Research Progress of Environmental Studies of a Mining Facility for Land Restoration (Using the Example of a Mining Enterprise in the Karaganda Region)

Abstract

This article is devoted to the crucial actual problem of the restoration of lands disturbed by the mining industry. It has been determined that before the reclamation of disturbed lands, it is essential to conduct an environmental impact assessment. The main objective of the research is to find and study the most optimal methods for reducing the technogenic impact of the mining industry on the environment by restoring disturbed areas. The object of the study was a mining enterprise in the Karaganda region. The Karaganda region was chosen for the study due to being the one with the most mining industry. After the extraction of mineral resources, the territories of the region became the most vulnerable and required the clearest solution for land restoration, taking into account the physical and geographical conditions. The work includes a statistical analysis of historical data on the state of disturbed territories of the Karaganda region, and laboratory and field studies. The comprehensive study revealed a clear need to restore disturbed lands. This will prevent further degradation of land resources and will make it possible to use them for new agricultural purposes. For the first time, studies were conducted for various soils, including technogenic soils, typical for areas where mining enterprises are located. For the first time, a reclamation algorithm has been developed for a mining enterprise in the Karaganda region, taking into account engineering and geological surveys.

1. Introduction

The issue of restoring lands disturbed by the extraction of minerals, including the territories of mines, open-pit coal mines, storage facilities for various industrial wastes and waste dumps, is relevant for mining regions [1]. There are 4563 mining enterprises operating in the Karaganda region of the Republic of Kazakhstan (1 July 2024) [2].

The volume of mining production is currently due to the intensive use of natural resources, the growth of production waste and the deterioration of the environment as a whole. There are 250.6 thousand hectares of disturbed land in Kazakhstan (2024) [3]. Dust drift from open-pit mines and dumps, dry beaches of tailings and ash dumps causes significant damage to the environment [4,5,6]. In addition to the constant excess of dust content in the atmospheric air, there is also an indirect impact on the environment [7]. This factor should be considered permanent, because atmospheric dust, settling on adjacent territories, pollutes the Earth’s surface, and when subsequently dissolved, chemical compounds migrate into the soil and ultimately into groundwater. Pollution of soils where vegetables are grown with heavy metals is of increasing concern due to the potential health risk through the food chain. Therefore, it is important to prevent the spread of exposure [8,9,10]. The problem of the restoration and transfer of lands to agricultural or urban use is extremely relevant for the economy of the region and the country. The novelty of the study is that it is extremely important to primarily assess the disturbed lands and choose the most optimal solution for the restoration of disturbed lands, since not all existing methods of reclamation are suitable for the Karaganda region. The selection of restoration methods was based on the physical and geographical features of the territory.

Bioremediation is a technology that uses the metabolic activity of biological objects such as plants, microorganisms or animals to decompose, transform or immobilize pollutants, thereby restoring damaged ecosystems [11]. It is necessary to take a comprehensive approach to studying the issues of land restoration, bioremediation and the selection of the best environmental technologies [12,13]. Restoration of disturbed lands is a complex multifunctional process, but a well-planned biological stage of reclamation (phytomelioration, improvement in soil quality) ensures the restoration of ecosystem services [14,15]. At this stage, soil quality plays a decisive role [16,17,18].

Rapid industrial development causes the loss of natural resources, pollution of the environment and imbalance in natural processes. In order to preserve natural resources from depletion and pollution in the context of increased extraction and production, rationalization of resource use must be a key factor.

The most profound and large-scale changes in the natural environment and appearance of territories are manifested in industrial landscapes of the appropriating type, for example, with quarry–dump geocomplexes of mining industries (Figure 1). Here, the morpholithogenic basis (relief and geological structure) of the landscape and other related properties change radically. Depending on the type of technogenic landscape, the direction of land restoration is selected.

Restoration of disturbed lands is not only a way to reduce the negative impact on nature, but also to preserve resources for their further use in the economic development of countries [19]. In addition, in slope restoration, engineering measures such as retaining walls and slope protection, combined with vegetation planting, effectively prevent geological disasters such as landslides [10,11].

The aim of the work is to find and justify the most optimal methods for reducing the man-made impact of mining and mining and processing industries on the environment by reducing emissions from storage facilities, as well as finding ways to restore disturbed areas.

Currently, there are a significant number of different technologies for the restoration of lands disturbed by mining operations [11]. For example, in the process of environmental restoration, the company uses unmanned aerial vehicles to transport horizontal partitions and green seedlings, which is not only efficient and fast, but also eliminates the safety risks associated with manual transportation [20].

However, in practical application, the restoration technology must be adjusted considering the climatic features, geological structure, social characteristics of the territory and environmental pollution in the area of the mining enterprise.

This is necessary from the point of view that the territories after reclamation should be used. This article is based on research for the industrial territories of Kazakhstan. In Kazakhstan, in particular, in the Karaganda region, there are a significant number of industrial enterprises for the extraction and processing of mineral resources. Consequently, the natural environment of this area is incredibly vulnerable and the lands require restoration and a special ecological approach to this.

2. Materials and Methods

To analyze the characteristics of the disturbed land area, materials from engineering–geological and engineering–hydrogeological surveys from previous years were used, and additional field and laboratory studies were carried out within the framework of this project. Engineering–geological surveys include work on studying the territory for reclamation. The goal is to obtain data on the geological conditions, composition and properties of soils, groundwater levels and other factors affecting the reclamation and further exploitation of lands. The results of these studies are necessary for selecting reclamation material. Based on this, various soils were selected for the study: ash, rocky soil, pulp and natural soil.

Due to the fact that the Karaganda region is subject to strong industrial impact and the lands are transferred to the category of “reserve lands unsuitable for agriculture”, disturbed lands must be returned to the category of “resources”. Therefore, the studies are aimed at finding and substantiating the most optimal methods for reducing the technogenic impact of the mining industry on the environment by restoring disturbed areas.

One mining enterprise in the Karaganda region was selected as the object of study. After the extraction of mineral resources, the territories of the region became the most vulnerable and required the most precise decision on land restoration, taking into account the physical and geographical conditions. The Karaganda region is the most industrially complex territory and the methods of land restoration suitable for it will be suitable for other territories.

