Hopkins County, Kentucky

GEOLOGIC HAZARDS

Hopkins County is located near the New Madrid and Wabash Valley Seismic Zones. Although the faults in the county are not considered active, precautions for earthquakes should be considered. Approximately 13 major earthquakes were recorded in the Madisonville area from 1974 to 2000. Earthquake prediction is not a defined part of seismology, but geologists and engineers know that earthquakes will cause damage, depending on magnitude, distance from the epicenter, and local geology. Areas of thick alluvium, lacustrine deposits, and other unconsolidated sediments are prone to the most damage because of ground-motion amplification and liquefaction. Liquefaction is the process which rock becomes saturated or loses shear strength, and is temporarily transformed into a fluid mass, resulting in structural damage.

Flooding is also a geologic hazard in Hopkins County. Areas underlain by alluvium are subject to regular flooding (Beck and others, 2004). The Green River borders the extreme northeastern part of the county and also has the potential for flooding. Urban development on or near both of these areas intensifies runoff, so flooding potential should be considered when planning.

Potential engineering problems can be associated with some clay shales beneath coals and with lacustrine deposits high in clay content. Small landslides and slumps occur locally on steep slopes where these deposits are prevalent. Where clay-shale deposits are overlain by massive sandstone, slumping is most common where joints in the sandstone parallel the slope. Excavations in shale, for roads or building foundations, may oversteepen the slope and undercut the overlying sandstone, causing slides to occur, especially when the material is saturated with water. Outwash and lacustrine deposits with high clay content present engineering problems because roads built on them tend to yield and push out under heavy traffic. Lacustrine deposits have good to poor compaction and moderate to high susceptibility to frost action. When the water table reaches the surface, the shrink-swell potential of lacustrine deposits is high.

Surface subsidence above abandoned underground coal mines has caused structural damage in parts of the county. When strata above mined-out coal beds collapse, resulting property loss can be substantial. If the overlying strata are not of sufficient thickness and strength, or the underclay is too soft, the result will be surface movement, causing structural damage (Sergeant and others, 1988). Structural damage and property damage can include cracks in foundations, cracks and depressions in roads, curvature of walls, collapse of buildings, and damage to utility lines. The areas of working or abandoned underground coal mines are shown on the map.

EARTHQUAKE HAZARDS

Peak ground acceleration at the top of rock that will probably occur in the next 500 years in Kentucky

Although we do not know when and where the next major earthquake will occur, we do know that an earthquake will cause damage. Damage severity depends on many factors, such as earthquake magnitude, the distance from the epicenter, and local geology. Information on earthquake effects is obtained by monitoring earthquakes and performing research. Such information is vital for earthquake hazard mitigation and risk reduction.

The most important information for seismic-hazard mitigation and risk reduction is ground-motion hazard. One way of predicting ground-motion hazard is by determining the peak ground acceleration (PGA) that may occur in a particular timeframe. The map above shows the PGA at the top of bedrock that will likely occur within the next 500 years in Kentucky (Street and others, 1996). It shows, as expected, that PGA would be greatest in far western Kentucky near the New Madrid Seismic Zone. Ground-motion hazard maps for the central United States and other areas are available from the U.S. Geological Survey. These maps are used to set general policies on mitigating damage. For example, maps produced by the USGS in 1996 were used to determine seismic design in building codes. For additional information pertaining to earthquake hazards visit the Kentucky Geological Survey website at www.uky.edu/KGS/geologichazards/geologichazards.html

WATER RESOURCES

Lake Pee Wee is a 420-acre-lake constructed in the early 1950’s to supply drinking water to the city of Madisonville. Currently, Lake Pee Wee provides drinking water to approximately 65 percent of the county. The lake holds 1.355 billon gallons of water and when necessary is recharged by pumping 9 million gallons of water per day from the Green River. Photo by Glynn Beck, Kentucky Geological Survey.

GROUNDWATER

About 2,300 people in Hopkins County rely on private domestic water supplies: 1,200 use wells and 1,100 use other sources. In Hopkins County, most wells that penetrate sandstones at depths of less than 300 feet are adequate for a domestic supply. In the areas surrounding Nortonville and south of Richland, most wells produce less than 100 gallons per day at depths of less than 300 feet. In southwestern Hopkins County, south of Charleston, a thin, highly faulted zone running east_west yields unpredictable amounts of water to drilled wells. Generally, groundwater is hard, and sometimes iron or salt may be present in objectionable amounts. Often groundwater becomes saltier with depth north of the highly faulted zone. For additional information, see Carey and Stickney (2001).

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.

COAL RESOURCES

Coal mining is a vital part of the Hopkins County economy. By 2000, approximately 5 to 10 million tons of coal has been mined in Hopkins County (both surface and underground). Original coal resources for the county are estimated to be 5 to 10 billion tons. Photo by Glynn Beck, Kentucky Geological Survey.

The Dotiki IV surface mine in Hopkins County, which is one of six surface mines owned by Dotiki in western Kentucky and southern Illinois. The facility was constructed in 2003, and mines the W. Kentucky No. 9 coal. In 2003, Dotiki Mines was the largest producer of coal in Kentucky and the largest non-longwall coal producer in the nation. Primary customers for coal produced at Dotiki are Seminole Electric, Tennessee Valley Authority, Louisville Gas & Electric, Western Kentucky Energy, Tampa Electric, and Henderson Municipal. Photo courtesy of Doug Blair.

AGRICULTURE

Traditional agriculture is a major part of the Hopkins County economy. Of the 353,433 acres in Hopkins County, 61,062 were used to grow corn, soybeans, and tobacco (Kentucky Agriculture Statistics, 2002–2003). Photo by Glynn Beck, Kentucky Geological Survey.

The presence of clayey to silty soils allows water to stand in row-crop fields. Fields are tiled in order to improve surface drainage in low-lying areas. Photo by George Kelley, Hopkins County Agriculture and Natural Resources agent.

Poultry-litter storage buildings are used to assist farmers in meeting nutrient-management and water-quality guidelines set by the Kentucky Agriculture Water Quality Authority. Currently, approximately 150 chicken houses are in Hopkins County, and each poultry farm has at least one litter storage building. The above building is located on the Doug Brown Farm. Photo by Glynn Beck, Kentucky Geological Survey.

Peppers (nontraditional crop) are growing next to burley tobacco (a traditional crop) on the Brumfield Farm. Commercial vegetable growing on black plastic with irrigation is just one of the non-traditional agricultural practices that have increased over the last 5 years in Hopkins County. Traditional agriculture such as corn, soybeans, and tobacco is still a major part of the Hopkins County economy, however. Photo by Glynn Beck, Kentucky Geological Survey.

PUBLIC HEALTH

The Trover Foundation and Regional Medical Center is located in Madisonville and is the largest employer in Hopkins County. The Regional Medical Center serves 12 surrounding counties in western Kentucky. Photo by Glynn Beck, Kentucky Geological Survey.