The largest water quality infrastructure project in the Australian Capital Territory (ACT) – the $93.5 million ACT Healthy Waterways Project – has been delivered on time and on budget. The 20 infrastructure assets constructed over two years have the biggest footprint of any water quality infrastructure project undertaken in the ACT.

The ACT Healthy Waterways project was a joint initiative of the ACT and Australian governments to improve the quality of water entering Canberra’s lakes and waterways and flowing downstream into the Murrumbidgee River system.

The project included the construction of stormwater treatment infrastructure – like wetlands, ponds and rain gardens – as well as research trials, a community education campaign and improvements to water quality monitoring practices.

Alluvium has been part of this journey, from supporting the development of the original business case to investigating site options and developing functional designs for some of the over $60 million of water quality infrastructure eventually installed. Alluvium continue to work with the ACT Government, advancing understanding of the relationships between urban water management and human health and welfare outcomes.

Alluvium was first engaged by the ACT Government in 2014 to undertake a strategic review of stormwater treatment infrastructure in Canberra to provide key inputs into the ACT Healthy Waterways Project methodology. The project focussed on assessing the performance of different types of treatment systems and recommending how their performance might be improved, from a planning, design, construction and operations and maintenance perspective. The work involved high-level qualitative assessments to initially rank performance, and then more detailed quantitative methods to provide specific information on water quality treatment performance and life cycle costs.

In 2015, as part of the first phase of the ACT Healthy Waterways Project, Alluvium investigated water quality improvement solutions in priority catchments in the ACT and Upper Molonglo River and developed whole-of-catchment treatment train options (i.e. source control options, catchment management options and intervening infrastructure).

A key task in this work was to identify sites within the public domain where infrastructure could potentially be located to help achieve water quality objectives. An initial “coarse filter” process was undertaken that involved site assessment against engineering feasibility criteria and environmental criteria. Short-listed sites were presented to the general public through a community consultation process.

Alluvium developed advanced concept designs for 23 sites across four catchments in the ACT and subsequently developed detailed designs for the construction of treatment systems at three sites, including two constructed wetlands and a peri-urban creek rehabilitation.