Winstone told to slow quarry work

By JAMES GARDINER

Mining company Winstone Aggregates has been ordered to stop lowering the water table under the Three Kings Quarry as fears grow that surrounding Auckland suburbs are sinking unexpectedly rapidly as a result.

Up to 6000 homes, as well as commercial property in Balmoral, Epsom, Hillsborough, Mt Roskill, Royal Oak and Three Kings, are in the area affected by the dewatering, which has involved pumping out five million litres of water a day for the past three years.

There was alarm last year when it was discovered the affected land was up to 1.8km from the quarry - not 1km as originally thought - meaning an area three times as large has been affected.

The Auckland Regional Council, which gave Winstone permission to dewater to enable quarrying of basalt and scoria, ordered it to stop at the end of last year while further tests were done and the effects analysed. It is now awaiting analysis of more information from Winstone before reconsidering.

In the meantime, Winstone has been told it may pump out only enough water to maintain the underground water level at 34m above sea level.

But local residents say there should be no water extraction at all - particularly during summer - until more work is done on the effect it is having.

"Residents are very worried," said Corinne McLaren, president of Three Kings United, a group opposed to the dewatering.

"They do not have any confidence at all in Winstone's engineers or in what [the council] is saying.

"Things have happened that they had convinced the council wouldn't happen."

Winstone and the council have said homes and other buildings should not be adversely affected but at nine of the 27 monitoring points set up the land has dropped further and faster than expected.

The most recent survey indicated land on Hillsborough Rd, near Budock Rd, had slumped 19mm in three years where Winstone engineers predicted it would drop just 5mm over the entire seven to 10-year period of dewatering.

The latest draft report from Winstone suggests movement of up 60mm could occur in that area during this decade and up to 140mm on Mt Eden Rd near Shackleton Rd.

Winstone general manager Chris Ellis said residents had nothing to worry about. "There's absolutely no way that Winstone Aggregates will get into a situation where we're going to create the liability of damage to people's property."

Mr Ellis said quarrying was continuing and provided the council agreed to a resumption of dewatering by the end of next month - which he was confident of - there would be no disruption.

Another member of the residents' group, Alan Bigelow, said property owners faced living on a "knife edge" for the life of the quarry, possibly another 30 years.

"All this talking isn't stopping the land movement," Mr Bigelow said. "Look what happened at Waihi. Everyone said it wouldn't happen."

Previous drafts of the monitoring report were rejected last year as "a load of garbage" by council water resource investigations team leader Alastair Smaill. Winstone then sacked one group of consultants and hired another.

Mr Smaill said this week that he was happier with the more recent work produced and hoped to have a final report next month.

He suggested that monitoring needed to be done not only on land and water levels but on buildings, particularly in the Mt Eden Rd-Landscape Rd area.