During and after mining the disturbed area undergoes various stages of rehabilitation. Waste rock dumps can be flattened out and contoured to fit into the surrounding topography.The dumps are normally covered in topsoil and revegetated with native plants. The mining pit may also be filled in with waste rock or in high rainfall areas like PNG, become a water catchment area. Possibilities for a new industry can be created by using the flooded pit for aquaculture or the water contained within the pit can be used to generate hydro electricity.Tailings dams contain finely-ground rock material left over after the valuable minerals have been extracted from the ore in the processing plant, often set like clay and contain residual chemicals. This material is normally contained within a large earth walled dam, called a tailings dam. Once mining is completed and the processing plant has no more ore to process, then the tailings dam must be rehabilitated by removing excess water and the covering the tailings material with an inert compacted layer of clay, topsoil and vegetation. Environmental monitoring of the rehabilitation and water quality occurs after completion of the rehabilitation for many years until it meets the community and government expectations.