Tailings Storage Facility Research Articles

Oil sands tailings storage facilities: Design considerations for ease of closure

Oil sands tailings storage facilities: Design considerations for ease of closure

Spatial Mapping of Acidity and Geochemical Properties of Oxidized Tailings within the Former Eagle/Telbel Mine Site

At some orphaned and abandoned mine sites, acid mine drainage can represent a complex challenge due to the advanced tailings’ oxidation state as well as the combination of other factors. At the field scale, several parameters control sulfides’ oxidation rates and, therefore, the acidity generation. The objective of this paper is to map the acidity and geochemical properties of oxidized tailings within a closed tailings storage facility. Based on systematic sampling, various geochemical parameters were measured within the oxidized Joutel tailings, including the: Neutralization potential, acid-generating potential, net neutralization potential, neutralization potential ratio, paste pH, thickness of oxidized, hardpan, and transition zones. The different parameters were integrated in geographical information system (GISs) databases to quantify the spatial variability of the acidity and geochemical properties of oxidized tailings. The oxidized tailings were characterized by low sulfide (mainly as pyrite) and carbonate (mainly as siderite/ankerite) contents compared to unweathered tailings. Acidic zones, identified based on paste pH, were located in the eastern portion of the southern zone and at the northern tip of the northern zone.

Nitrogen limitation and calcifuge plant strategies constrain the establishment of native vegetation on magnetite mine tailings

Mine tailings are challenging substrates for ecological restoration, as the establishment of diverse native plant communities can be constrained by a range of edaphic factors. Thus, the ability to restore native vegetation communities will depend upon developing a clear evidence-base as to what types of species and communities are likely sustainably reinstated on such altered substrates. As global tailings production and the cumulative footprint of tailings storage facilities continue to grow, understanding the effect of edaphic filters on community establishment is foundational for developing effective restoration solutions for tailings. We standardised growth rate estimates derived from nine root and shoot parameters for plants grown in magnetite tailings and natural topsoil, using crops (eight species) to characterise previously identified plant responses and native plants (40 species) to understand the impact of edaphic conditions on the species pool available for restoration. The edaphic conditions of unweathered magnetite tailings select against the majority of native plant species and nutrient-acquisition guilds (approximately 75% of reference floristic biodiversity), with plant development on tailings compared with natural topsoil compromised in a number of variables in all but six species. Plant growth on tailings was limited by a lack of available nitrogen (N) and high alkalinity (pH >9), and seedling growth and development was positively associated with seed N concentration. Calcicole species and species from N2-fixing and cluster root-producing strategies performed better on tailings than calcifuge species and species without specialised nutrient-acquisition strategy or those reliant upon mycorrhizal associations. The return of plant communities native to highly weathered, acidic soils on magnetite tailings is likely unsuccessful, unless strategies to ameliorate substrate hostility through acidification of the soil profile and improving N availability are prioritised.

Integrated Management of Pig Residues and Copper Mine Tailings for Aided Phytostabilization.

There is high demand for identifying socio-environmentally sound ways to dispose of large quantities of offensive odor-generating organic residues produced by intensive livestock farming. The use of these residues as amendments at large-scale mine tailings storage facilities for in situ plant-based reclamation may be a useful alternative. We performed a greenhouse assay to evaluate effectiveness of pig slurries and the solid organic fraction of aerobic-aerated pig slurries, both treated and not treated for odor emission, as amendments for copper tailings. Different doses of slurries or the solid organic fraction of the slurries, untreated and treated with either ozone or a commercial product used to manage strong odors (Just a Drop), were incorporated into tailings and stabilized (15 d) under greenhouse conditions. L. (ryegrass) was used as bioindicator for Cu and Zn toxicity. Plant performance (shoot and root dry biomass, Cu and Zn content in leaves) and general physicochemical characteristics of substrates were evaluated. Our results showed that odor management of pig residues was possible with commercial products, and their incorporation into tailings rapidly and effectively reduced odor emission. The solid organic fraction of the slurries neutralized acidic tailings, and both pig residues increased organic matter and nutrient content in tailings while reducing extractable Cu. As a result, ryegrass productivity was significantly improved by incorporation of either slurries or their solid organic fraction into tailings in a dose-dependent form. Foliar Cu content in ryegrass was not affected but foliar Zn content increased; however, Zn remained within acceptable ranges. Both the pig slurries and their soil organic fractions proved to be valuable residues for tailings reclamation.

