Shellfish warnings follow Collingwood sewage leak from previously unknown pipe
Signs were erected at Collingwood early last week, warning residents and visitors not to take shellfish along the coast as far as Parapara, due to an effluent discharge.
The estimated 500 cubic metres of primary treated effluent was released into the Burton Ale Creek due to the failure of a 100mm diameter pipe that was not known by council staff to exist. It was thought to have been used during construction of the sewerage plant, but its removal was overlooked upon the plant’s completion.
The leak was stopped shortly after it was noticed on 9 November.
Graham Caradus, TDC’s regulatory services co-ordinator, said the warning signs and the public notices in the paper were for areas that may have been contaminated, including any areas that the plume from the Aorere River may have passed over around the time of the incident.
“Given the relatively slow rate of leakage that occurred from the treatment plant, and the fact that it was material that had already received primary treatment, it could be that the risk was low, particularly when the dilution factors associated with the flow of the Aorere River and tidal movement in Golden Bay are factored in. However, from a public health perspective, it is better that the warning was given.”
The bivalve shellfish commonly taken in the area are all filter feeders, and can take in any bacteria or viruses in contaminated water and concentrate them in their gut. Typically, we eat the whole shellfish, including the gut, and potentially any harmful organisms that may have accumulated there. The cooking process for shellfish usually only opens the shell (occurring at about 44°C for mussels) and warms the flesh to begin coagulating the protein. This heat is usually insufficient to guarantee the destruction of organisms within the gut. The health warnings do not included fin fish, as they are eaten without the gut, and micro-organisms do not concentrate in their meat.
The shellfish ban will continue until further notice.
Gerard Hindmarsh
