Fuel threat lingers beneath buried Swiss mountain village

Aerial view of the Swiss mountain village of Blatten, which was buried by a massive landslide on May 28, 2025. Keystone / Laurent Gillieron

The Swiss mountain village of Blatten and the surrounding region face a new environmental threat. According to a study, around 150,000 litres of heating oil and fuel were buried beneath the rock, ice and debris that engulfed the village during a huge glacier collapse last year.

Given the pollution risk, authorities are planning long-term monitoring as preparations begin for Blatten’s reconstruction.

When the village was buried by a massive glacier collapse and landslide on May 28, 2025, it was not only homes, possessions and memories that were lost. Cars, heating oil tanks, machinery, batteries and refrigeration units also disappeared beneath the vast debris cone. Oil slicks quickly appeared on the lake that formed behind the debris in the valley.

A view of the massive landslide and debris field caused by the collapse of the Birch Glacier, which unleashed nine million cubic metres of rock, ice and debris into the Loetschental Valley. Keystone / Laurent Gillieron

A new environmental study, seen by Swiss public broadcaster SRF, shows that around 150,000 litres of heating oil and fuel were located within the buried area. It remains unclear how much leaked during the landslide and how much is still contained in intact fuel tanks.

Survey methodology

As part of the investigation, Blatten residents were sent questionnaires asking whether they had a heating oil tank and what substances were stored in their buildings at the time of the landslide.

A total of 220 questionnaires were completed, covering around 80% of the households and buildings buried by the disaster.

Alongside heating oil and fuel, respondents reported storing motor and transmission oils, batteries, refrigerators, paints, solvents, gas cylinders and ammunition.

Groundwater measurements

The study, commissioned by canton Valais, says oil hydrocarbons pose by far the greatest environmental threat. At the same time, the authors say it would be disproportionate to attempt a full recovery of these pollutants because their precise location is unknown.

About 90% of the village of Blatten, including 130 houses and the parish church, was buried. The debris also blocked the Lonza river to create a large lake. Keystone / Jean-Christophe Bott

The oil slicks that appeared on the lake suggest that some of the buried heating oil and fuel has already escaped. The authors warn there is a risk pollutants could enter the groundwater. However, measurements taken so far have not detected anything unusual.

They also note that water can penetrate the debris cone relatively easily. Monitoring of surface water and groundwater must therefore continue over the long term and be expanded. Valais authorities plan to extend monitoring across the entire Lötschental Valley in southern Switzerland, where Blatten is located.

Despite these uncertainties, the authorities believe reconstruction of the village remains feasible. “It would be disproportionate to say that we can no longer build here,” says Christine Genolet-Leubin, head of the Valais Department of the Environment.

View of ongoing reconstruction work at Blatten on August 18, 2026. Keystone / Cyril Zingaro

Updated hazard maps show where reconstruction is theoretically possible. Some of these areas are directly on the rubble that buried the old village. Construction methods will therefore be crucial, says Genolet-Leubin: “It’s a question of knowing how deep to excavate and how high you fill in the area.”

Some substances beneath the rubble could be released as gas or vapours. Authorities are therefore examining whether drainage systems will be needed in the areas where the village is to be rebuilt.

These concerns will not end when construction is complete. Some pollutants could continue to be released for decades.

“Some oil tanks are damaged and leaking, while others will corrode over time and the oil will leak out later,” says geologist and contaminated site expert Walter Wildi, who analysed the study for SRF. “Sooner or later, the heating oil will reach surface water or possibly groundwater.”

An image envisioning the future village of Blatten in 2030. Keystone / Laurent Gillieron

Reconstruction is underway

The necessary environmental measures must be integrated into the reconstruction work already under way. The first residents are expected to return to the new village of Blatten in 2029.

“If these measures are carried out in parallel, the timetable can be met,” says Matthias Bellwald, mayor of Blatten. But what the landslide left buried beneath the vast pile of rubble is likely to occupy residents and authorities for many years to come.

Translated from German, sub-edited by Simon Bradley/dos