Davis & Floyd Project Spotlight: Charleston-US 17 Spring/Fishburne Drainage Improvements

Septima P. Clark Expressway (US 17) is a critical transportation corridor across the Charleston peninsula that experiences chronic flooding during heavy rainfall events. The City of Charleston enlisted Davis & Floyd to recommend and design improvements for flood resiliency, highway accessibility, traffic efficiency, and vehicular/pedestrian safety.

Davis & Floyd provided the following solutions to the challenge at hand:

• D|F identified the most efficient means for flood hazard mitigation through collecting, conveying, and discharging stormwater runoff to alleviate frequent and damaging flooding within study area.

• D|F provided an improved drainage system reliable for all tidal runoff will be generated for particular design events and where existing drainage networks and basin topography will direct this flow.

• D|F performed a hydraulic study to determine collection, conveyance, and outfall capacity requirements for the layout, sizing, and operations needed to provide service to the tidally influenced drainage basin.

Innovative Methods

Davis & Floyd modeled and developed vortex structures for controlling air entrapment atop vertical drop shafts carrying flow from conventional collection systems into the deep conveyance tunnel network. Our team used a 12’-diameter conveyance tunnel network to connect drop shafts throughout the drainage basin to a pump-assisted outfall to the Ashley River. We designed a diesel-powered, 360,000 gallon-per-minute pump station housed within an aesthetically-pleasing building that fits the character of the neighborhood and houses mechanical screens, silt removal pumps, water treatment unit, electronic controls, and emergency generator power.