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What is the sewer tunnel?
Why does it need to be replaced?
Will the new tunnel help alleviate flooding in downtown Charleston?
How is the new tunnel being built?
How were the tunnel construction sites selected?
When did construction begin and how long will it last?
Who should I contact for more information, or to report a complaint?
What is the sewer tunnel?
The tunnel system, orgininally built in the late1960s to transport sewage to the Plum Island treatment plant, is now being replaced because years of corrosion have damaged the tunnel structure.
The eight-mile tunnel system roughly follows the perimeter of the Charleston Peninsula and stretches under the harbor to the treatment plant. A separate section of the tunnel conveys wastewater to the plant from the West Ashley area.
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Why does it need to be replaced?
The tunnel was built in the late 1960s and is now deteriorating. Divers have discovered collapsed sections of the tunnel structure and large holes in the pipe that carries the wastewater.
If the tunnel is not replaced, debris build-up could eventually block the flow of wastewater and cause sewer system overflows.
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Will the new tunnel help alleviate flooding in downtown Charleston?
No, the new tunnel will carry sanitary sewerage only–-not storm water. The storm water drainage system is separate from Charleston Water's sanitary sewer system. The City of Charleston Department of Public Service owns and operates the storm water system.
Although Charleston Water System acts as a billing agent for the storm water service fee, all proceeds go to the City of Charleston.
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How is the new tunnel being built?
The new tunnel is being built in five phases. The first phase was completed in 2001 and the second in 2006. The third phase is expected to be complete in late 2007, the fourth in 2008.
Most of the work is taking place more than 100 feet underground; above-ground construction is being performed in and around shafts, which are essentially large holes in the ground that will provide access for equipment to bore the tunnel cavity.
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How were the tunnel construction sites selected?
Engineers spent months finalizing the underground route for the new Ashley and Cooper Tunnels and selecting suitable construction sites.
The design team faced numerous challenges in selecting these shaft sites. Besides the lack of construction space on the Peninsula, the sites had to be close enough to the existing tunnel so pipes can be installed to divert wastewater to the new tunnel once it is complete.
Environmental, geographical, and historic preservation concerns also dictated the selection of these sites. Our design team studied many alternatives and consulted city staff in order to meet these criteria and to minimize the impact on surrounding neighborhoods and businesses.
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When did construction begin and how long will it last?
Construction on the Ashley Tunnel (Phase II), began in March 2004 and was completed in August 2006.
The phase III Cooper Tunnel construction began in June 2005 and is scheduled to be complete by the end of 2007.
Construction on the new tunnel to Daniel Island will take about two years to complete; work began in May 2006.
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Who should I contact for more information, or to report a complaint?
For public information requests, please contact Jenny Hagan, Public Relations Manager at (843) 727-6856. To report a complaint, please contact Larry Drolet, Construction Manager at (843) 727-6856.
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