Australian Water Management Review Vol. 1 2014 | Page 38

Securing
Canberra’s
water supplies

C

At 87 metres high the Cotter Dam is the tallest
Roller Compacted Concrete (RCC) dam in Australia,
and required approximately one million tonnes of
aggregate to be crushed to produce over 360,000m3
of RCC. Placement continued for 14 months, 24
hours per day seven days per week. Innovation and
continuous improvement ultimately ensured a high
quality structure was completed safely.

The project was delivered by the Bulk Water
Alliance, a collaborative venture between ACTEW
Corporation, GHD, Abigroup and John Holland.

In 2008, work commenced on a fiveyear project to design and construct
an enlarged Cotter Dam, 20 times the
capacity of the existing dam which was
built almost a hundred years before.

ompleted in August and officially opened
to the public in October 2013, the dam is
one of the most significant infrastructure
projects in Canberra’s history. It has
increased Canberra’s water storage
capacity by 35% to an impressive 277 billion
litres, and will sustain growth in the ACT and
surrounding regions for future generations.

Benefits to the ACT economy

In delivering this complex project a number
of significant challenges had to be overcome,
including extremes of temperature and some of
the wettest periods in Canberra’s recorded history.
Numerous complex environment obstacles, safety
considerations and engineering challenges were
also successfully overcome, bringing benefits
beyond the scope of increased water capacity into
areas such as the ACT economy and the engineering
and construction industries.
Engineering innovations
The collaborative environment promoted by the
alliance framework enabled continuous improvement
and innovation that proved crucial to the success
of the Cotter Dam project. World firsts, including
incorporating an aeration step in the primary
spillway and use of a paver for roller compacted
concrete placement, confirmed Cotter Dam as
world’s best practice in design and construction.
32 | Australian water man age m e nt re v ie w

The new Cotter Dam provides security against
a future water crisis, which has far-reaching
implications including financial implications for a
region that has faced the threat of insufficient water
in the past.
By expanding the size of the dam from four
gigalitres to 78 gigalitres, increasing its storage
capacity more than twentyfold and the storage
capacity of the ACT by around 35%, the region now
has enough water storage capacity to last at least a
generation and the threat of water restrictions has
been removed.
Previously, water restrictions have created flowon costs to households, as well as commercial
activities and water-intensive businesses and the
tourism sector. According to David Pearce, Centre of
International Economics Executive Director:
“The magnitude of these costs can be measured by
observing the effects of restrictions on particular
activities. These latest estimates suggest that, for