Environment in the permafrost regions

The rational siting of industrial projects, optimal development of regional infrastructure, safe and economical construction, safeguarding the region under development from dangerous geological and geocryological processes, and environmental protection must be based first of all on knowledge of the formation and development of the geocryological environment. Clearly the programme of rational development must be drawn up in accordance with the scheme of national regional planning and design, a) At the level of development of general plans for national development (AllUnion, departmental and republic schemes of development and disposition of production etc.). This is when the fundamental decisions are taken on kinds and methods of construction and of extensive regional development, and on ways of protecting the environment in the course of realization of the transformation programme (the first stage), b) At the level of regional planning when the schemes (projects) of regional planning provide siting of national economic projects (mining, power-generating, industrial centres, cities and settlements, etc.) as well as the arrangement of recreation and environmental protection zones (the second stage), c) At the level of design of particular industrial and other enterprises, when the particular projects for rational use of the geological environment are worked out. This includes protective and environmental protection measures guaranteeing safe construction, necessary comforts for human activity and living conditions and protection of the geological environment against harmful technological effects (the third stage). Clearly it is essential that continuity of decisions should occur at the different stages of drawing up the plan for rational use of the geological environment.

At the first stage the integrated schemes of rational use, control and protection of the region's geological environment must be developed on the basis of existing national geological, engineering-geological and geocryological maps and other materials. Concrete definition of the plans for rational use and protection of the geological environment in the course of development of regional planning schemes (projects) calls for special-purpose engineering-geocryological and hydrogeocryological surveying of the locality under development. It is necessary that the plans for environmental protection measures should be drawn up on this basis in accordance with the plan of development of the area. Detailed development of the protective and environmental protection projects (the third stage) is carried out on the basis of engineering geocryological survey materials.

One of the main challenges in the rational use of the geological environment is to guarantee the reliability of constructions. As noted above two alternative principles are used in operating with permafrost as a foundation for construction within the permafrost regions. To select which of them it is necessary to have information not only about the engineering-geocryologi-cal conditions of the area under development but also about the structures. In the absence of the latter, the question of the selection of the construction principle cannot be solved in the majority of cases. However one can give some recommendations on the primary use of one or another principle in the context of the small-scale engineering-geocryological mapping. Thus, it is advisable to perform the construction on the first principle in the regions where low-temperature ice-rich and highly ice-rich ground occurs (with ice content higher than 0.2-0.4 on account of the ice inclusions). Preference is given to the first principle in regions of high seismicity, because use of the second principle increases the seismic design and the cost of construction. It is appropriate to use the frozen ground according to the second principle in the regions where hard rocks and ground of low thaw consolidation are developed. It is possible to use both the first and the second principles in the regions with permafrost islands.

Thus, the information on distribution and mean annual temperature of frozen ground, on the prevailing complexes of pre-Quaternary rocks, on 'genetic' types and ice content of Quaternary deposits, on the genetic type of macrotopography and seismicity of the region, taking into consideration the accumulated experience of construction within the permafrost regions, allows selection of the principle of construction (Fig. 19.1). The schematic map shows the regions where: 1) only the first principle of ground as a foundation for structures is used; 2) the first principle is mainly used, but the second one can also be used; 3) the second principle is mainly used, but the first one can also be used; 4) only the second principle is used.

Clearly the given map cannot provide an unambiguous answer on the selection of the principle of construction, by virtue of its sketchy character; however, it guides the researchers toward the advisability of selection of one or other principle within each part of the permafrost region.

Rational use of groundwater within the permafrost regions includes the solution of the problems of its protection against pollution and exhaustion. The exhaustion of the groundwater resources occurs in the course of extraction from the interior of the Earth in amounts in excess of natural (or artificial) replenishment, as well as when the groundwater recharge and

Fig. 19.1. A diagram showing the permafrost region according to the principles of usage of the ground as a foundation: 1 - principle I only; 2 - principle I mainly, however principle II may be followed; 3 - principle II mainly, however principle I may be followed; 4 - principle II only; 5 - the permafrost limit.

