TABLE 1: Risks to dams resulting from mining activities

Risk Mechanisms Management
Mine subsidence from underground mining Ground movements cause damage to dam and possible dam failure: Cracking; Instability; Piping; Loss of confinement; Movement on geological structures; Loss of freeboard; Loss of flood capacity; Components (such as gates and conduits) fail Minimise ground movements by varying mine layouts, and by keeping a barrier between mining and dam; Dam surveillance
Blast, mainly from open cut mining Mine blast vibrations cause damage to dam and possible dam failure: Cracking; Instability; Piping; Loss of confinement; Liquefaction Manage blasts to limit vibrations by varying blasting practices, and by keeping a barrier between mining and dam; Dam surveillance
Mine workings (usually open cut, but may include portals to underground workings) downstream of dam Dam failure causes inundation of pit occupied by mine workers. Factors include: Short warning times; Pit wall failure destabilises dam Adequate pit wall design; Dam surveillance; Pit wall surveillance; Subsidence monitoring; Blast monitoring
Loss of storage resulting from mining activities Mining results in flow path between reservoir and mine workings Maintain barrier between reservoir and mine workings — in both horizontal and vertical directions; Understand hydrogeology of mine; Piezometric monitoring; Inspection of mine workings — identify seepage into mine; Mine water balance; Water source fingerprinting