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Ground Gas Monitoring & Risk Assessments For Planning Permission And Gas Mitigation

Ground gas monitoring is a critical requirement for many residential and commercial developments, especially on brownfield sites or areas with historic landfills. Hazardous gases such as methane (CH₄), carbon dioxide (CO₂), and hydrogen sulphide (H₂S) can migrate through soil and enter buildings, creating health and safety risks. Local authorities often require ground gas monitoring as part of planning conditions or following a Phase 1 Preliminary Risk Assessment.

When ground gas monitoring is needed - Ground gas monitoring is commonly required when a Phase 1 Preliminary Risk Assessment identifies potential gas sources (e.g. landfills, made ground), planning conditions specify gas risk assessment or when a development is near historic waste sites or organic-rich soils.

Our Ground Gas Monitoring Services

Drilling, monitoring, risk assessments and mitigation - We offer a complete, end-to-end service that combines technical expertise with practical solutions. Our team can handle everything from borehole drilling and monitoring to ground gas risk assessment and mitigation strategy development. We work to the highest standards, following CIRIA C665 and BS8485 guidance, and have a wealth of experience in contaminated land and ground gas risk management. With in-house capabilities and a commitment to compliance, we deliver reliable, cost-effective results that keep projects moving forward.

Detailed reports and clear recommendations -Our reports include detailed monitoring logs, interpretation of gas data, and clear recommendations for mitigation or gas protection measures. Where required, we also provide a Ground Gas Mitigation Options Appraisal & Strategy, or integrate these recommendations into a Phase 3 Remediation Options Appraisal to ensure full compliance with planning and building regulations.

The Ground Gas Monitoring Process

Initial Borehole Drilling and Ground Gas Well Installation - The process begins on-site with the drilling of boreholes to appropriate depths, typically around 5m below ground level, based on site-specific conditions. We install dedicated gas monitoring wells fitted with slotted standpipes, gravel filters, and secure gas valves in accordance with CIRIA C665 and BS8485 guidance. This ensures accurate sampling and long-term integrity of the monitoring setup.

Gas Monitoring Visits - Once the wells are installed, we carry out a structured monitoring programme consisting of six visits over a minimum of three months. These visits are scheduled to capture variations in atmospheric pressure and seasonal conditions, as recommended by UK best practice. During each visit, we measure concentrations of methane, carbon dioxide, oxygen, and other relevant gases, along with flow rates and pressure readings. Optional continuous monitoring systems can also be deployed for enhanced data accuracy and efficiency.

Ground Gas Risk Assessment & Report - After data collection, we interpret the results in line with CIRIA C665 and BS8485, classifying the site's gas regime and assigning a Gas Characteristic Situation (GCS). The findings are presented in a detailed Ground Gas Risk Assessment, which can be delivered as a standalone report or integrated into a Phase 2 Intrusive Site Investigation. If elevated gas concentrations are detected, we provide a Ground Gas Mitigation Options Appraisal & Strategy, or incorporate recommendations into a Phase 3 Remediation Options Appraisal.

For most residential projects, ground gas monitoring involves drilling boreholes and installing monitoring wells across the site, followed by a series of six monitoring visits over approximately three months. This approach ensures that data is collected under varying atmospheric conditions, providing an accurate assessment of gas risk. The results are then compiled into a Ground Gas Risk Assessment, which may stand alone or form part of a Phase 2 Intrusive Site Investigation. Where elevated gas levels are identified, we can develop a mitigation strategy or incorporate recommendations into a Phase 3 Remediation Options Appraisal, ensuring compliance and safe development.

Meet Our Land Contamination & Ground Gas Consultants

Louis Turner, Technical Director - Having graduated from the University of Nottingham with a degree in Environmental Science, Louis is recognised for his technical leadership and precision in environmental consultancy. Louis provides strategic oversight across all service areas, ensuring projects meet the highest standards of compliance, accuracy, and environmental responsibility. Louis directs contaminated land investigations, from desk-based risk assessments to intrusive site surveys. He ensures soil and ground gas analysis is conducted to UKAS-accredited standards, producing clear, evidence-based reports that support planning applications, regulatory approvals, and safe development decisions.

