By Warrant Officer William Finnamore, Diving Inspector, Canadian Armed Forces Directorate of Diving Safety
Ottawa, Ontario — Imagine sitting on the dive boat all geared up and ready for entry into the water. It’s a nice warm sunny day and the task at hand is a relatively easy one. The dive supervisor has done his checks and you and your dive buddy are told to enter the water and dive.
As your head goes below the waterline you quickly realize that the relatively easy task has become much harder due to the near zero visibility in the murky water. Welcome to the world of the Canadian Army (CA) diver!
CA divers are Combat Engineers who undergo a selection process and upon successful completion, follow a rigorous eight week-long Combat Diver course which qualifies them to conduct combat engineering operations underwater. That is the role of the Combat Diver – to extend Combat Engineer operations beyond land and into the water.
These divers can be tasked with a variety of jobs that include underwater construction, demolition, reconnaissance and minefield breaching operations just to name a few.
This type of diving is most often done in inland waterways where the underwater visibility, on a good day, is less than favourable. It is a good day of diving when you can see farther then the face plate of your mask. Diving in this type of environment is one of the many reasons that CA divers and all Canadian Armed Forces (CAF) divers put a great deal of emphasis on safety.
In the CAF, there exists a strong safety culture. From the moment a candidate enters the diving training system, they are subjected to a plethora of diving rules and regulations they all must follow and for good reasons. A constant enforcement of these rules by diving supervisors instills great respect for diving safety.
Candidates leave the training environment with an in-depth knowledge of all rules and regulations and a positive attitude that sustains a healthy diving safety culture that resonates throughout CA regiments with diving teams.
One of the more challenging tasks (read: hazardous) for CA divers is the recovery of equipment including vehicles that have fallen into the water. This type of operation can be conducted in depths of water no greater than 30 metres – CA divers’ depth limitation.
The hazards that arise from this type of operation can vary based on the size and sensitivity of the equipment lost to the bottom, the depth of the water, the temperature and visibility. CA divers are compressed air breathing apparatus (CABA) divers only, and according to CAF diving rules and regulations, they are not allowed to regularly conduct decompression diving.
Decompression diving entails stops within the water column that divers ascending to the surface must make for a specified period of time, measured in minutes, along a shot line which is marked in meters indicating depth below the surface.
Ascending too quickly from too deep a depth can cause a variety of serious problems, including decompression sickness. That is caused by nitrogen bubbles forming in the bloodstream and tissues of the body. The bubbles occur if you move from the higher pressure of deep water towards the surface where the surrounding pressure is lower in too short a space of time.
Those limiting factors must be kept in mind when determining how to tackle underwater challenges.
CA divers are very adaptive and determined, and as a group they have developed through training and experience the ability to solve many the complex problems that may arise on a mission.
Having to recover vehicles or bridge sections that have sunken to the bottom lakes or river beds can be hazardous even in ideal conditions. If mistakes are made, the consequences can be severe. This is why it is imperative that divers continuously keep safety as the number one priority, practice the required skills often and strive to complete all tasks with strict compliance to CAF diving rules and regulations.
These types of recovery operations are specifically taught on the Combat Diver course which is run out of the Army Dive Center located in the Canadian Forces School of Military Engineering at CFB Gagetown. The school is home to lessons learned, which are passed on to students in an effort to not repeat past mistakes and avoid future occurrences.
When combined with limited to zero visibility, underwater recovery operations become significantly more difficult. When submerged, divers rely on signals that if not passed visually or by underwater communications equipment, are passed to one another using rope signals or buddy lines – the latter entailing a pair of divers tethered arm-to-arm by a line no greater than three metres.
The most dangerous part of the operation occurs when the vehicle breaks ground reaction or “suction” of the river or lake bed and begins to rise to the surface. Once suction is broken, the vehicle generally surfaces at a high rate of ascent.
It is at this point that incidents may and have occurred. Ropes or buddy lines can get snagged on the ascending vehicle and unexpectedly pull the diver or pair of divers to the surface. Because the divers’ lungs are full of air, it is critical that ascent is controlled to prevent rapid expansion of that air within the lungs, which could possibly rupture one or both lungs. As well, an uncontrolled ascent has a very high potential to cause arterial gas embolism, which can be fatal to the diver.
This key information is taught to all divers and reinforces the need to pay strict attention to managing lines to prevent such an incident from occurring. CA divers, for the most part, dive in pairs and it is the responsibility of the more senior diver (recognized as the lead diver) to supervise the task.
The lead diver closely monitors the activities of the working diver, the movement of the vehicle to be extracted, controls all lines, and more importantly, pulls the working diver back at the first indication of the vehicle breaking suction. This control measure proves extremely effective and lessons learned indicate risk to the diver(s) has been suitably reduced to “very low”.
It’s easy to see that the world of the CA diver is a challenging one.
Regardless of the diver’s level of experience, all understand that the diving environment can be a hostile and unforgiving place. So, as only visitors to this rather hazardous world, safety remains at the forefront of each diver’s mind.
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Source: Canadian Armed Forces