 houses located outside of the wall in the Rosemont and Bridgeview Village communities. The specific definition of nonstructural measures was not included in the report beyond potential options ranging from elevating, 'floodproofing', relocating, or buying-out homes.
In June, the Conservation League facilitated a webinar with our partners at Charleston WaterKeeper, Groundswell Charleston, Historic Charleston Foundation, Preservation Society of Charleston, and The Nature Conservancy to provide a platform for the public to hear from the Army Corps of Engineers and the City of Charleston about the 3x3x3 project. You can watch that recorded webinar by clicking here.
Proposed Project Raises Concerns and Needs More Study
This proposed project is estimated to cost nearly $2 billion and would be the most expensive single construction undertaking in Charleston's history, changing the city's landscape forever. However, as currently planned, the project would go forward without the public engagement and thorough vetting of an Environmental Impact Statement, which is required for every other major infrastructure project.
It is imperative for the public to remain vigilant and engaged by providing comments at every possible opportunity to prevent this project from moving forward without thorough review of community, cultural, and environmental implications.
These are just a few of the reasons the Conservation League is concerned about the proposed project:
The Corps utilized an outdated sea level rise scenario that falls short of projections the City of Charleston has chosen to use for planning future infrastructure. This results in the Corps underestimating sea level rise in 2070 by 1-2 feet, according to the City of Charleston's own guidelines informed by federal experts.
The Corps proposes to construct a concrete wall on land where possible and in the marsh where necessary. It would be built at an elevation of 12 feet requiring nearly two dozen flood gates at road, bike/pedestrian, and rail crossings, as well as at the five remaining tidal creeks on the peninsula to be closed whenever a major tide is expected. The Corps does not account for how the gates would operate after sea levels continue to rise when high tide will be above today's ground level, which would require the tide gates to remain permanently closed.
Attempting to seal out the sea in such a way could create a bowl effect, similar to the New Orleans problem, and places a significant part of the city below the water line and at risk of flooding if any of the significant machinery the wall relies on – like the gates and pumps – malfunctions.
Little detail has been provided as to why the Rosemont and Bridgeview Village communities, both in the city boundaries on the peninsula, were excluded from the seawall perimeter. These communities have been excluded from decisions on massive infrastructure cutting through their neighborhoods in the past and it is essential that they are engaged in creating their adaptation plan.
Certain damaging effects, such as how deflected wave energy may affect neighboring communities like West Ashley, James Island, and Mount Pleasant have yet to be considered in the study.
The mitigation for the wetland impacts this project would require is poorly outlined and does not offer the public an opportunity to comment on the merit of the plan.
Charleston faces so many unique challenges to address flooding. This proposed project offers just one very expensive and impactful solution to address one type of flooding in one area of the city, but the reality is our entire city needs to mitigate and prevent flooding by utilizing multiple solutions.
We Need More Comprehensive Alternatives
Charleston residents, community leaders, elected officials, and the Army Corps must work together collaboratively to identify the kind of projects that are worth $2 billion dollars. We just don't believe this is one as currently proposed.
Because a one-size-fits-all solution does not match the varied neighborhoods and fabric of the Charleston peninsula, the Army Corps should assess solutions on a neighborhood basis. This could help determine where a concrete wall is necessary and where nature-based solutions and other adaptation measures could serve a similar purpose. And where a perimeter defense system is truly the best option, such as along Lockwood Drive, the Army Corps should require that any hard structure serves multiple community benefits such as stormwater storage, a bike path, or park space.
Water is such an integral part of our Charleston identity. We cannot afford to lose sight of the sea. Only a year ago, Charleston chose to adopt the Dutch approach to living with water but unfortunately, this is not reflected in this narrowly focused and shortsighted study.
Wherever and whenever possible, the City of Charleston – and the greater Lowcountry – should be adapting to live with water by creating parks that can double as protective barriers against floodwaters, restoring former creeks, elevating structures, utilizing natural green infrastructure, re-naturalizing the floodplains, and determining where hard armoring may be necessary on a site-specific basis. This USACE peninsula study does not meet the standard it should in order to address the urgent threats the City of Charleston faces in the short and long term.
With your engagement, we can do better, and we will. Please continue to stay engaged by following the Conservation League as we keep you informed throughout this process.
2020-06-19 Charleston Seawall Comments_Final
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