Carbon Sequestration in Biogenic Magnesite and Other Magnesium Carbonate Minerals.

The stability and longevity of carbonate minerals make them an ideal sink for surplus atmospheric carbon dioxide. Biogenic magnesium carbonate mineral precipitation from the magnesium-rich tailings generated by many mining operations could offset net mining greenhouse gas emissions, while simultaneously giving value to mine waste products. In this investigation, cyanobacteria in a wetland bioreactor enabled the precipitation of magnesite (MgCO3), hydromagnesite [Mg5(CO3)4(OH)2·4H2O], and dypingite [Mg5(CO3)4(OH)2·5H2O] from a synthetic wastewater comparable in chemistry to what is produced by acid leaching of ultramafic mine tailings. These precipitates occurred as micrometer-scale mineral grains and microcrystalline carbonate coatings that entombed filamentous cyanobacteria. This provides the first laboratory demonstration of low temperature, biogenic magnesite precipitation for carbon sequestration purposes. These findings demonstrate the importance of extracellular polymeric substances in microbially enabled carbonate mineral nucleation. Fluid composition was monitored to determine carbon sequestration rates. The results demonstrate that up to 238 t of CO2 could be stored per hectare of wetland/year if this method of carbon dioxide sequestration was implemented at an ultramafic mine tailing storage facility. The abundance of tailings available for carbonation and the anticipated global implementation of carbon pricing make this method of mineral carbonation worth further investigation.

Monitoring the pollution effects from a gold tailing storage facility on adjacent land through Landscape Function Analysis

Degraded landscapes adjacent to gold tailing storage facilities (TSFs) typically suffer from loss of ecosystem function as a result of seepage pollution. Restoration of these areas has become a primary concern in the fields of environmental science and management within recent decades. To assess the extent of land degradation, detailed monitoring of pollution took place over a period of 4 years on farmland adjacent to a gold TSF in South Africa. The Landscape Function Analysis (LFA) monitoring procedure was developed by David Tongway for the Australian rangelands, and has been utilised in this investigation to assess the impact of seepage pollution on the soil within the aforementioned farmland area. This paper indicated that the LFA procedure could not accurately present landscape stability and ecosystem functionality at the seepage-polluted sites within the short monitoring period presented in this study. It was established that no adverse effects on the natural vegetation were apparent, other than encroachment by Seriphium plumosum, which affected the grazing quality of the area but contributed significantly to the LFA values.

Ambient PM10 and Respirable Dust Levels Near Gold Mine Tailings Storage Facilities in South Africa

Gold mine tailings storage facilities (TSFs) contribute largely to high dust levels in the Gauteng and North‐West provinces, South Africa, and are seen as a public health concern. Currently, the South African National Ambient Air Quality Standard for PM10 is 75 μg m−3 (24 h) and no limits have yet been set for respirable PM4 levels. This study investigates the ambient PM10 levels close to three TSFs as well as respirable PM4 levels of school learners at various distances from five TSFs during the dry and wet season. The results show that the ambient PM10 levels exceeded the current limit to a large degree between three and five times during the sampling period at the three TSFs studied. Analysis of wind speed, direction, and frequency show that emissions from two of the three TSFs could have been a possible dust source contributing to some of these exceedances. The respirable PM4 levels ranged from 10–130 μg m−3 (wet season) to 3–173 μg m−3 (dry season). For two TSFs studied, sampling sites close to the TSFs showed significantly higher PM4 levels compared to those further away, which was, however, likely not the result of TSF emissions but rather from other dust‐generating sources. Overall, these results reveal high PM10 levels in surrounding communities, which should be monitored and investigated further.

