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7 <br />Noticeable during the 1969 and subsequent inspections was that considerable <br />breakage of the surface crusts was caused by people walking on and digging <br />into the taflfngs. The 1970 inspection showed that during the year, an addi- <br />tional disruption of about 20 percent had occurred, mainly in those areas that <br />were broken the previous year. The 1972 inspection indicated that a total of <br />about 40 percent of the dike showed disruption, but the crust on the pond area <br />appeared unbroken. Little difference was noted in the effectiveness of the two <br />chemicals tested, whether on acidic or basic material. The prime reason for <br />the disruptions was physical and unrelated to the stabilizing chemical used, <br />A preliminary conclusion is that chemical stabilization can be effective for <br />an indeterminate time ff the proper preparation of the site is accomplished <br />prior to applicatfon of the chemicals and maintenance is done each year, <br />Vegetative Stabilization <br />Consideration of esthetics and renewability generally favor use of vege- <br />tative stabilization. However, the successful initiation attd perpetuation of <br />vegetation on fine wastes involves ameliorating a number of adverse factors. <br />' Mill wastes usually (1) are deficient in plant .nutrients, (2) contain exces- <br />sive salts and heavy metal phytotoxicants, (3) consist of unconsolidated sands <br />that, when windblown, destroy young plants by sandblasting and/or burial, and <br />(4) lack normal microbial populations. Other less easily defined problems <br />also complicate vegetative procedures. The sloping sides of waste piles. <br />receive greatly varying amounts of solar radiation depending on direction of <br />exposure. Studies by Gates (3) have indicated that, while the sun is shining, <br />j of under high temperature conditions, photosynthesis may almost stop. Further- <br />i more, most accumulations of mill tailings are light in color and may reflect <br />excessive radiation to plant surfaces, thus intensifying physiological <br />stresses, Other mineral wastes may be extremely dark in color and absorb <br />excessive heat which may inhibit germination or kill seedlings, For these <br />reasons, vegetation that may be effective on northern and eastern exposures <br />' may not be suitable for southern or western exposures. <br />Ideally, vegetative stabilization should produce a self-perpetuating <br />plant cover directly or foster entrapment and germination of native plant <br />seeds which will form a self-regenerating community. In the latter case, an <br />ecological succession would be established leading to a vegetative covering so <br />completely in harmony with the environment that irrigation or special care <br />would be unnecessary. If the area were not cropped or grazed, only a minimal <br />additional fertilization should be required because the essential nutrients <br />would be largely cycled in place. <br />z Research indicates that, other than the excessive acidity, basicity, or <br />' salinity, perhaps the greatest problem to be overcome in establishing vegeta- <br />lion is that of windblown sands. Several procedures are in use for preventing <br />`\ windblown sands from covering or cutting off-the growing plants, These <br />include water sprinklfng while the plants are growing, covering the tailings <br />with soil or country rock, hydroseeding, using excelsior-filled matting as a <br />cover directly over the tailings, and a combination chemical-vegetative gra- <br />ced f k '1 h d - <br />ii <br />,; fft, <br />i <br />+: <br />i, <br />~~ <br />j! <br />is <br />ure developed by the Bureau o Mines. Sarin ling, soi covering, y ro <br />seeding, and matting have all been proved on various types of wastes, and the <br />