Current Projects

Sewer Project Begins

James Finlaw - Herald New Staff Reporter: 10/8/2002

Descending to a depth of 40 feet below street level, the wide, dusty path cuts down into the hillside like a driveway leading into a subterranean parking garage.

An excavator sits at the bottom of the sloping road, which ends at a wall of solid granite. The excavator operator deftly maneuvers the machine's bucket, scooping up mounds of earth and fractured granite and depositing them into a waiting trailer truck. Once filled with the debris, the truck begins its rumbling ascent from the terminus of the path. As it moves up towards the street, the truck is dwarfed by the towering retaining walls that line the sides of the pit.

The scene has been replayed again and again over the past few months, as construction crews with J.F. Shea Co. Inc. of Walnut, Calif., have worked to carve the road into the hill rising between Swift and Arnold streets.

The creation of the road is a major component of the city's $115 million Combined Sewer Overflow Abatement Project. The city is under a federal court order to construct a 20-foot-wide, 3-mile-long sewer tunnel to halt pollution to Mount Hope Bay.

The road the company is constructing is at the point where a 300-foot-long tunnel boring machine will soon begin drilling a huge sewer tunnel beneath the city. The city sits atop a vast granite plateau, and the city and its engineers have determined the best place for the boring machine to enter the plateau is the hillside between Swift and Arnold streets.

Sometime around the start of the New Year, the massive machine will descend the road and begin boring into the granite wall at the base of the slope. The machine's prime component is a disc-shaped drill that is 20 feet in diameter and studded with foot-long cutting blades. As the machine pushes into the rock, the blades churn the granite into small pieces that will be deposited into "muck carts" located behind the machine. The carts will be set on rail lines that J.F. Shea will lay behind the boring machine as it progresses. The carts will be hitched to a small locomotive which will pull them out of the tunnel once they are full. The crushed rock will be carted to a pit located just outside the mouth of the tunnel where a conveyor belt will be set. The carts will automatically tip and spill their contents onto the belt. The conveyor belt will whisk the crushed stone from the pit to a concrete pad situated at the top of the road now being dug into the hillside.

Front-end-loaders will then lift the refuse from the pile into trucks, which will take the rock to Tiverton for disposal.

The new tunnel is designed to intercept a number of the city's 19 existing sewage tunnels which are hopelessly outdated, and which currently allow more than one billion gallons of raw sewage and rainwater to spill into Mount Hope Bay every year.

During rainstorms where more than a quarter of an inch of rain falls, the 19th century sewers become overburdened and overflow into the bay. The new tunnel is designed to handle 106 gallons of sewage and rainwater per day, and to stop the flow of untreated sewage into the bay. The tunnel will run north from the Swift Street area to the intersection of Spring and Pearl streets at an average depth of 100 feet below the surface. The tunnel will then head east to Lowell Street where it will end.

Robert Otoski of Camp, Dresser and McKee, the city's engineering firm, is the project engineer. He and project manager Robert Hulick of Stone & Webster Engineering say the sewer project is on time and on budget. "It looks like it's all going to come together. We're right on target," Hulick said Monday.

Hulick and Otoski said more digging and blasting work is needed before the road or "tunnel portal" is complete. The men said a total of 50 to 60 feet of the granite wall must be exposed before the boring machine can enter its base. "We need 40 feet of rock above the tunnel boring machine so it's self-supporting," said Otoski.

Because granite is such a solid substance, it is stable enough to withstand the drilling. Otoski said it is unlikely that work crews will have to do much to shore up, seal or buttress the tunnel. "There will be limited lining where there are rock fractures, but most of it should be fine," said Otoski. "The tunnel is already there. We just have to take the rock out of it."

The boring machine is currently being modified and rebuilt to meet the specifications of the city's CSO project. Hulick said it is being assembled in Milwaukee, Wis., for testing. Once it passes the tests, it will be taken apart and shipped to Fall River in pieces. Hulick said he expects to receive the first part of the machine within the next three weeks. The remaining parts will be delivered in subsequent weeks, and the drilling will begin in December or January. "We hope to be mining in the portal with the (boring machine) by the end of the year," said Hulick.

According to the court order, the three-mile tunnel must be completed by Dec. 31, 2004. The court order was issued by Federal District Court Judge Rya Zobel in 1992 in response to a lawsuit filed against the city by the Conservation Law Foundation. The group filed the suit in 1988 to force the city to stop polluting the Taunton River and Mount Hope Bay with sewage.

The creation of the "tunnel portal" is the latest in a series of steps the city has taken to address its sewer problem. The city's wastewater treatment plant received a $20 million upgrade in 1999 to prepare the facility for the increased flow the new tunnel will generate.

In July, a 460-foot-long, 7-foot diameter pipe was laid beneath Bay Street. The pipe will one day connect the sewer plant to the new sewer tunnel, which is located diagonally across the street from the plant. The connecting pipe was installed by P.Gioioso and Sons of Hyde Park for $829,500.

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