Charleston Water System (CWS) is marking a second major checkpoint after a year of digging in its ongoing $135 million project to extend the West Ashley sewer tunnel.
Officials celebrated the milestone by taking media, project partners and others on a short journey that was 130-foot underground into the tunnel that still smells like freshly dug earth. In about two years, it will start moving millions of gallons of raw sewage to treatment.
On Tuesday, crane operators lifted a cramped cage holding four people at a time and lowered them into a wide-bore hole where the tunnel boring machine broke through last week.
The massive drill, dubbed “Miss Harper,” completed its 20,000-foot journey from Albemarle Road to Culver Avenue under the West Ashley Greenway three weeks ahead of schedule and under budget, according to CWS officials.
This machine has been boring away for almost a whole year, working 20 hours a day,” said CWS Communications Director Mike Saia. “Now, it’s finally broken through and is ready to be removed.”
Miss Harper will be hoisted out of a wide-bore shaft by crane. From there, it will be reassembled, shipped elsewhere to continue work. No specifics have been announced.
“This tunnel will easily go 100 years,” said Kathleen Wilson, vice chair of the CWS board of commissioners. “We’ll use that as a benchmark. But I would venture to say it’s 150 years or so of service.
A huge relief
The project comes at a time when West Ashley residents are complaining more and more about sewer overflows in their neighborhoods. It’s one of the most persistent infrastructure problems in the area, particularly during storms. But CWS officials say the new tunnel will eliminate many of those problems.
Construction is expected to be completed in late 2027, and the tunnel is expected to be fully operational in about two years. It is expected to take on nearly 60 million gallons of raw sewage per day, delivering it to the wastewater treatment plant on Plum Island. The extended sewer tunnel will serve West Ashley, Johns Island, Hollywood and Ravenel.
“It’s a critically important project to Plum Island because it will eliminate a lot of problems that we’ve had in the past with sanitary sewer overflows,” Wilson said. “By bringing the flow to one point, we’re replacing a problematic pump station in West Ashley. … “It’s an environmentally friendly project that’s going to help us tremendously.”
The $135 million extension project is the second-most expensive project in CWS history, but the utility says the relief that the community will feel immediately upon completion — and the environmental benefits — makes it worth the cost.
“Right now, the community around this project and throughout West Ashley should be very happy to see this big step in the process,” Saia said. “They’re not going to see immediate change — that’s about two years out — but this is a big milestone. We hit it right on the nose, we’re ahead of schedule and under budget, so we couldn’t be happier.”
The next phase of the project includes installing more than a thousand sections of 60-inch pipe inside the tunnel before it is cemented underground.
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