NIACE Centre, Belfast, Northern Ireland

Detailed Assessment of Ground–Gas Hazards

Ground-Gas Solutions (GGS) was commissioned by Queens University Belfast to carry out spot sampling, high-frequency bulk gas monitoring, trace gas analysis and a ground-gas risk assessment for the Northern Ireland Advanced Composites & Engineering (NIACE) Centre on part of the Bombardier Estate, Belfast. The site is currently a car park which is part of the Bombardier Aerospace complex. Potential receptors were identified as future site users and buildings.

 

The Investigation

GGS initially undertook a detailed review of available reporting with respect to ground-gas hazards.

 

GGS conducted continuous ground-gas and water level monitoring as a specialist element of the site investigation (conducted by others).

 

The continuous monitoring was completed using GGS’s innovative GasClam^® equipment.  This device takes high frequency (‘continuous’) readings of methane, carbon dioxide, oxygen and some trace gases along with other   environmental parameters, generating a better understanding of the gas regime for interpretation. This information proved to be extremely useful as a more detailed site specific conceptual model was built up and the true gas regime at the site was determined.

 

Risk Assessment and Conclusions

Site Investigation revealed a significant thickness of organic rich soils at the site.  These soils consist of hydraulic fill and estuarine alluvium (sleech) deposits and are the likely sources of hazardous ground-gases, with methane being driven by tidal and pressure changes forming the dominant risk to the proposed development.

 

Ground-gas monitoring of the site indicated very high concentrations of methane and carbon dioxide.

 

The assessment identified the requirement for gas protection measures at the site equivalent to Characteristic Situation 3 (CS3) levels of protection.  However, the building size and type, foundation solution and slab construction require the need for additional active measures beyond CS3.  GGS provided a detailed recommendation on gas protection measures requirements.