The RB is located in the Central part of Europe and takes a territory of 207,6 thousand km². Its population is 10 million people. There are two oil-refining plants in the RB. On its territory there are about 5 objects of petroleum storage (including about 4,5 thousand petrol stations), several oil and product pipe-lines the length of which is over 10 thousand km. Besides earlier in the RB there were military bases of the former USSR containing big petroleum depots. The majority of the objects mentioned were built in 60-70-ies and their equipment have mostly been aged by the present time. In this condition natural petroleum contamination has been widely spread.

Much attention to this problem in the RB in contradiction to the Western and CIS countries was paid in mid- 90-ies. At that time normative documents stricter than earlier regulating the problems of natural protection when building and using the objects of petroleum storage were prepared and approved and methodical recommendations defining the approaches to the estimation and prognosis of surface and underground water petroleum contamination were worked out. Directly by the CSRICDWR there were prepared STB 17.1.3.06-2000. Natural protection. Hydrosphere. Underground water protection from contamination. General requirements; STB 17.1.3.05-99. Natural protection. Hydrosphere. Underground and surface water protection from contamination when storing oil and oil-products. General requirements; the Temporary Regulations on ensuring ecological security of petrol stations; the Methods of inventorying the objects of petroleum storage and the form of the initial data collection; the Methods of ecological inspection of the functioning petrol stations and ecological grounding new oil and product reservoirs and petrol stations; the Methods of prognosis of contaminating substances migrations in the underground water-carrying horizons; the Recommendations. Minsk centralized system of dinking water supply. The measures on the protection of the underground water-intake "Zelenovka" from petroleum contamination. General requirements.

Parallel with this the Ministry of Natural Resources and Natural Protection and its subdivision - CSRICDWR made estimation and prognosis of petroleum contamination at the concrete objects. For the last 5 years study data have been fulfilled at the former military air base in Gomel district, Cobrin oil-base, the two parts of the oil pipe-line "Druzhba" break and also at several being reconstructed petroleum depots and petrol stations. The research included: soil geological survey, test well boring and soil testing; hydro chemical testing of rivers and reservoirs; underground water selection and testing in test and water operating wells; the prognosis of petroleum migration in rivers and underground water; working out the recommendations and measures on the petroleum contamination centers localization and contaminated parts of the territory rehabilitation.

The strongest center of underground water petroleum (kerosene) contamination was found at the former military base in Gomel district. The object is located between the rivers Sozh, Iput and Ut. The upper part of the hydro geological section, most exposed to contamination is presented by a week water-carrying Dnepr moraine complex, the power of which is up to 10-12m and by water-carrying lowermidpleistocene water glacial complex the power of which is up to 15m. The latter one is sufficiently widely used for the purpose of water supply. The main sources of underground water contamination are the three petroleum depots the capacity of which is correspondingly 5, 10, and 15 thousand tons each. Because of financial limitedness the research was carried out only at the second petroleum depot with the capacity of 10 thousand tons. As a result of boring of the 11 test wells there were discovered that the kerosene lens were formed in the area of about 60 thousand m² in the weak water-carrying Dnepr moraine complex on the surface of underground water at a depth of from 4,05 to 7,9m. Its power changes from 0,07 to 2,11m and in average is 1,1m. For the average rock porosity equal to 30%, the volume of the lost petroleum is about 29 thousand km². For a sandy rock water output equal according to the literature data to 0,1 it is possible to extract about 6,0 thousand m³ of kerosene from the lens. Thus the lens of kerosene is a subject of a commercial usage when carrying out the work on the rehabilitation of the contaminated parts of the former military base. At the present time the Institute is carrying out the work on contouring the lens by the method of the vertical electric boring. It is quite probably that the area and the volume will appear to be more than it is discovered by test boring. On the RB territory there are over 10 such military bases.

