Wayne County, Kentucky

KARST GEOLOGY

The term "karst" refers to a landscape characterized by sinkholes, springs, sinking streams (streams that disappear underground), and underground drainage through solution-enlarged conduits or caves. Karst landscapes form when slightly acidic water from rain and snow-melt seeps through soil cover into fractured and soluble bedrock (usually limestone, dolomite, or gypsum). Sinkholes are depressions on the land surface where water drains underground. Usually circular and often funnel-shaped, they range in size from a few feet to hundreds of feet in diameter. Springs occur when water emerges from underground to become surface water. Caves are solution-enlarged fractures or conduits

large enough for a person to enter.

This well-house is situated near a pond that is probably a "sinkhole pond", meaning that it is connected to the limestone aquifer by fractures in the bedrock, but is currently plugged with soil. Cattle feedlots or pastures near this well or pond can cause increased nitrate concentrations in groundwater. Photograph by Bart Davidson, Kentucky Geological Survey.

Cover-collapse inkholes such as this one may appear overnight when the soil plug at their base collapses into a fracture or cave in the underlying limestone. These are direct conduits to the local aquifer, and as such are susceptible to contamination by garbage dumping and accidental spills. They are also hazards to public safety. Photograph by Bart Davidson, Kentucky Geological Survey.

This pond was a sinkhole on dry land in the early 1970's, but filled with water in a few days after the sinkhole became plugged with clayey soil. Photo by Bart Davidson, Kentucky Geological Survey.

ENVIRONMENTAL PROTECTION

Never use sinkholes as dumps. All waste, but especially pesticides, paints, household chemicals, automobile batteries, and used motor oil, should be taken to an appropriate recycling center or landfill.

Make sure runoff from parking lots, streets, and other urban areas is routed through a detention basin and sediment trap to filter it before it flows into a sinkhole.

Make sure your home septic system is working properly and that it's not discharging sewage into a crevice or sinkhole.

Keep cattle and other livestock out of sinkholes and sinking streams. There are other methods of providing water to livestock.

See to it that sinkholes near or in crop fields are bordered with trees, shrubs, or grass buffer strips. This will filter runoff flowing into sinkholes and also keep tilled areas away from sinkholes.

Construct waste-holding lagoons in karst areas carefully, to prevent the bottom of the lagoon from collapsing, which would result in a catastrophic emptying of waste into the groundwater.

If required, develop a groundwater protection plan (410KAR5:037) or an agricultural water-quality plan (KRS224.71) for your land use.

(From Currens, 2001)

A small cave is located in Monticello across from the new courthouse. This cave was apparently used by the public in the past, and included a rock staircase and reflection pool nearby. It is now in a state of disrepair and marred by litter. Caves like this one are very susceptible to contamination from storm sewers, and are likely to be connected to the local aquifer. Photograph by Bart Davidson, Kentucky Geological Survey.

This sinkhole near the new courthouse in Monticello has been neglected. Sinkholes can be a source of contamination to local aquifers, and should also be carefully considered before building in the area. Photo by Bart Davidson, Kentucky Geological Survey.

CONSTRUCTION IN KARST AREAS

Cover-collapse sinkholes (outlined in red) are typical in areas of karst geology. Many sinkholes such as these have not been mapped. The construction implications of these features must be addressed for any type of development. Photo by Bart Davidson, Kentucky Geological Survey.

RESIDENTIAL CONSTRUCTION

Limestone terrain can be subject to subsidence hazards, which usually can be overcome by prior planning and site evaluation. "A" shows construction above an open cavern, which later collapses. This is one of the most difficult situations to detect, and the possibility of this situation beneath a structure warrants insurance protection for homes built on karst terrain. In "B," a heavy structure presumed to lie above solid bedrock actually is partially supported on soft, residual clay soils that subside gradually, resulting in damage to the structure. This occurs where inadequate site evaluation can be traced to lack of geophysical studies and inadequate core sampling. "C" and "D" show the close relationship between hydrology and subsidence hazards in limestone terrain. In "C," the house is situated on porous fill (light shading) at a site where surface and groundwater drainage move supporting soil (darker shading) into voids in limestone (blocks) below. The natural process is then accelerated by infiltration through fill around the home. "D" shows a karst site where normal rainfall is absorbed by subsurface conduits, but water from infrequent heavy storms cannot be carried away quickly enough to prevent flooding of low-lying areas. Adapted from AIPG (1993).

