Russell 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.
Sinkholes such as this one
(right center) may appear overnight when the soil plug at their base collapses
into a fracture or cave in the underlying limestone. Photo by
Bart Davidson,
These cattle are resting
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 plugged with soil. Cattle
feedlots or pastures such as this can cause increased nitrates in groundwater
if the ponds or feedlots drain into the aquifer. Photo by
Bart Davidson,
Cover-collapse sinkholes 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,
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)
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,
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).
SWELLING SHALES AND SOILS
A
problem of considerable concern in this area is the swelling of some of the
clay minerals in shales. This process is exacerbated
when the shale contains the mineral pyrite (fool's gold), such as is the case
in the Chattanooga Shale. Pyrite is a common mineral and can be found distributed
throughout the black shale, although it is not always present and may be
discontinuous both vertically and horizontally. In the presence of moisture and
oxygen, pyrite oxidizes and produces sulfuric acid. The acid reacts with
calcium carbonates found in water, the rock itself, crushed limestone, and
concrete. This chemical reaction produces sulfate and can form the mineral
gypsum, whose crystallization can cause layers of shale to expand and burst,
backfill to swell, and concrete to crack and crumble. It can heave the
foundation, the slab and
interior partitions resting on it, and can even damage upper
floors and interior partitions. This phenomenon has been responsible for
extensive damage to schools, homes, and businesses in
We
strongly suggest that anyone planning construction on these shales
seek professional advice from a geologist or engineer familiar with the problem.
The
Chattanooga Shale, is the equivalent of the New Albany
Shale in
RADON
Radon
gas, although not widely distributed in
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,
Riprap
drainage control and erosion protection. Photo by Stephen Greb,
GROUNDWATER
In the northwestern third of
For more information on the
groundwater resources of the county, see Carey and Stickney (2004).
A cattle watering trough,
probably fed from the nearby water well. Such wells are often the most
economical source of water for rural communities. Photo by
Bart Davidson,
SOURCE WATER
PROTECTION AREAS
In
source-water protection areas, activities are likely to affect the quality of
the drinking-water source. For more information, see kgsweb.uky.edu/download/water/swapp/swapp.htm.
WATER RESOURCES
Constructed between 1941 and
1950, Wolf Creek Dam is a comprehensive flood-control system for the
Wolf Creek National Fish
Hatchery, located next to Wolf Creek Dam, produces over a million pounds of
trout annually. Water feeding the hatchery comes from
A power transmission line
from nearby Wolf Creek Dam crosses southern
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
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
MAPPED SURFACE FAULTS
Faults are common geologic
structures across
TOURISM
The Creelsboro
Arch, locally known as the Rockbridge, in southwestern