The Vapour and Gas Specialist Interest Group (SIG) has considered the current Assessment of Site Contamination National Environment Protection Measure (ASC NEPM) and identified the changes needed to ensure it remains relevant and effective for the coming decade and beyond.
Why a Review is Needed
The NEPM itself requires review every 10 years:
“This Measure will be subject to a review every 10 years after the measure was last amended, or within any lesser period determined by the Council.”
The review must consider:
- Whether changes should be made to the Schedules; and
- Whether changes should improve the effectiveness of the Measure in achieving the intended environmental outcomes.
The current ASC NEPM (2013) was drafted in 2011, largely based on references from 2002–2009. Since then, technical knowledge and methods for assessing contaminated land have advanced significantly. This highlights not only the need for technical updates, but also the need to reconsider the intent, philosophy, and role of the Measure within the regulatory framework.
What Needs to Change
1. Philosophy – From Prescription to Outcomes
The NEPM is currently written in a highly prescriptive style, directing users towards specific methods and practices. This approach:
- Encourages uniformity but limits flexibility.
- Creates barriers to the adoption of scientifically valid, innovative methods.
- Risks dismissing superior approaches simply because they do not conform to “approved” methods.
A shift is needed to focus the NEPM on outcomes rather than processes. Clear articulation of desired outcomes, supported by flexible guidance, would foster innovation while maintaining protection of human health and the environment.
2. Language and Expression
The language of the NEPM strongly influences its interpretation. Terms such as “not recommended” or “only resort to” can be misleading, as they may only apply in specific circumstances but are often treated as absolute by regulators and auditors.
Guidance should:
- Avoid subjective or restrictive terms.
- Focus on outlining considerations and options, allowing practitioners to justify their chosen approach.
- Support auditors in evaluating the adequacy of justification, rather than relying on strict conformity.
This would clarify intent, reduce inconsistency, and improve regulatory outcomes.
3. Technical Content – Modernising the Science
The NEPM’s technical content reflects the state of practice in the late 2000s. For vapour and gas assessment, this was an early stage of development in Australia. Advances since then have rendered much of the guidance outdated.
Examples of areas needing urgent revision include:
- The technical legitimacy and applicability of passive soil vapour sampling.
- Updated approaches to vapour flux measurement.
- Recognition of the unsuitability of bulk soil samples for VOC risk assessment.
- A comprehensive revision of vapour intrusion risk assessment methods.
- Use of surrogate analyses and hydrocarbon fractions.
- Revised indicators for field QA/QC.
- Incorporation of landfill gas risk assessment.
- Stronger technical basis for groundwater sampling and indoor air measurement.
Without updates, the NEPM risks holding back the application of modern methods and tools already well established internationally.
Consistency vs Flexibility in Implementation
The NEPM recognises:
“There should be a consistent approach to the assessment of site contamination across Australia, but each participating jurisdiction may implement the necessary controls in its own manner.”
In practice, jurisdictions interpret and implement the NEPM differently, often through their contaminated land auditor systems. This has led to variation in application across states and territories. While sensible implementation can mitigate some issues, this should not substitute for an updated and modernised NEPM.
Conclusion
The ASC NEPM has been central to national consistency in contaminated site assessment. However, its prescriptive philosophy, restrictive language, and dated technical base limit its effectiveness and risk impeding scientific and professional progress.
Reform should focus on:
- Shifting from prescription to outcome-based guidance.
- Adopting clear, neutral language that empowers professional judgement.
- Updating technical content to reflect the best available science and international practice.
With these changes, the NEPM can continue to provide nationally consistent, scientifically robust, and future-ready guidance for contaminated land assessment in Australia. Significant benefits to the contaminated land assessment business would result from a philosophical change to the Measure achievable through critical re-wording, to move it from its current focus on process and compliance to one centred on guidance and outcomes.