The legal basis for environmental impact assessment in the Republic of Kazakhstan is a number of regulatory, regulatory–technical, regulatory–methodological and legal acts. Environmental legislation of the Republic of Kazakhstan is based on the Constitution of the Republic of Kazakhstan, consisting of the Environmental Code and other regulatory legal acts of the Republic of Kazakhstan [21,22].

Below is a list of the main environmental laws of the Republic of Kazakhstan and their provisions. The Environmental Code of the Republic of Kazakhstan regulates relations in the field of protection, restoration and preservation of the environment, and the use and reproduction of natural resources in the implementation of economic and other activities related to the use of natural resources and impact on the environment, within the Republic of Kazakhstan [21]. The Law of the Republic of Kazakhstan, “On Specially Protected Natural Areas”, defines the legal, economic, social and organizational foundations for the activities of specially protected areas [23]. The Code of the Republic of Kazakhstan “On Subsoil and Subsoil Use” regulates the implementation of subsoil use operations in order to ensure the protection of the interests of the Republic of Kazakhstan and its natural resources, rational use and protection of the subsoil of the Republic of Kazakhstan, protection of the interests of subsoil users and creation of conditions for the equal development of all forms of management, strengthening the rule of law in the field of subsoil use relations [24]. The Land Code of the Republic of Kazakhstan [25] regulates land relations and ensures the rational use and protection of land. The Law of the Republic of Kazakhstan “On the Protection, Reproduction and Use of Wildlife” ensures effective protection, reproduction and rational use of wildlife, and education of present and future generations in the spirit of a careful and humane attitude towards wildlife [26]. The Water Code of the Republic of Kazakhstan regulates water relations in order to ensure rational use of water for the needs of the population, economic sectors and the natural environment, protection of water resources from pollution, contamination and depletion, and prevention and elimination of harmful effects of water, strengthening the rule of law in the field of water relations [27].

Environmental impact assessment is a procedure within the framework of which the possible consequences of economic and other activities for the environment and human health are assessed, measures are developed to prevent adverse consequences (destruction, degradation, damage and depletion of natural ecological systems and natural resources) and to improve the environment, considering the requirements of the environmental legislation of the Republic of Kazakhstan.

Environmental impact assessment is necessary to determine the environmental and other consequences of management and economic decisions, to develop recommendations for improving the environment and to prevent the destruction, degradation, damage and depletion of natural ecological systems and natural resources.

Principles of environmental impact assessment (EIA).

The EIA is carried out on the basis of the following principles:

(1) Mandatory—the EIA procedure is mandatory for any type of economic and other activity that may have a direct or indirect impact on the environment and public health.

The development and implementation of projects for economic and other activities that affect the environment without an impact assessment procedure is prohibited.

(2) Integration (comprehensiveness)—consideration of issues of the impact of the planned activity on the environment, local population, agriculture and industry is carried out in their relationship with technological, technical, social, economic, planning and other design decisions.

(3) Alternatives—the assessment of consequences is based on the mandatory consideration of alternative design solutions, including the option of abandoning the planned activity (“zero” option).

(4) Sufficiency—the level of detail in conducting the EIA should not be lower than that determined by the environmental significance of the impact of the planned activity on the environment, local population, agriculture and industry.

(5) Conservation—the planned activity should not lead to a decrease in biological diversity, a reduction in bio productivity and biomass of territories and water areas or a deterioration in the vital properties of natural components of the biosphere in the zone of influence of the planned activity.

(6) Compatibility—the planned activity should not worsen the quality of life of the local population or cause irreparable damage to other types of economic activity, agriculture, flora and fauna.

(7) Flexibility—the EIA process varies in scale, depth and type of analysis depending on the specific nature of the planned activity and the type of documentation.

(8) Public participation—during the EIA process, public access to EIA information is ensured and public hearings (public discussions of EIA materials) are held.

In the process of developing pre-planning, pre-project and project documentation justifying economic and other activities in the Republic of Kazakhstan, the EIA procedure is carried out in the order of sequential actions, each of which ends with the conclusion of the state environmental assessment.

The form of development of the EIA, the completeness of the study, the volume of materials used, the level and detail of environmental research and design and survey work depend on the design stage, as well as the scale and intensity of the impact of the planned economic and other activities on human health and the environment.

EIA materials are drawn up as a document, the level of development of which corresponds to the design stage. They are an integral part of pre-design and design documents.

EIA—“Environmental Impact Assessment” provides for a detailed analysis in full of all aspects of the impact of specific objects and structures of the planned economic activity on the environment.

According to Article 39 of the Environmental Code of the Republic of Kazakhstan [21], “in the process of assessing the impact on the environment, the following must be taken into account:

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Direct impacts—impacts directly caused by the main and related types of planned activities in the area where the facility is located;

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Indirect impacts—impacts on the environment that are caused by indirect (secondary) factors arising as a result of the implementation of the project;

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Cumulative impacts—impacts that arise as a result of continually increasing changes caused by past, present or reasonably predictable actions accompanying the implementation of the project.”

The EIA includes the following materials on environmental components:

(1) Air environment:

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Characteristics of climatic conditions necessary for impact assessment;

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Characteristics of the current state of the air environment (a list of pollutants emitted into the atmosphere, indicating the rate of excess of the maximum permissible concentration (MPC) or oriented safe exposure levels (OSEL) based on available data from in-kind measurements);

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Sources and scales of estimated chemical pollution: at the maximum equipment load envisaged by the project, as well as at possible salvo and emergency emissions. Calculations of expected air pollution are carried out considering existing, under-construction and planned-for-construction enterprises (facilities) and existing background pollution;

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Introduction of low-waste and waste-free technologies, as well as special measures to prevent (reduce) emissions into the atmosphere at a level consistent with advanced global experience;

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Assessment of the consequences of pollution and measures to reduce the negative impact.

(2) Water resources:

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Hydrographic characteristics of the territory;

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Characteristics of water bodies potentially affected by the planned activity (using data from the closest observation sections);

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Hydrological, hydrochemical, ice, thermal, velocity regimes of the subsoil.

