Central de-icing facility at Toronto's airport

Largest facility of its kind in the world

By Ed Salenieks, P.Eng., and John Dejak, P.Eng., Marshall Macklin Monaghan

Canadian air regulations prohibit take-off when frost, ice or snow is adhering to any critical surface of the aircraft. This is referred to as the "clean aircraft concept". The concept is essential to the maintenance of flight safety. The pilot-in-command must be able to verify a "clean aircraft" from properly trained and qualified personnel.

The requirement to de-ice aircraft has been well established and de-icing of aircraft is a major activity at most airports in Canada during inclement winter weather conditions. At Toronto's Lester B. Pearson International Airport (LBPIA), prior to the Central De-icing Facility (CDF) becoming operational, aircraft were de-iced by airlines and fixed base operators (FBO) at selected apron perimeter locations outfitted with containment facilities just prior to taxiing to their take-off positions, and at some of the passenger boarding gates of Terminals 2 and 3, where Marshall Macklin Monaghan designed Canada's first dedicated at-gate glycol collection system.

Up to 12 B737-size aircraft can be de-iced at one time, with an equal number staged behind to await de-icing.

Glycol is the primary component of de-icing fluid. Glycol-containing fluids, if they find their way to local waterways, can increase the biochemical oxygen demand (BOD) during their degradation, a process resulting in depletion of oxygen with its associated impacts for aquatic plant and animal life. Glycol is now considered toxic to certain wildlife and aquatic life. Most airports in Canada were built long before environmental regulations governing contaminated water run-off were enacted, and many lack the infrastructure necessary to control large volumes of spent glycol fluid.

Over the last ten years, airports, airlines and FBOs across the country have begun to work together to improve the dispensing, collection and disposal of glycol fluids, in order to meet or exceed the airports' specific environmental and health standards. Although efforts thus far have been promising, the key to minimizing or eliminating the detrimental environmental and health effects of de-icing is to refine the process. This can be achieved by:

• improved de-icing fluid application, equipment and techniques to maximize de-icing efforts and materials and minimize personal exposure and over-application,
• centralizing and standardizing de-icing facilities for both airside operational and passenger safety reasons,
• collecting and discharging waste glycol fluids in an appropriate manner (e.g. current Canadian laws prohibit the discharge of fluids into natural watercourses with more than 100 mg/L of glycol),
• improved weather monitoring, and,
• minimizing the length of time between glycol applications and aircraft take-off (hold over time).

To begin to address these issues, the Greater Toronto Airports Authority (GTAA) undertook to implement a satellite de-icing facility located on a new taxiway extension at the airport. The one-bay facility served as a pilot project for the CDF and was commissioned for operation in the Fall of 1996.

In May, 1997, the GTAA retained Marshall Macklin Monaghan Limited (MMM) to carry out the planning, design and non-resident construction phase services for a unique, state-of-the-art de-icing facility (now known as the "Central De-icing Facility"). MMM utilised preliminary planning completed by the GTAA, Transport Canada, and Public Works and Goods and Services Canada (PWGSC), and the lessons learned from the Terminal 3 glycol recovery system, combined with the satellite facility, as the basis for the design of the CDF. The assignment included the preparation of a comprehensive design brief necessary for approval purposes. The design was completed for tendering in January of 1998.

The completed 65 acre complex will be capable of de-icing up to six Class E aircraft (e.g. B747), or twelve Class C aircraft (eg. B737, A320) at one time while the same number of aircraft can be staged in behind to await de-icing. Should the need arise, the facility is designed such that queued (or staged) aircraft also may be de-iced simultaneously, thus substantially increasing the throughput capacity of the facility. Once completely operational, the CDF will be the largest facility of its kind in the world.

The CDF features some of the most environmentally friendly systems in the world such as:

• All active paved areas are underlain with a geosynthetic liner (54 acres in total) to prevent glycol contamination of groundwater;
• All surface and subsurface runoff from active areas is collected in zones and directed to a series of 17 diversion chambers;
• Using a state-of-the-art computerised fluid management system, samples are taken at each diversion chamber to determine the glycol concentration and mode of disposal (e.g. to low concentration holding tank, to high concentration holding tank, or to sanitary sewer line); and,
• Fluids deemed to contain "low" or "high" concentrations of waste fluid are stored in separate 5-million litre, geosynthetic lined, concrete, in-ground storage tanks until loading into tanker trucks for off-site recycling or disposal can occur.

The facility boasts advanced methods to control and monitor the movement of both aircraft and de-icing operations vehicles such as:

• Comprehensive, locally controlled inset lighting system to control the taxiing of aircraft into the facility with flexibility to accommodate various classes of aircraft;
• Electronic, variable message signs to convey data to the pilot-in-command (e.g. duration of fluid application, type of fluid sprayed, etc.);
• Provisions for CCTV, infra-red cameras and future advanced ice detection cameras; and,
• Provisions for GPS monitoring and control of de-icing operations vehicles.

The facility also has a sophisticated glycol storage, handling and dispensing system, allowing de-icing vehicles to fill up at three locations within the pads. An operations control centre with control cab is sized to accommodate up to 40 personnel and to service/maintain up to three de-icing vehicles at a time.