Arsenic in Private Well Highlights Importance of Testing

Published: 08-May-2019

Council is reminding owners of private wells to have their water regularly tested, following a few recent private well tests showing elevated arsenic levels in the north-west of Kaiapoi.  The arsenic is thought to be naturally occurring, though further investigation is intended to be carried out by the Council.

Utilities and Roading Manager Gerard Cleary advises “There is no need to be concerned if supplied by a Council reticulated water scheme. The Council supplies have regular testing, with no water supply affected by elevated arsenic levels.”

A Kaiapoi landowner brought arsenic in groundwater to the attention of the Waimakariri District Council, after obtaining a water test for their private well supply. The discovery highlights the importance of private well owners to know that they are responsible to undertake their own water monitoring.

The test showed a level of arsenic above the Maximum Acceptable Value (MAV) of 0.01 milligrams per litre (mg/l), as set out in the Drinking-water Standards for New Zealand (DWSNZ).

“Consumption of arsenic over 0.01 mg/L can cause adverse health effects over the long term so it’s important to test regularly – at least annually - to check that water is safe to drink. Arsenic levels can change seasonally. The test for arsenic is particularly important in the coastal areas of our district where groundwater oxygen levels get low” says Council’s Water Environment Advisor Sophie Allen. “Arsenic is just one contaminant that well owners should look for, with testing also recommended for other potential contaminants such as nitrates and E. coli (bacterial contamination).”

Following the notification, Council has carried out testing on five private wells to the north-west Kaiapoi to assess the extent of higher arsenic levels in neighbouring properties, with another property found to be above the MAV.  Over the next 10 months the Council, with the support of Environment Canterbury, intends to undertake further work to determine the extent of the issue in the wider Kaiapoi area below Woodend.

High levels of arsenic have been known to be found in some selected private wells in the Waikuku, Saltwater Creek and Woodend area since early 2000’s. “The arsenic in this northern coastal part of the Waimakariri District was concluded in a 2001 study to be from natural sources found in certain sediments, which is released into groundwater when oxygen levels are low.” says Sophie.

Gerard Cleary recommends that people on private wells regularly test their water to ensure it is safe. “This incidence is an important reminder for private well owners to have their water checked by an accredited laboratory ensuring water is safe to drink.”

Standard filters are not adequate for the removal of arsenic, and advice should be sought from a water treatment specialist on the appropriate filtration system for removal.

Any private well owners who have found arsenic levels over 0.01 mg/L in the wider Kaiapoi Area are encouraged to notify Sophie Allen - Water Environment Advisor, Waimakariri District Council.

Find out more:

Click here for health information about arsenic.

Do you get your household water from a private well?

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