Document ID: EPA-HQ-RCRA-2008-0329-0200
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2009-01-02T05:00Z

Powell River Project

Reclamation Guidelines for Surface-Mined Land in Southwest Virginia

Reclamation of Coal Refuse Disposal Areas 

Authors: W. Lee Daniels, Associate Professor, and Barry Stewart and
Dennis Dove, Graduate Research Assistants, Department of Crop and Soil
Environmental Sciences, Virginia Tech 

Publication Number 460-131, June 1996 

 

Table of Contents

   HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L3#L3"  Coal Refuse Properties and Reclamation Success  

  HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L4#L4"  Geologic Considerations and Prep Plant Influences  

  HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L5#L5"  Inherent Variability  

  HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L6#L6"  Slope and Aspect Effects  

  HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L7#L7"  Pyrite Oxidation and Potential Acidity  

  HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L8#L8"  Acid Seepage and Leachate Production  

  HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L9#L9"  Spontaneous Combustion  

  HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L10#L10"  Low Fertility  

  HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L11#L11"  Moisture Retention, Rooting Depth and Compaction  

  HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L12#L12"  High Surface Temperature  

   HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L16#L16"  Guidelines for Refuse Area Revegetation in Southwest Virginia
 

  HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L17#L17"  Refuse Characterization  

  HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L18#L18"  Site Preparation  

  HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L19#L19"  Fertilization  

  HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L20#L20"  Seeding Rates and Species Mixtures  

   HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L25#L25"  Acknowledgments  

   HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/460-131.html" \l
"L26#L26"  References 

Introduction

Stabilization and reclamation of coal refuse disposal piles and fills is
a costly and challenging problem facing the Appalachian coal industry
today. Coal refuse disposal areas are also known as "gob piles," "slate
dumps," "waste piles," and "refuge." The exact acreage of coal refuse in
the Appalachian coal fields is difficult to estimate, but active
disposal facilities (see   HYPERLINK
"http://www.ext.vt.edu/pubs/mines/460-131/figure1.html"  Figure 1  )
cover thousands of acres and abandoned refuse piles dot the landscape in
almost every major watershed. Annual production of coal refuse exceeds
15 million tons in Virginia alone. 

This publication reviews problems associated with stabilization and
revegetation of coal refuse disposal areas and suggests strategies for
their successful long-term reclamation and closure. The primary focus is
establishment of vegetation, but other refuse stabilization issues are
discussed. The reader is encouraged to consult the papers and reports
cited in the bibliography for specific details and technical data. The
regulatory framework discussed in this paper is specific to Virginia,
but it is similar to that of other coal mining states in the Appalachian
coal region. 

Modern coal cleaning technologies have allowed coal preparation
facilities to become quite efficient at removing sulfur compounds, waste
rock and low grade coals from run-of-mine coal. Up to 50 percent of the
raw mined product may end up as refuse, particularly when the coal
originates from longwall mining operations or is high in partings, rock,
and impurities. The refuse materials vary from coarse fragments removed
by physical screening to very fine materials removed by flotation and
density separation processes. 

The potential hazards of improperly reclaimed refuse include
contamination of surface and groundwaters by acidic leachates and
runoff, erosion and sedimentation into nearby water bodies, spontaneous
combustion, and damage from landslides. While these problems were common
on refuse piles constructed prior to the 1970s, modern regulations
attempt to minimize the environmental impact of coal refuse disposal.
Several, if not all, of the problems associated with coal refuse piles
can be reduced significantly by the maintenance of a viable plant cover.
A vigorous plant community can reduce water and oxygen movement down
into the fill, thereby limiting the production of acidic leachates,
while reducing sediment losses and stabilizing the fill surface.
Establishment and maintenance of permanent vegetation on refuse,
however, is complicated by physical, mineralogical, and chemical
factors. 

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Table of Contents  

Regulatory Framework and Reclamation Strategies

Reclamation standards for refuse disposal in Virginia are set forth in
the Permanent Regulatory Program of the Virginia Division of Mined Land
Reclamation (VDMLR). The state regulations and performance standards are
subject to oversight and review by the U.S. Office of Surface Mining
Reclamation and Enforcement (OSMRE) and must meet the minimum standards
set forth in the federal Surface Mining Control and Reclamation Act
(SMCRA) of 1977. An important aspect of these regulations is the 5-year
bond liability period. Before reclamation bond monies are completely
released, refuse disposal areas must support self-sustaining vegetation
for a minimum period of 5 years after closure. Leachate and runoff must
meet water quality standards for this same period, and there must be
evidence that water quality will not degrade over the long term. 

Refuse disposal areas are generally constructed as large valley fills,
with surface waters diverted around or through drains under the
completed fill. These fills are commonly hundreds of acres in size and
are perched in the headwaters of many watersheds. The refuse is
compacted in place, and the entire fill must meet rigorous geotechnical
stability standards. Many refuse disposal areas are constructed using a
"zoned disposal" concept where refuse slurry generated in the fine coal
cleaning circuit is impounded behind a compacted dam of coarse refuse.
The face and sideslopes of the fills are generally constructed to a
steep gradient to minimize the total disturbed area, and these steep
slopes greatly complicate reclamation. Most fills are designed for a
lifetime of tens of years. Therefore, many active fills were designed
before current regulations were in force. 

Once the fill is completed, regulations require that "the site shall be
covered with a minimum of 4 feet of the best available non-toxic and
non-combustible materials." Less than 4 feet of alternative materials
may be used if chemical and physical analyses indicate its properties
are conducive to establishing a permanent vegetative cover, and the
applicant can prove that the standards for revegetation success can be
met. Thick topsoiling is quite costly and may be impractical in areas
where native soils are shallow. Extensive topsoiling also creates the
problem of reclaiming the borrow areas. 

