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8 <br />• in soils and results in reduced infiltration and lower hydraulic con- <br />ductivity. <br /> Compaction of regraded surface mined land cannot only occur on the <br /> soil surface by raindrop impact but can also occur in the spoils during <br /> regrading (Power et al., 1978). Overburden is commonly removed into <br /> long piles by a dragline, then the spoil piles are reshaped by a bull- <br /> dozer to a final configuration. More Compaction occurs along the center <br /> of the axis of these two operations while less compaction occurs along <br /> the sides where spoils are pushed downslope. Power et al. (1978) found <br /> bulk densities of undisturbed overburden in the Northern Great Plains <br /> range from 1.4 to 1.7 g/cm3 while the bulk densities of spoils were found <br /> to vary from 1.1 to 1.4 g/cm3. The authors give no opinion on whether <br /> the bulk densities of these spoils have increased since regrading, or if <br />• h <br />b <br />lk <br />~ t <br />e <br />u <br />densities will increase in the future. Research by Sindelar <br /> et al. (1974) in Montana, also in the Northern Great Plains, has shown <br /> bulk densities or" surface soil horizons from regraded surface mined land <br /> that had been reshaped with heavy equipment were higher than adjacent <br /> native range. Ripping the spoils to a 0.6 m depth with an instrument <br />~ - pulled by a crawler tractor typically reduced bulk densities from 1.6- <br /> 1.9 to about 1.5 g/cm3. <br /> The rate of water movement through the soil is dependent on the <br /> saturated hydraulic conductivity which is dependent upon the soil <br /> particle size distribution and characteristics of the pore spaces, which <br /> in turn change with corresponding changes in bulk density. Arnold <br /> and Dollhopf (1977} determined saturated hydraulic conductivity through <br />• depth for four different treatments at a mine near Colstrip, Montana. <br />