Clay sedimentation and consolidation behaviour in tailing storage facilities over mine lifetime

Changes in the tailing properties (increasing clay mineral content and fine particles) and poor operation of the dewatering systems have negative impacts on the Tailing Storage Facilities (TSF) of the Shahrbabak copper complex. The design solid concentration of the thickened tailings is 63 wt.% in the Shahrbabak paste plant but it is well below the design value right now (approx. 55 wt.%). The aim of this work is to find the effects of the clay mineral and dewatering operations on the water recovery and tailing dam capacity. The understudied samples were taken from the thickener underflow and prepared at the required solid concentrations (55, 60, 65, and 70 wt.%). The results obtained showed that the initial settled density varied from 1.044 to 1.146 t/m3 by increasing the solid concentrations from 55 to 63 wt.%. Furthermore, the shrinkage limit density of the two solid concentrations was recorded at 1.52 and 1.62 t/m3, and the crack volume was estimated at 6.3% and 7.2% of the final sample volume. Also the sub-aerial tailing beach slope in the upper quarter and the remainder of TSF was too low and exhibited 2.0% and 1.0%, respectively. However, it is far from the design values (3.5%, 2.5%, and 1.7% from head of the beach to the end). Thus it is clear that the clay minerals and fine particles hold more water in their inner network and occupy a more TSF volume. Nevertheless, the beach slope can be increased by improving the thickener performance and removing the leakage and other periodic water, although it seems impractical to achieve the design value due to the changes in the tailing properties.

Mechanisms of maintenance of cytoplasmic osmotic homeostasis in bryophytes cells under salinity stress

The mechanisms of stabilization of cytoplasmic osmotic homeostasis in the bryophytes cells the participation of H + -ATPase and the intracellular ratio K + /Na + were investigated as one of the effective means of control over absorption and compartmentation of excess sodium ions in plant cells under salinity at the territory of the tailings storage facility of Stebnyk Mining and Chemical Enterprise “Polymineral” .Samples of Barb ula unguiculata Hedw., Didymodon rigidulus Hedw. and Brachythecium campestre (Müll. Hal.) Schimp. mosses were taken from 2 experimental plots in the territory of the tailings storage facility, which significantly differed in substrate salinity levels. The highest activity of ATPase was detected in B. unguiculata and D. rigidulus plants, which grew on the substrate with very high salinity level. This indicates an important role of the plasma membrane H + -pump in the adaptation of bryophytes to salt stress. In B. campestre shoots growing on the outskirts of the tailings storage with less salinity of the substrate, the enzymatic activity was found to be lower. It has been shown that the H + -ATPase activity depends on changes of the structural state of membranes induced by lipoperoxidation processes under stress conditions. The salt-tolerant B. unguiculata and D. rigidulus moss species have a lower content of TBA-active products, which positively affects on the functioning of membrane enzymes and leads to the development of general protective stress reaction. It has been shown that increasing of the H + -ATPase activity in moss cells under salinity conditions provides a removal of excess Na + ions to outside, that was confirmed by the results of our investigations of cellular localization of sodium. The sequential elution technique for determining cellular localization of cations developed for bryophytes by D. Brown and J. Walls (Brown, Wells, 1995) was used. It made possible to determine the ratio between the amount of sodium and potassium cations localized on the extracellular sites and in the intracellular matrix. In shoots of the studied moss species, a correlation between ATPase activity and the localization of sodium ions on the extracellular sites was found. This indicates an important role of H + -ATPase in eliminating of the excess cytotoxic sodium ions from moss cells under salt stress conditions. It was showed that potassium ions are important osmolytes in the bryophytes cells since under saline stress, an increase in content of potassium and K + /Na + correlation was observed in the intracellular matrix, which improves the plants tolerance to the influence of excess Na + ions. Keywords: moss, salinity, H + -ATPase, sodium and potassium content

