Reclaiming waste rock piles at Bingham Canyon Mine

Abstract

More than 115 years of mining at the Bingham Canyon Mine has produced over 3 billion tonnes of ore bearing copper, gold, silver and molybdenum and over 6 billion tonnes of mine overburden that cover over 20 km2 of land adjacent to the major metropolitan area of Salt Lake City, Utah, USA. The waste rock piles were constructed initially by train and railcar haulage in the early 1900s. Waste rock haulage fully transitioned to diesel off-road mining haul trucks by the 1980s. The waste rock piles are very tall and in places approach 520 m of total elevation gain, and until recently, some angle of repose slopes had approached a continuous slope distance of approximately 550 m. Reclaiming these historic waste rock piles presents unique challenges to the operation due to the physical constraints presented by the toe and crest of the piles at Bingham Canyon Mine. This paper discusses the design constraints for grading the waste rock pile slopes to the standard industry design criteria of 3H:1V and the adaptation of site-specific grading of inter-bench slopes, ranging from 2.75H:1V to 2.37H:1V. This paper also discusses the processes undertaken to evaluate viable methodologies for blending and applying the cap and cover to support revegetation, manage erosion, and ultimately minimise acid rock drainage. Lessons learned from the field trials and implementation are included.