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1.
Abstract. The Sleeper open pit gold mine operated from the mid-1980s
through the mid-1990s. Operations were mostly sub-water table
and extensive dewatering was required to lower groundwater
levels by 180 m. Dewatering flows peaked at 930 L/s, with most
flow contributed from an alluvial aquifer. After completion of
mining, the pit was rapidly filled with water pumped from the
alluvial aquifer to reduce the exposure time of sulfide wall
rocks and waste rocks in the ultimate pit. The pumped alluvial
groundwater provided a large volume of low total dissolved
solids (TDS), high alkalinity water that controlled the early
chemistry. The rising lake waters were amended with lime to
buffer excess acidity contributed to the lake from reactive pit
wall rocks during submergence. The pore water contained in
submerged waste rock at the base of the pit was elevated in TDS
and subsequently of higher density that the lake water. The
density contrast and waste rock location limited contributions
of waste rock pore water to the main body of the lake. Some
stratification of the early lake occurred, with shallow water
characterized by higher pH, low dissolved metals, and sulfate;
deeper water had lower pH and higher dissolved metals and
sulfate. The reservoir of alkalinity in the shallow layer mixed
with the deeper waters and created a stabilized lake with a
homogenized column that exceeded water quality expectations.
Current water quality meets all Nevada primary drinking water
standards with the exception of sulfate, TDS, and manganese,
which are slightly elevated, as predicted. Chemistry has
remained stable since development of the initial lake. 相似文献
2.
Abstract. The basic chemical properties of Tertiary (T) and Quaternary (Q) aquifers near the Piaseczno opencast sulphur mine and the
water in the open pit, along with the stratigraphy and hydrogeology of the area, were characterized to assess the feasibility
of inundating the mine with ground water. Ground water quality varied markedly in the opencast area. A distinct stratification
was noted in the pit water; total dissolved solids, calcium, chloride, hardness, and hydrogen sulphide increased from the
top water level to the bottom of the pit lake. The concentrations of SO 42- and Cl - in the opencast water were very high, especially in the hypolimnion zone. Based on our preliminary analysis, it appears that
an artificial lake formed in the Piaseczno open pit could be used in the future as a fish and wildlife habitat as well as
for recreational purposes. 相似文献
3.
Abstract. Due to operational and regulatory practicalities, pit lakes will continue to be common legacies of mine lease relinquishments.
Unplanned or inappropriate management of these geographical features can lead to both short- and long-term liability to mining
companies, local communities, and the nearby environment during mining operations or after lease relinquishment. However,
the potential for pit lakes to provide benefit to companies, communities, and the environment is frequently unrecognised and
yet may be a vital contribution to the sustainability of the open-cut mining industry. Sustainable pit lake management aims
to minimise short and long term pit lake liabilities and maximise short and long term pit lake opportunities. Improved remediation
technologies are offering more avenues for pit lakes resource exploitation than ever before, at the same time mining companies,
local communities, and regulatory authorities are becoming more aware of the benefit these resources can offer. 相似文献
4.
Abstract. The Berkeley pit lake in Butte, Montana is one of the largest accumulations of acid mine drainage in the world. The pit lake
began filling in 1983, and continues to fill at a rate of roughly 10 million liters d -1. This paper details how changes in mining activities have led to changes in the rate of filling of the pit lake, as well
as changes in its limnology and geochemistry. As of 2005, the Berkeley pit lake is meromictic, with lower conductivity water
resting on top of higher conductivity water. This permanent stratification was set up by diversion of surface water—the so-called
Horseshoe Bend Spring—into the pit during the period 2000 to 2003. However, the lake may have been holomictic prior to 2000,
with seasonal top-to-bottom turnover events. The present mining company is pumping water from below the chemocline to a copper
precipitation plant, after which time the Cu-depleted and Fe-enriched water is returned to the pit. Continued operation of
this facility may eventually change the density gradient of the lake, with a return to holomictic conditions. A conceptual
model illustrating some of the various physical, chemical, and microbial processes responsible for the unusually poor water
quality of the Berkeley pit lake is presented. 相似文献
5.
Mine void pit lakes often contain water of poor quality with potential for environmental harm that may dwarf other mine closure
environmental issues in terms of severity, scope, and longevity. This is particularly so when many pit lakes occur close together
and thus form a new “lake district” landscape. Pit lakes that can be developed into healthy lake or wetland ecosystems as
a beneficial end use provide opportunities for the mining industry to fulfil commitments to sustainability. Clearly articulated
restoration goals and a strategic closure plan are necessary to ensure pit lake restoration toward a new, yet regionally-relevant,
aquatic ecosystem, which can achieve sustainability as an out-of-kind environmental offset. Such an approach must also consider
obstacles to development of a self-sustaining aquatic ecosystem, such as water quality and ecological requirements. We recommend
integration of pit lakes into their catchments as a landscape restoration planning exercise with clearly-identified roles
and objectives for each new lake habitat and its surrounds. 相似文献
7.