(3) Land resources and soils:

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The state and conditions of land use, the land balance of the territory planned for the placement of the facility and adjacent farms in accordance with the type of ownership, proposed changes in land management, calculation of losses in agricultural production and damages to land users (owners) subject to compensation during the creation and operation of the facility;

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Characteristics of the current state of the soil cover in the impact zone of the planned facility (soil map with site quality scores, water–physical, chemical properties, pollution, disturbance, erosion, deflation, fertility and mechanical composition of soils);

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Characteristics of the expected impact on the soil cover (mechanical disturbances, chemical pollution), changes in the properties of soils and grounds in the zone of influence of the object as a result of changes in geochemical processes, the creation of new relief forms due to the redevelopment of the surface of the territory, the activation of natural processes, pollution by production and consumption waste.

In the process of conducting an environmental impact assessment, both negative and positive effects of the impact of the enterprise’s input on various spheres of human activity must be taken into account.

The study analyzed scientific publications by various world authors.

In the scientific work of the authors Marcin Pietrzykowski and Wojciech Krzaklewski [28], the characteristics of the reclamation activities and their implementation in the mining industries of Poland are given. The research is aimed at the restoration of lands after mining operations in the direction of reforestation. A classification of post-mining areas in Poland was compiled based on an assessment of the complexity of biological reclamation [28].

In southern Poland, in Radziąków, an example of the transformation of abandoned areas into semi-natural areas after the mining industry is the development of the Silesian Botanical Garden [29].

Polish scientists are actively researching and promoting the concept of revitalizing areas negatively impacted by mining activities by integrating them into the tourism sector. Thus, Rurek et al. [30] study the potential of thematic mining settlements as a center for attracting tourism to regions previously involved in underground brown coal mining in northern Poland. Rostański [31] presents a successful experience of transforming a zinc production waste dump in Ruda Śląska (southern Poland) into a recreational area within the international LUMAT project, demonstrating the possibilities of ecological and social rehabilitation of industrial landscapes. Solarski and Krzysztofik [32] analyze the possibilities of urban landscape naturalization, considering examples of the spatial development of the city of Bytom (southern Poland), which experienced a period of intensive mining activities, emphasizing the role of natural elements in creating a favorable urban environment. Taken together, these studies demonstrate the prospects for using recreational and tourism strategies to restore and improve the attractiveness of degraded areas affected by mining.

In the work of the authors Hu Z., Liu S. and Gong Y., the quality of soil and growth of corn on restored lands after mining operations were assessed [33].

In Quebec (Canada), positive experience has been accumulated in the rehabilitation of tailings of ore processing plants, based on the use of reforestation technology. This method involves planting tree species in combination with the introduction of organic fertilizers, which helps improve the physical and chemical properties of the substrate and create favorable conditions for the growth and development of vegetation [34].

The scientific work analyzes the world experience of land reclamation, degraded due to mining activities and technogenic processes. Particular attention is paid to the study of the practices of biological land reclamation used in Ukraine to restore territories disturbed by mining enterprises. Based on the analysis, promising areas of land reclamation on a global scale are determined [35].

The authors of [36] note that the restoration of disturbed lands is an environmental component of one of the SDGs (goal 15). An example of the implementation of the industrial territory revitalization strategy is the RWE project in Germany, which provides for the placement of photovoltaic stations and energy storage systems on the sites of former brown coal mines [37,38].

Thus, there are many studies on land restoration, but a comprehensive approach with an environmental assessment and a selection of measures for the most complicated climatic conditions was carried out in studies for the first time for the complex industrial Karaganda region.

3. Overview of the Study Area

Karaganda region is a major industrial center of Kazakhstan. A significant number of industrial enterprises are located in this territory. Most of the deposits are concentrated mainly in Central Kazakhstan (Karaganda coal basin, Shubarkol deposit, Turgay brown coal basin) and the northeastern region (Ekibastuz, Maikubin coal basins, Karazhyra deposit). According to the Bureau of National Statistics of the Republic of Kazakhstan, 112.7 million tons of coal were mined in Kazakhstan in 2023, which is 1.1% less than in 2022 (113,707.3 million tons). Of this, about 107.7 million tons were hard coal and 4.9 million tons were brown coal. The maximum export volumes over the past 10 years (more than 32 million tons annually) were observed in 2021–2022 [39].

The relief of the study area, which is unique and heterogeneous geomorphologically, has a strongly elevated natural side. The small hills were formed in the process of continental long-term development, lasting from the middle of the Paleozoic to the present day, due to the intensive destruction and denudation of Precambrian, Paleozoic and later tectonic formations. Denudation processes turned the mountains into lowlands, into a vast ancient peneplain with island mountain ranges composed of the most destruction-resistant rocks. The Cenozoic–Mesozoic peneplain experienced weak repeated epeirogenetic movements. The processes of peneplainization and, partly, neotectonic movements caused the emergence and revival of wide leveled territories with low mountain ranges and small hills. Various denudation forms of small hills differ in the nature of the rocks and their occurrence.

The base of the foundations and the active zone of the compressible soil layer are made up of loose sandy–clayey sedimentary rock containing 10–30% (by weight) of clay particles, i.e., loam. Loam is a clay soil that contains from 10 to 30 percent of clay. This soil is quite plastic; when rubbing it between your fingers, you cannot feel individual grains of sand. A ball rolled from loam is crushed into a cake, along the edges of which cracks are formed. The porosity of loam is higher than that of sandy loam and ranges from 0.5 to 1. Loam can contain more water and is more susceptible to heaving than sandy loam. Dry loam with a porosity of 0.5 has a bearing capacity of 3 kg/cm², with a porosity of 0.7–2.5 kg/cm².

The climate is sharply continental and extremely dry. The average annual wind speed is 5 m/s. The highest average monthly wind speeds are in March (6.8 m/s), slightly lower in February and December (6.5 and 6.1 m/s). The minimum average monthly wind speeds are observed in August (4.3 m/s) (

Table 1. Frequency of different wind directions, %.

Direction	January	February	March	April	May	June	July	August	September	October	November	December	Year
N	5	8	7	9	12	16	19	17	13	7	5	5	10
NE	9	11	15	15	14	17	16	16	12	9	6	7	12
E	10	13	16	17	12	14	12	13	11	11	11	11	13
SE	17	15	13	12	10	10	9	9	10	11	16	17	12
S	24	23	16	13	13	11	9	9	13	16	20	22	16
SW	27	22	18	15	16	12	10	10	16	24	26	27	19
W	7	8	11	11	14	12	13	15	15	16	12	9	12
NW	1	2	4	7	9	10	13	11	10	5	3	2	6
Calm	11	10	9	8	9	9	9	11	11	9	7	11	10

, Figure 2).

