Contaminated Runway

For purposes of condition reporting and airplane performance, a runway is considered contaminated when more than 25 percent of the runway surface area (within the reported length and the width being used) is covered by frost, ice, and any depth of snow, slush, or water.
Note: While ash, sand, oil, and rubber (see “Slippery When Wet” definition) are reportable contaminants, there is no associated airplane performance data available and a depth would not be reported. (AC-150/5200-28F).

A runway is considered contaminated whenever standing water, ice, snow, slush, frost in any form, heavy rubber, or other substances are present. A runway is contaminated with respect to rubber deposits or other friction-degrading substances when the average friction value for any 500-foot segment of the runway within the ALD fails below the recommended minimum friction level and the average friction value in the adjacent 500-foot segments falls below the maintenance planning friction level. (PCG definition).

Source: AC-150/5200-28F, PCG