Assessing the performance of stormwater infrastructure: Understanding system objectives

Assessing the performance of stormwater infrastructure: Understanding system objectives

16.03.2015 - Posted by David Barratt
We all know that water quality infrastructure assets have essentially the same objective – to clean water. Right? Well, yes, but it’s not that simple.

Yerrabi Pond (Canberra) provides significant community benefits beyond stormwater quality treatment
Yerrabi Pond provides significant community benefits beyond stormwater quality treatment

Our ongoing work with the ACT Government to conduct a strategic review and analysis of urban water quality management infrastructure in Canberra* has highlighted the broad range of stormwater treatment systems in existence in the ACT and the range of performance objectives that these systems are being assessed against.

Of course, these assets must be assessed against their main objective to manage water quality, but some assets (particularly the larger ones) have additional objectives, such as stormwater harvesting, floodplain management, habitat and biodiversity improvement, amenity, and recreation.

The objectives of treatment systems designed (for example) 20 years ago reflect the philosophies and paradigms of that time and, therefore, often differ to what is expected of stormwater treatment systems today. While recent treatment systems in greenfield areas may be designed to meet the pollutant removal objectives specified in design codes (or are part of a treatment train designed to meet those objectives), older treatment systems have generally been designed to different standards.

Retrofitted infrastructure is often designed to meet a broader range of objectives, including urban biodiversity and community engagement goals.

There are also pragmatic objectives, such as minimising ongoing maintenance costs.

The performance of assets therefore needs to be assessed against the range of objectives that are specific to each site. Understanding this suite of objectives and their relative importance is a critical step in assessing treatment systems. Without a real and comprehensive understanding of each stormwater infrastructure asset’s specific objectives, incorrect conclusions can be drawn – and a water quality management system may be underrated when in fact it is meeting its original objectives, or is failing only with regard to one of a range of objectives.

* Part of the ACT Basin Priority Project (click here).


Other relevant blogs:

A review of urban water quality management infrastructure in Canberra (November 2014)
The ultimate design challenge: aesthetically appealing + cheap + resilient in extremes (September 2014)

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