The work went ahead and raised the height of the dams, in the case of the dam above the Men's Swimming Pond by 18 feet. The City of London Corporation said the work should be carried out urgently to reduce danger of flooding in surrounding built-up residential areas in the event of one of the dams bursting. The initial estimate of the number of lives which might be lost, in the event of a dam collapse in an extreme flood event, was over 2000 (2006 estimate). This figure has been reduced to less than 400, still a large number. However the chance of such an event is one in 400,000 years.