GB/T 43935-2024Technical specification for monitoring and evaluation of land reclamation and ecological restoration in mines (English PDF)

3 Terms and definitions

Mine land reclamation and ecological restoration is defined as the activity that, for the geological environment damage, land destruction and ecosystem damage or degradation caused by the extraction of mineral resources, relies on human support and guidance together with natural restorative capacity and takes preventive and restorative measures so that the mine geological environment becomes safe and stable, the destroyed land is reclaimed for use and the ecosystem function is restored or improved; a note abbreviates it to reclamation and restoration.

A monitoring site is a fixed or temporary point set up for observation, testing or sampling. The monitoring area is the region formed together by the extraction area, the area affected by mining and the sample plots of the reference ecosystem. A reference ecosystem is an ecosystem that can serve as the target or benchmark of ecological restoration; a note states that in this document it means in particular the ecosystem before extraction, the undisturbed local ecosystem around the mine, or an ecosystem that can be predicted to be reached on the basis of the target values.

The four kinds of value used throughout the document are defined as follows. The reference value is the figure obtained by surveying and monitoring the reference ecosystem, or the figure explicitly laid down by an existing standard. The base value is the figure of the monitored object at the base period, obtained by survey before extraction begins; a note adds that it is also called the initial value or the present value. The monitoring value is the measured figure obtained at different points in time, as monitoring requires, over the whole process of extraction, reclamation and restoration. The target value is the binding or guiding figure fixed by the reclamation and restoration plan and by the planning and design.

Adaptive management is the method and process of gaining experience by monitoring and assessing the reclamation works, management measures and practical measures taken in the past and of correcting and improving them as the ecosystem changes.

4 Purpose and general requirements of monitoring and evaluation

4.1 During the extraction of mineral resources, monitoring and evaluation are carried out on geological environment damage and its treatment, on land destruction and reclamation, and on ecosystem damage or degradation and its restoration, so as to give a sound basis for the process supervision, the adaptive management and the acceptance of mine land reclamation and ecological restoration.

4.2.1 Problem oriented, focused on the essentials. Centred on geological environment damage and treatment, land destruction and reclamation, and ecosystem damage or degradation and restoration within the monitoring area, and having regard to the mineral extracted, the scale of construction, the mining method, the process and the timing, the key monitoring content, indicators, point positions and periods are to be set on a sound basis, so that each mine has its own plan.

4.2.2 Scientific and regular, throughout and complete. The acquisition of indicators is to meet the relevant national technical standards and specifications and the rules of the departments concerned. The layout of monitoring points is to take account together of the needs before, during and after extraction. Before extraction the geological environment background, the current state of the land resource and the ecosystem baseline are surveyed; during extraction the protective and preventive control measures, the current and intended destruction and the effect of reclamation are monitored; after extraction the management and maintenance are monitored.

4.2.3 Accurate and efficient, practical and workable. While meeting the required monitoring accuracy, economical and practical monitoring methods and means are to be chosen, advanced and reliable techniques being used where economic and technical conditions allow, so that accuracy and efficiency are raised. The indicators are to be sufficiently sensitive and measurable; indicators that change easily are to be monitored over a short period and stable indicators over a long period.

4.2.4 Qualitative and quantitative, authoritative and comparable. Monitoring and evaluation are to combine qualitative and quantitative methods, the evaluation method being sound and reasonable. The data are to be continuous and reliable, and full use is to be made of the long-term monitoring data and research results of the natural resource, forestry and grassland, water, agriculture and rural affairs and ecology and environment departments and of research institutes and universities.

6 Objects and content of monitoring

6.1 Monitoring before extraction chiefly obtains the base values and reference values of the mine geological environment background, of the current state of the land resource and of the ecosystem baseline. It monitors the groundwater and soil environmental background of the mine and the surrounding area before extraction; establishes the current land use, the situation of basic farmland and the quality and productivity of each land use type within the monitoring area; establishes the area of the surface water environment and the condition of terrestrial vegetation within the area; and, following the main functional zoning and the natural features of the mining area and working from the land use parcels, sets sample plots and quadrats of forest, grassland and wetland ecosystems on grounds of typicality and representativeness so as to build the reference ecosystem and obtain the reference values. The monitoring content and indicators before extraction are given in Table A.1.

6.2 Monitoring during extraction chiefly covers protective and preventive control measures, the current and intended destruction, and the effect of reclamation. It monitors how the protective and preventive control measures of the mine are carried out, including the measures themselves and their effect; the goaf subsidence, unstable slopes, groundwater environmental damage and soil environmental damage caused by extraction; the type, area and degree of land destroyed by excavation, subsidence, occupation and pollution and the destruction of basic farmland; the destruction of ecological land, the surface water environment and the water resource environment of coal mining subsidence areas; the recovery and treatment of geological environment already damaged, the reclamation and use of land already destroyed and the restoration of ecosystems already damaged or degraded; and the change of the geological environment, land resources and ecosystems that are to be destroyed. The monitoring content and indicators during extraction are given in Table A.2.

