US Army Corps of Engineers
Charleston District Website

Charleston Peninsula Coastal Flood Risk Management Study

Study Background

The Charleston Peninsula Coastal Flood Risk Management Study is a federal feasibility study that investigates coastal storm impacts on the Charleston peninsula. In partnership with the City of Charleston and its stakeholders, the study also explores economically-viable and environmentally-sound solutions to mitigate coastal storm risks. The feasibility study began in 2018 and is 100 percent federally funded through Emergency Supplemental Funding.

This feasibility study is one piece of the City’s overall comprehensive flooding strategy. In the last several years, the City has initiated several flood reduction strategies, including its Flooding and Sea Level Rise Strategy, a vulnerability assessment, rehabilitation of Low Battery Wall, Dutch Dialogues and major drainage projects. This study primarily addresses the risks of coastal storm surges. In conjunction with other flood mitigation efforts, the study also takes tidal flooding and sea level rise into account in its analysis.

In April 2020, the U.S. Army Corps of Engineers published a draft report outlining study findings and general storm risk reduction measures, including a perimeter storm surge wall with pump stations and nonstructural measures. Over the last several months, the study has used public and agency feedback, as well as results from ongoing modeling and analysis, to continue optimizing the proposed plan. Among some of the plan refinements include removal of the wave attenuator, reducing the project’s initial cost; increasing the sea level rise curve to evaluate more severe SLR scenarios; ongoing modifications to the storm surge wall alignment to reduce costs without impacting benefits; and additional detailed interior hydrological modeling.

Transition to an Environmental Impact Statement 

In March 2021, the study transitioned from an Environmental Assessment (EA) to an Environmental Impact Statement (EIS). View the EIS Notice of Intent here. Conducting an EIS allows USACE to do a more robust analysis on project impacts and more clearly define measures to mitigate for those impacts. It also allows for expanded public engagement on the proposed plan through public meetings and release of a revised and updated draft report for public review.

Learn more:

  • Public EIS Scoping Meeting (March 30, 2021):  The study held a public scoping meeting March 30. View the event below and the Public EIS Scoping Meeting presentation.
  • Charleston City Council Peninsula Workshop (Feb. 18, 2021):  USACE provided an update on the study to City of Charleston City Council members in a public workshop Feb. 18, 2021. View the full meeting here.
  • Interactive Presentation:  The study team created an interactive site to help visually describe the selected plan, alternatives, history of peninsula flooring and more.
  • Draft IFR/EA of April 2020:  Draft Integrated Feasibility Report/Environmental Assessment documents from April 2020 are below.

Frequently Asked Questions

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The National Environmental Policy Act (NEPA) requires federal agencies to assess the environmental effects of their proposed actions prior to making decisions. Where a major federal action will result in a significant effect on the quality of the human environment, federal agencies are required to prepare a detailed statement (EIS) assessing the environmental impact of the proposed action and its alternatives prior to a decision to implement the action. If the potential impacts are unknown, federal agencies initiate an EA to evaluate whether a proposed action will have environmental impacts. If impacts are determined to be significant, and the ability to mitigate adverse effects to a less than significant level is uncertain, then NEPA requires preparation of an EIS.

After the Draft Feasibility Report and EA (FR/EA) was released for public and agency review, USACE continued to optimize and refine the proposed plan. Upon further agency analysis of the refined plan, as well as consideration of public input in response to the Draft FR/EA, USACE has determined that some of the potential adverse impacts are significant and may not be reduced below a level of significance through project modification alone, and that this uncertainty merited an EIS.

Conducting an EIS will allow USACE to perform an expanded analysis, where necessary, on project impacts and more clearly define measures to mitigate those impacts. The EIS will include the same categories of impact analyzed in the EA, including the effects on historical and cultural resources, visual resources, natural resources, and community resources. In addition, the EIS will allow for expanded public engagement on the proposed plan through additional public meetings and release of the revised report for public review.

The public will have several opportunities to provide input during the EIS process.

  1. EIS Scoping Period and Public Meeting (March 2021): The public is encouraged to submit input during a 30-day input period which runs from March 23 — immediately after the EIS Notice of Intent is published in the Federal Register — to April 22, 2021. To facilitate and encourage comments, USACE and the City of Charleston hold a virtual public EIS scoping meeting March 30 from 5-7:30 p.m. For more the public meeting agenda and access instructions, visit how to access the public meeting. During this period, USACE requests public input on other potential alternatives for USACE to consider, other potential impacts of the proposed action to be analyzed, and existing information and analyses relevant to the proposed action. Feedback already provided on the Draft FR/EA will be considered for scoping and development of the Draft FR/EIS.
     
  2. Draft FR/EIS and Public Meeting (Summer/Fall 2021): USACE will hold a 45-day comment period following release of the Draft FR/EIS in Summer/Fall 2021. During this period, USACE will hold a public meeting to present the updated findings in the Draft FR/EIS and facilitate public review. Comments submitted during this period will be addressed in the final report.

