The Federal Emergency Management Agency (FEMA) and South Carolina Emergency Management Division (SCEMD) have received  the Town of Sullivan’s Island’s COVID-19 application for Federal grant funding through the Hazard Mitigation Grant Program (HMGP).

 

As part of the application process and in accordance with Executive Order 11988 and 44 CFR §9.12, final public notice is hereby given for the Town of Sullivan’s Island proposed project which contains actions in or affecting the floodplain and/or wetlands. The project will conform to applicable state and local floodplain protection standards

Funding for the proposed project will be conditional upon compliance with all applicable federal, tribal, state, and local laws, regulations, floodplain standards, permit requirements and conditions.

Applicant: Town of Sullivan’s Island

Project Title: Sullivan’s Island Storm Water Outfalls Improvements

Location of Proposed Work:  The proposed work will at stormwater drainage outfalls at Station 18.5 Street and Station 25 Street.

Planning Factors and Considerations:

Several significant factors were considered as part of this project, including, but not limited to:

• Impacts to the natural environment including changes to the floodplain and base flood elevation as well as natural habitats and native animal species.
• Consistency with local goals and initiatives to reduce impacts from natural hazards.
• The economic impact to the community; and
• Legal constraints that could have impacted project execution.

Proposed Work and Purpose:

Intense rainfall, King Tides, and compromised drainage infrastructure have caused repeated nuisance flooding for residents and patrons of Sullivan’s Island (Town). Areas of particular interest are those serviced by drainage infrastructure along Station 18.5 Street and Station 25 Street. These areas collect runoff from adjacent properties and streets and discharge north to the marsh. Recently rising sea levels and increased rainfall intensity have caused the original design capacity of these systems to be surpassed.

The purpose of the stormwater outfall improvements project is to upgrade drainage systems, as necessary, along Station 18.5 Street and Station 25 Street to provide adequate capacity during storm events. Upgrades and point repairs to these systems will provide relief during low tides; however, upgrades are also required to prevent backfilling of the system and flooding due to King Tides. As a result, tide check valves are also proposed at the outfalls of each drainage system which will runoff to leave the island but also prevent King Tides from entering the island.

The following describes the work to be performed to complete this project:

Task 1 – Project Kick-Off

The project will initiate with a project kick-off meeting held in the Town. This meeting will allow the Town to provide an overview of current flooding and system concerns, provide documentation of drainage infrastructure and flooding history, identify project stakeholders, and define project roles and expectations. During the kick-off phase, the Town will work with the South Carolina Emergency Management Division (SCEMD) to establish appropriate administrative requirements for the projects.

Task 2 – Engineering and Design

The Town will begin engineering and design by procuring a responsible engineering firm to complete survey, engineering, and design, and permitting services.

Task 2.1 – Data Gathering, Field Investigations, and Survey

A desktop-level analysis will be performed to gather pertinent data and background information to assist in the development of the drainage study. Survey-grade data will be collected to support engineering design and will include an inventory of significant and apparent hydraulic features.

Task 2.2 –Hydrologic and Hydraulic Modeling

Hydrologic and hydraulic models of existing and proposed conditions will be developed to evaluate existing drainage performance and support system design.

Task 2.3 – Engineering Design and Construction Document Preparation

Engineering plans, specifications, and construction documents will be prepared. Plans will be prepared and delivered to the Town for review at the 30% and 90% levels. Final plans and an opinion of construction cost associated with the final plans will be delivered to the Town. Technical specifications and construction documents will be prepared based on the final plan set as approved by the Town.

Task 3 - Permitting

Applicable permits will be prepared and submitted as required by local, state, and federal agencies. Applicable permits may include SCDOT encroachment permits, MS4/SCDHEC permits, OCRM permits, and USACE permits.

Task 4 – Construction

Following, Task 2 and Task 3, the Town will publicly bid the construction of the project, select the most responsible bidder, and enter into a contract with the said contractor. Construction will commence the following award of the construction contract.

