TITLE:
Recycling Tailings Seepage Water for Diogo Heavy Minerals Mine Sustainability (Northern Senegal)
AUTHORS:
Mouhamat Seck, Serigne Faye, Mark Robertson, Michael Rose
KEYWORDS:
Mineral Sands, Groundwater Modelling, Dredge Pond, Grande Cote Operations, Fe Flow
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.10 No.1,
January
31,
2018
ABSTRACT: The sandy Quaternary and the deep Maastrichtian aquifers located in the
northern coastal zone of Senegal, from the locality of Kayar in the south to
Saint-Louis in the north, constitute the main sources of water supply for urban
and local needs as well as mining activities. The Quaternary aquifer that
provides the water required for the irrigation of local farmlands, hosts a significant
heavy mineral sands deposit currently being mined by the Grande
Cote Operations (GCO). As a result of variable rainfall and increased water
abstraction, this shallow aquifer has recorded a continuous water level decline
since 1970, with potential negative effects on both the social and economic
development of the region. The mining of heavy minerals (zircon, ilmenite,
leucoxene and rutile) at GCO is realised through conventional dredging techniques
that require large volumes of water (up to 60,000 m3/d). The water
pumped by the dredge to enable the extraction of the heavy minerals, infiltrates
into the shallow aquifer, runs-off into the dredge pond or evaporates.
The objective of this study is to evaluate a water balance that enables the provision
of a permanent water supply to the dredge pond, whilst minimising the
risk of flooding of the cropping depressions adjacent to the mine site or drying
out of the farming wells. The hydrodynamic model implemented for this
purpose was calibrated and tested during the first year of operation. The Root
Mean Squared Error (RMSE) obtained for the calibration is approximately
0.52 m. The predictions indicate a requirement for the system to recover part
of the tailings infiltration through dewatering boreholes. The quantity of recycled
water is estimated at 16,000 m3/d on average. The model simulations
show an additional water requirement, extracted from the deep Maastrichtian
aquifer, varying between 23,000 and 28,000 m3/d to achieve the optimum
pond water level.