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<br />f The buried sludge layer and pelletized cover methods are still unproven ~
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<br />in [he field and the actual costs incurred from application of these proce- ~`1 ~>i ;a
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<br />dares to differing sites tray range to double the lower calculated figure, How- ,
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<br />! aver, if the calculated cost range of $735 to $1,470 per acre is approximately :
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<br />correct for the combined buried sludge and pelieted surface method, this pro- ~ ~,~
<br />f cedure is comparable on a cost basis to that using a 12-inch soil cover and j >>
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<br />'
<br />'
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<br />vegetation, and tests may be warranted to evaluate the relative effectiveness i~Mi
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<br />.~
<br />of both procedures for obtaining vegetation on adverse sites. If the use of .li'•~`
<br />?~i
<br />pellets is not mandatory to achieve satisfactory vegetative stabilization, .•
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<br />then the lowered cost for application of only buried sludge layers and vegeta- ~;i,~'~
<br />I
<br />tion makes the method more competitive. i! ~~'
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<br />CONCLUSIONS •+~ .I
<br />L'~iLl ~
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<br />y,• •
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<br />1. Physical, chemical, vegetative, and combination stabilization methods ,~~;;{7~~~
<br />have been developed by the Bureau of Mines and the mining and milling industry ji;~a. "~~ei
<br />'~
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<br />c that offer romise of retardin or eliminatin erosion of fine-sized mineral
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<br />sas[es.
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<br />
<br />2. Vegetative stabilization is preferred in that it offers greater per- ~;'~i aj :'~.
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<br />•anenc and im rovement in a earance than other stabilization techni ues, .
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<br />wmbination methods of physical-vegetative (hydromulching, matting, and soil li~;'.'~f!.!
<br />cover and the chemical-ve etative rocedures ermit effective establishment ~'';'i~:j
<br />aE vegetation directly onto tailing material except for excessively acidic, "`~i~''
<br />Sasic, or saline wastes. Costs for these methods-range from $120 to $1,750 ![,y,il:
<br />per acre in 1973, j f.':`ji~
<br />3. Pelletization of tailings to improve physical structure is beneficial 1;:'~.i;.:
<br />in establishin a ve etative cover and artificial soils can be formed b com-
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<br />~Sining municipal wastes such as sewage sludge or refuse compost with mineral .
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<br />+astes. :. :'ti
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<br />f 4. The use of 2-inch layers of sewage sludge or compost buried 3 to I.`';.
<br />1 Sinches under the surface of tailings prevents or retards the oxidation of ,i.f. ~
<br />,sulfides and the consequent acidification of sulfide-containing tailings. .The i, f
<br />~
<br />j Suried organic layer method would aid in achieving stabilization of tailings ':
<br />"~'''
<br />' subject to such oxidation.
<br />. ,I~•', ~~ +
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<br />
<br />5. Nitrogen fertilization maintenance costs for vegetatively stabilized I
<br />i~.:. ' • i
<br />„ .:,~,c
<br />~ railings can be reduced by use of nitrogen-fixing native plant species such as ,, ',;
<br />I~
<br />;Indian ricegrass. Research has produced an acid and hormone treatment for ' ',.
<br />jincreasing.the naturally low germination rate of Indian ricegrass seeds. Addi- ~~ '~
<br />tional species of nitrogen-fixing native plants are being sought.
<br /> j : .,
<br />6, Growth of vegetation on saline tailings can be enhanced by percola- ~ ~
<br />tion leaching of salts, seedbed preparation using deep furrows, solar orienta- i'
<br />fon of mounded tailings, and the addition of sulfur in various forms.
<br />7. Microvegetative growth can be achieved-on tailings and offers promise ~ !
<br />ever macroscopic forms on tailings in and regions, but the algae, lichens, ~
<br />and
<br />mosses are as subject to salinity stresses as the larger plant species. ;
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