CRUISE REPORT

 

                                                     Cruise Number:  02-BV-02

                                                              F/V Big Valley

 

 

Area of Operation:  From Dutch Harbor Alaska to Seguam and Amukta Pass.

 

Itinery:  Depart Dutch Harbor, AK 10pm Oct. 30, 2002.  Transit west to Amukta and Seguam Pass.  Return to Dutch Harbor 8 Nov., 2002.

 

Participating Organizations:  NOAA/PMEL/OERD-2

 

Chief Scientist:  William J. Floering (NOAA/PMEL/OERD-2)

 

Cruise Objectives:  To recover damaged moorings in Seguam Pass and Amukta Pass.

 

Summery of Operations:  During the Sept. /Oct. cruise on the Canadian vessel Laurier we were unable to recover one mooring in Seguam Pass and one mooring in Amukta Pass.   The EdgeTech release on the Seguam Pass mooring was ranging but indicated it was in a horizontal position.  The assumption was that the single 48 inch float had separated from the mooring and what remained was sitting on the bottom in Seguam Pass.  The EdgeTech release on the Amukta Pass ADCP mooring indicated it was vertical but it would not release.  Some time after this mooring was deployed EdgeTech issued a recall on this particular release for a potential problem in the release motor bushing assembly.  During the Laurier cruise we spent several hours dragging large grapple hooks attempting to snag and recover both of these moorings.  We were unsuccessful in this attempt and the decision was made to go after these moorings at a later date and with additional mooring recovery equipment. 

 

On rather short notice we contracted the 100 foot fishing vessel Big Valley (Gary Edwards owner) and a Phantom ROV owned by Mark Blakesley.  We have successfully recovered other lost or damaged moorings using this equipment and were reasonably confident we could recover the Amukta and Seguam moorings as well.

 

The wind, surface and bottom currents in these passes made it difficult at best for the vessel to remain stationary over the target area and greatly limited the maneuverability of the small ROV.  Because the currents were high when we arrived at Amukta pass we decided to use a clump weight with sonar and grapple hooks attached.  We were hoping that we could home in on the vertical mooring string with the sonar and then snag it with the attached grapple hooks.  The tugging on the down wire as the waves passed the ship and the currents made it impossible to keep the sonar level enough to get accurate readings.  When the down wire weight tilted so did the attached sonar, rather then pinging out in front of the weight you would ping off the ocean bottom or towards the ocean surface.

 

From current predictions provided by OERD-2 we were expecting a favorable low current environment in Seguam pass.  The sonar/grapple idea was abandoned and we steamed 3 hours west to Seguam Pass.

 

At Seguam pass we did a number of drifts over the mooring site while ranging on the release to narrow down our search area.  Once we had a good idea where the release was and what our surface drift was going to be, we deployed the ROV on about 200 feet of umbilical tether, then deployed the down weight on a wire with the ROV umbilicus and spectra line attached to the wire.  The down weight was lowered to just above the ocean bottom.  Attached to the down weight and to the ROV was the Trackpoint system that acoustically gives you the location of the ROV and the down weight relative to the vessel.  Mounted on the front of the ROV was a Crosby hook on a breakaway rod.  Two tubes packed with Spectra line were mounted to the bottom of the ROV frame.  The approach was to hook the mooring with the breakaway hook, back the ROV away from the mooring, pull the 150 or so meters of Spectra line out of the packing tubes leaving the ROV free from the mooring.  For recovery the mooring was now attached to the Spectra line which ran up the down weight wire to the vessel.  There is underwater video available of the recovery of both of these moorings.

 

Once the ROV was deployed, with a little searching we found the anchor, release, wire, and temperature sensors for the Seguam Pass mooring.  We attached the hook to the mooring wire, recovered the ROV and then recovered what remained of the mooring.  As expected the 48 inch float had broken off the mooring and had drifted away.  Since the wire broke near the top of the mooring we were able to recover the acoustic release and 5 of the 6 SBE39 temperature sensors that were deployed.

 

We steamed east to the Amukta pass mooring site.  The ROV was deployed but before we were able to attach the mooring the wind picked up to 50 knots and we were forced to seek anchorage for 2 days.  Once the weather subsided we returned to the Amukta mooring site.  After waiting 6-8 hours for the currents to drop below 1.5 knots we successfully deployed the ROV and recovered the Amukta Pass ADCP mooring.  Following the recovery an ADCP mooring was deployed at the same location.  The EdgeTech release was shipped to PMEL to determine why it failed. 

 

Following the mooring operations we steamed east to Dutch Harbor arriving at 0500 on Nov. 8^th. 

 

Mooring Locations:

02-AMP-3A   52 24.00 N    171 55.00 W    310 meters

02-SM-3A      52 07.996 N   172 25.008 W   164 meters