Oceana Gold's proposed Macraes mine extension is unlikely to
affect water quality or quantity at Macraes Flat or the local
school, hydrogeologist Brett Sinclair says.
Mr Sinclair was giving evidence on behalf of Oceana Gold on
the third day of its resource consent hearing in Dunedin.
The company had been monitoring water quality in bores for
many years and only barely detectable amounts of contaminants
had been found, he said in his response to concerns from the
Education Minister about the Macraes-Moonlight School.
"Nothing has changed as the consequences of the mining
operation."
While water quality at existing compliance monitoring sites
had "almost always" complied with consent criteria, trends of
increasing sulphate concentration had been observed at
several surface-water compliance points, mostly related to
seepage from waste-rock stacks.
Sulphate concentrations were likely to eventually exceed the
relevant compliance limits on a seasonal basis, so mitigation
was required on all creeks intersecting the mine site, he
said.
He proposed an adaptive management plan be adopted, requiring
a high-quality water monitoring programme.
Flows in Tipperary Creek would be substantially reduced
during the operating period of the new tailings storage
facility, but they would recover after the closure and
rehabilitation of the existing tailings storage facility, he
said.
Oceana Gold counsel Stephen Christensen said Mr Sinclair was
picking up on long-term trends in relation to sulphate
levels.
"It's not a problem today and not a problem while the mine is
going."
The specialists were looking "way out" to the future and the
company was planning for those after-closure issues, he said.
"The company is being proactive."
Acoustic engineer Nevil Hegley said noise levels, and their
effect on nearby homes, had been predicted for each stage of
the proposed extension.
"During busy mining periods of each stage, the noise level at
all of the closer houses will remain well within the current
mine consent conditions ..."
Although noise levels were relatively low around the Macraes
township, the predicted noise level was also low, he said.
"While the mining might be heard in calm weather conditions
and with wind speeds up to 1m or 2m per second, even under
these conditions there will be little to no noise impact for
neighbours."
Technical services engineer Richard Taylor said provided
blasting operations continued in a controlled manner, similar
to as it was done now, adverse effects from ground vibration
and air blast were expected to be no more than minor.
Engineer Prudence Harwood said as the proposed works were
similar in scale to the present operation, "consequently the
effects of the operation were not expected to be
significantly different".
Dust levels were within consented levels and there had been
no reported adverse effects on plants or wildlife in the
vicinity of the mine.
"Providing particular care is taken with activities that have
a high potential to create dust in sensitive areas, such as
the remediation of the tailings storage facilities and the
construction of the extended waste-rock stacks, the effects
of the MPIII [Macraes phase 3] project should not be
significantly more."
The hearing continues today.
Oceana Gold hearing
Day 3
Applicant: Oceana Gold
For: Resource consents to extend the life of Macraes
mine.
Panel: Otago regional councillors Louise Croot
(chairwoman) and Duncan Butcher.
Submitters: Golder Associates senior hydrogeologist
Brett Sinclair; Golder principal geochemist Rens Verberg
(read); acoustic engineer Nevil Hegley; Orica Mining Services
technical services engineer Richard Taylor; Beca
Infrastructure associate engineer Prudence Harwood.
Macraes Phase III project
• Close existing mixed tailings impoundment and southern pit
impoundment.
• Construct a new tailings storage facility called Top
Tipperary.
• Construct a new dam on Camp Creek for water storage.
• Mining Round Hill - southern pitContinuation and expansion
of Frasers underground mine.
• New waste rock stacks and extensions to existing rock
stacks.
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