Landfill Gas Risk Assessment

Landfill Gas Risk Assessment UK for Planning and Building Safety (BS 8485, CIRIA C665 Aligned)

A Landfill Gas Risk Assessment evaluates the risk from methane, carbon dioxide and ground gas vapours to proposed buildings and occupants. Where development is near landfills, infilled ground or other gas-generating sources, planning authorities commonly require evidence that gas risks are understood and that appropriate protective measures will be installed and verified. A defensible assessment provides the basis for gas monitoring, risk classification, and specification of gas protection measures suitable for building control and condition discharge.

When a Landfill Gas Risk Assessment Is Required

Landfill gas assessments are typically required where:

• Development is proposed on or near a landfill, infilled ground or made ground with gas potential
• A planning condition requires ground gas monitoring and risk assessment
• There is uncertainty around historic waste tipping, backfilled ground or groundwater interaction
• Basements, voids or confined spaces increase gas ingress risk
• Stakeholders require BS 8485-aligned design specification and verification pathway
• Transaction due diligence requires defensible gas risk evidence

Purpose of a Landfill Gas Risk Assessment

The purpose is to determine whether gas protection is required, what level of protection is appropriate, and what evidence is needed to verify installation and performance. A strong assessment reduces over-design cost, prevents unsafe under-design, and supports efficient approval through planning and building control.

How Landfill Gas Risk Assessment Works in Practice

Landfill gas risk assessment typically includes:

• Conceptual Site Model defining sources, pathways and receptors
• Ground gas monitoring (methane, CO2, flow, pressure) and interpretation of variability
• Risk characterisation using guidance-aligned approaches (gas screening values, characteristic situations)
• Protection recommendations (gas membranes, ventilation, sub-floor systems) aligned to risk
• Verification requirements (inspection, photos, integrity testing, validation reporting)

Standards, Guidance and Regulatory Context

Landfill gas risk assessments commonly align to BS 8485: Protective measures for methane and carbon dioxide ground gases, CIRIA C665: Assessing risks posed by hazardous ground gases to buildings, and Land Contamination: Risk Management (LCRM) from GOV.UK.

What the Service Delivers

• Landfill gas risk assessment report suitable for planning and stakeholder review
• Ground gas monitoring scope and programme (where required)
• Risk classification and protection recommendations aligned to BS 8485/CIRIA approaches
• Clear gas protection specification intent and verification pathway
• Condition discharge support and evidence structure (including validation requirements)

What We Need From You

• Site boundary and proposed layout (including foundations, basements, service routes)
• Planning condition wording and programme (monitoring periods, determination timeline)
• Historic information and any existing gas data or ground investigation reports
• Proposed building use and sensitivity (residential, commercial, mixed-use)