At 15.45 on the 10th of November, enormous masses of clay were set in motion on Asak farm, 35 kilometers outside Oslo. The initial landslide pit was approximately 200 by 150 metres. Six men were working in the area hit by the disaster. Three of them managed to escape, while the other three, sadly, were buried in the rapidly moving masses. The masses of fluid clay had moved more than a kilometre down the fields, crossing a road and continuing along a small river.

NGI's natural hazard experts were immediately called to duty. Their first tasks were to assess the level of danger for surrounding areas and to assist in the search and rescue operation. It turned out to be a challenging and lengthy assignment.

Håkon Heyerdahl and Øyvind Høydal from NGI arrived at the landslide at 17:00. By then, darkness had already fallen.  A large-scale operation had been established by the police. Two helicopters had arrived, and search teams were preparing to look for survivors. NGI's men took a helicopter reconnaissance of the affected area.

Helicopter was used to get an overview of the disaster. Photo: Lisbeth Andresen

Safe search for survivors

"The first and most important task was to get an overview of the landslide area, and to assess the risk to neighbouring areas and houses. The Asak farm buildings and the nearby conference hotel were considered not to be at immediate risk. However, one residential building closer to the landslide was evacuated," says Håkon Heyerdahl, senior engineer at NGI's section for Risk, Landslide geotechnics and Climate adaption.

In this initial phase, NGI advised the police on how the search operations could be conducted with as little risk as possible for search crew, rescue dogs and excavation equipment.

Enormous masses of clay were set in motion. Photo: Tom Gustavsen

"Any human presence in the disaster area was considered extremely dangerous. Large areas had been covered in depositions of stirred, fluid quick clay, several meters deep. Having finished the first search phase, we realized that all hopes of finding survivors were dwindling. Safety for the rescue team was therefore top priority," says Heyerdahl.

The assignment lasted several weeks and was finished just before Christmas. Only one of the bodies was recovered.

The Sørum landslide was the first fatal quick clay incident in Norway since the Finneidfjord landslide in Northern Norway in 1996, which claimed four lives. However, there have been several other incidents where human lives were at risk.

Contributes to society

The Sørum landslide is just one example of the many projects NGI managed in 2016. The common factor for all our research and development work is our contribution to society and businesses.

Whether it be a new offshore wind park, bridge and road construction, or safeguarding of infrastructure from landslides and avalanches, NGI is there to develop and deliver beneficial solutions. Through our extensive research and expert advice, NGI helps to ensure that we can all live, build and travel on safe ground.

In the NGI Magazine On safe ground 2016 you can read more about the fatal quick clay landslide and other examples of how NGI solved a variety of challenges in several countries during the last year.