Joe Turner, Operations Director - Providing practical expertise and a client-focused approach, Joe ensures that every project is delivered quickly, efficiently, and without unnecessary hassle. He has successfully managed a wide variety of project types across the consultancy, bringing a wealth of operational knowledge and a reputation for keeping projects on track. Joe's leadership guarantees a smooth process for clients, from initial enquiry through to final reporting. Joe oversees contaminated land investigations, coordinating desk studies, site surveys, and remediation works. His operational management ensures that soil sampling, ground gas monitoring, and reporting are completed seamlessly, giving clients confidence in compliance and project delivery.

Richard Turner, Director - With over 30 years of experience in site development, he provides invaluable insight into pragmatic solutions that balance costs, practicalities, and client objectives. Richard has a detailed understanding of building regulations and a clear sense of what is and isn't possible on site, making him a trusted advisor for developments of all sizes. Richard applies his site development expertise to contaminated land investigations, ensuring that remediation strategies are practical, cost effective, and achievable on site. His focus on feasibility helps clients move forward with confidence.

Request Ground Gas Monitoring

Contact us for an informal discussion about your requirements or, if your requirements are more complex, a more formal consultation may be necessary. Following initial consultation we can provide an outline proposal detailing how we can help and the costs involved. If you're looking for more information about our services or our company then complete the below contact form and we will endeavour to respond to your enquiry in a timely manner, alternatively, give us a call on 0800 433 2906 and our experienced consultants can provide actionable advice and guidance.

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Frequently Asked Questions

How to test for contamination from landfill sites? - Testing for contamination from landfill sites involves a structured risk assessment process, starting with a Phase 1 Desk Study to review historical data and identify potential risks such as ground gas emissions (methane and carbon dioxide), soil contamination, and groundwater pollution. If the desk study indicates possible contaminant linkages, a Phase 2 Intrusive Site Investigation is carried out, which may include soil sampling, groundwater monitoring, and gas monitoring to measure contamination levels against regulatory standards. These assessments consider factors such as the landfill’s age, distance from the development site, capping measures, and gas management systems. This process ensures compliance with the Environmental Protection Act 1990 and helps determine whether mitigation or remediation is required before development can safely proceed.

What is a Phase 2 Intrusive Site Investigation? - Phase 2 Intrusive Site Investigations, noted in the Environment Agency LCRM guidance as the second step of a Stage 1 Risk Assessment, are conducted following the identification of contamination risks at a site that require further investigation in order to quantify. This initial identification is carried out as part of a Phase 1 Preliminary Risk Assessment (Desk Study), which will also outline a scope of work for a Phase 2 Intrusive Site Investigation. Site investigations are likely to include targeted soil or water sampling, with analysis carried out in a UKAS accredited laboratory, and are essential in order to determine whether contamination is present at your site.

What is a Phase 3 Remediation Options Appraisal and Strategy? - Phase 3 Remediation Options Appraisals, referred to in the Environment Agency LCRM guidance as a Stage 2 Options Appraisal, are conducted following the identification of contamination at a site that requires remediation in order to make the site safe for its proposed use. A Phase 3 Remediation Options Appraisal will include a detailed assessment of the feasible remediation options for a contaminated site, these will then be narrowed down to a final selection of the most appropriate and cost-effective options, for which a Remediation Strategy will be produced.

References
British Geological Society. BGS GeoIndex
BSI Group. Code of practice for the design of protective measures for methane and carbon dioxide ground gases for new buildings
CL:AIRE. Category 4 Screening Levels (C4SLs)
Environment Agency. Land contamination risk management (LCRM)
Land Quality Management. The LQM/CIEH S4ULs for Human Health Risk Assessment
US EPA. Regional Screening Levels (RSLs)