RECLAMATION SUCCESS

The Cabacal Copper and Gold Mine, an underground operation located in Brazil, was managed by RTZ Mineraco (RTZM), the Brazilian subsidiary of RTZ Corporation. The mine ran out of reserves after five years of operation and closed in 1991. The original vegetation in the area had been cleared for agriculture 10 years before the installation of the mine. Remnants of the original forest still existed on the upper parts of the surrounding hills. Therefore, the plan for rehabilitating disturbed areas detailed the work to be carried out both during and after operations in order to prepare the area for agriculture.

After analysis of the plant tailings for metal toxicity and acid generation potential confirmed that they were inert in both counts, the darn used for their storage was completely covered with a layer of soil and revegetated. The material used was the original topsoil which had been stored during darn construction. Mixtures of grass and legume seeds were spread over the dry part of the reservoir together with an application of nitrogen fertilizer. Water-resistant species of grass were planted over the wet part of the dam, thus forming a diversified environment along with already existing indigenous plant species. A drainage channel was excavated around the darn to divert runoff and protect the dam wall.

Tailings dam immediately after cessation of mining.

Waste rock dumps and slopes were stabilized and recontoured to blend with the adjacent terrain. Permanent rainwater drainage systems were constructed on every dump or slope before covering them with soil and seeding them with grasses and legumes. Initially the legumes provided a rapid vegetative cover over the bare surfaces. All the mine structures were dismantled and sold. Concrete and masonry walls of the industrial buildings were destroyed and the rubble used to fill the entrance of the underground ramp. Areas previously used for stockpiling ore were covered with soil and revegetated. The underground mine adit and the ventilation shaft were blocked and sealed with a reinforced concrete wall, covered with soil, and revegetated. All the former administration buildings and the concrete floor of the benefication plant were kept intact for future agricultural use.

In 1992, the Brazilian State Government granted RTZM a Certificate of Decommissioning for the successful closure and envirom-nental rehabilitation of the Cabacal Mine. The specific reclamation plans aimed at the safe decommissioning of the mine had been fully achieved.