Claims of a leak at Swakop Uranium's Husab mine's tailings storage facility two months ago were confirmed by an investigation, the company told The Namibian on Friday.
Swakop Uranium's vice president for human resources and business support Percy McCallum said this when responding to follow-up enquiries by The Namibian.
The enquiry came after a photo which was posted on social media showed the tailings dam leaking, thereby arousing concerns that this was contaminating the scarce underground water.
The tailings facility is where the waste from heavy and radioactive metals washed with sulphuric acid is stored, and fears were that a leak could pose a major environmental threat to the groundwater supply as those metals could increase levels of radon gas which permeates into the groundwater.
When brought to the attention of McCallum then, he said the mine was investigating the claims. The investigation was done by the department of environmental affairs, the national radiation protection authority in the Ministry Agriculture, Water and Forestry, and an external environmental consultancy.
"The pumps at some of the lined seepage collection ponds partially failed, and with the continuous inflow of the seepage water, it resulted in the lined seepage ponds overflowing onto the unlined surroundings.
"It should be noted that the spillage took place in a small localised area, still within the perimeter of the tailings storage facility fence, which is not accessible to the public or animals. The tailings dam, including the wall of the dam itself, has no leakages, and operates as per normal practice," read a statement on the findings.
McCallum explained that the tailings storage facility is part of the processing plant and has a number of components, in particular the tailings dam, return water ponds, decant water return systems and seepage collection points and ponds designed to detect seepage and to protect the tailings dam walls.
He said the tailings dam has a double-lined impermeable membrane which contains treated slurry from the processing plant. The bulk of the water from the slurry is returned via the decant system to optimise water recovery.
Due to commissioning activities at the tailings storage facility initially, higher seepage rates are expected as per design, which is subsequently drained into lined seepage collection ponds, from where it is pumped back to the processing plant for re-use purposes to save water.
"The inspections confirmed that the spillage incidents were directly caused by the pump failures at some of the seepage ponds," said McCallum.
He said when the external regulators examined the area, there were no longer any overflows of the seepage ponds as corrective action had already been taken to repair the pumps timeously, and additional mechanical pumps were used to pump the water back over the wall into the tailings dam.
McCullum said water analysis is being done by the mine, and the ministry also took samples for verification purposes. The company also continues to frequently monitor the tailings storage facility and surrounding boreholes.
"Rehabilitation measures were taken by the company to neutralise the sand patches where the spills occurred, and subsequent rehabilitation of the areas started, and is continuing. The company also reviewed reasons for the pump failures, and has ordered new pumps," he added.
Namibia Uranium Association president Hilifa Mbako said the association concurred with the findings of the regulators, and thanked Swakop Uranium for having taken immediate action when the spillages were detected.