Demolition of the damaged portion of the Pentagon began Oct. 18 after the discovery of microfractures in some concrete columns and slabs that caused a 1-in. shift in the structure. Detection of the shifts prompted officials to begin demolition sooner than planned.
Approximately 400,000 square feet of the Pentagon's wedges 1 and 2, including the outermost E, D and C rings between corridors four and five, will be demolished and reconstructed.
Prior to demolition, construction crews busily removed debris from the wedges, which were heavily damaged Sept. 11 when a hijacked airliner crashed into the west side of the building. Heat generated by the fire following the crash is believed to have caused the cracks in the columns and slabs.
New York City-based general contractor AMEC, which at the time of the crash was within days of completing renovation of Wedge 1, will reconstruct wedges 1 and 2.
Pentagon Renovation Program officials awarded AMEC a $520 million cost-plus-fee contract for the emergency repair, restoration and reconstruction. AMEC also is in charge of the six- to eight-week-long demolition.
Renovation officials plan to reconstruct much of the damaged area within a year. "It's very ambitious," says Tom Fontana, Pentagon Renovation Program spokes-person. "Our goal is to rebuild the E ring by next Sept. 11."
Upon completion, AMEC will turn over the area for tenant fit-out to Greeley, Colo.-based Hensel Phelps Construction Co., which heads up the design/build team that was awarded a contract worth up to $758 million for renovation of wedges 2 through 5.
While new materials will be used to rebuild the damaged areas, the reconstruction must conform to historic building requirements.
As the Pentagon was declared a historic building in 1992, renovation officials are working with the National Capital Planning Commission and other organizations to preserve the building's historic features.
Preservation of the building's limestone façade is emphasized in the reconstruction. Some of the limestone salvaged from the exterior of Wedge 1 will be cleaned and used in the reconstruction. An Indiana quarry adjacent to the one from which the original limestone came will supply the new limestone used on the exterior, says Fontana.
An airborne laser radar system that allows the creation of 3-D renderings of buildings is being used to size the limestone. Implemented by Toronto-based Optech under the supervision of the Army's Joint Precision Strike Demonstration Office, the technology makes it possible to accurately replace the razed and obliterated areas of the building.