Ten Years of Tailings Reclamation Experiments at the Morenci Mine

摘要

During 1997 through 1999, eight tailings reclamation experiments were initiatedat the Morenci copper mine in Morenci, Arizona, USA. Reclamation success andthe effectiveness of various designs for evapotranspiration covers placed overtailings are being investigated. Test plots were constructed on the side-slope of anexisting tailings dam to test effects of cover material depth, native-only versusnative plus non-native species and organic fertilizer amendments. Ten years of vegetation monitoring indicate mean ground and canopy covervalues were greatest in organically-amended plots and lowest in unamended plots.Biomass values were higher for plots seeded with a native plus non-native seedmix versus native-only. Native vegetation varied by species in response toorganic amendments. Treatment differences have been sustained to date. Seven years of flux monitoring indicate that wetting to depths of 180 cm belowground surface occurs episodically in response to multiple short-termprecipitation events. Subsequent tailings drying and upward gradients have beenobserved to depths greater than 150 cm below the cover surface. Precipitationtiming is the primary influence on the ability of the covers to control infiltrationand deep percolation. Low-permeability tailings underlying the coversignificantly reduce deep percolation such that increasing cover depth onlynominally reduces deep percolation of precipitation.