The I-93 Ramps & Viaducts were designed to efficiently move 200,000 cars daily into and out of Boston’s “big dig”. The GM2 Complex Bridge Group’s design incorporated both balanced cantilever and span-by-span erection schemes to construct the 15,488 linear feet of precast concrete segments. The erection methods accommodated spans ranging from 100’ to 200’ and horizontal curve radii from 212’ to 6,500’. Roadway widths within the project vary from 22’ to 96’. In order to economically construct the design, just three types of box girders and columns were developed, minimizing the different types of formwork required for casting. The foundation construction consisted of multiple and single drilled shaft locations in order to work within a complex site with numerous underground obstructions.

The concrete box shapes with uniformly sized circular pier elements create very clean lines that complement the adjoining Leonard P. Zakim Bunker Hill Bridge.