CO2 mine gas - site investigation and risk assessment: best practice

Report collating current practice in local authorities and provide a summary assessment of options to deliver a standardised ‘good practice’ approach to risk assessment, reporting, mitigation and verification of mitigation measures for mine gas.

This document is part of a collection

4. Detailed stakeholder engagement


4.1 At the outset of the project, it was intended to broadly identify two sub-groups of LAs to take forward to the detailed consultation:

  • Group 1: Local authorities with clear evidence (documented or informal) of working relationships between the EHO/ CLO, Planning and Building Standards. These relationships will be present but may not successfully 'manage' internal dialogue to achieve a consistent and co-ordinated approach to managing the presence of CO2 mine gas on a site.
  • Group 2: Local authorities without any clear or regular working relationship between the EHO/ CLO, Planning and Building Standards. Relationships may be absent, but this does not necessarily mean that there is or will be a failure to manage the presence of CO2 mine gas on a site. Expertise may be present in each of the three departments but with little or no interaction.

4.2 Based on the findings of the online survey, LAs did not always clearly fall into one of the two groups. Responses to Q11, specifically about having an existing framework, was found to vary between respondents at the same LA.

4.3 LAs where one or more respondents indicated they did not wish to participate in detailed consultation (Q30) were not considered for detailed engagement. LAs responding positively to Q30 were therefore broadly assigned to one of the two groups based on Q10, 11 and 17, which focused on working relationships between departments.

4.4 Eight LAs were contacted, with one declining due to current resourcing issues and a second contact not responding despite a number of attempts to engage. Six LAs were therefore taken forward to the detailed engagement. These were:

  • Fife Council
  • Falkirk Council
  • Midlothian Council
  • Renfrewshire Council
  • Stirling Council
  • Glasgow City Council (CLO only)

4.5 Following identification of the six LAs to take forward for detailed stakeholder engagement, a series of nine questions were developed for this phase. The questions for discussion were developed around the requirements of the research project in the tender Schedule 2 – Specification document and analysis of the online survey responses received. The detailed consultation questions are presented in Annex B.

4.6 Virtual conferencing (Microsoft Teams) was used to facilitate the discussion around the questions, which were led by the RSK project team. With the exception of one LA, there were representatives from all three disciplines on each call. With the agreement of participants, the meetings were recorded for reference purposes. This was on the understanding that discussions were undertaken in confidence and responses are not attributed to individual participants or an individual LA and that recordings and notes would not be made available as part of the study.

4.7 Key findings are discussed in the following sections that cover:

  • Interdepartmental relationships, roles and responsibilities (for identifying sites and reviewing of mine-gas related reports) and factors affecting them.
  • Identification / screening of sites for mine gas including data sources used.
  • Document management and information sharing.
  • Specific planning conditions for land contamination and mine gas.
  • Building warrant application requirements and mine gas, and how they are linked with planning applications.
  • Peer review of reports – roles and responsibilities, technical capability.
  • Processes in place to ensure that an amendment to the building warrant for the foundation design does not provide a risk of creating pathways for mine gas, and that decommissioning of gas monitoring well installations occurs.
  • The role of site inspections in verification of remediation to mitigate the risks from mine gas.
  • The need to supplement guidance or technical standards relating to the assessment and mitigation of mine gas risks to development.
  • Examples of good practice or areas of improvement in the processes discussed.

A. Interdepartmental relationships, roles, and responsibilities –

Working relationships

4.8 None of the LAs had a formal written procedure in place identifying specific roles and responsibilities across the three disciplines for the regulation of mine gas risk to development, or wider land contamination issues. This did not preclude effective working relationships between disciplines, which were present at a number of the LAs interviewed.

4.9 Key elements to achieving effective working relationships were trust between colleagues, relationships established over time and the ease with which officers were able to communicate and share information.

4.10 Disciplines being based in the same department (e.g. EHO/ CLO based in a Planning Department) was identified as being of benefit in some LAs. However, no LA identified the separation of disciplines into differing departments or sections within the LA, as being detrimental to having an effective working relationship. Having the same Head of Service across one or more disciplines was not seen as directly relevant to achieving an effective working relationship.

4.11 In one LA with an effective working relationship across all three disciples, all parties agreed this was a direct reflection of the relationship of the EHO/ CLO to either Planning or Building Standards. At this LA it was accepted there was limited direct communication between Planning and Building Standards, but EHO/ CLO facilitated the relationship as a central point of contact. However, in some other LAs consulted, while there is a strong relationship between Planning and EHO/ CLO, this is less so for EHO/ CLO and Building Standards who sometimes operate largely independently.