Coal refuse disposal areas are required to meet the same standards for
revegetation success following the 5-year bond liability period as
surface mined sites. Topsoiling may be the only option available on some
sites, due to toxic properties of the materials, but direct seeding
appears to be a viable alternative for many refuse materials. Documented
field trials have generally been required to evaluate the suitability of
refuse materials as a plant growth medium, since reliable laboratory
testing methods correlated with plant growth response have not been
available. It is our belief, however, that many coal refuse piles can be
successfully direct seeded by following the procedures outlined in this
paper without long-term dedicated on-site experimental trials. 

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Table of Contents  

Coal Refuse Properties and Reclamation Success

The long-term stability of any reclaimed coal waste pile is largely
dependent upon the ability of surface treatments (including soil cover)
to establish a favorable plant rooting environment. Failure to maintain
long-term vegetation results in excessive erosion and gullying. Lack of
a plant cover will also cause subsurface water contents and leachate
production to increase, due to lack of rain interception by the plant
canopy and decreased plant transpiration. The key to developing
successful long-term reclamation strategies is an understanding of the
nature and variability of the coal refuse materials and how they will
respond to various treatments over time. Long-term closure planning must
also consider the potential of the pile to generate acid mine drainage
(AMD). 

Many factors influence the reclamation potential of a given coal waste
pile, including the geologic source of the refuse, the prep plant
processes, and local site conditions. The following sections summarize
properties and conditions known to influence refuse pile reclamation and
surrounding environmental quality and relates them to reclamation
planning. 

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Table of Contents  

Geologic Considerations and Prep Plant Influences

The depositional environment of coal and its associated strata has a
direct relationship to the properties of the coal seams, including coal
bed thicknesses, sulfur and trace element content, and coal quality. The
correlation of paleoenvironment and coal properties has many important
applications to both the mining and use of coal, and to investigations
into the nature of the wastes produced by mining. Although coal refuse
will share many characteristics with the associated coal seams, coal
refuse properties are also influenced by mining, coal cleaning, and
geochemical weathering processes. 

Coal refuse is usually composed of rock fragments derived from interseam
shale or siltstone partings and waste rock materials from above or below
the seam. The refuse shares many properties with the associated coal
seam. For example, some coal seams are inherently high in sulfur (i.e.
the Pittsburgh seam of Northern Appalachia ), some are low in sulfur
(the Pocahontas seam of the South Central Appalachian Basin), and some
are variable. Southwest Virginia coal seams and associated strata are
generally low in sulfur compared to other Appalachian states. As a
result, Virginia coal refuse tends to be comparatively low in sulfur and
associated potential acidity (see   HYPERLINK
"http://www.ext.vt.edu/pubs/mines/460-131/table1.html"  Table 1  ). 

The processes utilized in the prep plant also influence the physical and
chemical properties of the refuse stream. Some prep plants re-combine
coarse and fine refuse fractions before disposal, while others dispose
of these fractions separately or in zoned fills. Our work has focused on
the reclamation of coarse refuse and re-combined refuse materials, and
not upon slurry impoundments. The approach to reclaiming slurry
materials would be similar to that described here, once the surface has
stabilized. 

The content and reactivity of pyritic sulfur exert a dominant influence
on refuse chemical properties over time. The efficiency of a preparation
plant at removing sulfur from the marketed coal and the degree to which
the sulfide fragments are fractured and reduced in size influence the
reactivity and potential acidity of the final refuse product. Numerous
reagents and additives such as cationic surfactants, fuel oil, and
strong bases are used in various separation processes and also end up in
the refuse stream to some extent. The influence of these additives on
the revegetation potential of fresh refuse has not been studied. 

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Inherent Variability

A high degree of variability often exists in refuse materials within the
same disposal area, since individual prep plants often process several
coal seams. Each seam may exhibit different mineralogical, chemical, and
physical properties. This variability makes the development of uniform
reclamation strategies difficult. Additional variability is introduced
through weathering. Because coal refuse materials are primarily fresh
unweathered geologic materials which have been subjected to severe
treatment during processing, sharp changes in physical and chemical
properties are common in short periods of time. The pH of fresh refuse
can change dramatically in a short period. We have observed the pH of a
fresh, high sulfur refuse change from 8 to 3 within a single month. 

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Slope and Aspect Effects

Modern refuse piles are engineered to maximize volume capacity while
minimizing "footprint," or land area occupied. Minimizing acreage
necessitates the construction of steeply sloping embankments; these tend
to be heavily compacted so as to maintain surface stability. Steep
slopes complicate revegetation efforts in several ways. First, it can be
very difficult to apply and incorporate soil amendments such as
agricultural lime on steep slopes. Secondly, the steep slopes enhance
rainfall runoff which leads to droughty soil conditions. This soil water
supply problem is further compounded by the compaction mandated to
achieve slope stability. Finally, the micro-climate of steeply sloping
areas will be strongly influenced by aspect. South-facing fill slopes
will be extremely hot in the summer while north-facing slopes are cooler
and moister. Thus, regulatory and economic design pressures to limit the
"footprint" of disturbance greatly complicate long-term stabilization
and revegetation of refuse fills. 

