Capitol Building Utility G Tunnels

Washington, DC

The tunnels, part of a system used to supply the heating and cooling for a large number of government buildings in the Washington, DC area, were built in the 1930s and required significant upgrades to meet today’s standards.

As conduits of fundamental heating and cooling utilities for critically important government buildings, the “G” tunnels are vital infrastructure for government operations, including the Supreme Court. The tunnels had not received upgrades since their construction and were susceptible to break downs and other malfunctions. The Architect of the Capitol required specialized utility upgrade construction in a unique, challenging and high security environment.

Conti worked through very difficult conditions, such as extreme heat, tight underground spaces and ever-changing windows of work to deliver this design-build project. The project team constructed two new emergency egress structures after demolishing an obsolete one, repaired 652’ of structural concrete, replaced lighting and installed a new exhaust fan to improve temperature cooling requirements.

Key aspects of the project included enormous flexibility to work around the schedules of each Supreme Court Justice. The team worked around the clock on a fast tracked timetable to respond to the Justices’ schedules.

The AOC gave Conti an “Outstanding” performance rating for the quality of the work delivered.

Conti exercised extreme flexibility to complete operations on time and budget without disrupting the work of Supreme Court personnel.

Project details

Client Architect of the Capitol
Value $5.03M
Status Completed
Key features
  • Design-build project
  • Constructed egress structures
  • Demolished former egress structure
  • Formed and installed rebar
  • Implemented side-rail system
  • Repaired structural concrete
  • Installed exhaust fan
  • Restored site

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