Prevalence of CO2 from disused mineral mines and the implications for residential buildings: research

In 2017 the NHS Lothian Incident Management Team investigated reported cases of ill health affecting residents of a recently built local authority housing estate. This research is looking for similar incidents and considers implications for building standards.

This document is part of a collection

7 Stakeholder Engagement

7.1 Stakeholder Engagement Methodology

A project requirement was to engage with LAs, regional NHS boards and other stakeholders to:

  • Collect information on where CO2 mine gas (shale and coal mining) events have occurred since national building regulations came into force (54 years ago)
  • Engage with Local Authorities to find out how they each scrutinise the possibility of CO2 mine gas migration for new development
  • Carry out a review of the guidance available on mine gas mitigation in new developments
  • Hold a stakeholder event to collect views on the questions raised within the research brief and discuss issues arising.

We reviewed the Coal Authority Planning Policy constraints area that highlights the former coal mining areas within Scotland to narrow the selection down to cover only those areas affected. This identified 23 local authorities and 10 regional NHS Health Boards with the potential to be affected by CO2 from disused coal or oil shale mine workings within Scotland.

Figure 7‑1 Local Authority overlay of CA reporting area

Figure 7‑1 Local Authority overlay of CA reporting area

Figure 7‑2 board overlay of reporting areas

Figure 7‑2 board overlay of reporting areas

Having reduced the stakeholder list to twenty-three local authorities and ten NHS board areas, we developed a contact list comprising:

  • LABSS Building Standards Managers List
  • Consultants in Public Health with the 14 NHS Boards Health Protection Teams
  • RSKW/ RSK contacts within LA environmental health departments or contaminated land officers (CLO’s)
  • Local authority planning departments
  • Key additional stakeholders i.e. Coal Authority, BGS CIRIA, CL:AIRE, etc.

Using this list, we were able to contact approximately 130 individuals to whom we submitted:

  • A project introduction outlining the project aims and objectives
  • Their invitation to our CO2 project workshop on 8th November 2018
  • A request for information on previous CO2 incidents
  • A short questionnaire related to the Building Standards questions raised within the Gorebridge IMT report.

7.2 CO2 Mine Gas Workshop

The Building Standards Division requested we organise a workshop to discuss the issues related to the prevalence of CO2 from disused mine workings. The main objectives in addition to raising awareness in this area were:

  • To consider the building standards related questions which were flagged up in the NHS Lothian, November 2017, Gorebridge IMT report
  • To collate information on incidents (other than Gorebridge) where CO2 events have occurred in the past
  • To discuss the degree of scrutiny of the risk of CO2 mine gas migration in new developments.

The agenda for the day, shown in Table 7‑1, aimed to outline the issues and comprised a mix of speakers covering the existing guidance and an overview of the Gorebridge IMT report and its recommendations.

Table 7‑1 Stakeholder Workshop Agenda 8th November 2018


9:00 - 10:00

Opening Remarks

Keynote Speakers:

  • Andrew Gunning RSKW – Objectives for workshop
  • Dr Tom Henman RSK – The Evolution of Ground Gas Guidance
  • Dr Colin Ramsey NHS – The NHS Lothian Gorebridge IMT Report, April 2018.

10:00 - 10:30

Coffee and networking

10:30 - 12:00

Breakout session

Three groups to consider one of the following issues:

  • Group A (Facilitator Andrew Gunning, Partner RSKW)
    • How is the risk of CO2 mine gas migration for new development scrutinised by Local Authorities (topic for all 3 breakout sessions);
    • Key discussion topics: Lessons from the NHS Lothian Gorebridge IMT report and how they might influence a precautionary approach to public health.
  • Group B (Facilitator Stuart Borland, MD RSK Building Sciences)
    • How is the risk of CO2 mine gas migration for new development scrutinised by Local Authorities (topic for all 3 breakout sessions);
    • Energy efficiency and construction factors – could these be contributing to the retention of mine gas in properties.
  • Group C (Facilitator Dr. Tom Henman, Director RSK)
    • How is the risk of CO2 mine gas migration for new development scrutinised by Local Authorities (topic for all 3 breakout sessions);
    • Risk assessment – is the current risk assessment process robust?

12:00 - 12:30

Presentations from each of the 3 breakout sessions / follow up Discussion:

  • Information on incidents (other than Gorebridge) where CO2 events have occurred in the past
  • How is the risk of CO2 mine gas migration for new development scrutinised by Local Authorities
  • Summary of main actions arising: Andrew Gunning RSKW.

