Charleston, South Carolina, has completed an approximately $198 million stormwater infrastructure project designed to reduce flooding across a large portion of the downtown peninsula.

The U.S. 17 Spring/Fishburne Drainage Improvement Project includes the William Dudley Gregorie Pump Station, which can pump up to 360,000 gallons of stormwater per minute into the Ashley River. The station serves a drainage area of nearly 550 acres, covering approximately one-fifth of the Charleston peninsula.

Much of the project’s infrastructure is underground, including approximately 1.5 miles of tunnels measuring 12 feet and 8 feet in diameter and 18,000 linear feet of new pipes and drainage structures. Improvements are intended to reduce flooding along the Septima P. Clark Parkway, also known as the Crosstown, and provide additional drainage capacity for portions of the city's medical district.

Developed over more than two decades, the project was designed to keep the U.S. 17 corridor dry during a 10-year storm and allow the system to drain water during high tides, including king tides. The pump station also incorporates considerations for future sea level rise.

City officials said the project will not eliminate flooding but is expected to reduce the depth and duration of inundation by moving water off streets more quickly. Additional improvements include landscaping and pedestrian safety upgrades, including a new connection across the Crosstown.

The project is part of Charleston’s broader stormwater management strategy, which city leaders say will require coordinated improvements across multiple drainage basins.