The Upper Engadin lakes are ready for the Engadin ski marathon next Sunday. A team of specialists of glaciologists and experienced trail preparers has examined the ice rinks on Lake Sils and Silvaplana using georadar and core drilling and is satisfied with the quality. The research focused on the quality of trails for the smooth running of Switzerland's largest popular run, which is expected to attract around 13,000 participants on Sunday.
In order to determine whether the layer of ice and snow on Lake Silser and Silvaplana meets the requirements of the Engadin Ski Marathon, a team of glaciologists from the University of Fribourg and the Academia Engiadina, together with experienced, local trail preparers, examined the trail in detail. A georadar mounted on a sled measured the ice sheet at several thousand measurement points between Maloja and Silvaplana. In addition, core samples were taken from the ice sheet and tested at several points. The experts' conclusion is positive.
Experts call it “sandwich ice cream”: Instead of a single, solid base layer, the ice of the Upper Engadin lakes in this very snowy winter consists of several layers, between which there is snow, slush and water. Although this does not significantly affect the overall load capacity of the ice sheet, if the top ceiling is damaged, water and slush could get onto the trail.
No wet feet for cross-country skiers
“After evaluating all the data, the scientists were able to give us the green light for next Sunday,” says OC President Ivo Damaso. “They thus confirmed the assessment of our experienced trail makers, who have known the lakes and the ice for decades.”
“The preparation of the two upper lakes with the lightweight skidoos has created a compact surface layer on which you can run the marathon on Sunday very well,” confirms Dr. Christine Levy from Academia Engiadina, who carried out and evaluated the investigations together with Dr. Matthias Huss from the University of Fribourg.
However, the transfer of the launch system from the lake to the shore in Maloja could not be avoided, explains start boss Nino Ganzoni: “The construction of the launch system on the lake would have put a heavy load on the top layer of ice at times. If thousands of participants had come out on foot on the lake before the start, it could have happened that the surface layer would not have withstood the high point loads, for example when access was narrower.”
Glaciologists welcome the relocation of the start area. After starting on land, runners enter the lake on skis instead of on foot. These distribute the weight of each runner over a much larger area than cross-country skiing boots do with their narrow soles.
“In addition to safety and fair conditions, all our efforts focus on a positive running experience for all participants,” summarizes Ivo Damaso. “If the top layer of ice were to break through somewhere, it wouldn't be life-threatening, but the runners would get their feet wet. Of course we don't want that.”
Keyword “sandwich ice cream”
If a lot of snow falls on a water surface after the ice sheet has formed, so-called “sandwich ice” can occur: The weight of the snow presses the ice sheet onto the water. This allows water to reach the ice from below, resulting in water-saturated slush. The overlying snow has an insulating effect, so that the slush sometimes does not freeze through for a long time, even when it is very cold.
To prepare the trails on Lake Silser and Lake Silvaplana, the much lighter skidoos with special tracking equipment were used instead of heavy snow groomers. This allowed the snowpack to be compressed at the top without stirring up the underlying slush. The trail across the three lakes was opened on February 11 and has already been race-tested. It is continuously being prepared so that it meets the high quality requirements of the Engadin Ski Marathon on Sunday.
For the construction of the launch site on the lake, slush would have had to freeze through, which could not have happened due to the weekly and sometimes heavy snowfalls since Christmas and the relatively mild temperatures.
gartmann.biz manages the media operations of the Engadin Ski Marathon.