Can you pile through Contaminated Soils?

Contaminated sites are often ‘Remediated‘ rather than ‘Decontaminated’ which means that the underlying soils which are subsequently built over still have a degree of contamination within them. While this is not sufficient to cause a risk or warrant further action as they sit there in their current form, they may however represent an issue when it comes to activities such as piling which bring them to the surface. 

Why? We’ll explain.

Firstly, the soil arisings (or contamination itself) is subject to two sets of regulations:

  • The Contaminated Land Regime which works on a risk-based scenario in terms of what risk is being caused by those contaminants as they sit there. 
  • The Waste Regulations (2011) which look at the risk of the material in terms of its hazardous properties when it is brought to the surface as a waste. 

The second thing that needs to be considered is that piling for example can create preferential pathways, which is the uneven and often rapid downward percolation of contaminated water into protected aquifers.  For this reason, planning consents on most brownfield sites require a Foundation Risk Assessment to assess the potential for piling or other penetrative ground improvement methods to mobilise contamination or to create preferential pathways for contamination to migrate. 

This means we have a risk of worsening the environment by piling or penetrative ground improvement methods as something is entrained and driven to depth or excavated through and contaminated soils are disturbed. 

The third issue concerns managing the arisings which could be classed as an expensive waste to handle with some hazardous properties. 

On top of this, there is the issue of the arisings getting mixed as they come up off the piling auger or similar excavation method so we can end up contaminating otherwise clean material with contaminated soils.

Finally, and perhaps the most prevalent issue that is coming up at the moment, there is the health and safety of the piling operatives and local stakeholders. As we excavate this material through piling or other means, we’re bringing contamination to the surface which may have an adverse health effect if not managed properly. A classic example of this is asbestos. 

So, can we pile through contaminated soils? 

The answer is yes subject to permission, with appropriate health and safety controls in place and good knowledge and foresight of what the contamination status or the waste classification status of those arisings are going to be. 

If it’s done in a measured and considered way, cost can be controlled and potential health effects can be readily and cost effectively mitigated, and we’ll have the full buy in of the regulator. 

If it’s done in a reactive way without foresight or forethought there is potential to fall foul of the planning regime, or the Health and Safety Executive to stop the job, or for local residents to be impacted, or to mobilise contamination. At the very best there is a time and cost delay on the project as we end up dealing with more contaminated material than was originally expected or was originally  tendered.

For peace of mind on your project, contact us to speak to an expert about your plans.