Conference PaperPDF Available




Content may be subject to copyright.
DANIELS, W.L., Can we return heavy mineral sands mines in Virginia to productive agricultural uses? Heavy Minerals 2005, Society for Mining,
Metallurgy, and Exploration, 2005.
Virginia Tech, Blacksburg, VA, USA
Significant deposits (> 4,000 ha) of heavy mineral sands were discovered in the USA Coastal
Plain of Virginia and North Carolina in 1989. The majority of these lands support highly
productive row crop agriculture, and the development of restoration protocols that would return
these lands to agricultural use was deemed to be critical to the long term sustainability of mining
operations. Virginia Tech worked closely with all stakeholders to develop appropriate restoration
protocols and to coordinate their implementation. Full-scale mining operations at the Old Hickory
Project in Virginia were initiated in 1997 by Iluka Resources Inc., and restoration protocols have
continued to evolve in response to a variety of economic, technical, and social issues.
Approximately 750 ha of land are in various phases of backfilling and final reclamation. Return
of these lands to agricultural row-crop production has been complicated by lateral variability in
mine soil physical conditions, excessive compaction, and limited topsoil return. However, within
the past two years, a series of tailings deposition and soil reconstruction practices have been
developed and implemented that significantly improve post-mining soil productivity. Deep ripping
and appropriate use of organic soil amendments have been particularly effective at restoring post-
mining soil productivity.
Mineral sand deposits were discovered along the Upper
Coastal Plain of Virginia, USA, in the late 1980's (1, 2),
and additional deposits were quickly located in similar
landscapes in North Carolina. Much of the recoverable
mineralized area occurs under prime farmlands (Fig. 1),
and as much as 4,000 ha could potentially be disturbed
depending on long-term market demand for titanium. This
is an important peanut, soybean, tobacco, and cotton-
producing region. The Old Hickory deposit in Dinwiddie
and Sussex Counties, Virginia, is the largest ore body (~
1500 ha). Mining leases for Old Hickory and two smaller
deposits in North Carolina were finalized in 1990/1991 by
RGC Mineral Sands with the landowners, who negotiated
as a block with several competing mining firms. Active
mining at Old Hickory commenced in the summer of 1997,
and Iluka Resources Inc., subsequently acquired RGC’s
mineral sands holdings, and is the current operating
Before the initiation of this research program, the
return of mineral sands mines to intensive agricultural use
had not been studied or documented. However,
considerable research literature is available regarding the
return of coal-mined lands to prime farmland status as
required by USA federal coal mining regulations. In
general, soil physical conditions such as compaction, water
holding, and permeability are limiting to rowcrop
production in restored prime farmlands in the USA. Jansen
and Dancer (3) reported that corn yields on replaced
topsoil depended on the quality of the topsoil and its
thickness. Compaction has been reported as the most
limiting factor in many mine reclamation studies.
Barnhisel and Gray (4) observed that compaction reduced
yields in nearly all crops and in mine soils, respectively.
Collectively, the majority of prime farmland restoration
studies to date indicate that return of post-mining
landscapes to productivity levels that approach (90 to 95%)
pre-mining conditions is possible only with appropriate
soil reconstruction, deep tillage, soil amendment and
fertilization practices (5).
Post-Mining Land Use and Sustainability Issues
The overall long-term sustainability of any mining
operation is heavily dependent upon the quality of the post-
mining landscape in relation to landowner, regulatory, and
general societal expectations. Clearly, the most challenging
aspect of developing effective and sustainable
rehabilitation strategies for the Old Hickory deposit is the
fact that much of this deposit underlies prime farmland.
Secondly, the silt+clay (slimes) content of the mineralized
ore body is higher than this industry has mined before,
generating a wide array of operational issues. Worldwide,
mineral sands mines have been successfully returned to a
variety of post-mining land uses including grazing,
forestry, native heath/shrubland communities, and
wetlands/nature preserves (6). However, before the
initiation of the project reported here, post-mining return of
mineral sands mines to prime farmland status had never
been attempted. Two important components of the Old
Hickory mining lease negotiation process were (1)
assurances by RGC of their intent to return the lands to
intensive agricultural production following mining, and
(2) RGC’s willingness to employ our university (Virginia
Tech) to develop a dedicated reclamation research
Figure 1. Pre-mining agricultural landscape at Old Hickory
Project Area in Dinwiddie County, Virginia, USA. Heavy
minerals are enriched in the upper 5 to 20 m of the surface,
with significant accumulations commonly occurring in the
topsoil layer.
