L’ Aber Wrec'h, France 2005 Ocean Exploration:

The survey of the sunken Athabaskan had three primary objectives; 1) the creation of a sonar mosaic of the forward half of the ship and 2) the location and mosaicing of the missing stern section of the vessel, 3) document the site(s) comprehensively enough to assist in the planning of a future dive mission to the site. The wreck site is approximately 10 kilometers from the village of Aber Wrec’h, France. Aber Wrec’h is a picturesque sea-side village whose harbor was well suited to our small operation.

The site had been visited by divers in 2003, but due to on-site conditions (depth – 87meters, limited visibility and ocean currents) divers could spend very little time on the bottom. Divers were able to confirm the wreck was the Athabaskan, however many more questions remained

Project Operations
Considering the remote nature of the site, we had determined it would not be cost effective to mobilize Aurora survey gear to the site and  we selected a survey company with a highly mobile (truck transportable) survey craft configured with a hull mounted multi-beam sonar and integrated GPS navigation. It quickly became apparent, however, that tidal currents would play an important role in governing our survey operations.  Tidal currents in excess of 9kts were experienced on site and the tidal range in the harbor was about 24 feet.

Finds
The first day of operations was very successful as the winds and seas in the area were quite mild and the survey vessel was capable of steering courses and speeds best suited to collecting sonar mosaic data. The wreck was quickly re-located and a composite record was compiled of the bow section of the ship. Additionally, a substantial area was surveyed adjacent to the location of the bow section in the hopes of locating the stern of the wreck. Official records of the sinking give few clues on where the stern may have broken free and sank relative to the bow and we were unsuccessful in locating the stern section or any major debris from it.

In the succeeding two days the weather and onsite conditions deteriorated and it became more difficult to operate at the site. Additionally, in the 90 meter water depths found at the site presented a significant challenge to the multi-beam survey sonar. Although the data collected was sufficient to create a mosaic of the wreck, the resolution suffered and the many details about the wreck and locating the stern section were unobtainable.

The decision was made to bring in a towed side scan sonar in hopes of improving the resolution of the remote sensing effort. A side scan sonar and operator arrived on the last day the availability of the survey vessel. Although the side-scan was the right tool for the job, the conditions on site (Spring Tides) and local wind conditions conspired to make the deployment of the tow fish to just above the seafloor impossible and we were unable to improve on the multi-beam data already collected.