Päijänne tunnel

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Päijänne Tunnel
Päijännetunneli
Päijänne Tunnel Päijännetunneli
Course of the tunnel:
1. Asikkalanselkä inlet
2. Kalliomäki hydroelectric power station
3. Korpimäki pumping station
4. Silvola reservoir
use Water supply
place Southern Finland
length 119.6 km
Number of tubes 1
cross-section 16 m²
construction
building-costs 530 million Markka (≈190 million €)
start of building 1973
completion 1982
business
operator Helsingin Vesi
release 1982
location
Päijänne Tunnel (Finland)
Red pog.svg
Red pog.svg
Coordinates
Inlet in Päijännesee 61 ° 15 ′ 1 ″  N , 25 ° 31 ′ 24 ″  E
Silvolan reservoir 60 ° 16 ′ 37 "  N , 24 ° 53 ′ 59"  E

The Päijänne Tunnel is a water pipe that supplies the Finnish capital Helsinki and its surrounding area with drinking water from Lake Päijänne . At 119.6 kilometers, it is the longest rock tunnel in the world.

Construction and operation

The decision to build the tunnel was made in 1972 because the water quality of Vantaanjoki , from which Helsinki's drinking water was previously taken, was increasingly impaired by industry and agriculture. In order to implement and finance the project, the municipalities of the capital region founded a joint water supply company with the legal form of a stock corporation (Pääkaupunkiseudun Vesi Oy) . Today, the municipalities that are supplied by the tunnel are involved in it, in addition to Helsinki Espoo , Vantaa , Porvoo , Järvenpää , Kerava , Tuusula , Sipoo , Hyvinkää , Kirkkonummi , Kauniainen and Nurmijärvi . The state-owned Altia group is also a shareholder .

Construction began in 1973; After nine years of construction, the tunnel was put into operation in 1982. The total costs for the construction were given in 1981 at 530 million Markka , which today corresponds to about 190 million euros. The tunnel was being blown up from the north. It begins in the municipality of Asikkala at the southern end of the Päijännesees, only the second largest, but deepest and most voluminous lake in the country. The inlet in the lake is 250 m from the shore at a depth of 26 meters and therefore has a temperature of 0.5–11 ° C. From there it runs at a depth of 30 to 100 meters below the surface of the earth through the rock base consisting of hard granite and gneiss to the southeast to the Silvola Reservoir in the municipality of Vantaa , immediately north of the Helsinki city limits. From there the water is fed into the drinking water network of the capital region. The Pitkäkoski waterworks (Pitkäkosken vedenpuhdistuslaitos) needs little treatment , as the Päijänne's water is of very high quality and there are no impairments during transport through the tunnel due to the dissolution resistance of the rock and the constantly low temperatures.

Due to the natural gradient, pumping systems are not absolutely necessary. About halfway (in Kalliomäki in the municipality of Hausjärvi ) the underground running water is channeled through a hydropower plant , which feeds around 7.3 GWh into the Finnish power grid every year. The tunnel is currently operated with a flow rate of around 3 m³ / s, but it is designed for a capacity of up to 10 m³ / s and can be pumped to 20 m³ / sec. increase. In 2006, a total of 104.5 million cubic meters of water passed through the tunnel. World icon

The tunnel has a cross-section of 16 square meters. The profile is sufficient for a truck to drive through. It takes about nine days for the water to pass the length of the tunnel. At the current water usage rates, the sewage treatment plants take up around 3.1 m³ of water per second for drinking water treatment. The tunnel can therefore be used as an emergency water reserve if the water supply is interrupted.

From April to December 2008 the tunnel was allowed to fall dry in order to carry out repair work in the southern section. During this time, the water in the capital was taken from the Vantaanjoki again. From December 4th of that year the locks were opened again; After two weeks, the entire tunnel (with a total volume of around 2 million cubic meters) was completely flooded again, so that water could be withdrawn again.

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