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17 <br />' material, and (2) in "as deposited" tailings capped with a Iayer of sands over- <br />- lain by a stratum of slimes. Both plots were permitted to dry thoroughly, <br />then were watered once with sufficient salt-free water to force the "wetting <br />front" several feet into the underlying tails. Subsequently water was added <br />only when plants showed signs of wilting. Appreciably more profuse and <br />healthy plant growth was obtained in the stratified plots. Apparently the <br />sand layer hindered the migration of salts to the upper slime layer in which <br />most of the vegetative growth took place. Also, when tailings were piled in <br />long mounds (approximately 12 to 18 inches high) oriented in an east-west <br />direction, vegetative growth was manyfold greater on the northern slopes of <br />the mounds than on south-facing slopes where increased evaporation concen- <br />trated the soluble salts. <br />In this testing, similar to that of Baines and Singh (1), five mounds <br />were established with saline copper tailings from Rennecott Utah Copper Divi- <br />sion having a soil solution with an osmotic concentration of about 2.4 atmos-. <br />pheres. The mounded tailings were then planted in April with tall wheatgrass, <br />yellow sweet clover, and Ladak alfalfa in two rows each on north and south <br />slopes of the mounds and one on the top. These tests showed that plant germi- <br />nation and survival after 9 weeks was three times greater on the north slope <br />than on the south slope and that the topmost row of vegetation on the mounds <br />showed poorer growth than that on either slope. The tops of the mounds were <br />subject to more solar. radiation than even-the south slopes and plant growth <br />'• suffered commensurately. Samples were taken from the surface inch of the <br />mounds near the planted rows on the northern and southern exposure and leached <br />to determine soluble salt content 15 weeks after planting. The results showed <br />30 percent more salts on the south than on the north slopes. After 28 weeks, <br />[he survival rate of vegetation on the north slopes was 17 .times greater than <br />on the south slopes. These findings have.been substantiated by field studies <br />on acid coal mine wastes showing much better growth when planting in mounds. <br />In an attempt to reduce the rate at which the mounds erode, five differ- <br />ent chemical stabilizers were applied to newly erected and seeded ridges. <br />Results of these trials indicate that the chemicals do influence erosion rates, <br />and also the germination and survival of plants. Chemical stabilizers tested <br />included Coherex, Orzan A (ammonium ligninsulfonate), Rezosol, DCA-70, and a <br />cationic neoprene emulsion. After 28 weeks, seedling survival counts showed <br />that almost 40 percent more seedlings grew on the Coherex-treated plots than <br />on the control. In comparison, the cationic neoprene emulsion treatment sup- <br />ported only 50 percent as many seedlings as the control plot; Orzan A, 70 per- <br />cent; and Rezosol and DCA-70, 90 percent. Thus, Coherex appears to aid <br />seedling establishment and survival in saline waste. <br />Modification of Tailing pH <br />con- Both basic and acidic tailings present conditions adverse for plant <br />ow( growth. In some instances, both conditions are present in different parts of <br /> a single tailing accumulation. The acidity and basicity of tailings can be <br />mound- neutralized by adding Iime or limestone and sulfuric acid, respectively, but <br />rative handling problems arise and costs mount if large quantities are needed. <br /> Impervious crusts are sometimes formed•by t he neutralizing reaction. The use <br />