This portion of the project consisted of base building renovations to the existing Main Post Office (MPO) building in preparation for the next phase: a tenant improvement fit-out to construct the new regional campus for the Internal Revenue Service (IRS), to house roughly 5,000 employees.

Renovations to the nearly 927,000-square-foot MPO, listed on the National Register of Historic Places, included extensive architectural, structural and mechanical/electrical/plumbing demolition as part of a complete gut-out of former postal operations space. The core and shell phase involved the historic restoration of façade and lobby areas, and resulted in the addition of fourteen elevators, a grand staircase, a skylight spanning five levels, and new MEP and life safety systems.