An inspection of the culvert should include the approach roadway, the embankment, the headwalls and wingwalls, the waterway, and the culvert barrel.
Roadway. The roadway over the culvert should be inspected for sags and cracks in the pavement that are the result of settlement. These may be evident in both the roadway itself and adjacent guiderail. The settlement may be the result of poorly compacted material adjacent to the culvert piping (infiltration or transportation of fines by water flowing through the backfill), or settlement of the culvert itself. The structural integrity of the culvert itself may or may not have been compromised. An inspection of the culvert must be made.
Embankment, Headwalls, and Wingwalls. The embankment, headwalls, and wing — walls at the inlet and outlet ends of the culvert should be inspected for signs of erosion, undermining, and settlement. If there is erosion at the ends, the structural integrity of the culvert will not necessarily be immediately compromised, but the hydraulic capacity will be affected. Any erosion or undermining will only worsen, and corrective action should be scheduled. If there is separation between the culvert and the endwalls, there could be a loss of supporting soil somewhere along the length of the culvert, which would affect structural capacity.
Waterway. The waterway should be inspected directly upstream and downstream for changes in the drainage. The culvert may have effected the changes in this drainage, and conversely, the changes in the drainage may have an effect on the culvert. An example of the former is where the velocity of the water is increased because of the channeling effect of the culvert. This velocity change could then cause either scour or accretion downstream. An example of the latter is accretion affecting the backwater up to the culvert, which can alter the subsequent performance of the culvert. In addition, the waterway should be inspected for accumulations of debris and sediment at both the inlet and the outlet and within the culvert itself.
Culvert Barrel. The barrel or structure of the culvert should be inspected for defects, distortions, and deflections. The nature of these will depend upon the type of culvert being inspected.
