The Päijänne Water Tunnel (, ) is a water tunnel located in Southern Finland. At , it is the second-longest

tunnel A tunnel is an underground passageway, dug through surrounding soil, earth or rock, and enclosed except for the entrance and exit, commonly at each end. A pipeline is not a tunnel, though some recent tunnels have used immersed tube cons ...

in the world, running at a depth of in the bedrock. The purpose of the tunnel is to provide fresh water for the over one million people of the Greater Helsinki area, including the cities of

Helsinki Helsinki ( or ; ; sv, Helsingfors, ) is the capital, primate, and most populous city of Finland. Located on the shore of the Gulf of Finland, it is the seat of the region of Uusimaa in southern Finland, and has a population of . The city ...

Espoo Espoo (, ; sv, Esbo) is a city and municipality in the region of Uusimaa in the Republic of Finland. It is located on the northern shore of the Gulf of Finland, bordering the cities of Helsinki, Vantaa, Kirkkonummi, Vihti and Nurmijärvi ...

Vantaa Vantaa (; sv, Vanda, ) is a city and municipality in Finland. It is part of the inner core of the Finnish Capital Region along with Helsinki, Espoo, and Kauniainen. With a population of (), Vantaa is the fourth most populated city in Finland ...

Hyvinkää Hyvinkää (; sv, Hyvinge, ) is a city and municipality of Finland. It is located in the Uusimaa region, approximately north of the capital Helsinki. The city was chartered in 1960. The population of Hyvinkää is (). Its neighboring municipal ...

Järvenpää Järvenpää (; sv, Träskända) is a town and municipality in Finland. It is located on the Helsinki–Riihimäki railway track in Uusimaa region, some north of Helsinki. Neighbouring municipalities are Tuusula, Sipoo and Mäntsälä. People ...

, Kerava,

Kauniainen Kauniainen (; sv, Grankulla) is a small town and a municipality of inhabitants () in the Helsinki Metropolitan Area, Finland. It is surrounded and enclaved by the City of Espoo, in the Capital Region of Greater Helsinki. Kauniainen was founde ...

Kirkkonummi Kirkkonummi (; sv, Kyrkslätt, , Sweden ) is a municipality of inhabitants () in southern Finland. The literal meaning of the words "''Kirkkonummi''" and "''Kyrkslätt''" in English is "church heath". Geography The municipality is located just ...

Sipoo Sipoo (; sv, Sibbo) is a municipality of Finland. It is part of the Helsinki metropolitan area. The municipality has a population of () and covers an area of of which is water. The population density is . The administrative center of the munic ...

and

Tuusula Tuusula (; sv, Tusby ) is a municipality of Finland. It belongs to the Helsinki sub-region of the Uusimaa region. The municipality has a population of () and is by far the third largest municipality in Finland after Nurmijärvi and Kirkkonummi ...

. The former Porvoo Rural Municipality, now merged with the municipality of

Porvoo Porvoo (; sv, Borgå ; la, Borgoa) is a city and a municipality in the Uusimaa region of Finland, situated on the southern coast about east of the city border of Helsinki and about from the city centre. Porvoo was one of the six medieval to ...

, also took part in the building of the scheme but has never drawn water from it for domestic use. The tunnel starts at Asikkalanselkä in

Lake Päijänne Lake Päijänne () is the second largest lake in Finland (). The lake drains into the Gulf of Finland via the Kymi River. The major islands are from north to south Vuoritsalo, Muuratsalo, Onkisalo, Judinsalo, Edessalo, Taivassalo, Haukkasalo, ...

, the second-largest lake in Finland with an area of . From there, the tunnel slopes slightly downhill allowing water to flow naturally with gravity. Water from the southern portion of Lake Päijänne is of good quality at the tunnel intake, and usually drinkable without processing. The tunnel ends at the Silvola

reservoir A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including contro ...

in Vantaa. From the reservoir, water is pumped to water treatment plants in Pitkäkoski and

Vanhakaupunki Vanhakaupunki ( sv, Gammelstaden) is a neighbourhood of the city of Helsinki, Finland, to the north of Toukola. It is also the name of a district of the city, which contains the neighbourhood and its surroundings. The name (meaning "old town") co ...

. The construction of the tunnel started in 1972 and was completed in 1982, at a cost of approximately €200 million (adjusted for inflation). In 1999 and 2001, portions of the tunnel required repair due to rock falls. In 2008, the tunnel underwent an extensive renovation. The southern part of the tunnel was reinforced in order to prevent

cave-in A cave-in is a collapse of a geologic formation, mine or structure which may occur during mining, tunneling, or steep-walled excavation such as trenching. Geologic structures prone to spontaneous cave-ins include alvar, tsingy and other limes ...

s. During the renovation, the Vantaa River was used as an alternative water supply for the Greater Helsinki area. The tunnel has a cross section of , wide enough for a truck to pass through, enabling a water flow of per second. It takes approximately nine days for the water to traverse the length of the tunnel. At current water usage rates, treatment plants take water at a rate of about per second for drinking water processing. __NOTOC__

Gallery

Image:Päijänne.png, Location of

Finland Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of B ...

. image:Aurinkovuori15112014.JPG, Asikkalanselkä in Lake Päijänne, where the tunnel starts. Image:Silvolan tekojärvi 1.jpg, Silvola reservoir, where the tunnel ends. Image:Silvolan tekojärvi.jpg, Aerial view of Silvola reservoir.

References

External links

Finnish Tunnelling Association, Päijänne Water TunnelPääkaupunkiseudun Vesi Oy
{{DEFAULTSORT:Paijanne Water Tunnel Water tunnels Water supply and sanitation in Finland Tunnels in Finland Tunnels completed in 1982 Lake Päijänne 1982 establishments in Finland

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See also

References

External links