Dispersion of De-Icing Chemicals to the Areas Along the Runways at Oslo Airport Gardermoen 2007-01-3351

Oslo Airport Gardermoen is located on the largest unconfined groundwater aquifer in Norway and acts upon strict governmental regulations concerning groundwater balance and contamination of groundwater and surface waters. In the cold Norwegian winter climate, de-icing of aircrafts and runway systems is necessary for safety reasons. The aircraft de-icing fluids (type 1 and type 2) are based on propylene glycol (PG). Potassium Formate (PF) is used for de-icing of runways and taxiways. Aircraft de-icing takes place on remote de-icing platforms. At each platform there is a system for drainage of excess de-icing fluid, but some is passively dispersed from the aircraft body to the area along the runways and mix with snow. During melting, release of de-icers to the ground occurs. In such events the chemicals need to be biologically degraded in the unsaturated zone to meet the governmental requirements.

To avoid negative effects on the environment and to meet governmental regulations, information on use and dispersion of de-icing chemicals is essential. Quantity and distribution of the dispersion, surface run-off and infiltration processes in frozen soil is significant factors in order to determine the chemical load to the underground and potential load to local streams.

The dispersion of de-icing chemicals has been monitored at Oslo Airport Gardermoen from 1999 - present. The results show that about 10% of used PG is dispersed to the area along the runways, and that the highest load is observed from 400 m to 1000 m after start position for take-off. The chemical load is also observed to be higher closer to the runway edge. The total load of PG is 100 - 200 tons per season (170-340 tons as COD). All 200 tons of Formate (70 tons as COD) used on the runway system is dispersed to the same area. The snow in the hot spot area can contain up to 10.000 ppm as COD, and the load can be up to 3 kg COD/m² in one season. Results from the 2005/2006 and 2006/2007 seasons indicate that it is mainly PG type 2 that is being dispersed to the area along the runways, and the hypothesis is that most of the type 1 PG drips off the aircraft on the de-icing platforms or on the taxiways when taxing to the runway.