How to Measure

Depressions are measured in square feet (square meters) of surface area. The maximum depth of the depression determines the level of severity. This depth can be measured by placing a 10 ft. (3-m) straightedge across the depressed area and measuring the maximum depth in inches (millimeters). Depressions larger than 10 ft. (3 m) across must be measured by using a stringline.

 Severity

Maximum Depth of Depression

Runways and High-Speed Taxiways

Taxiways and Aprons

L

<1/8 to ½ in.
(3 to 13mm)

<1/2 to 1 in.
(13 to 25 mm)

M

 ½ to 1 in.
(13 mm to 25 mm)

1 to 2 in.
(25 to 51 mm)

H

>1 in.
(25 mm)

>2 in.
(51 mm)