Ground gas health and safety monitoring during drilling and grouting of former mine workings

The site comprised a new railway station. As part of the development works, there was a requirement to remediate former coal workings through a programme of drilling and grouting. It was recognised that during these intrusive works, there was a potential risk of hazardous ground gas emissions due to the introduction of preferential pathways and displacement of ground gas.

Prior to commencement of the drilling and grouting, there was a requirement for a safe system of work to be in place to manage the potential ground gas risk. GGS developed a system of control measures for a range of gases of concern, inclusive of RAG ratings and action levels. Subsequently, GGS supported a safe system of work by:

• Providing daily attendance by a gas specialist during intrusive works.
• Undertaking high-resolution gas sweep surveys prior to and post intrusive works on a daily basis, to confirm baseline conditions, ensure a safe working environment and provide an indication of any changes that may be occurring.
• Providing a watching brief during intrusive works, with measurements of ground gas recorded on a regular basis to parts per million by volume level, to provide an early indication of potential hazardous ground gas emissions.
• Provision and management of gas alarms, to provide a warning system and evidence to time weighted exposure.

Outcome

GGS presence on site ensured that a safe system of work was in place to enable the remediation works to safely commence. Daily site records were provided to The Client to provide evidence that a safe system of work was implemented at all times.