A "major response" by Napier City Council works maintenance crews had water back on five hours after a Unison drill burst a major water supply pipe on the edge of the CBD yesterday.
A Unison crew carrying out horizontal drilling under Station St, to lay high-speed cables, fractured the 150mm cement pipe just after 3pm - the pressure of the escaping water blasting to the surface, where it tore a large hole in the road, and trapped one of Unison's own trucks.
The broken pipe caused major flooding in the immediate area, cut water to the nearby Reading Cinema and Underground Bar and caused traffic disruption.
Napier City Council works assets development manager Johan Ehlers said the one fortunate aspect was that the pipe struck was not one of the 300mm fittings.
"That would have really gone," Mr Ehlers said.
While the broken section was removed and replaced and the road temporarily repaired, traffic disruptions are still expected to continue through the weekend while engineers make road checks.
"With that sort of pressure and amount of water, we are concerned there may have been some undermining of the road surface, so we need to check and assess that," Mr Ehlers said.
The Unison drilling programme has been halted while repairs and checks are being carried out.
Mr Ehlers said horizontal drilling, under road surfaces, saved a lot of trenching and was far less intrusive - but did have its drawbacks. "And we saw one of those."
He had some concerns about the practice and said while plans showing piping in proposed drill areas were made available to the drillers, "this happens now and then".
One of his concerns was that while a broken water pipe became immediately obvious, fracturing a stormwater or sewer pipe, which did not carry the same pressures, would not be detected straight away. "The operators would not be aware they had hit something," Mr Ehlers said.
Unison customer relations manager Danny Gough said a report into what happened was being prepared for the council.
"We will provide all the information we have about the incident as well as the processes and policies we go through when we go about this type of work."
He said the bottom line was to give the council a level of comfort that a similar situation would not happen again.
"We pride ourselves on not impacting on other services - we know what it is like when we have our cabling hit."
Unison's work in the immediate area was being finished off late yesterday.