Explain the Bridge Selection Criteria - Underwater inspection?

Various factors influence the bridge selection criteria. As a minimum, all structures must receive routine underwater inspection at intervals not to exceed five years. This is the maximum interval at which all underwater elements of a bridge, even if it is in sound condition, must be inspected. More frequent routine and in-depth inspections may be desirable for many structures and necessary for critical structures. Inspection frequency may be increased in those bridges where deterioration has been noticed during previous inspections. Factors to consider in establishing the inspection frequency and levels of inspection include:

- Age

- Type of construction material

- Configuration of the substructure

- Adjacent water features such as dams, dikes or marines

- Susceptibility of streambed materials to scour

- Maintenance history

- Saltwater environment

- Waterway pollution

- Damage due to water borne traffic, debris etc.