In the last decade, dam safety officials from across the country have reported hundreds of dam failures and "incidents" - situations that, without intervention, would likely have resulted in dam failure.
According to data gathered by the Association of State Dam Safety Officials, from January 2005 through June 2013, there were reports of 173 dam failures and 687 incidents, out of 87,000 dams nationwide. The good news, according to the Association's executive director, Lori Spragens, is an uptick in repaired deficient dams.
Meanwhile, crews working around the clock atop the crippled Oroville Dam have made progress repairing the damaged spillway, reducing the lake level by at least 8 feet overnight at the Northern California reservoir.
Workers hoisted giant white bags filled with rocks, and at least two helicopters planned to fly in rocks Tuesday then release them into the eroded area of the spillway.
Dump trucks full of boulders also were dumping cargo on the damaged spillway.
Workers are rushing to repair the barrier at the nation's tallest dam after authorities ordered the evacuation of nearly 200,000 people for everyone living below the lake amid concerns the spillway could fail and send water roaring downstream. Evacuations remain in place.
State Department of Water Resources officials hope to reduce the lake level to 860 feet by Thursday when storms will bring more rain, spokesman Chris Orrock said. The level was 884 feet on Tuesday morning.
With files from the Associated Press.
Eric Kurhi, reporter at The Mercury News following the story
Lori Spragens, Executive Director, Association of State Dam Safety Officials