PERMFILE55696

• Permit No: C1981014
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: EXHIBIT 09 COMPARISON OF REFUSE AND SOIL SUITABILITIES
• Media Type: D
• Archive: No

• highest yielding plot. They concluded that the optimum thickness of respread
topsoil to maximum native grass growth was 30 inches while 20 to 28 inches
were required to maximize nested wheatgrass growth. In another study ft
was reported that topographic position, aspect and the quality of subsoil
medium over sodic spoil greatty influenced the growth of crested wheatgrass
and Russian wildrye. On north facing slopes, maximum yields were reported
at soil thickness of approximately 32 inches while on south facing slopes no
differences in yield response were evident for topsoil thicknesses of between
16 and 52 inches. Highest yields were obtained on the subsoil medium
having the lowest amount of clay and water holding capaaty.
Plant growth response on sodic spoil over a five year period was reported
by Barth and Martin (1982) and Barth (1984) for two mines in the Northern
Great Plains having SARs between 25 and 81. Perhaps the most signficant
finding of this study which can be confirmed by the findings in North Dakota
(Doll et. al. 1984), but which was seemingly ignored by the North Dakota
researchers, is that the optimum thickness of soil cover necessary to
successfully reclaim a given site decreases as the reseeded plant community
matures and as the chemical properties of the respread topsoil and spoil
reach a new equilibrium. Outside of the few studies, (such as those of
Sandoval and Gould 1978) wherein inadequate soil covering was applied to
a sodic spoil, virtually all other long term topsoil studies support this
observation. Several examples of this trend are cited in Crofts et. al. (1987).
• Barth (1984) developed a predictive equation to determine the thickness of
cover soil necessary for maximum perennial grass production on sodic spoil
for the Northern Great Plains. His data suggest that the optimum depth of
soil necessary for reclamation of sodic spoil with SARs of upwards of 81 was
71 cm and that a respread soil covering thicker than this amount would result
in decreased yields. These observations are consistent with the findings
reported by Doll et. al. (1984). Upward migration of sodium was detected in
some of the plots of Barth (1964). Soil samples collected where the respread
topsoil was 10 cm thick revealed no upward migration of sodium, while
samples taken from the 43 cm thickness of respread topsoil revealed that
upward migration of sodium was evident to a height of 7 cm in the respread
topsoil. Samples taken from 85 cm of respread topsoil showed that sodium
had migrated 14 cm above the spoil-topsoil interface. These findings
regarding the differential upward migration of sodium according to the
thickness of respread topsoil are consistent with the findings reported by
Merrill et. al. (1980).
Working at the Decker Mine in southeast Montana, Dollhopf et. al. (1985)
reported that two years after placement of 70 cm of respread topsoil over a
sodic spoil (SAR 23), no sodium migration could be documented. However,
seven years after placement of the topsoil the effects of sodification could be
measured on some plots to a height of 46 cm in the respread topsoil. They
cautioned that upward migration of sodium might become a potential problem
but that the process would most likely be a very slow one restricted to sites
• with over 35 percent clay, and under 45 percent sand.
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