If initial lessons included in an interim status report on the cause of February’s failure of the main spillway at California’s Oroville Dam are heeded, hundreds of U.S. dams more than 50 years old may have to be re-examined and upgraded.
The Independent Forensic Team’s Sept. 5 report pinned much of the blame for the failure on the 1968 dam’s design and construction. A 40-ft-wide concrete slab was uplifted and removed, resulting in a blowout of the underlying “highly weathered rock” in the chute of the tallest earthen dam in the country. The failure led to the evacuation of almost 188,000 people and millions of dollars in downstream damage from emergency releases.