12:30 - 14:00

Lunch and networking

As shown in Table 7‑1 Stakeholder Workshop Agenda 8th November 2018 we organised three breakout groups each of which had two issues to address within the allocated time with RSKW providing a facilitator and secretary for each to ensure the discussion moved along and responses were recorded. The format for the workshops comprised:

1. A common question (30 mins)

2. How is the risk of CO2 mine gas migration for new development scrutinised by Local Authorities (topic for all 3 breakout sessions)?

3. A specific topic to explore taken from Annex A of the contract scope, shown in Table 7‑2 IMT Questions to Building Standards Stakeholders, plus opening question(s) to get the discussions going.

Table 7‑2 IMT Questions to Building Standards Stakeholders

IMT Building Standards Questions Group

1/ Is the current mine gas risk assessment process adequate to correctly determine the level of risk, especially in relation to the requirements for assessing mine gas levels at sub‐surface depths likely to be representative of gas migration potential from underground mine sources?

Group C

2/ Is the current risk assessment process fit for purpose particularly in terms of taking account of future potential changes in mine gas dynamics and migration risk factors (e.g. due to ground stabilisation measures, additional developments, etc.) that could lead to an increased risk of gas migration into properties over the long term?

Group C

3/ Is there sufficient emphasis in the current mine gas risk assessment process on the potential for other interventions affecting the soils or substructures underpinning any building development, to alter the risk of mine gas migration and consequently to render any pre‐development assessment redundant and inadequately precautionary to protect public health?

Group A & Group C

4/ Are the current criteria used for deciding what constitutes a sufficiently precautionary approach to mitigation appropriate; particularly where there is known to be a potential risk of mine gas migration? Does the process adequately emphasise the need to take account of construction methods that may add to that risk (e.g. the use of vibro-stone underpinnings or solid slab floors that are not separately vented to the outside atmosphere)?

Group A

5/ In determining the need for mitigation measures, is the current scope for interpretation of the guidance open to developers at present appropriate?

Group B

6/ Are construction methods that do not involve creating a ventilated solum beneath the ground floor of a property inherently more liable to permit the transmission of mine gases to the inside of these properties compared to a traditional ventilated solum construction type?

Group B

7/ Is the drive to improve the energy efficiency of modern properties by increasing the levels of insulation and ensuring they are less prone to uncontrolled air movement (draughts) and are consequently more air tight, a potential factor contributing to the retention of mine gas emissions that manage to penetrate a property?

Group B

8/ Would the simplest and most appropriately precautionary solution to the problems highlighted by the Gorebridge incident be to require mandatory gas risk mitigation measures in all new residential and similar developments in areas of Scotland defined by the Coal Authority as former coalfields?

Group A

The workshop was attended by 42 individuals representing 25 of the key stakeholders as shown in Table 7.3 Stakeholder Workshop Attendees.

Table 7‑3 Stakeholder Workshop attendees

Argyll and Bute Council Environmental Health


Building Standards Division


City of Edinburgh Council Environmental Health

Coal Authority

East Ayrshire Council Building Standards

East Dunbartonshire Council Environmental Health

Falkirk Council Environmental Health

Fife Council Environmental Health

Glasgow City Council Environmental Health

Homes for Scotland

Melville Housing

Midlothian Council Building Standards & Environmental Health



North Ayrshire Council Building Standards & Environmental Health

North Lanarkshire Council Building Standards & Environmental Health

Renfrewshire Council Building Standards

Scottish Borders Council Environmental Health

South Ayrshire Council Building Standards

South Lanarkshire Council Building Standards & Environmental Health

Stirling Council Environmental Health

West Dunbartonshire Council Environmental Health

West Lothian Council Building Standards

A summary of feedback received from the attendees is shown in Table 7.4 Discussion Items from Stakeholder Workshop and in the findings log set out in Annex 3 – Stakeholder Engagement

3(a) Issues log from Stakeholder Engagement.

Table 7‑4 Discussion Items from Stakeholder Workshop

Issues Raised: Stakeholder Workshop 8th November 2018

The themes discussed within the workshop are fully noted in Annex 4 and 3b, the full analysis of the feedback is outlined within Section 9.1. To provide an overview of the views from the attendees we have summarised the discussion points raised under the following key areas:

