Tailings and Mine Waste Conference

Stabilization of a rock pile moving on a pre-sheared foundation at Questa, New Mexico Peterson, Tim; Dawson, Richard; Horton, Jay


In 2003 concerns were raised by both state regulators and the nearby town of Questa, about the potential mobility of the 300 metre high Goathill North rock pile at the Questa Molybdenum Mine, located in the Rocky Mountains of New Mexico. The 3.4 million m³ rock pile was constructed between 1969 and 1973, when foundation movements were initiated at the toe of the pile underlain by pre-sheared material that had been creeping for over 30 years. This paper outlines the extensive investigations and instrumentation needed to verify the movement mechanism and to develop a mitigation program acceptable to all stakeholders. The mitigation program was divided into four phases involving the placing of a rock under drain and toe buttressing prior to moving equipment onto the moving rock pile for regrading and construction of surface water control features. Considerable effort was made to balance over 760,000 m³ of cut and fill and ensure that the sequencing of material movement maintained stable and safe conditions. Integral to the mitigation, was a comprehensive instrumentation and monitoring program that continued for over a year after completion. [All papers were considered for technical and language appropriateness by the organizing committee.]

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