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1
Introduction
. .
Surface mining of coal affects large areas in the
United States (3 million hectares so far).
Currently, this figure is increasing by about
150,000 hectares per year and could eventually
reach about 7 million hectares. Since 1977, when
Congress passed the Surface Mining Control and
Reclamation Act (SMCRA; P.L. 95-87), there have
been strict federal rules for restoring the land to
"approximately its original contours" and for
minimizing degradation of the quality of surface
and ground water (e.g., by controlling sediment
content and acid or alkaline drainage).
Although Congress's general goal in passing SMCRA
may appear fairly clear for the water-related
provisions, problems arise with some of the
specifics that Congress mandated. The general goal
is that in areas where there are usable surface
water and/or ground water resources, those
resources should be qualitatively and
quantitatively suitable for post-mining land use.
One of the specific provisions is the focus of this
report. Congress mandated that the "recharge ~
capacity" of the surface-mined lands be restored to
approximately pre-mining conditions. Congress
provided no definition of recharge capacity, nor
does one exist in either the legal or scientific
literature. Yet several things are clear about
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the recharge capacity requirement: (1) Congress
was thinking about ground water and not surface
water; ~ 2 ) this requirement was viewed as quantity
and not quality related; and (3) it was conceived
to prevent a lessened recharge capacity without
indicating any concern for an increased recharge
capacity .
Intuitively, recharge capacity could be
interpreted as the maximum capability of the land
surface and underlying materials (vadose zone or
unsaturated zone) to recharge ground water at some
maximum rate as if, for example? the land were
continuously flooded with water. The actual
recharge, however, is primarily controlled by the
climate (precipitation' evaporation from soil,
transpiration from vegetation) and by
rainfall-runoff relationships that may not be
adversely affected by the mining operation if the
land is properly restored and the vadose zones are
sufficiently permeable to transmit the water to
underlying aquifers.
Desert alluvial fans in the southwestern United
States have a high recharge capacity but very
little actual ground water recharge because of the
very low rainfall and high evaporation in those
areas. On the contrary, soils and geologic
profiles in more humid areas may be less permeable
and have less recharge capacity, but ground water
recharge rates are higher because of higher
rainfall and lower evaporation. Thus recharge
capacity, as such, is not a true indicator of
actual ground water recharge rates. As a matter of
fact, surface mining and restoration of the land
conceivably could reduce recharge capacity but
increase recharge of ground water, and vice versa!
A better term than "recharge capacity," therefore,
would simply be "ground water recharge." Tn the
context of SMCRA, this would mean that restoration
of surface-mined land must also restore long-term
average ground water recharge rates to at least
pre -mining levels ~ assuming, of course, that the
climate does not change).
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Ground water recharge rates typically are
expressed in centimeters or inches of water per
year. Rates vary from year to year as annual
rainfall (amount and distribution) and temperatures
vary. Rates also vary from location to location as
- ace; TV; ~C, ~T^~T^~-~;~= '^ - Harry Rear
~ a_. = ~ _~ i. Quantification
of ground water recharge from atmospheric
precipitation is difficult. Thus there is a
paucity of good data. Studies in various parts of
the world have shown that ground water recharge may
range from 50 percent of precipitation or more in
humid, temperate climates to 1 percent of
. . . ~ . ~ ~ · .
precipitation or less In cry, warm climates.
Regional ground water recharge rates can sometimes
be estimated from a simple analysis of rainfall,
evapotranspiration, and surface runoff data. Such
an estimate shows, for example, that the relatively
dry, coal mining area of Gillette, Wyoming, may get
less than 5 cm/year recharge out of 40 cm/year
precipitation, or less than 12 percent. For the
warm, humid area of Oak Ridge in eastern Tennessee,
evapotranspiration is 73 cm/year, leaving a total
recharge and runoff of 64 cm/year out of 137
cm/year precipitation, or 47 percent.