Pre-Mining Research Program
Virginia Tech worked closely with all stakeholders to
develop appropriate restoration protocols and to coordinate
their implementation. Early (1990-1995) baseline research
efforts included detailed soil and crop productivity
mapping, wetland soil and geohydrologic studies, and
characterization of simulated tailings and reconstructed
soils (7, 8). In a precursor study, we evaluated reblended
tailings:slimes mixtures in the greenhouse and found that
the simulated mine soils (without topsoil) could serve as
suitable plant growth media if significant levels of P were
added to offset fixation potentials along with appropriate
pH adjustment via liming. In a follow-up study (9) on
pilot mining pits between 1995 and 1998, we compared the
effects of thick (25 cm) topsoil return vs. topsoil
substitution via the addition of 112 Mg/ha yardwaste
compost to mixed tailings and slimes following heavy P-
fertilization, liming, and ripping of the reclamation surface.
Over a four-year cropping rotation, post-mining
productivity compared to adjacent prime farmland plots
was reduced by 23%, 3%, 27%, and 20% for each crop
(wheat/soybeans/corn/ cotton) in sequence (Table 1). For a
given crop in a given year, response to topsoiling versus
compost addition to the surface varied, and neither
treatment appeared superior. However, the addition of
topsoil significantly reduced lateral short-range yield
variability and effectively buffered the effects of subsoil
texture on crop yields. The final soil reconstruction
protocol implemented by Iluka as described below was
based upon the combined results discussed and cited
Regulatory and Permitting Framework
The mining and reclamation operations at Old Hickory are
regulated by the Virginia Division of Mineral Mining
(VDMM) under their non-coal minerals mining
regulations. These regulations do not require post-mining
return to set productivity levels, but they do require that
self-sustaining vegetation consistent with the agreed-upon
post-mining land use be viable for at least two complete
growing seasons. A reclamation closure plan must be
submitted and approved by VDMM, and presumably
should be consistent with landowner expectations. The
VDMM approved reclamation and closure plan specifies
topsoil return and the associated subsoil reconstruction
procedures discussed below. However, there was some
leeway present in the language regarding how topsoil was
defined that depending on interpretation, allowed other
mineral materials to be utilized as topsoil substitutes before
The regulatory permitting and approval process for
these operations was remarkably free of dissent from non-
governmental citizen and environmental advocacy groups.
This was primarily due to the fact that the operation was
permitting as a “no discharge facility” with respect to
surface waters, and strong assurances by the company
(RGC) of effective return to post-mining agricultural use.
However, a number of adjacent landowners expressed
concerns over the possibility of ground-water withdrawal,
so make-up process water is withdrawn from a distant (5
km) river source and piped to the site when needed.
Active Mining and Reclamation
Current Mining and Reclamation Processes
Immediately before mining, any existing vegetation (e.g.
forests or old fields) are removed and raked as necessary.
Where topsoil is being salvaged, approximately 15 cm of
A horizon material is bulldozed into windrows around the
edges of the mining pits, and commonly became a portion
of the enclosing dikes before 2004. Additional low-grade
subsoil material is utilized to build enclosing dikes (up to
4 m above grade) as necessary. Mineral enriched
weathered soil and underlying Coastal Plain sediments are
dry-excavated using conventional loaders and haulers,
Table 1. Effect of various soil reconstruction treatments on row-crop yields over four growing seasons at Old Hickory as reported
by Daniels et al. (9). Pit #1 was constructed from re-graded dike subsoil materials over mixed tailings/slimes. Pit #3 was
constructed from mixed tailings and slimes. All materials were limed, P-fertilized and ripped. Subsequently, half of each pit
received 25 cm of topsoil, while the other half received yardwaste compost incorporated at 112 Mg/ha. All reclamation treatments
are compared to an unmined prime farmland soil that was directly adjacent. Reclamation treatments yields are means of 12 pots;
unmined control values are means of 24 plots.
*Treatment yields by crop/year followed by differing letters are significantly different at p < 0.05.
dumped locally through a trommel-screen, and then
pumped with water up to several km to the wet
separation (concentrator) facility. The suspended
soil:water mixture is then passed through sequences of
separatory spirals where the finer textured slimes (clays,
silts, and very fine sands) are separated away from the
mineral bearing sand fraction. On average, the deposit
generates from 35% to 45% slimes, depending on the
weathering extent of the soil landscape unit being mined.
The heavy mineral sands are further separated via spirals
from the lighter host quartz. No additives or chemicals
are used in the separatory process. The two processed
waste streams from the wet separatory facility are
dominantly quartz sands (tailings) from the spirals and
the slimes which are partially dewatered in a thickener
via the addition of an anionic polymer flocculating agent.
The tailings and thickened slimes are then pumped back
to the reclamation pits in a 25 to 35% solids slurry.
Depending on weather conditions, it takes
anywhere from several months to a year for the surface
of the pits to dry down sufficiently to support machinery.