Abstract. Permitting of open pit mines that intersect the
groundwater table necessitates the use of sophisticated
numerical models to determine the temporal impact of pit lake
hydraulics. However, while mine feasibility and the potential
environmental influences of open-pit dewatering can be estimated
using conventional screening-level methods, to date there have
been few published transient analytical solutions to estimate
the pit lake recovery duration and inflow rates. The
Comprehensive Realistic Yearly Pit Transient Infilling Code
(CRYPTIC) described here is based on the Jacob-Lohman equation,
modified to include the pit geometry and effects of
precipitation and evaporation from the pit lake surface as well
as the input/output of external flows. It assumes that the
aquifer is homogeneous and isotropic with laterally extensive
horizontal flow but differs from other methods in that it
includes transient inflows. CRYPTIC was used to successfully
model the Berkeley Pit Lake (Butte, Montana) recovery data and
its predictions also compared favorably with results from the
Pipeline Pit (north-central Nevada) numerical model. However,
while this analytical approach provides useful hydraulic
insights at the feasibility stage of mine planning, more
detailed analysis is required to determine critical mine
permitting requirements. For example, the lateral extent of the
drawdown cone, time to maximum extent of dewatering, and
temporal effects on springs and seeps require deployment of a
full numerical code and substantially more data. 相似文献
8.
In an arid climate, pit lake evaporation rates can exceed influx rates, causing the lake to function as a hydraulic terminal sink, with water levels in the pit remaining below surrounding groundwater levels. We present case studies from Western Australia for two mines nearing closure. At the first site, modelling indicates that waste dump covers for the potentially acid forming (PAF) material would not be successful over the long term (1,000 years or more). The second site is a case study where PAF management is limited by the current waste rock dump location and suitable cover materials. Pit lake water balance modelling using Goldsim software indicated that both pit lakes would function as hydraulic terminal sinks if not backfilled above long-term equilibrium water levels. Poor water quality will likely develop as evapoconcentration increases contaminant concentrations, providing a potential threat to local wildlife. Even so, the best current opportunity to limit the risk of contaminant migration and protect regional groundwater environments may be to limit backfill and intentionally produce a terminal sink pit lake. 相似文献
9.
Abstract. Unconsolidated sediment at the bottom of the Berkeley pit lake is a mixture of detrital silicate minerals derived from sloughing
of the pit walls and secondary minerals precipitated out of the water column. The latter include gypsum and K-rich jarosite.
The pore waters have a similar pH to the overlying lake waters (pH 3.1 to 3.4), and have similarly high concentrations of
dissolved heavy metals, including Al, Cd, Cu, Mn, Ni, and Zn. Sediment cores show that the top meter of the sediment column
is moderately oxidized (jarosite-stable). Petrography, chemical analysis and geochemical modelling all suggest a transformation
of poorly crystalline ferric compounds such as schwertmannite and/or ferrihydrite near the sediment surface to jarosite with
depth in the core. No evidence of bacterial sulfate reduction was found in this study, despite the presence of 0.3 to 0.4
wt% organic carbon in the pit lake sediment. 相似文献
10.
Abstract Lakes develop when pits from open cut mines are left to fill with groundwater. In recent years, mining companies, mining communities,
and regulatory agencies have begun to consider potential beneficial end uses for mine lakes. Beneficial end uses are unlikely
to be without environmental impacts, however, and a proper consideration of the total benefit to the community should consider
them. This paper briefly reviews potential beneficial end uses and possible environmental impacts that might arise with them
for mine lakes in the Collie Basin, a coal mining region in Western Australia. We identified eight distinct, but not necessarily
incompatible, end uses from a search of the literature on mine lakes throughout the world: recreation and tourism, wildlife
conservation, aquaculture, irrigation, livestock water, potable water, industrial water, and chemical extraction. Recreation,
conservation, and possibly aquaculture use the mine lake directly, whereas the other end uses utilise extracted water. All
end uses have the potential to have environmental effects, with the most common being an actual or perceived impact on human
health and safety. A semi-quantitative risk assessment, using published literature sources, identified wildlife conservation
as the end use with the least environmental risk, and irrigation as the end use with the greatest environmental risk. Such
risks need to be balanced against economic and social benefits. There is an urgent need for a regulatory framework to address
mine lake options. 相似文献
11.