Older piles, which pre-date the enactment of SMCRA and VDMLR
regulations, often have steeply sloping sides which remain uncompacted.
The surfaces of these abandoned piles tend to slide downward, exposing
fresh refuse with hard rains. For successful revegetation, these slopes
must be regraded to stable angles. No amount of vegetative cover will
stabilize materials with fundamental slope instability problems. Fine
refuse particles washed from recently exposed surfaces present problems
of acidification and sedimentation in nearby streams. This is
predominantly a problem with abandoned piles, constructed prior to
enactment of modern reclamation law, that are not under permit. 

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Pyrite Oxidation and Potential Acidity

Most of the environmental problems associated with coal refuse occur as
a result of pyrite oxidation and the production of acidity. Much of the
total sulfur in refuse is present as pyrite (FeS2) and other sulfides
which oxidize to sulfuric acid in the presence of water and oxygen. This
highly acidified water is frequently less than pH 3.0 and dissolves the
mineral matrix around it as it leaches downward, becoming charged with
aluminum, manganese, and other cations and metals. 

The pyrite reaction rate is dependent not only on the oxygen supply and
microbial catalysis, but also on the size and morphology of pyrite
particles. Two types of pyrite are commonly found in coal. Framboidal
(fine) pyrite forms concurrently with the coal, while coarse-grained
pyrite is a secondary product of coal formation and is usually found in
former plant structures and joints in the coal. Framboidal pyrite
particles (2-15 µ) have a high surface area and will oxidize rapidly.
Coarse-grained pyrite is much less reactive. In some refuse materials, a
large amount of the total sulfur is contained in relatively unreactive
organic forms or as sulfate, which is one of the reaction products of
the oxidation processes discussed above. These two forms are not
generally considered to be acid producing. Thus, the total-S content of
refuse is not as reliable a predictor of acid producing potential as is
pyritic-S content. 

Freshly exposed pyritic refuse often has a near-neutral pH. After
oxidation, pH values can drop dramatically, and many pyritic coal refuse
materials have a very low (2.0 to 3.5) pH once they weather. After
complete oxidation of sulfides and subsequent leaching of acid salts,
the pH often rises into the low 4's but is strongly buffered in that
range by aluminum and other metals. The pH of a particular refuse
material will depend not only on its pyrite content, but also on the
length of exposure time and its acid-neutralizing capacity. Most coal
refuse materials in the Appalachians contain an excess of oxidizable
sulfur compared to neutralizing carbonates and are therefore net acid
producing over time. The average fresh refuse material in Virginia
requires 10 tons of CaCO3 per 1000 tons of raw refuse to neutralize the
acidity present, assuming complete reaction of pyrite and carbonates via
the regular acid-base accounting technique (   HYPERLINK
"http://www.ext.vt.edu/pubs/mines/460-131/table1.html"  Table 1  ). The
potential acidity of refuse materials in West Virginia and Kentucky is
often much higher, sometimes exceeding 50 tons of lime requirement per
1000 tons. 

The rate of pyrite oxidation and acid production is generally highest in
the oxygenated surface layer, which is also the zone utilized by plant
roots. A rapid drop in pH releases plant-toxic concentrations of
acid-soluble metal ions into soil solution and reduces the availability
of many plant nutrients. When the pH falls below 4.5, root growth of
many plant species ceases. Another problem caused by pyrite oxidation is
the production of sulfate salts, which may accumulate to toxic levels in
the root zone. These salts are generally water-soluble and accumulate on
coal wastes during dry periods as water is lost by surface evaporation.
The whitish surface coating seen on refuse and coal piles during dry
weather is evidence of this process (see   HYPERLINK
"http://www.ext.vt.edu/pubs/mines/460-131/figure2.html"  Figure 2  ). 

Heavy metals such as copper, nickel, cobalt, and zinc are often
associated with pyrite and other sulfide minerals. Our studies have
indicated that soil solutions leaching from coal refuse materials may
contain much higher concentrations of Cu, Zn, and Ni than previously
assumed. Elevated levels of heavy metals in soil solution can be toxic
to plant roots and microbes and may pose a water quality hazard. 

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Acid Seepage and Leachate Production

While acid-sulfate weathering processes drastically inhibit vegetation
establishment, perhaps their greatest environmental impact is through
acid leachate production. As drainage waters percolate through a refuse
pile, leachates often become quite acidic and high in heavy metals.
These leachates, collectively referred to as "acid mine drainage" (AMD),
leave the pile as deep drainage waters, sideslope springs, or in surface
runoff. If not properly curtailed or treated, AMD poses a serious
long-term water quality threat. Seeps of AMD on steep fill sideslopes
also pose a major revegetation problem. 

Pyrite oxidation is catalyzed by Thiobacillus ferooxidans, and the
ubiquitous bacteria are capable of functioning in very low oxygen (<
1.0% partial pressure) environments. Therefore, as long as acid water is
allowed to percolate through a refuse fill, pyrite oxidation will occur
deep within the pile, regardless of surface revegetation and
stabilization efforts. The net-leaching environment of the Appalachians
assures that acid mine drainage is inevitable for any coal refuse pile
that contains net acid-forming materials. Due to the total mass of the
pyrite in many refuse piles and the relatively slow rate of water
movement through them, it is reasonable to expect that acid mine
drainage will be emitted for decades, if not longer. 

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Spontaneous Combustion

Many older refuse piles are high in coal fragments; often, such piles
were constructed in loose, unconsolidated configurations which allow
oxygen to interact easily with the refuse. Because pyrite oxidation is
an exothermic (heat producing) reaction, spontaneous combustion of older
refuse piles was a common occurrence. Combustion of older piles has also
occurred due to trash burning, arson, forest fires, and other factors.
Burning refuse piles pose local air quality problems and are virtually
impossible to revegetate. 

