Ringedals Dam
| Ringedals Dam | |
|---|---|
Ringedals dam, Skjeggedal Pumping Station and Tysso II
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| Location | Ringedalsvatnet, Norway |
| Construction began | 1909 |
| Opening date | 1918 |
| Dam and spillways | |
| Type of dam | Gravity dam |
| Height | 33 metres (108 ft) |
| Length | 521 metres (1,709 ft) |
| Width (crest) | 4 metres (13 ft) |
| Width (base) | 21.5 metres (71 ft) |
| Reservoir | |
| Total capacity | 426 million m3 |
Ringedals Dam is a gravity dam by Ringedalsvatnet at Tyssedal in Odda municipality in the county of Hordaland, Norway. The dam was built in stages between 1909 and 1918 in connection with the hydroelectric power plant in Tyssedal and the factories in Odda. When the dam was completed in 1918 it was one of Europe’s largest gravity dams with a reservoir capacity of 222 million m3. The dam is built in Cyclopean concrete with 30% large-sized stones (plums) and dressed on both sides with approximately 20,000 m² of hand-cut granite stone, the largest of its kind in Norway. The dam is crowned by the date and initials of managing director Ragnvald Blakstad and topped with merlons in Neo-Romanesque style.
Ringedalsvatnet is today the reservoir of Oksla Hydroelectric Power Plant at Sørfjorden. The reservoir has a capacity of 426 million m³ and the power station is every year producing approximately 900 GWh.
In the bedrock under the Ringedals Dam there are three tunnels. In 1903, three years before AS Tyssefaldene was established, the first underwater tunnel that pierced into the natural lake reservoir was made by the drill and blast method. The transfer tunnel was 100 meters long and named after the owner, Bruuns tunnel. The tunnel could lower the Ringedalsvatnet 10 meters, down to 428 meters above sea level. Later Bruuns Tunnel was made bigger and today a penstock pipe lifts the water from Skjeggedal Pumping Station to Ringedalsvatnet (pumped-storage hydroelectricity).
When the first stage of Tyssedal Power Station was built from 1906 to 1908, there was no need for a dam and reservoir. Ringedalsvatnet could be regulated 16 meters by a new transfer tunnel and valves. In 1907 a 160-meter-long tunnel with a cross section of 6.5–7 m² was cut out of the bedrock. The tunnel is named after the responsible engineer, Thorvald Schult (1874-1937). The valve house is also called "Schultsynken". The last tunnel under the dam is called Brekkes tunnel and is not in use.
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