Protecting a Karst Plain in Southwest Illinois - Investigations, Regulations, and Public Education.
Karst is a type of landscape in which the bedrock is made of soluble materials such as dolomite (calcium and magnesium carbonate) or limestone (calcium carbonate). Through time, rain and soil water draining down through cracks and crevices in the bedrock have dissolved, and will continue to dissolve, enough rock to form an underground network of conduits. Typical features of karst include sinkholes, springs, and disappearing streams. The Southwest Illinois Karst comprises a gently roiling sinkhole plain area located just southeast of St. Louis, Missouri. The area includes Monroe County, a major portion of Randolph County, and a small part of St. Clair County. Sinkhole density varies considerably. Substantial portions of the sinkhole plain are entirely internally drained, while other areas have a surface drainage component. The presence of large springs in areas of few sinkholes indicates that there is not a good correlation between a lack of sinkhole expression at the surface and the proportion of internal drainage.
Underlying the Southwest Illinois Karst is water-soluble carbonate bedrock. The formations that are of primary importance in terms of internal drainage are the St. Louis and Ste. Genevieve limestones. A significant erosion (karst) surface has formed on the limestone. The Paleozoic limestone is unconformably overlain by Pleistocene drift and loess (a loamy deposit) that mantles the bedrock surface. This mantling has obscured most of the bedrock topography. The loess is thickest (up to 50 feet) along the Mississippi River bluffs in the west and thins to the east. The authors believe that the bedrock has many karst features that are hidden beneath the mantle of loess but that may cause sinkhole development in the future. The loess is easily erodible and is conducive to the formation of soil pipes.
Statement of the Problem
Over the course of the past decade, tremendous population growth has occurred on the sinkhole plain. The gently rolling hills of the karst areas present a natural beauty that makes them highly desirable for residential development. The proximity to St. Louis is another desirable attribute. According to the U.S. Census Bureau, Monroe County had the highest growth rate of any county in the metro-east area between 1990 and 1995. The number of building permits issued for residential dwelling units increased by 269% between 1983 and 1993 (1). There are at least 45 platted subdivisions in various stages of development in the rural areas of Monroe County. All of these subdivisions are to be served by private sewage disposal systems on individual lots. Although many of these systems are installed in compliance with current regulations, they do not appear to be providing adequate treatment. In many cases, filtration of sewage before it enters the groundwater through sinkholes is inadequate. Private aeration systems for sewage treatment became popular about 1986 and are allowed to discharge to the ground surface in Illinois. Many systems installed in the 1980s discharge directly to sinkholes. Additionally, a majority of the homes in these subdivisions are served by private wells built in the St. Louis and Ste. Genevieve limestone formations. Currently, no regulations require casing in the dissolution zone of the bedrock. It appears that even the deep wells are not isolated from water entering the dissolution zone and that there is little to no filtration of the water recharging these wells. Well water sample data collected by the Monroe-Randolph Bi-County Health Department over the past 10 years show an increasing problem with unsatisfactory levels of bacterial contamination. In 1994, 71 percent of the wells showed unsatisfactory levels of bacterial contamination compared with 36 percent in 1986. In response to the realization that a groundwater contamination problem existed, a rural water district was formed to bring municipal water to a portion of the sinkhole plain. This only brought more problems. Rural development followed the water line extensions, compounding a problem the county was already facing, that of dealing with private sewage treatment in the sinkhole area.
The Mississippi Karst Resource Planning Committee was formed in 1991. The committee membership consists of concerned residents of Monroe, Randolph, and St. Clair Counties, including staff from the health department, the University of Illinois Cooperative Extension Service, the Soil and Water Districts, and the Natural Resource Conservation Service. The committee was formed after agencies and residents concluded that an educational campaign was needed to provide awareness about the problems of living and working in an environmentally sensitive area. A general lack of knowledge about karst hazards was found to exist within the community. The committee's goal is to educate, to create public awareness of water quality issues, and to implement groundwater protection strategies.
The Karst Committee has been very successful in its original goal of providing education to local people. In addition, a multitude of state and federal legislators, educators, and agencies have increased their knowledge about karst. Some of the committee's accomplishments are outlined below.
Groundwater Priority Protection Planning Area
The committee's efforts ensured that the Southwest Illinois Karst counties were included in the third Groundwater Priority Protection Zone designated by the Illinois Environmental Protection Agency (IEPA). Regional planning areas have been designated priority ground-water protection areas by IEPA in cooperation with the Illinois Department of Natural Resources (IDNR) through the Interagency Coordinating Committee on Groundwater (ICCG).
Spring and Well Testing
An intensive 12-month water quality testing study was conducted on six wells and six springs. The project was funded by the Illinois Department of Agriculture, Division of Natural Resources. The springs and wells that were tested were spread across the entire sinkhole plain. This was a preliminary evaluation of karst groundwater quality. The groundwater samples were analyzed for nitrates, 35 pesticides, and optical brighteners. Optical-brightener testing was completed only in springs because of the difficulty of sampling for them in wells.
