Waimea Plains property owners are being warned after elevated nitrate levels in some private bores have made the water undrinkable.
Recent sampling in the Bartlett Road and Ranzau Road West area has uncovered unexpectedly high nitrate concentrations, exceeding the Ministry of Health’s drinking water standards.
“Of the 10 bores sampled, seven were at levels we felt it necessary to inform the landowners that there has been a change over what we would have expected for their bore,” says Tasman District Council Environment and Planning manager Dennis Bush-King.
Dennis says it is not clear what has caused the spike, but onsite waste disposal is a possibility, given the free-draining nature of the gravels in the area.
The land use in the area is a mix of domestic dwellings/lifestyle blocks, apples, market gardens and grapes.
The Ministry of Health has set a Maximum Acceptable Value (MAV) of 11.3 g/m3-N for nitrate-nitrogen in drinking water.
If the concentration is higher than this, the water can pose a health risk to some people, especially infants in the womb or infants under six months old who are bottle-fed.
This risk from the nitrates may increase if the drinking water is also contaminated with microbial pathogens. Adults with some rare metabolic disorders may also be at risk.
“We know that not all of the wells and bores sampled as part of this survey are currently used for drinking water,” says Dennis. “The health risk is only of concern if the well or bore in question is used to supply drinking water.”
Dennis says the high concentrations should not affect the Waimea River and the Council’s reticulated water supply is unaffected.
If you have concerns about the quality of you drinking water supply, call the Council’s Environmental Health Officers on 03 543 8400.