June 12, 2023
On Monday, June 12, the Rapid Excavation and Tunneling Conference (RETC) kicked off in Boston, MA. More than 1,375 people were registered on the first day of the three-day conference that features industry-leading technical sessions, short courses, networking events and a vibrant exhibit hall where the latest technologies for tunneling and underground construction are on display.
The welcoming luncheon included a presentation that focused on the lessons the Massachusetts Water Resources Authority (MWRA) has learned from decades of tunneling projects in the greater Boston area. Fred Laskey, executive director of MWRA, credited the areas of tunnels with creating some of the best and cleanest water and urban beaches in the United States. The water and the pristine conditions currently found in Boston were not always so clean, according to Laskey, who said the city was “built with its back to the harbor because of the pollution that once existed.”
Commitment to infrastructure projects including more than 100 miles of water tunnels helped change that. Now, the MWRA serves 3.1 million people and provides an average of 200 million gallons of clean water to residents per day.
Winston Churchill said in a 1948 speech, “Those who fail to learn from history are doomed to repeat it.” On Monday, Kathy Murtagh, director of tunnel redundancy, MWRA, spoke about the lessons the MWRA has learned from its decades of building tunnels so that mistakes of the past will not be repeated in projects of the future that are part of ongoing designs of its next deep rock tunneling project, the Metropolitan Water Tunnel Program (MWTP). Focusing on a handful of tunnels including City Tunnel, Malden, Dorchester Tunnel, Inter Island Tunnel and Braintree West, Murtagh gave a presentation that was part history lesson and part planning for the future.
Because of past projects, the MWRA has learned how to tunnel through various ground conditions and fault lines. The MWTP will be built in the same conditions and cross the same fault lines. Among the lessons, Murtagh noted that a lining failure on the Dorchester tunnel that took six years to fix has had a heavy influence on future work as did a fire at the Inter Island project.
Among the lessons learned are the:
• Superiority of tunneling vs. cut and cover
• Optimize tunnel heading lengths to balance multiple considerations and risks
• Investigate faults early
• Tunneling in the Argillite can be very variable
• Don’t expect to speed
• Plan for water
• Select shaft sites carefully
• Maintain good relationships with host communities/neighborhoods
• Previous experience serves as an important risk mitigation tool.