From the June 17, 1966 Telegram-Tribune:

"About 300 of Cal Poly's graduating seniors shrugged off the cloak of decorum and went underground last night. And what a ball they had at the "Sewer Stomp." With San Luis Obispo Creek dammed off for the night, the seniors pranced, leaped watusied, cavorted and even slowed down to a waltz on a mammoth straw floor, in the tunnel under the downtown area. There were a few difficulties. Bats, apparently holding a lease on the drain, were disturbed by the Thunder Mugs, a loud beat band. There was a small bonfire in the hay when someone dropped a match on the dance floor, but that was quickly suppressed. There were rumors of attempts to flood out the party by by high school students, but they didn't materialize. The floor, not made for such strenuous stomping, began to leak about halfway through the dance, but that didn't slow the dancers much. And senior class president Ken Slocum was congratulated for making a sewer stomp come out smelling like a rose."