Found on Wiki. Verrrrrry interesting...
On October 17, 2005 three environmental groups filed a motion with the
Federal Energy Regulatory Commission urging federal officials to require that the dam’s emergency spillway be armored with concrete, rather than remain as an earthen spillway and that it did not meet modern safety standards. "In the event of extreme rain and flooding, fast-rising water would overwhelm the main concrete spillway, then flow down the emergency spillway, and that could cause heavy erosion that would create flooding for communities downstream, but also could cause a failure, known as 'loss of crest control.'"
FERC and water agencies responsible for the cost of the upgrades said it was unnecessary and concerns were overblown.
[25][26]
In 2006, a senior civil engineer sent a memo to his managers stating “The emergency spillway meets FERC’s engineering guidelines for an emergency spillway,” and that “
The guidelines specify that during a rare flood event, it is acceptable for the emergency spillway to sustain significant damage."
[27]
