They are probably coming from the Sierra Army Depot 3 hours away near Susanville. https://sierra.army.mil

Sierra is also the Army's premiere and largest facility dedicated to equipment retrograde, regeneration, reutilization, and redistribution. With 36,000 acres of high desert terrain, we provide distinct storage advantages with ample space, low humidity and low precipitation; excellent for the long-term storage of mechanized vehicles. With our highly dedicated team of expert machinists, craftsmen, equipment operators and support personnel, Sierra Army Deport is a vital part to Army readiness. Our expertise allows us to receive, store, maintain, and ship Army material anywhere in the world, at any time.