Verzasca Dam
| Contra Dam | |
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Contra Dam
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 Location of Contra Dam in Switzerland
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| Official name | Contra Dam |
| Location | Ticino, Switzerland |
| Coordinates | 46°11′48″N 8°50′52″E / 46.19667°N 8.84778°ECoordinates: 46°11′48″N 8°50′52″E / 46.19667°N 8.84778°E |
| Construction began | 1961 |
| Opening date | 1965 |
| Owner(s) | Verzasca SA |
| Dam and spillways | |
| Type of dam | Arch dam |
| Impounds | Verzasca River |
| Height | 220 m (720 ft) |
| Length | 380 m (1,250 ft) |
| Width (crest) | 7 m (23 ft) |
| Width (base) | 25 m (82 ft) |
| Dam volume | 660,000 m3 (23,000,000 cu ft) |
| Spillway type | Service, uncontrolled overflow |
| Spillway capacity | 1,300 m3/s (46,000 cu ft/s) |
| Reservoir | |
| Creates | Lago di Vogorno |
| Total capacity | 105,000,000 m3 (85,000 acre·ft) |
| Catchment area | 230 km2 (89 sq mi) |
| Surface area | 160 ha (400 acres) |
| Power station | |
| Hydraulic head | 277 m (909 ft) (Max) |
| Turbines | 3 x 35 MW Francis-type |
| Installed capacity | 105 MW |
| Annual generation | 234 GWh |
The Contra Dam, commonly known as the Verzasca Dam and the Locarno Dam, is an arch dam on the Verzasca River in the Val Verzasca of Ticino, Switzerland. The dam creates Lago di Vogorno 2 km (1.2 mi) upstream of Lake Maggiore and supports the 105 MW Verzasca Hydroelectric Power Station hydroelectric power station. It was constructed between 1961 and 1965 and starting shortly after its reservoir was filled, a series of earthquakes related to its water load occurred until 1971. The dam is owned and operated by Verzasca SA and is the fourth tallest in Switzerland.
The dam became a popular bungee jumping venue after a James Bond stuntman jumped off it in the opening scene of the 1995 film GoldenEye; a stunt voted as the best movie stunt of all time in a 2002 Sky Movies poll.
On May 6, 1960, Verzasca SA was formed to construct the dam as the center-piece of the Verzasca Hydroelectric Complex. Construction in the dam began in 1961. The dam was designed and its construction supervised by Lombardi & Gellaro Ltd. Because the Contra Dam is at a lower elevation compared to other Swiss dams, warmer weather allowed construction to be carried out year-round. To divert the river and prepare a dry work-site for the dam, cofferdams were constructed, one of which redirected the river through a diversion tunnel with a 200 m3/s (7,100 cu ft/s) capacity. As the river can have flows much higher than the tunnel's capacity, this was accepted as a risk by engineers. Excavation of the right side of the dam had to be expanded due to unforeseen weathered rock and designs were altered within 15 days.
Concrete pouring and placement occurred for 18 months, of which the maximum poured in a day was 3,100 m3 (110,000 cu ft) and in a month, 55,000 m3 (1,900,000 cu ft). The aggregate for the concrete was obtained from a quarry near the construction site. The high-quality and strength gneiss-rock was ground in a rotary crusher and prepared in the concrete mixture. To facilitate the contraction and settling of the concrete in the dam, it was cooled with a series of steel pipes that ran throughout the mass of concrete, with the exception of the top 30 m (98 ft) of the dam. A grout curtain was placed around and below the dam as well to prevent leakage, which consumed a large amount of cement. In August 1964, the reservoir began to fill and in September 1965, the reservoir was full and the dam completed.
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