Cost of diesel clean-up in Christchurch tops $1m and still rising

A clean-up operation to prevent diesel seeping into Christchurch’s water supply has topped $1 million and there is no time frame for completion.

A stake accidentally driven into a fuel line supplying Christchurch Arena in Addington continues to impact on the city’s coffers as Venues Otautahi - a council-owned company - oversees remedial work around the site.

"We’re continuing to monitor and manage the situation. This is a long-term process," said Venues Otautahi chief executive Caroline Harvie-Teare.

The Star understands the project has already cost more than $1 million, though Harvie-Teare would not reveal the financial implications.

"The costs associated with the diesel leak recovery and remediation strategy is commercially sensitive and we are unable to release the information on that basis,” she said.

"All costs associated for remediation and ongoing monitoring are an operating expense of Venues Otautahi."

The leak was discovered in July 2018, when a diesel odour was detected in a stormwater retention basin near what was then Horncastle Arena.

Investigations revealed a fuel line had been nicked.

The pipe was fixed immediately, but it is believed it may have been leaking for several years, infiltrating soil in the area.

Vbase (now Venues Otautahi) launched the clean-up process in October 2018.

The following February, routine monitoring detected diesel in bore holes sunk to trace the fuel’s spread.

So far 54,000-litres of diesel have been extracted by contractor Petrotec Services Ltd from bores dotted around the area and three interception trenches.

"In the past few months, there has been a marked decline in the amount of diesel we’ve managed to recover from each of these trenches,” Harvie-Teare said.

"We believe the decline is due to having reached a point where the more easily accessible and mobile diesel has been recovered, with the remaining diesel becoming immobile or trapped in the soil.

"This is very good news and is consistent with our remedial strategy."

Harvie-Teare said there has been no trace of diesel in the drinking water supply; no residential properties have been affected to date, based on testing.

An October 2019 report by then Vbase general manager Chris Mintern said Addington’s drinking supply was drawn from a deep aquifer and these wells were located hundreds of metres from where the diesel was detected.