AD 2016 Q4

LEADERSHIP
Americans Richie Kohler and Evan Kovacs, in conjunction
with a group of Russian divers, planned to take deep
wreck exploration to a new level. They had made a
single checkout dive the year before with the intention
of conducting a significant project with the Russians in
2016. Their diver support and safety plan restored my
confidence in the complicated endeavor of deep mixed-gas
rebreather diving, which had been shaken by the death of
my friend Carl Spencer on the Britannic in 2009.
EQUIPMENT AND OPERATIONS
A key safety feature of the dive operations was a
commercial wet diving bell. A 70-page standard
operating procedure (SOP) document outlined the
expedition’s safety protocols.
Only four divers would be in the water on dive days,
each using his own choice of rebreather with a teamchosen
diluent of 9/73 trimix. An emergency bailout
profile would be based on a carried three-gas protocol:
13/60 trimix, 20/30 trimix and 100 percent oxygen. All
other gas would be in the diving bell, the main point of
bailout at depth.
Diving-bell operations would be predicated by the
surface vessel maintaining a three-point mooring
position to keep the bell on station. In the case of a lost
mooring or a drastic shift in weather conditions during
the 45-plus-minute bottom phase, the diving bell could
shift from its position above the wreck to beyond where
the divers could see it. Protocols for this scenario would
be supported by ROVs and submersibles that oversaw
and maintained contact with the dive team — the
submersible pilots would direct the divers to an offstation
diving bell in mid-water, out of sight of divers on
the wreck.
Because the diving bell was a critical element of
the safety protocols, the team had to become familiar
with all aspects of its operation. Each exploration diver
would have to understand oxygen partial pressure (PO 2 )
calibration and venting, verbal and light communications,
buoyancy adjustments, onboard and surface-supplied
emergency open-circuit gas, bell master responsibilities
and management of an unconscious diver.
One nominated diver would be the dedicated bell
master for the dive and communicate with both the
dive team and the topside crew. The bell master would
confirm each diver was clear to ascend and move the
bell only when the slowest profile had cleared the stop.
Any diver ascending into the open bell at depth had
to confirm the PO 2 was within the acceptable range
before going off his loop (rebreather) and breathing
in the atmosphere of the bell. At the maximum depth
of the bell (about 300 feet) the atmosphere in the
bell would be hyperoxic with a PO 2 in excess of 2.0.
The 2016 Britannic expedition employed a commercial wet diving
bell for decompression and emergencies. This was only the second
noncommercial civilian expedition in history to use a diving bell.
Although the vent gas was air, the PO 2 in the bell could
be dropped by venting bailout gas into the bell or
having the topside crew pump down bottom gas. With
time spent in the bell, exhaled gas from a diver’s loop
would require a venting phase to prevent changes in
buoyancy. In rough seas, buoyancy adjustments could
also be used to eliminate the hard recoil of the cables if
the bell began bouncing with the ocean.
All diving operations were conducted under the
watchful eye of the topside control center via the ROV.
Should anyone actually get lost on the wreck, the
submersible pilots could simply hold up a directional sign
with one hand while eating a sandwich with the other.
EMERGENCY PROCEDURES
For the team of technical divers, using a bell was a new
approach to a mixed-gas project. Many emergency
scenarios had to be considered and factored into the
SOP, including central nervous system oxygen toxicity, air
embolism and loss of consciousness. An unconscious diver
drill was conducted topside to provide practice securing a
diver in the bell with a ratchet strap, maintaining an open
airway and performing chest compressions.
In the scenario a diver “found unconscious” at depth
was quickly placed inside the bell and strapped against
the bulkhead with his head above water. The rescue
divers cut away his equipment and secured him. The
bell master communicated the mock emergency to
the surface and followed the directions of the topside
hyperbaric doctor. As directed, the dive team took
turns maintaining an airway and performing chest
compressions. The rescue divers remained on their
loops in the bell, and the topside crew regulated the
atmosphere in the bell for the injured diver.
The plan dictated that an injured diver should ascend
with the dive team’s decompression schedule until the
topside team determined they should lift the injured diver
out of the water. A support diver would descend to the
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