Case Studies

Analytics & Under-Floor Gas Monitoring as a Building is Converted to Commercial Use

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Our Solutions

  • Continuous monitoring of the gas below the floor slab via a Vapour Pin installed through it
  • Ambilytics:  Data Analytics (used as part of a robust assessment of the historical information, ground investigation and coal mining data by the consultant)

Challenge

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.

Approach

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.

Client Benefits

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.

Results

  • Demonstrated that there was no risk of mine gas emissions to the building and avoided the need to install costly retrofit gas protection measures.

WOW! This article was amazing - I want to read the next one as soon as it's written

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Steve Wilson

Steve specialises in the investigation, assessment and mitigation of ground gas and hydrocarbon vapours and is an Accredited Risk Assessor (ASoBRA) for permanent gases and vapour intrusion (he also acts as a scrutineer for the scheme) . He has written several key technical papers on this subject and has contributed to recent CIRIA, British Standards and Chartered Institute of Environmental Health guidance on ground gas assessment and mitigation. He was a member of the drafting committee for BS8567, Guidance on sampling of ground gas and the 2015 update of BS8485 on gas protection design (with 2019 amendment). He advises local authorities in the UK on planning, Part IIA and other issues relating to ground and landfill gas. He has completed several Part IIa risk assessments in relation to the risk of gas migration from landfill sites towards existing buildings, including options appraisals and mitigation design. He has designed numerous vent trench and barrier systems to prevent ground gas migration. He has recently completed work into the effects of flooding on landfill gas risk and looking at landfill permit surrender guidance in the UK. Steve has acted as an expert witness in court cases involving landfill or ground gas migration in the UK and Australia and for a site in Bangladesh where a gas exploration well had blown out. He has been involved in the design of gas and VOC mitigation measures for sites around the world affected by gas from various sources including mine workings. This has included retrofit schemes for existing buildings affected by gas ingress. He also provides expert support on ground gas to several Licensed or Accredited Contaminated Sites Auditors in Australia.