Construction crews will start by installing appropriate sediment and erosion control practices, tree protection, and signage (e.g., detours). Next, the contractor will remove, repair, and replace drainage piping leading to the outfall. Outfall ditches from the stormwater piping to the marsh will be excavated and restored. Lastly, tide check valves will be installed on outfall pipes. Following drainage improvement construction, the contractor will be required to restore pavement, road shoulders, and other property that may have become damaged during construction.

Routine site visits/inspections will be completed to ensure construction is completed in accordance with the plans and specifications. A final site walk will be completed to develop a punch list and formally close out the construction phase. Following completion of the punch list, the contractor can demobilize, and the Town can begin the project closeout phase.

Task 5 – Project Close-Out

The Town will coordinate with SCEMD to submit all necessary paperwork (e.g., invoices, timesheets, etc.) to formally close out the project.

Drainage problems to be solved – The repairs and improvements will allow stormwater to move more freely off the Island and into the marsh as well as prevent saltwater from backflowing into the collection system during nuisance flooding and spring tides which ultimately reduces flooding events on private property and loss by residents

There are no other projects currently underway in the project area. At this time, there is no current or future development planned in the project area. The Town has adopted the latest version of the International Building Code and has incorporated these Code requirements in their attached Action Report in its Hazard Mitigation Plan.  This is a high priority for the Town and ensures its Building Codes requirements are met to provide building/structural resiliency in areas prone to flooding.

The project is located in FEMA Flood Zone AE, which covers nearly the entire Town of Sullivan’s Island.  This project must be located in the floodplains and wetlands because both stormwater outfalls requiring improvements are located in the floodplains and wetlands, and there are not viable locations outside of the floodplains and wetlands to make the necessary stormwater improvements. This project will have no adverse impacts to the floodplains or to the wetlands. Additionally, this project will not result in adverse impacts to any adjacent properties. No mitigation is required for this project.

Project Alternatives:

Viable alternates for this project were extremely limited. A limited alternative to removing existing failed stormwater infrastructure and replace with open channels/ditches was considered. With this alternate, the existing outfall could be completely blocked to prevent the tide from entering the island. This approach would prevent King Tide flooding and would provide increased storage for runoff. However, there would be no outlet for the runoff. As a result, any runoff that could not infiltrate due to high and/or saturated groundwater levels would simply inundate surrounding properties and roads causing additional flooding. This alternative is feasible but would not provide an acceptable level of protection against rainfall flooding. The Engineer evaluated three alternative design year storm events for this project.  That alternative evaluation resulted in the 25-year design being the most feasible and cost-effective for eliminating the flooding in this project area. Implementing this 25-year design will pose no adverse impacts on Environmental Justice Issues, Historic Issues, Endangered Species, or Hazardous Materials.  All Wetlands, Hydrology (Upstream and Downstream Impacts), Floodplain/Floodway requirements were factored into the project design and permitting requirements for all alternative elevations considered

The impacts of taking No Action will result in reoccurring tidal flooding in the project area. The No Action alternative would cost nothing but would allow for continued tidal flooding of roads and residential structures numerous times each year, with increasing occasions as sea levels continue to rise. To take No Action would continue to put the health, safety, and lives of the residents at risk.

Comment Period:

The comment period is from March 23, 2022, through April 8, 2022. Comments are solicited from the public; local, state, or federal agencies; and other interested parties in order to consider and evaluate the impacts of the proposed project. The comments can be made in writing and addressed to Andy Benke, 2056 Middle Street, Sullivan’s Island, SC 29482 or by email to  abenke@sullivansisland.sc.gov.net.  Comments are due by close of business on April 8, 2022.

Maps:

A map of the project areas is available to view by clicking here, and is also available for public inspection at 2056 Middle Street, Sullivan’s Island, SC 29482

Point(s) of Contact:

For additional information, please contact: Andy Benke, Town Administrator at abenke@sullivansisland.sc.gov.net. or (843) 883-5726.