A Ground Gas Risk Assessment evaluates the presence and concentration of gases within the ground that could affect future development. This usually involves installing dedicated gas monitoring wells as part of the ground investigation process, which helps minimise time and cost. Engineers then carry out a series of monitoring visits over a defined period, typically between four and six visits, depending on the expected gas conditions at the site.
A Ground Gas Risk Assessment is required for sites where ground conditions may generate hazardous ground gases. Sites requiring ground gas risk assessments are often affected by historical coal mining, landfills or infilled ground, either on or near to the site.
If the Phase 1 Desk Study identifies a very low risk, a forensic assessment may be completed instead. This can be carried out alongside chemical testing during the site investigation and often removes the need for full monitoring. This approach can significantly reduce programme duration and overall cost.
If required by planning, a detailed ground gas risk assessment must be completed. The results are presented in a formal Ground Gas Risk Assessment report. This identifies whether ground gas protection is required and specifies appropriate measures for the proposed development.
Where the risk is negligible, no protection is needed. If the risk is low or higher, appropriate mitigation measures must be incorporated into the design.
These may include sub floor ventilation or other engineered protection systems. Early completion of the assessment ensures these requirements can be integrated into the design programme efficiently and without delay.
IGE specialises in the design and verification of ground gas protection measures, with Specialist in Gas Protection Verification accreditation from CL:AiRE.
