A review of urban water quality management infrastructure in Canberra

A review of urban water quality management infrastructure in Canberra

17.11.2014 - Posted by David Barratt
The ACT Government launched their new 30-year water strategy in August 2014, called "Striking the Balance 2014-2044". Water quality and catchment management are major components of this long-term water strategy for the ACT.

Like most urban developments in Australia, Canberra’s natural waterways have been impacted by increased flows, increased flooding, reduced infiltration, erosion of watercourses, destruction of riparian and fringing vegetation and pollution of receiving waters. Infrastructure has been installed in an effort to ameliorate these impacts (e.g. gross pollutant traps, constructed wetlands, sediment ponds, etc). However, the actual performance of that infrastructure is largely unknown.

Representatives from the developer and design consultant team explaining the design intent and key features of the stormwater treatment wetland at Crace, to a group of Stormwater Industry Association representatives.

Alluvium is assisting the ACT Government to conduct a strategic review and analysis of their urban water infrastructure in Canberra. Like many other jurisdictions with significant urban growth, the ACT has seen a relatively rapid increase in the number of stormwater treatment systems, and more are proposed. The review will audit and analyse existing infrastructure to determine its effectiveness, and whether assets require replacement, retrofitting or maintenance.

The work will also inform the design of new infrastructure. Substantial investment (~ $85m) is planned in this space in Canberra over coming years under the broader scope of works known as the ACT Basin Priority Project.

Site visits with maintenance staff are useful to understand site-specific issues, performance history and their preferences for certain design features such as the standard trash racks used in the ACT (this example at Dickson wetland). Maintenance staff need to be on board with any proposed design changes.

A wet weather site visit can also highlight potential limitations in treatment performance, such as preferential flowpaths, short-circuiting, bypassing or “dead” zones in ponds and wetlands. This example shows a dead zone in the Lyneham wetland where floating debris tends to accumulate.

A critical element of the work will be to understand the suite of treatment systems in Canberra, not just from a technical perspective but also from an organisational and operational perspective. If performance is to be improved in these and future systems, it is important to understand not only where there are performance issues but also why.

Where new assets have some performance issues, if they are generally functioning well and in good condition, large-scale changes are not likely to be cost-effective or acceptable to the community. Small-scale rectification works may still be worthwhile where simple options exist to improve performance. This example shows people enjoying the view over Dickson wetland.

For more on water sensitive cities and the concepts of urban liveability, see Rob Catchlove’s interview in the Canberra Times.