Sandy tailings “beaches” are readily accessed while
areas of high slimes content take considerably longer to
dewater to support tracked vehicles. Once accessible, the
surface contour of the dewatered pits is graded with a
bulldozer to ensure adequate surface drainage, and areas
of highly contrasting materials are worked out to the best
extent possible. This is often accomplished by
dozing/ramping the enclosing dike materials up and over
the final reclamation surface. Because grading is often
performed on very moist tailings, the materials are often
very well compacted, particularly in the final lifts. Next,
agricultural lime (4 to 10 Mg/ha) is applied depending on
texture and pH, and P-fertilizer is applied at 350 kg/ha
P205. Depending on revegetation sequence, certain pits
also received an additional 150 to 200 kg/ha P205 when
indicated by low soil test P. These bulk soil amendments
are then incorporated via a sequence of V-ripping
followed by chisel-plowing and/or offset disking. The
overall goal of this combined treatment is to physically
loosen, lime and P-fertilize the mine soil materials to a
depth of at least 30 cm. If topsoil has been retained in the
lateral dikes, and is accessible, it is then returned at
varying thickness over the conditioned subsoil materials,
and disked again. Additional N and K fertilizers are then
added to the reclamation surface per the intended
revegetation species mixture.
Reclamation Challenges in Active Mining
Active mining commenced in 1997 with the excavation
of two tailings disposal pits to accept the tailings and
slimes generated by processing ore-bearing sands mined
from first-cut mine pits in 1997 through 1999 at the Old
Hickory concentrator. Approximately 750 ha had been
disturbed through May of 2005, and a second
concentrator was opened at Concord in 2002. In the early
mining years, significant segregation of sandy tailings
from slimes in the refilled mining pits was obvious (10),
and the dewatered tailings/slimes mixtures were highly
variable laterally and vertically due to shearing and
redispersion of the slimes as they were pumped from the
thickeners back to the mining pits (Fig. 2). Subsequent
efforts by the mining company to minimize segregation
via the use of multiple internal cross-dikes and
flashboard risers to slow the rate of water movement and
constrain slimes migration away from discharge points
have been partially successful at increasing the amount
of slimes deposited and mixed with the sandy tailings.
The limited flocculation of slimes at the disposal
pits leads to slower than anticipated settling rates for the
dewatering tailings/slimes mixtures which produces a
number of secondary effects. First, a significant amount
1995/1996 1996 1997 1998
Treatment Wheat Soybeans Corn Cotton
---------------------------------------- kg/ha ----------------------------------------
Control 3750 a* 2449 ab 8553 a 1384 a
Pit#1 Topsoil 3573 a 1810 c 6587 b 1194 b
Pit#1 Compost 2892 b 2386 b 7589 b 1088 b
Pit#3 Topsoil 2756 bc 2684 a 4987 c 1004 b
Pit#3 Compost 2375 c 2594 ab 6620 b 1130 b
of process water remains entrained in the pit sediments
for longer periods of time, and is delayed in its return to
the concentrators. Secondly, the effective swell factor of
the disposed tailings/slimes mixtures is greater than
predicted, leading to the necessity for the enclosing dike-
walls to be raised to greater elevations than originally
anticipated. Finally, the entrained water lengthens the
effective dewatering period for the pits before they can
support bulldozers for final grading, an issue further
aggravated in periods of wet weather.
The original mining and reclamation plan specified
the stripping of approximately 15 cm of native topsoil
which was to be used as part of the external pit dikes,
and then graded back over the mining pit for
reclamation. By the second year of the mining
operations, it became obvious that the return of the
stored topsoil was complicated by its location in the
lower portion of the enclosing pit dikes, contamination
with subsoil and other non-topsoil materials, and the
inability of the mining operation to consistently ensure a
suitable storage location while it was being stripped (Fig.
2). Therefore, by 2001, only approximately 50% of the
reclaimed pits had received at least a limited topsoil
cover with the remainder requiring direct revegetation of
the mixed tailings/slimes materials. These operational
difficulties, coupled with the fact that the topsoil layer is
quite rich in heavy minerals, led to a series of
discussions with various landowners and a joint decision
to process the topsoil layer in certain cases rather than
preserving it for reclamation.
Figure 2. Dewatering tailings and slimes at Old Hickory
Project. The light colored dike material in the foreground is
topsoil that is forming a section of the enclosing dike wall.
Once the surface of this pit has dewatered sufficiently, it will
be limed, fertilized, and deep ripped to prepare it for
revegetation. Significant swell in the slimes results in a final
elevation above the pre-mined lands.
In practice, the combination of lateral variability
of dewatered mine soil physical properties (Fig. 3),
severe subsoil compaction, and variable topsoil
replacement seriously constrained pre-2004 pit
reclamation efforts relative to the procedures developed
by our research program and limited expected
productivity. Through early 2004, the reclaimed pits had
been successfully returned to hayland/pasture vegetative
cover, but their long-term suitability for intensive
agricultural production was questionable (10). In
fairness, however, it must be pointed out that it
necessarily takes any new combined mining/reclamation
operation several years to fine-tune and effectively
merge operating and closure procedures.
