The CA/T project, considered the largest infrastructure project undertaken in the US to date, involved the replacement of a congested, dysfunctional, and outdated six-lane elevated viaduct with a widened eight to ten-lane underground expressway constructed through the heart of Boston. The complex construction sequencing of this mega project included many temporary bypass ramps, the temporary underpinning of the existing viaduct and other above-ground facilities; geotechnical and hazardous material removal and remediation; sequential demolition of existing structures, disposal of excavated materials, and demolition of debris. The CA/T project is regarded as one of the most ambitious and complex public enterprises undertaken in modern times. Tony Lancellotti, PE served as CA/T’s Deputy Program Manager and Design Manager (1993 to 2004) and Lead Tunnel Designer and Project Engineer (1986 to 1993) for I-90. Peter Donahue, PE served along with Tony as his deputy and eventually became the Design Manager and the Deputy Project Manager of the Project Management Consultant Team. Technical complexities included tunneling through the heavily built-up historical city with many older underground tunnels, utilities, and services; prevention of settlement and damage to existing facilities; and traffic management and minimization of driver delays during construction.