Reclamation Cover Research Articles

STUDY OF LABOR COSTS FOR INSTALLATION OF THE HDPE GEOMEMBRANE OF THE RECHARGEMENT COVERING OF THE LANDFILL №5 OF THE KYIV REGION

The article presents the results of studies of labor costs for the complex process of installation of the HDPE geomembrane of the multifunctional reclamation cover of Site No. 1 of the landfill site No. 5 in the village of Pidhirtsi Obukhiv district, Kyiv region. These studies also correspond to the direction of the scientific work of the Department of Construction Technologies of the Kyiv National University of Construction and Architecture on the topic "Creation of an algorithm and an electronic database for determining time standards for construction processes" (DR No. 0121U108931), scientific supervisor prof. Tonkacheev G.M.HDPE membrane of the AGRU company, 1.5 mm thick, 5.0 m wide, 100 m long, was used for the research. The research was carried out in the area of sector №2 during the laying of a 5x100 m roll geomembrane with an area of 500 m2. 60% of the site was a horizontal surface, and 40% was a 180 degree slope.The timing was used to determine the duration of the following technological operations: unloading geomembrane rolls from a truck with an excavator; moving one roll of geomembrane to the installation site with an excavator; unpacking, rolling, stacking with trimming and leveling of the geomembrane with an excavator; placement of ballast bags with sand to hold the geomembrane (loading); dust removal of geomembrane seams before welding; welding of geomembrane panels with a double seam; inspection of geomembrane seams with a pressure of up to 2 atm, elimination of detected weld defects, applying patches to inspection sites.The experimental laying of the membrane was carried out on a 500 m2 (10 x 50 m) area of the landfill, marked with outriggers for gas drainage - 30 cm (crushed gravel fraction 20-40 mm), without the use of a geotextile layer. According to the research results, labor costs for laying 100 square meters of structured HDPE geomembrane with a thickness of 1.5 mm amounted to 4.982 man-hours, in addition, the working time of the excavator was 1.50 machine-hours.

Root colonisation effects on the key hydrogeological properties of a reclamation cover with an elevated water table

ABSTRACT The performance of reclamation cover systems could be affected by the colonization of plant roots, which may modify the hydrogeological properties of the construction materials. A four-year field investigation was conducted using six experimental cells with various soil layering designs over AMD-generating tailings reclaimed with an oxygen-barrier cover combined with an elevated water table. Both herbaceous and woody vegetation were installed on top of the cells to compare the influence on the properties of the cover material. Consecutive and undisturbed cores were collected from the cover’s functional layer in 2020 and 2021, respectively. Root parameters, such as root length density, and hydrogeological properties were measured on the core samples to assess the possible relationships between the two categories of variables. Root observation trenches were also cut in each cell to better analyze the root density and occurrence profiles. Results showed that, within the four-year monitoring period of the study, both herbaceous and woody vegetation roots mostly colonized the top overburden layer of the cell (>86% visible roots) and barely occupied the functional layer of the reclamation cover (<10% visible roots). The observed maximum desorption rates for the functional layer were lower than the predicted values, which could be a short-term effect of the fine roots. No significant impact of roots on the main hydrogeological variables controlling the oxygen barrier efficiency were noted. At the end of the four-year study period, the hydrogeological behavior of the functional layer in all cells with/without vegetation/additional soil layers was found to be similar.

Tools to improve mine closure: 10 years of research in integration of environment in the mine life cycle

Abstract Mine closure can be approached by several points of view, from the technical, engineering, ecological, up to social and governance aspects. The definition of a good mine closure should cover most, if not all, of these aspects. This article provides a review of technical and engineering-oriented research work as a partial answer to the question ‘what is good mine closure’. The article presents a ten-year research program realized in the framework of a Canada Research Chair in integration of environment in the mine life cycle. Research projects aimed at better planning mine closure and mine site reclamation from the early stages of a mining project life cycle are exposed as possible steps to strive for optimal mine waste management. At the exploration stage, geo-environmental characterization and modeling are proposed as tools to improve mine waste management planification. During mine operations, environmental desulfurization is suggested as a method to reduce environmental risks associated with sulfidic tailings and waste rock. Indeed, research has shown that acid mine drainage and metal leaching can be significantly limited via desulfurization. At the closure stage, desulfurized tailings can be used to replace at least part of natural materials used for reclamation cover systems. Research work done on other types of mine waste, such as waste rock and water treatment sludge, also show good potential for their reuse as closure material. All these tools can be integrated into the mine life cycle to better plan for closure, which ultimately will make mine closure more sustainable.