Cobrin oil-base examination took place in its reconstructing connection. The oil-base is located at Cobrin western outskirts 400m from the right bank of the river Mukhavets and 450m from the left bank of the channel Shevnya. The hydro geological section of the territory being studied consist of the water-carrying Dnepr over moraine water glacial complex and of the weak water-carrying Dnepr moraine complex. As a result of the research made petroleum concentration in soil is up to 62,2-129,0g/kg of dry bottom, in bottom – 11,9-16,3g/kg and in underground water – 5,4-20,8g/l. The area of petroleum contaminated soil is about 30% and of contaminated bottom – about 50% of the oil-base territory and is traced through a depth of 8m that shows active petroleum migration with underground water. The petroleum content is lessening with the depth. Its concentration at a depth of 0,4m averages 1084mg/kg; 1m – 1270mg/kg; 2m – 762mg/kg; 3m – 518mg/kg; 4m – 212mg/kg; 5m – 95mg/kg; 6m – 72mg/kg; 8m – 50mg/kg. In the northern part of the base there is a sector 4 thousand m² in area within which there is a deposit of petroleum (diesel fuel) on the mirror of the underground water in the form of the lens with the power changing from 1 to 5cm. The prognosis of the petroleum dissolved in underground water is made by the numerical modeling method. It has showed the frontier of the petroleum contaminated underground water with its concentration of 0,05mg/l that corresponds to the maximum admissible petroleum content in the fish-industrial reservoirs will not reach the river Mukhavets and the channel Shevnya even in 50 years. The rehabilitation in the contaminated parts of the oil-base include: the rehabilitation of the sectors with the high level of soil contamination (500-2500mg/kg) using technical recultivation methods – rather shallow (10-20cm) soil aeration by means of regular soil layer ploughing up, soil liming, etc; recultivation of the contaminated parts with the high level of soil contamination (more than 2500mg/kg) using special biopreparations of hydrocarbon microorganism destructors; a regime observant well building.

The Institute has also examined the consequences of the two breakdowns at the oil pipe-line “Druzhba”. As a result of the first one and the petrol A-76 leak in Corneev forest area, Gomel district the territory about 66,5ha in area was contaminated. At the time of the examination the maximum petroleum concentration in soil was 15300mg/kg of dry bottom, in bottom – 482mg/kg and in underground water – 1,2mg/l. Bottom petroleum contamination was traced trough a depth of 8m. Taking into account a considerable remoteness of the breakdown place from residential areas, open reservoirs, river sand water-intake wells rather slow petroleum migration with an underground flow, moderate petroleum carrying out with surface water, sufficiently high degree of the territory self-purifying ability (evaporation, carrying out with underground and surface water, absorbing by plants) and also the fact that the territory is not used actively un agricultural and other industry, the measures on the breakdown liquidation were mostly directed to the strengthening of the compensatory abilities of the territory (strengthening of the washing regime and the highest water plants planting); organizing control over the contamination center and carrying out annually (in Summer) measures on hydrocarbon biodestruction in soil bottom in the most contaminated parts. As a result of the second breakdown a diesel fuel leak happened and the territory 6ha in area was contaminated. By this 9 horticultural plots were contaminated in different extent. The minimum petroleum concentration in soil was 48mg/kg, maximum – 23290mg/kg. Bottom petroleum contamination is traced through a depth of 10m. The petroleum concentration at a depth of 0,9m averages 1397mg/kg; 1m – 1236,3mg/kg; 2m – 753,5mg/kg; 3m – 252,8mg/kg; 4m – 274,7mg/kg; at a depth of 5m – 209,2mg/kg. At a depth of 7, 9 and 10m the bottom was tested in three wells. The petroleum concentration has averaged correspondingly 350,8; 166,6; 145,9mg/kg. The irregularity of bottom contamination is caused by the peculiarities of the territory hydro geological conditions (different depth of the level bedding and seasonal inconstancy of underground water infiltrative feeding) and litological structure of the plot and is a result of the different petroleum transportation with underground water in bottoms having different physic mechanical and absorbing characteristics. Petroleum content in surface water objects changes from 0,01 to 31,4mg/l. Underground water in the part of the breakdown lies down at a depth of from 0,7 to 1,1m. They are timed to concide to the water-carrying upperonlake alluvial horizon. The petroleum concentration in underground water changes from 0,1 to 4960,0mg/l. With the depth the petroleum concentration is lessening. In the water-intake wells fitted out to a depth of more than 12m the petroleum concentration changes from 0 to 1mg/l.

