Formation of Groundwater Quality of Drinking Water Intake Near the Flooded Pits (Middle Urals, Russia)
Rybnikova, Liudmila; Rybnikov, Petr
The Institute of mining, Ural branch Russian Academy of Sciences, Russian Federation
1. Development of mineral deposits is accompanied by dewatering, usually with drainage from the drain sump and dewatering with the help of drainage wells. Groundwater pumped out by drainage wells outside the pit is in the most cases of good quality and meets the requirements for drinking water. They can be used as a source of drinking water supply. In the middle Urals since the mid 80-ies of the last century, water supply of a number of cities with a population of about 50 thousand people is carried out with using such facilities. However, after the cessation of mining and flooding of mine workings, there is a gradual deterioration in groundwater quality at such water intakes. 2. On the example of Lipovsky water intake the analysis of mass balance was carried out to determine the processes of the water quality formation. The filling of the depression cone is accompanied by the flooding of the pit with the formation of a pit lake. The water quality in the flooded pit is good. 3. It has been established that the cause of the deterioration of the groundwater quality is the influx of water, forming in the technogenic aquifer in the sulphidized rock mass. These rocks were placed in the pit as an internal dump during the development of mineral deposits. The mass flow from the technogenic aquifer in the pit lake is twice the mass flow from natural resources. The rise of groundwater level in technogenic aquifer with free oxygen access leads to active geochemical weathering of sulfide-containing minerals and dissolution of secondary sulphates. This is the source of increased concentrations of sulphates, nickel and other components in the water intake on the eastern side of the pit. 4. The technogenic aquifer has become a ”generator " of sulphate salts and a source of increased nickel content, to values exceeding the standards. To preserve the good quality of groundwater after pit flooding, it is necessary to exclude the placement of rocks containing sulfide mineralization in the pits.