There have been a whopping 167 consent breaches, incidents/failures, and unconsented activities at the troubled Transmission Gully site.
The revelations are the latest blow to the billion-dollar lower North Island road, and come despite the project receiving a top gong at the annual International Erosion Control Association Environmental Excellence Awards in 2018.
Greater Wellington Regional Council (GWRC) has resorted to prosecution in one case, laying charges against the builder of the 27km motorway for earthworks offences affecting both Duck and Cannons Creeks.
One expert says the number of incidents reported is astonishing and suggest contractors are not taking the environment seriously.
The road is being built through a public-private partnership, the Wellington Gateway Partnership (WGP), with CPB Contractors and HEB Construction sub-contracted to carry out the design and construction.
GWRC has taken the most compliance and enforcement action against CPB HEB JV relating to work on Transmission Gully, Willowbank Quarry and Porirua Links Rd.
The builder has been issued with 21 infringement notices with fines totalling $15,750, as well as 23 formal warnings and 16 advice letters.
The offences include sediment discharges into local streams, unapproved works, and slips.
NZTA said it has supported CPB HEB JV with additional training for staff, attendance at an environmental compliance workshop and an increased on-site presence.
Additional specialist resources have also been recently contracted to assist with monitoring work and improve environmental compliance across the site, project delivery senior manager Andrew Thackwray said.
"Waka Kotahi is committed to acting in an environmentally responsible manner and protecting and enhancing the environment."
Thackwray said many of the incidents have been investigated.
"Where a discharge has occurred, an ecologist has inspected the site to determine the effect on the watercourse. In many of these incidents, it has been found there to be no environmental effect."
CPB declined to comment and HEB said it was contractually prohibited from commenting, referring any media queries to NZTA.
Transmission Gully has been plagued by delays and was last month handed a $14m lifeline from NZTA to reflect the cost of the Covid-19 lockdown. A final cost is still being negotiated.
This came after NZTA bailed out the contractor to the tune of $190m in a settlement over delays caused by the 2016 Kaikoura earthquake, and flooding around the same time.
Massey University resource and environmental planning senior lecturer Dr Jeff McNeill said it was clear the breaches and incidents were persistent and long-term.
"It suggests they're not taking the environment particularly seriously.
"I'm certainly very surprised and a bit astounded that there are just so many that have been going on for so long."
The regulatory records were released to the Herald under the Local Government Official Information and Meetings Act and cover the time period between the end of 2014 to the beginning of this year.
The records come from GWRC audits and self-reporting by CPB HEB JV, which meant in some cases the builder could intervene before there was an environmental impact.
But some of the incidents did involve a sediment discharge which is where fine silt, soil or clay is exposed and washed into waterways.
A 2019 survey of Te Awarua-o-Porirua Harbour showed sedimentation rates have more than doubled in the last five years.
GWRC marine and freshwater team leader Dr Megan Oliver said at the time sediment was accumulating in the deep basins of the harbour, making them increasingly muddy and unsuitable habitat for a range of species.
"This is a bigger issue in the Pauatahanui arm and is driven by factors such as urban development, motorway construction, forestry harvest, run-off from rural pasture and erosion of stream banks.
"We are losing the remaining seagrass meadows, important as habitat for fish and invertebrates, and in turn, the rich biodiversity our estuaries are so highly valued for."
McNeill said good engineering and early planning should prevent discharges from sites such as Transmission Gully.
Under the Resource Management Act infringement fines for such discharges are $750.
McNeill said that was an incredibly small amount of money considering the tens of millions of dollars tied up in Transmission Gully.
"It's hardly worth a compliance officer's time to go out and write them, I would say, and I don't see them really changing attitudes and performance. Clearly it's not happening here."
Civil Contractors New Zealand chief executive Peter Silcock said over time contractors and clients have become more aware and concerned about environmental impacts and consent conditions.
"That's becoming more and more important as we move away from lowest cost contracts to contracts where people are looking to deliver social and environmental benefits as well as having good infrastructure built.
"All of our members are concerned about it and particularly the large ones because they know poor performance in that environmental area is actually going to jeopardise their ability to get future work."