21 Mar, 2023
David Ratcliffe and Jo Strange

Waste Classification and WAC

Soil waste classification and Waste Acceptance Criteria (WAC) tests are two important elements of construction projects with respect to waste management. Whilst both are related to the management of waste, they are different in terms of their purpose and methodology. In this blog, David Ratcliffe and Jo Strange will explore the differences between waste soil classification and WAC tests.

Waste Soil Classification

Waste soil classification is the process of characterising and categorising soil that is intended to be discarded by disposal to landfill.  The process applies to ‘excess’ soils regardless of whether the soils is deemed to be contaminated as a result of a current or historic activity.  The characterisation is based on the history and activities associated with the material, the allocated appropriate European Waste Code (EWC), and because soils are a ‘mirror’ entry in the EWC, i.e. they can be classed as hazardous wastes or non-hazardous wastes, the measured  concentrations of contaminants.   Making sure that waste soils are properly and accurately characterised and subsequently classified for disposal to a correctly licensed facility is part of the waste producer’s legal ‘duty of care’.  Incorrect characterisation and / or classification can lead to illegal disposal and result in prosecution by the Environment Agency and HMRC.

Waste soils are classified into two main categories, Hazardous and Non-hazardous, based on Technical Guidance WM3: Waste Classification – guidance on the classification and assessment of Waste, (1st Editionv1.2) September 2021  (EA/SEPA/ NRW).

The waste classifications are determined by the chemical properties of the waste and how it behaves in the environment, and specifically within the context of disposal within a landfill, and the categories are defined by the category of landfill that can accept the waste.

‘Inert waste’ is a sub-category of non-hazardous waste, that poses minimal risk and is acceptable into a licensed inert landfill.

‘Stable Non-reactive hazardous waste’ (SNRHW) is a sub category of hazardous waste, that has a low potential for leaching and, subject to meeting additional physical criteria, may be deposited in landfill cells with a less onerous standard of containment than other hazardous wastes. That cell may exist within a landfill licensed for non-hazardous wastes.

Soil waste characterisation and classification is based on laboratory measurement of the total amount of chemical contaminants in the material.

Waste Acceptance Criteria (WAC) Tests

Waste Acceptance Criteria (WAC) tests are a supplementary set of tests that determine the acceptability of waste soils into the determined category of landfill based on the waste classification. The WAC test includes two sections; a direct measurement of specified organic substances and a measurement of leachability of metals, sulfate and selected physio-chemical parameters, i.e. the ability of the waste material to release such substances into water.

The results of WAC testing determine if the waste would be likely to meet the relevant permitting requirements of the determined classification of landfill, where the classification is hazardous or may potentially be inert.

Differences between Waste Soil Classification and WAC Tests

Waste cannot be classified by use of WAC testing. The primary testing is the ‘total soils concentration’ testing.

For hazardous wastes, WAC testing provides additional information that supports whether specific additional pre-treatment of waste is required to meet the landfill permit requirements.  For potentially inert non-hazardous waste, WAC testing determines whether the lower waste classification applies.

The combination of waste soil classification and relevant WAC testing is used to determine the appropriate way to manage and dispose of excess soil intended for disposal to landfill.

In conclusion, waste soil classification and WAC tests are two important concepts in the field of waste management. While both are related to the management of waste, they are different in terms of their purpose and methodology. Understanding the differences between waste soil classification and WAC tests is essential for effective waste management and for protecting human health and the environment.



Our chemical testing laboratory and geo-environmental consultancy teams have the necessary combined and integrated skills to provide a fully comprehensive and WM3 compliant waste characterisation and categorisation service.

CGL also provides complimentary waste management advice and recommendations to support regulatory compliance, sustainability and value engineering of solutions.