Evolving Improvements in Reclamation
In response to the soil reconstruction constraints
discussed above (lateral variability and limited topsoil),
we are working cooperatively with Iluka to develop
effective topsoil substitution strategies, particularly
through the use of deep-tilled organic amendments such
as municipal wastewater treatment biosolids (sewage
sludge). Recent modifications to water management via
the internal cross-diking discussed earlier and
manipulations of surface water decant sequences have
also limited lateral separation of tailings and slimes to
some extent. The combination of these two
improvements, coupled with Iluka’s evolving knowledge
base of pit dewatering and final grading procedures
should lead to significant incremental improvement in
the agricultural productivity potential of these post-
mining landscapes where topsoil return was not feasible.
Figure 3. Recently revegetated pit at Old Hickory
exhibiting strong lateral variability in texture due to lateral
segregation of tailings and slimes. The white patches are
areas of pure tailings while the darker-colored, better
vegetated zones were capped with a layer of finer-textured
slimes. Topsoil was not available as a cover material as this
pit was closed.
Our original reclamation prescription (as
discussed earlier) called for deep ripping and/or chisel
plowing of the reconstructed mine soils to ameliorate
grading related compaction. However, detailed soil
studies performed in the summer of 2004 coupled with
follow-up investigations with contractors revealed that
deep ripping protocols were not being followed for a
variety of reasons including their tendency to pull up
large chunks of plastic slimes that complicated final
tillage for seeding operations. Of 13 deep (2 m) soil pits
investigated in 2004, 9 contained compacted layers
within the upper 50 cm that completely limited rooting
and water percolation (Fig. 4), thereby drastically
reducing plant growth potentials. These heavily
compacted zones also limit rainfall infiltration and
increase surface runoff and associated sediment losses
following heavy rains. Based upon these findings, Iluka
immediately acquired a deep shank ripper (Fig. 5) and
initiated a series of trials on recently graded pits to
determine its efficacy at loosening the mine soils with
depth and enhancing mine soil productivity. The ripper
is pulled by a bulldozer in two passes at 90o to one
another, and the net effect was immediately apparent as
newly ripped lands infiltrated heavy rains while directly
adjacent non-ripped areas ponded water and generated
enhanced runoff. While we have not yet been able to
rigorously assess the deep subsoil effects of the ripping
practice upon crop rooting, we are convinced that this is
probably the most significant advance in mine soil
reconstruction technology at this site to date.
Figure 4. Heavily compacted mine soil generated by wet
grading of tailings/slimes and topsoil return layers without
subsequent deep ripping. The returned topsoil was dense
and platy as can be readily seen in the photo while the
subsoil bulk density was > 1.6 g/cm3. Compaction is the
major plant growth limitation in mine soils at Old Hickory,
regardless of adequacy of other factors such as pH, fertility,
and soil texture.
Figure 5. Deep ripping shank attachment acquired by
Iluka in 2004 to remediate mine soil compaction. The
ripper is pulled through reclaimed areas in two directions
at 90o to one-another. Iluka mine engineer Clint
Zimmerman (shown) was primarily responsible for
applying this technology to compaction identified by
Virginia Tech.
In 2004, a local landowner (the Carraway-Winn
family) agreed to dedicate approximately 50 ha of their
mined land to support a 10-year cooperative reclamation
research and demonstration farm. Final grading of
approximately 50% of the area was completed in the fall
of 2004 and a large replicated soil reconstruction
experiment was installed to evaluate the relative effects
of topsoil (15 cm) return vs. topsoil substitute strategies
with and without biosolids amendment. A local farmer
(Clark Farms LLC) has been employed to manage the
experiment, and the plots are large (0.3 ha each X 16)
enough to allow for full-scale and normal agricultural
operations. The row-cropping experiment will be
monitored for at least three full growing seasons and the
identical cropping sequence and management protocols
are being replicated on nearby undisturbed prime
farmland (pictured in Fig. 1) to allow for a direct
determination of crop productivity return. Over 2005,
additional hayland and forage management experiments
and demonstrations will be installed as final grading is
completed. Multiple ground water monitoring wells will
also be installed to determine the length of time that
within pit water levels take to equilibrate and to
document changes in water quality over time.
Landowner Perspectives and Sustainability
The majority of the Old Hickory ore body has been in
intensive agricultural production for over 150 years, with
extensive forestry practiced on minor inclusions of less
productive soils or wetlands. Most of the farms have
been in the same family for multiple generations, and are
< 300 ha in size. One farm in the center of the deposit
was the highest yielding (kg/ha) peanut producer in
Virginia for several years in the mid-1980’s, and large
areas of the deposit are clearly among the most
productive agricultural landscapes in the region.
