Heritage Cases

The original design intent was to use the FRD for short term surface disposal and then backfill the mine pits with this material once mining is complete. Due to ongoing underground mining operations, the backfilling options are no longer feasible. It is the intention of De Beers to continue depositing tailings residue on the existing FRD. In order to provide sufficient capacity for the LoM, the capacity of the FRD needs to be increased by raising the height of the south wall by approximately 2.5 m on average, which will: • meet volumetric requirements for tailings disposal; • maintain the required freeboard (800 mm above the maximum predicted flood level); and • ensure the stability of the south FRD wall. The FRD footprint will increase by approximately 2.4 ha. The south-west portion of the south wall (approximately 1 500 m) will be raised on the downstream side in order to gain the required height, with a 5 m wide crest). This is the lowest portion of the FRD and additional stability is required. The south-east portion of the south wall (approximately 1000 m) will be raised on the upstream side. The FRD wall will be constructed with tailings material with a calcrete armour layer for protection. The calcrete will be obtained from a new borrow pit within the mining right area. The wall will be constructed in phases to allow for sufficient construction time and to ensure that operational aspects are not compromised (e.g. freeboard requirements). Penstock outlet pipes used to drain stormwater from the FRD will be extended as required. Stormwater decanted from the penstocks to a new solution trench (1.5 m deep) at the toe of the wall will drain to an abandoned borrow pit to the south of the FRD for evaporation. Material excavated from the solution trench will be used to form a berm preventing clean stormwater from entering the trench. No new access roads and ramps will be required for construction. A 715 m portion of the existing road will be covered by the downstream wall construction and this section of road will be realigned to the south. Approximately 900 m of fencing south of the FRD will be moved to the south. The FRD is within the Kimberley Mine mining right area. The footprint of the wall will expand to the south of the existing FRD wall where downstream construction will take place (approximately 1 500 m). The new footprint of the wall will extend beyond the mining right area (but within De Beers’ property). A portion of land which is currently derelict will be transformed once it is occupied by the wall.