Environmental Impact Assessment (EIA) of a gold mine tailing through the multi-criteria decision making tool

Gold mine tailings dams are a high risk part of mining as they contain hazardous materials such as cyanide, mercury and arsenic from processing operations which present a risk to the public and to the environment. When tailing dams fail, the impact is disastrous for humans and the natural environment. The International Commission on Large Dams (ICOLD) collected 221 case records of tailing facility failure incidents worldwide to determine the causes of these incidents. The main causes of these incidents and reported cases of failure were found to be lack of control during the construction, lack of control of the water balance and a general lack of understanding of the features that control safe operations. The important elements to improve the safety and stability of tailings disposal facilities are geotechnical investigation, engineered design, construction, operation and monitoring of the tailings storage facility.

In situ evaluation of performance of reclamation measures implemented on abandoned reactive tailings disposal site

The abandoned Manitou mine site produced acid mine drainage for decades. One of the site’s tailings storage facilities (TSF 2) was reclaimed in 2009 using an elevated water table combined with a monolayer cover made of low-sulphur tailings. A field investigation was undertaken from 2012 to 2015 to verify the performance of the reclamation technique in stemming the production of contaminants. This verification is based on two main criteria, i.e., the minimum water table level and maximum oxygen flux reaching the Manitou tailings. Thirteen monitoring stations were installed in TSF 2. The hydrogeological behavior and oxygen migration were investigated at each station by measuring volumetric water content, suction, water table level, gaseous pore oxygen concentration, and oxygen consumption. Analyses of field data showed that the minimum water table level criterion was reached with the exception of a portion of TSF 2 during the summer months. Oxygen fluxes reaching the Manitou tailings were determined using numerical simulations and analytical solutions; their yearly mean was many times lower than maximum targets generally used on reclaimed tailings disposal areas. The current system met the targeted performance criteria over the studied period.

Refraction Microtremor method for delineation of layers and lenses, and assessing liquefaction potential within an alluvial setting - Morobe Province, Papua New Guinea

Refraction Microtremor (ReMi) is a relatively new method in the geophysics industry. ReMi provides high resolution seismic shear wave velocity models up to 200m depth and as such has the potential of being an efficient method for assessing the soil liquefaction potential in seismically active regions.This paper presents a geophysical investigation carried out as part of a geotechnical feasibility study for a proposed Tailings Storage Facility (TSF) in the Morobe Province of Papua New Guinea. The primary objective of the investigation was to use geophysical methods to obtain subsurface parameters to assess the liquefaction potential within an interbedded and lensed clay/gravel alluvial setting. ReMi together with down hole and cross hole seismic methods were used to generate shear wave velocity information of multiple layers with depth, and in particular to define seismic velocity inversions.ReMi data was acquired using two array setups specifically targeting the top 100m of subsurface material and the top 50m of subsurface material at increased layer resolution. The data was inverted to produce shear wave velocity soundings which were correlated with the cross-hole and down-hole seismic methods, and with bore hole Standard Penetration Tests (SPT). The soundings were compiled to generate high resolutions shear wave velocity sections, analysis of which proved pertinent in defining the interconnectivity of the lensed clay/gravel and shear wave velocity variations for the calculation of liquefaction potential thresholds.

Development of a UAV-mounted system for remotely collecting mine water samples

ABSTRACTAccurate and frequent measurement of mine water quality is essential for timely management and regulatory requirements. At mines, traditional water sample collection practices are sometimes unsafe or impractical due to accessibility challenges. Unmanned aerial vehicle (UAV)-based remote water sampling has benefits in accessing small, shallow and isolated waterbodies in hazardous environments. In this study, an integrated electromechanical pneumatic system was developed to provide an effective, efficient and safer means to acquire mine water samples using UAVs. The system was tested to collect and analyse ponded water from a tailings storage facility to measure pH, electrical conductivity and dissolved oxygen.

Extreme Geochemical Conditions and Dispersal Limitation Retard Primary Succession of Microbial Communities in Gold Tailings.