The maximum absolute minimum air temperature was −42.9 °C in December 1938. The maximum average maximum was 27.3 °C in July, the minimum was minus 18.2 °C (

Table 2. Air temperature [40].

Month	Absolute Minimum	Average Minimum	Average	Average Maximum	Absolute Maximum, Speed (Year)
January	−41.7 (1969)	−17.8	−13.5	−9.0	6.2 (1940)
February	−41.0 (1951)	−18.2	−13.5	−8.4	6.0 (2007)
March	−34.7 (1971)	−11.9	−7.5	−2.7	22.1 (1944)
April	−24.0 (1963)	0.2	5.6	11.9	30.6 (1972)
May	−9.5 (1969)	6.6	13.0	19.8	35.6 (1974)
June	−2.3 (1949)	12.1	18.8	25.6	39.1 (1988)
July	3.2 (1936)	14.6	20.8	27.3	39.6 (2005)
August	−0.8 (1947)	11.9	18.2	24.9	40.2 (2002)
September	−7.4 (1969)	6.1	12.3	19.2	37.4 (1998)
October	−19.3 (1987)	−0.8	3.8	9.7	27.6 (1970)
November	−38.0 (1987)	−9.2	−5.4	−0.8	18.9 (1984)
December	−42.9 (1938)	−14.7	−10.6	−6.3	11.5 (1989)
year	−42.9 (1938)	−1.7	3.6	9.3	40.2 (2002)

).

Geological characteristics of the area

The geological structure of the site includes carbon, Jurassic, Neogene and Quaternary deposits. Carbon deposits are represented by the lower part of the Nadkaraganda suite and the Karaganda suite.

Relief is a hilly plain. The hilly relief is due to the development of Jurassic rocks, and the dissection of the relief into small ridges is due in part to the lithological features of the rocks. Karaganda Saransk ridge, to which the site is confined, has a steep northwestern slope and a gentle southeastern slope. Absolute surface marks are within 500–575 m. In the area of the planned works, the marks fluctuate from 496 to 560 m, which is caused by man-made formations.

There are no agricultural lands, industrial buildings and structures or natural bodies of water within the mining allotment.

The surveyed area belongs to the subzone of dark chestnut soils. In the surveyed area, dark chestnut medium-thick soils, dark chestnut incompletely developed and poorly developed soils are widespread. In the lower elements of the relief, soils of the semi-hydromorphic series have formed as follows: small and medium chestnut solonetz.

Hydrogeological characteristics of the area.

The aquifer complex of the Lower Jurassic terrigenous deposits of the Saransk and Dubovskaya suites (I1) is represented by loose conglomerates and sandstones, with interlayers and thin beds of brown coal and low-permeability argillites and siltstones, occurring directly on the eroded surface of the coal deposits. Jurassic deposits are widespread in the eastern part of the site. The thickness of the deposits reaches 44 m. The depth of water occurrence varies from 2.6 to 40 m. The water content of these deposits is generally weak, the filtration coefficients fluctuate within 0.1–1.84 m/day, the flow rates in the wells varied from 0.16 to 3.88 L/s with a decrease in the water level of 3.6–23.4 m and specific flow rates of 0.026–0.49 L/s/m. The waters are predominantly fresh, less often slightly salty with a mineralization of 0.2–1.5 g/L, hydro carbonate − sodium sulfate.

The projected open pits are located in the zone of the long-term exploitation of mines, during the development of which a significant regional depression funnel was formed. In recent years, this depression has been maintained by drainage from the mine workings.

Thus, the projected sections are located in a drained zone and therefore no water flows are expected in them due to groundwater.

Description of the research object.

The mining and processing enterprise considered in the article specializes in the extraction and sale of coal. Initially, three separate quarries were developed along the K10 seam (quarry No. 1, 2 and 3), and then two separate quarries along the K12 seam.

The mining and geological conditions of the occurrence predetermined the transport system of development with the removal of overburden rocks to an external dump in the initial period and subsequent internal dumping in the developed space. Coal is removed to an intermediate coal storage facility.

The enterprise has on its balance sheet and operates the following objects: external waste dump I and external waste dump II. At the initial stage, it is planned to temporarily store the overburden rocks in external waste dump II. The overburden rocks will be used for reclamation works, storing them in the internal waste dump of the worked-out quarries. Waste dump I is located on the site of future quarry excavations No. 3, 4 and 5 and will be used for reclamation of the worked-out quarries.

For mining and stripping operations, it is envisaged to use a single-bucket excavator of the reverse shovel type in combination with a bulldozer.

The conditions of the quarry location and development dictate the need to use transport that is flexible, mobile, maneuverable in operation, capable of working on temporary approaches with limited lengths and providing the highest possible productivity of mining equipment. Automobile transport fully meets the above list of the conditions under consideration.

The development system is transport-based with the removal of overburden rocks to an external dump in the initial period and subsequent internal dumping into the mined-out space. Large-size, high-traffic vehicles will be used for transportation of overburden rocks.

Opening of quarry fields is carried out by mobile trenches and automobile sliding semi-permanent ramps. The routes of automobile roads along the horizons are two-way. The slope of automobile roads is taken to be 0.08.

The development of mining and overburden benches is provided for by horizontal layers with a height equal to the optimal excavator digging depth −5.0 m, without the use of drilling and blasting operations. Preparation of new horizons is carried out as the lower mining bench is developed.

The overburden benches will be mined using reverse shovel-type excavators with a bucket capacity of 1.5 and 2.5 m³.

The height of the overburden bench will be 5 m, width of the entry 10 m. When the mining is brought to the final contour, the benches will be doubled and built up. In a stationary position, the height of the working side bench will be 10–15 m.

There are two waste dumps on the industrial site that were taken over from the previous owners. Waste dump I has accumulated 4000 thousand m³, in rock dump II—290 thousand m³ of overburden rocks.

The nearest residential area, represented by a private sector residential area, is located 900–1000 m to the west and northwest of the industrial site.

There are no sanitary and preventive institutions, recreation areas, medical institutions or objects protected by law (architectural monuments, etc.) in the area of the industrial site of the enterprise in question. The production volumes are given in

Table 3. Approximate calendar schedule of works. Volumes of extraction and overburden.

