Pavement Inspection

Depression

Depressions are localized pavement surface areas having elevations slightly lower than those of the surrounding pavement. In many instances, light depressions are not noticeable until after a rain, when ponding water creates "birdbath" areas. However, depressions can also be located without rain because of stains created by the ponding of water. Depressions can be caused by settlement of the foundation soil, or can be built during construction. Depressions cause roughness, and when filled with water of sufficient depth can cause hydroplaning of aircraft.

Severity Distress Example Description
Low Photo showing a low-severity depression with standing water in it. A red line has been drawn on the photo to outline the area with the depression. Depression can be observed or located by water ponding or stained area due to ponding, only slightly affects pavement riding quality, and may cause hydroplaning potential on runways.

Runways and High-Speed Taxiways: 1/8 to 1/2 in (3 to 13 mm)
Taxiways and Aprons: 1/2 to 1 in (13 to 25 mm)
Medium Photo showing a medium-severity depression on the pavement. The area of the depression is noticeable due to water staining on the pavement. A red line has also been drawn on the photo to outline the area with the depression. Depression can be observed or located by water ponding or stained area due to ponding, moderately affects pavement riding quality, and causes hydroplaning potential on runways.

Runways and High-Speed Taxiways: 1/2 to 1 in (13 to 25 mm)
Taxiways and Aprons: 1 to 2 in (25 to 51 mm)
High Photo showing a large-severity depression on the edge of an asphalt pavement. A stringline has been stretched across the depression to illustrate the depth, and some water staining on the pavement surface is noticeable at the center of the depression. A red line has also been drawn on the photo to outline the area with the depression. The depression can be readily observed, severely affects pavement riding quality, and causes definite hydroplaning potential.

Runways and High-Speed Taxiways: > 1 in (> 25 mm)
Taxiways and Aprons: > 2 in (> 51 mm)