4.12 A good awareness of mine gas related issues by all three disciplines was identified as important where relationships were effective. This awareness related to the ground conditions (e.g. shallow workings) that were associated with potential mine gas risks, the consequences of not having effective means of regulating development where mine gas is an issue and in relation to the reports submitted as part of the development control process. This awareness was cited by a number of LAs to be directly related to an understanding of the Gorebridge incident and the findings of the resulting IMT report.

4.13 Within LAs where there is a good interdepartmental relationship in place (as agreed by all participants), this was effective where all parties understood which discipline took responsibility for identifying sites where there may be a potential mine gas issue (see Sections 4.20 to 4.33) and for reviewing submitted reports (see Sections 4.16 to 4.19). This effective relationship was supported by shared document management systems, discussed further in Section 4.34 to 4.43.

4.14 In LAs where there was a good level of interdisciplinary working, the EHO/ CLO at some of those LAs had provided internal training to other departments / officers in relation to land contamination. This enabled all those involved to have a better understanding of the subject and reporting requirements, which in turn facilitated effective communication with applicants and their consultants.

4.15 One LA had proactively held regular knowledge dissemination meetings relating to land contamination with some of the more prominent developers in their area. This was considered to have been beneficial in achieving compliance with reporting requirements and the content of submitted reports.

Roles and responsibilities for reviewing of submitted reports

4.16 In all but one LA the EHO/ CLO normally, but not always, took the lead in reviewing the majority of reports. Where the EHO/ CLO consistently took the lead, the exception to this was for review of design reports for gas protection measures. The peer reviewing of reports is discussed further in Sections 4.49 to 4.59.

4.17 The exception to the EHO/ CLO taking the lead was one LA where individual Building Standards officers would make a judgement regarding their own level of technical competency in relation to the submitted report. Consultation with the EHO/ CLO was only undertaken if the Building Standards officer considered this necessary. This approach resulted in potential duplication of the review process and potentially leading to differing review comments being provided to the applicant and their consultant.

4.18 In relation to mine gas, suitability of use under planning is required to be considered under PAN 33 as part of the planning process, which identifies land contamination as a material planning consideration. Building standards mandatory standard 3.1 requires that buildings must be designed and constructed in such a way that there will not be a threat to the building or the health of people in or around the building due to the presence of harmful or dangerous substances. The assessment and mitigation in relation to mine gas should be comparable as it draws on the same underlying technical standards, guidance and codes of practice as referenced above.

4.19 In LAs with an effective interdepartmental, or interdisciplinary, relationship it was clear to all disciplines who took the lead in reviewing all types of submitted reports. This led to consistency in reviewing of reports and comments made in relation to the proposed development.

B. Identification/ screening of sites where there is a potential mine gas issue

Key findings identified

4.20 One of the key elements to effective regulation of potential mine gas issues is the early and accurate identification of developments where there is the potential for mine gas issues, irrespective of who undertakes or leads on that identification.

4.21 With a planning application typically preceding a building warrant application, the identification of sites potentially affected by mine gas normally falls in the first instance to the Planning department. It was evident from discussions that roles and responsibilities were more clearly defined between Planning and the EHO/ CLO, than between Building Standards and the EHO/ CLO. The roles, responsibilities and approach were the same for any land contamination issue and were not specific to mine gas.

4.22 From the consultation undertaken there appears to be at least three methods in place to 'screen' planning applications for potential mine gas issues before deciding who needs to be consulted:

  • Selection of specific applications by Planning Dept. staff for review by EHO/ CLO staff based on GIS data, local knowledge etc.
  • Review of weekly lists of planning applications by EHO/ CLO staff to select relevant applications for peer review.
  • Planning departments consulted the EHO/ CLO on all non-householder applications, with the EHO/ CLO undertaking the identification and confirming when further information (i.e. submission of reports) should be obtained from the applicant.
  • Mandatory submission of desk study / SI reports for all planning applications and peer review of these in advance of determining the application.

4.23 As per the first two items above, some Planning departments initially identified sites potentially affected by mine gas (or other contaminants) for which they requested further input from the EHO/ CLO on. Depending on the data source(s) used by planning when taking this approach (see Figure 3-1) this could lead to sites where there is a potential mine gas issue not being identified to the EHO/ CLO for further consultation. Where the same, comprehensive data sources are shared between the two departments, the identification of sites driven by planning was effective.

4.24 In the case of the fourth item above in Section 4.22, the onus is placed on the applicant to identify if there is a potential mine gas issue. The submitted report (desk study and/or SI report) is then subjected to review. This does still rely on an understanding of mine gas risk assessment to ensure the assessment and conclusions are appropriate and is also potentially more onerous in time and cost for internal or external peer review resources.

