I don't know because in those days all the rivers were as undamed as the Consumnes is today and with such short and steep watersheds that would get hit with "Pineapple Express" monsoons that melted the Sierra Cement (wet snow) it's easy to see the "inland sea" type floods that occurred in those days. I just don't know if all our current dams plus an Auburn Dam would have flooded a nuke plant near Elk Grove.
I've driven past the site and could look in and see the cooling pond/lake so I doubt there was any levees, dykes or dam that could have withstood the floods described in your link. But as I said above, those floods may not have been so drastic with those wonderful time machines call dams in the watershed like we have now.