2004 – Closure and Decommissioning of the Namuk Tailings Dam, East Kalimantan

A Bodley, J Phillips and P Cesare

The PT Kelian Equatorial Mining (KEM) Gold Mine is located in the foothills of Central Kalimantan in Indonesia, only 3km south of the equator. Namuk Dam was completed in September 1991, to receive tailings from the gold mine that commenced commercial production in January 1992. Mining operations ceased in mid-2003.

Progressive closure of the mine has been underway since 2003, but processing of ore stockpiles will continue to the end of 2004.KEM and the local Government formed a Mine Closure Steering Committee, supported by four Working Groups to provide assistance and guidance to KEM in achieving responsible closure of the mine.

Engineering aspects of the Namuk Dam closure included flattening of the downstream slope to withstand overtopping in the event that the spillways should fail or be blocked for whatever reason. The design also required large rock to be placed as an apron over the tailings upstream of the dam as a security precaution against potential sabotage. This is intended to deter illegal mining of tailings, which could potentially initiate breach of the dam, and to protect the dam from malicious damage.

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