Hundreds of small fish were killed and some eels had skin peeling from their faces and bodies after an acid spill near Ahuriri Estuary last month, Napier City Council says.
In an Official Information Act response to Hawke's Bay Today, the council revealed its staff's assessments of the impact on wildlife of the 1000-litre hydrochloric acid spill at Galvanising Hawke's Bay.
But Galvanising Hawke's Bay operations manager Stuart Easton has hit back, saying the council's assessment that aquatic life was harmed or killed as a result of the acid spill was "100 per cent rubbish".
On Friday February 5, the public were advised to stay out of the water at Ahuriri Estuary after 1000 litres of hydrochloric acid was spilled in the Thames St area.
Four fire trucks, a HazMat unit and support vehicles attended the scene, while Thames St was closed and properties evacuated.
More than 40,000 litres of "acid-contaminated" water was extracted from the upstream side of the spill gate in the waterway using vacuum trucks.
In its response to the Hawke's Bay Today's request for more information about the effect of the spill, the council said hundreds of small fish, dozens of elvers, and several adolescent and adult eels were killed.
"Some eels had the skin peeling from their faces and bodies," a council spokesperson said.
They said the fatalities were mainly due to the "suddenly decreased pH, as fish gills and the respiratory systems are not designed for this level of acid".
A group of pied stilts were seen trying to eat the dying fish, but observation did not discover any harm to birds related to the acid spill event, the spokesperson said.
"Further observation after the clean-up showed normal bird activity on the mudflats on the weekend following the incident."
Easton said firefighters at the scene had measured the pH in the water on the Friday of the spill and it was pH7, the chemical measure for pure water.
He claimed a firefighter had also told him that none of the spill had entered the creek near to the business, or the estuary.
"This [the spill] was 35 metres away from a drain. If any had got to it, we are talking drops here, not buckets."
Easton said hydrochloric acid was a "friendly" acid, used to regulate the pH levels of things like swimming pools, and a spill of it would be nowhere near as destructive as a sulphuric acid spill.
"This has just been blown out of proportion."
He said did not want to comment on what the company would do if the council sought to prosecute, fine, or take another form of legal action against Galvanising Hawke's Bay.
Easton then directed Hawke's Bay Today to Peter O'Donnell of Safety and Environmental Services Ltd and a WorkSafe approved compliance certifier.
O'Donnell said of the acid spill that the natural pH of the sea water is usually slightly alkaline between 7.5 to 8.4 and "if some hydrochloric acid did get in, understanding that none did, that would be quickly neutralised by the sea water".
"The pH would have to be right down below 3.5 to cause severe damage."
Asked what stage the investigation was at, if any charges had been laid against Galvanising Hawke's Bay and asked to respond to Easton's comments, a council spokesperson said NCC would not be making any further comment.