Septima P. Clark Parkway Menu
Septima P. Clark Parkway Menu
The Septima P. Clark Parkway extends from Spring Street and Cannon Street east of the Ashley River to I-26 east of Coming Street. US 17/Septima P. Clark Parkway was built in the 1960s and was initially named the "Crosstown Expressway." The "Crosstown Expressway" bisected historic African American neighborhoods and cut long-standing community connections. The six-lane divided roadway carries approximately 64,000 vehicles a day. It is a key evacuation route for the peninsula but can be flooded by a combination of heavy rainfall and high tide.
The study team has looked at alternatives that would improve traffic flow, address flooding, and would re-connect the community surrounding the parkway.
The project team considered three strategies to relieve congestion on US 17:
widening existing Septima P. Clark Parkway,
rebuilding US 17 as a tunnel, or
rebuilding US 17 as an elevated bridge
The study team recognized that widening the Septima P. Clark Parkway in its current location would have major negative impacts on the surrounding community. Therefore, this option was dismissed.
On this page, we are asking you to tell us which proposal for adding new capacity to the Septima P. Clark Parkway you would support.
Tunnel Option
Converting US 17 to an underground tunnel would be an opportunity to reconnect neighborhoods that were divided in the 1960s. This option will allow reconnection of neighborhoods and cut-off cross-streets. The underground tunnel would also allow for a large park and/or a future bus rapid transit line where US 17 is now. However, it will be expensive and complex to construct and would require large ongoing maintenance costs. Based on the traffic analysis, moving US 17 underground would require three lanes of through traffic in each direction. The conceptual route for the proposed tunnel is shown on the aerial photograph below. Also, the tunnel would have an upper and lower level with northbound and southbound traffic on different levels. The US 17 design would need to meet SCDOT design criteria, so it could not follow the existing roadway exactly.
The tunnel option is technically challenging. The tunnel must avoid the 2006 "Ashley Tunnel" sewer system owned by the Charleston Water System. The tunnel must avoid the US 17 Septima P. Clark Parkway Transportation Infrastructure Reinvestment Project. The 40 foot-wide right-of-way of the deep underground drainage tunnel generally follows the alignment of US 17. It is assumed that deep foundations will not be permitted near the deep tunnel right-of-way.
Simulation Video of the Tunnel Option (no sound)
Elevated Option
The second option to increase the capacity of the Septima P. Clark Parkway would include elevating the roadway from the Ashley River to I-26. This option would also provide an opportunity to reconnect the community with a large park and/or a future bus rapid transit line where US 17 currently exists. An elevated roadway could be easier to construct and less expensive than a tunnel. Based upon the traffic analyses, elevating US 17 would require three lanes of through traffic in each direction. The plan view of the elevated highway and its cross-section are shown on the aerial photograph below.
Simulation Video of the Bridge Option (no sound)
Summary of Environmental Effects
This table summarizes the potential environmental effects the options for adding capacity to the Septima P. Clark Parkway. In the analysis, the US 17 team considered twenty-nine potential environmental effects. The table summarizes the differences between the two options.
SEPTIMA P. CLARK PARKWAY | ||||
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| OPTION A |
| OPTION B |
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| Underground |
| Elevated |
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HUMAN ENVIRONMENTAL FACTORS |
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Relocations – residential units |
| 92 |
| 130 |
Relocations – non-residential properties |
| 16 |
| 25 |
Total number of relocations |
| 108 |
| 155 |
Land acquisition (in acres) |
| 17 |
| 25 |
Conversation area |
| 0 |
| 0 |
Schools |
| 1 |
| 1 |
Parks |
| 3 |
| 3 |
Greenways |
| 2 |
| 1 |
Community Facilities |
| 6 |
| 5 |
Neighborhood Cohesion |
| The tunnel option may improve community cohesion by reconnecting neighborhoods. |
| Residents may see land beneath the bridge as unusable. |
Environmental Justice |
| There may be temporary construction-related Environmental Justice impacts. |
| The Bridge Option may have long term Environmental Justice impacts. |
Historic Architectural Resources |
| 4 |
| 4 |
Archeological Resources |
| 1 |
| 1 |
Compatibility with zoning and land use plan |
| Yes |
| No |
Traffic noise |
| Traffic noise has not been analyzed |
| Traffic noise has not been analyzed |
Visual / Aesthetic |
| The aesthetics of a tunnel will be a change |
| The aesthetics of a bridge will be a change |
Recognized Environmental Conditions (RECs) |
| 5 |
| 5 |
Utility Conflicts |
| The tunnel must avoid the Charleston Deep Drainage Tunnel |
| Unknown |
Permits needed |
| Yes |
| Yes |
Construction cost – opinion of probable cost |
| $500,000,000 |
| $275,000,000 |
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NATURAL ENVIRONMENTAL FACTORS |
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Threatened Endangered Species |
| No Effect |
| No Effect |
Essential Fish Habitat |
| No Effect |
| No Effect |
Section 404 Waters of the US – wetlands |
| No Effect |
| No Effect |
Section 404 Waters of the US – streams |
| No Effect |
| No Effect |
Land and Water Conservation Fund sites (section 6f) |
| No Effect |
| No Effect |
US Navigable Waters – rivers and open water |
| No Effect |
| No Effect |
US Navigable Waters – critical area wetlands |
| 2 Acres |
| 0 Acres |
Prime Farmland |
| 0 |
| 0 |