Growth and survival of native wetland species in shallow capped centrifuged tailings and co-mixed tailings: a meso-scale greenhouse study

This 3-year meso-scale greenhouse study used 55-gallon columns to evaluate the survival and growth of boreal wetland communities planted on centrifuge (CF) tailings and co-mixed (CM) tailings capped with different reclamation cover soil capping designs. The CF tailings were capped with a shallow layer (10 and 30 cm) of peat reclamation material (PRM) and the CM tailings were capped with a shallow layer (5 cm) of PRM above 15 or 35 cm of reclamation subsoil (till). After 3 years, plant survival and growth on CF tailings showed significant improvement with a 10 cm PRM cap compared to the uncapped tailings, and plants growing on a 30 cm PRM cap outperformed those on the 10 cm PRM cap. Plant growth on CM tailings was significantly improved with a soil cover containing 5 cm PRM and at least 15 cm till. Among the seven native wetland species included in this study, the top performing species in terms of survival and above-ground biomass were Salix bebbiana, Scirpus microcarpus, and Carex aquatilis.

Influence of vegetation and additional surface layers on the water balance of a reclamation cover with elevated water table

Influence of vegetation and additional surface layers on the water balance of a reclamation cover with elevated water table

Buried wood effects on macronutrient supply and microbial activity and metabolic potential in different oil sands reclamation soils in northern Alberta

Buried wood is an important yet understudied component of natural and anthropogenic soils. Nutrient immobilization as a response to wood addition during oil sands' reclamation may be a concern since surface wood is salvaged with the soil, thereby becoming buried wood in reclamation cover soils. This project investigated the impact of buried wood on macronutrient supply and microbial communities in different reclamation soils. A 60-day incubation was performed with different rates and types of wood (0%–50%, aspen and pine) and four different soils: fine and coarse forest floor-mineral mix (fFFMM and cFFMM), peat-mineral mix (PMM), and peat. Analysis of macronutrient supply rates using Plant Root Simulator (PRS™) probes and a community-level physiological profiling (CLPP) to assess metabolic potential was performed at the end of the incubation period; microbial activity was measured through soil respiration during the incubation. Responses varied by soil type; however, buried wood caused nitrogen immobilization in three soils due to an increase in the C:N ratio. Soils with lower C:N ratios like fFFMM and PMM were more susceptible to immobilization with a decrease in available nitrogen by up to 95% at a 10% of wood addition. Phosphorus immobilization was observed in cFFMM, and potassium supply increased at 20% of wood and above. Soil microbial activity and metabolic potential increased but no significant changes in the soil profiles were observed. The findings of this study demonstrate that buried wood increases the soil C:N ratio and can potentially cause nitrogen immobilization when added by 10% of volume or more.

Properties of HDPE Geomembrane Exhumed 20 Years After Installation in a Mine Reclamation Cover System

Properties of HDPE Geomembrane Exhumed 20 Years After Installation in a Mine Reclamation Cover System

Understanding Willow Transcriptional Response in the Context of Oil Sands Tailings Reclamation.

One of the reclamation objectives for treated oil sands tailings (OST) is to establish boreal forest communities that can integrate with the surrounding area. Hence, selection of appropriate soil reclamation cover designs and plant species for revegetation are important aspects of tailings landform reclamation and closure. Research and monitoring of the long term and immediate impacts of capped OST on the growth and survival of native boreal plant species are currently underway. However, plant responses to OST-associated toxicity are not well known at the molecular level. Using RNA sequencing, we examined the effects of three types of OST on the willow transcriptome under different capping strategies. The transcriptomic data showed that some genes respond universally and others in a specific manner to different types of OST. Among the dominant and shared upregulated genes, we found some encoding protein detoxification (PD), Cytochrome P450 (CYPs), glutathione S-transferase regulatory process (GST), UDP-glycosyltransferase (UGT), and ABC transporter and regulatory process associated proteins. Moreover, genes encoding several stress-responsive transcription factors (bZIP, BHLH, ERF, MYB, NAC, WRKY) were upregulated with OST-exposure, while high numbers of transcripts related to photosynthetic activity and chloroplast structure and function were downregulated. Overall, the expression of 40 genes was found consistent across all tailings types and capping strategies. The qPCR analysis of a subset of these shared genes suggested that they could reliably distinguish plants exposed to different OST associated stress. Our results indicated that it is possible to develop OST stress exposure biosensors merely based on changes in the level of expression of a relatively small set of genes. The outcomes of this study will further guide optimization of OST capping and revegetation technology by using knowledge based plant stress adaptation strategies.

