The second of two subdivisions planned for Outram will be
safe to develop, despite concerns seismic activity,
liquefaction and flooding could threaten the site, a Dunedin
City Council hearings committee has been told.
The evidence came as representatives for Balmoral
Developments (Outram) Ltd presented arguments in favour of a
plan change to the council's hearings committee yesterday.
The company, together with an adjoining landowner, want to
build 24 homes on 6.7ha of rural land beside State Highway
87, Holyhead Rd and Mountfort St.
Balmoral has applied to the council for a plan change for the
subdivision, which would have the district plan amended and
the rural land rezoned for residential use.
That was despite opposition from some neighbours and concerns
from the Otago Regional Council, in its submission, that the
site was unsuitable because of the risk of liquefaction and
settlement in an earthquake.
The suggestion was rejected as Balmoral's directors, Cathy
and Neville Fergusson, solicitor Phil Page and a panel of
seven expert witnesses began presenting the case for the
Tonkin and Taylor senior geotechnical engineer Colin
Macdiarmid, appearing for Balmoral, confirmed there was a
risk of ''piping'' beginning at the site, which was protected
from the nearby Taieri River by a floodbank.
Piping could occur when the water level on one side of the
embankment was higher than on the other, and could lead to
water seeping under the floodbank towards the lower side,
with the potentially to cause the embankment to settle or
fail completely, he said.
Investigations had concluded there was a risk of piping
beginning at the site, but only to an early stage and only in
some areas, he said.
There was only a ''very low'' risk of the process progressing
to later stages, and problems could be addressed by
engineering solutions, such as a slurry wall, he said.
''There's no reason we can see that the development should
not proceed because of the piping risk,'' he said.
He also doubted liquefaction would be an issue, even though
silty soils under the site were potentially problematic.
That was because groundwater - a key ingredient for
liquefaction - was only found 5m below the surface, meaning
there was a protective buffer between the water and the
surface, he said.
The situation was different from that found in Christchurch's
eastern suburbs, and potentially problematic parts of South
Dunedin, where homes built on land vulnerable to liquefaction
had groundwater just below the surface, Mr Macdiarmid said.
Engineering solutions, such as deeper piles or more flexible
building structures, could also be used to address any
threat, he suggested.
Evidence from engineering consultant David Hamilton, the
principal of David Hamilton and Associates Ltd, also
concluded existing floodbanks were adequate for the threat of
flooding from the Taieri River.
Speaking earlier, Balmoral's solicitor, Mr Page, also
responded to concerns from some neighbours worried
development of the site - a former market garden - would mean
the loss of high-class soils.
Mr Page told the committee the site had proven not to be
viable as a market garden, meaning the soils were already
lost in a ''production sense''.
However, the 2000sq m lots within the subdivision could
attract buyers interested in lifestyle properties, who could
put the soil to use ''albeit at a hobby scale'', he said.
Other witnesses called by Balmoral yesterday argued there
would be sufficient water to supply the new subdivision,
without ''significantly impacting'' on existing Outram
residents, and that the site was suitable for an on-site
wastewater management system.
The development would see a ''modest'' increase in stormwater
runoff, but that could be dealt with by turning a 25th lot at
the subdivision into a stormwater detention pond, engineer
Gary Dent, an associate at Spiire New Zealand, said.
A pump would also be installed to drain the pond's contents
into the nearby West Taieri drain or over the stopbank and
into the Taieri River, he said.
Balmoral's plan change request was the second to be
considered by the council's hearings committee, after Two
Note Ltd had earlier sought a plan change to allow 7.7ha of
rural land on Formby St to be rezoned for 28 houses.
A decision on that application was still pending, but it -
and Balmoral's plans - had both run into opposition from
Balmoral's application had attracted 15 submissions,
including eight opposed to the subdivision and just two in
Neighbours were worried about stormwater runoff, flooding,
traffic congestion and pressure on existing infrastructure,
on top of the ORC's concerns about water quality and seismic
The hearing concludes today.