The Christchurch earthquake had Dunedin City Council staff
checking for fresh cracks at the Ross Creek Reservoir dam.
The dam was patched in June, after large cracks were
discovered across the face of the 143-year-old earth wall.
Council water production manager Gerard McCombie yesterday
said he was back at the dam by 6.45am on Saturday - just over
two hours after the 7.1 magnitude earthquake devastated parts
of Christchurch - but found no signs of fresh damage.
The dam was not the only one checked. Mr McCombie said it was
standard practice to visit dams around the city after an
earthquake. No signs of damage had been detected at any of
them.
Mr McCombie returned to the Ross Creek dam again yesterday to
carry out further checks, and again found no reason for
alarm.
"I was reasonably confident but ... it's an old structure and
you have just got to keep an eye on it."
Mr McCombie said the possibility of a large earthquake
striking the area had been considered when Opus International
staff were asked to assess the dam's stability, after the
discovery of its cracks on June 3.
Opus staff had decided the dam was safe despite the cracks,
which were patched up until long-term decisions about the
dam's future could be considered by city councillors.
Opus International technical services manager Ian Walsh, of
Dunedin, said there was "a good chance" the dam would have
withstood a 7.1 magnitude earthquake, even if it were centred
on Dunedin.
The cracking in May was the result of saturated ground, which
had since begun to dry.
Further damage would depend on a combination of groundwater
inundation and the size of any earthquake.
- chris.morris@odt.co.nz
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