Council agreed to fund this partly through their current budget provisions of legal and consultancy, with the remainder to be funded from the surplus operating position for the 2015/16 financial year.
This however was not the total cost of the contamination incident. Group manager strategic development James Palmer said costs related to the Government Inquiry "remain a highly uncertain variable at this time".
Mr Palmer said with the inquiry set to begin before the end of next month, funds could be drawn from the Regional Disaster Reserve - as they fit within its criteria.
"This is clearly an event which could not have been anticipated by council staff in our budgeting and planning for the year," he said. "The costs as you have seen are significant, and substantial, and could not therefore be absorbed on an ongoing basis over the coming six months.
"In our view the regional disaster reserve is the most appropriate place to go in respect to meeting those costs."
Some of these some of these costs, particularly in regard to the investigation, could be recoverable if there was a successful prosecution, he said.
Group manager resource management Iain Maxwell said this could come through penalties imposed on one or a number of parties if a prosecution was undertaken.
"We would also be seeking to recover some of our costs," he said, "so we would make submissions around our costs and then ask the court to provide that some, or all of those costs, be returned to us by the party we are prosecuting."