  • Gas Membranes – concerns over quality of fitting, verification, and their long-term protection
  • Gas Risk Assessments (Conceptual Site Model) – Variability in the quality of the assessments and conceptual site models being submitted. Many lacked the assessment of changing environmental conditions and, due to the development process, omitted assessments of soil stabilisation activities or impact of adjacent sites
  • Gas Risk Assessments (Gas Monitoring) – Insufficient or incomplete gas monitoring, or those which did not include falling pressure events indicative of worst-case scenario
  • Coal Authority – Perceived issues with data availability and accessibility, particularly on a site-specific basis, and benefits of closer collaboration with local authorities
  • Expertise – Local authorities acknowledge coal mine gas risk assessment is a specialist area. Loss of expertise is occurring as staff with mining industry experience retire. Financial constraints limit the use of external expertise to undertake peer reviews of reports submitted under Planning/Building Standards
  • Standards – Generally noted that the production of risk assessments and mitigation measures are targeted to meet the minimum functional standard. Local authorities try to provide a level playing field in interpreting the guidance, but some workshop attendees were not comfortable in determining if the current standards and guidance remain appropriate for mine gas assessment. They felt this area needs additional research and review at Scottish Government level
  • Communication – Some attendees felt their local authority required more of a joined up approach on these issues within departments. In others, they felt they already had this in place. There were some concerns raised on communication relating to planning conditions, gas risk assessments and mitigation measures between Planning, Environmental Health and Building Standards departments within local authorities
  • Ongoing Maintenance – Permitted developments and future maintenance issues that could affect the integrity of ground gas protection measures installed at the time of development.

7.3 Additional stakeholder engagement

Three local authorities have provided more considered responses or further relevant detail to the issues raised in the questionnaire as follows:

  • Midlothian Council – we arranged follow up interviews with their planning teams to obtain further feedback
  • North Lanarkshire Council provided reports related to methane seepages in the Chryston area which were first recorded in 1984
  • Fife Council – their Land & Air Quality Technical Officer provided an additional written submission covering the issues raised and gas protection system verification.

Stakeholder meetings also took place with Northumberland County Council (NCC) and BGS and information was provided by University of Newcastle. Several publications in relation to experience of mine gas in the Northeast of England were reviewed including Sizer et al. (1996) and Robinson (2000).

NCC has extensive experience of dealing with mine gas related issues similar to those recorded in the Gorebridge IMT Report. This has led to increased vigilance regarding the risks posed by CO2 for new developments. Two standard planning conditions requiring ground gas protection have been introduced by NCC as follows:

Condition 1 – Ground Gas Protection:

No buildings shall be constructed until a report detailing the protective measures to prevent the ingress of ground gases, including depleted Oxygen (<19%), to the CS2 standard specified in BS8485:2015 (Code of Practice for the design of protective measures for methane and carbon dioxide ground gases for new buildings) have been submitted to and approved in writing by the Local Planning Authority.

The report shall contain full details of the validation and verification assessment to be undertaken on the installed ground gas protection, as detailed in CIRIA C735 (Good practice on the testing and verification of protection systems for buildings against hazardous ground gases).


In order to prevent any accumulation of ground gas, which may potentially be prejudicial to the health and amenity of the occupants of the respective properties.

Condition 2 – Validation and Verification of Ground Gas Protection:

No building shall be brought into use or occupied until the applicant has submitted a validation and verification report to the approved methodology in Condition 2*, which has been approved in writing by the LPA.


In order to prevent any accumulation of ground gas, which may potentially be prejudicial to the amenity of the occupants of the respective properties.

Information relating to planning appeals concerning the protection for mine gas was also provided by NCC. The first is for the Arriva Garage site in Ashington where the site was developed without the required ground gas protection. Subsequently, the developer installed gas monitors in the areas of concern. The second appeal relates to a housing development near Cambois where the applicant submitted ground gas information which did not cover the low atmospheric pressure events. Subsequently, the developer submitted this information which showed no ground gas issues of concern at the site.

Generally, NCC were concerned about a lack of specific guidance relating to mine gas issues. This was partly negated by good contacts with Newcastle University, particularly Dr Jean Hall, who provided useful background information for this current project. That included several incidents in the Northeast of England related to CO2 from abandoned mine workings. Experience in NCC in dealing with mine gas is extensive and there are also regular contacts with neighbouring LAs in the region. We would recommend further discussion with Environmental Health Officers in NCC who indicated they would find it mutually beneficial. Contact details will be provided to Scottish Government.

A key aspect of the incidence of CO2 related incidents within the NCC area is the presence of shallow mine workings, sometimes only a few meters below ground level.

Consultation with the BGS focussed on the use of environmental data and supporting information to inform planning policy and in particular the issue of providing site investigation and other environmental data early in the planning process (Bonsor, 2018).

Work has been carried out by a sub-group of key agencies in Scotland, to examine what environmental information is potentially relevant to informing preparation of Local Development Plans (LDP), and how this information can be made more accessible.

This could be relevant to identifying within LDP’s areas that may be of high risk of CO2 emissions.

Contacts within the land contamination team at SEPA were also consulted, but they responded that they did not have much to contribute at this stage of the project.



Back to top