6.3 Monitoring after extraction chiefly covers the management and maintenance of the areas already reclaimed: the maintenance of infrastructure, the tending of land quality and vegetation and the maintenance of ecosystem function. For the reclaimed open pit, spoil dump, gangue hill, tailings reservoir, heap leaching site and subsidence area, the stability of the geological environment, the effect of the control of potential pollution, the effect of ecosystem restoration and the latent risks are monitored in particular; and the water bodies, water sources, permanent basic farmland, protected areas and basic grassland affected by extraction are likewise monitored in particular. The monitoring period after extraction is recommended to be five to ten years. The monitoring content and indicators after extraction are given in Table A.3.

7 Layout of monitoring points and monitoring methods

7.1 The monitoring area and the layout of points are to cover the extraction area, the affected area and the area of the reference ecosystem. Points are preferably laid out by combining points, lines and areas, and full use is to be made of the existing monitoring networks of the several departments and research institutes so that a monitoring network for mine reclamation is formed. Automatic and manual monitoring are to be combined, and remote sensing monitoring, fixed sample plots, quadrats and belt transects, fixed automatic monitoring of the soil and water environment, test analysis and public interview may all be used for dynamic follow-up monitoring of the reclamation work and its effect throughout. The monitoring period and frequency of each indicator are to be settled having regard to the natural geographic conditions, the mineral extracted, the mining method, the destruction, the reclamation measures and targets, the monitored object and the management needs. Points are to be concentrated on the open pit, spoil dump, gangue hill, tailings reservoir, heap leaching site, subsided land, in-situ leaching site and the discharge outlets of ore washing and dressing water, and points are to be set on the water bodies, water sources, permanent basic farmland, protected areas and basic grassland that extraction may affect. The layout, period and frequency are to be adjusted from the results so that data collection stays accurate, timely and complete; where natural conditions are poor, reclamation difficult or potential pollution risk high, the period is to be lengthened and the frequency raised. Monitoring of the protective measures and their effect uses field survey, remote sensing survey and public interview, water and soil conservation monitoring following GB/T 51240.

7.2 For the mine geological environment, groundwater monitoring points are laid out with the mine as the unit and cover water level, water quality and water volume; in the recharge, runoff and discharge areas that mining is expected to affect, points for water level, water quality and water temperature are laid out along or across the groundwater flow direction, naturally emerging springs within the mine being preferred, purpose-built monitoring wells being the main means and production or domestic wells a supplement. Soil environmental monitoring points are likewise laid out with the mine as the unit, with at least one point in every micro-relief unit and every land use type within the area; background points are laid out from high ground to low in and around the area that mining is expected to affect, with particular attention to the soil around heap leaching sites and tailings reservoirs. For goaf subsidence, the extent of the goaf is settled from the mining plan, the surface and underground correspondence drawing and the destruction prediction, and reference points, working base points and monitoring points are laid out to form a network for the subsidence area and the ground fissures; where room and pillar mining is used underground, cross-shaped monitoring lines are preferred, and where mechanized longwall mining is used, lines in the shape of the characters feng, jing or tian are preferred; the lines are to be longer than the range of mining influence and at least one end is to reach stable ground; monitoring may stop once subsidence is stable.

7.2 (continued) Monitoring points are also laid out for the reshaped landforms of the open-pit workings, the solid waste stockyard and the spoil dump and for the ground beyond the final limit that may deform, together with the collapses, dangerous rock masses and unstable slopes affected; points for surface and subsurface deformation are concentrated on the bulging zone of the slope face and the tension zone at the crest, and points for groundwater level on the resisting zone at the toe; shared monitoring data of the departments concerned is used for the monitoring of geological stability and of triggering factors such as rainfall. In the subsidence area, the groundwater drawdown cone and the groundwater catchment of waste water and waste liquid outlets, a network for groundwater environmental damage is laid out from the hydrogeological data: hydrogeological boreholes, shallow wells and core sampling points monitor the change of aquifer thickness; wells for water level, volume and temperature monitor the change of the phreatic water that sustains the ecological environment, of the target extraction layer and of the drained layer; and groundwater samples or field tests monitor the change of water quality. Points for soil environmental damage are laid out chiefly in the areas occupied, damaged and polluted by solid waste, tailings reservoirs and open-pit workings and in the areas polluted by ore washing and dressing water; sampling points are laid out in plan and in depth according to the diffusion of the pollutants, plan points being placed where the soil type is clearly expressed and profile points where the profile is complete, the layers clear and there is no intrusive body; mixed samples are collected, small monitoring areas using the diagonal and plum-blossom layouts, medium areas the chessboard layout and large areas the snake layout. After reclamation works, points for groundwater environmental recovery are laid out in the drawdown cone and the polluted zone, preferably chosen from the damage monitoring points where the dynamic features are clearly expressed and the wellhead protection is sound, the borehole is not silted and the water-lifting equipment works; and points for soil environmental recovery are laid out by decision units built from the reclamation direction, the reclamation time and the micro-relief unit of bench and platform, with at least one mixed sampling point per unit and closer spacing where soil pollution is heavier. The layout, monitoring grade, point density, frequency, sampling method and monitoring method for the geological environment background and damage follow DZ/T 0287 and DZ/T 0388.

