First, let’s discuss the reason why they are produced.

At the planning stage of any project, there is invariably an imposed condition to assess any potential contaminative sources on the site, and the risk that they might pose to end users, groundwater and the general environment.

The Process

Phase 1 Investigation – usually a desktop study, sometimes including a general site walkover, but not intrusive and no laboratory-based analysis is undertaken. The Phase 1 study will generally determine if there are any potential risks and if further investigation is needed.

Phase 2 Investigation – if the Phase 1 study has identified some possible contamination risks, then an intrusive investigation is required. This will investigate those risks through analysis and monitoring and determine if indeed there are hazards present. If Phase 2 identifies unacceptable risks, then a remediation strategy will be required.

Remediation Strategy – this will provide guidance on how to remove or mitigate the hazard(s) so that the site does not pose any unacceptable risk to any potential receivers (people, wildlife, groundwater). The remedial work conducted by a contractor will need to be verified to discharge the planning condition and satisfy the planning officer that the site is not a contamination risk.

So, what is the glaring omission from all the above? WASTE CLASSIFICATION!

There is no stipulation at the planning stage for a waste classification assessment to be undertaken. Often there isn’t any real certainty as to where waste will be generated (if any are to be generated at all) so this is understandable. But when the tenders go out, or the project commences and waste needs to be moved, what information is available to accurately price the waste soils? That’s right…the site investigations, the very investigations that were designed to assess risk rather than classify waste.

So, let’s look at some of the reasons why these Si’s are often not fit for waste classification purposes:

• Insufficient sampling frequencies – The Si may have been done on a budget, or conducted at the time whilst the site was still active prior to development, both of which would inhibit where samples could be taken from.
• Irrelevant areas of the site tested – Often where the waste is being generated from, either in location or depth, is not where the soils have been sampled and analysed, meaning they are a complete unknown.
• Sampling techniques – Often due to site restrictions at the time of the investigations small window samples are needed to be taken, these can be cores of just several inches in diameter and can easily miss contamination that may be present in the ground. Often a site is assumed to be “clean” but when excavation starts in earnest, a host of issues are uncovered.
• Incorrect testing for waste classification – Assessing soils for risk to health and the environment has a different set of criteria to waste classification, therefore some of the analysis may not be suitable, or certain contaminants may not have been tested for. A regular example is when asbestos is found. From a risk perspective any asbestos is generally unacceptable, so they merely test for its presence. However , it needs to be quantified from a waste perspective, which is often missing, causing delays and uncertainty.
• NO WAC – WAC leachate analysis is required to determine wastes suitability to landfill, and this is most commonly used to determine if soils are suitable for inert landfill disposal (often the most cost-effective disposal solution). Si’s are designed to assess risk, not landfill suitability, yet every contractor wants to know “is my muck inert”?
• Other wastes go unassessed – The most common example would be the presence of coal tar in asphalt. Asphalt is rarely (if ever) tested during a Si, however the prevalence of hazardous coal tar is far more common than most realise and is often mishandled by the waste producer.

This is a common process that generally leads to one of two scenarios:

Waste is misclassified and/or mismanaged due to time constraints and commercial reasons

OR

The project is delayed due to the need for further sampling and analysis so the waste can be properly classified and managed. Often this can cause issues if contamination is identified, it can seriously affect budgets, or if the contractor has taken risk on the project can seriously affect profitability.

We would be naive to think all sites should conduct waste classification analysis from the outset, however, the keys are:

• Understand the limitations of the available site investigations.
• Assess the possible risks that may yet be undiscovered.
• Create a waste sampling strategy early, so that waste can be managed effectively and there aren’t too many surprises when ground is broken.

If you need someone on your side that can assist your business with this, get in touch with SoilEx.

About the author

Alex Collman

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