|Data on the structure|
|Lock type:||Arch dam|
|Height of the barrier structure :||220 m|
|Height above the river bed :||204 m|
|Height of the structure crown:|
|Building volume:||660,000 m³|
|Crown length:||380 m|
|Crown width:||7 m|
|Base width:||25 m|
|Power plant output:||105 MW|
|Operator:||Verzasca SA officina Idroelettrica|
|Data on the reservoir|
|Water surface||1.68 km²|
|Reservoir length||5.5 km|
|Total storage space :||105 million m³|
|Catchment area||233 km²|
|Design flood :||1 300 m³ / s|
The Lago di Vogorno is unused for electricity generation reservoir in the Swiss canton of Ticino . It is located at the exit of the Valle Verzasca (Verzasca Valley) near the municipality of Gordola . Two kilometers downstream, the Verzasca flows into Lake Maggiore . The lake is dammed up by the Contra Dam (also known as the Verzasca Dam), which was completed in 1965 . With its height of 220 meters, it is the fourth highest dam in Switzerland after those of the Lac des Dix , Lac de Mauvoisin and Lago di Luzzone reservoirs .
The dam is an arch dam of concrete m with a height of 220 meters and a length of crown 380 for sale. The barrier is 25 meters thick at the foundation base and 7 meters thick at the crown. It contains 660000 m³ of concrete and has a surface of 44500 m². The dam is slender and has an elliptically shaped horizontal curve. The horizontal curvature decreases from the center towards the foundation base, while the vertical curvature increases from the crown to the base. The thickness is constant except for the part where the dam meets the foundation to reduce pressure on the rock. This carries up to 70 kg / cm². The thickness increases vertically from the crown downwards and describes a slight curve from the center towards the crown. This will reduce the tension if the reservoir is not full. The bottom outlet of the dam consists of two pipes. One leads into a tunnel that diverted the water during the construction of the dam, the other is at the foot of the dam and leads into the river.
The dam has two flood reliefs with a capacity of up to 1300 m³ / s. This is especially necessary because the water flow of the Verzasca is subject to very strong seasonal fluctuations and can be up to 1000 m³ / s. Each flood relief has six weirs , each 12 meters wide. From each opening the water flows to a jump, which hurls the water into the middle of the valley 200 meters below. The flood reliefs were later rebuilt in order to improve functionality by enlarging the pillars and adding additional lateral deflectors.
Up to 50 m³ / s of reservoir water are fed from the reservoir with a storage target of 470 meters above sea level to three vertical 35 MW Francis turbines and one horizontal 4.3 MW Pelton turbine , which are housed in a cavern power station at 193 meters above sea level. From there it is led through a 1.9 km long tunnel into Lake Maggiore . The annual electricity generation is approx. 230 GWh .
Verzasca SA is the builder and owner of the power plant. It has an 80-year license to operate the power plant until 2046. Two thirds of the shareholders are the city of Lugano and one third of the canton of Ticino.
Verzasca SA was founded on May 6, 1960 to build the Contra Dam as the heart of the Verzasca hydroelectric complex. Construction began in 1961. Planning and construction supervision was carried out by Lombardi & Gellaro Ltd. Because the Contra dam is relatively low compared to other dams in Switzerland, the construction work could be carried out all year round. In order to divert the river and drain the construction site, cofferdams were built and the river diverted through a tunnel that could hold 200 m³ / s. Since the river can carry significantly more water than the tunnel, this was a risk for the engineers.
The concrete work lasted 19 months, with up to 3,100 m³ of concrete being processed per day. The aggregate for the concrete was extracted from a nearby quarry . The gneiss was crushed in a crusher and mixed with the concrete . To make it easier for the concrete to harden, it was cooled using steel pipes that ran through the concrete. It was only waived for the top 30 meters of the dam. A sealing veil was also placed under and around the dam. In August 1964, the reservoir began to be filled. Part of the village of Vogorno was flooded in the summer of 1965; the houses were rebuilt on the slope above the lake. In September 1965 the reservoir was full and construction was completed.
Civil engineer Giovanni Lombardi describes the lock as one of his finest, mainly because of its slimness and "clean design". As less concrete was used, costs were also reduced.
During the initial filling of the reservoir, seismic activity occurred repeatedly . The earthquakes started in May 1965, and the greatest disturbances occurred between October and November when the reservoir was full. The epicentres were on two faults near the dam. Up to 25 impacts per day were measured. The tremors subsided when the reservoir was emptied and no damage was found to the dam. After refilling, the shocks decreased and it was assumed that an equilibrium was reached that did not react to different water levels. After 1971 no more seismic activity was observed in the area of the dam.
Greater awareness gained the dam through the opening scene of the seventeenth James Bond -Streifens Goldeneye (1995): it shows Bond - played by Pierce Brosnan - the dam jumping, which as a double for the fictional chemical weapons factory Arkhangelsk in the Soviet Union during the Cold War served. In fact, the bungee jump was performed by British stuntman Wayne Michaels and was rated by Sky Movies as the best film stunt of all time. Shortly after Goldeneye appeared , the dam's company, Verzasca SA, began lending it to a bungee jump company as a bungee jumping facility. Since then, the dam has been a popular destination for bungee jumpers. According to the company, more than 10,000 visitors have already taken advantage of this offer.
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