It has been this way for more than 50 years from my own experience traveling through this area. Seems to be a permanent job site for the state highway workers. There is even a permanent set of traffic lights on each side of one major slide.
I worked for the then Division of Highways in the 1970's and the engineers were clueless as to how to stabilize, and not destabilize slopes. The same practices that were consistently failing then are still being used today with exactly the same results. Two sections of new overpasses built by my house both had slope failures within 6 months of their completion. Great example of institutional insanity.