Name	Unit Change	Years of Work
		1st Year	2nd Year	3rd Year	4th Year	5th Year
Coal mining	Thousand tons	180.0	180.0	240.0	240.0	221.0
Volume of overburden	Thousand m3	2160.0	2160.0	2820.0	2820.0	2604.0

.

External rock dumps

Rock dump No. 1 will be used for the reclamation of quarries No. 3, 4 and 5. After the reclamation of the quarries, the area of external dump No. 1 will be leveled and planned. Since the external dump exists and overburden rock has accumulated on it, the territory of external dump No. 1 after the completion of all reclamation works will be a curved surface in the form of a hill with an area of 27 hectares height up to 5 m. Overburden rocks will be removed to external dump No. 2 during the initial development of quarry No. 2, and during the development of quarry No. 3. Overburden rocks from external dump No. 2 will be used to backfill part of quarry No. 2 and part of quarry No. 5. After that, external dump No. 2 will be reclaimed by leveling the slopes and grading the surface, and will be a curved surface in the form of a hill with an area of 19 hectares height up to 5 m.

The strip mine field is opened by a motorized coal–rock mobile trench of external foundation and motorized sliding semi-stationary ramps. They are intended for the removal of overburden to an external dump and for the transportation of coal to the coal storage area. The main dimensions of the elements of strip mine workings, ensuring safety during their operation, are given in

Table 4. Elements of the exit trench and sliding ramp.

Name	Production
	Exit Trench	Sliding Ramp
Maximum bench height, m	10.0	10.0
Width, m	20.0	16.4

.

The mining and geological conditions of coal occurrence predetermined the development of the transport system with the removal of overburden rocks to an external dump in the initial period and subsequent internal dumping in the developed space. Coal is removed to an intermediate coal storage facility.

The project provides for the development of overburden and mining benches according to a dependent technological scheme, consisting of the sequence of bench development from top to bottom along the length of the working side front. In this case, the development of the underlying bench is carried out after the overlying one. The minimum width of the working platforms includes the width of the excavator entry, the width of the face road, the berm (a horizontal platform on the slopes to give them stability) safety and ensures the safety of the mining and transport equipment: placement of excavators and access of dump trucks.

The general angle of the working side is generally 32–350.

The choice of types and parameters of mining equipment for extraction and overburden mining depends on the mining and geological conditions of the open-pit development, the planned rate of development of reserves, the physical and mechanical properties of rocks and the productivity of mining and transport equipment.

Considering the mining, geological and technological features of the development of industrial reserves, the project provides for external and internal waste dumping. In the first year of operation of open-pit mining sites, waste dumping is planned to be carried out on the area of the external waste dump.

The purpose and necessity of reclamation of lands disturbed by production activities of the mine

The most effective measure to reduce the negative impact of open-pit mining on the environment is timely reclamation of disturbed lands, which ensures not only the creation of optimal landscapes with the appropriate organization of the territory, flora and fauna, but also contributes to the reliable protection of the air basin and water resources. At the same time, technical reclamation is considered an integral part of the mining production process, and the quality and organization of reclamation work, as one of the indicators of production culture.

According to State standard 17.5.1.01-83 [41], the following directions of reclamation are possible: agricultural, with the aim of creating agricultural land on disturbed lands:

-

Forestry—for the purpose of creating forest plantations of various types;

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Fisheries—with the aim of creating fish-breeding reservoirs in depressions of man-made relief;

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Water management—with the aim of creating man-made relief in depressions;

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Reservoirs for various purposes;

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Recreational—with the aim of creating recreational facilities on disturbed lands;

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Sanitary and hygienic—for the purpose of biological or technical conservation of disturbed lands that have a negative impact on the environment, the reclamation of which for use in the national economy is economically ineffective or impractical due to the relative short-term existence and subsequent disposal of such objects;

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Construction—with the aim of bringing disturbed lands into a condition suitable for industrial and civil construction.

The choice of the direction of land reclamation is carried out considering the following factors:

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Natural conditions of the area (climate, soils, geological, hydrogeological and hydrological conditions, vegetation, relief, determining geosystems or landscape complexes);

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Agrochemical and agrophysical properties of rocks and their mixtures in waste heaps;

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Economic, socio-economic and sanitary–hygienic conditions in the area where disturbed lands are located;

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The lifespan of reclamation lands and the possibility of their repeated violations;

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Technologies for the production of a complex of mining and reclamation works;

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Environmental protection requirements;

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Plans for the prospective development of the territory of the mining area;

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The state of previously disturbed lands, i.e., the state of man-made landscapes of the quarry–dump type, the degree and intensity of their spontaneous combustion.

An analysis of the factors influencing the choice of the direction of reclamation of lands disturbed by mining operations showed that the sanitary and hygienic direction of reclamation with subsequent biological stages of reclamation, which fully meets the natural, social conditions and the purpose of reclamation, is acceptable.

Reclamation must be carried out in two stages: technical and then biological.

The study revealed that there is no soil suitable for removal and further use for biological reclamation on the site, since the facility is located on industrial lands.

In this regard, the biological stage of reclamation is extremely difficult. However, it must be carried out. To do this, it is necessary to bring fertile soil, or find a substrate that can be used as a substitute for natural soil.

The area of reclamation to be studied will be 77.35 ha. At the biological stage of reclamation, herbs such as wheatgrass, motherwort and coltsfoot will be sown at a rate of 3 g of seeds per 1 m², followed by watering.

Technical Methods

To analyze the characteristics of the disturbed land area, materials from engineering–geological and engineering–hydrogeological surveys from previous years were used, and additional field and laboratory studies were carried out within the framework of this project.

In accordance with State standard 17.5.1.01.83 [41], the following directions of reclamation are possible:

-

Agricultural—with the aim of creating agricultural lands on disturbed lands;

-

Forestry—for the purpose of creating forest plantations of various types;

-

Fisheries—with the aim of creating fish-farming reservoirs in depressions of man-made relief;

-

Water management—with the aim of creating reservoirs for various purposes in depressions of man-made relief;

-

Recreational—with the aim of creating recreational facilities on disturbed lands;

-

Sanitary and hygienic—for the purpose of biological or technical conservation of disturbed lands that have a negative impact on the environment, the reclamation of which for use in the national economy is economically ineffective;

-

Construction—with the aim of bringing disturbed lands into a condition suitable for industrial and civil construction.

