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Staff at BP petrol terminals around the country have undergone extra training to ensure an incident where petrol was contaminated with water at a terminal in Dunedin last month is not repeated.
This comes as an investigation confirmed the contamination happened during ''routine pipeline testing'' on November 2 at the industry terminal in Dunedin, which is owned by BP and operated by New Zealand Oil Services Ltd.
As a result of the contamination, about 30 cars encountered engine problems. They had been filled up with 91-octane petrol at three BP sites, two in Dunedin and one in Oamaru, and Mobil Northgate in Cumberland St.
BP communications and external affairs manager Jonty Mills said an investigation into the contamination found it occurred when staff were undertaking ''routine integrity pressure testing of a pipeline'' using water. He said the test was done once every five years.
''It is important to note that water is used as a safety precaution, due to the nature of pressure-testing procedures.
''It's a normal procedure. It's just that there were some deficiencies in the process around doing it,'' Mr Mills said.
Since the incident, operational and management staff from around New Zealand had attended workshops in Wellington where the incident and the proper way of pressure testing were discussed.
Mr Mills would not reveal the amount BP had spent repairing damaged engines, saying it was ''commercially sensitive'' and the claims process was continuing.