I happen to live downstream. I wasn't concerned with the spillway failing. The main concern is the erosion on the mountain itself under the emergency overflow. That section to the left of the actual dam. The dam is 20 feet higher than the section on the left. Water came over that area for the first time ever since the dam was completed. The water coming down the hill is eroding the actual hill itself. Huge concern about the pressure from the max capacity lake behind it. If that system crumbles, mind you it's not the dam that fails, its the HILL next to it, then a 30 foot wall of water hits and even us here in Sacramento are going to get our feet wet.
Now, this morning, they are "fixing" the problem. They are filling the holes that eroded with concrete and rocks. My concern, that isn't going to fix the problem of further erosion around those new patches.
This condition was pointed out in a 2005 lawsuit and is unfolding exactly as was described. There is talk that the concrete cap over the lip of the emergency overflow would protect the top of the hill when the water poured over. They are right, but it doesn't protect where the water hits the dirt immediately underneath.
Now, that spillway, the concrete one that came apart first, that soil eroded under the concrete spillway and then the concrete collapsed. That entire hill is unstable and eroding.
Oh, side note, that massive dam is anchored into that same hill.
Concerned? I am, and I have been active in the levee upgrade program here in the valley since the mid 90s and am very familiar with the infrastructure, live in an area surrounded by close levees and water, a virtual island, and this is the first and only time in m 35 years here I am concerned about flooding. I can't take my eyes off this hill.
Here, they are plugging holes. Concern is the soil eroding around the plugs
Dam to the right, Concrete spillway to the left is what initially blew apart by the soil underneath eroding away, there was a cavity under the concrete, it blew apart. To the left, that's the lower emergency overflow. That concrete wall is sound, the soil below it, down the mountain, and under the spillway, that's coming apart.
