Progress Continues On Tunnel Project Despite Groundwater Issues

Dec 17, 2018

Credit Rebecca Green/WBOI News

Construction crews have spent the last year working on the Three Rivers Protection and Overflow Reduction Tunnel, as part of a broad effort to improve water quality in the city’s rivers.

In August, crews at the worksite near Dwenger Avenue had nearly finished a 200-foot deep shaft, which would generate enough space for a boring machine to begin drilling a five-mile tunnel.

TJ Short is the senior program manager for the tunnel project. His team is working in an aquifer -- or, enclosed space of permeable material such as sand and gravel, limestone, or sandstone. Water can flow through this, which Short says is a problem.

“In order to deal with the water, sometimes you have to use grout in the ground to slow down the amount of water that gets into your excavation,” said Short. “I think the grouting has gone slower than we anticipated.”

So the drilling hasn’t started -- yet. But officials aren’t concerned with the delay, and Short remains optimistic everything will end up back on track quickly.

Once drilling begins, the tunnel boring machine -- 20-feet in diameter and nicknamed “MamaJo” in a voting campaign earlier this summer -- is expected to complete its part of the project “within 18 months.”

“We’re one year into the project and it’s at least four years of this tunneling and all the site prep and all the other stuff. It’s just not time to panic yet,” he said.

The Three Rivers Protection and Overflow Reduction Tunnel is part of a 2008 consent decree with with U.S. Environmental Protection Agency and costs $188 million. It is projected to be completed by 2023.