Modern refuse piles are generally lower in coal than older piles, due to
improved coal separation technologies, and are compacted in place to
limit air and water penetration. The thick topsoil requirement for
refuse pile reclamation is also intended to further limit oxygen
movement into the fill, although our results indicate that significant S
oxidation occurs in refuse even under 4 feet of topsoil cover. Reports
of combustion of modern refuse fills are very rare. When they do occur,
they are generally the result of arson or accidental ignition. 

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Low Fertility

Because coal refuse is composed mainly of weathered rock and coal
fragments, plant available nitrogen (N) and phosphorous (P) are
generally low. Due to their weatherable mineral content, however, refuse
materials can be expected to supply adequate levels of calcium (Ca),
magnesium (Mg), and potassium (K) to plants. In general, reclamation of
coal refuse materials requires substantial fertilization, particularly
with N and P. However, even large applications of N can easily leach out
of the rooting zone within one year if not assimilated into plant
tissue. The majority of plant available N after the first year must be
supplied by legumes, so it will tend to be held in organic matter forms
over time. Therefore, the establishment and maintenance of legumes over
the first season after seeding is critical to long-term revegetation
success. 

Soil P does not leach from the rooting zone in the same fashion as N;
however, P is readily converted into soil mineral forms which are not
available to plants. Soil P held in organic forms is protected against
these losses, so the establishment and turnover of an organic matter
pool in the reclaimed "refuse soil" is also critical for long term
P-fertility. Organic amendments such as sewage sludge supply large
amounts of N and P in addition to their beneficial effects on the soil
physical environment and should be considered for use on refuse piles
when available (see   HYPERLINK
"http://www.ext.vt.edu/pubs/mines/460-131/figure3.html"  Figure 3  ).
For additional discussion of N and P behavior in mine soils see VCE
Publication 460-121. 

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Moisture Retention, Rooting Depth and Compaction

Inadequate plant-available moisture is a major problem with all mine
spoils and refuse materials. The moisture holding properties of a given
refuse are directly related to its particle size distribution. Coal
refuse is usually coarse in texture with a very low water-holding
capacity (see   HYPERLINK
"http://www.ext.vt.edu/pubs/mines/460-131/figure4.html"  Figure 4  ).
Refuse materials in Virginia average 59 percent coarse fragments (>2mm)
depending on length of exposure to weathering (   HYPERLINK
"http://www.ext.vt.edu/pubs/mines/460-131/table1.html"  Table 1  ). As
the average refuse particle size increases, the material's moisture
retention capacity is reduced. The exclusion of fine refuse from a fill
will further reduce water holding capacity. For this reason, it is
desirable to place combined refuse (coarse plus fine) in the final
revegetation surface if possible. 

Plant roots are able to extract nearly all available water which is
retained in the rooting zone of refuse (usually the upper 24 inches) if
potential acidity has been neutralized. There are a number of ways to
increase moisture retention in coal refuse. The addition of organic
amendments, heavy mulching, and the natural process of soil organic
matter accumulation over time will all improve the water supplying
ability of coal refuse. We have frequently observed that the addition of
only several inches of topsoil or similar finer spoil materials to an
otherwise barren coal refuse material is all that is necessary to
promote plant growth, in cases where potential acidity has been
neutralized. This occurs because the cover material improves water
retention and supply. In older piles where weathering has taken place,
the upper surface may contain very fine particles similar in texture to
silt or clay; such materials will have a higher moisture retention than
coarse, fresh refuse. When revegetating older piles where soil cover is
expensive or limited, weathered surface materials should be segregated
prior to regrading and then re-applied to the pile as final cover. 

Virginia mining regulations require coal refuse to be "spread in layers
no more than 2 feet in thickness; and compacted to attain 90 percent
maximum dry density to prevent spontaneous combustion and to provide the
strength required for the stability of the coal processing waste bank."
Excessive compaction has been identified as a major factor limiting
reclamation success throughout the USA and will cause similar problems
in coal refuse materials by limiting the available rooting depth.
Whenever possible (i.e. on near-level or mildly sloping surfaces, where
surface stability is not a major concern), the final lift or surface of
the refuse pile should be left as loose as possible to enhance its
potential to support plant growth. 

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High Surface Temperature

Coal refuse varies in color from light gray to black. Thus, much of the
incoming solar radiation is retained as heat. Under sunny skies, the
surface temperatures on the refuse surface may exceed air temperature by
300F or more depending on cloud cover and slope aspect. Surface
temperature may fluctuate widely during the course of a day. Early
morning temperatures may be higher than air temperatures due to heat
retention within the pile and this is also true of evening temperatures.
On a warm cloudless day on a South-facing slope, the surface temperature
may exceed 1500F. Surface temperatures in this range are lethal to most
plants and legume seedlings are particularly susceptible to heat kill. 

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Summary

The development of a successful coal refuse area reclamation strategy
must take a number of factors and processes into account. Most
important, the surface of the refuse must be manipulated and treated to
overcome soil water-holding, temperature, and acidity problems. The
revegetation strategy must be capable of producing a plant community
that can withstand a wide range of harsh soil and micro-climatic
conditions. Finally, the steeply sloping surfaces of most refuse piles
greatly complicate revegetation. Each area of the coal refuse fill must
be carefully assessed for the properties and problems discussed above,
and the final reclamation approach must be tailored accordingly. 

