Ensuring the stability of a large earth embankment that holds a large volume of water or slurry behind it is always a very challenging design and operation issue. Failure of such a structure could endanger public safety and could have serious environmental consequences. A mining company successfully mined under a refuse disposal facility that had a 61-m (200-ft) high embankment holding about 7 million m3 (9 million cu yd) of slurry and solid material. The disposal facility was above four consecutive longwall panels. To ensure the safety of this facility during and after mining these panels and to minimize the interruption to the longwall mining operations, a comprehensive subsidence simulation study was conducted. Based on the findings from subsidence studies, a relatively small support area was left in the longwall panel directly beneath the embankment. The performance of the support area was monitored and assessed during the mining of these longwall panels and continues to be monitored. The refuse disposal facility has shown no sign of problems and is continuing its intended service after being mined nearly six years ago.
