Mined Land Reclamation Research:
Hydrology and Water Quality
By
Carmen T. Agouridis, Christopher D. Barton,
and Richard C. Warner
OVERVIEW
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Tree planting on surface mines returns economic and ecologic diversity to the
impacted areas.
High value hardwood forests provide opportunities for a growing wood industry and
potentials for employment of local residents.
Rapid growing trees sequester large quantities of carbon both above and below the
earth's surface.
High quality trees that are intensively managed and converted into furniture and
manufactured structures become long-term carbon sinks. Harvested areas with young
rapidly growing revegetation sequester additional carbon at more rapid rates than old
growth timber stands.
Timber stands provide for a variety of wildlife enhancements as it progresses from
initiation to maturity and again as it is regenerated.
Timber stands provide for a variety of recreation activities ranging from hiking,
camping and fishing to the development of resource-based resorts.
The level of compaction on reclaimed surface mine sites can be characterized by
physical measurements of bulk density and penetration resistance.
oo Compaction increases proportionally with the amount of grading.
oo Greater tree growth correlates with lower bulk density and greater
penetration depth.
Low compaction spoil placement and ripping of previously compacted spoils
provides a variety of substantial benefits.
oo Enhanced rainfall/runoff surface storage
oo Rapid infiltration
oo Smaller peak flows (reduced flooding)
ƒƒ Additional moisture for tree growth
ƒƒ Reduced runoff volume
oo Less erosion and improvement of overall stream water quality
The transpiration process associated with a forest is capable of removing large
quantities of CO2 and releasing O2 and results in higher quality air.
Uncompacted
Compacted
M I N ED LA N D HY D R OLOGY &
WATER QUALITY
Limited knowledge exists regarding the hydrologic system and associated water quality
from mined lands that have either been constructed with loose dumped spoil or reclaimed
through ripping. The traditional reclamation technique is to spread topsoil or soil
substitute material using large earth moving equipment, thereby creating a compacted
layer that inhibits tree establishment and growth. Grass cover is established and therefore
erosion is substantially reduced. Additionally, the site is aesthetically pleasing to many
regulators and others due to the grass cover. Unfortunately, such reclamation is
counterproductive to tree establishment and growth due to competition by grasses and the
highly compacted soil/spoil.
Some concern has been expressed about the 'moonscape' appearance of loose-dumped
spoil and ripped reclaimed areas. NGOs and selected regulators have expressed the
viewpoint that there is a greater propensity for much higher erosion rates and runoff
occurring from loose-dumped spoil and steep slope ripped areas compared to traditional
reclamation methods. Flooding in Eastern Kentucky surface-mined areas has been a
continuous problem, and therefore increased sedimentation of streams and higher peak
flows are always strongly addressed.
Based on preliminary applied research conducted at the University of Kentucky, it has
been determined that runoff and sediment rates are substantially lower for loose-dumped
spoil areas and ripped areas compared to traditional reclamation techniques.
The high relief landscape of loose-dumped spoil provides ample opportunities for:
• depressional storage of surface runoff enabling deposition of eroded soils,
• reduction of runoff potential, and
• provision of soil moisture for rapid establishment and growth of trees.
Thus, the opportunity readily exists for establishing an Appalachian forest after surface
mining.
HY D R OLOGI C &
SEDIMENTOLOGIC MONITORING
Monitoring Locations
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Eastern Kentucky
o 17 West near Inez, Kentucky in Martin County
o Starfire near Hazard, Kentucky in Perry County
o Bent Mountain near Meta, Kentucky in Pike County
o Robinson Forest in Breathitt County
Western Kentucky
o Peabody near Central City, Kentucky in Muhlenberg County
Monitoring Equipment
Monitoring stations, for the larger sites, consist of a recording rain gauge, trapezoidal
flumes with automatic stage recorders and automatic water quality samplers. Thus,
complete hydrographs, to determine rainfall – runoff and carbon relationships, are being
developed. Water quality sampling encompasses sediment, carbon and nutrients.
Similarly, for the smaller applied research sites runoff is recorded through recording
tipping bucket flow monitors that are capable of providing flow-proportional samples for
water quality assessments.
June 7, 2003
4
0.12
0.10
Runoff (cfs)
0.08
2
0.06
0.04
1
0.02
0
158.22 158.23 158.24 158.24 158.25 158.26 158.26 158.27 158.28
0.00
Julian Days
Rainfall
17West1
17West2
Preliminary Results
Preliminary results are quite promising! The loose-dumped spoil, on relatively flat
slopes, and ripped reclaimed areas, which were previously vegetated with grasses, are
providing a microclimate conducive to tree survivability and growth. Measured
infiltration rates are high, nearly as high as those found in established second-growth
forest, and peak flow and runoff volume are low resulting in low sediment production.