Taking into account a settletive territory contamination by the second breakdown the main aim of the measures is to lessen the total level of the petroleum contamination of the plot ensuring manufacturing ecologically clean agricultural production and preserving the health of the people temporary residing there. For reaching the goal it is necessary:

• to provide a washing regime on the contaminated territory and that is especially important - in the parts that are used in agricultural manufacturing. This task can be decided at the expense of the lowering the underground water level as a result of carrying out hydro technical drainage melioration to a depth of the root inhabited level, which is 1,0-1,5m.
     
• to exclude the territory flooding by surface and underground water that is the main factor of transporting contaminative substances (petroleum in our case) from contamination center. This task can be decided as a result of draining the underground water to 1,0-1,5m.
    
• to provide the rehabilitation of the day surface of the contaminated territory in order to create rather comfort conditions there for people residing. This task can be decided in three ways depending on the territory natural conditions and its level of the petroleum contamination. The first way lies in pouring in clean bottoms and can be implemented in those parts that are used in agricultural activity. The second one means to conduct technical recultivation by dint of ploughing up a soil layer regularly and its liming, etc. It can be implemented in the parts with rather low contamination level. The third one is to recultivate soil using special hydrocarbon microorganism destructors. It can be implemented in the parts with a high contamination level.
     
• to provide haulage and purification of contaminated underground water. Considering the lost petroleum mostly masses in the upper part of the bottom water-carrying horizon the task of the haulage of contaminated underground water can be decided as a result of the hydro technical drainage melioration with lowering the underground water level to 1.0-1,5m. For purification contaminated drainage water special systems catching dissolved petroleum swimming on the surface are to be used. By haulaging and purifying contaminated underground water the problem of accumulating a part of drainage flow can arise. It can be decided by creating in the upper level a meliorative channel (in the area 200m in length from its source that is a wedging zone of contaminated underground water) of the accumulating capacity.
     
• to provide observation and control over the nature condition. This task is to be decided by creating permanent posts for observing petroleum content in soil, underground and surface water. The order of carrying out regime observations is defined considering natural conditions, the level of the territory contamination and its structure of engineering and technical natural protective measures.

A large number of measures of big volume at the second breakdown section are explained only by the fact that in summer period people live and are involved in agricultural activity there. That is why as a result of the contaminated land recultivation the necessary sanitary, hygienic and ecological norms of nature conditions must be provided there.

We can consider one of many examples of underground water contamination in the petrol station parts – when a petrol station is located in a sanitary protective zone (SPZ) of a drinking water-intake. Such example is Petrol Station №7 located in the third belt of the SPZ of the water-intake "Zelenovka".

The water-intake "Zelenovka" operates the water-carrying Dnepr and Sozh water glacial complex. Within the examining part where the Southeastern wing is located it is widely spread and is unsealed by the wells at a depth of from 24,8 to 52,2m. Mostly the bedding depth of the roof of the water-carrying horizon changes from 25 to 48m and averages 37,8m. Water contained rocks are represented by sands of different granulometric content in the section of which sufficiently powerful seams of gravel and gravel material and also lens and seams of rather waterproof sandy soils and loams are often can be seen. In the base of the Dnepr and Sozh water-carrying complex there are moraine sandy soils and loams of the Dnepr frozenness the power of which is up to 18 and more meters. In the roof of the water-carrying horizon there is a thickness of the moraine deposit of the Sozh frozenness represented by moraine sandy soils, loams and clays with the seams and lens of sand of different granulometric composition or gravel material. In the district of several wells clay formation of the Sozh moraine in the section are completely replaced by sand diversities, creating in closing thickness litological "windows", favoring water overflowing from upper lying horizons. Filtration factor according to the laboratory research data is 3,1-3,5m³/24h. Filtration factor magnitude found according to the data of building haulage changes from 9,21 to 29,02m³/24h. Water conductivity of the complex changes from 500 to 1000m³/24h. Water abundanty of the complex is characterized by the specific 1,3-12,2 l/s outputs. Piezometric levels in the wells are installed at a depth of 14,9-15m that corresponds to the absolute notes of 201,82-201,84m. The average absolute note of the underground water level at the period of the water-intake building was 205,4m. Thus there has been a little level shear for the time of water-intake operating. Specific level lowering factor for the last years has shown that a settled regime of underground water filtration has been formed at the water-intake. According to the regime observation data and the result of modeling operating stocks of the water-intake are formed at the expense of natural horizon stocks and drowing underground water resources.