Climate change risks and vulnerabilities during mining exploration, operations, and reclamation: A regional approach for the mining sector in Québec, Canada

ABSTRACT Climate change (CC) has already and will continue to have a significant impact on the mining sector. A comprehensive and thorough analysis was performed to evaluate the risks and vulnerabilities resulting from CC during the exploration, operation, and reclamation phases of the mining life cycle. This analysis focused on six mining regions in Québec. Climate scenarios were produced for each region and, along with a literature review, used to assess the effects of CC on the mining sector. The results were presented to a panel of experts who highlighted the risks for each activity at each phase of the mining life cycle. A second group of experts evaluated the level of risk and the mining industry’s vulnerability for each risk identified by the first group. Six main risks due to CC were identified: activity schedule disruptions, loss or limitation of site accessibility, water management issues, instabilities and failures of storage facilities, operations infrastructure instabilities, and reduction of reclamation cover performance. The mining experts performed a Delphi-type survey for each mining activity to determine the risk level for each region, leading to the production of a risk matrix. Results indicate that CC is expected to particularly affect reclamation cover performance, and extreme climate events are projected to have significant impacts on operations. Vulnerability levels were assigned by a third group of experts based on the industry’s ability to adapt to these risks. Results showed a low vulnerability for exploration, low to high vulnerability for operations, and low to very high vulnerability for reclamation.

Approaches to the selection of measures to ensure the safety of closed landfills for the disposal of solid municipal waste

The approaches to the choice of measures to ensure the environmental safety of closed facilities for the disposal of solid municipal waste (MSW) are considered. Laws of the Russian Federation in terms of requirements for ensuring the safety of waste disposal facilities during the operational and reclamation periods have been studied. Scenarios of the conduct of processes at MSW landfills after reclamation are presented. The article presents the results of engineering and geological research: a comprehensive study of engineering and geological and hydrogeological conditions of the site, composition, condition and properties of soils, the activity of geological processes for making design decisions. Field engineering and geological work, soil sampling from wells have been carried out. Laboratory research of soil samples has been carried out in a soil laboratory. The project of reclamation cover of MSW landfill has been completed, including geosynthetic materials and natural soils, a network of pipelines supplying filtrate for recirculation has been calculated, and a set of work and selection of vegetation at the biological stage of reclamation have been justified. Scenarios of the conduct of processes in the course of reclamation of a waste disposal facility are considered in the case of application of the filtrate recirculation technology with preliminary pH-regulation by changing the structure of the landfill in the first year after reclamation and according to the scheme of the section of the reclaimed landfill upon reaching the stage of destruction of the biodegradable part of the waste. The advantages of the developed reclamation pavement are shown: high cultivation capacity, preservation of drainage properties at high loads, reduced costs for excavation and crushed stone laying, high chemical resistance and environmental friendliness of the material.

Simulation of water storage in a reclamation cover incorporating tailings consolidation

Successful reclamation of mine tailings requires effective management of the contaminated water generated by the consolidation of tailings over time. Due to uncertainty in predicting consolidation-induced water release, mine planners often use simulation models to prepare for a range of anticipated scenarios. This paper describes the development of the Tailings Management Simulation Consolidation model (TMSim-Consol) using the GoldSim software. TMSim-Consol simulates tailings settlement over time and the upward flow of pore water due to consolidation. The advantages of using system dynamics simulation tools are illustrated by the inherent transparency of the numerical method to end users. A hypothetical reclamation set-up consisting of an oil sands thickened tailings (OSTT) deposit capped by a sand layer was simulated under a range of initial tailings properties. The simulation results showed that soil water storage in the sand cap was highly sensitive to the initial solids contents of the underlying OSTT. To limit the release of contaminated water at the surface, the initial solids content of OSTT needs to be at least 65% before sand capping.

