Charleston Water System is in the process of replacing the network of deep tunnels that carry sewage to our Plum Island Treatment Plant.

With an estimated total cost of $224.5 million, it is the single most costly project in Charleston Water System’s history, funded primarily by revenue bonds and sewer rate increases.

The original tunnel system was built in the late 1960s to collect wastewater from shallow sewer lines and deliver it to the treatment plant. Over time, the highly corrosive nature of wastewater damaged the carrier pipe inside the tunnel and the tunnel structure itself.

After discovering this severe deterioration in 1998, Charleston Water System began an aggressive, multi-phased effort to replace the tunnels. Engineers feared that a collapse might block the tunnel and cause sewer overflows—a potentially serious threat to public health and water quality in the Charleston Harbor, not to mention the overall economic impact to the Charleston metro area.

As of January 2010, three sections of the tunnel have been replaced and a fourth section added. Engineers are now working on the design for the fifth phase, the West Ashley Tunnel, which involves replacing the existing section of tunnel that serves West Ashley, parts of Johns Island, Hollywood, and Ravenel.

The existing West Ashley Tunnel is structurally unsound and does not have enough capacity, which leads to sanitary sewer overflows in the Byrnes Down and South Windermere areas during heavy rain events. Learn more about the West Ashley Tunnel Project

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For more information, contact Charleston Water System's Engineering and Construction Department at info@charlestoncpw.com or (843) 727-6856.

West Ashley Sewer Tunnel Replacement Project

Information for neighborhood groups and property owners near planned construction sites

(February 1, 2012)—Charleston Water System is continuing the process of contacting neighborhood groups and property owners near the construction sites for the West Ashley Sewer Tunnel Replacement Project.

The project has been delayed and remains in the final design/planning stages. However, we anticipate that construction may begin in Fall 2012. Details about the construction timeline will be posted here as that information becomes available.

For more information, download the West Ashley Tunnel Fact Sheet (PDF), or contact Jenny Craft, Public Relations Manager.

Information for contractors and vendors

(February 1, 2012)—Charleston Water System continues to work on finalizing the design of the West Ashley Sewer Tunnel Replacement Project. 

Details regarding the project schedule (i.e. availability of bid documents, mandatory pre-bid meeting, and bid opening) will be forthcoming as soon as a resolution on a pending permit issue is reached. 

Notification of contractor prequalification decisions remains suspended due to the pending permit issue, as final resolution of the permit may affect the work. Please check this website periodically for updates on the project status and further details regarding contractor prequalification.