An assessment done by Associated Press has found over 2,200 high hazard dams in the United States which are in poor or unsatisfactory condition. This number has increased substantially since the last review done by AP three years ago, which found 1,680 dams posed a potential risk.
U.S. dams are on average more than 50 years old, and buildings and roads have since been built below them. In addition, heavier rainfall driven by climate change could cause problems for ageing dams. In 2020, 10,000 people were evacuated in Michigan following catastrophic dam failures at the Edenville Dam and the Sanford Dam as rapidly rising water overtook the dams.
Biden’s $1 trillion infrastructure bill included about $3 billion for dam-related work, including dam safety plans and repairs. However, the Association of State Dam Safety Officials estimates the cost of rehabilitating U.S. dams in $76 billion.
The U.S. Corps of Engineers keeps a National Inventory of Dams with more than 90,000 dams. Those classified as high hazard are those where failure or mis-operation will probably cause loss of human life. The hazard potential is not related to the condition of the dam or the risk of the dam failing. The inventory includes hazard ratings and condition assessments for more than 25% of the dams, but the information is not available for the rest, because federal agencies and states either do not track that information, or do not release it based on terrorism concerns.
Part of the reason why the number of high-hazard dams classified as in poor condition or unsatisfactory condition has increased is regulations are now stricter, as state safety programs improve inspections and update precipitation models. Sometimes risks can be reduced by temporary measures such as lowering the water level. The El Capitan, Hodges and Morena reservoirs in California are thus filled to less than half their capacity over concerns they could fail in case of an earthquake or heavy rainfall.
Repairing old dams is costly and can take years. Trying to remove them is often controversial, even when the structures are obsolete and removal would benefit public safety and river health. Once a radical notion, dam removal has become an accepted tool to address outdated infrastructure, with 57 dams removed in 2021 across the U.S. according to American Rivers. A 2021 report by the Institute for Water, Environment and Health (United Nations University) predicted a global increase in dam decommissioning as economic and practical limitations prevent dam upgrade.