7.3 For land resources, the monitoring of current land use builds on the latest national land change survey results of the monitoring period, from which the land use type, area and tenure within the area are extracted and the distribution and area of basic farmland established. The survey of land already destroyed divides destruction units by damage type and monitors the type, degree, area and extent of the destroyed land: open-pit workings and borrow areas take a single excavated site as unit; subsided land is divided by the extent of goaf subsidence together with administrative boundaries, land use type and ponding; land occupied by spoil dumps takes a single occupied site or a single occupied line as unit; and polluted land is divided by the extent of pollution. The destruction of roads, water facilities, shelter belts and other infrastructure is likewise monitored. Land that is to be destroyed is monitored on survey units divided by the timing of extraction, the mode of destruction, the destruction prediction, the land use type, the soil type and village boundaries. The use type, extent, area, mode of use, cover features and level of use of land already reclaimed are monitored by remote sensing interpretation, ground survey and public interview. Decision monitoring units are then divided by the land use type after reclamation, the reclamation time, the micro-relief of platform or slope and the reclamation measures, and points laid out by unit so that the quality of the reclaimed soil is monitored dynamically. Land resource monitoring is preferably carried out once a year, and the soil quality of reclaimed arable land once a year, the soil quality of other reclaimed land once every three years; monitoring of reclaimed forest, reclaimed grassland and restored wetland is to fall in the period of peak grassland biomass, preferably July to August in the north and June to October in the south. Land use types follow GB/T 21010 and the guideline on the classification of land and sea use for territorial survey, planning and use control; the current land use survey follows TD/T 1055, dynamic remote sensing monitoring TD/T 1010, arable land quality monitoring NY/T 1119, and the survey and monitoring of land already destroyed and to be destroyed TD/T 1049. Soil sampling points are to cover every land use type in the monitoring area, mixed samples being collected by the diagonal and plum-blossom layouts, the number of samples per type meeting GB/T 36393; soil pollution sampling follows GB/T 42489, the environmental quality monitoring of reclaimed soil HJ/T 166, and the soil quality monitoring of reclaimed forest and grassland GB/T 32740.

7.4 For the ecosystem, monitoring sections are set on rivers and monitoring verticals on lakes, ponds and reservoirs. An entry section is set before the river enters the area affected by mining and an exit section where it leaves; points are set downstream of areas or points of potential pollution risk and of discharge areas or outlets, where the waste water and the surface water are essentially mixed. In the different water areas of lakes and reservoirs within the monitoring area, such as the inflow area, the outflow area, the deep water area, the shallow water area, the lake centre and the shore zone, verticals are set by water body class; where there is no clear functional distinction, verticals may be set evenly by a grid; and in important lakes and reservoirs heavily affected by pollutants, control sections are to be set on the main migration paths of the pollutants. The layout and sampling for surface water environmental quality follow HJ 91.2. Vegetation tending monitoring covers the closure, supplementary planting, tending, renewal, pruning, fire prevention and control of pests, disease and rodents of reclaimed forest land, following GB/T 18337.3; reclaimed grassland takes grazing exclusion and enclosure, no-till resowing, loosening and fertilizing and rodent and insect control so that vegetation recovers, following NY/T 1342. In the monitoring of ecosystem function maintenance, forest ecological status follows GB/T 30363 and HJ 1167, grassland ecological status NY/T 2998 and HJ 1168, wetland ecological status HJ 1169, and the ecological status of desert systems such as sandy land, bare soil and bare rock and gravel land HJ 1170; the layout of quadrats, sample plots and belt transects is to take account together of the reclamation direction, the reclamation time, the relief and the vegetation type.

