Rogun Dam
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The Rogun Dam, a partially completed dam located on the Vakhsh River in Tajikistan, has a four-decade history that has seen it devastated by floods and left incomplete after a number of political issues, including the break-up of the Soviet Union, the civil war in Tajikistan, and a disagreement about the height of the dam.
Construction began in 1976 and came to a halt for the first time in 1991 when the Soviet Union broke up. Construction resumed in 1998, with a series of studies being expedited to ensure the dam would survive despite its location in an area rife with seismic activity.
If constructed, it would stand as the tallest dam in the world at 1,099 feet (335 m) high, producing 3,600 megawatts of hydroelectricity and becoming the region’s biggest exporter of electricity.
As of August 29, 2007, the Tajik government announced that they had cancelled their contract with Russian aluminum giant, RusAl, a company that agreed to construct and invest as much as $2 billion towards the project that would provide electricity and irrigation for Tajikistan, as well as neighboring nations Uzbekistan, Afghanistan and Turkmenistan. The disagreement was over the proposed height of the dam. Tajik government insisted the dam reach 1,099 feet (335 m) high, while feasibility studies have prompted RusAl to stay below 919 feet (280 m).[1]
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[edit] Construction History
[edit] Initial Construction
Initial construction of the dam began in 1976 after 11 years of studying and surveying the site. It came to a halt due to lack of funds. Some components of the first construction phase were completed, including some excavation and underground and surface facilities.
Construction was restarted in 1987 but ceased again in 1991 when Tajikistan was embroiled in a five-year civil war.
In 1993, a flood destroyed what little excavation work had been done to dam's foundation, as well as the access roads and tunnels that had been constructed. The flood blocked the diversion tunnels causing the dam to overtop by 148 feet (45 m), washing away the cofferdam.
[edit] Partnership
Despite many challenges in constructing the Rogun Dam, Russian aluminum giant RusAl and the Tajik government were committed to seeing its completion. The two formed a partnership in 2004, with Tajik government putting forth US$14.5 million and RusAl funding US$2.2 billion towards the project. The new construction date was set for 2007 with RusAl announcing they could have the dam extended to 738 feet (225 m) high with two operational units by 2011.
An extensive plan was scheduled for the completion of the dam. Although it did not reach its final stages, some construction was completed and it is probable that it will continue the path previously outlined for it if and when the Tajik government can find interested investors to fund the dam’s completion.
[edit] Planned and Completed Construction
The initial stage of construction for the 1,099-foot (335-m) high clay embankment dam involved constructing a reservoir with a volume of 3.2 cubic miles (13.3 km3); a spillway with an intake shaft tunnel and open chute; and an underground powerhouse with 6 x 600 megawatts installed capacity with an outdoor switchyard and a 500-kilovolt transmission line.
The damage left by years of inaction and the destruction of the flood left the previous dam only somewhat intact. On one side, existing access roads and tunnels would provide access to the construction site. The other side, however, needed to be completely demolished and constructed from scratch.[2]
As much as 12 miles (19.26 km) of permanent operation roads would have to be constructed, as well as 17.6 miles (28.3 km) of temporary roads, two miles (3.19 km) of transport tunnels, and four road bridges, in order to resume construction. In addition, a minor excavation project was carried out to remove sandstone and mudstone.[3]
Previously completed access roads and tunnels were constructed by earthmoving equipment such as excavators, shovels, compactors, and hauling equipment. The access roads and tunnels would enable workers to divert the flow of the Vakhsh River in order to extend the dam and build two cofferdams that would play a pivotal factor in the dam’s stability. Additional to the construction schedule were temporary and permanent roads and site utility systems such as power and water supply, as well as sewage.
While some roads were in need of repair, the first stage was to include the collection of rockfill by excavators and shovels which was loaded into dump trucks and poured into the dam site. As much as 758,611 cubic yards (580,000 m3) of clay rockfill per month would fill the dam.[4]
[edit] Out With the Old, In With the New
Typically for this kind of dam, the rockfill is compacted using a series of specialized compaction equipment. The wet rock dump technique, which was frequently employed in the 1960s and 1970s, was found to be less effective than other techniques for improving the strength and compaction of the rockfill, resulting in a less stable dam in the post-construction stages. Both the Army Corps and the Bureau of Reclamation, two agencies crucial to the building of dams in the U.S., cited better compaction results with equipment such as heavy steel drum vibratory rollers, as opposed to the non-vibrating versions, whether steel or rubber tired.[5]
Most of the unused tunnels were filled with rockfill and sealed with concrete plugs. While hydraulic steel structures were already on-site ready to be utilized, a lot of equipment used in the 1970s was considered outdated by today’s standards and had to be replaced with modern equipment.
Modern technology also played a significant factor in constructing the dam the third time around, as experts have had more time and technology to study the geologic conditions surrounding the dam. The geology consisting of heterogeneous bedrock Gaurdak salt formations that had wedged between the Ionakhsh fault, could submerge the reservoir and produce 33 to 39.4 feet (10 to 12 m) of residue by the time it reached the surface. Salting took place to stabilize the structure, and grouting curtains were completed and used as a temporary hydraulic barrier. Additionally, long-term grouting would need to be completed in order to provide a permanent barrier for the completed project.
The dam is set in a location where the Eurasian and Indopacific plates are converged, causing a compression in the tectonic unit of the Tajik region. Although the dam would lie within two faults, the Ionakhsh and the Gulizindan, upstream and downstream respectively, experts estimated that building a rockfill embankment dam as opposed to other types of dams would provide Rogun with optimal stability and strength.
