Hastings District Council says a power outage was behind a sewerage manhole overflow earlier this month.
A council spokeswoman said the overflow of waste at Cooper St in Havelock North on August 6 was caused by the power cut that happened during the large storm.
"The pumps did not fail or break down, but they were affected as they run on power."
The council acknowledged that it had additional storage and back-up generators at pump stations but said the magnitude of the power cut suffered on August 6 meant some overflows were unavoidable.
"It is not designed and nor can it cope with the extensive power cuts, such as what we suffered when snow toppled a vast number of poles that day."
The council sent two mobile generators to the problem sites but said that, due to the length of the power outage, back-up systems were not able to cope.
When asked if the council had found out why it took so long to respond to calls from resident Andrew McDonald, the council said it was still looking into what happened.
Mr McDonald said the council had since spoken to him about a lack of response to his phone calls but did not tell him, nor his wife, Lynda, what actually went wrong.
"It was all very well they said sorry, but we still wanted to know what actually happened."
He said he was concerned by the low level of action and hated to think what would happen if there was a "proper" natural disaster.
"I just think we need answers and the council needs to get in to gear so things like this do not happen again."
The council said that the sewerage system met industry standards and reiterated that there was no link between the gastric outbreak and the overflow on Cooper St.
"There is no opportunity for the overflow to get into the water supply in that area," the council spokeswoman said.