Tunnelling reaches completion on West Ashley sewer
25 May 2016USA - Following a six-month excavation, the TBM drilling a new 1.6-mile-long wastewater tunnel in Charleston, South Carolina, has made its breakthrough, Charleston Water announced May 19.
This is the fifth and final phase of the USD 196M Sewer Tunnel Replacement Project, which began in the 1990s and is one of the largest and most costly infrastructure projects in Charleston Water System's 99-year history.
The new West Ashley tunnel will replace an existing tunnel that's in poor condition and too small for today's peak wastewater flows.
This creates a bottleneck that occasionally causes sewer overflows in low-lying areas of West Ashley.
The construction contractor is Southland Renda, a joint venture between Southland Contracting and Oscar Renda Contracting, who launched the 8ft-diameter TBM in November 2015 from deep shaft at the Plum Island Wastewater Treatment Plant. From there, it drilled under the Wappoo Cut to another deep shaft off Albemarle Road. The tunnel is 125 feet deep.
The contractor will now install a pipe in the tunnel, build a pump station at the treatment plant, and connect the new tunnel to the existing sewer system off Albemarle Road. Construction is expected to be complete and the tunnel put into operation in late 2017.
The design team includes Charleston Water System staff, Black & Veatch, Hussey Gay Bell, and Hazen and Sawyer.
