Boston's "Big Dig" project was substantially larger and more complex than the SR 99 tunnel. It was eight miles long with multiple tunnels and bridges, including a signature cable-stayed bridge over the Charles River. The project was built while traffic was maintained through the construction zone and businesses stayed open with heavy equipment operating outside their doorsteps. This approach required extensive traffic management and mitigation.

The SR 99 tunnel will be less than half the length of what was constructed in Boston. By using a tunnel boring machine, we will minimize traffic disruptions and impacts to the waterfront and downtown.