Authors: Milczarek, MA; Steward, FM; Word, WB; Buchanan, MM; Keller, JM


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Milczarek, MA, Steward, FM, Word, WB, Buchanan, MM & Keller, JM 2011, 'Final results for the Morenci tailings experimental reclamation plots', in AB Fourie, M Tibbett & A Beersing (eds), Proceedings of the Sixth International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 281-292,

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Experimental monolayer evapotranspiration cover systems were installed in 1997–1998 over mine tailings at the Morenci Mine in the semi-arid southwestern United States. Test plots were constructed on the tailings dam side-slope to examine effects of cover treatments on vegetation and net infiltration flux into the tailings. Treatment variables were: cover thickness, three organic amendments applied at different rates, two mulch types, and seed mixes with native species only or native plus non-native species. Vegetation monitoring results indicated minimal differences in ground or canopy cover or species frequencies between cover depths, but greater mean vegetation cover was seen in organically-amended compared to unamended plots,and in mulched compared to unmulched plots. No differences were identified between seed mix variables. Matric potential data showed that, under normal precipitation conditions, the 60 cm cover more effectively limited infiltration of precipitation into the tailings at 180 cm below ground surface than did the 30 cm cover, but storm sequences delivering precipitation of 2.5 cm or more resulted in wetting of sensors at this depth. Unsaturated flow models calibrated to in situ matric potential data indicate long-term net percolation rates of less than 1 cm per year, with only nominal decreases in net percolation if the cover thickness is increased beyond 60 cm.

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