Inert muck away: Debunking myths around “inert muck”

The cost of the “muck shift” often represents a decent proportion of any construction projects budget. There is pressure to complete this as cost-effectively as possible because spending more than budgeted would still achieve the same outcome, unlike investing in better quality materials or a higher spec of product that may make a fundamental difference to the final build. Ultimately the client still sees the same “hole in a ground” and doesn’t want any financial surprises.

This is the fundamental reason why there is a push for the soils to be deemed “inert” or “clean” as the disposal route is usually the most cost-effective (and Eco-friendly), often being used for the restoration of a former quarry which has lower tipping rates and no landfill tax implications.

But has this race to the bottom caused receiving facilities, waste carriers and waste producers to interpret the rules with their commercial, rather than compliance hat’s on? Do any of the aforementioned really understand what “inert” really even means, and do they care so long as it gets the job done?

Here we look at the finer detail of how soils can be deemed “inert” and do some myth and jargon-busting in the process.

So let us start with the basics…

The term “inert”

“INERT” isn’t a waste classification for soils. Soils generated from construction activities are only ever Hazardous or Non-hazardous, that’s it. No secret third option to choose from. Based on their physical and chemical characteristics they are assigned a European Waste Catalogue (EWC) code of either 17 05 03* if they are hazardous or 17 05 04 for anything that isn’t. If you’ve ever wondered why you use the same code for virgin clay and made ground with low-level asbestos fibres, its because they are both Non-hazardous waste.
So where does the term “inert” come from and why are we so keen on our waste to be it?

Inert describes the way that waste behaves. The landfill directive defines inert waste as (and stay with me on this one!):

“waste that does not undergo any significant physical, chemical or biological transformations. Inert waste will not dissolve, burn, or otherwise physically or chemically react, biodegrade or adversely affect other matter with which it comes into contact in a way likely to give rise to environmental pollution or harm human health. The total leachability and pollutant content of the waste and the ecotoxicity of the leachate must be insignificant, and in particular not endanger the quality of surface and/or groundwater”.

So now we are fully in the picture how does one determine if their “muck” is inert…no sorry…Non-hazardous, suitable for disposal at a facility permitted to accept inert soils (not quite as catchy I know).

How to determine if “muck” is inert…

Well, firstly, the producer needs to classify their waste and determine if it has any hazardous properties. Usually, this will involve both physical and chemical assessment in line with Technical Guidance WM3. (Most projects use the Phase II site investigation to determine their waste classification which is often not fit for purpose but we can talk about that another time!) The assessment needs to include analysis of all possible contaminants based on a number of factors and the testing needs to be of the air-dried variety (NOT WAC!).

If you are lucky enough to have a Non-hazardous classification then the next step to determine inert acceptance will more often than not be WAC testing, which assesses the leaching behaviour of the soils. If inert leaching levels aren’t exceeded then the waste can be deposited at cost-effective restoration site’s, however, if there are failures, then alternative disposal options need to be thought about – this could be recycling or Non-hazardous landfill.

If you are dealing with waste soils and looking for inert disposal there are a few key rules to remember:

• You need to determine if the waste is hazardous or not, this will require relevant air-dried soil analysis
• Air dried analysis will only tell you if the waste is hazardous or not. There aren’t “inert air-dried levels”
• WAC testing CANNOT be used for waste classification, only to determine landfill acceptance
• You must ensure the testing data is relevant to the waste you are dealing with e.g location and depth of the samples were taken from where the waste is being excavated from
• You cannot tell waste is clean just by looking at it, however, with in-depth information of the site then soils do not always need analysis

Ensuring you move your waste correctly is a legal responsibility for all in the waste chain. Incorrect disposal carries significant risk of prosecution and fines, so make sure you have the expertise at hand to get it right.

About the author

Alex Collman

Waste management expert | Identifying cost savings on construction waste soil management and removal