A hydrostratigraphical approach to support environmentally safe siting of a mining waste facility at Rautuvaara, Finland Based on the construction of a detailed sedimentological model, hydrostratigraphy and local groundwater/surface water flows, this paper analyses the Niesajoki river valley as a suitable area for the expansion of a tailings facility, associated with the nearby Hannu-kainen (Cu, Au, Fe) mine, Finnish Lapland. Three different glacial/interglacial cycles were identified from the sedimentary observations and, optical stimulated luminescence (OSL) datings showed them to be of Early to Late Weichselian in age. Two groups of hydro-stratigraphical units were identified from hydraulic conductivities. The first, fluvial deposits, lie in the centre of the valley along the valley axis, and are the main aquifers. The second, till group, with lower conductivities, are located on the flanks of the valley. The thickness and complexity of sediments varied across the study area. To the E/SE of the valley, sediments are thick (~40 m), and more complex., In contrast the S/W/NW of the area, sediments are thinner (~10 m) and more simple. Groundwater is found to flow towards the centre of the valley and along its axis, where a bedrock controlled divide forms two groundwater basins. Based on the results of this research, it is suggested that any future expansion of the tailings facility should be restricted to the western and southern side of the valley, where waters are more manageable.