Phase 3 Project Details (Tunneling)

Update December 17, 2018

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 July 2019. View a map showing alternate routes (PDF).


  • Shaft construction is almost complete and excavation of the President Street tunnel continues
  • Complete work at Lockwood St Shaft Site: January 2019
  • Substantial Completion: Spring 2020
  • Final Completion: Summer 2020

Project Overview

Phase 3 of the U.S.17 Spring/Fishburne Drainage Improvement Project will include the construction of deep tunnels and working shafts. There will be 4 working shafts constructed as part of this phase. Two of the shafts will be 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 will be 30-feet internal diameter. The tunnel connecting the Coming Street shaft and wet well shaft (under the Crosstown) will be approximately 5,400 linear feet (LF) in length and up to 12-feet in internal diameter. 

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


View videos of the mainline tunnel:

Note: Completion of the work at the Lockwood Street shaft site is significant as that will allow the commencement of Phase 4 of the project, construction of the wetwell and outfall.

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