Hydrogeohazards in post-mining areas – the phenomenon of uncontrolled groundwater outflows in wetlands

Abstract

Aquifers formed in the wetland area around the closed lacustrine chalk mine at Mierzyno (northern Poland) are distinguished by a specific groundwater flow system, the main component of which is lateral flow and ascent seepage from the deep aquifer to the ground surface. In investigating the origin of the uncontrolled groundwater outflows and the phenomenon of progressing spring pools, field and laboratory work, as well as model studies of groundwater flow, allowed assessment of damage to the soil and aqueous environment. These occurred due to defective reclamation of post-mining areas, as a result of which the natural hydrodynamic balance in the groundwater was disturbed. Artesian pressure in the deep aquifer caused layer interruption at the boundary of the lacustrine chalk deposit. In consequence, strong uncontrolled outflow of groundwater occurred, and the accompanying spring pools are changing their position as a result of headward erosion. So far, the amount of washed-out carbonate sediment exceeds 5,600 m3.