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Coal Refuse Reclamation Studies and Trials

Best results in reclamation of coal refuse piles have been achieved by
incorporating lime and plant nutrients into a suitable soil cover above
the refuse. In some cases, this is not possible due to the lack of
available soil cover materials or the expense of transporting soil.
Vegetation can be established directly on some refuse materials after
amendment with lime and fertilizers. The major question involved with
direct seeding strategies is whether or not the surface will remain
hospitable for plants over extended periods of time. The establishment
of a permanent legume component on refuse is particularly difficult.
Improvement in vegetation establishment on bare refuse has been reported
with high rates of organic amendments (sewage sludge) in a number of
states. Combinations of lime, mulching, heavy P, and sewage sludge
treatments have maintained vigorous vegetation for five full seasons in
SW Virginia in Powell River Project trials on a slightly acidic refuse
material. 

Although many different companies and researchers have evaluated
strategies for establishing plant cover on coal refuse, a unified study
to incorporate a variety of potentially important factors (such as
refuse properties, weathering with time and reclamation strategies) has
not been reported. Often, experiments are conducted and abandoned before
the long-term effectiveness of a single or multiple treatments can be
determined. Also, many studies are site specific; remedies are developed
for localized conditions, and no effort is made to correlate results
with refuse character or general reclamation principles. 

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How to Develop a Successful Refuse Reclamation Strategy

The successful long-term stabilization and reclamation of refuse piles
is a difficult and complicated process. Reclamation strategies must be
based on a thorough understanding of refuse and disposal site
properties, how they will react to various treatments, and how the
soil/plant system will change with time. Establishing a vigorous cover
to stabilize the fill surface and reduce acid leachate production is
critical. 

Moisture stress, induced by high coarse fragment contents, salts, and
high surface heat, is the primary growth limiting factor in most fresh
coal refuse. As the materials weather, acidity becomes a major problem
in some refuse; but acidity can be controlled to a large extent by
liming. Many coal refuse materials can be successfully direct seeded
once their potential acidity has been neutralized through appropriate
liming practices (See   HYPERLINK
"http://www.ext.vt.edu/pubs/mines/460-131/figure5.html"  Figure 5  and  
HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/figure6.html" 
Figure 6  ). Reagents and chemicals used in mineral processing may also
limit plant growth in fresh wastes, but little is known about their
effects. Once the coal refuse weathers and leaches for several years,
and its physical and chemical properties stabilize, it becomes easier to
utilize as a plant growth medium. Many of the older abandoned piles in
the Appalachians are invaded by native pioneer vegetation after this
stabilization occurs. Care should be taken not to disturb this fragile
surface zone on older piles (if possible) during reclamation. 

The use of a reduced thickness of soil cover (< 4 feet) to reclaim coal
refuse has been successful in several experiments in Virginia and other
states. Even thin (< 1 ft.) layers can provide enough water-holding
capacity and suitable rooting environment for establishment of both
grasses and legumes on moderately acidic wastes. Thicker covers may be
necessary for long-term legume vigor on highly acidic refuse. The use of
lime at the refuse/soil contact is essential when thin topsoil covers
are employed; lime application rates should be based on the potential
acidity of the underlying material. Where high surface temperature and
low water supply are major problems, topsoiling also appears to be the
best alternative for establishing a permanent vegetative cover. Direct
seeding appears feasible for refuse with low to moderate levels of
acidity, particularly when heavy agricultural lime, mulch, and other
organic treatments like sewage sludge are employed. Topsoiling plus
liming is the best alternative for highly acidic materials. 

Revegetation strategies should establish a quick annual cover to rapidly
provide shade and a natural mulch for perennials. Any plant materials
used on coal refuse must be capable of withstanding extreme short- and
long-term changes in soil and site conditions. The importance of
overcoming the heat and water holding limitations of bare refuse cannot
be overemphasized. The combination of liming, fertilization, surface
treatments, and seeding mix must be designed to rapidly establish an
annual cover that will shade the surface and thereby improve soil
moisture and temperature conditions. The initial cover crop also takes
up and holds essential plant nutrients against leaching and runoff and
then returns these nutrients to the soil as it decomposes. The permanent
perennial species then germinate and establish in the favorable
micro-climate provided by the cover crop. Once the perennial species are
well established (usually by the second year) and plant/soil nutrient
cycles have become established, the chances for long-term reclamation
success (and bond release) are greatly improved. Over the years we have
observed many vigorous stands of annual cover crops on direct seeded
coal refuse materials. However, diverse self-sustaining stands of
perennial grasses and legumes after multiple seasons are much more
difficult to achieve. 

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Guidelines for Refuse Area Revegetation in Southwest Virginia

The guidelines which follow represent our best recommendations for the
stabilization and revegetation of refuse piles in SW Virginia at this
time. They were submitted to VDMLR for consideration in 1991 and have
been used successfully by a number of mining firms over the past several
years. It is important that these guidelines be used in consultation
with regulatory authorities; use of these guidelines without regulatory
agency concurrence may lead to permit violation, particularly with
regard to topsoiling or fertilizer augmentation requirements. These
guidelines are based upon Powell River Project cooperative research work
at multiple sites since 1983 and our interpretations of relevant
literature. 

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Refuse Characterization

Our studies indicate that many refuse materials can be direct seeded or
successfully reclaimed with reduced topsoil depth if and only if their
physical and chemical properties are well understood. The two most
important properties are water holding capacity and potential acidity.
Therefore, in order to use our classification system (see   HYPERLINK
"http://www.ext.vt.edu/pubs/mines/460-131/table2.html"  Table 2  ), data
on these parameters and how they vary across the reclamation surface
must be obtained. 

Particle size distribution should be determined by sieve analysis. Any
refuse that is less than 20 percent fines (< 2mm) will be difficult to
reclaim regardless of acidity levels and should be topsoiled. It is
possible to increase the water holding capacity of coarse refuse with
additions of organic amendments and fine textured soils as discussed
later. Compaction is also a major factor in limiting water holding in
refuse materials. Therefore, for direct seeding options, the surface 18
inches of refuse should be left uncompacted or should be ripped before
seeding. 

