Sustainability website / Case Studies 2004 / Xstrata zinc / Landscape integration of a jarosite waste dump in San Juan

Landscape integration of a jarosite waste dump in San Juan

During 1995, jarosite waste pond No 2 ceased operations and pond No 3 became the active pond. Until 2003, pond No 2 remained commissioned to recover the liquor contained in it. These liquids contained metals and were treated at the metallurgical plant to recover zinc, as well as replace water lost during evaporation. Leaving the pond open allowed the stored waste to reach an optimum consistency allowing for closure in 2003.

Since jarosite is classified by Spanish and European regulation as a hazardous waste, pond No 2 had to be closed using specific procedures for hazardous waste landfilling installations. A bentonite ‘sandwich’ layer was placed over the upper surface of jarosite to protect a 1 mm thick polypropylene membrane. This membrane fully encapsulates the jarosite to isolate it from the environment. A 30 cm thick sand layer was deposited on the plastic membrane and a geotextile membrane was placed over it. In addition, over this geomembrane, a 35 cm thick layer of clay soil was spread which in turn was covered by a final 10 cm layer of topsoil. Draining systems were also installed to extract leachates from both the upper surface and the encapsulated cavity of the dump. After these operations the upper surface was seeded and the vegetation rapidly blended with the surrounding environment.