Oroville dam designers included "overdesign" in the thickness, depth, and dimensions of the layers of the earthfill embankment design. Thus there is a built in safety factor. All earthfill embankment designs have seepage. They just need to be on top of anything that develops.
The problem that I have is that there is an inaction behavior that seems to be ignoring the Dam Inspectors recommendations (inferring from multiple Inspection reports).
What if any preferable alternatives are there to earthen-made dams of this size?
About 35 years ago, I was a state inspector of things like
landfills, drinking water plants, and wastewater treatment plants.
We wrote up our observations in reports and passed them up the line.
We never knew what action was or was not taken until that site
popped up on the inspection to-do list again a few years later,
and we went back there to inspect it again.