Potential acidity should be determined by a qualified laboratory using
either the conventional acid-base accounting method or the hydrogen
peroxide oxidation technique. These two techniques give somewhat
different estimates of the liming requirement for refuse materials (see 
 HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/table1.html"  Table
1  ), with the peroxide oxidation technique being more conservative.
Potential acidity or acid base accounting (ABA) results are typically
reported in net tons of lime required per 1000 tons of spoil or refuse
tested. Given that one acre of refuse to a depth of six inches weighs
approximately 1000 tons, these figures equate to a field liming estimate
in tons per acre. Simple measurements of pH are not valid for estimating
refuse potential acidity since they do not account for unoxidized
pyritic sulfur and/or the native lime content in the sample, and the
chemical reactions in the weathering refuse will cause the pH to change
with time. 

The ABA lime requirements should be considered as a bare minimum lime
application; additional quantities may be applied to help ensure
success. Many experts in the field of acid mine drainage control
advocate the use of two to four times the amount of lime prescribed by
the ABA technique to insure that the treated zone of acid-forming
material is permanently stabilized. Studies have shown that in some
cases the rate of pyrite oxidation is so fast and the levels of iron
plus acidity generated in solution are so high that a large excess of
reactive lime is necessary to prevent the alkaline side of the balance
from being overwhelmed. 

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Site Preparation

The preparation of a refuse disposal area for hydroseeding should begin
well in advance of actual seeding. Grading plans should minimize steep
slopes where possible, provide equipment access for revegetation
efforts, and reduce potential washes or rills from developing. The final
lift of 2 to 3 feet of material should be left uncompacted or loosened
with a ripper prior to the final grade. 

Where possible, it is advisable to allow fresh refuse to lie exposed for
a period of 6 months or more before seeding. During this time, refuse
samples representative of areas to be seeded should be collected and
analyzed for potential acidity as discussed earlier. Dependent on this
analysis, agricultural lime or other suitable liming materials should be
applied and incorporated 2 to 3 months before planting. It is possible
to reduce the potential acidity of highly acidic materials (as discussed
in   HYPERLINK "http://www.ext.vt.edu/pubs/mines/460-131/table2.html" 
Table 2  ) by repeated addition of lime over an extended period. Should
this method be used, it is recommended that no more than 25 tons/acre of
lime be applied at any one time. Single applications using higher rates
have been shown to form FeCO3 concretions around larger sized lime
particles rendering the lime ineffective unless the lime is thoroughly
incorporated to a depth of six inches or more. Similar problems have
been noted when coarse textured liming materials have been utilized. 

Sloping areas are of particular concern in site preparation. Often
lateral water flow through a pile will result in an acid seep or "hot
spot" along the slope. These areas often appear chalky white during dry
weather and may exhibit a pH below 3.0. These "hot spots" should be
pinpointed and treated heavily with lime where possible to prevent
future problems in plant establishment. 

Immediately prior to seeding, sloping areas should be prepared for
seeding. The conventional approach is to track the slope with a dozer or
other suitable equipment. Tracking should be done in a manner that
leaves narrow "track" depressions across the face of the slope. In
practice, these "tracks" retain water, seed, and mulch during rains and
are usually the first areas to show plant growth. However, a large body
of revegetation literature clearly indicates that rough graded slopes
are much superior to "tracked" slopes for the prevention of short-term
runoff and the establishment of vegetation. This is particularly true of
sites where forest establishment is required (See VCE Publication
460-123. ). Tracked slopes are also more compact than rough-graded
slopes. In situations where surface stability is not a major concern, we
strongly recommend only rough grading be applied to coal refuse disposal
surfaces. This recommendation is contrary to common practice, however,
since the current "mind set" of equipment operators, reclamation
planners, and mine inspectors tends to favor the
smooth-grading-tracking-compaction approach. 

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Fertilization

Because of the inherently low fertility of refuse, vegetation
establishment requires the addition of N, P and K fertilizers. Field
trials and laboratory analyses have pinpointed P as being the most
limiting nutrient to plant growth on these sites. If topsoil or a
topsoil substitute material is to be used, a representative sample
should be submitted to the Virginia Tech Soil Testing Laboratory (or a
comparable commercial facility) for analysis. Please see VCE Publication
460-121. for a discussion of fertilizer interpretations for mine soils. 

As a base rate of fertilizer for direct seeding, 100 lb/acre (lb/a) of
N, 350 lb/a of P (as P2O5) and 100 lb/a of K (as K2O) is recommended. To
attain this high P level it may be necessary to supplement conventional
fertilizers (e.g. 10-20-10) with a high P fertilizer like
superphosphate. These rates are suggested when the seed mixture to be
used contains legumes (clovers, trefoil, etc.) and assume adequate
establishment of legumes for continuing N availability in succeeding
years as discussed earlier. 

When legumes are seeded, the appropriate inoculant should be added at
time of seeding (see VCE Publication 460-122. ). Care should be taken to
keep the pH of the hydroseeder slurry buffered above 4.0 with lime. The
inoculant should be added to the hydroseeder tank immediately before
seeding, since the inoculant bacteria will perish if left in the high
salt environment of the hydroseeder slurry for more than a few minutes.
If only grasses are to be used, then the N rate should be adjusted
upward to 150 lb/a, but the grasses will need additional N fertilizer in
successive years in the absence of legumes. 

