New WM3 Guidance: What Developers Need to Know in 2025

Waste Management | March 2025

Recent updates to the Waste Classification (WM3) guidance affect how soils and construction wastes are assessed, tested and classified in England. While the underlying principles of waste classification remain unchanged, the revised guidance introduces clarifications that have practical implications for redevelopment projects, particularly those involving excavated soils.

This article summarises the key points developers and contractors should be aware of, and how the changes may influence project planning, compliance and cost

What Is WM3?

This article summarises the key points developers and contractors should be aware of, and how the changes may influence project planning, compliance and cost.

What Has Changed in the Latest Guidance?

The updated WM3 guidance does not fundamentally alter the classification process, but it places greater emphasis on:

Robust justification of waste codes
Appropriate and representative sampling strategies
Clear documentation of classification decisions
Use of professional judgement where data is limited

These changes reflect increased regulatory scrutiny and aim to improve consistency and transparency across waste classification assessments.

Key Points for Developers and Contractors

Sampling Strategies Are Under Greater Scrutiny

The updated guidance reinforces the need for sampling strategies that are:

Proportionate to the scale and complexity of the works
Representative of the materials being classified
Clearly documented and technically justified

Generic or poorly defined sampling approaches are more likely to be challenged by regulators or waste operators.

Clear Rationale for Waste Codes Is Essential

The guidance places greater emphasis on demonstrating why a particular European Waste Catalogue (EWC) code has been selected. This includes:

Justifying the use of mirror entries
Documenting assumptions and limitations
Explaining how analytical results have informed the classification

This is particularly relevant where soils sit close to hazardous thresholds.

Professional Judgement Must Be Evidenced

While professional judgement remains an accepted part of waste classification, the revised guidance makes clear that it must be:

Transparent
Evidence-based
Clearly recorded in the classification report

Unsupported assumptions or unexplained decisions are more likely to result in delays or rejection by disposal facilities.

Increased Focus on Auditability

Waste classification reports should be clear, auditable documents that can be relied upon by:

Regulators
Waste carriers
Disposal facilities
Project stakeholders

Incomplete or ambiguous reports increase the risk of reclassification, additional testing and project delays.

What Does This Mean in Practice?

For many projects, the updated WM3 guidance means:

Earlier consideration of waste classification at design stage
More structured sampling and testing programmes
Improved coordination between environmental consultants, contractors and waste operators

While this may increase upfront planning effort, it can significantly reduce the risk of unexpected costs or compliance issues later in the project.

How Terra Environmental Supports WM3 Compliance

We provide WM3 waste classification services tailored to site-specific conditions and project requirements. Our approach focuses on:

Proportionate, risk-based sampling strategies
Clear and defensible classification decisions
Practical advice on disposal and recovery options
Preparation of concise, auditable classification reports

Our aim is to help clients achieve compliance efficiently, without unnecessary testing or waste movement.

Need Advice on WM3 Classification?

If you are planning earthworks, remediation or waste movements and would like advice on how the latest WM3 guidance applies to your project, our team can provide clear, site-specific support.