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

• potential for topsoil deterioration was reported to apply to sites where
dispersed materials having SAR values of 20 or more and where only 30 cm
or less of topsoil were reapplied. With respect to the depth of respread
topsoil, R was reported that the upward extent of sodium migration would
increase proportionaly with the thickness of respread soil.
The identfication of diffusion as the actual mechanism involved in the
upward migration of sodium was reported by Merrill et. al. (1983a). This
paper reports that the main determinant controlling the amount of upward
sodium movement into the respread topsoil is the soil type (texture) and
water content of the spoil. Water movement is dependent on the upward
hydraulic gradient. Thus, very low hydraulic conductivities limit the flow of
water into or out of the mine spoil while soils with high hydraulic conductivities
allow more flow of water across the spoil-topsoil interface. Therefore, the
low hydraulic conductivities and high initial concentration of sodium in the
underlying spoil were responsible for the sodium movements by the process
of diffusion. Salt migration at two sites was not deemed to be a problem
where dispersion and saturation percentages were lower and where hydraulic
conductivities were higher. They reported that signficant sodium
acxumulations would occur in the respread topsoils only ''rf the associated
mine spoil has very low HC, which may result from dispersion due to sodicity
and high clay content, severe compaction or other reasons.° They concluded
that the degree of sodification was dependent upon the nature and depth of
• the overlying soil and that weathering of the soil which released divalent ions
would mitigate the physical effects of sodification.
In a study designed to evaluate the reclamation techniques alternative to
soil covering of sodic mine spoil lt was determined that the need and
effectiveness of calcareous soil amendments was dependent on the initial
spoil properties and amount of precipitation (Merrill et. al. (1983b). They
reported that saturation percentages above 90 are necessary for sodic spoils
to become dispersed. The most limiting factor in the suitability of sodic spoil
was attributed to a very low hydraulic conductivity which restricts root
penetration and not from a blockage mechanism. Application of gypsum was
found to signficantly lower SAR levels. Fallowing of respread topsoil, over a
four year period, was found to be a very poor means of ameliorating the
adverse properties of sodic mine spoil. No evidence of sodium leaching
could be detected in these very clayey mine soils, and due to increased soil
moisture levels, upward sodium migration was actually increased.
A number of topsoil depth studies, spanning several years and designed
to evaluate the response of plant growth over various levels of sodic and non
sodic spoil were conducted in North Dakota. They were summarized by Doll
et. al. (1984). to the present discussion, only those treatments dealing the
native perennial grasses such as those proposed for the Southfield Mine
Refuse Pile area will be discussed. The warm season grasses, blue grama
and sideoats grama, produced the highest growth on eight inches of topsoil
over 28 inches of subsoil. However, the eight inch topsoil over 20 inch
• subsoil produced 98 percent of the yield of the highest producing treatment
while the eight inch topsoil over 12 inches of subsoil treatment yielded 88
percent of the highest producing treatment. Crested wheatgrass yields were
highest on the 24 inch topsoil over 28 inch subsoil treatment, although, yields
of the 28 inch mixed topsoil and subsoil treatment yielded 91 percent of the
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