After Three Decades, Narragansett CSO Project Nears Completion

Source: KLa Systems

A 30-year clean-up in Rhode Island hit an important milestone with the completion of a 2.2-mile tunnel to transport combined sewer and stormwater. The Narragansett Bay Commission (NBC) began work on the monumental project known as RestoredWaters RI back in 1993 to address long-standing pollution issues in Narragansett Bay. This initiative, which is part of a Combined Sewer Overflow (CSO) Abatement Program, has the ongoing aim of improving water quality, supporting marine life, and boosting Rhode Island’s economy.

In the decades since the project’s inception, NBC ratepayers have invested close to $2 billion to bolster the health of the bay. In addition to improving the waterways, the project has created more than 2,000 direct and indirect jobs, benefiting industries like fishing and tourism.

The CSO Abatement Project was conceived as part of a consent agreement with the Rhode Island Department of Environmental Management (RIDEM) to comply with the Federal Clean Water Act and prevent diverting CSOs into the bay during rainy seasons.

The project is currently in Phase III, which began in 2008 and includes the construction of the Pawtucket Tunnel. Located 125 feet below the surface, the tunnel is designed to store and transport storm-related sewer and stormwater overflow to be treated before discharge into Narragansett Bay. The completion of this tunnel is a huge step towards cleaner waters and healthier marine ecosystems.

Phase III is divided into four sub-phases, with Phase IIIA focusing on the Pawtucket Tunnel, representing a substantial portion of the project cost. The tunnel, along with other facilities like launching and receiving work shafts, drop shafts, and a tunnel pump station, will contribute to reducing annual combined sewer overflow volumes by 98% and achieving an 80% reduction in shellfish bed enclosures.

In total, Phase III is estimated to cost $800 million. Funding comes from multiple sources, including a loan from the USEPA’s Water Infrastructure Finance and Innovation Act (WIFIA), which covers almost half of the total cost. Other projects that are part of Phase III include an 11,600-ft. long deep rock tunnel to provide storage for 58.5 million gallons of water and a 160-ft. deep pump station. The project also incorporates construction of green infrastructure to absorb stormwater and reduce pressure on the sewer system, further improving water quality.

Once completed, Phase III will close out the federally mandated CSO Abatement Program. Overall, the project is critical for Rhode Island’s environmental sustainability, economic growth, and compliance with regulatory standards.

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