On the night of Saturday, September 23, the ground collapses down towards the E6 in Stenungsund. Buildings are destroyed, cars get stuck and the road that is so important for the region is shattered.

On a hill next to the motorway, the construction of a business park for industry, offices and warehouses is underway.

Together with two experts in geotechnics, SVT has gone through older versions of documents and maps that governed the construction – and it appears that the risk of landslides was greatest in the area closest to the E6.

Risks of landslides are detected – and eliminated

The sensitivity of the ground near the E6 motorway was discovered as early as 2013, when the company Norconsult measured the strength of several locations in the area. But the information is being deleted from the documents that will govern the construction.

According to a previous plan, the area closest to the E6 was to be developed, but the plans were scrapped. The area is then replanned as natural land – but at the same time, all calculations of how sensitive the land is are erased.

Stenungsund Municipality later approved both a raising of the ground level and the construction of an approximately six-metre-high slope – next to the sensitive ground. But on the slope, no measurements of the risk of landslides are ever made.

"It's surprising that they don't check it. Given that it is the only direction that has an infrastructure of importance, the E6 is still the E6," says Mats Karlsson, researcher in geotechnical engineering at Chalmers University of Technology, who also does assignments on geotechnical issues for a consulting firm.

The municipality confirms

Stenungsund Municipality confirms that the calculations of the risks were removed in connection with the fact that the area closest to the E6 would not be built on and that no new measurements were made.

"In retrospect, you should have measured everywhere, but you can always be wise with hindsight," says Olof Lundberg (S), chairman of the municipal board in Stenungsund.

The incident is being investigated by both the Swedish Accident Investigation Board and the police.

Norconsult declined to be interviewed.

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See the mayor's answer to why the landslide measurements closest to the E6 were erased from the municipality's documents – and why a high slope was approved without new measurements? Photo: Lars Wiklund/SVT