Clark/Banks, A Joint Venture (CBJV), which is composed of Clark Construction Group, LLC, of Bethesda, Maryland, and Banks Contracting Company, Inc., of Baltimore, is in Phase 1 of a $573-million project to construct Johns Hopkins Hospital's (JHH) new clinical building in Baltimore. The design team is led by Perkins+Will of Los Angeles. Bard, Rao + Athanas Consulting Engineers, LLC, of Boston is the mechanical and electrical consultant, and Thornton Tomasetti of Washington, D.C., is the structural consultant. The 1.5-million-square-foot medical building will feature two connected towers — one for adult cardiovascular and critical care and the other for children's care. It is currently the largest health care project under construction in the nation.
The project is the new main entrance and centerpiece of a $1.2-billion JHH redevelopment plan to increase research and clinical space and replace outdated hospital buildings with advanced facilities. There is a two-level below-grade basement of cast-in-place concrete, and the above-ground structure is structural steel. The skin will be curtain wall and precast with a cast-in-place brick veneer.
When CBJV arrived on-site in November 2006, other buildings on-site had been partially demolished by other contractors. Berg Demolition continued with the demolition of the Jefferson Building, the only remaining building on the project site. Complicating this process, however, was the fact that the Jefferson Building was adjacent to the Nelson/Harvey Building, which would remain in place.
"We actually had to physically separate the Jefferson Building from the existing Nelson/Harvey Building on the north side," says John Barotti, senior vice president with Clark Construction. "We cut the slab and disconnected the structure so the vibration would not (affect) the other building. We had to use selective demolition and soft strip operations."
After removing the ceilings, duct work, conduit, and other interior items, Berg Demolition used remote-controlled Brokk hydraulic hammers and Bobcat skid-steer loaders to selectively demolish the concrete shell and remove the debris. Barotti explains that there was extensive coordination with the hospital during the demolition process due to the close proximity to patients and hospital operations.
"For awhile we were only working from 6 a.m. to 8 a.m.," says Barotti. "We were shut down until 4 p.m., and then we could work at night. In some cases we couldn't (work) at all until later in the evening or on weekends. However, we were able to achieve significant noise and vibration reduction by severing building connection points, adding noise abatement materials and modifying equipment."
CBJV is nearing completion of the excavation process of Phase 1. There have been two bulk excavations of the job, with the lowest building elevation reaching 28 feet below grade. At this level, CBJV had to connect to a tow line tunnel, which serves a major role in the new hospital's operations.
"An interesting fact about this hospital is that there is no loading dock and there is no commercial kitchen or cafeteria," says Barotti. "All supplies, even food, come from across the street and through this underground tunnel below the parking garage and Orleans Street."
This level of the project also includes excavation for all of the storage areas, the elevator pits and the central sterilization area, which is a recent addition to the hospital's plans. These types of design changes and enhancements are something the project team has come to expect on hospital projects.
"A hospital is a complex facility, so it's been under design for a long time. It's an evolution and it's continuously changing," says Barotti. There are two primary reasons for this. Because the hospital wants to have the latest technology when it opens its doors in 2011, high-tech equipment will not be ordered until the last minute. For this reason, 25 areas in the hospital towers will only be shelled during construction, and they won't be completed until the specific equipment has been ordered.
In anticipation of this, the MEP design has to be flexible. "What they typically do is over-design the area," explains Barotti. "They'll give it a little extra power, a little extra air conditioning, extra floor loading, and extra ceiling loading in case we have to hang anything off the ceiling. It's kind of like a belt and suspenders approach." Therefore, when the final specs do arrive these spaces can be customized for each piece of state-of-the-art equipment.
Furthermore, Johns Hopkins Hospital has continued its fundraising efforts since the project has been in the design phase. Therefore, as more money becomes available, enhancements can be added to the project.
"Originally the hospital was going to rely on an adjacent building to do all of the sterilization for it. They came to realize that it was an operational need to have it in the hospital building itself, and they realized they had the budget to do it," says Barotti. "So, we were at the point where we were excavating walls for this area where (central sterilization) would be going in. Now we're out there making the changes to work the new plan."
The floor plan of the lower level is very "process oriented and functional," but much smaller than the actual floor plan of the towers, explains Barotti. "When you go down to the B2 level, which is all the way down, you're at deep elevation 72. Because the floor plan gets larger as you go up, there are some floor elevations that don't start until elevation 99. That's slab-on-grade elevation."
To support the foundations, there are a total of 275 caissons ranging in size from 3 feet to 11 feet. The caissons at elevation 72, the deepest elevation, go down over 30 feet, and the caissons for elevation 99, which are at the slab-on-grade level, go down approximately 40 feet. Because this is a caisson pile and steel job, the caps are not significantly larger than the caisson foundations. Instead, the new facility is a "brace-framed" job.
"There's heavy structural steel that gets encapsulated in concrete at the lower levels," says Barotti. "We'll come in around the elevators basically, and we'll set some large steel. Then we'll come in and cast them in place, too. They are the brace frames for the whole project. They keep the towers stable."
Because the footprint for the underground floors is smaller, these perimeter walls are on the interior. CBJV has been able to open cut and lay the dirt back for many of these walls. Once they are constructed, the exterior will be backfilled. The perimeter walls for the upper levels are just minor foundation walls to support one level of precast or window system, and then the next level continues with structural steel.
Phase 1 also includes the utility work. The project ties into Baltimore city power, sewer, water, and storm systems. The hospital does have its own central plant, so the project will link to the hospital's plant systems.
When the excavation and foundation work are complete, the project will move into Phase 2, which is the vertical construction. Although designed as one building with an expansion joint between them, the towers are being constructed as two different structures. CBJV had access to the children's tower site first, so vertical construction will be about three months ahead of the adult tower. The new towers will tie into existing buildings along certain corridors, and two bridges will connect the towers to existing parking garages.
When it is completely finished, the new clinical facility will be 15 stories high, with 12 active hospital floors. At an anticipated final cost of over $600 million, the entire 1.5-million-square-foot project is scheduled for substantial completion by December 23, 2010.
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