Solid mining waste with high concentrations of leachable arsenic, lead, zinc etc. has been excavated from more than 20 sites along river Baccu Locci and was deposited in the Central Disposal Cite. At the foot of the site is situated the external Permeable Reactive Barrier that treats aCID (pH = 5) percolate of on average 1 m3/day volumetric flow and appr. 500 mg/L of heavy metals in solution.