How properly identifying and dealing with contaminated waste can save construction projects time and money

Written by: Jo Gallacher | Published:
Developers and contractors need to have the right information about the nature and location of any contamination on their site

Most waste generated in the UK comes from construction sites, chemical plants or factories and is at risk of containing toxins and contaminants that can cause harm to human health or the environment.

In 2014, the last date that figures were available, construction, demolition and excavation generated over half of UK waste at 59%.

Not only is it important for businesses to know whether their waste is hazardous or non-hazardous, it is also important to know exactly what kind of danger it presents and how to manage those risks.

Previous occupants on the site can affect the contamination within the land. For example, old power stations, old industrial sites, heavy plant operators or petrochemical sites can all impact the land beneath, posing an environmental risk.

Through their operating processes, fuel storage or their material management procedures, land can become contaminated with any number of pollutants or hazardous materials such as heavy metals and chemicals.

In high concentrations, lead – a toxic metal – can cause acute problems with the nervous system. Hydrocarbons are carcinogenic and can give rise to health concerns, even at low concentrations. Asbestos in soils is also a risk for developers, although it will only present a risk if there is a potential for the asbestos fibres to be released from the soil and subsequently inhaled by the construction worker or site user.

Readying a brownfield site for development can be a challenging process because any soils found to be contaminated must be made safe through remediation or must be disposed of. With over 50 million tonnes of soil waste generation in 2014 in the UK, earthworks and excavation often require management and support to address contamination levels on the site.

Controlling waste management risks and minimising uncertainties is fundamental to development and remediation projects; soil analysis provides an understanding of the available materials within the ground and can support the material handling plan.

One of the main goals for any developer is minimising the volume of hazardous waste. This can be achieved by either following the waste hierarchy or by classifying material to determine if it is hazardous or non-hazardous for appropriate handling and disposal.

Minimising volumes of material waste

The most effective way to manage waste is outlined in the waste hierarchy, used across industries to establish and evaluate the processes of waste management. Regardless of whether the site is a construction site, manufacturing site, rail depot or otherwise, the waste hierarchy aims to generate the minimum amount of waste.

A common misunderstanding with contaminated land is that it cannot be reused and must be disposed of as hazardous waste. This, however, is not the case as it may still be possible for soil to be reused and recycled – even if there is contamination present.

Reusing material, or transferring material for reuse on another site or depot, is subject to appropriate risk assessment and compliance with the environmental legislation such as carrying out the work under a waste exemption or environmental permit, or using a Materials Management Plan.

This is especially important now that the Environment Agency (EA) and HMRC have paired together to change the landfill tax policy.

Now applicable for waste disposal at any site, including unlicensed landfill sites, landfill tax can be charged to organisations that have reused excavated soils without the full implementation of either a suitable exemption from waste permit or under a fully compliant and declared CLAIRE Definition of Waste Code of Practice (DoWCoP) Materials Management Plan.

Material not directly suitable for reuse – if it is considered contaminated or hazardous – can undergo appropriate treatment to make it suitable, although this outcome must be based upon the outcome of a risk assessment.

Although the waste hierarchy places disposal as the last resort, material cannot always be reused or treated and therefore some waste material needs to be disposed of.

Up until the point where the material is fully intended or required to be discarded, material should not be considered ‘waste’. Once excavated soils and materials are considered to be waste, there is a waste duty of care that requires identifying any hazards and disposing of waste appropriately.

Classifying waste

In order to correctly and legally dispose of waste, it must be classified to determine if the material is hazardous or non-hazardous. As a two-stage process, the soil must first be subject to laboratory analysis; the data of which is then used to classify the material following the procedure in the waste classification technical guidance, WM3.

The List of Waste (LoW) within the guidance outlines a legal classification system for those who need to identify types of waste and their potential hazards. Waste Acceptance Criteria (WAC) testing may also be required.

Chemical analysis – either at an offsite or on-site mobile laboratory – can provide testing to classify the waste and determine the most appropriate way to manage it, either through disposal, storage or treatment.

A mobile laboratory can routinely test for common contaminants such as total petroleum hydrocarbons (TPHs), polycyclic aromatic hydrocarbons (PAHs), BTEX, metals, cyanide and phenol on site, and provides a rapid and cost-effective way to delineate, segregate and classify material on site.

Cost implications of disposing of waste to landfill can be considerable for the developer. Material that is less polluting and is not chemically or biologically reactive – known as inert waste – costs £2.80 in landfill tax for every tonne that is sent to landfill. With hazardous waste costing £88.95 per tonne to be sent to landfill, correctly classifying the waste can save projects significant time and money.

In the same way that chemical analysis determines whether the material is hazardous and supports classifying the waste, soil analysis can also support waste management for the other steps in the waste hierarchy.

Gasworks case study

Developers and contractors need to have the right information about the nature and location of any contamination on their site. This information can ensure remediation work is carried out as safely and effectively as possible.

Previously, SOCOTEC – formerly ESG – delivered on-site waste classification for a former Gasworks site. The site was marked for use as a temporary compound to allow construction of a major infrastructure project and subsequently for a residential housing development.

To classify the waste, SOCOTEC deployed its mobile chemical analysis laboratory for the rapid waste classification of contaminated soils. The mobile laboratory was used to analyse soil samples for the presence of heavy metals and hydrocarbons.

Being on site, the laboratory was able to produce a waste classification within hours of the sample being taken. Hazardous and non-hazardous waste could be segregated without stockpiling material to wait for results.

Following an initial demonstration of method capability, the on-site analysis protocol was approved by the Environment Agency and the landfill operators. Data results from the site laboratory were correlated with data analysed in SOCOTEC’s off-site environmental chemistry laboratory.

For this project, stockpiling material was not practical on site so the unclassified material would have been conservatively disposed of as hazardous waste. SOCOTEC’s on-site analysis added considerable value to the project with the volume of waste disposed of as hazardous reduced by an impressive 90%, saving the client both time and money.

Charlotte Reeve is operations manager for SOCOTEC's contaminated land business

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