An investigation into the construction of the Waimea Dam has found no evidence of impropriety or hasty, uninformed decision-making, says Tasman Mayor Tim King.
A report on the investigation, which was requested by a number of councillors earlier in the year, was received at a full Tasman District Council meeting on Thursday.
The investigation which looked at the appropriateness of the dam project was undertaken by PJ & Associates and overseen by the council's Audit and Risk Committee independent chair Graham Naylor.
Staff were interviewed and hundreds of documents and reports were reviewed during the investigation.
King says the dam project was always going to be challenging given its size, multi-benefit scope and the mixed ownership funding model.
It found the information provided to the Tasman District Council was generally robust and there was no evidence of bias by officers.
He said the report highlighted lessons that could be applied to future infrastructure projects, not just in Tasman.
The council had already implemented some of the recommendations in the report and were developing others.
Tasman District Council CEO Janine Dowding said she hoped the report would provide reassurance to those with concerns about the processes and decision-making related to the dam.
"I never had any doubt that staff had acted with integrity and this report should bring an end to the unpleasant allegations that have been directed toward staff and councillors.
"While the investigation does not remove the challenges of the project nor the risk of further cost over-runs, it should provide reassurance that decisions made have been well informed and appropriate."
Dowding said the findings and recommendations were appropriate and the council continued to work on its approach to risk and project management.