Two people have been confirmed dead, four people are being trated in jospital, and 47 homes have been destroyed following the collapse of a mine tailings pond in the Potosí Department of Bolivia. The incident happened at Laguna Kenko in the Llallagua District, on the Bolivian Altiplano, at about 5.00 am on Sunday 16 March 2025, following heavy rains in the area, associated with the local rainy season, and led to hundreds of tonnes of a grey, muddy slurry washing through the community of Andavilque.
The mine tailings pond was associated with the Siglo XX Mine, which opened in 1900 and closed in 1987, being at its peak the most important tin mine on the Bolivian Altiplano. The mine was a centre of union activity in Bolivia, and in 1967 was the site of the San Juan Massacre, in which the Bolivian military shot more than 90 men, women, and children at close range, killing at least 20, in rsponse to a threat to strike by miners, an event considered to be the worst massacre in Bolivian history. Although the mine itself has closed, mine tailings at the pond have been worked by the Cooperativa Multiactiva 'Catavi Siglo XX Ltda' since 1994, and the tailings pond was associated with this operation.
Tailings ponds are used to store sediment-laden waters from mines; such waters typically contain a high proportion of fine silt and clay particles, which take time to settle out of the water. The resulting water may be fairly clean, or may contain other pollutants (typically acids, either generated by the local geology or used in the mining process), and need further treatment. The waters of the Laguna Kenko were acidic, and contained dissolved tin, lead, and arsenic, although these were not at levels as high as in solid waste at the site.
The Bolivian Rainy Season, typically lasts from November to March, driven by high evaporation over the Pacific Ocean during the southern summer, which falls as rain when air currents coming from the ocean are pushed upwards as they encounter the Andes Mountains, causing the air to cool and lose its moisture, with peak rainfall in January and February.
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