Abstract. An analog pit lake (APL) test has been developed to
predict pit lake water quality following closure of an
equatorial copper-gold mine. The juvenile (0-9 years after
closure) pit lake (JPL) water budget will comprise 10% rainfall;
26% surface runoff; 40% wallrock runoff, and 24% deep
groundwater inflow. The mature (>65 years after closure) pit
lake (MPL) will consist of 39% rainfall; 29% surface runoff; 15%
wallrock runoff; 3% deep groundwater inflow, and 1% shallow
groundwater inflow, with the balance (13%) contributed by the
JPL. Wallrock runoff due to incident precipitation was
replicated in humidity columns, subaqueous wallrock leachate by
leaching columns of each rock type with groundwater, rainwater
by addition of sea salt to deionized water, and surface runoff
by a sample from a local creek. The solutions were combined in
aquaria and the appropriate fraction evaporated, 7% for the JPL
and 36% for the MPL. Electron microprobe analysis of
precipitates identified clays and Al, Cu, and Zn adsorbed to
ferrihydrite surfaces. A preliminary pit design resulted in an
acidic (pH 3.3) JPL containing 7 mg/L Cu. However, by modifying
the design to exclude a potentially acidgenerating andesite
unit, the JPL water quality improves (e. g., pH 6.7; Cu 0.002
mg/L). The MPL pH with the andesite would be 6.1 (Cu = 2.2
mg/L), while the final design results in a pH of 7.1 and 0.22
mg/L Cu. The APL test can also be used to corroborate numerical
models predictions and assess the efficacy of mitigation
alternatives. 相似文献
12.
While pit lakes can pose potential risks to the environment and liabilities to mining companies, they may also present opportunities for sustainable end uses, if managed appropriately. The Springer Pit Lake and Mount Polley Mine provided an opportunity to store mine waste such as tailings and mill process water while the mine repaired its tailings storage facility after a breach in its perimeter embankment, which released tailings to the downstream environment in 2014. 1 year after the breach, a water treatment plant was installed so that the pit lake could be drawn down. Frequent monitoring of water quality in the pit, combined with a calibrated and verified water quality model, shows that water quality is improving. Based on the observations that tailings, suspended solids, and associated constituents are being removed efficiently by the pit, the treatment plant was reconfigured to a “passive” mode, which did not entail the use of reagents or mechanical energy—only in-line instrumentation. 相似文献
13.
Pit lakes formed by open-cut mining may have poor water quality as a result of Acidic and Metalliferous Drainage (AMD). Water
quality remediation treatments that enhance naturally occurring alkalinity-generating processes (bioremediation) can be used
to remediate these water quality problems. Microbially-mediated sulfate reduction using carbon as an electron donor is one
approach that shows promise. Carbon amendment can be bulk organic materials, which are often cheap or free. This study investigated
a process for determining what organic materials were best for in situ pit lake AMD bioremediation in a remote mining region.
Following a literature review identifying how different organic materials facilitated sulfate reduction in AMD waters, we
evaluated availability and costs of acquiring and transporting these materials to a typical remote mine pit lake. We found
that those sourcing organic materials should focus on a mixture of sewage sludge and green waste, which are commonly available
from mining camps/service towns and from land clearing operations. 相似文献
14.
Abstract. Nearly 10,000 miles (16,000 km) of underground mine workings began flooding on April 22, 1982 when the large pumps used to
dewater the mines of Butte, Montana were shut off. In the first few months, water levels in the workings rose hundreds of
meters. Flooding continues to this day at a slower rate, nearly 25 years later. An early evaluation of the water chemistry
in the flooding mines suggested that the initially poor water quality was the result of flushing of a reservoir of stored
acidity and metals. However, a detailed water balance for the Berkeley pit, underground workings, and associated mining features
suggests an alternative explanation. During the early period of mine flooding, acidic surface water from the deactivated heap
leach operations and nearby acid rock drainage were routed into the empty Berkeley Pit, and thence drained downward and outward
into the underground mine workings, causing widespread degradation of water quality in the underlying workings. After 21 months,
the hydraulic gradients in the system reversed, causing a change in the direction of ground water flow and a gradual improvement
in water quality of the mine shafts. 相似文献
16.
Abstract.
Drainage systems in large surface mines are designed to
accomplish three basic objectives: keeping working conditions
dry, stable and safe; lowering hydrostatic pressure and
increasing the effective stress of soil to improve slope
stability; and ensuring pit floor workability. This can be
achieved with drainage facilities that include channels, water
collection sumps, and pump stations. We report the development
of a computer-aided system called Dewatering of Open Pit Mines
(DEWOP), which can assist open pit mine designers to solve
water-related problems. The system was developed in a Visual
Basic object programming language, taking advantage of
multi-user, open database connectivity, such as Microsoft
Access, for storage and processing of information. In tests at
coal and copper surface mines, it reduced drainage facilities
costs by 8%. 相似文献
17.
