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At last weekend feverishly working on a solution to the hole at Grave making shipping now blocked since Thursday. Twelve scenarios are calculated. Stakeholders have looked at the possibility of a mobile dike or pontoons in big bags.
Eventually opted for a temporary barrier of boulders behind the weir. Over the dam, partly covered by stones, is a water retaining cloth to stop the water. The construction is begun this week, the necessary equipment is already underway. It is expected that the construction lasts two weeks. Thereafter, the navigation on the Meuse can get going again.
It is expected that the construction will take two weeks then shipping on the Meuse can get going again. The dam is 30 meters wide and 5.6 meters high. It is connected to the pillars of the northern opening of the weir and comes to rest on a concrete barrier. Thus the temporary dam water level is the same as the actual dam. If the water level in the river Maas is at 7.9 meters above sea level, ships are again able to sail and come houseboats that are now stranded lie loose on river bottom.
The chosen solution was presented by Rijkswaterstaat water engineers from TU Delft for an independent second opinion. They have been unable to pass on all, stresses engineer Miller. "There was no time for that." But the solution adopted, according to him, the charm of simplicity. It can be fast. "And things can go wrong with relatively few."
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One complication was in finding a temporary solution that should be quickly removed if there comes a flood wave. If the water may not alter, Meuse Dykes can not cope, says Miller. "Then you have rather low water flooding."
A spokesman for Rijkswaterstaat may then be reduced to the dam within 48 hours that the water can over it. According to Department of Public Works, the coming months are likely to expect a high water.
If the hole is close to Grave, we are here to draw lessons for the future
Bas Jonkman, professor of integrated engineering
Simultaneously with the construction of the dam is working to repair the dam. With 'droogzetkuipen' 5 meters wide and 9 meters high, parts of the weir put dry so the damaged yokes can be removed and replaced. The weir at Grave is made up of separate parts. Rijkswaterstaat expects that this job will take more than six months. In the meantime, the temporary sheet pile wall to keep the water level high.
Bas Jonkman, professor of integrated engineering at the Faculty of Civil Engineering of TU Delft expects will generate a discussion after the repair on better protection of river weirs. The probability that a ship through the weir canal is small. "But the consequences are perhaps greater than we thought, 'says Jonkman. By one accident all shipping traffic is paralyzed. In the Meuse seven dams, which makes the river vulnerable.
Storm surge barriers are protected by double doors, dams not. Jonkman think of solutions that can be deployed rapidly in emergencies, such as an emergency closure which can be sail or an inflatable bladder. "If the hole is close to Grave, we are here to draw lessons for the future."
external research
Tuesday it became known that Rijkswaterstaat, municipalities, security regions and water authorities have ordered an external study on the dam accident. It will show whether the responsible authorities have acted properly in addressing the near-disaster when a ship loaded with benzene feed through the weir.
After the accident came from various quarters criticism. Rijkswaterstaat would have concluded the dam late at Heumen which dropped the water level in the Maas-Waal canal. Which went from lock to 2:30 am in the morning close, seven hours after the accident. The mayor of Heumen felt he was informed too late.
The research, which focuses on the first 48 hours after the disaster, must be completed within six weeks. The Maas-Waal canal is now navigable again limited.
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