MWRA Reaches Next Milestone on the MetroWest Water Supply Tunnel with the Completion of Tunnel Excavation

At 8:08 a.m. on Friday, October 27, MWRA reached another major milestone in the construction of the 17.6 mile MetroWest Water Supply Tunnel Project. Directly under the Mass Turnpike/Route 128 intersection, construction workers including the Tunnel Workers Local 88, Electricians Local 103 and the Operating Engineers Local 4 completed mining of the longest of the tunnel legs. The contractor is the joint venture team of Shea-Traylor-Healy, with construction management by Stone & Webster.

This final 6.6 mile leg was mined using a 16 foot diameter tunnel boring machine. With this "hole-through," the tunnel boring phase of the MetroWest Tunnel is finished. Two 430’ shafts remain to be excavated in Weston.

With the achievement by the contractor and workers, the tunnel is excavated along its entire length, starting at Shaft D in Marlborough where the tunnel will eventually be connected to the MWRA’s Walnut Hill Water Treatment Plant, also under construction. From there, the tunnel stretches eastward under Southborough, Framingham and Wayland to Shaft 5A in Weston, adjacent to the Massachusetts Turnpike/Route 128 interchange.

Mining of the MetroWest Water Supply Tunnel began in November 1996, when excavation of the first shaft (Shaft "L" in Framingham) started. Over the next three years, the entire tunnel will be lined with one-foot thick concrete, pressure tested and disinfected before being put in service in 2003.