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11 September 2009
The Bulk Water Alliance has won a
prestigious Engineering Excellence award for its AUD3.2 million
geotechnical project to underpin the successful design and
construction of the enlarged Cotter Dam.
The project is part of ACTEW
Corporation's suite of water security projects to be
implemented over coming years. The Bulk Water Alliance
consists of ACTEW, GHD, and contract alliance partners John Holland
and Abigroup.
At 80 metres high, the new dam will be
Australia’s third largest concrete gravity dam – exceeded only by
Warragamba and Burrinjuck Dams. The dam’s design and construction
represents an historic project for the ACT and for Australian
engineering.
The geotechnical project was carried
out in the unusually steep work environment of the dam’s future
construction site in the Cotter River valley. The BWA geotechnical
team had to overcome many engineering challenges.
‘Working at height’ and ‘rope access’
training prepared geologists to abseil down cliffs to map rock
defects and geological faults, drill shot holes and place
explosives for seismic refraction surveys. Helicopters lifted
prefabricated drilling platforms onto site.
GHD Senior Engineering Geologist,
Andrew Barclay, said that to work safely in a site of significant
hazards, including rock fall events made more frequent following
the 2003 bushfires, BWA had to adopt procedures to manage the
safety of its personnel and the community at large.
"We worked hard to ensure that safety
was not compromised during the 11.5 month project. The project was
completed on time and within budget, without any safety incidents
or lost time to injury," Mr Barclay said.
The geotechnical data provided will
play a major role in reducing the cost of the dam. Investing in the
geotechnical investigations at the front end of the project has
enabled BWA to design an efficient foundation excavation that also
meets dam safety requirements.
The work of the geotechnical team has
been independently scrutinised throughout the project. In August
2008 the expert review panel commented that: "The investigations
and the design of the dam are in good hands. All involved are to be
commended". In June the panel wrote that: "In our opinion the
standard of geological mapping and borehole logging on this project
has been very high and provides a sound basis of assessing shear
strength and other relevant engineering properties".
The Cotter precinct is beloved by
Canberrans as a leisure destination. BWA was conscious not only of
minimising the visual and noise impact at the site, but of reaching
out to share and showcase geological and archaeological findings
with Canberrans. Children could touch rocks that were formed 400
million years ago around the Cotter Dam during a five-day event at
the National Science Festival.
Sites of Aboriginal and European
cultural heritage value were identified and participation from the
Ngunnawal Elders and other cultural and heritage groups, ensured
appropriate responses. Time and money was saved by carrying out
test pit investigations by geotechnical staff , archaeology
consultants and Registered Aboriginal Organisations
concurrently.
The enlarged Cotter Dam will secure
ACT’s water supply for future generations and its building will
provide a major boost for the local economy, at a time when the
global financial downtown is causing a drag on employment prospects
and economical development.
For further information, contact:
Donna Sowry 61 2 6175 2388