A change to Swedish waste legislation in 2005 means that process waste with a given mercury content must be sent for final storage underground. Rönnskär has, therefore, been investigating a range of alternatives for final storage for a couple of years now. The investigation recommended a solution involving storing the process waste in the bedrock directly under the smelter. Drill cores from exploratory drilling underneath the smelter showed that the quality of the rock is good and complies with the requirements for deep storage. This will, furthermore, offer a comprehensive solution, with space for deep storage of other types of process waste generated each year at the smelter.
An application was submitted to the Swedish Environmental Court at the end of May 2010 and preparatory work has since then continued while the application is processed. This has included new test drilling work in order to further investigate the rock's properties, and advance planning for the location of the ramp opening. The ramp will, if the application is approved, comprise a 3 kilometre-long tunnel with a 1:8 incline that descends to a storage depth of 350 metres. It is estimated, if the environmental permit is granted, that the planned construction of the ramp will take approximately three years.