If you've ever stared at a lab result that exceeds your NEPM HIL and wondered "okay, but what does this actually mean?". This one's for you.

Gunnar and James sit down with Kylie Dodd, environmental toxicologist and risk assessor at GHD, to get into the science behind the numbers that so many of us lean on without fully understanding where they come from. Kylie has a great way of making this stuff click, and the conversation goes places that are genuinely useful for day-to-day practice.

They get into why Tier 1 screening levels are built to be conservative by design, why an exceedance doesn't automatically mean you need to remediate, and what it looks like to think a bit deeper, what they're calling "Tier 1.5 Risk Assessment — without needing to be a fully-fledged risk assessor yourself.

A big chunk of the conversation is about the practical stuff: how to get more out of your conceptual site model (CSM), how to think about exposure pathways and bioaccessibility, and how realistic site use should dictate the way you interpret results. Some of those small shifts in thinking can make a real difference to the recommendations you're putting forward.

They also get into how risk assessments hold up under regulator scrutiny, when an environmental management plan is actually the right tool, and what data decisions early in a project can save a risk assessor a lot of headaches later.

Fair warning: this episode won't make you a risk assessor. But it might change how you think about what those numbers are really telling you — and what you do next.

Links:

ASC NEPM Toolbox

Episode 38 The Bioavailability

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The necessary disclaimer: The views, thoughts, and opinions expressed in this Podcast are the speakers’ own. They do not necessarily represent the views, thoughts, and opinions of 4Pillars Environmental Consulting Pty Ltd or any Client, Supplier or other party related to 4Pillars or the speakers.

(c) Gunnar Haid and James Hammond

A deeper dive into Acid Sulfate Soils. In a slightly QLD centric episode, Gunnar and James are joined by all three main authors of the QLD ASS Management Guidelines, widely regarded as the best ASS guidelines in the world.

Sue-Ellen Dear is a Senior Land Resource Officer with the QLD Department of Natural Resources and Mines and has contributed to acid sulfate soil policy and guidance since 1996. She is lead author of the QLD ASS Management Guidelines.

Kristie Williams has spent nearly 25 years in the QLD government soils team, working across ASS, salinity, erosion and land resource assessment. She has authored technical reports, contributed to regulations and assessed developments from small works to major canal estates.

Dr Angus McElnea Angus developed the SPOCAS method, contributed to laboratory guidelines, and co-authored Australian (AS 4969) and international (ISO 14388) standards. He is a NATA technical assessor, worked on the East Trinity remediation project, and is currently involved in greenhouse gas and fertiliser efficiency research.

They unpack how acid sulfate soils form and what really happens when these soils are disturbed. They cover pyrite formation, potential vs actual acid sulfate soils and the “trinity of acidities” and then discuss real-world management challenges.

They put forward avoidance of disturbing ASS as the first priority, the realities of liming and mixing on treatment pads, the controversy around acid neutralising capacity, and why incubation testing matters. They talk about strategic reburial, the pros and cons of centralised treatment facilities, the carbon cost of treating ASS, and the industry’s tendency toward conservative safety factors (with a small Gu-rant - they are always audience favourites so we hear)

The episode finishes with validation testing, safe reuse of treated soils and the future of professional certification through the Registered Soil Practitioner scheme.

If you work in contaminated land, coastal development, infrastructure or groundwater, this episode is essential listening.

Links:

BTS #23: The Basics: Acid Sulfate Soil

Legislation and policies for ASS management in Qld

ASS guidance material

Retained Acidity Technical Note

SNAS correction by NATA

Gunnar loves ASS

Listen to Below the Surface and collect CPD points. We have confirmation that you can claim 0.5 points for every hour you spend with us under the Self Education Category

Contact: bts@4pillars.com.au

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The necessary disclaimer: The views, thoughts, and opinions expressed in this Podcast are the speakers’ own. They do not necessarily represent the views, thoughts, and opinions of 4Pillars Environmental Consulting Pty Ltd or any Client, Supplier or other party related to 4Pillars or the speakers.

(c) Gunnar Haid and James Hammond

How much of any given contaminant is actually taken up into human bodies?

If we think about it, that is one of the single most important things to consider as an environmental consultant when reporting on a site's contamination status, yet it is not something that is very often done. Gunnar and James are yet again soaring with an industry eagle as they set out to get better at that very aspect of consulting.

They chat with Dr Albert Juhasz, a Research Professor at the Future Industries Institute, internationally recognised for cross-disciplinary research on contaminant bioavailability and human health exposure. He has led development of one of the world’s largest contaminant bioavailability databases and advanced in vitro methods now applied at more than 100 contaminated sites across Australia.

His work has informed national and international exposure assessment policy, including the ASC NEPM and EnHealth Guidelines, and influenced regulatory guidance in the US, Canada and New Zealand. Albert is a senior journal editor, WHO consultant, contaminated-site auditor adviser, and a highly cited researcher (H-index 37).

The episode was recorded on 7 November 2025

Listen to Below the Surface and collect CPD points. We have confirmation that you can claim 0.5 points for every hour you spend with us under the Self Education Category

Contact: bts@4pillars.com.au

https://www.linkedin.com/company/below-the-surface-podcast

The necessary disclaimer: The views, thoughts, and opinions expressed in this Podcast are the speakers’ own. They do not necessarily represent the views, thoughts, and opinions of 4Pillars Environmental Consulting Pty Ltd or any Client, Supplier or other party related to 4Pillars or the speakers.

(c) Gunnar Haid and James Hammond