Historical mining sites in the area fill the 11.2-km Kingsmill Tunnel continuously with acidic mine drainage containing metal contaminants that discharges directly into the Yauli River. Minera Chinalco Peru S.A. is cleaning up the historic pollution prior to initiating operations in the area because “it’s the right thing to do,” according to a Chinalco spokesperson.

HDS (High Density Sludge) technology is being employed, applying a sludge recirculation process to create a crystalline sludge that is claimed to minimize waste volume, lower disposal costs and reduce environmental impacts.