Oxygen depletion caused fish kill at Newmont Ahafo Mine – EPA

An Environmental Protection Agency (EPA) report released has indicated that the fish kill at the Water Storage Facility (WSF) at the Newmont Ghana Gold limited Ahafo Mine was due to oxygen depletion and over population of the fish stock.

It said the fish kill was not as a result of elevated levels of sodium cyanide and or heavy metal contamination.

A copy of the report made available to the Ghana News Agency (GNA) at Kenyasi in the Asutifi District of the Brong Ahafo Region on Friday said “Based on the result of the analysis, it is evident that the fish kill was not as a result of elevation levels of sodium cyanide and or heavy metal contamination.

“However, it was as a result of oxygen depletion and over population of fish stock in the Water Storage Facility (WSF).”

The report was an investigation into Fish Mortality in the Water Storage Facility (WSF) at Newmont Ghana Gold Limited Ahafo Mine at Kenyasi.

The report said at the time of writing, results of metal analysis were yet to be received, and although those data were relevant to the study, they were not the source of the fish kill, adding “Their presence in the water will result in bio-accumulation in the fish muscles”.

It said the fact that the section of the water where the incident occurred had turned green in colour as in eutrophic water; it was likely that an increase in organic matter and nutrients in the water encouraged algal growth in the pond.

The report said this was confirmed by the dense population of algae present in the water and by the greenish colouration observed in the water.

These algae made a high demand on oxygen at night and early hours but generated oxygen at day time. It was possible that the increase in algal population and or decomposition of algae and other organic matter in the water resulted in a critical oxygen depletion which eventually led to the fish kill.

“This assertion is collaborated by the high BOD levels and the account of the community, which said that they saw the fishes coming up, meaning that the fishes were gasping for air,” the report added.

The EPA conducted the investigations based on a report by the Centre for Environmental Impact Analysis (CEIA) an environmental integrity and non-governmental organisation that 3,000 fishes that were discovered dead in a dam at the premises of the Mine on January 3, 2012 was as a result of cyanide spillage.