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Iraq's Mosul Dam is in danger of collapsing any day

 
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Dr. N. Subramanian
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PostPosted: Tue Feb 16, 2016 10:43 pm    Post subject: Iraq's Mosul Dam is in danger of collapsing any day Reply with quote


Iraq's Mosul Dam is in danger of collapsing any day




The Mosul Dam ( formerly known as Saddam Dam) in Iraq is the largest dam in Iraq. It is located on the Tigris River in the western governorate of Ninawa, upstream of the city of Mosul. At full capacity, the hydroelectric dam holds about 11.1 cubic kms  of water and provides electricity to the 1.7 million residents of Mosul. It is ranked as the fourth largest dam in the Middle East, measured by reserve capacity, capturing snowmelt from Turkey, some 110 km north.

Construction of the Dam

Construction on the Mosul Dam began in 1981, when Saddam Hussein was in power, by a German-Italian consortium that was led by Hochtief Aktiengesellschaft.  Because the dam was constructed on a foundation of soluble gypsum, the engineers recommended the implementation grout curtain within the foundation before the superstructure was built. Instead, to speed construction of the dam, engineers installed a grouting tunnel  that would allow almost constant injection of cement and drilling mud into crevices in the base (that are widened by the water flowing through them), in order to promote stability. Construction was complete in 1984 and in the spring of 1985, the Mosul Dam began to inundate the Tigris River, filling the reservoir which submerged many archaeological sites in the region. The power station began generating power on 7 July 1986. Because of significant structural stability issues associated with the Mosul Dam, ongoing grouting and additional construction and repairs are necessary.

Instability and remediation

As mentioned earlier, The earthen embankment dam is located on top of gypsum, a soft mineral which dissolves in contact with water. Continuous maintenance is required to plug, or "grout", new leaks with a liquefied slurry of cement and other additives. Interestingly, more than 50,000 tonnes of material have been injected into the dam since leaks began forming shortly after the reservoir was filled in 1986, and 24 machines currently continuously pump grout into the dam base, and sinkholes form periodically as the gypsum dissolves beneath the structure! Seepage from the dam funnels into a gushing stream of water that engineers monitor to determine the severity of the leakage. "You cannot find any other dam in the world like this," said Mr. Ayoub, who has worked at the dam since 1983 and has managed it since 1989.


Water rushes down a spillway at Mosul Dam. As engineers monitor the structure to determine leakage, machines constantly pump grout deep into its base. (U.S. Army Corps Of Engineers)


A September 2006 report by the United States Army Corps of Engineers (US ACE) noted, "In terms of internal erosion potential of the foundation, Mosul Dam is the most dangerous dam in the world". The report further outlined a worst-case scenario, in which a sudden collapse of the dam would flood Mosul within hours under 20 m of water and Baghdad, a city of 7 million, to 15 feet, with an estimated death toll of 500,000. In addition, more than a million people will be forced to vacate their homes. Disease and looting as the floodwaters raced through Baiji, Tikrit, Samarra and even parts of Baghdad would complete that dreadful scenario. Even in a country gripped by daily bloodshed, the possibility of a catastrophic failure of the Mosul Dam has alarmed American officials.

A report on 30 October 2007 by the US Special Inspector General for Iraq Reconstruction (SIGIR) said that the dam's foundations could give way at any moment. However, taking the dam out of commission is not an attractive option. Emptying the reservoir would leave Iraqis seriously short of drinking and unpolluted irrigation water in the summer. Hence, the Army Corps of Engineers proposed that the Badush Dam, under construction downstream, be expanded to obstruct the large wave which would result if the Mosul Dam collapsed.

During 2004, dam manager Mr. A.T. Ayoub ordered the dam's water level, which can reach 330 m above sea level, to be restricted to a maximum of 319 m , thus reducing the pressure on the structure. Moreover, Iraqi officials maintain that the U.S. government is overstating the risk. The proposal to expand the Badush Dam has also been resisted by Iraqi officials, on the ground that the current cost of the Badush Dam is US$300 million and the the proposed expansion by US ACE would cost $10 billion.

In 2007, the U.S. Army Corps of Engineers developed and executed a US$27 million plan to help continue maintenance and repairs on the Mosul Dam in the short-term. The Iraq Government is implementing a long-term solution which includes the construction of 67 m deep walls around the dam foundation. The ongoing project is expected to cost $4 billion and last four to five years.

Growing instability concerns due to the Islamic State of Iraq and Syria (ISIS) previous control of the dam and poor security led the Iraq government to award a US$2 billion contract to an Italian company, Trevi Group, in December 2015. The contract covers repairs to the dam and the Italian government plans to send 450 additional troops to provide security at the dam site. Trevi Group offered a more advanced and permanent method of plugging cavities in the stone base than the constant maintenance it has required for the past 30 years. That maintenance came to an abrupt halt after IS seized the dam in August 2014, and has continued only intermittently after it was seized back three weeks later. Essential equipment went missing then, and half its staff decided not to return to work.

In January 2016, U.S. Lieutenant-General Sean MacFarland,who commands American forces in Iraq, warned that the dam might undergo a "catastrophic" collapse (Sensors installed by American army engineers in December showed widening fissures in the fragile gypsum base underneath the dam, though no one can predict when a breach might occur).  MacFarland added, “What we do know is this—if this dam were in the United States, we would have drained the lake behind it". Maintenance had suffered as ISIS had removed equipment and chased technicians away in August 2014, and the grouting schedule had not been maintained. He indicated that contingency plans are in the works to protect people downstream in case of a collapse.

According to The Economist, "One study says that if the dam collapses, Mosul would be submerged within hours. Another warns that half a million Iraqis could be killed by floodwaters, and more than a million forced from their homes. Disease and looting as the floodwaters raced through Baiji, Tikrit, Samarra and even parts of Baghdad would complete that dreadful scenario."


Reference:
(1) https://en.wikipedia.org/wiki/Mosul_Dam
(2) http://www.washingtonpost.com/wp-dyn/content/article/2007/10/29/AR2007102902193_2.html
(3) http://www.economist.com/news/middle-east-and-africa/21692903-most-dangerous-dam-world-watery-time-bomb



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