Planowana kopalnia odkrywkowa na złożu węgla brunatnego „Oczkowice” zagrożeniem dla gospodarki wodnej i środowiska południowo-zachodniej Wielkopolski

Abstract

The planned “Oczkowice” opencast brown coal mine as a threat to the environment and water management of the south-western Wielkopolska region.A b s t r a c t. The ‟Oczkowice” brown coal deposit composed of Neogene sediments was documented between 2011–2014 in South– West of Wielkopolska region. The lignite deposit, located between Miejska Górka and Krobia communities, occur 110–140 m below the surface. The designed open-pit mining requires the Quaternary and the Neogene–Paleogene aquifers to be drained and depleted up to the depth of 115–165 m for at least 50 years. The article is based on a hydrogeological expert report (Dąbrowski et al., 2015) andpresents both analytical and model calculations as well as potential risks to the environment and water management of south-western Wielkopolska region. According to the expert estimation, the initial output resulting from draining of sector I would reach 4930 m3/h (81.7 m3/min). Thereafter, it would be reduced to 3520 m3/h (58.7 m3/min) at the end of sector I mining. The radius of depression cone of the Quaternary structures would be up to 3–10 km far away from the open-pit but it would be widespread by ca. 20–25 km in the Neogene–Paleogene basins. According to the calculations the groundwater losses caused by the ‟Oczkowice” open-pit draining would attain 59% resources of the Quaternary structures and 92% of the Neogene–Paleogene basins in the Gostyński district and 45% and 62%, respectively, in the Rawicki district. Reducing the piezometric pressure of the Neogene–Paleogene basins would result in increasing the chloride water ascension of the underlying basement and consequently its discharge to rivers.