'Unsafe': Canterbury school turns off water amid nitrate spike

A school campus in Canterbury has been forced to turn off its main water supply after a well on site became contaminated by nitrates, documents obtained by 1News show.

The satellite campus at Lagmhor, part of Ashburton Borough School, has been trucking in a temporary water supply from elsewhere for the last year and a half.

School officials were sent a warning of unsafe water in February 2025.

The maximum allowed value or MAV is 11.3 milligrams of Nitrate-N to a litre of water. The school supply peaked at 11.5 mg/L.

Exclusive: New impacts of Canterbury’s 'nitrate emergency' revealed - Watch on TVNZ+

Nitrates are colourless, odourless and tasteless in water. If consumed at certain levels, they can lead to blue baby syndrome – conditions causing blueness of the skin due to low blood oxygen levels – in infants under six months.

The science was hotly debated, with arguments ongoing about whether they may also increase risk of colorectal cancer.

Debate was also swirling around exactly how they spread into groundwater, but farming activity was a major contributor, according to Canterbury University associate professor Tim Chambers.

He said nitrogen fertilisers were a key ingredient for plant growth.

"Livestock also eat the grass and anything they don't need, they excrete which also leeches down into the groundwater and washes away into streams," he said.

Documents obtained from the Ministry of Education through the Official Information Act have revealed just how deep the problem goes in Canterbury.

Emails show officials at the Ministry spent months considering the best fix for the school and ultimately decided to drill down further, in search of cleaner water.

The chief advisor to the Ministry’s water services team supported the move, with some caveats.

"We understand that deeper aquifers are likely to have lower Nitrate-N levels," they said in one email, before issuing a warning.

"However there is evidence of a steady increase in Nitrate-N levels at all aquifer levels."

With the original contaminated well at the school only going down 29 metres, the Ministry opted to drill a new bore around four times deeper.

A local drilling company went down to 119.5 metres in April 2026, reaching the third aquifer.

But when a test was carried out on the fresh supply, the water still carried an elevated level of Nitrate-N.

Test results obtained through the OIA show it returned a reading of 3.86mg/L, around a third of the maximum allowed value.

While it was within the legal limit, the result was alarming to Chambers.

"It's concerning that we have to go 120 metres deep to try and get access to water that would just comply with the drinking water standards," he said.

"There's a lot of people around the country, and particularly in Canterbury, that can't afford to drill a 120-metre well to try and get access to drinking water."

The school board stressed that the health, safety and wellbeing of students and staff had been its "highest priority" throughout the incident.

It would not be interviewed for the story but said in a statement that it had been working closely with the Ministry of Education on a fix.

"Safe potable drinking water has been provided to the Lagmhor School community throughout," it said.

The ministry said design work had been completed for a permanent treatment and storage upgrade to the school’s water supply system.

Water had been brought in from elsewhere, with a tank onsite for children in the meantime.

"Tenders are being sought to complete the work, which is expected to be completed within the next few months," a spokesperson for the ministry said.

The ministry also stressed that the nitrate concentration in the new supply was below New Zealand’s current Maximum Acceptable Value.

"Nitrate concentrations in water from the new bore meet the requirements of the drinking water standards."

Regulator Environment Canterbury (ECan) has also found high results while testing other Canterbury wells in recent years.

ECan water and land science manager Dr Elaine Moriarty said the council had been tracking the 10-year trend through groundwater surveys.

"The latest report shows an increasing trend of nitrate concentrations in 62% of the wells we test," she said.

The scene was a depressing one for local freshwater advocate Peter Trolove.

Trolove, an angler and retired vet, argued the situation at the school campus was a "case study" that could be replicated in many other areas across the region.

"This is the sharp edge of Canterbury's nitrate emergency," he said.

"I don't think it's the New Zealand that my grandparents' father and deceased brothers fought for in the world wars, I think it stinks."

Moriarty said ECan "recognises that nitrate is an issue in the region", and had a "drinking water action plan in place".

"It has taken many decades for nitrate concentrations to get to where they are today," she said.

"Depending on the soil type, aquifer parameters, and land use improvements, it can take some time before nitrate concentrations fall or stabilise – especially in deeper groundwater."