Do Weeds Hinder the Establishment of Native Plants on a Reclaimed North American Boreal Mine Site?

The majority of plant diversity in the boreal forest of northern Alberta, Canada is comprised of native understory plant species that are continuously facing competition from other species, including both undesirable native and weedy species. In oil sands mine reclamation, cover soils rich in organic matter are used to cap overburden materials. The aim of this study is to understand the role of weeds on different reclamation cover soils (forest floor-mineral mix and peat-mineral mix) and determine if they hinder the establishment of the native plant community. This study was conducted four growing seasons after site establishment in June 2019. At that time, both soil types had approximately 45% total cover, had 21 species per plot, and were composed of mainly native vegetation. Competition from non-native forbs (11% average cover, mainly Sonchus arvensis and Melilotus alba) did not seem to impact the development of the native vegetation community on either soil type given the high cover and richness of native forbs. However, native graminoids (predominantly Calamagrostis canadensis) were associated with reduced native forb cover and richness at graminoid cover greater than 17%. Overall, non-native forbs appeared to have little impact on the native forb community on either soil type while native graminoids had a negative influence. We suggest that the classification of what is considered an undesirable weedy species should be evaluated in the context of ecosystem management goals rather than simply the presence of non-native species.

Aboveground and Belowground Colonization of Vegetation on a 17-Year-Old Cover with Capillary Barrier Effect Built on a Boreal Mine Tailings Storage Facility

Acid mine drainage is an important environmental risk linked to the surface storage of reactive mine tailings. To manage this problem, a cover with a capillary barrier effect (CCBE) can be used. This oxygen barrier cover relies on maintaining a fine-grained material layer (moisture-retaining layer, MRL) with a high degree of saturation. CCBEs can be colonized by surrounding plants. Plant roots pump water and could impact CCBE’s performance. This performance is predicted with unsaturated water flow numerical models in which vegetation parameters can be included. Vegetation parameters may be specific in a CCBE environment. Therefore, analyzing and quantifying the vegetation that colonizes this type of cover is necessary. Plant colonization was investigated through cover and density surveys on 12 transects on a 17-year-old CCBE in the mixed forest of Quebec, Canada. Then, aboveground vegetation and root colonization intensity at three depths in the MRL were characterized on 25 plots of five dominant vegetation types (Salix, Populus, Alnus, Picea sp., and herbaceous species). The mean root length density under plots dominated by Salix sp. was higher than in the other plots. Root colonization of the MRL was concentrated in the first 10 cm and occurred under all woody and herbaceous species as well. This work quantitatively describes, for the first time, the vegetation colonizing a CCBE both at the above- and belowground levels. These data will be useful to better predict the long-term performance of this engineered reclamation cover.

Resistance of a soapstone waste rock to freeze-thaw and wet-dry cycles: implications for use in a reclamation cover in the Canadian Arctic

Engineered covers are commonly used to control the potential environmental problems related to acid mine drainage and contaminated seepage from tailings and waste rock storage facilities. Cyclical environmental weathering processes, such as freeze-thaw and wet-dry cycles, can cause rock degradation. However, these processes are usually not explicitly considered when selecting coarse-grained geomaterials for use as cover materials, even though they could be responsible for a decrease in cover performance over time. This study assesses the durability of a non-potentially acid-generating soapstone waste rock unit with respect to freeze-thaw and wet-dry cycles. This waste rock is intended for use as a cover material for the reclamation of mine tailings and waste rock storage facilities at a site in the Canadian Arctic. An experimental approach was developed based on existing standard and non-standard laboratory methods. Degradation tests were conducted on rock cores, rock slabs, and < 50-mm granular materials. These tests examined changes in selected physical and mechanical properties before and after 20 and 80 freeze-thaw and wet-dry cycles. The high density, low water absorption index, and low apparent porosity of the fresh waste rocks suggested excellent rock durability, which was confirmed by the degradation tests that showed acceptable mass losses and negligible evolution of the material’s physical and mechanical properties over time. Considering the results of this study, the studied waste rock unit was identified as an excellent construction material for mine closure purposes. The experimental approach developed for this study could be included in cover design methodologies and applied widely in the selection of rocks for use in mine reclamation schemes in cold regions.