Videos and Demonstration Stabilization
Two videos have been produced that target rural and urban audiences on the need to protect the groundwater in the karst area. The project also stabilized a demonstration sinkhole using new technology, new design criteria, and past landowner and contractor experience. These videos were funded by the U.S. Department of Agriculture National Resource Conservation Service, the Cooperative Extension Service, the Monroe County Soil and Water Conservation District, the Ciba-Geigy Corporation, the Monroe-Randolph BiCounty Health Department, and the Ozark Underground Laboratory. The videos were produced by the University of Illinois Office of Agriculture Communications and Education.
Water Quality Incentive Program
The Water Quality Incentive Program (WQIP) was approved for a select area of karst in Monroe County. This program provides incentive payments for management and cultural changes in farm practices that improve water quality.
The Karst Committee has conducted biannual tours of the sinkhole area. Each of the tours has targeted a different audience. The point of the tour is to raise awareness of the special problems associated with protecting groundwater in the karst area. Participants learn about groundwater contamination and how land use and daily activities contribute to it. Focus groups have included politicians, regulators, developers, the agricultural community, and students.
In April of 1995, the U.S. Environmental Protection Agency (U.S. EPA) awarded the Mississippi Karst Resource Planning Committee a Section 319 grant, administered by IEPA, in the amount of $324,500. The grant funds education and research in the Southwest Illinois Karst.
A full-time Karst educator has been hired to educate residents of the area about how their activities affect the quality of the groundwater. The educator has been producing and distributing fliers, handouts, and a newspaper pullout. The goal is to reach all stakeholders, whether they are working the land or just living on it. The educator also conducts public programs for specific audiences. This is a two-year position, and the committee hopes to extend it at least until the trend of degrading groundwater has been significantly reversed.
A nonpoint-source (NPS) pollution curriculum including student and instructor manuals and materials is being developed. The training program will deal specifically with karst groundwater pollution and pollution prevention for teachers. A karst water quality and NPS pollution prevention management manual is being produced, which will discuss effective best management practices and their appropriateness in reducing NPS pollution.
As a condition of the grant, the Mississippi Karst Resource Planning Committee is continuing to sponsor tours of the sinkhole plain. A tour was held on April 19, 1997, in conjunction with the Illinois State Geological Survey. Tour participants explored the sinkhole plain; learned how the sinkholes, caves, and vanishing streams of karst terrains are formed; and talked about protecting groundwater from contamination in a rapidly developing area where aquifers are extremely vulnerable. In the fall of 1997, the committee hosted a conference on the problems and the need for protection in the Southwest Illinois Karst. The target audience included local officials, developers, and landowners.
The research has focused on a specific study area within the Southwest Illinois Karst. The committee believed from the outset that the grant would not be large enough to conduct intensive studies throughout the karst, so a study area of a manageable size was selected. The area was chosen largely because it was experiencing high development pressure in combination with a high sinkhole density. The research comprises two basic areas: groundwater quality and springhead delineation.
The bulk of the groundwater quality research is being done by Southern Illinois University at Edwardsville. Groundwater is being monitored at 60 residential wells and five springs. The sampling is performed monthly, as well as during peak discharge during storm events spread throughout the 12-month data collection period. The research team is looking at several indicator parameters, specifically pH, conductivity, temperature, atrazine, optical brighteners, chloride, bromide, nitrate-nitrogen, and fecal coliform.
The springhead delineation is being done by dye tracing, and that work is being performed by the Ozark Underground Laboratory. Early dye-tracing results indicate more complexity in groundwater flow than anticipated.
Additional research is being done by a chemistry student at Purdue University who is independently sampling three additional springs for pH, temperature, specific conductivity, turbidity, and atrazine. The Illinois State Geological Survey is engaged in ongoing groundwater research in the karst and is publishing a series of papers about the results. The geological survey also has published a map titled "Karst Terrains and Carbonate Bedrock of Illinois" (2).
The committee intends to synthesize all these data and to reach conclusions about the state of interconnectedness between natural conduits (caves) and wells, and between land use and water quality. In turn, the committee will disseminate this information so that residents and regulators can make well- informed choices for the future and improve groundwater quality in the Southwest Illinois Karst. The committee hopes that the existing research efforts will stimulate others to conduct additional studies in the area.
As a result of development pressures along the initial phase of the rural water district lines, Monroe County adopted a revised Comprehensive Development Plan and revised health, zoning, and subdivision ordinances in an attempt to deal with the sinkhole issue. A section on Karst topography was included in Monroe County's comprehensive plan. A map delineating the sinkhole plain areas was also incorporated.
A definition for the term sinkhole was added to all the county ordinances. A sinkhole is defined as follows: "any natural depression formed as a result of subsurface removal of soil or rock materials and causing the formation of a collapse feature that exhibits internal drainage. The existence of a sinkhole shall be indicated by the uppermost closed depression contour lines on the USGS 7.5 minute quadrangle topographic maps or as determined by field investigations" (3). The definition was chosen by a consensus of committee members, including regulators, county officials, realtors, developers, and bankers.
