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

• calcium were reported to be sulfide oxidation, dissolution of gypsum, and
dxlamination of Ca-tactoids which lowered the pH and increased the amount
of soluble calcium. A corresponding decrease in pH consistently resulted in
the increased amounts of calcium present in the system. This factor was
discussed by Sandoval and Gould (1978) wherein they presented detailed
evidence that the solubility of calcium in the spoil system was directly related
to the pH of the spoil material.
The studies conducted by CSU on the New EIk Mine refuse (Abbott 1981,
and Fmbel 1982) contain data to support this phenomenon, wherein data
were presented to actually document the reduction in SARs due to
oxidization. A summary of the data collected by Abbott (1981) and Fmbel
(1982) for the various Veatments is summarized in Table 1.
These data show that the pH of the regraded refuse prior to Veatment
averaged 8.62 with an associated mean SAR value of 31.25. After four years
of weathering the pH was lowered to an average value of 7.59. Unfortunately,
no post Veatment SAR data were collected. It must be remembered that
application of gypsum at the rate of 3360 kg/ha failed to result in any
measurable plant growth response. From a soils standpoint, a t-test
comparison of these data document that the application of gypsum resulted
in signfcant decreases in EC and K, with corresponding increases in Fe, Mn,
total N, Cu and C/N ratios compared to the untreated plots. Changes in EC
with gypsum application were reported by Merrill et. al. (1983b), Gould (1982)
• and Dollhopf el. at. (1985) on fine textured mine spoils. According to these
three researchers, changes in EC suggests that the gypsum has dissolved.
Since the gypsum treated plots on the New Elk Mine refuse contained less
salts, it appears the infiltration and/or leaching of these plots may have been
enhanced over the non gypsum treated plots. Applying this logic to the New
Elk Mine sodic refuse, it appears that the lack of response to applied gypsum
was not because the gypsum did not dissolve, but because some other
factor was overriding the amendment properties of the supplemental gypsum.
A careful examination of these data demonstrate that the oxidization of
organic materials or pyrites suggested by Fimbel (1982) was more
responsible for the lack of response to the gypsum than was the lack of
dissolution of the gypsum into the refuse system. Upon applying the data
collected by Fmbel (1982) which shows a pH drop of over one unit within a
four year period, the changes can be directly applied to the calcium solubility
relationships presented by Sandoval and Gould (1978). They reported that
the solubility of calcium at a pH of 8.6 is 1.1 meq/I while at a pH of 7.85 is 2.7
meq/I. Thus, the oxidization of pyrites in this sodic refuse material created
a chemical form of mitigation more effective and rapid in ameliorating the high
SAR values than did the application of gypsum.
Data collected in connection with Project Reclamation in North Dakota
(Kollman 1979) support these conclusions. Based upon the correlation matrix
presented for sodic mine spoil, the factors most closely correlated wfth SAR
were reported to be saturation percentage (r=0.885), sodium (r=0.842) zinc
• (r=0.762) and copper (r=0.733), all of which were significant at the 0.01 level.
Using the corresponding decreases in the zinc concentration, which was the
only one of these parameters measured in both the pre and post treatment
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