From 1970 to current date, the Missouri Department of Natural Resources investigated nearly 200 reported collapses and found that most were less than 10 feet in diameter and depth. (Kauffman) However, there have been some documented that have covered numerous acres and have caused massive property and ecosystem damage. Much of this could have been avoided. Tighter regulation of development, requiring basic studies of the geology and hydrology of the area in question, could go a long way to further securing the public safety and welfare, and saving millions in property damage.
Surrounded by a suburban subdivision, the 23-acre Lake Chesterfield in St. Louis drained in just a few days in 2004, after a sinkhole emerged in the lakebed. (Currier) The artificial lake, and accompanying subdivision were built in the mid-1980s, and the only reported review of the structural integrity of the land had been through aerial photos taken by the county. The photos did not indicate the presence of past sinkhole formation, or that the landscape would be prone to this sort of development. However, it is impossible to ascertain anything by simply reviewing aerial photography. Most sinkhole activity happens slowly on a minute scale, over an extended period. A minor, hidden sinkhole could easily have been overlooked. The water from the lake might have begun to seep into a small crack around an overgrown or underwater sinkhole and leaked out a thimble full of water every day for years, until just enough erosion occurred to allow for a greater drainage; at which point it would be much like someone pulling a plug on drain.
There are usually some common elements that a structural engineer, geologist or hydrologist can easily recognize. In reviewing this particular case, the Missouri Department of Natural Resources (MoDNR) found that the rock layers beneath the lake were very “prone to solution activity where soils are thin. The areas have always been a prime candidate for sinkhole development, and intensive studies should have been done, prior to any development.” (MoDNR) Currently, plans are being made to seal the sinkhole and refill the lake, but at great cost to the homeowners of the subdivision. As private property, the city is not obligated to restore the lake, or repair any damages done, but the developer should certainly be held accountable in some way.
With the number of incidents on the increase in southern parts of Missouri, property owners are facing growing repair costs. A simple Geographic Information Systems (GIS) analysis (Comer) conducted in the spring of 2008 discovered that there are very specific areas within Missouri, which are at a higher risk; the City of Nixa is one such area. Situated just a few miles immediately south of Springfield, the community sits squarely on one of these higher risk areas, and it has been known for years to be prone to sinkhole development. In 2006, a sinkhole measuring approximately 60 feet wide and 75 feet deep, opened and swallowed portions of a couple of homes in a half-block area of city. Spokesperson for the City, Bryan Newberry stated, “These homes had been there without problems until this point.” (AP) Typical for sinkhole formation, there is usually very little warning prior to a collapse and many small towns like Nixa and rural areas are ill prepared for situations such like this. Building codes are either not in place, or because the construction is technically outside of city limits, city development regulations do not apply.
As recent as April 2008, new sinkholes have begun to form in and around Nixa. While there are no regulations requiring that there be a study of overburden integrity prior to any construction, with new development on the increase, Nixa city leaders have taken notice. The City is now beginning to consider regulations that would require a study of the structural integrity of the land under consideration for new development. (KY3)
On the east side of the state, the City of Cape Girardeau has been witnessing a steady increase in sinkhole activity, at an alarming rate. In April 2008, the city had recorded 20 new sinkholes over a nine-month period. According to Ken Eftnick, director of development services for the city, they “have been seeing one show up every week or so and don’t anticipate that changing anytime soon.” The sinkholes appear related, but the cause is still a mystery, and the concerns of property owners continue to mount. Utilities are already working to move lines to areas more structurally sound and the Burlington-Northern Sante Fe Railroad has installed ground movement sensors to alert oncoming trains if there has been significant disturbance to the integrity of the rails, and workers in the city have made efforts to stabilize and fill recent sinkholes. There really is no good way to fill a sinkhole though and be certain it will not reappear.
Currently, the biggest concern for the city is a wastewater treatment facility, which lies perilously close to the area that the collapses have been occurring. Widespread contamination of groundwater and ecosystems could occur if a sinkhole forms beneath this facility. Fortunately, the city has reached out to the U.S. Army Corps of Engineers, to help identify and propose solutions to the problem before such an eco-disaster happens.
It will be interesting to review the results of their research, especially since the City has chosen to ignore one of the prime suspects in the situation. Many of the sinkholes have been developing around the local Cape LeCroix Creek, which by way of infiltration, appears in the walls of nearby Buzzi Unicem quarry. At minimum, it seems rather obvious that intense vibrations from the blasting at the quarry, coupled with erosion from ground water movement, could be compounding the problem, if not creating it. When questioned about the significance of the quarry operation, the GIS Analyst for the City stated that they “do not believe that the operations at the quarry are contributing to the problem in any way,” and they “are not considering an investigation of the quarry.” (Anand) As the “biggest employer and highest taxpayer in Cape Girardeau,” (McNichol) this certainly raises the concern that the city could be ignoring critical evidence, as well as the safety of the public, in the interests of preserving their employment and tax base. It would not be the first time that a government entity has set aside public interest, in favor of business, and certainly will not be the last.
Identifying the immediate cause of sinkhole development could take years, though. Many of the factors that contribute to this problem are not constants, and persistent monitoring of them will be essential in obtaining a better understanding their significance. Ultimately, it is the responsibility of the property owner to do their best to protect themselves from naturally occurring phenomenon, such as sinkholes. However, community planners can also take steps to help property owners become more aware of the potential, and regulate to avoid unnecessary risk in areas that are at higher risk. This is particularly true for any development by utilities and businesses.
Sources:
- Currier, Joel. Sinkhole quickly drains 23-acre lake in Wildwood. Jun 11, 2004. St. Louis Post-Dispatch. http://www.ambrosiasw.com/forums/lofiversion/index.php/t44593.html (accesss 28 SEP 2008)
- (AP) Home swallowed by giant sinkhole. Columbia Daily Tribune. August 14, 2006. http://www.columbiatribune.com/2006/Aug/20060814News010.asp (accessed 28 SEP 2008)
- McNichol, Peg. Cape sinkhole total reaches 20 as five more appear. Southeast Missouri. April 28, 2008. http://www.semissourian.com/apps/pbcs.dll/article?AID=/20080413/NEWS01/780792621/0/NEWS03 (accessed 28 SEP 28) - photo used.
- Robinson, Jonathoan L. SCI Engineering, Inc. Press Release. August 22, 2006. http://www.sciengineering.com/pressrelease/Nixa%20sinkhole%20collapse%208-25.pdf (accessed 28 SEP 2008) - photo used.
- Latest sinkhole could cause change in Nixa building rules. KY3 News. April 7, 2008. http://www.ky3.com/news/local/17366234.html (accessed 28 SEP 08)
- Lake Chesterfield Sinkhole Formation. June 17, 2004. Missouri Department of Natural Resources (MoDNR) News release 176: Vol 32-176.
- http://www.dnr.mo.gov/newsrel/nr04_176.htm (accessed 28SEP08)
- Telephone Interview with City of Cape Girardeau GIS Analyst Arnand, Mar 2008
- Comer, Todd. Sinkhole Risk in Missouri. A GIS analysis of geology formations related to sinkhole development in Missouri. April 2008. (accessed 28SEP08)
GGP345 – Land Use Planning
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