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The Town of Sullivan’s Island is taking significant steps to address its aging stormwater infrastructure through a new island-wide stormwater master plan developed by engineering firm SeamonWhiteside (SW+). The plan aims to ensure long-term resilience and efficient drainage in anticipation of increasingly intense weather events.
The existing drainage system was originally installed by the South Carolina Department of Transportation (SCDOT) decades ago, before Sullivan’s Island was incorporated as a town. As a result, much of the infrastructure is clogged, collapsing, or simply not designed to handle the volume of rainfall and high tides the island has experienced in recent years. SW+ has been tasked with developing a comprehensive improvement strategy to address these issues.
Outside of the ongoing South Carolina Infrastructure Investment Program (SCIIP) projects, the firm recommended 18 additional initiatives across three critical zones: Osceola Avenue, Station 22½, and Station 26½. These areas are not currently covered by existing projects or grant funding.
One of the most substantial efforts will occur on Osceola Avenue, estimated to cost $9.5 million. Engineers propose elevating the road between 12 and 18 inches in some of its lowest-lying areas to mitigate flooding. Alongside this, an improved drainage system will be installed, using pumps to overcome the limitations of gravity-based systems in low-lying zones.
Credit: Rob Byko
At Station 22, SW+ recommended entirely replacing the drainage infrastructure at an estimated cost of $3.7 million. This will include larger pipes and new inlets stretching from the causeway to Atlantic Avenue and down adjacent Middle Street and Ion Avenue. The project will also involve dredging the marsh near the causeway outfall site and installing a tidal check valve to prevent seawater backflow during high tides.
At Station 26, the plan suggests upsizing pipes and laterals to better manage stormwater runoff and prevent flooding, costing around $6.4 million.
Meanwhile, ongoing projects under SCIIP target other areas, including Stations 16, 25, 28, and 31. Bids for these projects are expected to be advertised in December 2024, with construction set to begin in March 2025 and conclude in May 2026, 15 months later.
Ryne Phillips, project manager with SW+, emphasized that the work will remain within roadways and public rights-of-way, avoiding impacts on private property. However, he noted that temporary disruptions, such as inaccessible driveways and tree removal, will be necessary. Plans include replacements for removed trees, and residents can expect a landscaping allowance in the construction bids.
Credit: Rob Byko
Phillips addressed the suggestion of coordinating with Dominion Energy to install underground power lines alongside the drainage construction. He advised against delaying the current project, stating, “At this point, I think we need to get the project to bid, get a contractor, and check more boxes with the federal funding agencies so we don’t jeopardize $9 million.” He added, “Once we get a contractor and we get to bid, we can work through some ideas during construction.”
Mayor Patrick O’Neil acknowledged the upcoming disruptions.
“2025 and a good bit of 2026 is going to be a messy year,” he said. “We just need to put a sign on the causeway that says ‘Entering construction zone’: it’s going to be muddy, messy, disruptive, and loud.”
With an estimated $20 million for potential improvements to Osceola Avenue, Station 22½, and Station 26½, alongside an additional $10 million in SCIIP funding for ongoing drainage projects, this initiative is a critical step in the island’s long-term strategy to safeguard homes, businesses, and natural resources from flooding.