Complex research in accordance with the present methodical documents was not carried out at the object. That is why the petroleum contamination characteristic of the part of the water-intake and petrol station area is made by the materials of individual scientific research works carried out in 1997 and 1999-2000. The works give incomplete and fragmentary picture of the object contamination. By characterizing petroleum contamination of the object there was made an estimation of the petroleum total content, volatile aromatic hydrocarbons (benzyl, toluene, ethyl benzyl) and half volatile polio aromatic hydrocarbons (pyrene, benzo(a)pyrene, phenanthrene, etc). In soil petroleum contamination is discovered in the area of the petrol station and adjoining territories to 50m in distance. Maximum total petroleum content of soil is 18181mg/kg of dry bottom and minimum one – 123,5mg/kg. In bottoms (including artificial ones) petroleum contamination is discovered at a distance of to 300m from the petrol station towards the water-intake "Zelenovka" and at a depth of to 45m. Maximum total petroleum content of bottoms has been discovered very close to the petrol station at a depth of 12,2m. It is 10500mg/kg. With this volatile hydrocarbon content is 1607mg/kg there. Minimum total petroleum content of bottoms (3,3mg/kg) is discovered at a distance of 70m to the South from the petrol station at a depth of 7,5m. It is 1320mg/kg. At a depth of 44m total petroleum content is 47,5mg/kg. With this it is important to note that in the petrol station area sandy soil deposits of the Sozh moraine damming operating water-carrying horizon are fully contaminated.
At surface water objects (reservoirs, meliorative channels) that are located at a distance of from 100 to 400m to the South from the petrol station the total petroleum content changes from 0,84 to 3.00mg/l. In underground water of "upper water" type bedding at a depth 1,4-5,6m from surface petroleum is discovered at a distance of 70-230m from the petrol station. Its total content changes from 0,14 to 0,38mg/l. In underground water bedding at a depth of from 12,0 to 16,0m from surface petroleum is discovered at a distance of 70-300m from the petrol station. Its total content changes from 0,04 to 0,36mg/l. The total volatile hydrocarbon content changes from 0,661 to 3,846mg/l. In pressure water being operated by the water-intake "Zelenovka" (the water-carrying Dnepr and Sozh water glacial complez) petroleum is discovered at a distance of 70-300m from the petrol station. At a distance of 70m from the petrol station its total content at a depth of 41,7m is 0,12mg/l. At a distance of 300m from the petrol station its total content at a depth of 40,6m is 0,02mg/l. In the operating wells of the Southeastern wing of the water-intake "Zelenovka" underground water petroleum contamination was not discovered by January 01, 2000.

The following measures making for the protection of the water-intake "Zelenovka" from petroleum contamination have been considered and estimated: liquidation of the center of underground water petroleum contamination, i.e. Petrol Station №7, contaminated soils, bottoms and underground water in that area; installation of a geomigrative screen on the way of the contaminated underground water movement; optimization of a regime underground water selection by the operating wells of the South-Eastern wing of the water-intake "Zelenovka". These measures do not replace the measures that are to be carried out in sanitary protection zones of water-intakes according to BN&R (СHиП) 2.04.02-84 and SanR&N (СанПиН) 10113RB99 and are additional.

Preliminary (on the level of scientific ground) analysis of measure variants of the water-intake "Zelenovka" protection from petroleum contamination allows making the following conclusion:

• It is necessary to carry out completely the measures on the contamination center liquidation (Petrol Station №7 reconstruction) for the water-intake "Zelenovka preservation;
    
• It is expedient to operate the South-Eastern wing of the water-intake "Zelenovka" according to the present water-intake scheme;
      
• The most effective and technically acceptable measure variant of the water-intake "Zelenovka" protection from petroleum contamination is to install a geomigrative screen consisting of a water-intake well with 1000m³/24h output with the existing intake regime and liquidation of the underground water contamination center (The Petrol Station reconstruction);
     
• Working out technical and economic ground of this measure variant should be considered as a prior direction of the research.

The examples given show the essential petroleum contamination of underground water in the RB and the necessity of its more thorough examining in order to ensure a normative quality of underground water.

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