However, much of the profitability of these operations
has historically been based upon federal tobacco and
peanut price support programs which have been
drastically curtailed in recent years. While there is some
uncertainty regarding how much of this landscape would
remain in intensive agricultural production over the next
20 years in the absence of mining, the inherent
agricultural productivity potential of the land is beyond
question. Thus, any decision to permanently alter these
lands via mining generates a number of questions and
implications for individual landowners, regulatory
authorities, and the Commonwealth as a whole.
On an individual landowner basis, the royalty
return value of the processed mineral is much greater
than the local current market value of prime agricultural
lands. The economic return to the landowner is further
improved when mineral-rich topsoil is processed, but
that will more than likely have an offsetting affect on
post-mining productivity potentials. The majority of
current landowners have assumed that their lands will be
returned to some level of agricultural productivity, with
varying levels of expectations among differing
Currently, our research and field monitoring
programs indicate that a return to hayland/pasture land
use potentials will be readily achievable, while intensive
row-crop agriculture will probably be limited to < 90%
of pre-mining conditions. As mentioned earlier, we are
hopeful that current improvements to the operations will
elevate post-mining productivity levels, but that is
speculative at this time. As a reference, the coal mining
farmland restoration research cited earlier indicates that
an actual and consistent return of 90 to 95% productivity
would be an outstanding outcome. Extensive or intensive
forestry should also be viable across this post-mining
landscape, and a number of unique water features and
wildlife habitat and wetland conservation landscapes are
also under development.
The development and implementation of effective
restoration protocols at the Old Hickory mineral sands
mining operation in Virginia was complicated by the
lack of a pre-existing research or industry knowledge
base, and the fact that the ore body is higher in slimes
than any mined to date. Fifteen years of collaborative
work by Virginia Tech, Iluka Resources and local
landowners has led to a detailed understanding of the
mining process and a reasonable prediction of
reclamation outcomes. Overall, with respect to the long-
term sustainability of this and similar mining operations,
it is clear that these heavy mineral deposits can be
developed and successfully returned to post-mining
agricultural and/or forestry land uses. While it is unlikely
that the most productive soils within these deposits will
be returned to their full (100%) pre-mining row cropping
potentials, recent advances in mine soil reconstruction
technologies at the site offer hope for maximizing post-
mining productivity potentials.
The support and collaboration of RGC Mineral
Resources and Iluka Resources Inc. over time is
gratefully acknowledged. In particular, Denis Brooks,
Mike Creek, Elliott Mallard, Geoff Moore, Clay Newton,
Fiona Nichols, Allan Sale, Chee Saunders, Steve Potter,
Chris Wyatt and Clint Zimmerman have worked
diligently with us over the years to improve mined land
reclamation protocols applied at Old Hickory. At
Virginia Tech, Mark Alley, Steve Nagle, Zenah
Orndorff, Phil Schroeder and Lucian Zelazny have all
contributed greatly to this long-term research program.
1. Berquist, C.R., Jr., and B.K. Goodwin (1989), Terrace
gravel, heavy mineral deposits, and faulted basement
along and near the fall zone in southeast Virginia.
Guidebook No. 5, Dept. of Geology, College of
William and Mary, Williamsburg, VA.
2. Carpenter, R.H. and S.F. Carpenter (1991), Heavy
mineral deposits in the Upper Coastal Plain of North
Carolina and Virginia. Economic Geol. 86:1657-
3. Jansen, I.J., and W.S. Dancer (1981), Rowcrop yield
response to soil horizon replacement after mining. In:
D. Graves, (Ed.), Proc. of the Symposium on Surface
Mining Hydrology, Sedimentation and reclamation.
p. 357-362. College of Engineering, Univ. Of
Kentucky, Lexington, Ky,
4. Barnhisel, R.I., and R.B. Gray (1990), Managing
restored prime farmland for corn production. In: J.
Skousen et al. (Eds) Proc., 7th Annual Meeting,
American Society for Surface Mining and
Reclamation, June, 1990, Charleston, WV, p.143-
149. ASMR, 3134 Montavesta Rd., Lexington KY.
5. Dunker, R.E., R.I. Barnhisel and R.G. Darmody
(1992), Prime Farmland Reclamation. Proc., 1992
National Symposium on Prime Farmland
Reclamation St. Louis. University of Illinois at
Urbana Champaign, 284 pp.
6. Brooks, D.R. (1989), Reclamation in Australia’s
heavy mineral sands industry. In D.G. Walker et al.
(eds.) Proc., Reclamation, a Global perspective. Rpt.
RRTAC 89-2. p. 11-26. (Alberta Land Cons. And
Reclamation. Council).
