An Assessment of the Direct Revegetation Strategy on the Tailings Storage Facility at Kidston Gold Mine, North Queensland, Australia

A closure objective of Kidston Gold Mines Limited was to return a self-sustaining savannah woodland vegetation of native trees and introduced and native ground cover species to areas disturbed by its Kidston mining operation. One of the major areas of disturbance was the 310 ha tailings storage facility (TSF) into which approximately 68 Mt of tailings were deposited between 1985 and 1996. Early revegetation trials conducted in the early-mid 1990s demonstrated the capacity of the tailings to support vegetation growth without the requirement for a capping layer of soil or other cover material. The tailings storage facility was decommissioned at the end of 1997 and as the accessible area on the surface of the facility became progressively available (from March 1998 through to December 2001), planting and seeding of over 50 native tree and shrub species and 8 introduced and native pasture species was undertaken. With the support of drip irrigation over the first few months and initial fertilisation, the alkaline tailings have proven to successfully support the establishment and growth of a range of native tree and shrub species. Greatest success with upper-and mid-storey species has been where competition from introduced grasses has been minimised. Since 2001, up to four areas of different aged rehabilitation across the surface of the TSF have been monitored on an annual or biennial basis by The University of Queensland's Centre for Mined Land Rehabilitation (CMLR). The overall aim of the Kidston monitoring program has been to assess the progressive development, functioning and composition of the rehabilitation areas prior to relinquishment by the company. This paper presents some background on rehabilitation works and research trials undertaken on the tailings and reports on the most recent findings from the vegetation monitoring that has been conducted on the four TSF sites (TD40, TDNA, TDNB and CTD) in the period 2001 to 2005. The 2005 findings are presented in relation to two unmined analogue communities and preliminary rehabilitation targets. Monitoring against these interim targets has proven to be a valuable process for tracking the structural and functional development of these vegetation communities. In addition, an ongoing assessment of the tailings attributes contributes to our understanding of soil development processes and hence the longer–term sustainability of the reconstructed ecosystem as the company aims towards lease relinquishment.