Cairn Curran Dam Safety Upgrade
Cairn Curran dam was completed in 1956. Designed and constructed to the engineering standards of its day, the dam has performed effectively ever since.
However, since the original construction knowledge of dam design principles, the science of meteorology and understanding of earthquakes have all developed considerably. G-MW completed a detailed safety review of Cairn Curran in 2000 comparing the design and current condition of the dam to modern design requirements. This study identified a number of deficiencies in the dam related to lack of filters to control seepage through the main and secondary embankments and the spillway was inadequate to cope with extreme floods.
As a responsible dam owner, G-MW developed a program of works to address these deficiencies and ensure the dam continues to operate satisfactorily.
Stage 1 of the upgrade was completed in 2002 to address a high risk issue related to potential for seepage along the spillway wall and instability of the embankment in this location by constructing a filter buttress.
Stage 2 of the upgrade to address remaining deficiencies was completed in 2007. Key features of the Stage 2 upgrade include extending the rock buttress on the downstream face of both the main embankment across the upper part of the bank for its entire length, raising the clay core of the main dam to replace the deteriorated concrete wave wall on the dam crest and constructing a filter buttress on the secondary (western) dam. The rock buttress ensures that Cairn Curran is protected against cracking that could occur as a result of an existing, unidentified defect or during an earthquake. The dam is also able to withstand larger floods. All aspects of the project were subject to technical review by national and international experts.
The Stage 2 upgrade of Cairn Curran Dam was delivered two months ahead of schedule and more than $2 million under budget.
Over the eight month project 230,000 tonnes of material was used to improve the structural safety of the dam, with 35 people employed on-site and 20 
trucks delivering rock fill during the peak construction period.
The upgrade was a significant investment to ensure the long term future of Cairn Curran Dam with a large portion of the $12.5 million budget spent in the local community employing local people, purchasing materials and engaging local contractors.
