1989-10-10_REVISION - M1988112 (4)

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Some of the controlling factors affecting the depositional • characteristics of the tailings were identified and kept as constant as possible during the study. These factors as they were controlled might not have been truly representative of site conditions but the study required that several factors be kept as constants. The bottom of the box was covered with a medium sand to a depth of about .85 inch. The bottom of the box was also kept flat with no grade to the discharge point of the drain sand. The grain size characteristics are presented in Appendix A. The box was set up as a closed environment for two reasons. The first being an attempt to control the atmospheric environment of the deposited tailings. The second reason was tm attempt to collect any cyanide which might have out-gassed to the atmosphere and pass it through a Sodium Hydroxide water bath. The tailings slurry used for the box was mixed in a column • ~ three inches in diameter by three feet in length. The column was filled to a height of thirty inches and the column was placed above the box. The bottom valve was opened and the tailings slurry was discharged into the box through a manifold with four spigots. Each deposition consisted of approximately 3 liters of tailings slurry deposited at a rate of about 4 liters per minute with an initial driving head of 6 feet. Each lift represented the total amount of slurry placed in the box for a specific day. Typically 2 or 3 depositions were made in any given day. The water which drained to the surface of the tailings was allowed to run off the tailings solids and discharge into the sand blanket. This collected water was drained and collected by means of drain valves at the base of the box. When the entire sand blanket was covered with railings the solution was allowed to form a small pond. The values of density and saturated moisture content (90) obtained are presented below on per lift and total deposit basis. C~ J