In early February, Wrecking Corporation of America returned to 2501 Pennsylvania Avenue and the site of the historic Luzon Apartment Building to continue demolition and excavation work for a new condominium project. Built in 1896, the original Luzon Building was a 20,000-square-foot load-bearing brick structure with wood framing. Vacant and deserted for the last 15 years, the building's roof had rotted and the structure had been significantly damaged by water and decay.
However, demolishing the Luzon has not been just a "simple" matter of taking a wrecking ball to the structure. Instead, in order to preserve the historic streetscape, the Luzon's existing five-story brick façade has been shored and carefully severed from the balance of the structure, which has been razed. The new building will be constructed and the existing façade retrofitted to it.
After Wrecking Corporation performed some preliminary demolition work, Berkel Contracting Company drilled and poured caissons and attached base plates to form foundations for the prefabricated steel towers that support the façade. These steel towers, fabricated and installed by Winkler Company, were brought to the site and linked together, forming a freestanding structure. Once in place, 4-inch-diameter tube steel was guided through the window openings and attached to 8-inch to 10-inch wale beams bolted into the brick façade on both sides. Wood shims driven between the wale beams and the brick façade ensure that the support structure is firmly attached and immobile.
"We have to do this very carefully because the façade wall is not in great shape," says Terry Anderson, executive vice president of Wrecking Corporation. "Certain walls were more deteriorated than others. Some of the floors had caved in. At the beginning we didn't really want to put anybody in the building to do any physical separation. We had to raze the back of the building before we could do any physical separation."
Wrecking Corporation used a 90-ton P&H crane to raze the back of the building. Much of the demolition debris was then packed to form a hard, temporary surface for the Genie S-80 telescopic boom. Men work from the Genie's platform to manually separate the remaining wood framing from the façade.
"The idea is to demo it, rough clean it, get the debris out of here, build a pad so we can work, and then go back with a lift to really do the fine tuning," says Anderson.
Wrecking Corporation has started removing debris using a Hitachi 330 excavator with a Lemac bucket. This work will continue for two weeks until the site is slightly below sidewalk elevation. Wrecking Corporation will then demobilize to allow preparatory work for the excavation phase.
The excavation of the site will go down another 20 feet below street grade. In order to do this, the foundations of the neighboring buildings to the north and west of the site will be reinforced with underpinning pits. These underpinning pits are hand-dug, narrow shafts adjacent to the neighboring buildings; lagging boards are installed as work progresses to keep soil from falling into the shaft. When the excavation reaches the bottom of the foundations, workers tunnel up underneath the buildings to create cavities that are then filled with concrete. "This provides a new foundation for these buildings that are at the depth we need to allow us to excavate for our site," says Anderson. "We'll then work with the sheeting and shoring contractor while we excavate the site. In order to facilitate this, there will be soldier beams and lagging and some tie backs around the perimeter of the site to support the excavation."
Working on a small D.C. site has been challenging. City-certified flagmen must be present for trucks to enter and exit the site. A silt fence for erosion control and a chain link fence for security ring the site. Highway plates across the sidewalk at the site entrance help protect the numerous utilities running underneath, and signage and placards help maintain safety for the pedestrians and vehicular traffic that run alongside the project.
Maintaining and protecting the façade during demolition, excavation and construction is also difficult. "It's much easier to come in and start over — raze the entire structure and rebuild," says Anderson. "Obviously they don't because they want to maintain the historic character of these sites, and the (Historic Preservation Review Board) will not allow them to take down the original façade and rebuild it in kind."
Retrofitting the old façade to the new building will not be easy either. The irregular floor heights and brick construction that characterized buildings in the 19th century are not compatible with 21st century design. Therefore, the project's architects and engineers will continue to evaluate the exposed façade to determine how to best incorporate it in the design of the new building. The steel towers will remain in place until the façade is permanently attached.
Wrecking Corporation will be finished with the excavation by July 1, 2007. The entire project is scheduled for completion by mid-2008.