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OCR for page 95
Conclusions and Recommendations
The committee's mission was basically to assist
the Office of Surface Mining Reclamation and
Enforcement (OSM) concerning interpretation of the
term "ground water recharge capacity" in the
context of the Surface Mining Control and
Reclamation Act of 1977 and to advise OSM in regard
to its estimation or assessment before and after
mining. The committee expresses the results of its
deliberations in terms of the following several
sets of conclusions and recommendations that
correspond generally to the items of its charge,
outlined in the Preface. These conclusions and
recommendations are of three general types: (1)
those that should clarify the meaning of the term
"ground water recharge capacity"; (2) those that
should provide operational guidance to the OSM and
their constituents; and (3) those concerning
research and development that may produce more
long-term and general benefits to the evaluation of
the hydrologic functions of surface-mined areas in
the future.
GROUND WATER RECHARGE CAPACITY INTERPRETED
CONCLUSION:
"Ground water recharge capacity"~has no clear
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scientific meaning. This committee's legal
interpretation is that the term means ground water
recharge capability, as concluded in Chapter 2.
Again, this term has no scientific definition but
is an indicator of the "ability of soils and
underlying materials to allow precipitation and
runoff to infiltrate and reach the zone of
." Notwithstanding the issue of
definition, for reasons stated in Chapter 1 both
terms ("capacity" and "capability") are nebulous
and are poor indicators of actual ground water
saturation "
recharge.
RECOMMENDATION:
For the above reasons, the term "ground water
recharge capacity" should be interpreted to mean
ground water recharge, which is the movement of
surface water to ground water or the addition of
precipitation or surface water to ground water, the
real issue of concern. The rates of this movement
are controlled by precipitation, infiltration,
surface and subsurface runoff, evapotranspiration,
and site stratigraphy and structure. All of these
parameters exhibit spatial and temporal
variabilities, making accurate measurement of pre-
and post-mining recharge rates for mine-scale areas
difficult.
HYDROLOGI C EVALUATIONS
CONCLUSION:
The several parameters relevant to ground water
recharge can, in principle, be measured for a given
point. However, spatial and temporal variabilities
would require intensive instrumentation at high
costs, and these variabilities and the uncertainty
in measurement techniques would generally preclude
accurate extrapolation to mine-scale areas.
Nonpoint methods for estimating ground water
recharge, made by hydrograph separation, tracer
techniques, and regional water budgets, are also
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not exact. The errors in resulting estimates of
ground water recharge may exceed the change in
recharge due to mining.
RECOMMENDATION:
No single technique or set of techniques for
assessing recharge at
required as rat
provision of SMCRA.
v surface coal mines should be
Dart of the "recharge-cacacitY"
CONCLUSION:
Although accurate determination of differences
between pre- and post-mining recharge rates is not
practical, the committee concluded that enforcement
of existing OSM regulations concerning mine
reclamation will, in the vast majority of
situations, result in post-mining recharge rates
that equal or exceed pre-mining rates. This
conclusion is based on the following currently
required conditions:
1. The land surface is recontoured and
stabilized to the approximate pre-mining
topography; '
the committee concluded
2. The site is typically revegetated with plants
using less or approximately the same quantity of
water as the pre-mining species;
3. Compaction of surface soils and vadose zone
materials Is avolueu; and
4. Restricting layers in the original vadose
~ ~ ~ ~ the
zone are broken up and alspersea in
reconstituted vadose zone by the mining and
reclamation process.
RECOMMENDATION:
No additional instrumentation and measurement,
over and above that already required by other
sections of the SMCRA and justified solely on the
grounds of establishing whether or not differences
exist in pre- and post-minin~ recharge, should be
required as part of
surface coal mining, because Suck measurement
cannot be justified rationally given the present
state of recharge measurement technology.
~ ~ ,
the permitting process for
. . .
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CONCLUSION:
Isolation practices can be implemented to
preserve water quality in surface mine restoration
projects. These practices can have an impact on
the process of ground water recharge.
RECOMMENDATION:
When practices implemented to preserve water
quality substantially reduce recharge over a given
area, recharge should be restored through other
areas that are especially engineered to assure good
quality and quantity of water. But if isolation
practices substantially reduce mine-site recharge
and this recharge cannot be restored by engineered
zones, the area should be reconsidered in respect
to its suitability for mining. There is an
"unsuitable-for-mining" provision of SMCRA (Sect.
5221.
CONCLUSION:
The impacts of mining on the hydrology of a
region with many mining operations may be
substantial but are currently not well known,
because cumulative hydrologic impact studies
currently are difficult to conduct in a meaningful
manner due to the lack of a central digitized data
base.
RECOMMENDATION:
Each state regulatory authority should be
encouraged to produce and maintain a Geographic
Information Systems data base of all mined areas
Such data bases should be uniform across states.
RESEARCH AND DEVELOPMENT
.
CONCLUSION:
The long-term cumulative consequences of large
surface coal mining projects on the ground and
surface water parameters are unknown.
RECOMMENDATION:
A long-term research program of hydrologic
monitoring should be provided for such sites. This
monitoring may have to continue well beyond the
current bond-release dates.
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CONCLUSION:
No single current technique or combination of
current techniques can provide a sufficiently
accurate characterization of ground water recharge
at mine scale. Improvement in our ability to
determine site recharge rates is needed to allow
for better quantification of pre- and post-mining
hydrologic systems so as to improve our ability to
predict the effects of mining and reclamation on
the surface and ground water resources of an area.
RECOMMENDATION:
Research should be undertaken in eastern and
western coal provinces to help improve our
understanding of the recharge process, its spatial
and temporal variability, and the accuracy of
individual measurement techniques.
CONCLUSION:
Issues of hydrologic balance, recharge, and pre-
and post-mining monitoring need to be addressed in
a more coherent hydrologic framework.
RECOMMENDATION:
In conjunction with research to improve
hydrologic methods and information, annual water
budgets should be developed based on available
monthly records representative of the pre-mining
landscapes in the permitting areas. Several water
budgets may be needed because the rates and timing
of recharge can differ between and within the coal
mining areas of each state. As part of each permit
application, the applicant should qualitatively
describe the anticipated changes in water-budget
components (evapotranspiration, runoff,
infiltration, soil water storage, drainage, and
recharge) during mining operations and the
reclamation period. (A written review of the
reclamation project could take place at the time of
bond release.) All the above data should be
incorporated into the above mentioned Geographic
Information System data base for use in subsequent
cumulative hydrologic impact studies.
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CONCLUSION:
Soil compaction can be a major factor affecting
the restoration of the recharge process in a
reclaimed landscape.
RECOMMENDATION:
Innovative methods should be developed for
overcoming compaction problems in reclaimed spoil
materials and minesoils, particularly in
surface-mined areas with identified compaction
problems.
Representative terms from entire chapter:
water recharge
