For safer salvage.

An accurate method for rescuing objects from a waterbed. Frozen sediments provide a shield against contamination and a stable embedding for fragile goods.

Through the FriGeo method of underwater freezing potentially hazardous objects such as leaking containers or dumped munitions can be safely salvaged. By the same method freeze dredging can also be used to rescue objects of archaeological, historical or forensic interest from an underwater location.

Freeze Dredging is a method highly suited for the rescue of objects that have been buried in sediments. Frozen sediments support the sunken object during lifting and work as a shield against the potential redistribution of contaminants. Dumped munitions and objects of historical interest can be safely salvaged through Freeze Dredging and the unique precision of the method also makes it suitable for underwater forensic investigations.

A major advantage of Freeze Dredging is the ability to preserve the positioning of an object on the seabed by freezing the surrounding sediments before lifting.

The technique provided by FriGeo can be remotely operated, thus making it ideal for stabilizing and handling hazardous materials. The method can also be used to rescue objects from very deep waters. By freezing sediments it is possible to increase slope stability and prevent the spreading of contaminated or radioactive sediments during the salvage operation.

Case study: The Catalina Affair

In June 1952 a Swedish military DC-3 flying over the Baltic Sea on a secret mission disappeared east of the Island of Gotland. Three days later a Catalina aircraft searching for the DC-3 was shot down by Soviet warplanes. This was the start of the Catalina Affair – a sensitive chapter in the history of the Cold War.

More than fifty years later Swedish deep-sea explorers found the wreckage of the lost DC-3 in international waters east of Gotska Sandön, an island 120 kilometres east of the Swedish coastline. After the aircraft had been salvaged the method of Freeze Dredging was used by the Swedish Navy to retrieve small objects of important forensic value from the seafloor close to the aircraft.

The dredging work was conducted by the Swedish submarine rescue vessel HMS Belos which carried a freezing plant onboard. The wreck of the DC-3 lay at a staggering depth of 125m but through advanced technology it was possible to freeze a portion of the uppermost layers of the bottom sediments into solid blocks. During the salvage operation around 200m3 of sediment were lifted. After uptake the material was kept frozen until a careful examination could be made.

The precise technique enabled forensic experts to travel back in time and search for clues as to what really happened on that fatal day in 1952. While the Cold War is part of the past, Freeze Dredging, as a means of rescuing objects from underwater sediments, is part of the future.