The dam was built in the 60's. About a decade ago, some groups raised concerns that the aux spillway should be fortified with additional concrete. Since then, that task has never been on the state's to-do list. Sacramento is too busy with delta tunnels and playing with Jerry's train set.
I think the media outside of CA is under the impression that the dam is about to break, which it is not. It's a huge earthen dam. The primary spillway is damaged, which means they cannot shed excess water fast enough, so the excess water is spilling over the aux spillway, which is basically just a smooth concrete wall that has no real reinforcement at the footing. The excess water was eroding the soil at the base of the aux spillway. If the aux spillway gave way, then there would be an uncontrolled flow of excess water until the water level fell below the erosion.
I just wish my mother in law would go back home.