City of Florence Stormwater Master Plan

The stormwater system in any community consists of the natural and man-made drainage features and structures that transport rainfall throughout the community.  This consists of drainage features on individual properties – roof gutters, ditches in the yard, or culverts under the driveway; or larger features such as inlet boxes in parking lots, large underground pipes, ponds and even streams - Jeffries Creek, Pye Branch and Middle Swamp are all part of the City’s stormwater system! 

A stormwater master plan is a comprehensive assessment of the existing stormwater system and the development of a defined approach to address existing and future stormwater needs.  A stormwater master plan looks to address existing and future flooding concerns, while also trying to make the stormwater runoff (rainfall that is collected by the stormwater system) as clean and free of debris and pollutants as possible.  A master plan looks at how stormwater runoff is directed through the stormwater system, and how this system impacts the community and downstream lakes, rivers, and ultimately the Atlantic Ocean. A stormwater master plan evaluates causes of existing flooding and water quality concerns and identifies areas for improvements to meet the future needs of the community. It evaluates both man-made infrastructure and natural waterways under existing and future development conditions.

As the City of Florence has grown over time, the amount of stormwater runoff has increased as the amount of land development has reduced the amount of land area available for runoff to infiltrate into the ground.  Therefore, in many areas of Florence, pipes which were large enough to handle normal rain events are now too small to convey the increased stormwater runoff.  Additionally, as pipes get older, they are less effective at carrying stormwater volume.  Sediment that is contained in stormwater can lead to clogging of pipes and natural waterways, contributing to the stormwater system’s reduced effectiveness.  The City needs to evaluate the system in order to develop an effective approach for upgrading and repairing the existing system as well as adding new infrastructure to the stormwater system to accommodate growth.  This master plan development process will identify areas of need and determine a cost and schedule for stormwater system improvements.  This will allow the City to better plan and allocate funding to reduce flooding and improve water quality. 

Because of increased land development large storm events such as severe thunderstorms and hurricanes significantly stress the City’s stormwater system and cause widespread flooding as well as water quality concerns.  However, most flooding problems associated with the stormwater system occur during small, more frequent rain events. As you may have noticed over the last several years, these smaller events are occurring more frequently.  Flooding during these times is often related to a lack of sufficient infrastructure due to increased development or aging infrastructure that needs to be upgraded.  The master plan will focus on identifying areas impacted during these smaller storms and developing a solution to reduce the potential for frequent flooding in these areas.

Stormwater concerns can come in all shapes and sizes, including small ponding of water in the roadway, flooded yards, impassable streets, discoloured or foul-smelling stormwater runoff, or deposition of sediment after a storm event.  Fortunately, the City has a staff of highly trained professionals and engineering consultants that can address almost any stormwater concern you may have.  There are a variety of ways to get in contact with our team. We will be hosting four (4) public meetings to have an interactive dialogue with the community to identify and understand flooding and water quality concerns throughout the City. You may also reach out to Martin Fox, the City of Florence Engineer, at mfox@cityofflorence.com.

The project will occur in three phases:

• Phase 1 will be a review of historical data related to the development of the City’s stormwater system. The purpose of this task is to compare the original design and function of the system and how increased rainfall runoff and development has impacted the system. This phase is expected to take approximately four months.
• Phase 2 will include an inventory of the current system. The goal of this phase is to enhance the understanding of stormwater runoff within the City and to develop a plan to address both existing and future stormwater capacity and treatment concerns. The work in Phase 2 will occur concurrently with the work in Phase 1. This phase is expected to take approximately 14 months.
• Phase 3 of this study will be developing a comprehensive report that outlines concerns in the existing system and the identifies future remediation action through projects, upgrades and retrofitting of the existing systems to improve stormwater drainage as well as protect downstream natural resources. This report will be provided to the City to be utilized as a guide for future financial allocations to address stormwater concerns. This phase is expected to take approximately 6 months.   

In total, we expect the stormwater master plan to be completed in October 2024. Individual stormwater construction projects will continue while we work on the master plan.  

Field inspections will take place between 8 am to 5 pm Monday through Friday. If the City is required to perform an operation outside of these hours, an alert will be released via social media and the City’s website.

The City will prepare a map of the pipes, ditches, ponds, and inlets that will include the size and condition. City staff will have to validate some of the information found on the map.

While most of the work will be completed on public property, there are areas the City will need to access on private property. Input from the public will help refine locations that are experiencing flooding, drainage concerns or water quality issues. Your participation will help the City gain a better understanding of issues that are affecting individuals that make up the community. If you are experiencing any type of stormwater related concerns, please contact City officials or attend the public meetings.

The City will be providing financial support to the project as directed by City Council. This project is also being funded using federal grants from the U.S. Housing and Urban Development (HUD) Community Development Block Grant – Mitigation (CDBG-MIT) program. The South Carolina Office of Resilience will be providing oversight to the City for Grant related funding requirements.

Field investigations will be performed throughout the City. While we do not expect there to be major adjustments in traffic, the City will do its best to accommodate the high traffic areas at off-peak times to reduce traffic congestion.

As part of the stormwater master plan, the City will be assessing water quality issues within the City.  The master plan will address drainage, flooding and water quality concerns to create a holistic plan to maintain the waterways in Florence as high-quality natural community amenities.