During the spring of 1983, the huge Thistle mudslide closed Rio Grande's mainline from April until July. While the new bypass was under construction, Provo area crews were kept busy shoring up the existing mainline along the river in Spanish Fork Canyon. Here caboose 01504 trails six air dumps with two GP9s, returning for another load of rock. Today this rural setting has been transformed with housing developments springing up on both sides of the mainline.
