A planning application was made to change a warehouse, located on the site of a former colliery, into a leisure facility. However, the building was thought to be very close to an old mineshaft and the local authority raised concerns about potential mine gas emissions from the shaft. The building was due to open so a quick resolution to this issue was needed.
A comprehensive desk study investigation by the consultant identified the old shaft and found that it was further away from the building than previously thought and that the Coal Measures were capped by Glacial Till. This would limit the risk of gas emissions from the shaft reaching the building. Furthermore, the groundwater levels in the area were known to be fully recovered and the former deep workings were flooded.
Continuous monitoring of gas concentrations immediately below the concrete floor slab was completed via a vapour pin installation. This allowed sufficient data to be collected over a short period including suitable drops in barometric pressure which is the key driver for mine gas risk in this site.
The continuous monitoring data collected by the Ambisense units was analysed using the Ambilytics platform and provided evidence that there was no risk of carbon dioxide emissions occurring from the shaft and affecting the building. The correlation plots, heat maps and 1D partial dependency models generated by the platform showed the absence of correlations. When combined with the other information sets for the site it helped provide multiple lines of evidence, all showing no risk from mine gas.
The end result was approved by the local authority and the facility was able to open on time and without the need to retrofit costly gas protection measures. Thus, the Ambisense units and the Ambilytics analysis paid for itself.