Mana whenua today made their case to independent commissioners against a controversial dump proposed for the Dome Valley, north of Auckland.
Waste Management has sought resource consent for the 60 hectare dump 5km from Warkworth, saying it is needed to cater for Auckland's growth.
But the plans have been vehemently opposed by iwi and community groups.
The site is next to the Kaipara and Hōteo rivers, sparking concerns the waterways which run into Kaipara Harbour would be polluted.
In today's hearing session, Ngāti Manuhiri chairman Mook Hohneck told the commissioners he understood the need for more landfills, but Dome Valley was not the right place.
The iwi owed it to future generations to stand up against the application, he said.
"Would our mokopuna ever forgive us, would the Kaipara [Harbour] ever forgive us for putting that paru into the source of the awa, [when it ends] up down there.
"[If] we paru the whenua, then we paru the wai at the source, it ends up in the Kaipara with our whanaungatanga. In 50 years time, those mokopuna down there [will be] saying, 'we wouldn't have this if it wasn't for Ngāti Manuhiri'."
Hohneck was concerned the dump would leak toxic chemicals into waterways.
While Waste Management said the tip had a lining system made up of multiple linings that would last 750 years, Hohneck took issue that the company could not promise no chemicals would spill.
"If we agree with it and in 50 years time our grand-mokopuna are running around and it does leak, who do you think gets to wear the burden?" Hohneck said.
"Ngāti Manuhiri does because it's in our area."
He said Waste Management should underwrite that the tip would not spill toxic waste if it was confident it posed no environmental risk.
He said the iwi would not go down without a fight.
"We are not going to be the victims of something that allows the pollution to go down our awa, down our beautiful river and down into Kaipara, impacting all our people down there.
"We're going to fight, because at least if we fight - whether we win or lose - at least we've stood up for what those tīpuna up there have told us to."
Te Aroha Pa Marae chair Te Atarangi Edmonds said the dump should be declined to protect the already beleaguered Kaipara Harbour.
She said kaimoana collected from the harbour was a dietary staple for local Māori 50 years ago, and water was consumed straight from waterways from around the area.
But the once plentiful food source was now largely lifeless, she said.
"Our awa has become contaminated, it smells, the water does not flow like it used to. We know it's because of run-off from farms and silt build-up."
She said the connection to the waterways goes deeper than being a food source: as kaitiaki, water is sacred to Māori.
"It's the tapu-ness of what it really means to us as Māori. I can best describe it as, in this instance, when we ask, 'ko wai koe?' we are asking, 'who are you?'
"The real meaning of what we are asking is, 'of whose water are you'".
Alan Riwaka, chief executive Te Rūnanga o Ngāti Whātua, was due to speak at the hearing the following day.
He believed the focus needed to be on more sustainable ways of disposing of waste instead of rubbish dumps.
"We can't continue the sorts of things we're doing to Papatūānuku. Imagine putting that on your mother and creating these sorts of landfills and toxic dumps. It's not acceptable in this day and age.
"We should be focusing on the alternatives, like waste-to-energy [and] 100 percent recycling.
"We shouldn't be saddling our young people coming through with these outdated technologies."
The hearing is set to continue through to mid-December, and a decision is not expected until 2021.