4.25 With a building warrant application, the identification of sites was influenced by the interdisciplinary relationship and the overall approach to both applications at the LA. At LAs where effective interdisciplinary relations were present, there was evidence of a technical, scientific and consistent approach to identifying such sites across all disciplines. Once a site had been identified during the planning application this identification was shared with Building Standards (normally through a shared document control system) and the process of identification was not repeated at the time of a building warrant application.

4.26 Where the interdisciplinary working was less effective at a LA, the identification of sites was undertaken separately by Building Standards with limited oversight of decisions that may have already been undertaken by Planning and/or the EHO/ CLO.

4.27 Building Standards, in the absence of GIS, relied on:

  • circulation of a 'weekly list' of building warrant applications to the EHO/ CLO with reliance on them to identify sites. The 'weekly list' includes new applications and amendment applications. The EHO/ CLO will then undertake the identification process using a GIS or the CA interactive viewer.
  • building standards officer judgement, followed by consultation with the EHO/ CLO
  • building standards officer judgement only.

4.28 A shared GIS enables all disciplines to access the same data sources (GIS layer(s)) directly relating to ground conditions assisting in the identification of where mine gas may be a potential issue. These may include CA and British Geological Survey (BGS) data, as well as layers created by LA staff to detail local knowledge. One LA had been particularly proactive in adding data on mineshafts and shallow workings from sources other than the CA.

4.29 The shared GIS is also used for identifying potentially contaminated land unrelated to mine gas. If used effectively, sites can easily and consistently be identified on receipt of a planning or building warrant application. Potential development constraints can be identified, and can feed into the screening process for applications, or when reviewing submitted reports. In some LAs the GIS is inter-related with the LA data management software solution, identifying constraints to the development within a defined distance from the application site that may require further consideration.

4.30 However, understanding the GIS data sources available, and those which would support identification of mine gas sites, is key. The person(s) responsible for the management of the LA GIS data sources should be clearly identifiable, as should the age and provenance of the data sources. This was identified as a data gap at one LA where a GIS was used and shared across disciplines, but no discipline appeared to have ownership of the GIS following reductions in headcount.

4.31 One important finding related to two LAs who accessed limited data sources as part of the identification process, prior to internal consultation with the EHO/ CLO. These were LAs where mine gas issues were not considered to be routinely encountered (although there were noted to be Development High Risk Areas within their areas). Non-householder developments on greenfield sites were considered not to be of concern; a conclusion based on identification of contamination associated with past potentially contaminative activities at a site rather than on the underlying geology. Therefore, applications passed to the EHO/ CLO for additional technical input may fail to include all sites with potential mine gas issues.

4.32 Local Authorities who appear to be identifying sites effectively where there is a potential mine gas issue, are achieving this by: accessing a GIS with appropriate data sources; routinely using the CA interactive viewer to identify sites; or putting the onus on applicants to demonstrate through desk study/ SI reports whether or not this is an issue requiring assessment.

4.33 The identification of sites was undertaken only once at the planning application stage, with the findings being shared with (or accessible by) Building Standards. All disciplines at these LAs had a clear understanding of the risk drivers for developments where there may be a mine gas issue.

Document management and information sharing

4.34 Some but not all of those LAs with clear evidence of effective working relationships between the EHO/ CLO, Planning and Building Standards also had shared document management systems. Where there was an effective working relationship, but no shared document management system, reports and peer reviews were proactively shared and stored separately by each discipline. Such shared systems used by LAs are commercially available and those referred to included Oracle and Northgate M3PP.

4.35 These systems have modules for each discipline, linked through a property gazetteer. When all disciplines have access to each other's modules, they can readily access submitted reports and comments made in relation to those reports. In addition, all parties can view related documents for the planning or building warrant application. This enables more efficient working and consistency between departments.

4.36 Building Standards officers, on receipt of a building warrant application, are able to check that (i) a planning application has been made, (ii) what relevant information has already been submitted and when (e.g. report versions) and (iii) what comments have been made in relation to those reports. This can avoid duplicating reviews and can ensure that the approach to regulation and enforcement in relation to potential mine gas risks is considered during the development control process.

4.37 In LAs where there was no shared document management system, staff from different disciplines have to work harder to share relevant information. In some of these LAs sharing submitted reports, and review comments in respect of those reports, was ad-hoc and often not undertaken. In the absence of clear roles and responsibilities, combined with shared document management systems, the same report could be reviewed by different officers with differing interpretation and comments presented to the applicant.

