Boston Project Uses a Triple Dip of Tunneling Technology

STRAIGHT SHOT Metcalf & Eddy’s Martin and MWRA’s McBride (right) helped guide complicated tunneling to ease overstressed facilities. (Photo by William J. Angelo for ENR)

Six south shore Boston communities are getting a new $200-million sewage pumping and transport system to help reduce chronic surcharge and backup problems. The work involves utilizing three different tunneling techniques to cross a river, peninsula and bay.

Work on the Braintree-Weymouth relief facilities project started in 1999 and will wrap up by year’s end. The effort includes constructing a 45-million-gallon-per-day intermediate pump station; 2.7-mile-long, 42-in.-dia hard-rock tunnel under Boston Harbor; 60-in.-dia relief interceptor; and two 4,000-ft-long, 36-in.-dia siphons. All will supplement existing facilities struggling to handle waste from the burgeoning towns of Braintree, Hingham, Holbrook, Randolph, Weymouth and parts of Quincy, all of which have suffered from overflow problems.

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The lines will tie into the $3.6-billion Deer Island wastewater treatment facility, which went on line in 1995. “The existing lines and 28-mgd pump station are old and overstressed so we need to increase capacity by as much as 20 mgd,” says Michael J. McBride, deputy chief operating officer of the Massachusetts Water Resources Authority, the owner. The older pump station will be rebuilt for about $17 million. Bids will be let this fall.

The last tunnel component to be put in place is the twin horizontal directional bores under the Fore River in Weymouth. Work started in April, about 10 months late because of contractual problems at the new Excelon natural gas-fired powerplant, which was used as the lay-down area for 600-ft-long sections of plastic and steel pipe. The plant was a Raytheon Engineering and Constructors project, part of the assets purchased by Washington Group International, Boise.

Crews from drilling subcontractor Laney Directional Drilling Co., Humble, Texas, holed through on the first bore on May 5 and shortly will begin the pull-back operation enlarging the slurry-filled hole from 11 in. to 34 in., to 47 in. and ultimately to 64 in. The tunnel will hold a 42-in. steel sleeve containing a 36-in. high-density polyethylene pipe. The hole-through was complicated by a 30-in. high-pressure gas line feeding...