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Seeding Rates and Species Mixtures

Selection of species suitable for planting on refuse is complicated by
the variability of the material. Therefore, it is imperative to use
species which will tolerate a wide range of pH, moisture and temperature
conditions. Consideration should also be given to the time of year when
seed is applied and to the overall goal of establishing a diverse and a
permanent vegetative cover. These criteria cannot be met by use of a
single species mixture on all sites and/or under all conditions. 

Powell River Project direct seeding field trials, which were established
using the above criteria, have been successful for five growing seasons
and beyond. Species mixtures and seeding rates detailed in   HYPERLINK
"http://www.ext.vt.edu/pubs/mines/460-131/table3.html"  Table 3  appear
to be suitable for direct seeding of refuse and for use with topsoil
covers. These recommendations were based on the conditions at our
various research sites, and addition or deletion of species should be
considered depending upon your local site conditions and seed
availability. Each mixture contains species adapted to a variety of site
conditions which is intended to overcome local mine soil variability
problems and make the mixes usable on a variety of sites. Spring
seedings should be done after March 15 and before May 15 for optimal
results (   HYPERLINK
"http://www.ext.vt.edu/pubs/mines/460-131/table4.html"  Table 4  ). Fall
seeding is recommended between September 15 and November 15 for best
results. Environmental conditions during the summer and winter are
generally unfavorable for successful establishment of mixed perennial
vegetation, and annual covers should only be seeded during these
periods. 

Commercially available wood fiber or paper mulches at conventional
application rates perform satisfactorily for their intended use:
establishment of grasses on topsoil. However, they are inadequate under
the extreme environmental stresses on refuse piles. Our recommendation
is that paper mulches be used at higher rates (> 2000 lbs/ac) in the
hydroseeder tank mix, or in conjunction with straw mulch on refuse.
Field trials indicate that using straw and wood fiber/paper mulches
together greatly improves plant establishment and long term vigor,
particularly on hot, south-facing fills. 

A technique which has proven successful in our work is as follows: when
loading the hydroseeder include paper mulch to achieve 1000 to 1500 lb/a
along with the desired amount of seed and fertilizer. Spray this mixture
in such a manner that it covers twice the normal area usually covered
with l tankful (or half the normal rate). Next, using a mechanical straw
blower or manual spreader, cover the area just sprayed with straw. Good
coverage is achieved with 2500 lb/a of straw. Respray this area again
with the mulch/seed/fertilizer mixture and in the same manner as
indicated above. 

By using this seeding method, several factors critical to successful
establishment are ensured. The shade provided by the mulch reduces water
loss from the seedbed and shields young seedlings from the high
temperatures common to these areas. The first tankful provides good
seed/soil contact which is necessary for good germination. The use of
straw mulch over this initial tankful provides shade which reduces water
loss and lowers surface temperatures. The addition of the final tankful
adds more seed and water which may infiltrate the straw mulch, while the
paper mulch tacks the straw mulch in place by forming a mat-like
surface. While this technique adds to the cost and time involved, we
feel that it is justified in terms of long-term establishment success,
particularly on hot droughty sites. 

In summary, any direct seeding should be done with heavy mulch,
applications of at least 350 lb/a of P2O5,and normal rates of N and K as
discussed previously. Many direct seeding alternatives may be impossible
due to the difficulty of working amendments on steep fill faces. In
these cases, some combination of lime and topsoil will be the only
viable alternative. 

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Tree Planting

Currently, very little has been documented about the use of woody plants
for the reclamation and revegetation of coal refuse. Experience of the
industry indicates that black locust (Robinia pseudoacacia L.), white
pine (Pinus Strobus), and red pine (Pinus Resinosa) can be successfully
direct hydroseeded onto conditioned refuse. Some success has also been
achieved using containerized tree seedlings. Several tree species (e.g.
black birch, Betula lenta) are known to successfully colonize old refuse
piles, but seeds or seedlings of these species are not readily available
commercially. Refer to VCE Publication 460-123. for a detailed
discussion of establishing forests on mined lands. 

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Post-Reclamation Management and Land Use

Current regulations require that the 5-year bonding liability period
begin after final reclamation and revegetation are completed. Except for
practices typical for the specified post-reclamation land use, further
augmentation of seed or soil amendments restarts the bonding period.
When refuse disposal areas are being returned to unmanaged forest,
augmentation is not considered by regulatory authorities to be a typical
management practice. However, despite current regulations, we feel that
augmentation, via split fertilizer applications or spot liming and
seeding, is often necessary and should be a specified practice for the
reclamation of coal refuse disposal areas. Often, problem areas
requiring this type of augmentation do not become apparent until the
second or third growing season and may only cover a small area. While
the area affected may not be large enough to preclude bond release, it
may present a potential erosion/or water quality threat in succeeding
years. For this reason, augmentation treatment of these areas is
encouraged. 

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Long-Term Water Quality Concerns

The long-term emission of acidic leachates from refuse piles is a major
problem. These leachates present a much more difficult challenge than
surface revegetation. To stop leachate production, water flow through
the fill must be limited, but this is very difficult in a humid leaching
environment such as Virginia's. There is evidence that a vigorous
vegetative cover can reduce acid drainage by intercepting and
transpiring rainfall, consuming oxygen in the rooting zone, and through
several other mechanisms. However, the fundamental reaction
thermodynamics of pyrite oxidation in the presence of water and oxygen
cannot be ignored. 