Microbial community succession in tailings materials is poorly understood at present, and likely to be substantially different from similar processes in natural primary successional environments due to the unusual geochemical properties of tailings and the isolated design of tailings storage facilities. This is the first study to evaluate processes of primary succession in microbial communities colonizing unamended tailings, and compare the relative importance of stochastic (predominantly dust-borne dispersal) and deterministic (strong selection pressures from extreme geochemical properties) processes in governing community assembly rates and trajectories to those observed in natural environments. Dispersal-based recruitment required > 6 months to shift microbial community composition in unamended, field-weathered gold tailings; and in the absence of targeted inoculants, recruitment was dominated by salt- and alkali-tolerant species. In addition, cell numbers were less than 106 cells/g tailings until > 6 months after deposition. Laboratory experiments simulating microbial cell addition via dust revealed that high (>6 months’ equivalent) dust addition rates were required to effect stabilization of microbial cell counts in tailings. In field-weathered tailings, topsoil addition during rehabilitation works exerted a double effect, acting as a microbial inoculant and correcting geochemical properties of tailings. However, microbial communities in rehabilitated tailings remained compositionally distinct from those of reference soils in surrounding environments. pH, water extractable Mg, and water extractable Fe emerged as major controls on microbial community composition in the field-weathered gold tailings. Overall, this study highlights the need for application of targeted microbial inoculants to accelerate rates of microbial community succession in tailings, which are limited primarily by slow dispersal due to physical and spatial isolation of tailings facilities from inoculant sources; and for geochemical properties of tailings to be amended to moderate values to encourage microbial community diversification and succession.

A new species of Boloponera from Sekhukhuneland, South Africa (Hymenoptera, Formicidae, Ponerinae).

During an environmental impact assessment survey of a proposed tailings storage facility for a platinum mine in Sekhukhuneland, South Africa, five adult and five larval specimens of a new species of Boloponera were found while excavating soil to a depth of 10–15 cm at the base of a tree in riparian woodland. These specimens represent a 3400 km range extension and the first reported record of the genus since its description in 2006, which was based on a single specimen collected in the Central African Republic in 2001. A description of the worker and ergatoid queen of Boloponeraikemkhasp. n. is presented, with a description of the mature larva and a key to distinguish workers of the two currently known species of the genus. The taxonomic relationships of Boloponera are discussed with respect to several confirmed and newly identified autapomorphies that support its retention as a distinct genus, although closely related to Plectroctena and Loboponera. A preliminary assessment of the conservation status and discussion of potential threats to the survival of B.ikemkha is also provided. Evaluation of current data under the IUCN Red List criteria would result in B.ikemkha being assessed as Critically Endangered, but further investigation is required to test the validity of placing it in this category.

The role of hardpan formation on the reactivity of sulfidic mine tailings: A case study at Joutel mine (Québec)

The former Eagle and Telbel mine site (hereafter referred to as Joutel mine), located near the town of Joutel in the Nord-du-Québec (Canada) houses a tailings storage facility (TSF) that has been inactive since 1996. Fresh, unweathered tailings (beneath 10–30 cm of oxidized horizon) are characterized by an average sulfide content of 6–7 wt% and an average Fe-Mn-carbonate content of 20–40 wt%. The oxidation of Joutel's tailings under atmospheric conditions resulted in the precipitation of secondary phases such as ferric oxyhydroxides and gypsum. Accumulation of these secondary phases throughout the TSF caused cementation and agglomeration of grains, which decreased the porosity of the material in a horizon below the surface. This horizon, which is referred to as hardpan, is frequently encountered within fine, reactive tailings. Characterizations showed that hardpans have a highly compact texture. The formation of hardpans limits vertical water infiltration and oxygen diffusion and these layers greatly affect the global geochemical behavior of underlying tailings in the Joutel TSF by protecting the unweathered material from oxidation. As a result, the water quality of the TSF is largely controlled by the reactivity of the upper oxidized tailings horizon.Joutel's oxidized tailings showed an acidic behavior early during laboratory kinetic leaching tests despite the near absence of sulfides and neutralizing minerals. However, when unweathered tailings were added under oxidized tailings, the water became neutral and metal leaching rates were reduced. After over a year of laboratory leaching tests, hardpans formed within the columns and the natural phenomenon was reproduced under laboratory conditions.