The studies Lahmeyer presented to RusAl revealed that the deformities in the formation of the dam would be better suited to rockfill rather than a concrete or arch dam, which were also suggested. The studies suggested building a dam as high as 771 feet (235 m), requiring a rockfill of 110 feet (33.6 m). Further excavation would not be necessary. The excavation completed in 1976 remained intact but further compaction of the soil would be required.
[edit] Stage 2
Stage 2 of the planned construction involved installing three Francis turbines, rated at 600 megawatts by the final stage, with a fourth turbine to be added to the collection later in the second stage.
A headrace tunnel was also to be constructed for each unit with tunnel boring machines, complete with a separate power intake, pressure shaft, and pressure tunnel to the left of the embankment. Tailrace tunnels were to be constructed as well, but would follow a different method than was employed in 1978.
Diversion tunnels were also set to be built on both sides of the dam. The tunnels are each 4,856 feet (1,480 m) long , consisting of an open channel and section measuring 46 x 56 feet (14 x 17 m) in the shape of a D. Two diversion tunnels that are being planned will be modified to an inverted slope to dam and divert the river.
Cofferdams are also being constructed to divert the river during the dam’s construction. The river was diverted to the first diversion tunnel, located on the left side of the embankment, as well as into an auxiliary tunnel so a diversion bund could be constructed and set in place. A cofferdam reaching 230 feet (70 m) high, meanwhile, was going to be constructed and would remain a component of the dam once it was completed. The second cofferdam was elevated up to 3,228 feet (984 m), built primarily to protect the dam and enable workers to build diversion tunnel 2. Cofferdam 3 would be constructed to seal off the Vakhsh downstream flow.
[edit] A Better Spillway
A spillway, a device constructed to allow water to escape in times of flooding, was also in the construction plans. Due to Rogun’s tumultuous fate with a flood in 1993, an effective spillway was crucial. The 1978 design was flawed with limited discharge available. The modern version would be constructed to benefit the rockfill dam and enable it to withstand flood overtopping for a much longer period than previously sought. In fact, the previous spillway was a crucial fault in the original construction that led to its demise during the flood.
The new spillway would comprise an open chute on the right side of the abutment, resulting in a 272-foot (83-m) discharge for at least 50 percent of the design. Two tunnel spillways would be constructed to the right of the embankment, totaling to 25 percent of the discharge. The spillway would be able to combat with floods that send water as high as 869 feet (265 m). The vortex-type spillway was in the works, with the only other one like it in the world belonging to the Tehri Dam in India. The vortex spillway causes axial rotation of the water flow, which produces high energy and dissipation due to the friction caused by water against the vortex wall.
Additional tunnels and chutes would be constructed in order to prevent cavitation, as well as a mid-level outlet tunnel located above diversion tunnels one and two, that would be constructed for controlled impoundment, but would be plugged during the final stages of construction.[6]
[edit] Height Issues
One of the main issues of debate between the Tajik government and RusAl was the height of the dam. The Tajik government insisted it should reach 1,099 feet (335 m) high, rendering the dam capable of producing 13.1 billion kilowatts of electricity per year.
RusAl, having carried out a number of studies conducted by Lahmeyer in the high seismic-prone area, insisted that the dam should reach no higher than 919 feet (280 m), in fear that greater proportions would not be able to withstand earthquakes and floods. At this height, the dam would produce 8.9 billion kilowatt hours of electricity per year.
"The Rogun project is crucial to our partnership, but it has regrettably become a hostage to technical and technological disputes between specialists and experts," Ramazan Abdulatipov, Russia’s ambassador, said in a conference that took place in Danshube.[7]
Despite promises of completion, the construction for the Rogun Dam has barely surpassed the initial stages of rehabilitating the construction that was previously built and left destroyed over years of political turmoil and floods.
Mahmud Turakulov, “We hoped to find work at Rogun, but everything is closed, no construction has begun,” said Russian construction worker Mahmud Turakulov.[8]
[edit] Equipment Used
[edit] Unique Facts
- If the Rogun HEP project was completed, it would reduce the sedimentary disposition occurring at the Nurek Dam, which embraces the same Vakhsh River.
- Concerns have been posited that the completion of the dam could cause problems with Tajik neighbors Uzbekistan, Afghanistan, and Turkmenistan, all nations that rely on water from the Vakhsh River. Tajikistan’s control of the dam could limit or prevent supply to these nations.[9]
- Currently, residents receive three to four hours of electricity per day, and sometimes no electricity whatsoever.
- Tajik owns four of the world’s hydropower supply, with 95 percent of electricity in Tajikistan deriving from power plants.[10]
[edit] References
- ↑ History of Rogun Dam. CISRG Database, 2008-09-24.
- ↑ Onwards and Upwards. International Water Power & Dam Construction, June, 2008. (accessed: 2008-09-24)
- ↑ Berga, L. Dams and Resevoirs, Societies and Environment in the 21st Century.
- ↑ Onwards and Upwards. International Water Power & Dam Construction, June, 2008. (accessed: 2008-09-24)
- ↑ Breitenbach, Allan J. History of Rockfill Dam Construction: Part 2. Geo Engineer, 2008-09-24.
- ↑ Onwards and Upwards. International Water Power & Dam Construction, June, 2008. (accessed: 2008-09-24)
- ↑ Russia to Complete Rogun Hydroelectric Plant in Tajikistan. CaWater-info.net, February, 2007. (accessed: 2008-09-24)
- ↑ Tajikistan's Energy Dilemma. Institute for War & Peace Reporting, 2008-09-08.
- ↑ Tajikistan's Energy Dilemma. Institute for War & Peace Reporting, 2008-09-08.
- ↑ Onwards and Upwards. International Water Power & Dam Construction, June, 2008. (accessed: 2008-09-24)
