Her comments came on the eve of expected results from the ramped-up testing coming closer to being released.
New Institute of Environmental Science and Research (ESR) results released on Thursday evening to the Northern Advocate show the virus has not been detected in 18 Northland wastewater treatment plants analysed to date.
Ngāti Kahu is part of Te Kahu o Taonui, the Northland Iwi Chairs Forum, which this week called for the testing to be ramped up across the region.
At that stage, it was being done in five of Northland's 32 wastewater treatment plants (WWTP)s – Whangārei, Kerikeri, Kaitaia, Paihia and Rawene.
Testing is now happening at 28 of them.
In the Far North it is being at Ahipara, Awanui, Hāruru, Hihi, Houhora, Kaeo, Kaikohe, Kaitaia, Kawakawa, Kerikeri, Kohukohu, Opononi, Paihia, Rangiputa, Rawene, Russell, Taipā/East Coast, Whangaroa and Whatuwhiwhi.
In Whangārei is being done at Whangārei - (Kioreroa) with Oakura, Ruakākā, Tutukaka and Waipū soon to be added. Hikurangi, Portland, Ngunguru and Waiotira are not being tested.
In Kaipara testing is happening at Dargaville, Kaiwaka, Mangawhai and Maungaturoto.
No testing was done in Kaipara at the start of the week, in spite of it being immediately next door to Auckland - the current Delta community outbreak's epicentre.
Thursday night's ESR results for this week to date, show the virus has not been detected in 18 Northland wastewater treatment plants so far analysed - Ahipara, Awanui, Hāruru, Hihi, Houhora, Kaeo, Kaikohe, Kaitaia, Kawakawa, Kerikeri, Opononi, Paihia, Rangiputa, Rawene, Russell, Taipā, Whangārei and Whatuwhiwhi.
Herbert-Graves said the obvious influx of Auckland bach owners into Northland as New Zealand's national level 4 lockdown was put in place meant testing wastewater for the virus was critically important.
This became even more so with the large number of Auckland Delta outbreak close contacts that are in Northland.
Huhana Lyndon, Ngātiwai Trust Board chief executive, said Covid-19 wastewater testing helped provide reassurance around whether the virus was locally present.
Herbert-Graves said this was clearly borne out by Warkworth's positive Covid-19 wastewater test being followed by the discovery of a positive Covid-19 case in the town.
Lois Howe, Whangārei District Council (WDC) laboratory manager, said the council had been sending raw sewage from its Kioreroa plant twice weekly to Wellington for Covid-19 testing.
The plant serves about 70,000 people, roughly 70 per cent of Whangārei district.
Howe said Whangārei district WWTP Covid-19 testing was initially done only at this plant, because at first only bigger plants were being monitored.
The surveillance programme had now been expanded to sample raw sewage from reticulated sewage schemes in Whangārei's coastal settlements.
Howe said the ultra-sensitive test could detect the distinct RNA strands shed by people carrying the virus. The results were used to alert Government to the virus' presence in the community, even where cases had not been identified through individual medical tests.
WDC has been Covid-19 testing since early July. WDC's WWTPs are not being tested.
Covid-19 wastewater testing is set up by the Ministry of Health with the Institute of Environmental Science and Research (ESR) analysing surveillance samples.