On steeper sloped lands there is a need for enhanced sediment control systems, at least
until trees are more established.
Cumulative Rainfall (in.)
3
GU Y C OV E
R ES TOR A TI ON P R OJ EC T
The mining technique of mountain top removal, and subsequent valley filling, a prevalent
practice in the Appalachian Coal Belt Region of eastern Kentucky, is detrimental to
headwater stream systems. With permitting for valley filling continuing to rise in eastern
Kentucky, the number of impacted headwater stream systems will likewise increase. The
watershed values (i.e. water storage, carbon sequestration, nutrient cycling, habitat, etc.)
provided by headwater stream systems are essentially lost once the valley is filled. The
development of practical stream reclamation techniques for post-mined lands is needed to
regain lost headwater stream system value. Important to note is that these techniques
must be 1) all encompassing of the valuable functions of headwater stream systems and
2) economically feasible for the mining companies to implement for both currently
constructed fills and for future fills (i.e. the techniques demonstrated will be readily
adopted).
Fortunately, an opportunity to develop head-of-hollow fill stream restoration techniques
is present at the University of Kentucky's Robinson Forest. Robinson Forest is an
approximately 15,000-acre teaching, research and extension forest administered by the
Department of Forestry at the University of Kentucky. Located in the rugged eastern
portion of the Cumberland Plateau and largely isolated from human activities, Robinson
Forest is unique in its diversity. During the 1990s, a section of Robinson Forest,
including the proposed restoration site at Guy Cove, was mined for coal. As part of the
mining process, a valley fill was created in Guy Cove, which impacted the headwater
stream system in that valley. While there was significant environmental loss, a unique
research and demonstration opportunity was created. Currently, the University of
Kentucky is negotiating a memorandum of agreement with Kentucky Fish and Wildlife to
conduct a restoration project at Guy Cove using mitigation dollars.
WA T E R Q U A L I T Y
Grab samples are being collected at four (4) locations in the Guy Cove watershed as well
as at two locations along Laurel Fork. The Guy Cove water samples are collected in the
headwaters of the watershed from an unmined section (GC 1), along the face of the fill at
the mixing zone for surface and subsurface waters (GC 2 and GC 3), and at the outlet of
the watershed prior to the waters entering Laurel Fork (GC 4). Water samples from
Laurel Fork are collected both upstream (LF up) and downstream (LF down) of the Guy
Cove outlet. A sampling station consisting of a stainless steel trapezoidal flume, ISCO
automated sampler, and miniTroll water level recorder has been established in the
headwaters of the watershed in the unmined portion to monitor storm events. A tipping
bucket rain gauge was installed in the Guy Cove to monitor rainfall prior to the addition
of a weather station.
Movement of water through the unconsolidated fill, and surface runoff to some extent,
has resulted in significant water quality problems for the watershed and downstream
environments (Tables 1 and 2). Specific conductivity (EC), chloride (Cl), sulfate (SO4),
calcium (Ca), magnesium (Mg), potassium (K) and sodium (Na) concentrations from
water samples in Guy Cove are well above that observed from a nearby reference
watershed (Little Millseat). The concentrations observed reflect a problem that is
prevalent throughout the mined portion of the Eastern Kentucky Coalfield. Of particular
concern are specific conductivity (or total dissolved ions) and manganese levels, which
are both above discharge water quality standards for active mine sites (Code of Federal
Regulations, 1996).
Evidence of erosion and deposition is common throughout the watershed. Fine-grained
sands have accumulated in low gradient areas and are the dominant bed feature in the
intermittent stream the flows along the crown of the hollow fill.
An iron rich flocculent is observable in waters emanating from the subsurface drains,
which indicates the presence and oxidation of pyrite (FeS2) in the watershed. Low pH
values are observed in areas where iron precipitation is evident. However, buffering
from high dissolved solid concentrations and subsequent alkalinity production has
maintained a neutral pH and limited trace element mobility from the overburden.
Analyses were below detection for arsenic (As), selenium (Se), lead (Pb), mercury (Hg),
cadmium (Cd), and chromium (Cr) in all Guy Cove water samples.
