Yesterday council chairman Rex Graham said if they had not done their job properly "then we would definitely apologise to the community".
"We're charged with these roles and we take it incredibly seriously, and none of our staff want to fail," he said.
"They're all trying their best ... we need to look at our ways so the best is good enough."
Council group manager resource management Iain Maxwell said they accepted the inquiry's findings, and staff would be analysing the report to "see what might need to be worked on from our perspective".
LACK OF INVESTIGATION
One of the council's major failings was that it had not been sufficiently aware of aquifer and catchment contamination risks in the vicinity of Brookvale Rd.
This included HBRC not taking the opportunity in 2008 - when HDC applied for a water take - to assess, and manage aquifer contamination risks relating to the take from the bores, as would have been part of its functions under the RMA.
In the years following, HBRC also failed to identify aquifer contamination risks arising from the water extraction, "despite some clear indications of such risks".
As HBRC had the resource, and a "clear duty" to address aquifer contamination under the RMA, they failed to take effective steps to assess the real risks of this.
When asked why the council had not taken action in the years to 2016, Mr Maxwell said at the time of the 2008 consent process there was no evidence before HBRC to indicate there was a risk of the HDC bore drawing in surface water.
NON-SECURE BORES
Part of their failure in addressing the risk of contamination was leaving uncapped, disused, or "risky" bores in the vicinity of Brookvale Rd unchecked.
The inquiry accepted HBRC were not able to monitor all 7000 consented bores in their jurisdiction, and that it was "too difficult" to keep track of unconsented bores.
However given the number of such "risky" bores in the Brookvale Rd vicinity - where drinking water was extracted from an aquifer that was not confined - it would not have been "unduly burdensome" for the regional council to have assessed these bores.
Mr Maxwell said they were contacting "the thousands of bore owners throughout the region to ensure that bore security requirements were being met and unused or abandoned bores were recorded".
HEAVY RAINFALL
HBRC had also not identified the risk posed by heavy rainfall - especially given the bores' proximity to livestock. The inquiry also noted HBRC should have been aware of the pattern of heavy rainfall associated with contamination events.
"While it is speculative, the inquiry considers it is at least possible that an earlier identification by the regional council of heavy rainfall as a substantial risk factor may have led to a different outcome in August 2016," the report noted.
This could have led HBRC to discover faults in the bores meaning HBRC might have looked at its compliance with the "safe and serviceable" condition of the HDC's 2008 water permit - as they had done as a result of their 2016 investigation.
Other risks included HBRC having no process for monitoring livestock in the area - an "obvious form of contamination risk", and their inadequate knowledge of aquitards in the catchment area.
On these catchment risks, Mr Maxwell said council had a significant body of work to better understand the Heretaunga aquifer.
"The work that occurred as a result of this inquiry has assisted this."
CONSENT CONDITIONS
HBRC also failed to properly enforce a condition of the HDC's Brookvale bores water permit. Condition 21 concerned the bores' safe and serviceable state - a generic condition which should have been more specific, requiring proper bore protection.
The council also fell short in its compliance monitoring of the permits - which it had a statutory duty under the RMA to do.
The consent had implied HBRC would monitor the bores to ensure compliance with condition 21, however there was "undisputed evidence" that HBRC had not carried out any physical inspection of the bores, or otherwise monitored their status and serviceability.
Although HDC was required to comply with the consent's conditions, "ultimately adequate monitoring to ensure compliance was the regional council's responsibility".
Mr Maxwell said the regional council had completed their process of revising and updating their consenting procedures, forms and templates for implementing the NES regulations.
"HBRC is also adding more groundwater monitoring sites and reviewing the current monitoring network to ensure it is fit for purpose. We are also undertaking a regionwide review of our monitoring networks."
PAST TRANSGRESSIONS
The inquiry also pointed to previous incidents relating to bore contamination in late 2015 - noting HBRC's lack of any "meaningful or effective response" indicated a "substantial failure to grasp the changed contamination risk to the Te Mata aquifer at that time".
"It is striking that [HBRC] carried out an intensive and comprehensive investigation after the August 2016 outbreak, at a time when it perceived at least a possible changed risk landscape," the inquiry noted.
The first event was in October 2015, when Brookvale Bore 3 was contaminated. Aside from sending "some brief emails" to HDC, the regional council failed to follow this up, pursue investigations against Te Mata Mushrooms, or escalate the matter within their organisation.
Two months later HBRC did correctly speak with HDC about elevated E. coli readings in a test bore. However, the inquiry stated that by early 2016, there was a need for the two councils to undertake a "substantial and rigorous" investigation into aquifer and catchment matters.