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June 5, 2003
Photos courtesy of Nuprecon
A tethered worker helps dismantle the Seattle Opera House building for Nuprecon, which used a safety team to deal with the dangers of performing demolition work at high elevations with multiple construction crews.
As arts enthusiasts looked on, Seattle Mayor Greg Nickels broke open a 1928 time capsule originally sealed in the old Civic Center, and ceremonially kicked off the demolition and abatement of the 74-year-old Seattle Opera House.
This was the first stage in the historic building’s dramatic $127 million transformation into Marion Oliver McCaw Hall. Nuprecon performed the demolition work for Skanska, the general contractor.
A Russian nesting doll
The project was difficult due to a very compressed and highly linked schedule, technical complexity and unforeseen field conditions.
The structure was unique and difficult to renovate because it had been added to twice before.
Originally built as the Civic Center in 1927, the Opera House structure was built around the open-air auditorium, entombing the old seating bowl. For the 1962 World’s Fair, a shell was built to enclose the Opera House, creating buildings within buildings like a Russian nesting doll.
Further, because some of the structures being removed provided integral support to the remaining structure, preparations for the demolition work required careful planning with Skanska’s structural construction divisions.
Skanska added Nuprecon to the project design-build team meeting six months prior to demolition. The planning paid off — nine months of work was finished in 65 days.
High danger potential
The demolition was rather unconventional due to unusual sequencing requirements with ongoing construction. In order to meet the deadlines of the performance season, the contractor interwove the bracing plan, erection plan and demolition plan rather than perform them sequentially.
For example, a structure would be selectively demolished, and the contractor would intercede to build the new structure (eliminating the need for temporary bracing and shoring), followed by completion of the demolition activity.
The project had a high danger potential, since major structural demolition was performed at high elevations while multiple construction crews were working nearby.
For most of the project, six separate demolition crews worked simultaneously in different areas. At times, over 100 field workers were scheduled on a single day, with multiple cranes and advanced heavy equipment including demolition robotics.
Workers contended with traffic, dust and noise restrictions. Construction crews working in close proximity on all sides, above and below the demolition work, created a three-dimensional chess board for project management and safety.
To address this, a “safety hit team” was chartered to install safety equipment and protection as required. In one case, the demolition crew stopped using red tape as a barrier and erected fencing to ensure that a dangerous area was not traversed.
The long-reach tool on this modified Hitachi excavator helped demolition crews take apart the structure while preventing damage to nearby buildings and public areas.
A substantial amount of unexpected asbestos was uncovered during demolition, including unusual materials such as a woven rope used as a sound cushion on ductwork. Friable hair batt insulation in the auditorium attic had to be abated without interfering with the normal daily operation and performances in the auditorium.
A complex scaffolding platform within the attic space was engineered to contain and abate the insulation. Spot lead removal was performed on existing structural steel to accommodate the contractor’s seismic upgrades.
Mercer Arts Arena
The scope of the demolition work also included selective demolition at the Mercer Arts Arena to prepare the facility to temporarily house performances while the Opera House renovation was under way.
In the early phase, Nuprecon worked with Skanska to demolish slab on grade below the Opera House while performances were ongoing. The work was coordinated around “quiet times,” with late shifts and seven-day workweeks. The 62,000-square-foot Opera House was completely gutted while preserving the 60-foot high historic plaster ceiling.
Nearly 150 tons of steel were lowered from the 70-foot-high fly loft with construction crews working nearby. The rehearsal hall was demolished to allow for an additional 15 feet of building space underneath, requiring five coordinated demolition/construction phases to eliminate the need for shoring.
While the structure was held in place, foundations and pilings were removed below. The Opera House seating bowl demolition constituted heavy concrete removal inside a structure that was being partially preserved; raker beams were temporarily left for support during the west end total demolition.
An innovative abatement technique had to be developed to economically remove the asbestos-coated ground-level steel seating bowl (the old hockey arena).
The trickiest work
Some of the trickiest work came with the removal of the entire west end of the building. Careful engineering and coordination with the contractor was mandated because the west end was integral to the remaining structure.
The integrity of the entire building was dependent upon a massive beam supported by two columns that stood directly on the 250-foot line of separation for total removal. If the beam had been compromised in any way, the entire structure could have collapsed.
The removal had to be performed 60 feet up in a public area near adjacent buildings. A state-of-the-art 80-foot Long Reach demolition excavator was used to take apart the structure in a controlled, surgical manner.
The Long Reach can simultaneously cut and pulverize structural concrete and steel, creating neat debris piles for easy removal in an urban environment. The constraints of the work area required an 11-step process to remove each bay.
Recyling and salvaging
Nuprecon’s recycling division recycled the construction and demolition debris and provided the consolidated diversion reporting required for LEED silver certification.
Throughout the demolition phase, debris recycle rates were over 95 percent, easily meeting the 75 percent project target. Items including marble, carpeting, theater seats, light fixtures, doors and doorknobs, brass handrails and plumbing fixtures were salvaged for reuse in the renovated facility.
The demolition and abatement were finished on schedule in anticipation of the eagerly awaited grand opening this season.
Susan Cannon is vice president of planning and development for Nuprecon, a national demolition firm based in Snoqualmie.