The Center Street Underpass has filled with run-off from heavy rains at least three times in the last 25 years. Most recently (August 23, 2013), a heavy rainfall combined with a hailstorm lasting less than two hours filled the underpass nearly to the brim.
Above is a still from a video taken by a local observer that demonstrates the force with which the water ran into the underpass.
Soon after the storm began, the underpass was filled enough to flood the pedestrian walkways on either side.
Twenty minutes after the storm, the underpass was filled with about 10 feet of water (note the 12' 2" clearance sign). A few foolhardy citizens decided to swim in the temporary "Lake Pocatello," until police officers cordoned off the area.
