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
Alluvium yields more than 500 gallons per day to nearly all wells
drilled along the Ohio River; it is reported to yield as much as 360
gallons per minute to large industrial wells. Wells in the alluvium
of valleys that are tributary to the Ohio River yield more than 100
gallons per day. Wells drilled and screened in the alluvium of the Big
Sandy River probably will yield as much as 20 or 25 gallons per minute.
Breathitt Group (Pbu, Pbm)/Conemaugh Formation (Pmc) (Princess Formation,
Four Corners Formation, Hyden Formation, Pikeville Formation)
Topography
These rocks form rounded hills of moderate relief. The tops of hills
and ridges commonly are capped by sandstone. Shales form wide valleys
and moderate or gentle slopes on hills.
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 to wells on hilltops. The most common aquifers are sandstone
and shale, but coal supplies water to a few wells. Near-vertical joints
and openings along bedding planes yield most of the water to wells.
Waters are highly variable in chemical character. Salty water may be
found at depths less than 100 feet below the principal valley bottoms.
The U.S. Geological Survey's Hydrologic Atlas Series, published cooperatively
with the Kentucky Geological Survey, provides hydrologic information
for the entire state. Boyd County is included in HA-37
and HA-75.
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