Blue Lagoon pond closure, Pirdop, Bulgaria

Umicore purchased a copper smelter from the Bulgarian government as part of Bulgaria’s transition from state owned properties to private ownership. Contingent to this purchase, Umicore and the Bulgarian government agreed to close a slimes pond referred to as the Blue Lagoon as part of a site wide cleanup primarily financed by the World Bank. The Blue Lagoon was used to contain waste slimes generated from the wastewater treatment system at the site. As part of Umicore’s site wide cleanup, approximately 800,000 m 3 of contaminated soil and demolition debris (waste material) was placed in the slimes contained in the Blue Lagoon. Waste material was placed around the perimeter of the lagoon and used to construct a sequence of roads through the slimes forming a series of cells containing slimes. Additional waste was placed on top of the slimes and graded to drain. A low permeability cover system was constructed over the waste material. Unique aspects of the Blue Lagoon closure construction included creating mud-waves to displace the slimes during construction of the roads and floating a cover over the slimes in the interior of the pond. Pore pressure dissipation curves and settlement profiles were monitored to assess the degree of consolidation continually during construction.