The choice of the direction of land reclamation is carried out considering the following factors:

-

Natural conditions of the region (climate, soils, geological and hydrogeological conditions, vegetation, relief, determining geosystems or landscape complexes), agrochemical and agrophysical properties of soils;

-

Economic, socioe-conomic and sanitary–hygienic conditions in the area where disturbed lands are located;

-

The lifespan of reclamation lands and the possibility of their repeated violations;

-

Technologies for the operation of hydraulic structures bordering the site and reclamation works;

-

Environmental protection requirements;

-

Plans for the long-term development of the territory of the area where reclaimed lands are located.

In economic terms, the area where the deposit is located is industrial, with coal, woodworking and food industry enterprises operating.

According to State standard 17.5.1.02-85 “Lands. Classification of disturbed lands for reclamation” [42], which is in force in the territory of the Republic of Kazakhstan, shallow quarry excavations developed in one bench can be used to create sodded areas for nature conservation purposes.

The technical stage of reclamation involves the preparation of land for subsequent targeted use [43] and includes the performance of the following types of work:

-

Construction of a protective shaft;

-

Backfilling of overburden rocks into mined-out spaces;

-

Leveling the slopes of quarries and waste dumps to a slope of 10°;

-

Compaction by cam rollers on pneumatic wheels;

-

Planning and rolling of the surface.

After completion of the mineral extraction work, the buildings and capital production facilities are to be preserved. Their subsequent use for economic purposes is possible.

Quarry No. 1

The quarry is developed in the following manner.

Initially, the overburden from quarry No. 1 is used to fill protective banks around the entire perimeter. The remaining volume of overburden is taken to a temporary external dump from the northern slope of quarry No. 1 (to the idle side). After quarry No. 1 is fully mined, the overburden from the temporary external dump and protective banks will be filled back, then the slopes will be leveled to a 10° slope, compacted, planned and rolled. Due to the fact that the volume of overburden removed (due to the extracted coal) will be less than the volume of the mined space, the quarry surface will be slightly deepened.

Quarry No. 2

At the initial stage of quarry No. 2 development, overburden will be stored in external dump No. 2; then, as the quarry is developed, the mined-out space will be filled with overburden without transporting overburden to the surface—internal waste heap formation, until the quarry is fully developed. After the quarry is developed, the missing overburden in the amount of 306 thousand m3 will be taken from external dump No. 2 and from external rock dump No. 1 from the location of quarry No. 3. After this, the slopes will be leveled to a slope of 10°, compacted, planned and rolled.

Quarry No. 3

Initially, protective banks will be made along the perimeter of external dump No. 1, which is not included in the territory. During development, overburden rocks from quarry No. 3 will be transported to external dump No. 2. After complete development of quarry No. 3, the overburden located on external dump No. 1 in the area of quarry No. 4 and quarry No. 5 will be moved to the mined-out space, as well as part of the overburden rocks formed at the initial stage of development of quarry No. 4. After this, the slopes will be leveled to a slope of 10°, compacted, planned and rolled.

Quarry No. 4

At the initial stage of quarry development №2, the overburden will be used for the reclamation of quarry No. 3; then, as the quarry is developed, the mined-out space will be filled with overburden without transporting the overburden to the surface—internal dumping, until the quarry is completely developed. After the quarry is developed, the missing overburden from quarry No. 5 during its development, as well as part of the overburden from external dump No. 1, will also be moved to the mined-out space. After this, the slopes will be leveled to a slope of 10°, compacted, planned and rolled on the surface.

Quarry No. 5

Initially, protective banks will be made along the perimeter of external dump No. 1, which is not included in the territory. During development, overburden rocks from quarry No. 5 will be used for the reclamation of quarry No. 4. The remaining formed overburden will be moved to external rock dump No. 2. After complete development of quarry No. 5, the overburden located on external dump No. 1 and external dump No. 2 will be moved to the mined-out space. After this, the slopes will be leveled to a slope of 10°, compacted, planned and rolled.

External waste dump No. 1

Rock dump No. 1 will be used for the reclamation of quarries No. 3, 4 and 5. After the reclamation of the quarries, the area of external dump No. 1 will be used for leveling the slopes to a slope of 10°, compaction, planning and rolling of the surface. Since the external dump exists and overburden rocks have accumulated on it, which will not be fully used, the territory of external dump No. 1 after the completion of all reclamation work will be a curved surface in the form of a hill with an area of 27 hectares height up to 5 m.

External waste dump No. 2

External dump No. 2 will be used to remove overburden rocks from the initial development of quarry No. 2, from the development of quarry No. 3 and part of the overburden rocks from quarry No. 5. Overburden rocks from external dump No. 2 will be used to backfill part of quarry No. 2 and part of quarry No. 5. After that, external dump No. 2 will be reclaimed by leveling the slopes to a 10° slope, compacting, planning and rolling the surface and will be a curved surface in the form of a hill with an area of 19 hectares height up to 5 m.

The composition of the grass mixture for biological reclamation is formed on the principles of ecological adaptation, considering such factors as winter hardiness, drought resistance, salt tolerance and resistance to increased or decreased environmental reaction. The rates of application of fertilizers and sowing of seeds of perennial grasses are given in

Table 5. Application of fertilizers and sowing of perennial grass seeds on the sides of a quarry.

Name of Works	Application and Seeding Rates
Hydroseeding of perennial grasses together with the application of fertilizers:
- Carbamide (urea);	60 kg/ha
- Double granulated superphosphate;	60 kg/ha
- Potassium sulfate;	60 kg/ha
- Water;	45 m3/ha
- Yellow sweet clover;	24 kg/ha
- Yellow alfalfa;	14 kg/ha
- Awnless brome;	30 kg/ha
- Crested wheatgrass;	30 kg/ha
- Wood sawdust.	22 m3/ha

.

4. Results

All areas disturbed during the work process are subject to reclamation.

In accordance with the legislation of the Republic of Kazakhstan, the reclamation of disturbed lands, increasing their fertility and using and preserving the fertile soil layer are environmental protection measures.

The technical stage of reclamation involves the following work:

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Cutting off the quarry side to organize a technological ramp;

-

Leveling and planning of the southeastern side of the quarry up to 18 degrees using the “top-down” method;

-

Leveling and planning of the southern, western and northern sides of the quarry;

-

Planning of the quarry bottom.

