By H.H. Angus & Associates
Toronto General Hospital RedevelopmentEngineering
The largest healthcare redevelopment in Canadian history is now complete, at the University Health Network's Toronto General Hospital site. One of the older hospital sites in the city's downtown core,...
The largest healthcare redevelopment in Canadian history is now complete, at the University Health Network’s Toronto General Hospital site. One of the older hospital sites in the city’s downtown core, Toronto General has been under reconstruction for the past decade. Carried out in three phases, the project covered 334,440 m2 (3.6 million sq. ft.) of new and renovated healthcare facilities.
The plan seemed simple: take an 80-year old site at University Avenue, Gerrard and Elizabeth Streets, tear down two of its integral buildings and replace them with two new state-of-the-art facilities. The execution of the plan, however, presented a challenge: the footprints and system requirements were different, and the entire service infrastructure had to be reconfigured. Most important, all the work had to be carried out without interrupting the ongoing provision of healthcare at the site.
The Emergency and Engineering Building, which contained a large portion of the utility services for the entire hospital campus, was the first to be demolished. It was replaced by the $35-million R. Fraser Elliott Building for support services, a 16,629 m2, six storey facility.
Next to go was the Bell Wing, built in the 1920s, and rife with redundant services and overlapping systems awkwardly interconnected. It was replaced by the $107-million New Clinical Services Building, 41,800 m2 and 12 storeys, to accommodate cardiology, neurosurgery, orthopedic surgery and solid organ transplants.
The third component, completed in December 2004, was the renovation of the 15-storey Norman Urquhart Wing, which forms the main entry and linking structure on the campus.
H.H. Angus & Associates Limited of Toronto (Michael Loughry, P. Eng., was project leader), worked closely with multiple clients and other consultants from the initial concept meeting through to the commissioning.
Reconfiguring the service infrastructure
Construction had to be carefully phased and designed because over the years the site had evolved with a tangled web of utility services that needed to be either dismantled and rebuilt, or reconfigured. In addition, the site for the new R. Fraser Elliott Building was directly on top of the existing bulk medical gas tank farm that fed not just the Toronto General Hospital, but also the nearby Hospital for Sick Children, Mount Sinai Hospital and Princess Margaret Hospital. Seamlessly relocating these tanks to a new location at College and Elizabeth Streets was the first major challenge.
As well, the Engineering Building that was demolished on the site had housed utilities and associated equipment, which meant rerouting the water, sewer and natural gas lines, the main electrical feeders, and steam piping. Many of these were required services that could not be shut down.
Before demolition could begin, an entire substation had to be relocated, which took nine months. The main electrical feeders were replaced completely without a single shutdown or use of a standby generator. The new main electrical service included three underground high voltage (13,000 volt) feeder lines from Toronto Hydro, the main services entrance switchgear, and countless supply ducts for every building and area on the hospital site.
Because of the complexity of the systems and procedures, H.H. Angus played an instrumental role in the coordination of the subcontractors as well as the construction. The consulting engineers prepared a manual outlining a step-by-step procedure for the various tie-ins, shutdowns, temporary connections and testing, and circulated it to the other parties for feedback before work began. The project was treated as a 5-9s design, requiring redundant feeds and a critical approach to provide continuity in operations. The final implementation proceeded without incident and with no disruption to the healthcare professionals on four campuses.
New Clinical Services Building
The New Clinical Services Building is extremely complex, with 22 operating rooms complete with associated surgical support spaces, a diagnostic imaging suite with MRIs, CTs, radiology and ultrasound equipment, and three floors of patient rooms. It also has extensive public spaces, including the large Patient Court. The mechanical systems are designed to be flexible and able to support future code changes and technological developments.
The entire second floor is designated as the surgery floor, with 100% fresh air requirements. Four operating rooms have been designed with 40 air changes per hour, each served by its own dedicated air handling unit. The other 18 operating rooms have 25 air changes an hour. Laminar flow diffusers incorporate 99.99% HEPA filters as an additional stage of filtration to air entering the room. Ceiling diffusers and low-level exhaust grilles at the corners of the rooms are arranged to maintain a continuous directional airflow of clean, conditioned air over the operating table. The rooms are at a positive pressure to ensure a clean and sterile environment, and temperatures can be adjusted between 15C to 29C depending on the type of surgery taking place. Occupancy sensors are used to save energy when the rooms are not being used, and heat recovery wheels recover 80% of the waste energy within the exhaust stream.
