After taking three years to travel little more than 2 miles, the Narragansett Bay Commission finally reached a finish line of sorts in February – the completion of a massive tunnel 125 feet below Pawtucket.
That’s when a spinning, 30-foot-wide tunnel boring machine broke though the last few inches of bedrock, marking a big milestone in the decadeslong effort to help make Narragansett Bay cleaner.
The 2.2-mile tunnel is part of a massive undertaking begun more than 20 years ago by the commission to replace its century-old sewer and water runoff infrastructure below ground. The tunnel under the eastern bank of the Blackstone and Seekonk rivers is actually the third and final one built as part of the Combined Sewer Overflow Abatement Program, otherwise known as RestoredWaters RI.
The new tunnel will eventually capture as much as 58.5 million gallons of sewer and stormwater runoff and retain it so it can be treated at the Bucklin Point Wastewater Treatment Facility in East Providence before being discharged into the Seekonk River.
NBC says the tunnel will hold 98% of the overflow volumes during storms that would otherwise be dumped untreated into the river, which flows into Narragansett Bay. It’s estimated that the project will reduce shellfish bed closures by 80%.
With the digging of the storage tunnel complete, workers have now turned their attention to four down shafts and pumping stations that will connect overflow sewer and stormwater pipes to the tunnel, and the tunnel to the Bucklin Point facility.
Work on the third tunnel is being managed through a joint contract that includes CB3A, the U.S.-based subsidiary of a French construction and engineering firm, and Massachusetts-based Barletta Heavy Division Inc., which were awarded a $479.4 million contract to complete the combined sewer overflow project. Officials say the Pawtucket project should be completed by 2026.
It’s been estimated the cost of the third tunnel will total $836 million when completed, nearly 60% of the $1.4 billion estimated price tag of the complete RestoredWaters RI.
Boring the tunnel under Pawtucket and Central Falls wasn’t exactly easy.
Most challenging was navigating Rhode Island’s underground geologic formations, which scientists refer to as “uniformly ununiform,” said Jamie Samons, NBC public affairs officer.
“We have sandstone and shale. Working underground requires unique skills and there aren’t many people that do this type of work,” she said.
The first part of the project, which started in 2021, involved blasting the hard bedrock to make the vertical shafts bordering the tunnel. Then a massive German-made tunnel boring machine that cost more than $200 million was lowered in, grinding millimeters of rock at a time.
James White, president and business manager of International Union of Operating Engineers Local 57, says the union has had between 80 to 100 members active on the site since the start.
While not the first tunnel in Rhode Island, “there was nothing of this scale,” White said. “We had never seen a tunnel like this.”
Moving the boring machine was a project in itself.
“They had to assemble it above ground and dissemble it underground. If you could picture that,” he said. “They had to drill and blast the first part of the tunnel in order to fit part of the machine in. And then repeat the process.”
It’s been a costly endeavor. Samons says the commission took steps to lower the cost of RestoredWater RI in part by extending the completion date from 2026 to 2041 for some aspects. In 2019, the project received a 1.9% interest loan covering half the cost from the U.S. Environmental Protection Agency. And in May, the Rhode Island Infrastructure Bank approved $45 million in bonds from the Clean Water State Revolving Fund, with $5.2 million in principal forgiveness stemming from the Bipartisan Infrastructure Law.
Still, the average household’s sewer bill is projected to increase 23% to $643 by 2025.
But the results of the first two storage tunnels in Providence, completed in 2008 and 2014, are clear.
For decades, sections of upper Narragansett Bay and other areas had to be closed to shellfishing because of poor water quality, particularly after heavy rainfall.
Now tests indicate the water in the bay is cleaner than it has been for decades, and shellfish beds there that were permanently closed have now been reopened.
“This is a giant tunnel that is essentially a holding tank instead of going into the treatment plant directly. When the sewage treatment plant gets a day where it rains an inch or two, it just cannot handle that,” White said. “And all that raw sewage went directly into the bay. It was not that long ago that if we had a rainy day an awful lot of the beaches would be closed. Now, you don’t hear of that as much as you did before.”