Erosion of silty sand tailings through a geomembrane defect under filter incompatible conditions

At tailings storage facilities, a geomembrane may be used to contain tailings from relatively more permeable foundation or embankment materials. A “filter incompatible” condition may arise between the tailings and underliner materials. In this study, the potential for piping erosion of tailings through a 1 cm diameter geomembrane defect was evaluated in a series of physical experiments. The geomembrane defect was sandwiched between silty sand tailings and various underliners (DF15/DB85 = 5.6–13.5) not meeting typical retention criteria for filtration. The leakage rates and visual findings revealed that a critical stress condition existed where erosion occurred continuously for up to 24 h. This stress condition could be encountered during early deposition or development of a reclaim pond at a tailings storage facility. When allowed to occur, erosion during this stress condition resulted in subsequent leakage rates that were 2–3 orders of magnitude higher than previously observed with “filter compatible” conditions and higher stresses. Practitioners unaware of this potential for erosion near the defect may significantly underestimate leakage and underpredict pore pressures within the embankment.

Oxygen penetration and mineral stability within the San Manuel tailings, AZ

Environmental impact assessment of tailings storage facilities focuses on defining the reactivity and potential for acid rock drainage and metal leaching (ARDML) through geochemical testing of representative samples and numerical predictive calculations. The acid generation potential of tailings is dependent on the reactivity of their sulphide content which is directly proportional to the oxygen concentration within the material. As such, predicting the oxygen concentration as a function of time and depth is critical to understand the acid generation potential of tailings material. The aim of this study was to predict the oxygen flux and concentration as a function of time and depth within the San Manuel flotation copper tailings in Arizona, USA. This flow was combined with mineralogical data, including the presence of encapsulated sulphide, oxygen and moisture content to model oxidation and metal release in the tailings. Numerical simulations, using reactive transport code MIN3P, correctly reproduced the San Manuel field and analytical results when the sulphide reactivity was controlled by reducing the effective sulphide mass within the numerical models from total sulphide to available sulphide. These calculations effectively demonstrated that an effective control minimizing sulphide oxidation exists within a portion of the San Manuel tailings.

Analytical solutions for the flow depth of steady laminar, Bingham plastic tailings down wide channels

At mid to high concentrations, fine mine tailings are non-Newtonian, and their rheology is commonly expressed as Bingham plastic. Discharges of such fine materials in tailing storage facilities form shallow channels. In this short communication, exact analytic expressions to relate the volume flow per unit width and the flow depth are derived for a Bingham plastic in terms of a newly-defined dimensionless parameter. Simplified approximations, valid for the near-plug and quasi-Newtonian fluid limits are proposed.

Ambient noise Love wave tomography at a gold mine tailings storage facility

Tailings storage facilities (TSFs) are some of the most challenging structures to operate in the mining industry. Some of these structures are susceptible to liquefaction and piping failure, and need to be monitored carefully. In this study, ambient seismic noise interferometry is applied to image the internal structure of a tailings storage facility (TSF) that showed signs of increased seepage. Twenty geophones were deployed along a roughly 100 m section of the TSF and recorded continuous seismic data. The ambient noise was used to create Love wave dispersion curves between sensor pairs, which were in turn inverted to estimate the shear wave velocity of the dam wall as a function of depth. The velocity profile indicated the phreatic surface roughly 10 m below the surface, with regions near the centre of the array showing the phreatic surface as close as 3 m below the surface. These areas are spatially well correlated with the area where increased seepage was identified and the results were comparable with cone penetration tests that were performed in the area. The study showed that the analysis of ambient seismic noise can be a cost-effective, fast and non-invasive method to image the internal structure of TSFs.