The ideal time of the year to arrange an underwater inspection is when the conditions are ideal, including when the water is low, the air is clean, or the water is visibly clear. For bridges placed in backwaters, the dive must be scheduled for a similar time period of the tide. Underwater inspections are of three types:

Routine inspection:

This routine inspection involves an underwater visual and kinesthetic check. This examination is frequently described as a “swim by" inspection. The main goal is to find evident damaged or issues. It should be a Level I inspection. This inspection needs to be done once per year. Even when a bridge is in good condition, all underwater components must be checked at least once every six months. Getting in for a detailed inspection may be necessary if any issues are found during the underwater bridge inspection.

Detail inspection:

This inspection is much more thorough and aimed at taking accurate measurements of any deteriorating or destroyed regions that may be masked by marine vegetation. The marine vegetation must be cleaned for surface inspection, and this cleaning is only permitted in a few sample regions of the complete underwater construction. Additionally, those structures where issues were found or encountered while routine inspection must also undergo detailed inspection. 

Once every five years, a Level II inspection should be conducted. Even if a bridge is in good condition, all underwater components must be inspected at least once every six months. A Level III inspection should be done when the bridge appears to be damaged during this inspection or when any issue is seen or noticed that may call for additional inquiry. These services include visual inspection and condition and structure inspection.

Special inspection:

This inspection was not scheduled. The following situations necessitate performing this inspection:

 

  •   After exceptional floods.

  •   After vessel effect.

  •   The build-up of waste at ports and abutments.

  •   Uncommon prop wash from vessels.