Päijänne Water Tunnel

The Päijänne tunnel is a 1982 put into operation water line that supplies the Finnish capital Helsinki and its surroundings with drinking water from Lake Päijänne. With a length of 120 kilometers, it is the longest rock tunnel in the world.

The construction of the tunnel in 1972 decided, as the water quality of Vantaa, the Helsinki until then the drinking water was removed, was increasingly affected by industry and agriculture. In order to implement the project and to finance, the municipalities of the capital region created a common water supply company with the legal form of a stock corporation ( Pääkaupunkiseudun Vesi Oy). At their communities are now involved, which are supplied through the tunnel, next to Helsinki so Espoo, Vantaa, Porvoo, Järvenpää, Kerava, Tuusula, Sipoo, Hyvinkää, Kirkkonummi, Kauniainen and Nurmijärvi. Shareholder is also the state Altia Group.

The construction was started in 1973; after nine years of construction of the tunnel was put into operation in 1982. The total cost of construction in 1981 estimated at 530 million markka what today would correspond to about 190 million euros. The demolition of the tunnel was driven from the north. It begins in the community at the south end of Asikkala Päijännesees, only the second largest, but the deepest and richest lake volume of the country, at a depth of 25 meters. From there it extends to a depth of 30 to 100 meters below the earth's surface by the existing of hard granite and gneiss rock base to the southeast until Silvola Reservoir in the community Vantaa, immediately north of the city limits of Helsinki. From there the water is fed into the drinking water supply in the capital region. Here, the processing demand is low because the water of Päijänne has a very high quality and no adverse effects occur during transport through the tunnel by the solution resistance of the rock and the constant low temperatures.

Due to the natural gradient pumping equipment may not be needed, and at about halfway ( in Kalliomäki in the community Hausjärvi ) the flow is directed in the tunnel by a hydroelectric power plant, which feeds approximately 7.3 gigawatt hours annually in the Finnish electricity grid. Currently the tunnel is operated with a flow rate of about 3 m³ / s, but it is designed for a capacity of up to 10 m³ / s. In 2006, were passed through the tunnel to 104.5 million cubic meters of water.

From April to December 2008 were allowed to dry out the tunnel to make repairs in the southern section. During this time, the water capital was again temporarily removed the Vantaanjoki. As of 4 December of the year the floodgates were opened again; after two weeks the entire tunnel was ( for a total of about 2 million cubic meters ) completely flooded again, so that the water withdrawal could be resumed.

Swell

• Päijänne tunnelin korjausurakka saatiin päätökseen information page of the waterworks Helsinki to the tunnel
• Päijänne tunneli side of the water supply association of Helsinki capital region

• Tunnel
• Water supply construction
• Building in Uusimaa
• Built in the 1980s