Central Artery/Tunnel "The Big Dig"

Brief Overview

As part of a joint venture, Slattery Skanska Inc. was awarded three contracts, totaling close to $1 billion, by the Massachusetts Highway Department to perform construction services on Boston’s impressive Central Artery project also known as “The Big Dig.”

The first contract called for the demolition and removal of existing roadway viaducts and the construction of approximately six miles of temporary and permanent roadways, six viaducts and twelve bridges. The project also included excavation and excavation support, construction of grade slabs on piles, traffic control systems, storm drainage, two stormwater pump stations, utility relocation and landscaping.

The two other contracts called for the construction of a combination of thousands of feet of cut-and-cover tunnels, boat sections, viaducts, jacked tunnels underneath active railroad tracks and roadway lanes. Methods being used are decking systems, temporary bridges and the underpinning of the elevated Central Artery viaduct. The team chose segmental precast concrete as the method of construction for the viaducts.

For the construction of the tunnel and boat sections, a combination of the following support excavation systems were utilized: slurry walls, sheet piling and soil stabilization using a freezing technique.  Excavation depths for utilities range up to 25 feet and extend through fill silts, sands, various clays and soils.