The Lauttasaari water tower was a water tower in Lauttasaari, Helsinki, Finland from 1958 to 2015. Its volume was 4400 cubic metres,Asola, Ismo: Vesitorni – yhdyskunnan maamerkki. Helsinki: Suomen Rakennusinsinöörien Liitto RIL, 2003. . its height was 34 metres and the diameter of the upper water container was 42 metres.Uino, Ari: Lauttasaaren historiallisia vaiheita Julius Tallbergin ajasta 2000-luvulle. Helsinki: Lauttasaaren säätiö, 2005. .Elomaa, Ville: Lauttasaaren vesitorni. Helsinki: Lauttasaari-seura, 2009. . The water tower was decommissioned in 1996 and dismantled from October to November 2015.Malmberg, Lari: Lauttasaaren vesitorni katosi maisemasta, Helsingin Sanomat 16 November 2015.
General The Lauttasaari water tower was located on top of the Kotkavuori hill in Lauttasaari. It was built in 1958.Vuosikymmenten rakennukset Lauttasaaressa: Suomi 80 vuotta. Helsinki: Lauttasaari-seura, 1997. . As soon as the tower was completed it became a local landmark, and later a kind of symbol of Lauttasaari. The tower was the first mushroom-shaped water tower in Finland, and because of this, it was regarded as an architecturally and historically significant building.Lauttasaaren entisen vesitornin suojeleminen sekä korjaaminen yleisökäyttöön soveltuvaksi, city of Helsinki 5 October 2010. Accessed on 27 August 2013. Several other mushroom-shaped water towers have later been built in Finland.
History
Lauttasaari was connected to the Helsinki waterworks in 1936 by building a 150 millimetre pipe from Salmisaari. Water distribution to the apartments in Lauttasaari was started in the same year.Mustonen, Kauko; Pykälä, Kalevi (ed.): Lauttasaari: helmi Helsingin kruunussa. Helsinki: Lauttasaaren kustannus, 1976. At first the distribution network only reached Lauttasaarentie and its surroundings. As habitation grew denser the need of water increased considerably, and the capacity of the water network was increased in 1939, when a 200 millimetre pipe was built over the bay, next to the Lauttasaari bridge. From the 1950s, Lauttasaari started becoming a proper district, and the number of apartment buildings increased rapidly. In 1951 an additional 300 millimetre pipe was built. The water was taken from the Alppila water towers at the time.
In the 1950s large pressure differences in the Lauttasaari area waterworks became a problem. On days of large water consumption the pressure at the Lauttasaarentie pump station was not enough to bring water to the uppermost apartments in Vattuniemi and on Isokaari.Uino, Ari: Lauttasaaren historiallisia vaiheita Julius Tallbergin ajasta 2000-luvulle. Helsinki: Lauttasaaren säätiö, 2005. . The solution was to build a new water tower in the Lauttasaari area.
Planning In 1955, the Helsinki waterworks made a three-year plan for improving the water distribution in the districts newly annexed to Helsinki, which sought funding for expanding the water network in Lauttasaari and building a water tower. The plan had a proposal of 80 million markka for building a water tower. As well as the water network, the plan included a new water pipe from Salmisaari to Lauttasaari and excavating a tunnel needed by the water tower. The plan was accepted in spring 1957. The construction council started design of the water tower in autumn 1956.
The main designer for the tower was the architect Ossi Leppämäki. The construction plans for the tower were made by engineer Paavo Simula, who designed several different alternatives for a Lauttasaari water tower together with architects from the construction council. At the time, the usual type of water tower was a cylindrical container supported by pillars. As well as this option, an option for a conical container, new to Finland at the time, was investigated. These two options did not differ greatly in cost. The advantage for a conical container was smaller change to the level of the water, which would make the pressure in the pipe more stable than in a cylindrical container of the same size. An additional consideration was that a sleeker conical water tower would fit the Lauttasaari environment better. At the time, the only other conical water tower in Finland was a small tower of 250 cubical metresAsola, Ismo: Vesitorni – yhdyskunnan maamerkki. Helsinki: Suomen Rakennusinsinöörien Liitto RIL, 2003. . built in Halikko in 1951.
Location The waterworks suggest Myllykallio as the location for the new water tower to the construction bureau in April 1956, as it is the highest spot in Lauttasaari. After negotiations with the zoning department it was found that as the Lauttasaari church was being built at the end of Tallbergin puistotie, the water tower would have to be placed at least 70 metres north of the Myllykallio cliffs for zoning reasons, so it would have been constructed about seven metres lower than planned.
In summer 1956 the waterworks suggested Kotkavuori as the new location for the water tower. The proposal said that the effect the Lauttasaari church had on the zoning plan was that Kotkavuori was an equal option for the location as Myllykallio, as both had the same height of 27 metres from sea level in the spots reserved for the water tower. However, had the tower been located in Myllykallio, it would have cost 20 million markka more, as the location was further away from Salmisaari than Kotkavuori.
