It will take US$1B to rehabilitate aging dams in the US, calculates the American Society of Civil Engineer#s. But that estimate is too low, and spending should be around US$1B annually for the next 20 years, according to Martin McCann, Stanford Professor of civil and environmental engineering.

The ASCE calculated its figure for the refurbishment cost as part of a regular report on US infrastructure. However, in response, McCann says the ASCE figure covers only the cost of fixing dams known to be unsafe. Cost factors that were not included in the study include: ongoing maintenance and repair; implementation of action plans at dams that have a ‘high or significant’ hazard; the cost of state and federal dam safety programmes; and the costs of the manpower required to inspect, review and approve dam design, construction and operation. McCann also says that the costs of failure — damage, emergency operations, loss of dam infrastructure and revenue, environmental and economic impact — are also being overlooked.

The cost of dam failure can be huge: the 1976 failure of Teton dam re#sulted in 11 fatalities and damages of US$900M; the failure of the Lawn Lake earth embankment in July 1982 resulted in three fatalities and US$35M in damages; and the failure of a small dam in New Hampshire in 1996 resulted in one death and US$5.5M in damages.

By 2020 it is estimated that 85% of the 85,000 dams in the mainland USA will be more than 50 years old.