Problems around the now sunken area of the basement of the Theatre and Communications Building were first reported in 2003 by a building inspector, who recorded that there were noticeable and sizeable cracks in and around the southeast stairwell of the building. Every year since, building inspections have documented similar cracks.
Although the same problems in and around the stairwells near the sunken area were reported on almost every inspection over a four-year period, there was no reason for The University to be concerned, according to Ronnie Brooks, director of The U of M physical plant.
"The building itself is built out of brick, which cracks and needs patching on a fairly regular basis," said Brooks. "Each time the cracks were reported, we had them fixed."
Brooks also said that the sunken area was caused by an air pocket that formed from the settling of the soil underneath the building. According to him, pockets of air are common in structures built with a spread footing foundation, in which separate rooms of a structure are built on individual slabs of foundation. After the foundation for each room is built, the hallways or connecting areas are laid out "on grid" or directly on the earth.
While Brooks said air pockets are the cause, John Woods, project manager for the Woods Chris Construction Company, said the settling of soil under a building does not usually cause the sinking of an area of that size.
"The sinking caused by the settling of soil usually occurs in the first two or three years after a building is built," said Woods. "The entire area underneath a building usually sinks roughly the same amount."
According to Brooks, the sunken area of the floor is 10 to 15 feet long and the width of the hall. The floor has dropped 1 to 2 inches, but there is an additional 4 to 6 inches of air underneath it. Brooks said the floor itself has four feet of concrete under it, poured to increase strength.
"If there were never any repairs done to this area, the floor would probably still never fall or settle anymore," Brooks said. "It just wouldn't look good."
Woods, however, said that having four feet of concrete poured under something constructed "on grid" was very peculiar.
"I don't know why there would be four feet of concrete underneath the hallway area, unless the original contractors thought there was bad soil there, dug it out and filled it with concrete," Woods said. "Even then it would be a weird solution. I really can't think of a good reason why they would do that."
According to Brooks, when it was built, soil was put under the building equally and the sinkage due to settling of soil may have been caused by a variety of factors such as earthquakes, rain or vibrations from Central Avenue's traffic. Woods, however, said that the sinking of only certain areas under a structure is more likely to have been caused by poor soil, water drainage or faulty construction from not connecting the area under the hallway to the foundations of the rooms around it.
"The soil should have been tested prior to building the structure and a water table done to predict erosion risks," Woods said. "Also, if the hallway was poured separately and not attached to the slabs of the adjacent foundations, it could also be a factor."
While Brooks said there are plans for repairing the affected area in the Theatre and Communications Building, repairs are unlikely to commence before March.
"There are several theater productions that will be put on over the course of the semester," Brooks said. "In respect to them, we will probably wait until around spring break when the building is empty."
According to Brooks, the repairs are relatively minor and should take anywhere from a couple days to two weeks, depending on what method they choose to use.
"The floor is built strong enough to hold itself up," Brooks said. "They've already rolled pianos across it with no problem."
