Most older dams were built without adequate spillways to release water in heavy rains, causing water to run over the top. Inadequate spillway capacity is the most common deficiency and a major cause of dam failures. A dam failure can affect thousands of lives and cost millions of dollars. In the past 10 years, more than 200 documented dam failures have caused millions of dollars in property damage and repair costs. Thirty-five percent of these haven't been inspected since 1990.
Every state has at least one high-hazard dam.
North Carolina has the most high-hazard dams with a total of 874. Pennsylvania and Texas each has more than 500 high-hazard dams. Funding for these repairs is sorely lacking. Furthermore, repair projects on thousands of other dams, which must be rehabilitated before they become unsafe, are on hold due to lack of funding. Equally alarming is the fact that many dams built more than 50 to 100 years ago have been abandoned and the owners are unknown.