Contamination with Claire Chamley of ARUP

Contaminated Land and Landscape Architecture: Challenges, Risks and Smart Solutions

The UK’s long and layered industrial past has left behind more than just historic buildings — it’s also resulted in extensive areas of contaminated land. As landscape architects and developers, we increasingly work on sites where past uses have left harmful substances in the ground, posing risks to people, projects, and the environment.

What is Contaminated Land?

Contaminated land refers to sites where soil, water, or air contains substances that could pose a risk to human health, property, or the environment. These substances can be metallic contaminants, organic hydrocarbons, asbestos (especially in sites developed before 2000), or harmful gases.

This issue is regulated under the Environmental Protection Act 1990: Part 2A and guided by the National Planning Policy Framework (NPPF). Both frameworks require developers to assess and manage contamination risks, ensuring safe, sustainable developments.

Key Contaminated Land Management Steps

Managing contaminated land involves several stages:

1. Preliminary Risk Assessment

A largely desk-based exercise reviewing:

• Historical land use

• Geology and aquifer properties

• Old aerial photos

• Fire safety history

• This stage identifies possible sources, pathways, and receptors — the foundation of any contamination risk model

2. Ground Investigation

Following standards like BS 10175, this stage includes:

• Trial pits (manual or mechanical)

• Window sampling rigs (for shallow conditions)

• Soil, groundwater, and ground gas testing

• Both targeted (specific problem areas) and non-targeted (random sampling for a wider picture) approaches are used

3. Risk Assessment

A tiered process:

• Generic Assessment Criteria (GAC) for general safety levels

• Detailed Quantitative Risk Assessment (DQRA) for site-specific factors

4. Remediation

Solutions are either:

• Engineering-based: soil excavation, containment systems

• Process-based: chemical or biological treatments to neutralise contaminants

• Costs can range from £20–£500 per m³, depending on severity and methods

Sustainability and Brownfield Development

Brownfield sites (previously developed) are preferred for regeneration over untouched greenfield land to support Sustainable Development Goals (SDGs). Good early assessments minimise risks, control costs, and allow for environmental and social benefits, like creating new parks or public spaces.

Case Study 1: London 2012 Olympic Park

An iconic example of land regeneration:

• 150 potentially contaminative past uses identified.

• Historic pollution, bomb damage, and socio-economic challenges.

• Massive ground investigation: 3,500 locations sampled.

• 2.3 million m³ of soil excavated and treated.

• A Global Remediation Strategy (2007) was created, managing risks and setting a template for future urban projects. The London Legacy Development Corporation (LLDC) oversaw post-Games development, though it will soon dissolve, with responsibility returning to local boroughs.

Case Study 2: Greenwich Peninsula

Once home to one of Europe’s largest gasworks, along with tar, chemical, power, and metal works. The north side was worst affected due to tar contamination. Soil, groundwater, and ground gas issues required comprehensive remediation. Statutory remediation (1995–1996) by British Gas, followed by development remediation by English Partnership. Focus on soil re-use strategies — reducing off-site disposal by excavating, segregating, stockpiling, and categorising soils for reuse wherever possible.

Key tools included:

• Environmental Method Statements (EMS)

• Quality Risk Assessment (QRA)

• Sampling Quality Control (SQC)

• Custom tree pit construction details for contaminated areas

• Arup acted as Environmental Management Co-ordinator for this transformative regeneration project

Final Thoughts

Contaminated land is a challenge — but it’s also an opportunity. With smart risk management, clear strategies, and sustainable practices, these former industrial sites can be reborn as vibrant, healthy, and accessible urban environments.

Landscape architects play a vital role in this process, balancing history, ecology, and community needs while safeguarding public health.