What conditions can affect commercial diving operations?
Strong currents due to tidal changes can make diving operations exceedingly difficult.
The primary (and obvious) difference between work performed by divers and that performed by topside personnel is the environment in which the tasks are conducted.
It is, however, the specific aspects of the underwater environment that are often overlooked by those unfamiliar with the industry. The list of such aspects includes current, visibility, sea state, tides, vessel traffic, possible contamination, and vessel movement.
These are in addition to factors such as weather, crane or tugging operations which may take place overhead, the possibility of stray electrical current in the work area, differential pressure (Delta P), concern over vessels utilizing active sonar in the vicinity, and equipment which may become energized while the diver is in the water.
Current
Current, measured in knots, can often become too strong for a diver to operate effectively. If the current results from tidal action, one solution is to schedule necessary diving operations during periods of slack tide.
Tides
Aside from tide-induced current, other issues relating to the tide must be considered during marine projects. For a variety of reasons, some work can be most effectively accomplished at either high or low tide. Thus, scheduling of such work takes tidal conditions into account. Also, a rising tide during a long dive may force a change in a decompression table. This, obviously, must be taken into account during each day's pre-dive safety meeting.
Visibility
Visibility, or lack thereof, may limit some operations, but divers frequently ply their trade in black water. Where a record must be made in such limited-visibility situations, infrared cameras can be employed.
Sea State
Sea state can have a significant impact on diving operations, especially if dive operations are conducted from a vessel that is subject to such wave action.
One problem is that any in-water decompression in rough seas may be impossible if the diver would likely be pulled away from his scheduled in-water decompression stop. Such a scenario is dangerous and to be avoided at all costs.
Vessel Traffic
Vessel traffic in the area can likewise be a concern, both because some vessels produce an enormous wake and because many vessels are operated by irresponsible individuals who motor too fast or too close to the dive platform.
Vessel Movement
Some dive operations are conducted from a moving vessel – so-called “live boating.” Such operations are inherently more dangerous and carry with them additional safety precautions.
However, even when not live boating, vessel movement must be taken into account in the dive plan. Take for example the situation where a diver enters the water during flood tide to perform work on a vessel moored alongside a pier. When the tide turns, the positioning of the vessel may likewise change. The change in position can be quite dangerous if not anticipated in the dive plan.
Differential Pressure (Delta P)
Differential pressure (Delta P) situations often exist, for example, at hydroelectric dams or beneath vessels that have a ruptured hull. It is of paramount importance to either eliminate the differential pressure prior to the diver entering the water or to account for such Delta-P situation in the dive plan.
Effective Hazard Analysis
As can be seen by the few examples above, some conditions can be addressed by altering the dive plan, while other conditions can (and should) be avoided altogether.
Experienced commercial diving companies are able to conduct an effective hazard analysis and present the available options to their clients in an understandable way.