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Alluvium (Qa)
Topography
The alluvium forms terraces and narrow floodplains of varying width
along streams. At least one well-developed terrace is generally present.
Hydrology
Alluvial sediments yield more than 500 gallons per day to nearly all wells drilled
along the Ohio River, with reported yields as much as 300 gallons per minute to
large industrial wells. Most wells dug in the alluvium of valleys tributary
to the Ohio River yield more than 100 gallons per day. Wells drilled and screened
in the alluvium of the Big Sandy River and its Tug and Levisa Forks
will probably yield as much as 20 or 25 gallons per minute.
Breathitt Group (Pbu, Pbm, Pbl)/Conemaugh Formation (Pmc) (Princess
Formation, Four Corners Formation, Hyden Formation, Pikeville Formation)
Topography
The topography of the Breathitt is rugged. Sandstone forms narrow valleys
and cliffs or steep slopes on hillsides, and shales form wide valleys
and moderate or gentle slopes on hills. The tops of hills and ridges
commonly are capped by sandstone.
Hydrology
These rocks yield more than 500 gallons per day to most of the wells
drilled in valley bottoms and half of the wells on hillsides, and smaller
quantities of water to wells on hilltops. Yields are slightly lower
in the eastern part of the county. The most common aquifers are sandstone
and shale, but coal supplies water to a few wells. Near-vertical joints
and openings along bedding plains yield most of the water to wells.
Waters are highly variable in chemical character. Wells may contain
salty water at depths less than 100 feet below the principal valley
bottoms.
Grundy Formation (contains Lee-type sandstone of the former Lee
Formation) (Plc)
Topography
Resistant sandstone beds 2 to 3 feet thick form steep-sided, rounded
hills and ridges.
Hydrology
In most of Carter County, yields are more than 500 gallons per day to
almost half the wells drilled in valley bottoms. Smaller quantities
of water are yielded to wells on hills. In the rest of the area, more
than 500 gallons per day is yielded to most wells drilled in valley
bottoms and to half the wells drilled on hillsides. Sandstone is the
principal aquifer, but shale yields water to some wells and coal to
a few. Vertical joints and openings along bedding planes, best developed
in sandstones, supply most of the water to wells. Intergranular openings
yield water to joints, and probably directly to some wells. Perched
and semiperched water tables are common. Water is moderately hard, and
sometimes contains noticeable amounts of iron. In some places, salty
water may be yielded to wells drilled below drainage level.
Slade Formation (Mn)
Topography
The Slade underlies valleys in Carter County. Limestone beds form steep
hillsides and prominent bluffs in sides of ridges and knobs that are
capped by Pennsylvanian rocks. Massive limestone forms cliffs and solution
features such as sinkholes, caves, and hanging valleys.
Hydrology
The Slade yields more than 500 gallons per day to over half of the wells
drilled in valley bottoms, and to many wells drilled on hills. It yields
little water where overlain by Pennsylvanian rocks. It may yield more
than 50 gallons per minute to a few wells penetrating large solution
cavities in limestone, the most common aquifer. Sandstone and shale
yield water from fractures to a few wells. Springs are common, particularly
at the head of streams; some springs from solution cavities near stream
level flow as much as 100 gallons per minute. Springs have large winter
and small summer flows. Water is hard.
Borden Formation (MDbb)
Topography
The Borden shale forms dissected slopes; massive siltstone forms cliffs.
Hydrology
The Borden yields 100 to 500 gallons per day to wells in valley bottoms.
It may yield more than 500 gallons per day to drilled wells in broad
valley bottoms from fractured sandy rocks near streams, but almost no
water to wells on hills. Water from wells drilled below stream level
may contain salt and sulfate less than 100 feet below the level of the
principal valley bottoms. Water from dug wells and small springs is
soft and has a low dissolved-solids content. Because much of this formation
is soft and silty, it has been well suited to the construction of dug
wells in the past.
The U.S. Geological Survey's Hydrologic
Atlas Series, published cooperatively with the Kentucky Geological
Survey, provides hydrologic information for the entire state.
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