For more information on commenting during the NEPA process, see the Council on Environmental Quality Citizens Guide to NEPA.

At this stage in the NEPA process, USACE and the City of Charleston request input on other potential alternatives for USACE to consider, other potential impacts of the proposed action to be analyzed, and assistance identifying existing information and analyses relevant to the proposed action. These comments will be used to build upon scoping conducted for and comments pertinent to scoping that were received on the Draft EA released in April 2020.

USACE and the City of Charleston hold a virtual public EIS scoping meeting March 30 from 5-7:30 p.m. For more the public meeting agenda and access instructions, visit how to access the public meeting. This meeting is part of a 30-day public input period which runs from March 23 — immediately after the EIS Notice of Intent is published in the Federal Register — to April 22, 2021. The purpose of this meeting is to collect scoping comments from the public to inform the EIS. These comments will be used to build upon scoping conducted for and comments pertinent to scoping that were received on the Draft EA released in April 2020. The meeting will also include a thorough update on the study’s progress and describe the overall NEPA process.

There are several ways the public can submit comments during the scoping period, which runs from March 23 to April 22.

  1. Using the online comment form.
  2. Emailing comments to Chs-Peninsula-Study@usace.army.mil.
  3. Mailing comments to:
    U.S. Army Corps of Engineers Charleston District
    ATTN: Planning and Environmental Branch
    69A Hagood Avenue, Charleston, SC 29403
  4. At the virtual public scoping meeting during the public comment section. To give all attendees an opportunity, input is limited to two minutes.

Comments are due April 22, 2021 — 30 days after publication of the EIS Notice of Intent in the Federal Register. Comments submitted last year on the draft report that are relevant to the scoping of potential alternatives and impacts will be considered for the EIS, and do not need to be resubmitted.

The EIS process gives USACE, the study sponsor and cooperating agencies additional time to assess and mitigate for adverse environmental impacts. As a result, the study’s completion date has been extended from Fall 2021 to Summer 2022.

The EIS process does not alter the study’s goals, expand the authorized focus on coastal storm surge, or change the City’s role in the study. The study’s original goals remain the same: reducing risks to human health, life and safety and reducing economic damages caused by coastal storm surge events through a cost-effective, environmentally-sound and feasible solution. The focus of the feasibility study on protecting the highly vulnerable Peninsula from coastal storm surge remains. Transitioning to an EIS will not change the City’s 35 percent cost-share requirement for construction of a project.

Alternatives, including the proposed action with alignment of the perimeter storm surge wall and localized non-structural measures, will continue to be examined and refined as additional input and analysis are reviewed. This continued analysis and input will inform more specific strategies for mitigating impacts to historical, visual, community and natural resources. Refinements to the proposed action and mitigation measures may lead to an adjustment in the initial proposed cost of construction. Additional impact analyses will be based on available data and modeling efforts that are already underway.

The Charleston Peninsula Coastal Flood Risk Management Study is a federal feasibility study that investigates coastal storm impacts on the Charleston peninsula. In partnership with the City of Charleston and its stakeholders, the study explores economically-viable and environmentally-sound solutions to mitigate coastal storm risks. Working in tandem with other flood mitigation efforts, the study primarily addresses the risks of coastal storm surges and considers tidal flooding and sea level rise in its analysis.

Coastal storms on the Charleston Peninsula place people at risk, including the potential for loss of life and declines in public health. The Charleston Peninsula experiences coastal storm surges that adversely affect the economic sustainability of Charleston, including impacts to businesses, organizations and industry; critical facilities and infrastructure; and residents. Coastal storm events also limit access to critical facilities, emergency services and evacuation routes. Historic and cultural resources are at risk of damage due to storm surge flooding.

Currently, the plan proposes a 12-foot NAVD88 perimeter storm surge wall with pump stations and nonstructural measures, such as flood-proofing and home-raising, for the study area. Design and alignment of the storm surge wall are conceptual and will continue to undergo refinement through progressive study phases, should the project move forward. The surge wall would be built to withstand earthquakes and can be elevated in the future.

The study has used public and agency feedback, as well as results from ongoing modeling and analysis, to continue optimizing the proposed plan. Among some of the plan refinements from 2020 include removal of the wave attenuator, reducing the project’s initial cost; increasing the sea level rise curve to evaluate more severe SLR scenarios; ongoing modifications to the storm surge wall alignment to reduce costs without impacting benefits; and additional detailed interior hydrological modeling.

The study is currently in the initial (feasibility) phase of the USACE project delivery process. The ultimate purpose of this 3x3x3 feasibility study is to determine whether or not there is a federal interest in a storm surge solution on the peninsula, and if so, outline a project recommendation.

If the project moves to the Pre-Construction Engineering and Design, or PED, the Corps will work with the City of Charleston and local stakeholders to closely refine project design details, including height, placement and material selection, and prepare renderings.

