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 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.
Download West Ashley Sewer Tunnel Fact Sheet (PDF)
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Click image to view larger version (PDF: 1.5 MB).
For more information, contact Charleston Water System's Enginnering and Construction Department at info@charlestoncpw.com or (843) 727-6856. |
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