The Länsiväylä highway was being planned at the same time as the water tower. One of the three options for the location of the highway would have been at tunnel from Kotkavuori to Salmisaari, exactly at the location of the planned water tower. The tunnel plan was abandoned, as it would have required excavation at a depth of 50 metres, which would have made it over two kilometres long and very expensive to carry out. In the end, the Länsiväylä highway was built to pass Kotkavuori to the north.
Construction
The City Council of Helsinki approved the main design drawings for the Lauttasaari water tower in March 1958. A so-called partial work grant was reserved in the city budget for the construction of the water tower, the water pipe and the undersea pipe. The bidding contest for the construction of the water tower was originally won by Oy Concrete Ab with a price of 59.65 million markka and the contest for tensing the water container by A-Betoni Oy with 6.93 million markka. Concrete had to increase their offer later on. The board did not accept their requirement for the increased cost of the construction and rejected the offer. Construction of the water tower was given to YIT for a price of 64 million markka. The water technics connected to the water tower was implemented by the Helsinki waterworks, which also acted as construction supervisor.
During planning the construction, an alternative where the water container would be built on the ground and later lifted on top of the tower on a shaft was also considered. This alternative proved more expensive, and in the end wooden molds and scaffolding were used in the construction. The scaffolding was planned so that the wood would last as long as possible and could be reused.
Construction was started in early April 1958 and the tower was topped out on 26 September 1958. The casting of the tower took about 100 tonnes of iron and 450 cubic metres of special concrete mass. The tower was first filled with water in October, when it underwent a so-called tightness test. The tower was officially taken into use on 13 November 1958. After this, reinforcing elements were placed on the outer surface of the tower and construction was finally complete in February 1959.
Water pipes Undersea feeding pipe Before the construction of the water tower there had been three smaller water pipes from Salmisaari to Lauttasaari. After the new water tower was built, the old water pipes did not have enough capacity any more, so a decision was made to build a new 24-inch main feeding pipe.
The construction job of the new feeder pipe was given to YIT and it cost 11.7 million markka. Construction was started in July 1957 by building ground supports, at which the ends of the feeder pipe come out of the ground. New special water pipes brought from Germany were later lowered onto the seabed, floated onto their place with pontoons. The problems with water receiving and pressure differences in Lauttasaari went away when the new water tower was complete and the area got a new feeder pipe. The undersea pipes were renewed in 1971. The current main water pipe goes from Salmisaari to Lauttasaari via a multi-purpose tunnel completed in 2000.
Feeding of water to the water tower A new water tunnel from the seashore to the water tower was built in 1958. The construction company was Pyyhtiä & Karppinen Oy, and the tunnel cost 33.85 million markka.
The tunnel was built at Melojantie 2 up to the intersection between Koillisväylä and Klaarantie, at which it passes Kotkavuori and ends at Taivaanvuohentie. A separate branch pipe branches off from the feeder pipe in an undersea tunnel at Kotkavuori. A vertical underground shaft from the tunnel has been built at the same spot, with stairs leading up to the water tower. The Kotkavuori tunnel has entrances from Melojantie and at the Ekonomitalo buildings.
The water tower as a structure
The structure of the tower Kotkavuori is located 27 metres above sea level. The height of the water tower was 34 metres, so its roof was located 61 metres above sea level. The diameter of the water container was 42 metres at the widest point. On top of the shaft of the tower were 24 support beams at a 60-degree angle, with a 15.8 metre wide support ring on top of them. The purpose of the beams and ring was to support the water container and to ensure that the structure did not suffer damage due to changes in outdoor temperature or the shape of the concrete shell.
The total volume of the water container was 4530 cubic metres. It was divided into two parts, so that the container could be cleaned without interrupting the water supply. The volume of the inner container was 1080 cubic metres and that of the outer container was 3450 cubic metres. The height of the water surface in both containers was 57 metres above sea level, and the depth of the water in the containers was about seven metres. The water pipes were equipped with automatics that would cut off the water intake when the container was full.
The outer shell and support ring of the tower were pre-tensed concrete to prevent tensions and subsequent damage in the structure. The pre-tension was done in accordance to the Dywidag system, where the tension steel has a diameter of 26 mm. The Lauttasaari water tower was the first water tower in Finland to use pre-tensed concrete. The concrete walls were 25 cm thick. The outer walls and the support ring were cast without interruption, to prevent folds from appearing between the structures and to ensure water-tightness. The work was done in three shifts and took four days in total. The roof of the tower was built from copper.Manninen, Olli (ed.): Lauttasaari: kaupunki kaupungissa. Helsinki: Lauttasaari-seura – Drumsö-sällskapet & Helsingin kaupunginosayhdistysten liitto & Helsingin kaupunki, 1995. .
The thermal insulation was done by adding protective elements representing mushroom gills to the outer walls, with three-centimetre thick cork disks inside them. The roof was insulated with mineral wool, and the shaft and support beams were insulated with chalk-containing LECA brick. The eaves of the roof were heated with resistance wires to prevent falling icicles from forming.
The water in the Lauttasaari water tower was drawn from the Ilmala water tower. As well as Lauttasaari, the pressure area of the tower included Kaskisaari and Lehtisaari.
Later and proposed use