The WA Department of Water and Environmental Regulation (DWER) recently published the WA Environmental Offsets Calculator and associated guidelines (Environment Offsets Metric: Quantifying Environmental Offsets in Western Australia), creating WA’s new environmental offsets metric (the Offsets Metric).


  1. The Offsets Metric was recently introduced as part of WA’s environmental offsets framework.
  2. The WA Offsets Metric aims to enhance the existing offsets framework, creating transparency and consistency when assessing offsets under Parts IV and V of the Environmental Protection Act 1986 (WA) (EP Act), as well as between State and Commonwealth assessment processes.


The existing environmental offsets framework has been in place in Western Australia for over a decade, consisting of the Offsets Register, the WA Environment Offsets Policy (September, 2011) and the WA Environmental Offsets Guideline (August, 2014).

Following a review of the framework, the Offsets Metric was published by DWER on 26 October 2021.

Quantification and consistency

The Offsets Metric is intended for use in new approval applications under both Part IV and V of the EP Act. It adopts a balance-sheet approach to capture the minimum offsets required to counterbalance significant environmental impacts and quantify benefits.

Key objectives associated with this tool are transparency and consistency.

Notably, the Offsets Metric was developed in consultation with stakeholders, using the Environment Protection and Biodiversity Conservation Act 1999 (Cth) (EPBC Act) offset calculator as a point of reference. As the Offsets Metric is aligned with the Commonwealth offset calculator, streamlining of State and Commonwealth assessment processes is anticipated.

Using the Offsets Metric

Below we outline the key steps in the Offsets Metric.

  1. Determine conservation significance: Step one determines a conservation significance score for the impacted environmental value. The conservation significance score will reflect the level of threat for the relevant environmental value. Generally, the greater the conservation significance, the larger the offset.
  2. Calculate significant residual impact: Step two comprises three parts, which calculate the quantum of the impact for a project area, an allowance for any onsite rehabilitation and the significant residual impact in respect of an area and a feature.
  3. Calculate offsets: Step three captures the offsets calculation, allowing a user to input values to calculate the suitability of counterbalancing various environmental impacts. In certain circumstances, it may be considered appropriate to propose multiple offsets to address a single significant residual impact.

Next steps

The operation and effectiveness of the Offsets Metric will be monitored and reviewed in 12 months.

To view the new Offsets Metric tool, and the associated environmental offsets framework, visit this link.