This is like the immigration checkpoint on i5 near camp pendleton?
If so, the San Onofre checkpoint is 67 miles from the border. It sits just like a truck scale on the major interstates. It was manned most of the time during the early 80’s then tapered off during the 90’s and was virtually non-existent up to 2007, my last year in Oceanside.
It’s mainly designed to catch mules hauling illegals but I understand some of the slower illegals do get caught here from time to time.
It appeared other illegals or "helpers" would go ahead, and radio back if the CP was operating or down. Sometimes it appeared to go hot unexpectedly to the approaching illegals.
You would see cars suddenly pulling off the road and passengers leaping out into the brush of Camp Pendleton.
There was a lot just north of the CP buildings usually full of various vehicles, I guessed were confiscated from nabbed druggies or illegals.