Fig. 19.1. A diagram showing the permafrost region according to the principles of usage of the ground as a foundation: 1 - principle I only; 2 - principle I mainly, however principle II may be followed; 3 - principle II mainly, however principle I may be followed; 4 - principle II only; 5 - the permafrost limit.

replenishment conditions are disrupted in the hydrogeological structure. The latter is most probable and dangerous for those permafrost regions where the water-thermal regime is most sensitive to external impacts. The exhaustion of the groundwater in the permafrost regions can be prevented if certain rules of rational use are observed and a number of measures taken. First of all it is necessary that the areas of deep groundwater recharge should be kept unfrozen. These are radiation-heat, underwater, seepage and ground-infiltration taliks. Their freezing can be caused by industrial development of a region involving vegetation reduction, snow cover removal and consolidation, or creation of artificial covers on taliks during road construction, etc. Secondly, it is necessary that discharge of deep groundwaters through mine openings (holes and shafts), left after prospecting for mineral deposits and their development, be prevented. And finally, the artificial replenishment of the groundwater must be organized, involving a series of measures aimed at increasing the amount of groundwater in the waterbearing horizons, complexes and the whole hydrogeological structures.

Protection of groundwater in the permafrost regions against pollution stipulates a series of measures aimed at prevention, retention (or improvement) of its quality and the elimination of negative effects of technological loads. First of all the assessment of the natural capacity of groundwater to protect itself against pollution should be carried out on the basis of revealing protective factors preventing the contaminants from entering the groundwater basin. The zone of aeration, the first water confining stratum below the surface and hydrodynamic isolation of water-bearing horizons must be analyzed in this context. For the permafrost regions it is necessary to analyze the character of the perennially frozen ground and distribution of taliks, because the former constitutes a complete water confining strata, while feeding, discharge and flow of the groundwater occur through taliks.

The structures situated in the zone of continuous permafrost are less sensitive to technological impacts; the structures situated within the zone of island and discontinuous permafrost with wide development of precipitation-radiation taliks are most sensitive. One can recommend creation of special-purpose water protection zones for each type of hydrogeological structure within which it is necessary that a series of measures aimed at ground water protection be performed. Protection of groundwater against exhaustion and pollution for the permafrost regions as a whole and within the water protection zones should be directed toward keeping the natural thermodynamic equilibrium in the system 'surface conditions - frozen ground - groundwater'.

Experience in many developed regions shows that it is easier to protect the groundwater against pollution than to eliminate its consequences. This means that the problem of groundwater protection arises as early as at the first stage of development and that to solve this problem it is necessary to carry out a variety of geocryological-hydrogeological investigations, including survey, forecast and special-purpose regime observations within each region of the permafrost.

In the course of the industrial/economic development of the permafrost regions vast areas are involved. Within these areas disruption of the whole complex of the natural environment takes place. This disruption of natural conditions extends as a rule not only over the site under construction but also to the whole zone of infrastructure creation (access roads, electric power lines, service lines, etc.). The restoration by nature of plant communities proceeds very slowly, with some not being restored at all. Therefore as early as before the beginning of economic activity it is necessary not only to assess the engineering-geological conditions of the area and to make a forecast of their change, but also to establish measures aimed at recurvation (restoration) of the disturbed parts.

For this purpose the methods of biological recultivation are used. Biological recultivation consists of the artificial creation of vegetation covers of various kinds, purpose and productivity. Biological recultivation within the permafrost zone can solve the following problems: a) reduction or prevention of consequences of technological disturbance of the cover, associated with sharp increase of seasonal ground thawing depth; b) stabilization of sand embankments against the action of water and wind erosion; c) creation of green landscapes in agreement with the requirements of the inhabitants so far as sanitary and aesthetic aspects are concerned; d) restoration of necessary conditions for animals to live.

Methods of biological recultivation are various for the wide range of natural-climatic conditions of the permafrost regions. The main methods used within the areas of completely disturbed soil vegetation cover or on artificial embankments, are sowing of grasses, planting of shrubs with lime pretreatment and the application of mineral and organic fertilizers. Under good moisture conditions and with a modest degree of disruption of the turf one can restrict these methods to the application of mineral fertilizers with obligatory lime pretreatment in a number of cases, to restore the vegetation cover after carrying out levelling. The kinds and sorts of plants suitable for biological recultivation must have a number of morphological features such as sufficient resistance to cold, capacity to form strong turf cover for a long time, fast growth, annual fruiting, rather high germinating capacity and be present in quantity in nature. The efficient method to prevent erosion and to establish trees in the northern settlements is planting of native willow grafts. The essential condition for the safe overwintering of plants, especially of those brought here from other regions, is a rather thick snow cover. In winter one should not consolidate or remove the snow cover within the areas under recultivation and one should institute measures promoting snow accumulation in the areas where it is blown by wind.

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