An ornate octagonal-in-plan sanctuary topped by an elaborately coffered, 100-ft-high dome is ringed with elaborate murals. The dome is suspended from a 135-ft-dia steel-and-concrete outer dome.

Computer models indicated a risk of failure of four of the eight sanctuary walls, which meant the project team had to devise a strategy to add new shear walls without damaging the historic interior.

During the preconstruction phase, a worker crawled through a 2-ft-wide interstitial space between the domes to take measurements for the development of a plan of action. During construction, crews removed the walls of the corridors that encircle the sanctuary because they could more easily be replaced if damaged. Crews then built nearly five-story shear walls, from the basement to the top of the "drum," that consist of structural steel in-filled with shotcrete.

Crews had to dig the 10-ft-deep footings for the shear walls in tight basement quarters. "It was almost like a mining operation—it was all done by hand," Montoya says. "Our overhead space was no more than 5 ft."

Since water could leech from the shotcrete and damage priceless murals and mahogany wainscoting on the inner sanctuary walls, the contractor used offset metal- stud framing to allow for a 2-in. air gap. Crews also installed waterproof plastic sheeting.

Once the walls were stabilized, craftworkers began removing accumulated dirt and past water damage from the murals, cast stone, paint, wood, marble, Zenitherm and numerous other interior surfaces. Pews that seat nearly 2,000 people were reupholstered. Scaffolding up to 100 ft in height provided access to work areas.

Judges were particularly impressed by the team's careful restoration of a 25-ft-dia, 100-ton stained glass window. Workers disassembled and removed the 25 stained glass panels and 125 cast stone elements comprising the surround. Cores were drilled in the stone to add 1-in.-dia steel reinforcement, intended to resist seismic loads. Once the pieces were rehabilitated, the window was reassembled on site.

Crews also removed, restored and reinstalled more than 100 additional art glass windows, plus a 4,100-piece pipe organ.

New building systems, architectural lighting and complex sound-dampening treatments were added in ways that camouflaged them as much as possible.

Since the only space for the building's two new air handlers was in the basement directly beneath the sanctuary, noise and vibration control was paramount. The plenum was lined with multiple layers of drywall and sound insulation. Acoustical-isolation hangers and duct "silencers" prevent vibration transmission. MATT Construction rigorously enforced a custom-designed quality control inspection program to ensure each element was properly installed.

On the exterior, crews performed lead paint abatement, waterproofing and stone repair.