PED, also known as the Design Phase, is a collaborative effort. Within Federal parameters, the Corps will work with the City of Charleston and local stakeholders, such as Historic Charleston, Preservation Society and many others, on determining design features. The City may propose some additional features to aesthetics and the alignment that would be entirely funded by the City.

Regardless of the final design features of a perimeter storm surge wall, the perceived elevation of the wall will vary depending on the location’s topography (i.e., the above-ground wall height will vary according to whether an area is lower-lying or higher ground).

USACE feasibility studies do not guarantee construction. The USACE project delivery process has several steps before construction, including a finalized feasibility report; the City of Charleston must agree with the recommendation and be willing to accept the local cooperation requirements of a non-federal sponsor; the USACE Chief of Engineers must approve the final feasibility report and submit a Chief’s Report to Congress with a favorable recommendation of the project; Congress must make the decision whether to authorize the project; and, finally, Congress would need to appropriate and the City would have to provide the necessary funds to commence the design phase and later the construction phase of a cost-shared project.

The initial (feasibility) phase of the study is 100 percent federally funded. Future phases, including the Design and Construction phases, require a 35 percent cost-share from the City. This means, the City must fund 35 percent of the total cost of that phase. The cost-share amount is not required upfront and is broken up based on annual requirements over each fiscal year.

USACE will present analysis on potential effects to surrounding communities in Spring 2021. If the analysis determines that adverse impacts to adjacent communities are likely, USACE will assess the need for and appropriate mitigation to address those impacts. Formal USACE recommendations cannot move forward without considering the potential for adverse impacts to adjacent communities.

Natural and nature-based features (NNBF), or green solutions, can be effective for other sources of flooding (tidal, SLR), but alone are not sufficient for storm surge flooding. You can save, restore or enhance the wetlands, and they are very helpful for absorbing wave action and storing water when it gets here, but they will not stop the storm surge. Wetlands do not reduce the height of the surge (the water on top of the tide level). The same is true for living shorelines. While not suitable for coastal storm surge risk reduction, the study recommends a number of green infrastructure practices that the City of Charleston could implement to help with localized flooding.

The Dutch Dialogues Charleston Report provides a large-scale framework for addressing several sources of flooding across the region and contains multiple recommendations. The Corps proposal is one aspect of this framework and would, if implemented, require coordination with all other flood reduction efforts. To learn more about how the Corps proposal works with the Dutch recommendation, view the USACE-Dutch Integration.

No. USACE continues to refine the storm surge wall alignment. During optimization, USACE has evaluated ways to reduce costs without impacting benefits. The actual location of the storm surge wall is not finalized until the Design Phase.

The 12-foot NAVD88 storm surge wall is ultimately designed to mitigate storm surge damages to meet FEMA standards. Areas and structures outside the tentative storm surge wall alignment are on higher elevation or are designed within FEMA’s flood standards. For these areas and structures, the study recommends nonstructural measures, such as flood-proofing and home-raising.

Hurricane Hugo was a Category 4 hurricane when it made landfall just north of Charleston in 1989. In the Charleston harbor, peak storm tides reached 9.4-foot NAVD88, or 10-12 feet above mean sea level. Those tidal heights would not have overtopped a 12-foot NAVD88 storm surge wall.

Public EIS Scoping Meeting | March 30, 2021

USACE and the City of Charleston held a virtual public scoping meeting on the Charleston Peninsula Coastal Flood Risk Management Study on March 30 to encourage public input as the study transitions from an Environmental Assessment (EA) to Environmental Impact Statement (EIS). View the Public EIS Scoping Meeting presentation.

 

Public EIS Scoping Period: March 23-April 22

 

 

As part of the transition to an Environmental Impact Statement, the study holds a 30-day public input period from March 23 to April 22. Specifically, the study requests input on other potential alternatives for USACE to consider, other potential impacts of the proposed action to be analyzed, and assistance in identifying existing information and analyses relevant to the proposed action.

To facilitate and encourage comments, as well as to provide an update on the study's progress, USACE and the City of Charleston held a virtual public EIS scoping meeting March 30. View the full public meeting in the video module below and the Public EIS Scoping Meeting presentation.

Public Feedback



Three ways to provide feedback:

  1. Online: Use the online form by clicking the button above.
  2. Email: Email comments to Chs-Peninsula-Study@usace.army.mil.
  3. Mail: Mail comments to: 
    U.S. Army Corps of Engineers Charleston District
    Planning & Environmental Branch
    69A Hagood Ave, Charleston, SC 29403
  4. At the meeting: Provide verbal comments during the public meeting March 30, 2021 from 5-7:30 p.m.

Questions?

Have a question? Email the Charleston Peninsula Coastal Flood Risk Management Study at chs-peninsula-study@usace.army.mil

Interactive Study Overview