The Scandinavian Peninsula sits on a geological time bomb. Twenty thousand years ago, glacial ice covered the land, pressing it down beneath massive weight. As the ice melted, clay particles flowed into the salt water along the coast, settling into layers that became highly unstable. When the land slowly rose, these clay deposits emerged above sea level, now sitting between 220 and 300 meters above where the ancient ocean once reached. Freshwater washed away the salt that had held the clay together, leaving behind what geologists call quick clay: stable enough to build on, until disturbed. Then it flows like liquid.

The ground at Stenungsund had been telling its story for years. In 2013, engineering firm Norconsult surveyed the area and found the soil near the E6 to be sensitive. In 2020, the Vastra Gotaland County administrative board warned Stenungsund municipality that the land was unsuitable for development and that landslide risk existed. A professor at Chalmers University of Technology noted similarities to a 2006 landslide 50 kilometers north, caused by construction companies piling excavated material. After some modifications, authorities allowed development to proceed anyway.

The E6 stretches 3,056 kilometers from Kirkenes on Norway's Russian border to Trelleborg in southern Sweden. Twenty thousand vehicles traveled this section daily. After the landslide, that traffic had to go somewhere. Local road O650 through the village of Ucklum suddenly carried 15,000 vehicles per day on roads never designed for such loads. Long-haul trucks detoured through Trollhattan and Uddevalla. Residents of small villages watched heavy vehicles squeeze past their homes on narrow streets. On November 14th, the inevitable happened: a head-on collision between a bus and car on O650 sent a woman to the hospital by helicopter with serious injuries.

Engineers found a novel solution to prevent future instability. They placed a layer of crushed, recycled glass several meters deep beneath the rebuilt roadway, improving drainage and reducing the load on the sensitive clay below. On July 3rd, 2024, King Carl XVI Gustaf, Infrastructure Minister Andreas Carlson, and Transport Authority officials gathered for the reopening ceremony. Traffic resumed on July 5th. In Ucklum, over 100 residents celebrated with sausages and bouncy castles, relieved to have their village back. Three people face prosecution for gross public endangerment. The investigation revealed that construction companies had been paid to haul excavated material away from another project, then simply dumped it at the business park instead.