Table 1. Average Cation and Anion Concentrations in Water Samples from Restoration
Sites‡
EC
Cl
SO4
Mg
Ca
K
Na
Site*
μS
----------------------------mg L-1--------------------------------LM (30yr)†
46.9
0.6
10.4
1.8
2.3
1.3
1.1
LMpΔ
47.4
0.7
8.8
1.7
1.4
1.6
1.3
Δ
LMi
49.5
0.7
8.5
1.7
1.4
1.7
1.3
GC 1
439.0
1.2
168.4
37.9
30.5
8.2
5.9
GC 2
1987.2
2.6
1467.3
200.7
122.4
10.1
11.8
GC 3
1884.2
2.6
1282.5
185.4
115.6
10.0
11.3
GC 4
1935.8
2.4
1306.7
186.9
115.2
10.0
11.3
LF up
1885.6
2.2
1248.4
176.8
117.7
10.2
13.8
LF down
1872.4
2.2
1251.9
179.0
116.4
9.9
12.7
*LM =Little Millseat reference stream; GC = Guy Cove restoration stream; LF = Laurel
Fork stream, upstream and downstream of the Guy Cove outlet.
†
Average from weekly samples collected over a thirty-year period.
‡
Samples collected weekly during the period June – September, 2004.
Δ
p = perennial weir, i = intermittent flume.
Table 2. Average Nutrient and Metal Concentrations in Water Samples from Restoration
Sites.‡
pH
NO3
NH4
TOC
Alk
Fe
Mn
Site*
-1
su
----------------------------mg L --------------------------------LM (30yr)†
6.46
0.13
NA
4.99
17.70
--Δ
LMp
6.79
0.15
0.04
4.66
28.28
--LMiΔ
6.83
0.11
0.12
7.09
30.64
--GC 1
8.22
0.03
0.07
31.26
321.47
0.25
9.04
GC 2
6.62
0.02
0.10
7.36
74.16
3.55
30.61
GC 3
6.45
0.02
0.11
11.93
100.55
2.41
31.35
GC 4
7.06
0.02
0.09
9.62
88.48
0.25
30.27
LF up
6.80
0.04
0.15
10.73
75.87
2.61
16.34
LF down
6.89
0.03
0.12
9.15
82.05
1.82
23.49
*LM =Little Millseat reference stream; GC = Guy Cove restoration stream; LF = Laurel
Fork stream, upstream and downstream of the Guy Cove outlet.
†
Average from weekly samples collected over a thirty-year period.
‡
Samples collected weekly during the period June – September, 2004.
Δ
p = perennial weir, i = intermittent flume.
BEN T M OU N TA I N
INFILTRATION STUDIES
Often, natural channel design employees a technique in which the dimension, pattern and
profile of an "ideal" stream or reference reach is mimicked to create the new channel.
This technique is called an analog approach or "blueprint" approach. The crux of this
design technique is the ability of the designer to locate the "ideal" stream - such a stream
should have many similar characteristics (watershed area, valley type, geology, etc.) and
should be located in an adjacent or nearby watershed. However, mined lands particularly valley fills - present a unique challenge in that a reference reach is often
difficult to locate as the valley configuration is quite different. Adding to the challenge
of the design is the incorporation of habitat enhancement aspects, as water quality issues
are often the limiting factor.
As part of the conceptual design of the Guy Cove restoration project, research regarding
tree growth on loose spoil (tail dumped in accordance with RAM124) will be utilized.
While demonstration projects at Starfire and Bent Mountain are showing that high value
hardwood trees grow exceptionally well on loose spoil, question remain regarding the
rainfall-runoff or rather rainfall-infiltration response of this treatment - particularly
regarding the amount, timing and duration (by the very nature of the tail dump
configuration, surface runoff is negligible). Additionally, questions exist regarding the
sedimentological aspects of these tail dump systems as well as the functioning of these
systems in the carbon cycle (note that headwater systems are ecologically important in
that they supply organic matter to higher order stream systems). By gaining a better
understanding of the infiltration characteristics of the tail dumped spoil, the stream
restoration design at Guy Cove will be greatly enhanced.
To answer questions regarding the rainfall-infiltration response of tail dumped spoil
(three (3) types), the six (6) test plots at Bent Mountain have been equipped with
recording tipping buckets, some in the form of rain gauges. Collection of data regarding
volume, timing and duration of infiltrated rainfall has recently begun (note that the
infiltration data acquisition stations are in the final phases of completion). Additionally,
composite samples from each rain event are being collected (one composite sample per
tipping bucket for a total of 24 potential samples per rain event), and will be analyzed for
a number of constituents (e.g. sediment, pH, specific conductance, various metals).
B = Brown sandstone
B
G = Gray sandstone
M = Brown + Gray sandstone + Shale
G
B
Tail Dumped
Plots (RAM 124)
M
M
G
Plots separated by ~8 ft
(dozer blade width)
Direction of Flow
210’
High
Approx. 2% slope
PVC cap
Low
Direction of water flow
A
pp
ro
x.
2
%
sl
op
15’
210’
Pan lysimeters
Low
1” diameter PVC pipe
4” diameter PVC perforated pipe
Sample Station