Project Details

More than 60,000 vehicles per day use the portion of U.S. Highway 17 known as the Septima P. Clark Parkway, or simply the Crosstown. It is vital that this route remains an efficient lifeline for emergency response vehicles, commuters, and those evacuating the city in times of imminent hurricanes. But due to the Crosstown's construction, neighborhoods have been separated for more than four decades. The project will reconnect those neighborhoods through pedestrian enhancements while improving traffic flow and efficiency. Most importantly, the Crosstown will be made safer for both vehicles and pedestrians.

The full infrastructure reinvestment portion of the U.S.17 Septima Clark Parkway Transportation Infrastructure Reinvestment Project will improve drainage in an area that covers approximately 20% of the peninsula of Charleston (PDF). This first image shows the location of the project on the peninsula and gives a sense of the scale.

Construction Phases

The second image is much more detailed showing all 5 construction phases of the project (PDF). Phases 1 and 2, the surface collection and conveyance system and drops shafts, are shown as the thinner pink lines and smaller yellow dots, respectively. Phase 3, the tunnels and access shafts portion, is depicted as the light blue thick lines and larger green dots. The outfall, to be constructed as part of Phase 4, is shown as the thick orange line and the pump station, Phase 5, is the royal blue polygon.

When it rains, the stormwater that collects on the street will be conveyed by the surface collection and conveyance system (pink lines) to the drop shafts (yellow dots) and access shafts (green dots). It will then flow into the tunnels (light blue lines) and to the wetwell under the pump station (royal blue polygon). After the stormwater passes through some trash screens, if the tide is low and the rainfall light, it will flow by gravity through the outfall boxes (orange lines) into the Ashley river. If the rain is moderate to heavy and/or the tide is high, the pumps in the pump station will add the extra energy need to move the stormwater to the Ashley River via the outfall boxes.