Store and release cover performance at Cadia Hill gold mine, Australia

Abstract

The rehabilitation of waste rock dumps to minimise potential contamination is site specific; being a function, among other factors, of the rock types, the dumping and storage method employed, and the climatic setting. Three experimental store and release cover trials have been developed and constructed as part of a larger trial waste rock dump at Cadia Hill gold mine (Newcrest Mining) in Central New South Wales, Australia. The development of store and release cover systems for the temperate conditions typically experienced at Cadia (700 to 1,200 mm of rainfall annually) signals a significant departure from the climatic settings of other store and release cover system applications throughout Australia (typically semi-arid climates with less than half the annual rainfall of Cadia). The store and release cover system relies on the storage of rainfall during the wet season and its release during the dry season through evapotranspiration. It typically comprises a compacted fine-grained sealing layer (typically compacted clay) overlain by a significant thickness of loose “rocky soil mulch”. Where there is a local paucity of clay and suitable rocky soil mulch, it may be possible to manufacture suitable cover materials from mixtures of benign tailings and benign waste rock crushed by haul truck trafficking. The paper describes trial store and release covers constructed at Cadia using such mixtures, the instrumentation of the trial covers and monitoring data collected over the past four years.