Using Statistical and Dynamical Downscaling to Assess Climate Change Impacts on Mine Reclamation Cover Water Balances

The oil sands industry in Canada uses soil–vegetation–atmosphere-transfer (SVAT) water balance models, calibrated against short-term (<≈ 10 years) field monitoring data, to evaluate long-term (≈60 years) reclamation cover design performance. These evaluations use long-term historical climate data; however, the effects of climate change should also be incorporated in these analyses. Although statistical downscaling of global climate change projections is commonly used to obtain local, site-specific climate, high resolution dynamical downscaling can also be used. The value of this latter approach to obtain local site-specific projections for mine reclamation covers has not been evaluated previously. This study explored the differences in key water balance components of three reclamation covers and three natural sites in northern Alberta, Canada, under future, site-specific, statistical, and dynamical climate change projections. Historical meteorological records were used to establish baseline periods. Temperature datasets were used to calculate potential evapotranspiration (PET) using the Hargreaves–Samani method. Statistical downscaling uses the Long Ashton Research Station Weather Generator (LARS-WG) and global circulation model (GCM) projections of temperature and precipitation. Dynamical climate change projections were generated on a 4 km grid using the weather research and forecasting (WRF) model. These climate projections were applied to a physically-based water balance model (i.e. Hydrus-1D) to simulate actual evapotranspiration (AET) and net percolation (NP) for the baseline and future periods. The key findings were: (a) LARS-WG outperformed WRF in simulating baseline temperatures and precipitation; (b) both downscaling methods showed similar directional shifts in the future temperatures and precipitation; (c) this, in turn, created similar directional shifts in future growing season median AET and NP, although the increase in future NP for LARS-WG was higher than that for WRF. The relative increases in future NP were much higher than the relative increases in future AET, particularly for the reclamation covers.

Modelling nitrogen mineralization and plant nitrogen uptake as affected by reclamation cover depth in reclaimed upland forestlands of Northern Alberta

Early forest re-establishment in landforms constructed from materials such as overburden or mine waste is partly determined by nitrogen (N) availability in reclamation covers. Here we examined whether the ecosystem model ecosys which simulates key processes governing N availability such as mineralization, plant N uptake and N return to soil through litterfall could be used to forecast potential N limitations for forest re-establishment in these constructed landforms. In this study, N cycling was simulated and tested against measured soil, foliar and surface litter N concentrations with three soil covers differing in thickness (35, 50, and 100 cm) in a 17-year-old forest reclamation site and in an analogue natural forested site in northern Alberta. Overall, results from this study demonstrated the applicability of the ecosys model in predicting nutrient cycling in reclaimed upland forestlands. Results of this study highlight the importance of optimum cover depth to ensure sufficient N is available for plant growth. Even though the modelled net N mineralization, N uptake and thereby plant productivity increased with cover depth, the foliar and surface litter N concentrations did not. A non-linear relationship between total soil nitrogen (TN) stocks and modelled net N mineralization indicated that cover depth, which determines TN stock, had little effect on net primary productivity beyond a threshold TN. This threshold was 17 Mg N ha−1, similar to TN for the 100 cm cover, giving a net N mineralization rate of ~ 3.5 g N m−2 year−1, and this was attributed to reduced microbial activity in deeper soil layers.

Modeling salt redistribution and plant growth in reclaimed saline-sodic overburden upland forests: A case study from the Athabasca Oil Sands Region, Canada

Migration of salts from overburden/mine spoil with elevated salinity and sodicity into placed soil reclamation cover materials can adversely affect forest growth. In this study, we explored whether the ecosystem model ecosys which uses water potential and salt concentration gradients to simulate lateral and vertical water and solute fluxes can be used to determine the effects of salt redistribution on plant productivity in reclaimed landforms. In this study, salt transport and consequent effects on plant growth were simulated and tested against electrical conductivity (EC) and plant growth measured with soil cover depths of 35 cm, 50 cm and 100 cm in a 17-year-old forest reclamation site on a slope constructed on saline-sodic overburden in Northern Alberta. Overall, results from this study demonstrated the applicability of ecosys in predicting salinity effects on forest productivity in reclaimed landscapes. The modelled results showed that the upward salt movement from overburden to coversoil was influenced by the cover depth as observed in the measured values. Upward salt movement into the covers equilibrated with modelled downslope salt discharge after nine years from reclamation, maintaining a stable EC profile in the root zone. Even though modelled aspen vs. white spruce growth was adversely affected by salinity in shallow covers (≤50 cm depth) during dry years, long-term plant productivity in all the covers did not change markedly under the current climate. A clear topographical effect on salinity in the reclamation covers was not found during the study period, although the modelled salt discharge indicated a risk of salinization in downstream areas.

