El Cajón Dam (Honduras)
El Cajón Dam | |
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The El Cajón Dam, officially known as Central Hidroeléctrica Francisco Morazán, is a
Location
El Cajón Dam is located 180 km (112 mi) from Tegucigalpa, the country's capital, and 80 km (50 mi) from San Pedro Sula, the main Honduran industrial city.
Construction
Harza Engineering of Chicago, Illinois, United States, began site investigation in the 1960s with initial construction beginning June 15, 1980. A multinational team of designers, builders and engineers included members from Italy, Germany, and Switzerland. Engineering design was developed by Motor Columbus [now Colenco] of Switzerland. Italian companies were responsible for the construction of the underground machine room, while Italian and German companies were responsible for dam construction and ancillary works. Upon completion the dam became the largest piece of infrastructure in Honduras, requiring over half a million cubic meters of concrete to construct. Due to its double-curved arch design, this dam is relatively thin compared to say, Hoover Dam (gravity dam design) that spans a similar valley profile yet required roughly four times as much concrete.
Design
Reservoir
El Cajón Dam bridge | |
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Coordinates | 15°02′N 87°45′W / 15.03°N 87.75°W |
Characteristics | |
Width | 7 m (23 ft) |
Location | |
The reservoir created by El Cajón spans 94 km2 with a maximum capacity of around 5,700 million m³.[3] The reservoir displaced approximately 4,700 people.[4] While the main purpose of the reservoir is for powering El Cajón's turbines, flood control is another major benefit. Before completion of the dam, yearly flooding in the Sula valley seriously disrupted commerce for the people of Honduras. Now during the rainy season the reservoir has the ability to retain a layer of water ten meters high, and then discharge it slowly to prevent disastrous flooding. Agriculture has also benefited. Historically, during the dry season the Comayagua's flow dropped significantly to around 20 m3/s, the dam now provides year-round flow of approximately 100 m3/s, which has had a significant economic impact for the region.[3]
Power output
Eight large vertical axis
Instrumentation
Initially, electrical monitoring devices commonly used in modern dams were installed, but due to high sulphur content in the surrounding rock and water, all of the devices corroded and failed. With the exception of portable monitoring equipment, El Cajón now relies entirely on mechanical devices to check its performance.
- Mechanical extensometers, used for measuring settlement and linear deformation, are oriented in horizontal and vertical directions. These devices are spaced at different intervals horizontally throughout the dam with groups every 30 meters in elevation.
- V-Notch weirsare used to measure seepage through the curtain of the dam. One is located in a trench at the base of the dam on the lower right side
- Force balance accelerometersare used to measure motion of the dam, which is an indication of deformation. These devices are useful in monitoring damage from seismic events.
- Inverted pendulums – These devices measure vertical deformation of the dam. One end of a thin wire is attached to an anchor which is grouted in solid rock below the dam with the other end attached to a float station that is attached to the dam. Movement of the float relative to the anchor alerts dam operators to possible motion.
- Direct pendulum – This device is similar in operation to the inverted pendulum except the anchor is located at the top with the float tank located at the bottom. There are 21 direct and indirect pendulums located in El Cajón.
- Bourdon Pressure Gages are used to measure the static pressure of the water contained in the reservoir.
- Geodetic surveyingstations are located at fixed reference points in the area surrounding the dam. "Object" points are installed on the face of the dam (look closely you can see the yellow drums). Surveyors use devices such as theodolites and total stations to compare changes in distance and elevation of the object points on the dam to the reference points. The information gathered gives dam operators a picture of how the dam is settling or if motion of the face is occurring.
- Inclinometers are installed in the dam's abutments to monitor slope stability. The device measures linear deformation.
- Seismographsare used to monitor vibration of the structural elements due to geologic activity. Because El Cajón lies on three fault lines, the collection of seismic information is crucial to making decisions about the dam's operation.
The important role these devices play came into focus after a 7.1 magnitude earthquake, originating 200 miles north of Tegucigalpa, caused massive damage to many pieces of infrastructure May 28, 2009. These devices were critical to determining the internal deformation of the structure.
Notes
- ISBN 978-0-7844-0923-7.
- Worldbank. Archived from the originalon 2011-06-12. Retrieved 2009-10-05.
- ^ a b c d "Represa Hidroeléctrica Francisco Morazán "El Cajón"". ENEE. Archived from the original on 2009-09-16. Retrieved 2009-10-05.
- ^ McCully, 1996: 324-325
References
- ENEE (Empresa Nacional de Energia Electrica), 2009, "Central Hidroelectrica 'El Cajón'," Honduras C.A.(Translated from Spanish to English by Missouri S&T)
- McCully, Patrick (1996). Silenced Rivers. The Ecology and Politics of Large Dams. London: Zed Books.
- Rodriguez, 2009, "El Cajón report on Honduras Earthquake,"
- VOA News, 2009, "Honduras Earthquake Kills 4," http://www.voanews.com/english/archive/2009-05/2009-05-28-voa8.cfm?CFID=260696152&CFTOKEN=41550207&jsessionid=de3020563db41dca29b9143924434d376143, (July 21, 2009)