Engineering and Environmental Issues
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Rock
Slides
Rock slides and falling rock are commonplace along road cuts after heavy rains
due to the instability of strata lying at a steep angle. The open pit gold quarry
of the Homestake Mining Company mine in Lead was closed recently due to the
danger of further rockslide
activity.
Flash
Floods
The narrow, steep valleys of
canyon creeks throughout the Black Hills are conducive flash flooding during
heavy rainstorms. A flash flood event occurred unexpectedly in Rapid Creek in
Rapid City in 1972 and resulted in loss of life and property.
Mine
Reclamation (Tour
Map symbol 'Re')
Reclamation activity on landscapes disturbed by mining operations or those in
which mining tailings
were deposited has received great attention because of it's potential to be
a non-point pollution source. Reclamation
activities are very costly yet mining companies are applying appropriate
resources to minimize environmental damage.
Sinkholes
(Tour
Map symbol 'Sk')
Landscapes where limestone and gypsum formations underlie the surface can form
sinkholes as these materials solubilize (Karst topography). Construction on
the Spearfish formation in the northern Black Hills on the soluble gypsum caps
poses a danger to structures since these areas are prone to sinkhole
formation.
Earthquakes
The landforms of the Black Hills are relatively stable but have not been so
in the past. Since 1872, about 10 earthquakes have recorded in the the Black
Hills area (see
SD Earthquake Map). Structural damage was minimal as all of these
were measured in the III-VI magnitude range of the Mercalli Intensity Scale.
Radon
Radon is a colorless, odorless, gas generated from the radioactive decay of
uranium. It has been implicated in the onset of lung cancer. Geological formations
which contain some uranium can generate radon. Several formations occur in the
Black Hills area which could generate measureable radon levels
(see Potential
for Radon Emission Map). If a
concern arises, an environmental engineer should be consulted to test specific
locations for radon levels.