The Giroux Wash tailings impoundment at the Robinson Mine in Nevada receives a nominal 42,000 tons per day of milled, processed sulfide flotation tailings. The facility has a compacted earth starter embankment with the majority of embankment raise construction achieved via the centerline construction method using the coarse fraction of cycloned tailings slurry.
SRK consultants were instrumental in formulating and implementing new design initiatives following the commissioning of the facility in 1996. These initiatives were implemented to improve control of slurry deposition and supernatant reclaim due to operational start-up limitations associated with these two design elements. These initiatives included:
• A hydraulically raised cyclone system using a 30-inch diameter steel pipe located on the embankment crest with 4-inch hydro-cyclones at 25 foot centers. This system enables the pipeline to be elevated at an adequate height above the crest tailings surface to ensure sufficient height for centerline raising, which typically occurs during the summer and early fall. The cycloned overflow and total tailings are used to maintain a positive beach slope and drainage towards the barge operation channel for recycling of supernatant water.
• The barge operation channel is 150 feet wide, 15 to 20 feet deep, and clay lined. The depth and storage capacity of this facility allows the operator to maintain a water level in the channel to sustain the pump operation and limit the spread of the supernatant pond surface area onto the beached tailings. This eliminates ponding and results in rapid consolidation and decrease in the hydraulic conductivity of the beach tailings. Construction to extend the channel has also been appropriately phased. As a result, when the facility went into temporary closure in June 1999, the remaining supernatant pond inventory was fully evaporated by the end of August 1999.
Operation of the facility resumed in the fall of 2004 and continues today. Based on inspections and annual dam safety evaluations, the system continues to function as designed and permitted, highlighting the importance of all aspects of tailings impoundment drainage in the design process.
