At the Lake Needwood Dam, the yellow line shows how high the water after persistent raining in 2006.
Thursday is National Dam Safety Awareness Day, and federal officials didn't have to stray far from D.C. for an example of how dangerous dam breaches can be.
On this day in 1889, the worst dam failure in United States history occurred when the South Fork Dam in Cambria County, Pennsylvania gave way. As many as 2,200 people perished in what's remembered as the Johnstown Flood. Since then, the federal government has been more active in dam safety, but the Federal Emergency Management Agency says there is still a long way to go.
Federal officials touted their new efforts today at the Lake Needwood Dam in Rockville. Six years ago, several consecutive days of heavy rain caused leaks in the earthen dam. More than 2,000 people in the immediate area were evacuated.
"The water was coming through the rock underneath the dam," says Mike Riley, the dam's engineer of record at the time. "And while that's not good, that's better than it coming through the dam, because the rock is more stable and less likely to deteriorate."
Cement was poured into the fractures in those rocks to prevent future leaks. Riley is confident that will hold up to future storms, though he admits in the last six years there have not been storms severe enough to test the dam.