Ground water recharge rates are very difficult to
measure, and quantification may even be impractical
for operational purposes, such as restoring ground
water recharge rates to original levels after
surface mining of coal. A more practical approach
would be to require that surface-mined areas be
restored in such a manner that the factors
controlling ground water recharge are returned to
condition that produces ground water recharge at
rates that are not lower than those that existed
before mining
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a
Water quality considerations also are very
important. Depending on the particular geologic
materials and geochemistry, water percolating
through "reconstituted" vadose zones will leach
more chemicals than it did when it moved through
natural formations. In the eastern United States,
acid drainage and leaching of trace elements can be
a problem. In the western United States, salts,
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alkalinity, and leaching of trace elements are of
concern. Restoring ground water recharge becomes
meaningless if the quality of the resulting ground
water is so poor that it becomes useless or
degrades the quality of existing aquifers or
streams. Thus protection of ground water quality
in mined areas may actually require reduction of
post-mining recharge for specified subareas.
Aquifers differ in different coal mining
regions. In eastern Kentucky, "aquifers" may be
consolidated rock formations-that trap and convey
water in vertical stress-relief fractures so that
it may be pumped from small, mostly shallow,
domestic wells. When these fractures are replaced
by disturbed material due to surface mining and
restoration of the land, the original "aquifer"
system is also destroyed in the mine area. After
reclamation, aquifers will then form in
unconsolidated fill material. If local fracture
systems are drained, deeper aquifers may have to be
tapped if they are available. If coarser fill
materials are placed on the mine floor and the
finer ones on top, and if the fill is bowl-shaped
or has a controlled outlet so that water can be
stored in the coarse material, an "engineered"
aquifer can be created. This is being done, for
example, at the Starfire Mine in eastern Kentucky,
where the engineered aquifer also is connected to
the land surface with specially constructed rock
shafts to enhance ground water recharge. In large
coal fields of the West, the coal seams themselves
may be the major aquifers. Removing the-coal
seams, then, also removes the aquifers and replaces
them with mine spoil. If the lower layers of this
spoil become saturated, the spoils become the new
aquifers.
Apparently because of uncertainties about the
definition of recharge capacity and the method for
ascertaining or measuring its restoration, the
regulatory authorities responsible for the
implementation of SMCRA have generally not stressed
its implementation. Or at least it was perceived
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by some that this aspect of SMCRA was among
provisions not being implemented in Kentucky, the
top coal-producing state in the United States.
The supervisory agency for SMCRA is the Office of
Surface Mining Reclamation and Enforcement (OSM) of
the U.S. Department of the Interior. Basically OSM
has three roles to perform: (1) promulgation of
procedural and substantive regulations to carry out
the provisions in SMCRA; (2) oversight of state
administration of SMCRA and the regulations adopted
under SMCRA by those states that have assumed
primacy; and (3) administration of SMCRA and the
regulations adopted under SMCRA to coal mining
operations in those states that have not assumed
primacy.
It was alleged that the ground water recharge
capacity provisions of SMCRA were not being
addressed adequately in Kentucky. Because Kentucky
had been granted primacy, it was sued for this
alleged failure of administration and enforcement.
The OSM, in turn, was sued for a failure in
oversight. Eventually the suit against OSM was
dismissed when the Kentucky suit was settled and
OSM joined as a party to the settlement. That
settlement, known as the Kentucky Settlement
Agreement, included a requirement for hydrologic
balance among other items. A steering committee
was to be selected to advise OSM on a study of
hydrologic balance.
i__ _ =_ ~ , and specifically, that study
was to undertake to "identify . . . cost-effective
approaches to determination of the pre-mining
recharge capacity for both eastern and western
Kentucky coal field regimes." Thus at OSM's
request the Committee on Ground Water Recharge in
Surface-Mined Areas was established to clarify
issues associated with the requirement of restoring
"recharge capacity."
Therefore, as a result of the Kentucky Settlement
Agreement, this report was prepared to resolve a
scientific uncertainty, namely how to measure in an
efficient, cost-effective way whether the "recharge
capacity" restoration requirement has been
implemented. Before the scientific question can be
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addressed, it must be determined what "recharge
capacity" means. Thus a somewhat detailed
examination of the SMCRA language, its legislative
history, and prior interpretation of the recharge
capacity restoration provision follows in Chapter
2.
Representative terms from entire chapter:
water recharge
