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Staged Emergency Spillway Development – Design Considerations

Author: K.L Ainsley, B. Otis, E. Chong
Conference: 87th Annual Meeting of the International Commission on Large Dams
Date: June 9-14, 2019

ABSTRACT

Under most circumstances, spillway structures are required for the safe operation of a dam, helping to control the release of excess water within the impoundment to a location downstream. Where spillway facilities exist, it is essential that they are capable of operating throughout their design life and within prescribed regulatory requirements. This condition becomes more challenging when an emergency spillway needs to be incorporated into the design of a tailings storage facility (TSF). TSFs are typically designed for the final arrangement anticipated at mine closure. In order to reduce mine operating capital costs, TSFs are often constructed in staged lifts as dictated by tailings production estimates. Consideration for the spillway is required with each lift. Several factors influence the dam and spillway geometry including supernatant pond volumes, climatic conditions, tailings production rates, volumetrics of the impoundment, spillway location, geotechnical considerations, mine closure criteria. This paper will explore the key considerations for the development of a TSF emergency spillway. The spillway development at the Phu Kham Copper-Gold Operation (operated by Phu Bia Mining Limited) located in the Lao People’s Democratic Republic will be used to illustrate these considerations.

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