Lahti landmark enhanced for World Championships

The renovation of the large hill and surrounding structures in the Lahti Sports Centre will be complete by December 2015. Ski jumpers will then also be able to jump in the summer, which was not possible for a long time due to the unevenness of the landing slope.

Completed in 1971 at the Lahti Sports Centre, the 130-metre hill is the higher of the two adjacent landmarks of the city. The hill has special symbolic value for Lahti residents and other Finns, as world-class ski jumping competitions have been arranged at the Lahti Ski Games since 1923. From the point of view of builders, renovating the large hill is extremely demanding – both technically and in terms of occupational safety.

Lahti Sport Center

"There are demanding lifts on a steep slope every day, at their highest up to some 70 metres," says Jari Kautonen, Safety Manager at Lemminkäinen.

Kautonen emphasises the fixed connection between safety and the technical management of work. According to him, keeping the site tidy is an equally significant factor in safety – and quality.

"We never look at safety as a separate issue. This is the only way to reach a zero level of accidents. This is a realistic aim for us, also at the Lahti large hill site," Kautonen says.

One of the key safety principles is that no one is allowed to be under lifting at any time. This requires careful planning of work, as there is a lot of lifting and the schedule of the site is quite tight.

"Inducting everyone working at the site or visiting it into the basics of safety is an essential part of safety work," Kautonen reminds.

Access control is also part of site safety, as this makes it possible to prevent unauthorised persons from accessing the site at the gate.

"The same system also serves the objectives laid down by the Act on the Contractor's Obligations and Liability when Work is Contracted Out. No company that does not fulfil its statutory obligations may bring employees to this site," says Site Manager Antti Marttinen.

Six-month effort

The six-month project that began in early June started with the demolition of the old wooden structures of the landing slope. The demolition was necessary to be able to reinforce the soil structure, which had depressed up to half a metre at places and was prone to landslides, or sagging of soil, during rain.

"The pitch of the landing slope is 38 degrees, which is at the extreme limit in terms of the stability of the soil structure without reinforcement measures. The reinforcement method used here is a steel Titan pile encased with concrete, installed in 12 rows throughout the length of the landing slope," Marttinen says.

Thanks to Titan piling, the slides that have occasionally taken place will be in control. The Titan-piled embankment will be covered with filter cloth to prevent a thunderstorm with heavy rain during the installation from spoiling the final result. The final surface structure will be a wooden deck installed by our subcontractor APR-Rakennustyö Oy.

The concrete-structure in-run will get a new ice track made of prefabricated elements with a more effective cooling system. With it, the tracks can be frozen economically in conditions up to +10°C. The new technology is also energy-efficient as, unlike before, the cooling will only target the track, not the entire element.

"Our aim is to have both the landing slope and the in-run as well as the skiing bridge between the Ski Museum and the stadium complete by October. The rest of the time will be used for demolishing and rebuilding the judges' tower," Marttinen says.

The new concrete-structure skiing bridge will be 54 metres long and 18 metres wide. The entire 700-cubic-metre deck casting of the bridge will be carried out as a single effort in early autumn, after which the structure will be post-tensioned.