Carbon dioxide ingress into residential houses at Gorebridge in Midlothian, Scotland, United Kingdom

Le résumé fourni par la source

Problem In March 2014, NHS Lothian setup an Incident Management Team (IMT) to investigate carbon dioxide (CO2) migration into houses in a local council estate. The estate was built above abandoned mine workings with unstable and insufficient rock in places. Migrating mine gas presented a risk to public health that required intervention. Description The investigation aimed to assess health risk, protect public health, scope the issues and define options to address short and long-term health risk using the source-pathway-receptor model. This required a systematic literature review; review of land-use history, previous site investigations and background reports from Midlothian Council; independent expert advice; radiocarbon analysis of gas samples; CO2 gas monitoring in the affected houses, surveillance of residents’ use of health services and health needs assessment. Results 22 of the 174 residents, in the affected area contacted healthcare services between September 2013 and September 2014 with complaints of headaches, dry coughs, dizziness and anxiety. Radiocarbon analysis identified geological CO2 in the houses that was similar to that originating from the mines. The most likely source of the gas was abandoned coal workings with oxidising coal deposits. Atmospheric pressure changes amongst other factors caused surface migration of CO2. Potential pathways included ungrouted disused mine shafts, natural ground cracks, investigation drill holes, grouting work for the Borders rail link, deep drainage installations, ground stabilisation grouting and foundation vibro stone columns. Lessons This was a rare, complex, large-scale and costly environmental public health incident. Midlothian Council demolished all 64 properties to safeguard the health of the residents. Setting up of a care-for-people group was helpful in addressing the residents’ immediate need and their subsequent resettlement. Key messages: Inadequate remedial work prior to construction and the lack of gas-proof membrane resulted in CO2 seeping into the houses. Gas protection measures are needed in houses built on old mine workings. Mine gases are a potential hazard across similar sites in Scotland and other parts of the world with old mines. Detailed risk assessment is essential prior to construction on such sites.

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