Underwater inspection is the process of sending a diver down to perform an inspection of an asset visually and tactilely. Most common underwater inspections are performed on bridges, dams, and hydro facilities. For each of these structures, a portion of it’s support is in water that is deeper than what can be waded. To inspect the portion of the structure below water, a diver enters the water, swims around the structure, and performs the inspection. While underwater the diver observes the condition of the structure visually and tactilely. A tactile or hands on inspection can identify issues with a structure when the diver can see or when there is little to no visibility underwater. Condition of the structure as observed during the dive along with environment conditions in which the dive was performed are recorded in report for the structure’s owner. The report can be used for future decisions and as a reference for the next underwater inspection by the dive team.
A dive team is comprised of a minimum of 3 members along with the associated diving equipment. Most often, given the difficult working environment underwater, the dive team uses surface supplied air equipment which can be staged in a boat on open water or on the shore. The environment in which the diver is working can vary greatly from calm clear water to dark water with no visibility in high currents. With the size of team, equipment required, and difficult working environment, an efficient operation is key to keep project cost within budget. To calculate the budget, an understanding of the level of effort for an underwater inspection is required.
The levels of intensity for an underwater inspection are defined in the Bridge Inspector’s Reference Manual. Level I is a visual and/or tactile inspection. Level II is a detailed inspection with a defined quantity of cleaning aquatic life from the structure. Level III is a detailed dive using non-destructive or partially destructive testing to assess conditions beyond what can be done visually or tactilely. Generally, Level I and Level II intensity are performed in during a regularly planned underwater inspection. A Level III intensity dive is reserved for situations identified as requiring more information and hence more time underwater with specialized equipment than a dive to Level I or II intensity.
After this session, participants will have a thorough understanding of the effort involved with underwater inspection.
