Phase 3 Project Details (Tunneling)

Update 29 January 2020

In order to construct the Coming Street access/retrieval shaft, the King Street ramp from I-26 eastbound will be closed for the duration of the project, estimated to be June 2020. View a map showing alternate routes (PDF).


  • Construction and lining of both tunnels is almost complete.
  • Work to line the complicated intersection has begun and may be complete by the end of February 2020
  • Substantial Completion: Late Spring 2020
  • Final Completion: Summer 2020

Project Phase Overview

Phase 3 of the U.S.17 Spring/Fishburne Drainage Improvement Project will include the construction of deep tunnels and working shafts. There are 4 working shafts constructed as part of this phase. Two of the shafts are 20-feet internal diameter (Coming Street/King Street off-ramp and President Street and Cannon Street). The wetwell shaft between the Ashley River Bridges and the Harmon Field working shaft are 30-feet internal diameter. The tunnel connecting the Coming Street shaft and wet well shaft (under the Crosstown) is approximately 5,400 linear feet (LF) in length and 12-feet in internal diameter. 

The tunnel connecting the Cannon St/President St and the Harmon Field shafts  is approximately 2,100 LF in length and  8-feet in internal diameter. These tunnels intersect approximately 140 feet below grade at the intersection of the Crosstown and President Street. There is also a smaller 500 LF 8-foot diameter tunnel connecting the Cherry Street drop shaft to the Crosstown tunnel.


View videos of the mainline tunnel:

The videos were taken during placement of the tunnel boring machine (TBM) in the Lockwood Drive working shaft and are courtesy of Upwind Studios of Mount Pleasant, SC.

Lockwood Drive Shaft

Lockwood Drive Shaft Orbit

TBM Insertion Timelapse