The building has a four-storey Patient Court rising from the fourth to the eighth floor. The challenge here was to condition this large space in the most efficient and unobtrusive manner, while ensuring that its fully glazed outside walls stayed free of frost and condensation during winter months. To solve this, about 90% of the total conditioned air is distributed at the base of the curtain wall along the south and west perimeter, using low level linear bar grilles. Return air is extracted using sidewall grilles along the east and north walls. High level grilles at ceiling level extract air during the winter heating season to ensure a continuous wash of warm air across the glazing and maintain its surface temperature above the dew point. In the summer months, return air is drawn through sidewall grilles at the fourth floor ceiling level of the adjacent patient rooms, a design that conditions the lower 3.6 – 4.8 m of the court where it is “occupied.” The equipment to maintain this well-conditioned environment is controlled and adjusted by a fully automated system based on occupancy levels and temperatures both inside and out.
Another feature of the Clinical Services Building is the third floor mechanical room. H.H. Angus requested provision for a mechanical room directly above the operating rooms. It was difficult to convince the client and other consultants that the best place for a major plant was in the middle of a 12 storey building, but there were clear advantages. Maintaining a regular floor-to-ceiling height for the plant allowed the new building to be linked with the existing Norman Urquhart wing on all the desired levels. Further, the proximity to the operating rooms meant there was no floor space lost to duct shafts in the operating rooms. Finally, placing all the serviceable components in the ducts on the level above kept them out of the operating room ceiling space.
While the limited room height restricted the size of the air-handling units, this potential disadvantage produced a fringe benefit. Instead of one larger unit, several of the operating rooms are fed by two smaller, equally sized units, providing a parallel system. In case of unit failure, either of the units can serve the operating room at a reduced capacity.
The design resulted in lower mechanical and electrical system costs. With the distance between the services and plant reduced, less ductwork and piping is needed. The reduction in riser and shaft space allowed hundreds of square feet of space to be reclaimed for healthcare uses.
Many small design features in the new buildings helped improve energy efficiency. For example, there are set-back functions on motors, low temperature condenser reheat,
and heat recovery wheels wherever possible. Heat pipe technology reclaims heat from emergency area systems and there is a high quality steam condensate recovery network. A centralized, programmable low voltage lighting control system simplifies and reduces the lighting requirements in the administrative areas of the R. Fraser Elliott Building.
Food storage freezers with -20C capability are located in the dietary area of the R. Fraser Elliot Building. To prevent frost from forming and causing heaving in the concrete sub-floor, waste heat from the freezers is sent through embedded piping in the floor below the units, thus eliminating the need to provide a separate underfloor heating system.
The electrical system has non-interruptive “make before break” automatic transfer switches in order to minimize the disruptive effects of switching from emergency to normal power during blackouts and weekly tests.
Despite the complexity, the project was completed on time, with the Fraser Elliott Building opening in 2000, the Clinical Services Building in 2003, and the Norman Urquhart Wing, in 2004.
Client: University Health Network
Mechanical & electrical consultant: H.H. Angus & Associates (Thomas Halpenny, P.Eng., Michael Loughry, P.Eng., Shaunak Pandit, P.Eng., Kevin Feeney, P.Eng., Sergey Polak, Rod Mons, P.Eng., John Bastian)
Electrical consultant, Phase 3: Mulvey & Banani International.
Structural consultants: Carruthers & Wallace, Phase 1; Quinn Dressel Associates, Phase 2; Yolles Partnership, Phase 3.
Architect: HOK Urbana, Phase 1 & 2; Bregman + Hamann, Phase 3.
Construction managers: PCL, Phase 1; EllisDon, Phase 2 & 3;
Contractors: Modern Niagara, Sayers & Associates, H. Griffiths, Guild Electric, Comstock Canada, Ontario Electric