The quarry side cutting for the organization of the exit is planned from the western side at the junction of the existing dirt road. The cutting is carried out by a bulldozer using the “top-down” method. The organization of the exit is necessary for carrying out reclamation work and access to the pond after completion of reclamation.

The technological parameters are as follows:

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Length—85 m;

-

Width—10 m;

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Slope i = 0.010;

-

Elevation difference—538.2–529.5 mBS.

The design setting of the general angle of quarry wall recession at the end of mining is 450, which is an unsafe criterion after completion of mining operations. As part of the technical stage of reclamation, it is envisaged to flatten the walls to a slope of 18–220, which reduces the degree of erosion of the walls by accumulated waters, allows for the smooth integration of the disturbed area into the natural landscape and allows people and animals to independently get out of the quarry.

Monitoring work is carried out on the restored areas (Figure 3):

-

Development and transportation of overburden rocks to areas located along the worked-out sides of the quarry along the drained bottom of the quarry;

-

Development and transportation of overburden rocks to areas located along the worked-out sides of the quarry in the flood zone at the top of the quarry;

-

Development of clay rocks in a quarry to flatten the sides;

-

Flattening of overburden rocks on the sides in the drained part of the quarry using the “bottom-up” method;

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Flattening of overburden rocks on the sides in the flooded part of the quarry using the “top-down” method;

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Planning of quarry sides after completion of leveling;

-

Planning of the drained part of the quarry bottom.

Biological stage of reclamation

Work on the biological restoration of lands is carried out to fix the applied reclamation layer by the root system of plants on the surface of disturbed lands, as well as to create plant communities for landscaping purposes. Biological restoration is carried out with the purpose of creating a root-inhabited layer on the surface prepared during the technical stage.

To assess the rooting and early growth of plants, experiments were conducted using three types of soil substrates: a mixture of vermiculite and quartz sand; overburden from quarries and coal mines [44]. Also, studies were conducted between 1997 and 2005, which had combinations of coal dust substrate and coarse-grained material [45].

It is advisable to use biological substrates instead of the natural fertile soil layer. In addition to replacing the missing soil in the storage tanks, biomaterial promotes the formation of the soil layer due to the subsequent decomposition of natural fibers that make up the biomat (Figure 4,

Table 6. Laboratory test results.

Soil Type	Average Monthly Number of Sprouts, pcs/cm2 (Average Monthly Sprout Height, cm)
	January	February	March	April	May
Natural soil	8 (4)	15 (15)	17 (18.25)	17 (19.5)	17 (19.5)
Ash, slag	11 (4)	13 (19)	13 (17.5)	13 (18.25)	13 (18.25)
Rocky ground	7 (3.15)	12 (5.5)	12 (9.5)	11 (10)	9 (10)
Pulp	6 (6.25)	9 (7)	8 (10.25)	8 (10.75)	6 (10.75)

).

As a conclusion, it was established that biological plant materials can be used for reclamation on technogenic substrates. However, the set of plants should be adapted to the conditions of the region under study: strong wind, dry hot summer and high solar activity. The preliminary composition of the set of herbs, which should be varied depending on the local conditions, was as follows: red fescue, reed fescue, meadow bluegrass, wheatgrass and awnless brome grass.

In addition, for more effective reclamation, it is recommended to plant trees and shrubs around. Optimal conditions for ventilation and air purification in the sanitary protection zone are achieved by creating ventilation corridors, especially in the direction of prevailing winds, which is considered when developing the scheme for planting trees and shrubs.

The planting rate is 150–200 seedlings per hectare.

For the main species of shrubs, the following species are recommended: tamarix (comb), oleaster, ash and acacia, as well as elm, maple and hawthorn.

The accompanying species are almonds, currants, chingil and juzgun. Figure 5 shows a diagram of the planting of trees and shrubs.

For planting and facilitating the care of trees and shrubs, a wide-row planting scheme is recommended.

The range of trees and shrubs is formed as follows: main species (MS) and secondary species (SS). In the center of the row, an irrigation furrow is laid, which will collect atmospheric precipitation, and will also be used for irrigation if precipitation is insufficient. At a distance of 1.5 m on both sides of the trenches, MS is planted. The distance between plants is 5 m. SS is planted at a distance of 3 m from the MS row. MS and SS plants are planted in a checkerboard pattern. One irrigation furrow is laid on both sides of the row. The total width of the row is 10 m. The depth of the irrigation furrow is 30–50 cm, the width is 30–50 cm. The distance between the rows is 35 m. In total, 240 seedlings are planted per 1 ha. Of these, 120 are of the main species and 120 are of the accompanying species.

The irrigation furrow not only optimizes irrigation work, but also accumulates moisture after the snowmelt period and during precipitation during the warm period of the year.

If the grass mixture contains only loose-bunch grasses, the grass stand quickly thins out due to the low resistance of the roots. At the same time, rhizome plants with a well-developed fibrous root system increase the elasticity of the turf cover, and leguminous grasses with a powerful taproot system connect the upper soil horizons with the lower ones, and provide the greatest resistance to the mechanical impact of rainwater. In this case, the following advantages take place:

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Mixtures overwinter better, are stored longer and produce more stable harvests;

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Mixtures use nutrients better, since their roots cover more layers of soil, the roots of cereals spread shallower, while legumes penetrate deeper;

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Mixtures leave more roots in the soil, and therefore more organic matter, thereby improving the soil structure.

When including one or another type of grass in a grass mixture, the following biological characteristics are taken into account: winter hardiness, drought resistance, salt tolerance and resistance to increased or decreased environmental reaction [46].

Thus, in order to select the direction of land reclamation, an assessment of the territory of the studied deposit was carried out as follows:

-

Physical and geographical characteristics of the area of the deposit location were studied;

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The enterprise for the extraction of minerals was studied, and sources of land disturbance (quarry, dumps) were identified;

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Existing traditional methods of land reclamation were considered;

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Laboratory and field studies on land restoration in complicated natural and climatic conditions (on example in Karaganda region) were carried out.

5. Discussion

Territories disturbed by mining activities, without special reclamation measures, remain unsuitable for further use [47]. Land disturbance resulting from mining activities results in environmental impacts that extend far beyond the operating area [48,49].