7. Daniels, W.L., L.W. Zelazny, M.M. Alley and K.C.
Haering (1991), The development of restoration
strategies for prime agricultural soils following
mineral sands mining in the Coastal Plain of the
eastern USA. In: Proc., Aust. Mining Ind. Coun. Env.
Workshop, p. 26-37 (AMIC, Dickson, ACT,
8. Daniels, W.L., M.M. Alley, L.W. Zelazny, Y.Z. Lei,
V.A.L. Groover and P.D. Schroeder (1996),
Strategies for rehabilitating prime farmlands
following mineral sands mining in Virginia, USA. In:
D. Brooks et al. (Eds.), Proc., (Vol 2) Third
International Minerals Council of Australia
Environmental Workshop, Newcastle - NSW, Oct.
14-18, p. 412-427. Minerals Council of Australia,
Dickson, ACT, Australia.
9. Daniels, W.L., P.D. Schroeder, S.M. Nagle, L.W.
Zelazny, and M.M. Alley (1999), Reclamation of
prime farmlands following mineral sands mining in
Virginia. In: S.A. Bengson et al., (eds.) Proc., 16th
Annual Meeting, American Society for Surface
Mining and Reclamation, August 13-19, Scottsdale,
AZ. p. 146-156. ASMR, 3134 Montavesta Rd.,
Lexington KY.
10. Daniels, W.L., Z.W. Orndorff, and P.D. Schroeder
(2003), Chemical and physical properties of mineral
sands mine soils in southeastern Virginia. In: R.I.
Barnhisel et al., (eds.) Proc., 20th Annual Meeting,
American Society for Surface Mining and
Reclamation, June 3-6, 2003, Billings, MT. ASMR,
3134 Montavesta Rd., Lexington KY.
... The topsoil is removed and stockpiled; it may be used to create berms around the active mining pit. Later, the topsoil is either mixed with sand tailings/clay slimes and returned to the mined-out void, or replaced on top of the tailings/clay mix (Daniels, 2003). The pit bottom is typically below the water table, and a floating dredge with a suction cutter or bucket wheel removes the unconsolidated ore and pumps the slurry to a wet primary concentrator floating in the mine pond. ...
... Environmental requirements and legislation have been imposed only in the last 30 years, and are not present still in some parts of Africa (Tyler and Minnitt, 2004). In the last 30 years, several studies have been conducted concerning the need for environmental/ecosystem studies prior to mining (e.g., Lewis, 1980;Finucane et al., 2006;Lubke and Avis, 1998;Saviour, 2012) and on post-mining recovery at some HMS locales (e.g., van Aarde et al., 1996;Brewer and Whelan, 2003;Buckney and Morrison, 1992;Daniels, 2003;Moll, 1992;Van Etten et al., 2011). ...
... Post-mine vegetation tends to be less diverse than the pre-mining natural mix, and new vegetation tends to be dominated by colonizer plants (weeds), even when seeded with original type vegetation (Brewer and Whelan, 2003;van Aarde et al., 1996). Soil in newly-rehabilitated tracts tends to be compacted by the heavy equipment used, and this has an effect on soil porosity, permeability, and productivity (Daniels, 2003). ...
Technical Report
Full-text available
Economic deposits of heavy mineral sands include numerous Paleogene, Neogene, and Quaternary deposits and some modern coastal deposits. This study provides descriptive and exploration models of South Australia’s Paleogene-Quaternary heavy mineral sand deposits accumulated in coastal environments. Virtually all of South Australia’s significant heavy mineral sand deposits were discovered in two periods: between late 1980s and early 1990s, and 2004 onwards during the period of large expenditure on exploration for this commodity. Between the two periods exploration expenditures were low and only one deposit (Kintyre) was discovered. Estimates of South Australia’s heavy mineral resources dramatically increased after 2004 because of the successful greenfield discoveries in the Eucla Basin. This study draws together diverse aspects of South Australia’s HM resources to provide an overall context for evaluation of South Australia’s HM resources. The two main objectives of this study are: - develop a better understanding of the characteristics, geometry and geological/depositional environment of sedimentary basins hosting near-surface heavy mineral deposits, mostly in former coastal environments, - facilitate prospectivity analysis of the basins and their peripheral paleovalleys by mapping paleoshorelines and paleovalleys, and developing geoscientifically and technically efficient procedures for mineral exploration based on knowledge of the geological processes associated with shoreline development in sedimentary basins and interactions with associated paleovalleys which mediate sediment supply and modify coastal environments, with possible influence on HM accumulation and preservation. This research, together with new information derived from recent HM discoveries and data on the provenance of HM in various South Australian deposits, has led to the identification of new exploration targets, as well as greater understanding of the timing and development of the sedimentary basins and peripheral paleovalleys.
... The early mining and rehabilitation history for this site was reported by Daniels (2003) at an earlier Milos SDIMI meeting. As is typical with any new mine operating under completely new closure and rehabilitation mandates, development of effective strategies to meet post-mining land-use goals took time. ...
