25 people are no longer allowed in their homes What Lucerne is doing to protect people from the threat of rockfall

There is an acute risk of rockfall on the Gütsch near Lucerne. This was announced by the city. The authorities have taken immediate measures. 20 to 25 people are no longer allowed in their homes.

The rock at Gütsch in Lucerne is showing worrying signs of movement, forcing the city to take immediate action. On Friday morning, the city announced that immediate measures had been taken due to the acute risk of rockfall in the Gütsch area.

As those responsible announced at a media conference, thousands of tons of rock are unstable. The rock could fall at any time.

The rock is around 5500 cubic meters in size and weighs 13,000 tons. Residents in the danger zone were informed on Thursday evening and only have limited access to their homes, the city announced.

Construction work is not the cause

According to the city of Lucerne, the construction work at Schlössli Schönegg has nothing to do with the impending rockfall. The fissure found in the rock is much more a "child of the ice age".

Crevices and fissures like this one occur time and again in the Lucerne region, said geologist Beat Keller at the media briefing on Friday morning. They were formed during the ice age when the Reuss glacier receded. By luck, however, the fissure was discovered during the construction work in mid-August.

Assessments of the moving boulder showed that it reacts very sensitively to changes. Construction work at the Schlössli was therefore stopped. An automated alarm system was installed as an immediate measure.

On September 12, new analyses showed that the rock mass could detach without warning. The Gütschweg, the SBB portal of the Gütsch tunnel, parking lots on the valley side and the Schlössli Schönegg are located in the immediate danger zone. Although the latter is not in danger of collapsing, it could be damaged, according to the authorities.

20 to 25 people in the apartment at risk

The emergency shelter and four residential buildings are also affected. However, only the apartments on the mountain side are affected, as Keller emphasized. The city informed the majority of residents about the danger at an event on Thursday evening. The residents who could not be reached are to be informed later today. They will be banned from staying in their homes permanently. According to Keller, it is unclear exactly how many people are affected. It is estimated to be between 20 and 25 people.

As an immediate measure, steel palisades will be flown in by helicopter on Friday afternoon, according to Beda Müller, Head of Urban Drainage and Natural Hazards at the City of Lucerne. These are intended to reduce the danger and mitigate the potential damage in the event of an incident.

The long-term rock stabilization measures will start at the end of September and are expected to last until the end of the year, said Keller. Specifically, the rock section at risk of falling is to be secured with anchored concrete bars and shotcrete walls. It will also be covered with a ground net. The costs for this amount to around 1.6 million francs.

Sirens and warning lights installed

As the implementation of the measures will take some time, those responsible have drawn up an alarm concept in the event of an incident. A monitoring system measures movements of the rock mass. If these reach a critical level, the system triggers an alarm. Sirens and warning lights alert local residents to the danger.

The SBB railroad line near the Gütsch tunnel is also automatically closed in the event of an incident. This is the main access route to Lucerne railroad station. On request, the media office of the Federal Railways explained: "SBB is monitoring the situation closely and is in close contact with the responsible authorities in the city of Lucerne". According to SBB, alternative concepts exist for Lucerne station, which could be adapted to the situation and implemented if necessary.

Most recently, there was a risk of rockfall in the Gütsch area near Sagenmattquartier in January 2016. A 20-metre-high section of rock had moved around 1.5 millimetres within a few hours, according to reports at the time. There was a risk that a boulder could break loose and fall onto the settlement. 125 residents of a block of flats were evacuated as a precaution. According to Keller, however, the situation back then had nothing to do with the situation today.