What is WAC testing, and when do you actually need it?

What WAC testing measures

WAC stands for Waste Acceptance Criteria. The test takes a prepared sample, passes water through it under controlled conditions to BS EN 12457-3, then analyses the resulting leachate — the liquid that has picked up whatever will move out of the soil.

The results are compared against the limit values for each landfill class: inert, stable non-reactive hazardous (SNRHW), and hazardous. The output is therefore a destination, not a verdict on the soil itself.

Because it is a leachate test, WAC tells you about mobility. Two soils with the same total contaminant concentration can produce very different WAC results depending on how tightly the contaminants are bound.

When you need it — and when you don't

You need WAC when material is going to landfill and the receiving facility requires evidence that it meets that landfill class. This is normal on brownfield, infill and any site with made ground.

You need it when a WM3 classification has identified contamination and the disposal route depends on leachability.

You usually do not need it for clean, well-documented greenfield subsoil going to a recovery or restoration site — classification plus the facility's own acceptance procedure often covers it.

You never need it as a substitute for classification. WM3 classification comes first and decides hazardous vs non-hazardous; WAC then confirms the acceptable landfill class.

Sampling: where most projects go wrong

Sampling follows BS EN 14899. The sampling plan should reflect the volume, the site history and the variability of the material — one grab sample from the top of a stockpile is not a defensible basis for classifying several hundred tonnes.

Sample by discrete zone or stockpile, not across obviously different materials. Mixing a clean subsoil with a suspect made-ground layer produces a result that describes neither.

Take samples before the excavation reaches the layer you are unsure about, so lab turnaround runs in parallel with other works instead of stopping them.

Timescales and what to expect back

Standard laboratory turnaround from sample receipt is typically around five working days, with accelerated options available where the programme demands it.

You should receive the leachate results against each landfill class, and — where the fuller job has been done — a WM3 hazard assessment and a plain statement of the acceptable disposal route.

Keep the report in the site file with your transfer notes. It is the document an inspector, a principal contractor audit or a receiving facility will ask for.

Booking testing and removal as one job

The efficient sequence is: sample, classify, confirm the route, then mobilise haulage. Splitting testing and haulage between two suppliers is where gaps and standing time appear.

Atlas Stone Supplies samples to BS EN 14899, runs analysis through UKAS-accredited laboratories, issues WM3 assessment, then removes the material to a licensed facility and back-loads aggregate on the return leg.

Start with our WAC testing hub for the classification detail, or request a quote with your site postcode, the material and rough volumes.