FWIW there is no place in California where the railroads are not going to have to deal with mother nature. In addition to periodic washouts in south Orange County and north San Diego County, much of the Surf Line goes over and around the Newport-Inglewood-Rose Canyon fault zone. One day either fault could produce a 6.0 - 7.4 earthquake. Further north much of the line runs through areas prone to liquefaction.

BOB2 and I have also exchanged opinions on the practicality of a second line running south from Riverside, along the old ATSF Elsinore branch, then south to Temecula and on to the north county area roughly parallel to US 395. The trouble with this alignment is that it was (and might be again) prone to flooding.