Urea fertiliser spill stops water intake from Waikato River

Hamilton's water treatment station stopped taking water from the Waikato River after 13 tonnes of urea fertiliser was spilled into it near Hamilton today.

And Auckland will temporarily stop taking water from the river tomorrow.

The urea got into Waikato River when a truck crashed about 7.30am today on Narrows Bridge near Hamilton Airport.

The truck had been wedged across the bridge with its trailer unit dangling over the side.

When mixed with water, urea turns into ammonia and carbon dioxide.

Environment Waikato closed Hamilton's water treatment station intakes this morning, but did not think it would affect the water supply.

Aucklanders are not expected to notice any impact from the shutdown.

Auckland's Watercare Services spokesman Owen Gill said treatment of the river water would be suspended sometime before midday tomorrow.

A $155 million pipeline system taking water from the river to Auckland started operating last year after a drought in 1994 caused supply concerns.

The plant at Tuakau, about 10km southeast of Pukekohe, would be shut down several hours before the urea passed the supply intake, Mr Gill said.

"Under current flow rates in the river, it will take 32 hours for any traces of the urea to pass the intake."

Any urea in the river, which provided about 6 per cent of Auckland's bulk drinking water, would be highly diluted by the time it reached Tuakau.

"Nonetheless, Watercare has strict risk management practices, and the company has decided to suspend operations at Tuakau in order to provide absolute public reassurance that there is no threat to Auckland's water supply," Mr Gill said.

Environment Waikato said initial checks along the river had turned up no dead fish.

- NZPA