8 Evaluation of reclamation and restoration

8.1 On the basis of the base value, the reference value, the monitoring value and the target value, and using single-factor comparison, trend evaluation, expert evaluation and public participation, and with reference to the international five-star rating system and to visualization methods such as the ecological recovery wheel, the geological environment damage and treatment, the land destruction and reclamation and the ecosystem damage or degradation and restoration are evaluated at the instant of monitoring. For binding indicators such as surface water environmental quality, fishery water quality, the pollution risk control of agricultural land soil, the pollution risk control of construction land soil, farmland irrigation water quality, the land reclamation rate and the amount of soil erosion, evaluation uses the single-factor index, the sample exceedance rate and the treatment rate; where the mean single-factor pollution index of the samples is significantly greater than 1, or the sample exceedance rate is greater than 10 %, the result is rated as not qualified. For expected indicators such as canopy density or cover, ecosystem quality, biodiversity and soil fertility, trend evaluation, the five-star system and the ecological recovery wheel may be used for quantitative and qualitative evaluation so that the direction of change is judged.

8.2 On the basis of the monitoring values, the geological stability of the mine is evaluated so that the number, scale and area of geological environment hazards are obtained; the area and degree of land affected by surface subsidence and surface excavation are analysed; and the damage to the surface water and groundwater environment is analysed. The evaluation of the degree of development and the danger of geological hazards follows GB/T 40112 and groundwater quality follows GB/T 14848. The type and degree of harm of aquifer damage are evaluated following GB/T 42362. From the monitoring values of recovery and treatment, the area treated and the number of hazards removed are obtained, the recovery and treatment rate computed and the rate of compliance of groundwater and surface water at the monitoring points computed; the evaluation of treatment effect follows DZ/T 0287, and the statistical table for the evaluation of geological environment damage and treatment is Table B.1.

8.3 The protective measures and the preventive control of mine extraction and their effect are evaluated qualitatively. Water and soil conservation is evaluated following GB/T 51240. Land destroyed by excavation, occupation, use, pollution and subsidence is evaluated following TD/T 1031 in all its parts, the statistical table for the newly destroyed land area of the monitoring period being Table B.2. Arable land quality grading follows GB/T 33469, and the evaluation of reclaimed arable land, garden land, forest land, grassland and construction land follows TD/T 1036, the statistical table for the evaluation of land resource reclamation and use being Table B.3.

8.4 The planting density, survival rate, retention rate and tree species of reclaimed forest at the time of monitoring are counted or computed and, together with the target values, used to judge whether the engineering design standard set for reclamation has been reached. Surface water environmental quality is evaluated following GB 3838, fishery water quality following GB 11607, the pollution risk control of agricultural land soil following GB 15618, the pollution risk control of construction land following GB 36600, farmland irrigation water quality following GB 5084, and the water resource environment of coal mining subsidence areas following GB/T 37574. The pattern and quality of the reclaimed ecosystem are evaluated following GB/T 42340 and its service function following HJ 1173; carbon sequestration by the ecosystem is computed from plant and soil sequestration, the carbon stock of forest land following LY/T 2988 and wetland carbon sequestration LY/T 2899. Taking the reference ecosystem and the quality evaluation results of the several ecosystems together, the state of ecosystem quality in the evaluation area and its dynamic features in different periods are analysed. The statistical table for the evaluation of the effect of ecosystem restoration is Table B.4.

9 Preparation of the monitoring and evaluation report and management of the data

9.1 The monitoring and evaluation report is to include the basic situation of the mine, the layout of the monitoring points, the monitoring area, the monitored objects and the monitoring indicators, the geological environment damage, the land resource destruction and the ecosystem damage or degradation since extraction began and during the monitoring period, the main reclamation measures and the works carried out, the present state and the trend of the monitored objects, and the evaluation of the effect of reclamation. From the monitoring and evaluation results, adaptive management is to be carried out and proposals put forward for correcting and improving the reclamation works and the technical and management measures.

9.2 The monitoring and evaluation report follows Annex C.

10.1 Following the laws, standards and specifications on natural resource survey and monitoring and on mine reclamation, the data are to be built into databases and managed by grade and class, each unit being responsible for the quality of its data, and the transmission, sharing and application of the data are to meet the relevant rules.

10.2 The several kinds of data produced at each stage of the work are to be classified, catalogued and archived in good time. Besides keeping the original paper records, a monitoring data set is to be built so that the data and materials are managed. The construction of the information system is to meet the national requirements on network security design.

10.3 A mechanism for the release of survey and monitoring results is to be established. After the survey and monitoring work is finished, the result data or the data catalogue that concerns the public is to be released to the outside in a unified way once the relevant review procedure has been carried out.