Aeronautical quantity kinds dimensionless runwayContaminationCoverage Runway contamination coverage Proportion of runway that is contaminated. A runway is considered to be contaminated when more than 25% of the runway surface area(whether in isolated areas or not) within the required length and width being used is covered by the following:(a) Surface water more than 3 mm deep, or by slush or loose snow equivalent to more than 3 mm of water; (b) Snow which has been compressed into a solid mass which resists further compression and will hold together or break into lumps if picked up (compacted snow); or (c) Ice, including wet ice.