Durban Harbour Entrance Widening (DHEW) – Tunnel Removal
The original Durban Harbour sub-aqueous tunnel, which was constructed in 1958, accommodated municipal services (mainly sewer pipes) between the Point and Bluff and was located beneath the harbour entrance channel. The entrance channel deepening and widening project necessitated the removal of the tunnel along with 2 approach jetties and terminal structures.
The tunnel was removed in two phases—the northern section was removed first in coordination with the dredging of Stage 1 of the new channel. The remaining section was then removed at the same time as the dredging for Stage 2 of the new channel.
The tunnel itself was a reinforced concrete immersed tube tunnel. The tunnel section was circular with an outside diameter of 4.88 meters and a wall thickness of 0.61 meters. While a number of options were considered to remove the tunnel, in the end, a frame was built and mounted on top of the tunnel. Diamond cutting wire powered by hydraulics was then used to cut the tunnel into sections. Holes were then cored into the sections at the 3 and 9 o’clock positions and grommet chain was used along with lift bags to lift each section to the surface. The section was then towed to Ashed where the floating crane was used to lift the sections out of the water.
This was a project of monumental proportions, large-scale operations, high-energy and stress levels and long duration. Our thanks to the many Subtech employees involved in this project – it has raised the level of Company’s status and forever changed the landscape that is Subtech.
Special congratulations to project manager Godfrey Sterley who along with Commercial Manager, Franz Scholtz, ensured that the project remained on track, the team in focus and the project a resounding success.