While various treatments have been shown to slow the rate of the
acid-producing pyrite weathering reactions, eventually the reactions
will continue to completion. The mass of sulfur within most disposal
areas far exceeds the neutralization potential of any surface applied
treatments. Thus, unless water is completely excluded from the fill,
even moderately sulfidic refuse materials should be expected to
discharge acidic leachates and long-term water treatment strategies
should be planned. For net-acid producing refuse piles, these discharges
will generally continue well beyond the 5-year bond liability period.
For such piles, the leachates will have to be neutralized with caustic
additions and/or acid treatment wetlands. 

Acid-treatment wetlands are not currently accepted by regulatory
authorities as a "walk-away" solution to acid leachate water quality
problems. Where sufficient land area is available, however, wetland
treatment systems have proven to be a more cost-effective means of
treating acid water than alkaline chemical systems. Lack of sufficient
land area in the right location has proven to be a major barrier to use
of acid treatment wetlands. Proper placement and design in the landscape
can allow refuse fills to utilize acid treatment wetland systems as a
cost-effective means of leachate water treatment. Design requirements of
acid treatment wetlands are reviewed in VCE Publication 460-132. 

The only technology that is known to be effective in eliminating the
acid leachate potential at refuse disposal sites is the bulk-blending of
alkaline materials with the refuse as it is placed in the fill. Ground
agricultural limestone serves this purpose well, but may be required at
mixture ratios of up to 5 percent. This would add a considerable cost to
refuse disposal. 

Current research is evaluating the potential to use alkaline fly ash as
a lime substitute for this purpose. However, not all fly ash materials
are alkaline, and the net water quality impacts of blending ash and
other coal combustion by-products, such as scrubber sludges, with
acid-forming refuse materials must be carefully considered. Details on
such uses of coal combustion by-products in mined land reclamation are
given in VCE Publication 460-133. 

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Summary and Recommendations

The Appalachian coal industry has made great progress in coal refuse
reclamation over the past 20 years. However, further improvements are
needed to ensure that the industry is not faced with significant
long-term liabilities. Refuse disposal areas should be designed and
constructed with long-term stabilization and water quality concerns in
mind. In particular, fill hydrology and its interaction with pyrite
weathering and seepage should be considered when designing and
constructing refuse fills. The surface reclamation strategy should be
designed to maintain a vigorous plant cover and to neutralize surface
acidity and water holding limitations over time. Excessively steep
slopes are very difficult to treat as needed to establish permanent
vegetation and should be minimized where possible. The land area
requirements of constructed wetland water treatment strategies, which
are capable of reducing the long term costs of leachate water treatment,
should be considered in fill design. 

The long-term acid generation potential of a refuse pile must be taken
into account during reclamation and closure planning. It is likely that
permit approval for refuse disposal areas in the future will depend on
the permittee's ability to prove that the site will not pose a long-term
acid mine drainage hazard. Currently, bulk blending of lime or other
alkaline materials is the only viable long term approach to permanent
control of acid mine drainage in-situ. 

Finally, we believe that the current practice of designating reclaimed
coal refuse piles to support "conventional" post-mining land uses such
as wildlife enhancement or unmanaged forest uses does not recognize the
particularly fragile nature of their surface plant/soil communities.
These areas need to be strenuously protected from surface disturbance
and erosion once they are reclaimed. Perhaps a special "environmental
protection zone" land use category should be developed. The need for
augmentation seed and fertilizer, within certain guidelines, could be
recognized within this land-use category. 

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Acknowledgments

This paper summarizes the collective work and insights of a number of
people working with us on the Powell River Project coal refuse research
study. Katie Haering, Vince Ruark, and Jay Bell have all contributed
immeasurably to our understanding of this problem through their
collective efforts. We wish to thank Eddie Hannah and Mark Singleton
(Jewell Smokeless Coal Company), Ken Roddenberry and Steve Sutphin
(Westmoreland Coal Company), Ron Keene (United Coal Co.) and Roger Jones
(Pyxis/Paramont Mining) for their generous help and cooperation
throughout our studies. We also received invaluable help in the field
from Ron Alls, Ren-sheng Li and Velva Groover. 

The research that allowed us to reach this level of understanding was
supported by the Powell River Project, the Virginia Center for
Innovative Technology, and the U.S.D.I. Bureau of Mines Mineral Inst.
program, grant # G1164151. Primary sponsors of the Powell River Project
program are Penn Virginia Coal Corporation, Norfolk Southern Foundation,
other southwestern Virginia firms, Virginia Tech, and the Commonwealth
of Virginia. 

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Powell River Project "Reclamation Guidelines"

This publication is a chapter from Reclamation Guidelines for Surface
Mined Land in Southwestern Virginia, Virginia Cooperative Extension
Publication 460-120, which is based on the results of research and
education programs supported by the Powell River Project since 1980.
Other Virginia Cooperative Extension publications referenced in the text
are chapters of the Reclamation Guidelines series; all referenced
chapters are in preparation but, as of this writing, some have not yet
been issued. 

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References

Buttermore, W.H., E.J. Simcoe, and M.A. Maloy. 1978. Characterization of
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Daniels, W. L., and D. C. Dove. 1987. Revegetation strategies for coal
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Daniels, W. L., K. C. Haering and D. C. Dove. 1989. Long-term strategies
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Daniels, W.L., K.C. Haering, B.R. Stewart, R.V. Ruark and D.C. Dove.
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Joost, R. E., F.J. Olsen, and J.H. Jones. 1987. Revegetation and
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Robl, T.L., A.E. Bland, and J.G. Rose. 1976. Kentucky coal refuse: A
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Schramm, J. R. 1966. Plant colonization studies on black wastes from
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Stewart, B. R. 1990. Physical and Chemical Properties of Coarse Coal
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Stewart, B.R. and W.L. Daniels. 1992. Physical and chemical properties
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