When asked if this measure related to the contamination's potential cause, Mr Wilson said not that he was aware of.
Regional council candidate Neil Kirton has called for a review of the council structure, saying the investigation was a "desperate attempt to stave off any finger pointing" at its consenting and compliance processes.
The investigation had "all the hallmarks of butt covering" for the council's failure to adequately monitor resource consents.
Mr Kirton, a former regional councillor, said his concern over a number of years had been the "soft hand" approach of the council with compliance of local authority consents - he cited the Central Hawkes' Bay wastewater, Napier City Council stormwater, and discharges into the Wairoa River.
Despite having all the latest risk-assessment and management-reporting tools, the most obvious risks have been ignored, he said, adding the regional council had failed to invest in critical monitoring to keep the community safe.
Mr Wilson said as the council's investigation, and the government's inquiry, continued he was sure "everyone's processes will be under scrutiny, and we welcome that."