Rehabilitation of a historic mine with sudden seepage

A mine in South Africa that has been closed for years suddenly developed downstream seepage from the underground. Preliminary investigations showed that it was potentially due to the partial collapse of portions of the board and pillar areas in the underground as well as changes to groundwater levels. There are complicating factors such as no access to the underground, a deep mining horizon and mine plans that are incomplete or unavailable. Current overall stability of the underground is also unknown. The risks to surface water receptors have been mitigated by temporary measures but a long-term permanent solution is the preference. This case study presents the investigations and modelling of the seepage as well as the preliminary plan for plugging the leak points using paste backfill, and the paste recipe development using old onsite dump materials.