Traffic is once again flowing the entire length of Iowa Avenue after the filling of a sinkhole that could have, theoretically, housed several rows of mid-sized vehicles, stacked five deep.
Measuring about 35 feet long, 25 feet wide and 30 feet deep, the sinkhole was filled with more than 600 tons of rock by Directorate of Public Works contractors.
Iowa Avenue reopened without detours on Oct. 28, five months after traffic was rerouted with the sinkhole discovery on May 24.
"The situation was difficult to remedy, not only due to the size of the sinkhole, but also because of the large number of utilities (overhead electric lines, cable TV, underground communication lines, and storm water lines) that were either in the sinkhole or adjacent to it," said Mariola Bush, civil engineer and project manager.
Closing portions of Iowa Avenue was part of the process to make sure vibrations from the traffic didn't make the sinkhole walls collapse and cause further damage, according to Gary Roberts, DPW Design Branch chief.
Once the area was fenced off to both pedestrian and vehicular traffic, communication and storm sewer lines were relocated. Filling the hole was a process that involved packing with rock/gravel and capping with topsoil and seeding.
The final steps were repairing the sidewalk and force protection walls and reinstalling an electrical pole.
"The entire process went just as we projected," said Bobby Rakes, director of Public Works. "We knew the complexity of moving fiber optic communications cables would take up the bulk of time. Once that was completed, the entire filling and repair process took less than seven days."
"It was truly a team effort by all involved. Amy Crews, Percy Williams and Greg Nelson, DPW inspection team, worked very hard to speed up the process," Rakes added.
Sinkholes are a common feature in Missouri, which has "karst terrain." Karst terrain is a region where the bedrock can be dissolved by ground water, according to the U.S. Department of the Interior's U.S. Geological Survey.
Between 1970 and 2007, the Missouri Department of Natural Resources examined more than 160 collapses reported by the public. Most of these collapses were small -- less than 10 feet in diameter and 10 feet deep; some, however, are quite large and spectacular.
Collapses are more frequent after intense rainstorms, and there is some evidence that droughts play a role as well. Areas where the water table fluctuates or has lowered suddenly are more prone to collapse formation.
Collapses are not limited to karst areas, as they can form above old mines and even from leaky pipes -- though they are much more frequent in areas that have significant karst development, according to the USGS.