... As is typical with any new mine operating under completely new closure and rehabilitation mandates, development of effective strategies to meet post-mining land-use goals took time. In particular, active mining and closure operations in 1997 through 2001 were characterized by a succession of inter-related challenges such as differential tail-ings+slimes settling, swell and water retention in the backfilled mining pits, severe compaction of the post-grading mine soils, and a lack of topsoil return (Daniels, 2003). The combined result was to generate an array of post-mine soil conditions that were generally much lower in potential crop productivity than the pre-mining landscapes (Orndorff et al., 2005). ...
Full-text available
Mineral sands mining for ilmenite, rutile, and zircon will disturb over 2,500 ha of prime agri-cultural farmland in Virginia and North Caro-lina (USA) over the next 20 years. Mining of the Virginia deposit was initiated in 1997 and approximately 750 ha have been disturbed to date with approximately 150 ha reclaimed to support a mix of agricultural post-mining land uses. While considerable university research and corporate effort were devoted to developing environmental management systems and recla-mation protocols for these lands, specific indica-tors of sustainability and restoration success were lacking. By 2003, it became apparent to the mining operator (Iluka Resources), local landowners/farmers, local government, and the regulatory authority that testable indicators of reclamation success were essential for long-term sustainability. Virginia Tech worked coopera-tively with all stakeholders to review the pre-existing research base and to propose reasonable expectations of post-mining soil productivity levels. The state regulatory authority reinforced its position on a number of associated issues in-cluding necessity of topsoil return and specific comparative crop yield targets. Virginia Tech, Iluka Resources, and a local leaseholder (Car-raway-Winn family) agreed to jointly manage a 45-ha research demonstration farm where the effects of alternative soil reconstruction prac-tices are being rigorously monitored for both row crops (corn and wheat) and forage produc-tion. All mined land crop yields are also com-pared to an adjacent undisturbed exceptional quality prime farmland soil. Corn and wheat yields in 2005 and 2006 were significantly above county average yields (regulatory target level) and approximately 75% of undisturbed adjacent prime farmlands. This cooperative ef-fort allows all clientele groups to objectively as-sess the post-mining productivity of these mined lands while providing an invaluable educational opportunity for the mining industry.
... Native topsoil (15 cm) is salvaged and returned back over the graded pits. Deep ripping (90 cm) and applications of lime (4 to 8 Mg/ha) and P-fertilizers (350 kg/ha) are employed to ameliorate adverse subsoil chemical conditions before application of other soil amendments or topsoiling (Daniels, 2003). ...
Full-text available
Significant deposits of heavy mineral sands (primarily ilmenite and zircon) are located in Virginia in Dinwiddie, Sussex and Greensville counties. Most deposits are located under prime farmland, and thus require intensive reclamation when mined. The objective of this study was to determine the effect of four different mine soil reconstruction methods on soil properties and associated rowcrop productivity. Treatments compared were 1) Biosolids-No Tillage, 2) Biosolids-Conventional Tillage, 3) Lime+NPK fertilized tailings (Control), and 4) 15-cm Topsoil+lime+NPK over lime+P treated tailings. Treated plots were cropped to corn (Zea mays L.) in 2005 and wheat (Triticum aestivum L.) in 2006. Yields were compared to nearby unmined prime farmland yields. Over both growing seasons, the two biosolids treatments produced the highest overall crop yields. The Topsoil treatment produced the lowest corn yields due to relatively poor physical and chemical conditions, but the effect was less obvious for the following wheat crop. Reclaimed land corn and wheat yields were higher than long-term county averages, but they were consistently lower than unmined plots under identical management. Detailed morphological study of 20 mine soil pedons revealed significant root-limiting subsoil compaction and textural stratification. The mine soils classified as Typic Udorthents (11), Typic Udifluvents (4) and Typic Dystrudepts (5). Overall, these mined lands can be successfully returned to intensive agricultural production with comparable yields to long-term county averages provided extensive soil amendment and remedial tillage protocols are implemented. However, a significant decrease (~25 to 35%) in initial productivity should be expected relative to unmined prime farmland.
The history of mining extends over thousands of years, but remediation of mine areas began only about a century ago. The relatively recent interest in remediation stems from the realization that healthy ecosystems are essential to human well-being. Mining typically has serious, negative effects on the ecology, at all levels of organization, from microbial to landscape. It may be desirable to restore the ecology and associated ecosystem services of mine areas to be similar to that of the original land prior to mining. However, this is typically not possible – even after the most successful remediation efforts, the structure of the substrate and the ecosystems supported by it are altered and biodiversity may be lower. In some cases it may be more strategic to remediate the mine waste by creating an alternative ecosystem. For example, under comparable conditions on mine wastes, wetlands often support greater biodiversity than drylands. Wetlands also tend to provide better stabilization of mine wastes than drylands and may therefore provide good alternatives for remediation, even if no wetlands existed before mining commenced. Sometimes, remediation of mine areas also provides an opportunity to compensate for ecological degradation elsewhere by providing newly created habitat.
