The final stage of a massive storm water runoff and sewage collection and treatment project was set in motion by Rhode Island's Coastal Resources Management Council (CRMC) at an Oct. 13 online meeting.

Several issues need to be resolved, however, including where to dispose of 800,000 tons of pulverized rock and sediment. The Narragansett Bay Commission (NBC), the state's largest wastewater treatment operation, manages the combined sewer overflow (CSO) system, which is credited with significant pollution reduction in the upper Bay.

Then, in early November, the NBC voted to award its multi-sectioned CSO Phase III A/Pawtucket Tunnel building project to the CBNA Construction joint venture consisting of European-based Bouygues Construction, Barletta Engineering/Heavy Division, in Canton, Mass., and AECOM, the American multinational engineering firm.

According to an NBC spokesman, the Pawtucket Tunnel documents have yet to be signed, as there are additional requirements for the contracting team to meet, including the certification of minority, women and disadvantaged business participation, as well as equal employment opportunity qualifications as set forth by the state of Rhode Island.

The tunnel construction is just the first of four different projects that make up CSO Phase III and is, on its own, worth $245 million.

The entire final phase of the Narragansett Bay environmental upgrade will cost an estimated $548 million. Additional segments will be completed through 2041 and the work will include sewer connections, a smaller tunnel link, additional wastewater storage and green storm water infrastructure.

The NBC expects the Pawtucket Tunnel to be completed in 2025, and operational the year after that.

The CSO Phase III A/Pawtucket Tunnel project is the third and concluding phase of a comprehensive program to alleviate combined sewer overflow discharges into Narragansett Bay.

When boring operations begin in two years, crews will dig it to be 11,600 ft. long, with a diameter of 30 ft. It will be bored at a depth of 140 to 180 ft. below grade by a tunnel boring machine which will concurrently line the tube through rock with a pre-cast segmental concrete lining.

The three-phase CSO program kicked off in 2001 with construction of a 3-mi. long, 26-ft.-wide deep-rock tunnel under Providence to store stormwater runoff.

Phase II, completed in 2015, added CSO interceptors to the Providence Tunnel, several sewer separations projects and a wetlands storage facility.

The final phase is focused on the construction of the Pawtucket Tunnel underneath the communities of Pawtucket and Central Falls. The tunnel is designed to divert, store and treat 58.5 million gallons of combined sewer overflows from those towns before it is discharged into the Blackstone and Seekonk rivers.

Final plans have yet to be completed and submitted to CRMC, but the project also is set to have a tunnel pump station, four drop shafts, a tunnel odor-control facility and two additional treatment clarifiers to be built at Bucklin Point. Structures on nine properties in East Providence and Pawtucket will be demolished to prepare for construction.

The entire Pawtucket tunnel project received a loan covering half the cost from the U.S. Environmental Protection Agency. The Rhode Island Clean Water State Revolving Fund and other programs also will finance a portion of the enterprise's costs.

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