Closure of German Hard Coal Mines: Effects and Legal Aspects of Mine Flooding

Following the closure of the last hard coal mines in Germany, pumping is no longer necessary. However, the resulting rise of mine water can affect the environment. Laws have been enacted at the European and national level to protect properties. Within the framework of the approval procedure, it must be determined whether the cessation of pumping may cause unacceptable effects, including water pollution. With regard to water protection, the European Union has issued the Water Framework and Groundwater Directives, which have been implemented into German national law. These contain the prohibition of deterioration and the requirement for improvement, with the aim of maintaining or achieving good ecological and chemical status. However, before the target mine water level is reached, the water does not need to comply, since although the pumps are switched off, no mine water is being discharged. This also rules out permit requirements, which only go into effect when the target mine water level has been reached and mine water is discharging. Obviously, however, detailed planning before then is necessary.

Kherzet Youcef Mine Flooding of 2nd June 1990 Revisited (Northeastern of Algeria) Origine and Hydrogeological Consequences

This work is part of the hydro geological study of the Kherzet Youcef deposit. The polymetallic deposit of Kherzet Youcef is known since the beginning of the 20th century. It is known by the exploitation of Lead and Zinc ore. It is located 50 Km southeast of Setif (North-eastern Algeria) and 5.5 Km west of Ain Azel. Mineralization can be described by some ore bodies (about 25). The thickness variate from a few centimeters up to 3 m. These bodies are located on the layers of dolomite and dolomitized marl and along the Kherzet Youcef fault. The geological reserves of Zinc and Lead ore are of the order of 1.6 million tons. This ore has a Pb content of 3.6% and Zn content of 18.4%. The projected annual exploitation was 100 thousand tons per year. Hydro geological studies carried out successively (1973-1977) and (1981-1983) revealed the existence of an aquifer system located west of the Kherzet Youssef fault. It is characterized by the presence of Karts and by strong cracking due to local brittle tectonics. These two characteristics define the filtration and storage capacity of very abundant groundwater. This groundwater represented a major handicap for mining in view of the large amounts of water that required the installation of major pumping and drainage devices. The Kherzet Youssef mine has experienced frequent flooding in the past at a time when technology could not pump efficiently. It caused the mine to close several times. In June 1990, the mine experienced a flood of great magnitude that has never been observed and despite the large installed means of pumping, this 'water costled to the total drowning of the mine, the death of 19 workers and the stoppage of the exploitation of this deposit since. Pitting attempts were carried out with a pumping capacity of 1100 m3/h, then 1800 m3/h but without success. The interpretation of the drawdown data and field observations made it possible to conclude that this accident was only the result of the general destabilization of the massif. Our complementary work by geophysical prospecting made it possible to represent the configuration of the underground layers and demonstrate the hydrodynamic communication between the two East and West compartments of the deposit.

Kherzet Youcef Mine Flooding of 2nd June 1990 Revisited (Northeastern of Algeria) Origine and Hydrogeological Consequences

This work is part of the hydrogeological study of the Kherzet Youcef deposit. The polymetallic deposit of Kherzet Youcef, known, since the beginning of the 20th century, by the exploitation of Lead and Zinc ore, is located 50 Km southeast of Setif (North-eastern Algeria) and 5.5 Km west of Ain Azel. Mineralization is represented by some ore bodies (about 25). The thickness variate from a few centimeters up to 3m. These bodies are located on the layers of dolomites and dolomitized marls and along the Kherzet Youcef fault. The geological reserves of Zinc and Lead ore are of the order of 1.6 million tons. This ore has a Pb content of 3.6% and Zn content of 18.4%. The projected annual exploitation was 100 thousand tons per year. Hydrogeological studies carried out successively (1973-1977) and (1981-1983) revealed the existence of an aquifer system located west of the Kherzet Youssef fault characterized by the presence of Karts and by strong cracking due to local brittle tectonics. These two characteristics define the filtration and storage capacity of very abundant groundwater. This groundwater represented a major handicap for mining in view of the large amounts of water that required the installation of major pumping and drainage devices. The Kherzet Youssef mine has experienced frequent flooding in the past at a time when technology could not pump efficiently. It caused the mine to close several times. In June 1990, the mine experienced a flood of great magnitude that has never been observed and despite the large installed means of pumping, this "water cost" led to the total drowning of the mine, the death of 19 workers and the stoppage of the exploitation of this deposit since. Pitting attempts were carried out with a pumping capacity of 1100 m3/h, then 1800 m3/h but without success. The interpretation of the drawdown data and field observations made it possible to conclude that this accident was only the result of the general destabilization of the massif. Our complementary work by geophysical prospecting made it possible to represent the configuration of the underground layers and demonstrate the hydrodynamic communication between the two East and West compartments of the deposit.

