Tunnelling was part of the new Tren Urbano transit system in San Juan, Puerto Rico. Four tunnels in soil were designed and constructed with shotcrete linings using the sequential excavation method (SEM), which uses some aspects of the New Austrian Tunneling Method (NATM). Four 6-m-diameter tunnels of about 100 m in length were required to reserve two historic structures located above the subway alignment. Two of the four tunnels were constructed as part of a turnout to a future line. Cover over the SEM tunnels ranges from 20 to 5 m. Some of the tunnels are located less than 1 m from each other in the turnout section. Detailed analysis of the staged construction was undertaken to design shotcrete lining thickness, shotcrete strength, and reinforcing with welded wire fabric and lattice girders. Several variations in lining section were required, which depended on sequence of tunnel excavation and depth of cover. Further refinement of the lining design was possible by considering the initial lining as permanent since it had been constructed with final structure quality requirements. Compensation grouting effectively mitigated ground movements and building settlement was limited. Tunnel lining convergence measurements revealed the lining displacements due to excavation of adjacent or overlying tunnel construction to be within acceptable limits. Design and construction of the tunnels as sequentially excavated with shotcrete support (SEM) was unprecedented in Puerto Rico and not in widespread practice in the continental United States. Further, this was the first major United States underground transit construction project with design-build project delivery.