Nitrate Dashboard and Information

Nitrates and nitrites are natural chemicals found in soil and water as part of the earth’s nitrogen cycle. They’re also present in some foods and in the human body, and nitrates are sometimes added to food as preservatives.

Under the Drinking water quality assurance rules we are required to test monthly for nitrate. Since the event began, we have been testing daily, and we are now comfortable with the levels. As a result, the frequency of testing will be reduced. We have also invested in nitrate probes at both the bore site and the treatment plant, allowing the team to detect any changes quickly and respond faster.

April

• 7.63mg/l at Coopers
• 7.93mg/l at East Gore WTP
• 1.15mg/l at Jacobstown

May

• 8.93mg/l at Coopers
• 8.24mg/l at East Gore WTP
• 0.90mg/l at Jacobstown

June

• 8.73mg/l at Coopers
• 9.2mg/l at East Gore WTP
• 1.02mg/l at Jacobstown

Never. This was the first occurrence.

At this stage we do not know Environment Southland is responsible for investigating environmental pollution, including what might be affecting groundwater. They are will keep us informed as they learn more.

Nitrates can only be removed from water using methods like reverse osmosis. This process works like a super-fine filter, pushing water through a special membrane that blocks nitrates and other contaminants. However, it's expensive to run because it uses a lot of electricity, wastes some water, and the filters need regular maintenance so while it’s great for household use, it’s not a practical long-term solution for treating a whole town’s water supply. . Building a reverse osmosis plant can cost millions of dollars, depending on the size and complexity of the system.

Water was pumped from the Mataura River, which has much lower nitrate levels, into a nearby unused well. This helped dilute the aquifer which we withdraw water from, bringing the nitrate concentration down to safer levels. Nitrate levels are now down to below 5 mg/L at the East Gore Water Treatment Plant highlighting the work done to lower the levels over the past two weeks

A routine sample was taken on Thursday 10 July. On 16 July, we noticed unfinalised results were higher than usual, so we carried out additional testing on Wednesday and again on Friday to monitor the situation closely. It was the text test on Friday that showed the 11.4mg/L reading which lead to the do not consume notice.

New Zealand’s Maximum Acceptable Values (MAVs) are based on World Health Organisation guidelines, which reflect the latest international scientific evidence. The Ministry of Health advises Taumata Arowai on these limits and considers the current MAV for nitrate to be appropriate.

In Gore, normal levels typically sit between 6 and 8 mg/L.