Groundwater Chemistry and Stratification in the Flooded Hard-Coal Mine Shaft “Nowy I” (Nowa Ruda Region, SW Poland)

The flooding of unprofitable underground mines is one of the methods of their closure. After the drainage of the mine has stopped, the voids left in the rock mass as a result of mining, are filled with inflowing groundwater. In this way, reservoirs of groundwater with specific physicochemical parameters are formed. These parameters depend on the interaction of the water flowing into the workings with the rock formations. It was the economic situation in the 1990s that led to the closure of hard coal mines in the Nowa Ruda Coal Basin, where the flooded “Nowy I” shaft is located. In that shaft, in 2008, hydrogeological research was performed and groundwater samples from five various depths were collected. The aim of the study was to recognize if groundwater stratification occurs in the shaft. In 2015, a sample of the water outflowing through the “Aleksander” adit was taken to check the potential influence of mine flooding on the environment and to confirm the changes in groundwater chemistry over time. These were the first, and so far, the only studies on the chemical composition of water in the flooded mine in that area. The article presents results of the preliminary research, which confirmed the existence of not obvious hydrogeochemical stratification in the shaft. It can be assumed that below the depth of 350 m, the water circulating through mining excavations exhibits the highest electrical conductivity and the highest concentration of Ca2+, K+, SO42−, Fetot. In the depth range of 320–380 m there is a transition zone, in which a decrease of Eh value and a change of reduction and oxidation is recorded. Above this zone, infiltration water inflow, from outside the shaft casing, dominates. The research shows that it would be necessary to perform additional sampling of the water in the shaft at greater depths, as well as to perform isotope analysis and periodical tests for at least several years. This would allow for a more complete characterisation of hydrogeochemical processes taking place in the flooded mine.

Mine Flooding History of a Regional Below-Drainage Coalfield Dominated by Barrier Leakage (1970–2014)

A 44-year record of water level fluctuations in a series of adjacent closed underground mines documents the history of closure and mine flooding in the Fairmont Coalfield, one of the oldest coal mining districts in the Pittsburgh coal basin, West Virginia, USA. As closures proceeded and mines began to flood, US environmental regulations were first enacted mandating mine water control and treatment, rendering uncontrolled surface discharges unacceptable. The purpose of this study is to present this flooding history and to identify critical events that determined how mine pools evolved in this case. Also examined is the strategy developed to control and treat water from these mines. Flooding is visualized using both water level hydrographs and mine flooding maps with the latter constructed assuming mine water hydraulic continuity between one or more mines. The earliest flooding formed small pools within near-surface mines closed prior to 1962 yet still pumped following closure to minimize leaking into adjacent still-active workings. These subpools gradually enlarged and merged as more closures occurred and the need for protective pumping was removed, forming what is today referred to as the unconfined Fairmont Pool. Later, deeper mines, separated by intact updip barriers from the Fairmont Pool, were closed and flooded more gradually, supplied in large part by leakage from the Fairmont Pool. By 1985, all mines except 2 had closed and by 1994 all had fully flooded, with the Fairmont Pool interconnected to deeper single mine pools via barrier leakage. As protective pumping ceased, the Fairmont Pool rose to a water level 3 m higher than surface drainage elevation and in 1997 discharged from an undermined section of Buffalo Creek near the Monongahela River. The principal mine operator in the basin then designed a pumping system to transfer water from the Fairmont Pool to their existing treatment facilities to the north, thus terminating the discharge. It may be concluded that the progress of mine flooding was influenced by mining history and design, by the timing of closures, by barrier leakage conditions, and by geologic structure. A key element in how flooding proceeded was the presence of a series of intact barriers separating deep from shallow mines. The shallow mines closed and flooded early, but then lost sufficient water by barrier leakage into the deeper mines to delay the completion of flooding until after the deep mines had all closed and flooded as well. Intensive mine water control has continued from the 1997 breakout to the present. The final water control scheme was likely unanticipated and serendipitous; future district-wide mining efforts should be advised to consider in advance closeout strategies to control mine water postmining.

Technical research on controlling major karst water hazards in China coalmines

Karst water is one of the major water hazards in China coalmines, causing frequent mine flooding and sever human casualties. This article, starting out on the spatial relation between mining facility and karst aquifer, extensively illustrates the techniques to identify water burst risks in karst aquifer and field testing methods of key parameters; primary water hazards control techniques for specific mining conditions and hydrogeological properties, such as retaining water-resistant safety rock pillar, water draining and depressurizing, bottom aquifuge consolidation grouting and revamp. All achievements can be of reference to other coal-producing countries confronted with karst water hazards.