Narragansett Bay Commission (NBC) has completed the excavation and lining of the 2.2-mile Pawtucket Tunnel. The project is Phase III of NBC’s Combined Sewer Overflow (CSO) Abatement Program, known comprehensively as RestoredWaters RI. It features a deep rock tunnel 125-ft below the surface. The tunnel will store and transport storm-related combined sewer and stormwater overflow to NBC’s Bucklin Point Wastewater Treatment Facility for full treatment before discharge into Narragansett Bay – all leading the way for cleaner waterways throughout Rhode Island.
The cutterhead of the tunnel boring machine (TBM), named “Chloe the Clean Water Cruncher,” was placed into the tunnel near Bucklin Point on June 22, 2022, marking the symbolic beginning of tunneling operations. Since then, the TBM has excavated 2.2-miles of earthen material spanning Pawtucket and Central Falls. Feb. 15 marked the breakthrough milestone for the tunneling operation (view the breakthrough video here).
“We are excited to complete this important milestone in the Phase III RestoredWaters RI project,” said NBC Chairman Vincent Mesolella. “We are continuing to see the positive results of the investments made through this project, including a significantly cleaner Narragansett Bay, reopening of shellfishing beds, and healthier waters for all Rhode Islanders for generations to come. I want to especially thank the individuals who’ve contributed to the success of the project on a daily basis, the NBC Board of Commissioners, our local legislative representatives and government supporters, our ratepayers, and the communities we serve.”
With the tunnel boring complete, the concrete-lined tunnel is capable of storing 58.5 million gallons of combined sewer and stormwater overflow ready for treatment and discharge. Storm-related sewage will be pumped to NBC’s Bucklin Point Wastewater Treatment Facility for full treatment. The next step of this phase of the CSO program will include the installation of drop shafts and outfalls, which will divert storm-related sewer overflow into the tunnel.
RestoredWaters RI is the largest public works project in Rhode Island history. It continues to improve the health of shellfishing and swimming beaches across Rhode Island, reduce annual combined sewer overflow, and create green spaces for public access. Phase III of the project supported 1,700 direct or indirect jobs over the past three years. For an inside look at the project and tunnel, visit RestoredWatersRI.com/Media-Room.
CSO Phase III Facts
CSO Phase III is divided into four sub-phases. Phase IIIA includes the Pawtucket Tunnel, which is the largest single facility in Phase III, representing approximately 2/3 of the anticipated project cost. The tunnel is an important step towards reaching compliance with NBC’s Consent Agreement with the Rhode Island Department of Environmental Management (RIDEM)
The program will protect the water quality in Narragansett Bay, contributing to reducing annual combined sewer overflow volumes by 98% and achieving an 80% reduction in shellfish bed enclosures
The project will create over 1,700 direct or indirect jobs
In 2019, the project received a loan through the USEPA’s Water Infrastructure Finance and Innovation Act (WIFIA) for 49% of the project cost
The CSO Phase III Facilities project includes design and/or construction of the following:
11,600 ft-long deep rock tunnel to provide a storage volume of 58.5 million gallonstwo launching, receiving work shaftsfour drop shafts to divert storm-related flow into the tunnel160 ft-deep tunnel pump station to transport flow from the tunnel to the Bucklin Point WWTF for treatmentseveral “green infrastructure” projects, providing permeable areas at the surface to absorb stormwater and keep it out of the sewer systemmodifications throughout the sewer system to optimize flow
limited areas of sewer separation, where stormwater is directed into a separate pipe from sanitary sewage
The purpose of the project is to implement the final phase of the federally mandated CSO Abatement Program, significantly reduce CSO volumes in the Bucklin Point service area, and eliminate overflows from a three-month storm (1.614 inches of rain in six hours).