Karst topography is common in Wayne County, and is seen in this area of residential construction. Weathered limestone must be excavated to build houses, and sinkholes in this neighborhood have been filled with the excavated material. Photo by Bart Davidson, Kentucky Geological Survey.

RADON

Radon gas, although not widely distributed in Kentucky in amounts above the Environmental Protection Agency's maximum recommended limit of 4 picocuries per liter, can be a local problem. The bedrock composed of limestone/dolomite/shale in the county may contain high levels of uranium or radium, parent materials for radon gas. This rock and several other limestones in the state locally contain the phosphate mineral apatite. Uranium is sometimes part of the apatite structure, and when the limestone weathers away the phosphates containing uranium become concentrated in the soil and ultimately can give rise to high levels of radon. Homes in these areas should be tested for radon, but the homeowner should keep in mind that the health threat results from relatively high levels of exposure over long periods of time, and the remedy may simply be additional ventilation of the home.

EPA recommends action be taken if indoor levels exceed 4 picocuries per liter, which is 10 times the average outdoor level. Some EPA representatives believe the action level should be lowered to 2 picocuries per liter; other scientists dissent and claim the risks estimated in this chart are already much too high for low levels of radon. The action level in European countries is set at 10 picocuries per liter. Note that this chart is only one estimate; it is not based upon any scientific result from a study of a large population meeting the listed criteria. (From the U.S. Environmental Protection Agency, 1986.)

EROSION CONTROL

During construction, erosion-control fences such as these may be needed to prevent silt from entering local streams. Photo by

Bart Davidson, Kentucky Geological Survey.

Riprap drainage control and erosion protection. Photo by Stephen Greb, Kentucky Geological Survey.

GROUNDWATER

In the eastern half of Wayne County, most of the wells drilled in the valley bottoms are adequate for a domestic supply. Less than half the wells drilled on hillsides and hilltops are adequate for domestic needs.

In the western half of the county, about three-quarters of the drilled wells in the uplands yield enough water for domestic use. In low-lying areas, very few wells yield adequate amounts of water for a domestic supply. Some wells close to Lake Cumberland provide an adequate domestic supply, however, especially those that penetrate small solution openings within the limestone bedrock.

For more information on the groundwater resources of the county, see Carey and Stickney (2004).

A National Historic Site, Mill Springs is the location of one of the first important battles of the Civil War in 1862. It is named after 13 springs that feed a creek which powers the gristmill, constructed in 1839. The mill is still in operation, and is considered one of the largest in the world. Photo by Bart Davidson, Kentucky Geological Survey.

POND CONSTRUCTION

Successful pond construction must prevent water from seeping through structured soils into limestone solution channels below. A compacted clay liner, or artificial liner, may prevent pond failure. Getting the basin filled with water as soon as possible after construction prevents drying and cracking, and possible leakage, of the clayey soil liner. Ponds constructed in dry weather are more apt to leak than ponds constructed in wet weather. The U.S. Department of Agriculture--Natural Resources Conservation Service can provide guidance on the application of these liners to new construction, and for treatment of existing leaking ponds. Illustration by Paul Howell, U.S. Department of Agriculture--Natural Resource Conservation Service.

Dams should be constructed of compacted clayey soils at slopes flatter than 3 units horizontal to 1 unit vertical. Ponds with dam heights exceeding 25 feet, or pond volumes exceeding 50 acre-feet, require permits. Contact the Kentucky Division of Water, 14 Reilly Rd., Frankfort, KY 40601, telephone: 502.564.3410.

MAPPED SURFACE FAULTS

Faults are common geologic structures across Kentucky, and have been mapped in many of the Commonwealth's counties. The faults shown on this map represent seismic activity that occurred several million years ago at the latest. There has been no activity along these faults in recorded history. Seismic risk associated with these faults is very low. Faults may be associated with increased fracturing of bedrock in the immediately adjacent area. This fracturing may influence slope stability and groundwater flow in these limited areas.

THE LAND

Although located primarily in the Mississippian Plateau, Wayne County also has foothills of the Eastern Kentucky Coal Field, as seen in this photo. Landuse practices differ significantly in the more mountainous parts of the county. View looking south. Photo by Bart Davidson, Kentucky Geological Survey.

NATURAL RESOURCES

The lumber industry is a common land-use feature of Clinton County. Photo by Jeff Adams, Don Molden Multiple Services Inc.

AGRICULTURE

The majority of Wayne County's land use is agricultural, exemplified by this soybean crop. Best management practices are recommended to ensure that pesticide and fertilizer applications do not pose problems to the groundwater supply. Photo by Bart Davidson, Kentucky Geological Survey.