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<br />adhesive type, was applied to the moistened tailings in amounts costing 1 cent
<br />or less per square yard: This stabilization procedure generally is best -
<br />applied in the fall of the year so as to achieve some growth before the onset
<br />of winter, thus allowing the root system to develop under a cover of snow and t
<br />with good moisture conditions.
<br />Field Tests S
<br />A combination system involving vegetation and an application of Coherex
<br />co stabilize the surface against sand blowing until the plant cover was able
<br />to, take over that function itself was developed from knowledge acquired from
<br />the Bureau laboratory and outdoor trials. That system was applied to a
<br />10-acre plot of Kennecott's McGill, Nev., tailings in mid-September of 1967,
<br />The McGill tailings are located in a climatically harsh site for vegetation.
<br />The growing season is short, the temperature range is wide, and precipitation
<br />is only 8.4 inches per year. Different proportions of western, pubescent,
<br />crested, intermediate, and tall wheatgrasses, Russian wild rye, Ladak and
<br />Ranger alfalfas, yellow sweet clover, winter wheat, and Siberian pea tree
<br />seeds were mixed and planted by drill seeder at a rate of about 15.5 pounds
<br />per acre or .37 seeds per square foot. Prilled urea and superphosphate fer-
<br />tilizers were added to the seeding mixture at a rate of about 45 pounds per
<br />acre each of P20s and nitrogen. The mixture was planted in furrows 10 inches
<br />apart, (This field test was conducted prior to discovering that nitrogen in
<br />this quantity tends tb inhibit legume germination,) A week after .the area was
<br />seeded, Coherex diluted with 4 parts of water was applied over the entire area
<br />Laboratory studies had indicated that approximately 0.25 gallon per square
<br />yard of diluted Coherex would satisfactorily stabilize McGill tailings. To
<br />corroborate these laboratory finds, 5, 2-1 /2, and Z-1 /2 acres were sprayed
<br />~:ith 0.25, 0.18, and 0.67 gallon per square yard, respectively.
<br />An accounting was kept of material and application costs associated with
<br />treatment of the 10-acre plot. During a year of observation, no appreciable
<br />differences were noted in the stabilization of plots treated with the differ-
<br />ent amounts of Coherex. This indicates that the preselected quantity of
<br />0.25 gallon per square yard of dilute Coherex solution could be reduced to
<br />0.18 gallon per square yard with a savings in cost. The estimated cost of
<br />$1,355 for the 10 acres could probably be reduced if larger acreages were
<br />treated or if proper equipment were available. Such a cost for the chemical-
<br />. Vegetative procedure compares favorably with that of chemical stabilization
<br />only, which cost $335 per acre in the Tuba City test. .
<br />Many violent windstorms have passed through the McGill area during the
<br />6 years since planting, without raising dust clouds from the stabilized plot.
<br />q' The Coherex satisfactorily maintained the surface until the vegetation grew
<br />r' and the chemically and vegetatively stabilized tailings now appear fully
<br />resistant to wind erosion. No irrigation was applied to the plot during the
<br />`~ 6 years, but the growth was excellent. The plot, as of September 1972, showed
<br />that a line of vegetative ecological succession had been established in that
<br />aPProximately 27 different plant species were on the area and growing well,
<br />11 of which were encroaching native species.
<br />The success of the combined chemical-vegetative stabilization procedure
<br />at McGill, Nev., prompted testing of that method in other Localities with
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