Conference Paper
Full-text available
Significant deposits of mineral sands were discovered in Virginia (USA) in 1989. The Old Hickory Deposit is the largest ore body in the state (>2000 hal and supports a productive rowcrop agriculture based on tobacco, peanuts, corn, wheat, soybeans and cotton. In 1990 we generated simulated mine tailings and slimes from deep driliing bulk samples and employed them in a series of greenhouse experiments. With appropriate P and lime additions, mixtures of tailings and slimes (at 15% to 45% slimes) were found to equal native topsoil in productivity. In a followino greenhouse trial we evaluated the use of topsoil covers, sewage sludge additions, and sUbsoil slimes/tails mixture ratios for a wheat/com/soybeans rotation grown in large (200 L) barrels. Results indicated that appropriately limed and fertilized mixtures of tailings and slimes equaled topsoiled tailings/slimes in productivity. Field experiments were installed on pilot-scale (25 m X 60 m) mining pits in the late summer of 1995 and replicated on an adjacent undisturbed area. Half of each mining pit was topsoiled (25 cm) while the remaining half was left as either (I) mixed tails/slimes or (2) regraded subsoil over tails/slimes to simulate various pit closure scenarios. Both non-topsoiled areas received 112 T/ba of yard waste compost as a soil building amendment. The entire area was rippedldisced to ameliorate compaction and incorporate lime and fertilizer additions. The experimental area wili be taken through a wheat/soybeans/com rotation typical of the area. Results of these controlied experiments are encouraging, however, the implementation of our protocols will be complicated in practice if tailings and slimes cannot be re-blended to generate a reasonably uniform final reclaimed surface.
Approximately 22.7 million metric tons (25 million short tons) of heavy minerals, at an average grade of 6 wt percent in 377.8 million metric tons (416 million short tons) of sand, have been delineated in 19 deposits in the upper Coastal Plain of North Carolina and Virginia. These deposits formed during a worldwide, Pliocene, transgressive-regressive event that occurred between 3.5 and 3.0 Ma. The deposits formed as beach or dune sands during the regressive phase of the event over an elevation range of 96 m (315 ft) to 53 m (175 ft). -from Authors
Terrace gravel, heavy mineral deposits, and faulted basement along and near the fall zone in southeast Virginia
  • C R Berquist
  • B K Jr
  • Goodwin
Berquist, C.R., Jr., and B.K. Goodwin (1989), Terrace gravel, heavy mineral deposits, and faulted basement along and near the fall zone in southeast Virginia. Guidebook No. 5, Dept. of Geology, College of William and Mary, Williamsburg, VA.
Rowcrop yield response to soil horizon replacement after mining
  • I J Jansen
  • W S Dancer
Jansen, I.J., and W.S. Dancer (1981), Rowcrop yield response to soil horizon replacement after mining. In: D. Graves, (Ed.), Proc. of the Symposium on Surface Mining Hydrology, Sedimentation and reclamation. p. 357-362. College of Engineering, Univ. Of Kentucky, Lexington, Ky,
Managing restored prime farmland for corn production
  • R I Barnhisel
  • R B Gray
Barnhisel, R.I., and R.B. Gray (1990), Managing restored prime farmland for corn production. In: J. Skousen et al. (Eds) Proc., 7th Annual Meeting, American Society for Surface Mining and Reclamation, June, 1990, Charleston, WV, p.143-149. ASMR, 3134 Montavesta Rd., Lexington KY.
The development of restoration strategies for prime agricultural soils following mineral sands mining in the Coastal Plain of the eastern USA
  • W L Daniels
  • L W Zelazny
  • M M Alley
  • K C Haering
Daniels, W.L., L.W. Zelazny, M.M. Alley and K.C. Haering (1991), The development of restoration strategies for prime agricultural soils following mineral sands mining in the Coastal Plain of the eastern USA. In: Proc., Aust. Mining Ind. Coun. Env. Workshop, p. 26-37 (AMIC, Dickson, ACT, Australia).
Chemical and physical properties of mineral sands mine soils in southeastern Virginia
  • W L Daniels
  • Z W Orndorff
  • P D Schroeder
Daniels, W.L., Z.W. Orndorff, and P.D. Schroeder (2003), Chemical and physical properties of mineral sands mine soils in southeastern Virginia. In: R.I. Barnhisel et al., (eds.) Proc., 20th Annual Meeting, American Society for Surface Mining and Reclamation, June 3-6, 2003, Billings, MT. ASMR, 3134