Calibration and application of quality-scoring functions using soil-forest productivity relationships in land reclamation

Soil-forest productivity has been studied over decades, especially for North American boreal forests; however, there has been little effort to quantitatively incorporate this relationship into frameworks of soil quality assessment (SQA). The need for such framework is critical as land reclamation and ecosystem restoration are expected to quantitatively demonstrate the redevelopment of functional soil-plant systems in spatial and/or temporal dimensions for closure of disturbed sites. The objective of this research was to assess three potential options for calibrating soil-forest productivity relationships into a SQA framework using scoring functions, while demonstrating applications in land reclamation. Using Alberta oil sands reclamation as a case study, soil-forest productivity was calibrated by i) stepwise regression of soil and forest productivity indicators, ii) use of GYPSY to model pre-disturbance growth trajectories while treating soil as categorical variable, and iii) use of process based models HYDRUS 1D and BIOMES-BGC to estimate soil and plant productivity parameters such as available water holding capacity, leaf area index and net primary productivity. All three approaches provided adequate data for calibrating the relationship into existing SQA frameworks producing soil quality-scoring functions (SQF), although the regression approach will require more rigorous validation and constraining of the SQF in comparison to the other two options. Applications of the SQF include temporal assessments of plant’s growth rate of reclaimed stands and testing the effect of reclamation cover design factors on forest productivity.

Modelling plant water relations and net primary productivity as affected by reclamation cover depth in reclaimed forestlands of northern Alberta

Success in establishing upland forests on landforms constructed from overburden is determined by the characteristics of the reclamation soil covers and depth. We explored whether an ecosystem model that uses water potential gradients to simulate soil-plant-atmosphere water transfers can be used to forecast effects of water availability on plant water relations and net primary productivity (NPP) with different cover depths in these constructed landforms. Plant water relations and growth were simulated with ecosys and tested against measured soil moisture content, rooting depth, transpiration, leaf area and biomass production in three soil cover depths over 5 years. Shallow reclamation soil cover depth caused greater water potential gradients and less soil water content, tree water uptake and growth to be modelled, consistent with measured data. Modelled transpiration increased nonlinearly with increasing cover depth, indicating a threshold depth above which additional gains in transpiration and hence NPP would be limited. This study highlights the importance of sufficient cover depth on forest community end-land use re-establishment. It also demonstrated that a terrestrial ecosystem model such as ecosys can be a useful tool in forecasting land capability for reclamation soil covers of different depths and properties under diverse climates.

Plant community composition and tree seedling establishment in response to seeding and weeding treatments on different reclamation cover soils

The majority of plant diversity in North American boreal forests is comprised of understory plant communities undergoing continuous interspecific competition. Anthropogenic activities, particularly surface mining, have introduced higher severity disturbances that not only remove vegetation, but also modify soil. During reclamation, soils used to cap overburden materials have inhibited native plant growth and increased weed invasion. This study aimed to examine the effectiveness of seeding and weeding treatments for promoting the establishment of native understory plant communities, as well as a common deciduous tree species, on three different reclamation cover soils (forest floor – mineral mix, peat–mineral mix, and transitional). The broadcasting of a native forb seed mix was not successful on any of the cover soils, whereas weeding affected each cover soil differently. With weeding, the forest floor – mineral mix and transitional cover soils experienced a decrease in the relative abundance of introduced forbs and an increase in the relative abundance of graminoids. The increase in graminoid cover on the forest floor – mineral mix was mostly attributed to the expansion of Calamagrostis canadensis (Michx.) P. Beauv. Overall, weeding effectively eliminated introduced plant species, allowing competitive native grasses to establish. However, weeding may have unintentionally hindered the development of a native understory plant community via the over-establishment of grass on reclamation sites.