Shortly after the NEPTUNE Canada Vertical Profiler System (VPS) was deployed last fall, a significant problem developed: we could extend the instrument float upward, but we could not retract it back down to the base platform. NGK technicians tried mightily, but were ultimately unable to find a way to retract the float. Our only recourse was to recover the VPS and bring it back to Victoria for repairs.
On 14 May 2010, NEPTUNE Canada, ROPOS and CCGS Tully crews worked together to retrieve the VPS from its seafloor location, 396m below the surface on Barkley Slope. To accomplish this, a custom kit had been prepared, which would allow ROPOS to the corral the errant float and rig the VPS for recovery by rope.
The kit included:
- 1 800m high-strength rope
- 4 floats
- 7 30lb weights with carabiner attachments
- 1 acoustic release
- 3 large barrels and 1 bucket (to hold the rope)
Our elaborate rescue plan detailed the following steps:
- Lower the rescue kit to the seafloor by ship's winch
- Dive with ROPOS to locate the kit
- Remove 30lb weights from kit and attach to VPS float until it becomes neutrally buoyant
- Use ROPOS to carefully guide the float down into its stowage basket and secure it
- Close VPS base platform lifting bales and hook lifting point to rope end
- After recovering ROPOS to ship, trigger acoustic release to spring the floats (attached to rope end) from the rescue platform
- Locate floats and send Zodiac crew to carry the rope end back to ship
- Thread rope through A-frame pulleys onto ship's winch
- Pull the VPS up from the seafloor to the ship
- Transfer the load to the ship's crane
- Swing the VPS around from the A-frame, over the aft-starboard side and onto deck
Amazingly, the plan went off mostly without hitch. Both Tully and ROPOS crews were highly effective in their various roles executing this complicated and potentially dangerous operation. The only snag (literally) was an unforeseen tangle of ropes floating above the rescue kit after one of the barrel tops became unfastened prematurely. But this problem was solved when ROPOS pilots used their robotic arms to carefully untangled the mess. After a long day of careful teamwork, the VPS arrived on deck by suppertime.
Some, however, were none too pleased with our efforts: those who lost their hangout when we so rudely plucked it from the seabed. A great number of fish and at least one miffed octopus witnessed the rescue operation. Sorry, guys! We'll try to return the VPS as soon as possible!