1986-12-08_GENERAL DOCUMENTS - M1977493 (2)

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18 of a fine water spray, described earlier, provides another technique which may be effective for controlling excess acidity. Tailings samples from several locations would not support vegetation without neutralization. Among these were uranium tailings from Wyoming and Colorado which had respective pH values of 2.3 and 4.5. Addition of 70 and 7 pounds of lime per acre, respectively, added to the top 2 inches of tailings raised the pH to a level high enough to sustain plant life. The tailings pile at the site of the former Vitro Minerals & Chemical Co. , Salt Lake City, Utah, contains both acidic uranium tailings (pH 3.6) and basic vanadium tailings (pH 8.5). These were mixed in the laboratory in equal portions to produce a material of pH 6.3 in which seeds readily germinated. Fertilization, however, was necessary to sustain adequate plant growth. Altering the Structure and Organic Composition of Tailings As previously noted, fine mineral wastes lack nutrients, humus, and micro bial populations all of which militate against the growth of vegetation. They may also lack the proper surface structure for air and water access and resist ance to being blown or washed away. Coarse grains and mineral aggregates are of importance on the surface of beach and pond areas of tailings accumulations because they resist movement by wind and water. Coarse grains and aggregates are of even greater benefit to stability,on the sloping dikes of the tailings ponds. Fertile soil in which vegetation grows most abundantly, unlike mill tailings, usually contains a small but important percentage of organic matter and micro-organisms. Plants can be grown well in pure sand cultures to which have been added a proper balance of all the necessary mineral compounds needE� by the plant, but if a little appropriate organic matter, such as leaf mold, is added, the plants grow much better. To prepare synthetic soils from barren tailings, research was conducted using additions of chemicals, sewage sludge, and compost. Structural and Organic Modifications of Tailings Several methods were tried for increasing particle aggregation of tail- ings to provide better root environment and soil aeration, thereby improving vegetative growth. Effective pelletizing and agglomerating procedures were developed. One of these procedures consisted of pelletizing tailings to minus-8-plus-35-mesh size with 2.5 percent asphalt, hardening the pellets by baking at 250° C, and spreading the pellets over the surface of the tailings to a depth of 1/2 inch, or mixing the pellets with an equal quantity of tail- ings to form a 1-inch-deep covering over normal tailings. A similar pellet was prepared, without the baking step, by pelletizing with 3 to 4 percent Peneprime (a commercial asphaltic bitumen product cut with white kerosine) or with 1 to 2 percent Coherex. Another procedure not requiring pelletization encompassed (1) seeding, (2) watering, (3) raking the wet tailings to form small-size agglomerates , and (4) spraying the agglomerates with Coherex and/or Soil Gard to preserve the pelletized form. Plant growth was improved in all instances where a granular, soillike texture was achieved by these methods. Additionally, two types of municipal wastes were tested as additives to x tailings. One was a commercial compost made from municipal refuse , and the