Direct revegetation of coal tailings at BHP-Saraji mine (Central Queensland)

A direct revegetation strategy involving minimal capping for coal tailings is sought to reduce dust hazard and maximise the potential for later coal extraction. Coal tailings produced from washing mined material are composed of ca. 50% coal and 50% inorganics and are pumped as a slurry(c.30% solids) to holding dams for disposal. On cessation of filling, surface crusting slows evaporation, and slow drainage limits consolidation and vehicular access. Studies were conducted on tailings dam #3 at Saraji Mine. The dam has a storage capacity of ca.3,500,000 m) (20 m height, 23 ha) and was last used in 1985. The moisture content 1 m below the surface was, in July 1994, 10-30%. Substrate characterisation indicated the material should allow growth of salt tolerant plants, with a pH1:5 of 6.5-8.5 and a salt content (EC 1:5) of 2.5 dS.m-l , except in the immediate area of the old inflows where substrate pH was low (pH1:5 2-4. Nutrient analyses indicated a low CEC (<20 meq.lOOg-1), with deficiencies in N (0.6 mg N03:N.kg-l) and P (bicarb extractable; 6 mg PO4.kg-1). Plant available moisture was 20%, but the material was poorly aerated where moisture content was high.