Heavy Metals in Contaminated Soils

Metals like lead, nickel and mercury can remain in soil for decades and can create risks to people, controlled waters and the environment. These risks aren’t always obvious, so proper testing and management is essential.

At Provectus Soils Management, we help clients understand why heavy metals occur and how to sample reliably and what to do with impacted soil in a safe and compliant way.

Heavy Metal Soil Testing 

Heavy metal soil testing is a process that is used to find out whether metals are present in soil and at what concentrations. This helps supporting the planning applications and risk assessments. The process of soil testing includes:

• Site review and planning

Before samples are taken, we have a look at the site history and sources that could be likely contaminated. This helps us decide where to sample and what tests are needed.

• Sampling design

Once the risks are understood, a sampling plan is prepared including how many samples are needed, where they will be taken, which laboratory tests are required. On development sites, samples are often taken across proposed areas. If hotspots are suspected, targeted samples are added in those locations, this helps reduce the uncertainty and avoids unnecessary costs later.

• Field Sampling and Handling

The technicians will collect the soil and record the locations carefully and make sure that the samples are tracked. They note down the soil type, colour and any visual or odour indications. The samples are then taken to a laboratory to be analysed.

• Compare results with screening criteria

If concentrations are below the screening level, the risk of contamination is considered low however if they exceed the screening levels, it doesn’t mean the site is automatically unsafe, it means a further assessment will take place to understand the actual risk.

Removal of Soils Affected by Heavy Metals 

Removing soil affected by heavy metals is a controlled process as it must protect workers, prevent pollution and comply with the UK waste law. This process includes:

• Confirm the need for removal

Removal should be based on evidence from heavy metal soil testing and risk assessment. This should be clear on where the metals are present, where they are located on site, the depth and volume of affected soil and the proposed end use of land.

• Define the removal area

Once removal is agreed the affected area is set out on drawings and on site. This includes target depth and any separation between contaminated and clean soils. Setting these boundaries prevents over digging which can increase disposal costs and under digging which leaves contamination behind.

• Prepare a method statement

Before the work is started, a written statement is prepared which covers equipment to be used, segregation of clean and contaminated soils and health and safety controls.

• Excavate and Segregate

During removal contaminated soil is kept separate from the clean material, a visual inspection is carried out to check for any changes in soil type. Segregation can significantly reduce disposal volumes and not all soil on a site will be contaminated to the same level.

• Validate the excavation

After removal, validation sampling is often carried out. Samples are taken form the base and sides of the excavation to confirm that heavy metal concentrations are below the agreed criteria and therefore this provides that the risk has been addressed.

Disposal of Soils Affected by Heavy Metals 

Heavy metal soil testing tells you what is in the soil and at what concentration. If the results show that it cannot stay on site, the next step is disposal or treatment. This is a regulated process under the UK waste law. Here is how disposal works:

• Using testing results to classify the soil

Before any soil leaves the site, it must be clarified. The results from the heavy metal soil testing are then assessed against UK waste guidance to determine if the soil is hazardous and whether it displays any hazardous properties. This stage is important as it dictates which facilities can legally accept the material.

• Identify a suitable permitted facility

Once classified, a suitable disposal or treatment facility is identified. This may include hazardous landfill, non-hazardous landfill, soil treatment centre and stabilisation facility. This can depend on the metal concentrations. In some cases, treatment is possible before final disposal.

• Complete the correct documentation

All soil movements must be supported by the right documentation. This usually includes waste transfer notes for non-hazardous soil, waste classification assessment and laboratory reports. The producer of the waste has a legal duty of care to ensure it is described accurately.

• Confirmation of receipt and disposal

When the soil reaches the permitted facility, it is checked against the paperwork and could be visually inspected. Once it is accepted the receiving site confirms the waste type, disposal is recorded and the data is issued for project records. This forms part of the site’s compliance record and is often required for verification reporting.

Disposal is the final stage in managing contaminated soil, when it is planned properly it becomes controlled and a predictable process.