At present, there are good technical solutions for the restoration of areas disturbed by mining activities in the field of physical, chemical, biological and combined restoration technologies [50,51].

The screening stage identifies potential direct, indirect and stimulating positive and negative impacts that may affect the social and economic aspects of life in the area affected by the project.

Direct impacts occurring in the socio-economic environment are impacts directly related to the operations of the project implementation in the territory of its implementation. They include changes in such social indicators as employment, level of well-being (income) and health status of the population.

Indirect (mediated) impacts are impacts that are not related to a specific project action, but show the effect of project implementation within broader boundaries (district, region and republic as a whole). These changes are related to indirect changes in both the social and economic spheres.

Stimulating effects are effects caused by changes in the social environment as a result of changes stimulated by the project in the economic sphere. These effects manifest themselves over a longer period of time than direct and indirect effects.

Land reclamation is one of the most effective and direct ways to improve the environmental situation in areas affected by mining activities [52,53]. Reclamation of areas disturbed by mining activities is a long-term and dynamic process that ultimately leads to the restoration of the ecosystem [54]. When reclaiming lands disturbed by mining operations, it is necessary to conduct continuous assessment and monitoring of the state of the restored areas [54,55,56,57,58].

Land reclamation will reduce the impact of disturbed lands on environmental components, such as the atmosphere, surface and groundwater, soils, flora and fauna, has a beneficial effect on human health and is aimed at eliminating environmental damage. In addition, the plant landscape improves the microclimate of the restored lands [59,60]. Vegetation restoration is a major factor in improving soil quality [61,62]. Tree planting leads to slow and steady ecosystem restoration, while shrub planting leads to early improvement. Vegetation types and cover effectively indicate ecosystem stability and biodiversity [45,63]. Reclamation in Kazakhstan is carried out on the basis of State standard 17.5.3.05-84 [64].

In turn, the restored lands will allow for the overall rehabilitation of industrial areas, the formation of pasture areas and/or the creation of areas for tourism and sports (equestrian sports, mountaineering) [65]. An assessment of the impact of different types of land use after reclamation (afforestation, haymaking, pasture use) on the complex of physical characteristics of the soil was carried out in a comparative aspect [66]. These nature restoration measures are a real indicator of the possibility of reducing the negative impact of enterprises extracting and processing minerals. In addition to the nature conservation effect, rehabilitation work has social significance in the form of restoring steppe massifs and creating recreational areas.

Given the difficult soil conditions, trees are not recommended for landscaping. The main life form for planting is shrubs. Under planting conditions, the main species for landscaping can reach a height typical for tree plantations in arid climates. The diagram recommends alternating taller and shorter shrubs. Taller plants are used as the main species, and shorter ones are used as the accompanying species. The climatic conditions of the area and landscapes must be taken into account [67,68].

The selection of plant species is an important factor in the restoration of lands disturbed by mining operations [69]. The correct selection of plant composition subsequently influences the quality and properties of soils [15].

The success of reclamation depends on factors such as the initial soil composition, climatic conditions of the area, hydrology and the choice of plant species for reclamation [70,71,72].

The best time to plant trees and shrubs is early spring. The start date of silvicultural work is determined by the meteorological features of the year: snow melting, warming and the possibility of soil cultivation. Planting is carried out in a short time within 10–12 days (before the beginning of plant vegetation and bud opening).

Authors should discuss the results and how they can be interpreted from the perspective of previous studies and of the working hypotheses. The findings and their implications should be discussed in the broadest context possible. Future research directions may also be highlighted.

6. Conclusions

This study comprehensively shows that the reclamation of disturbed lands will lead to the restoration of their fertility and other useful properties of the land and its timely involvement in economic circulation:

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Removal, preservation and use of the fertile soil layer during work involving land disturbance;

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Elimination of sources of adverse impact on the environment;

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Improving the sanitary and hygienic living conditions of the population;

-

Increasing the aesthetic value of the landscape.

In order to reduce the impact of the enterprise on the industrial site, it is proposed to sod (overgrow with turf grasses) the waste dumps of the enterprise. It is necessary to conduct constant monitoring in these areas.

The social and ecological consequences of reclamation consist of creating favorable conditions for human life and the functioning of ecological systems in the area of the location of disturbed lands during the extraction of minerals after their restoration and provides for the following results:

-

Environmental protection result—elimination of environmental damage caused by disturbed lands during the period of reclamation works, regardless of the direction of reclamation;

-

Nature-restoring result—creation of conditions in the area of placement of disturbed lands after their reclamation that best meet social and environmental requirements (sanitary and hygienic, aesthetic, recreational, etc.).

The main scientific conclusions and practical results of the research carried out are as follows:

-

As a result of the development of all the deposits under consideration, ecosystems change. The most significant change occurs as a result of the formation of quarries, waste rock dumps and enrichment waste.

-

Reclamation work will prevent the spread of negative impacts on the ecosystems of mining regions. Restoration work will return the lands to the category of “natural resources”.

-

For quarries for the extraction of mineral resources with waste rock, partial flooding and planting of perennial grasses and shrubs is recommended. For better protection and aesthetic appearance at the border of the sanitary protection zone, a positive effect will be achieved by planting trees.

-

The planted vegetation will have a positive effect as “green plant resources” of the territory.

For the studied object, the following algorithm is required for land restoration:

• Backfilling of rocks along the drained quarry bottom to reduce the volume of flooding;
• Backfilling of rocks in the flood zone in the upper part of the quarry (flattening);
• Leveling the sides with clay;
• Level the area around the quarry for the use of biomats and growing plants;
• Preparing the area for planting tree species;
• Maintaining the territories and monitoring the condition of the restored lands.

As a result, the benefits for the mining industry are as follows:

(1) After the closure of the enterprise:

-

Creation of reservoirs in exhausted quarries;

-

Use of soils from dumps for filling quarries, for road construction.

(2) Economic and social benefits:

-

No payments for the placement of dumps and waste in the environment;

-

Improving the quality of life of the population;

-

Return of land to agricultural circulation.

The Karaganda region is the most industrially complex territory and land restoration methods suitable for this region will be suitable for other territories of Kazakhstan, as well as similar climatic conditions and industrially saturated territories in the world. The research conducted in the article is aimed at restoring the mining industry’s disturbed lands. The results of the study can be included in state plans for the development of the Karaganda region and Kazakhstan as a whole.