Pit lake waters are often contaminated by acid mine drainage (AMD) from weathering of pyritic materials exposed by mining
operations, leading to low pH, and high solute and heavy metal concentrations. Few cost-effective engineering solutions exist
for large-scale environmental remediation of AMD-contaminated pit lakes. However, various studies have demonstrated that biological
remediation strategies for remediating AMD-contaminated waters, including microbially-mediated sulphate reduction, show promise
at the laboratory-scale. The addition of acidic mine water to raw sewage and workshop wastewaters in an evaporation pond provided
an opportunity for a field-scale experiment as essentially a reversal of suggested in-situ treatment of acidic pit lakes by
addition of organic carbon. The hyper-eutrophic evaporation pond initially contained high concentrations of nutrients, a pH > 8,
high levels of sulphate (500 mg L −1), and had regular algal blooms. Soon after the addition of the AMD pit water, the evaporation pond pH fell to 2.4, and electrical
conductivity (EC) and most metal concentrations were elevated by one to two orders of magnitude. Over the following 18 months,
the pH of the pond increased and the EC and metal concentrations decreased. After only 18 months of addition of AMD, pond
water quality had returned to a level similar to that before AMD addition. These observations suggest that addition of low-grade
organic materials shows promise for remediation of acid mine waters at field scale and warrants experimental investigation.
An erratum to this article can be found at 相似文献
18.
Mine waters are a significant point source stressor for aquatic environments, not only due to their acidity and high metal concentrations, but also because of their high electrolyte concentrations. Ion-rich mine waters can disturb the seasonal mixing of lake waters, even leading to permanent stratification, i.e. meromixis. In this study, we investigated two small natural lakes receiving waters from closed Ni-Cu mines. To characterize the present chemical and physical conditions of these two boreal lakes, we collected water samples and in-situ water column measurements seasonally in 2017 and 2018. We modelled the stability of meromixis in the lakes under varying physico-chemical and meteorological conditions with the MATLAB-based open-source model code, MyLake. Chemical analyses and water column measurements show that both lakes are currently meromictic with a chemocline separating the circulating, well-oxygenated upper water from the non-circulating, hypoxic bottom water. The main anion was SO4 in both lakes, while the main cations were Ca, Mg, Na, and K. Elevated concentrations of conservative elements flowing from the mine areas are crucial in maintaining the meromixis. Modelling scenarios suggest that the meromixis would be sustained for several decades even if the external load ceased completely. Lake morphology and sheltered surroundings also seem to contribute to maintaining the meromixis in these lakes. Consequently, our results indicate that small headwaters are sensitive to persistent meromixis even when external loading is mild. 相似文献
19.
Abstract The copper mine at Kilembe in the Ruwenzori Mountains in western Uganda ceased to operate in 1978 but a steady flow of contaminants,
including Cu, Co, Ni, Zn, Cd, and sulphate, continues to enter the Nyamwamba-Rukoki River, which passes through Queen Elizabeth
National Park, and finally flows into Lake George. Lake George is quite shallow, alkaline, and highly eutrophic. Measuring
mass-flow of contaminants, water, and suspended solids in the Rukoki River near Kasese allowed us to estimate their input
into Lake George. Grid sampling of lake sediments indicated that the contaminants settle near the two mouths of the river;
low concentrations in a drill core in the centre of Lake George indicate that further dispersion within the lake is small.
Sequential extraction experiments on lake sediments and lake water analyses suggest low bioavailability of the heavy metals.
We conclude that Lake George is a highly resilient system that efficiently immobilises contaminants. Though there is no health
risk for the population under present environmental conditions, a reduction of the contaminant load is desirable. 相似文献
20.
Abstract. Microbial alkalinity production was evaluated as a method to prevent reacidification of neutralized mining lakes by acidic
ground and seepage water. We used 60 L mesocosms to represent the sediment and water column of a shallow acidic mine lake.
To enhance alkalinity production, acidic and neutralized lake waters were treated with either phosphorus (controlled eutrophication)
or organic matter (controlled saprobization). Controlled eutrophication could not produce enough autochthonous biomass as
substrate for microbial alkalinity production to change the acidity of the water. Chemical pre-neutralization of the acidic
water caused the inorganic carbon concentration to increase, but at the same time, hindered algae growth by reducing the availability
of phosphate by sorption to the freshly precipitated iron hydroxide. This effect was so strong that even high phosphorus additions
could not increase the algae biomass production. In contrast to controlled eutrophication, controlled saprobization produced
significant alkalinity. Despite inhibition of the most important alkalinity producing process, namely microbial sulfate reduction,
by low pH values, the microbial alkalinity production rate was not affected by pre-neutralization of the water column. Other
alkalinity producing processes raised the pH in the reactive zone until sulfate reduction was no longer inhibited. 相似文献
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