The Monroe County Subdivision Ordinance was revised to require that subdivisions with 10 or more lots of 2.5 acres or less install a central sewage collection system (4). A community shared-maintenance program is required to ensure that the system and components are continuously maintained and functioning.
A "Karst Topography Regulations" section was added to the Monroe County Zoning Ordinance. The ordinance changes were patterned after the regulations adopted in Greene County, Missouri. A section stating that any property on which a sinkhole has been used as a site for dumping trash, garbage, or refuse will be prohibited from obtaining building permits, zoning change requests, or land subdivision approvals until the sinkhole has been cleaned out and approved by the Bi-County Health Department. No building construction will be permitted in a sinkhole unless the site plans are approved by the county engineer. Many committee members were not satisfied with the allowance of an exemption by the county engineer; however, the compromise made it possible to get the ordinance passed.
The Illinois Department of Public Health Private Sewage Disposal Licensing Act and Code was revised in 1996. The word "sinkhole" was added to the Prohibited Discharges section of the code, which now states: "Domestic sewage or effluent from any private sewage disposal system or component shall not be discharged into any well, cistern, basement or into any underground mine, cave, sinkhole or tunnel."
The Monroe and Randolph County Health Ordinances were revised in an attempt to better dean with the issue of private sewage disposal in karst areas. A revised ordinance was adopted on November 21, 1994, in Monroe County, and the same ordinance was adopted shortly thereafter in Randolph County. The following definitions were included in the ordinance:
* Immediate sinkhole drainage area shall mean any area that contributes surface water directly to the sinkhole(s); this does not include areas that contribute surface water indirectly to a sinkhole (via streams).
* Lower elevation segments of sinkholes shall include the floor of the sinkhole and sides of the sinkhole up to a point where the slope of the sinkhole side is less than five percent.
* Sinkhole is defined as in Monroe County's Comprehensive Development Plan (see above) to maintain consistency throughout county ordinances.
* Upper elevation segments of sinkholes and sinkhole divides shall mean areas having slopes of less than five percent but does not include the bottoms of sinkholes or subsidiary sinkholes within compound sinkholes (5).
It is a requirement of the ordinance that any subsurface seepage system installed in a karst soil mapping unit, as defined by the National Resource Conservation Service in the Monroe County Soil Survey, be sized based on the results of an on-site soil investigation performed by a certified soil classifier - and not by a percolation test. No private sewage disposal systems or components are permitted within the lower elevation segments of sinkholes. Systems with surface discharges are not permitted within 50 feet of an immediate sinkhole drainage area. The immediate sinkhole drainage area is the ground surface area that provides drainage to the sinkhole. Surface discharge systems will not be permitted in the sinkhole plain areas. This refers to areas where all of the surface drainage becomes subsurface. Subsurface seepage fields are not permitted within 75 feet of the point where the slope of a sinkhole side exceeds 5 percent.
These regulatory measures are certainly a step in the right direction, although there is some uncertainty about their effectiveness. The studies being conducted through the Section 319 grant and others should provide data that indicate how effective the regulations are.
Progress is being made in understanding groundwater quality and behavior in the sinkhole plain. Much work remains to be done. The Mississippi Karst Resource Planning Committee strongly encourages interested researchers to conduct additional studies in the Southwest Illinois Karst. The committee would be happy to share its educational materials with interested parties. Karst education needs to be an ongoing function in Southwestern Illinois. Efforts must be made to educate all stakeholders about the impacts of their land use activities on groundwater quality.
(Adapted with permission from: Beck, Barry F., J. Brad Stephenson, and J. Gayle Herring (eds), The Engineering Geology and Hydrogeology of Karst Terranes - Proceedings of the Sixth Multidisciplinary Conference, Springfield, Missouri, April 6-9, 1997. 528 pp., Hfl.210/US$105.00. Please order from: A.A. Balkema, Old Post Road, Brookfield, Vermont 05036. Phone: (802) 276-3162; fax (802) 276-3837; email firstname.lastname@example.org)
1. Southwestern Illinois Metropolitan and Regional Planning Commission (1994), Monroe County, Illinois, Comprehensive Plan, Waterloo, Ill.: Monroe County Courthouse.
2. Weibel, C.P., and Panno, S.V. (1997), "Karst Terrains and Carbonate Bedrock of Illinois," I-Map Series, Champaign, Ill.: Illinois State Geological Survey.
3. Monroe County, Illinois (1996), Zoning Ordinance, Waterloo, Ill.: Monroe County Courthouse.
4. Monroe County, Illinois (1995), Subdivision Ordinance, Waterloo, Ill.: Monroe County Courthouse.
5. Monroe County, Illinois (1994), Chapter 18, "Health Code, Article IV," Ordinances, Waterloo, Ill.: Monroe County Courthouse.
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|Publication:||Journal of Environmental Health|
|Date:||Apr 1, 1998|
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