The movable Dutch Maeslant surge barrier closes when the city of Rotterdam is threatened by floods due to a big storm on the North Sea. However, the barrier might get damaged and repair may be needed. The question is what is the probability that a second closure is necessary during the repair time? We solve the problem by using a huge dataset of weather situations that accumulates to more than 6000 years. It is found that two closures within a month occur on average once in every 150 years.