4/30/2010:
Residents of Fargo were surprised to learn of an underground cavern within their city limits on this day in 1917. Fargo City Commission President Alex Stern called an emergency meeting of the commission after a portion of sidewalk along first avenue north collapsed, revealing a giant hole beneath the street. Fortunately, no one was injured in the incident, although the enormous hole attracted the attention of onlookers for days.
Residents discovered the hole between Broadway and Fifth Street during the early hours of the afternoon. Fearing additional cave-ins, vehicle and pedestrian traffic was diverted until the underground cavern could be investigated safely by Fargo officials. Eventually, city engineers F. L. Anders and E. M. Hooper were sent below the concrete to find the source of the problem. A pulmotor and ropes were lowered into the nearby manhole, should the men become overwhelmed by gases or need oxygen. Once inside the cavern, the men found themselves up to their knees in mud, and frost along the walls of the hole. They also found the cause of the cave-in; the roof of the sewer running below the street had actually collapsed and washed away into the river. The only foundations holding up the street for a distance of twenty-five feet were the concrete supports of the sidewalk. The city officials measured the hole to be eighteen feet deep, fifteen feet wide, and twenty-five feet long. Fargoans were quite surprised to learn the massive size of their underground cavern. The engineers also found additional disintegration occurring in nearby sewer walls that would need to be repaired. Anders guessed that the sewer had been eroding for several months before the collapse.
Built in 1909, the sewer weathered the North Dakota elements for eight years before caving-in beneath the city. It was constructed as a brick arch sewer, six feet high and five feet in diameter. The city commission authorized funds to begin work on the sewer at once. Fargo's one-time underground cavern was repaired and filled in immediately.
Source:
The Fargo Forum and Daily Republican (Evening ed.). April 30, 1917: p.10.
Dakota Datebook written by Jayme L. Job