C. Specific planning conditions for land contamination

Key findings identified

4.38 The detailed engagement focused on developments where planning permission is required, with only limited discussion relating to householder permitted development rights. However, concern was raised by some consultees that this places a greater onus on the building warrant process with the shorter timescales for processing applications not typically compatible with those for undertaking ground gas monitoring and assessment.

4.39 The use of standard (generic) and mine gas specific planning conditions were considered as part of the online survey (see Section 3.5 to 3.26). Standard conditions require the submission of reports (see Section 1.50 to 1.56) relating to land contamination in the broadest sense, commencing with a desk-based review of potential constraints to development, through to intrusive site works and risk assessment, remediation and verification.

4.40 During the detailed engagement no LA stated they routinely used mine gas specific conditions. However, bespoke planning conditions were used by one LA specifically in relation to a geographic area where minimum gas protection measures were requested on all new build developments (equivalent to Characteristic Situation 2 under BS8485 (BSI, 2019)). A full intrusive site investigation and mine gas risk assessment were still required by that LA, irrespective of the mandatory requirement for gas protection measures in the defined geographic area.

4.41 One LA applied standard land contamination planning conditions to all non-householder new build developments. This is broadly comparable to the approach taken by another LA (not taken forward to detailed consultation) where a desk study and/or SI is required prior to determining the planning or building warrant application for all residential development.

4.42 None of the consultees felt that mine gas specific planning conditions were required except in very specific circumstances. Standard planning conditions, provided it was clear to the applicant what was required in relation to those conditions, were adequate to cover mine gas related issues. A number of the consultees commented that the current trend is toward simplifying the use of generic conditions and Planning departments are often resistant to application-specific conditions. At least one consultee felt that standardising planning conditions across all local authorities in Scotland would be beneficial in terms of consistency and creating a level playing field for all stakeholders.

4.43 A key point (discussed further in Sections 4.71 to 4.74) related to the LA being able to provide supporting guidance documents to the applicant/ consultant in relation to what was specifically required in relation to mine gas. This discussion primarily focused on the decommissioning of gas monitoring well installations. CL:AIRE (2021) guidance document good practice for risk assessment for coal mine gas emissions does fulfil this need and includes detailed guidance on site investigation and risk assessment, as well as the importance of decommissioning site investigation monitoring wells.

Building warrant application requirements and mine gas

4.44 In relation to building warrant applications, the detailed engagement focused on new developments, with only limited discussion relating to extensions or other minor works. Reports evidencing compliance, at the design stage, with mandatory standard 3.1 are submitted in advance of the building warrant being granted.

4.45 Local Authorities varied in the reports required to support a building warrant application, with the majority routinely requiring a desk study, and SI and remediation strategy reports as relevant. One LA focused more on the submission of geotechnical reports rather than geo-environmental reports where mine gas (and land contamination) would be considered.

4.46 Where there were effective interdisciplinary relationships and the sharing of reports, the relevant information relating to mandatory standard 3.1 that had already been submitted in connection with the planning application was accessed by Building Standards at the time of the application. Where a LA did not have shared document management systems, the reports were requested again by Building Standards. Two Building Standards departments requested the submission of a desk study to accompany the building warrant application as a default.

4.47 In a number of the LAs consulted there is no formal check on receipt of a Building Warrant application that there is a linked planning application.

4.48 It was acknowledged by a number of LA consultees that if Building Standards relied on previously submitted reports (i.e. to Planning) these may no longer be current if time has elapsed or if assumptions made about building design had changed.

Peer review of reports

4.49 The discipline reviewing reports varied depending on the relationship between Planning, the EHO/ CLO and Building Standards. No Planning Department took responsibility for reviewing submitted reports, always delegating this to the EHO/ CLO. In LAs where there was a good level of interdisciplinary working, responsibility for reviewing the majority of submitted reports was allocated to the EHO/ CLO by either Planning or Building Standards. Where there was a lower level of interdisciplinary working, the Building Standards officer made the decision if reports were delegated to the EHO/ CLO to review or reviewed internally.

4.50 For at least two LAs the EHO/ CLO reviewed each report in accordance with a structured review template, summarising the data presented and identifying any aspects that required further clarification. Where the EHO/ CLO reviewed the submitted report, they would advise Planning of the suitability of the submitted reports in relation to the planning application or appended planning conditions to the Decision Notice. This review would be electronically filed, associated with the planning application and property gazetteer reference. The report and review would be accessible to Building Standards as, and when, a building warrant application was made.

4.51 One LA sought external peer review for all submitted reports and other LAs are known to do this also. This was to ensure consistency in the reviews and the required level of technical expertise to review those reports.

4.52 During some interviews, the EHO/ CLO was specifically asked, when reviewing reports, if mine gas migration to existing off-site receptors was specifically considered. This included consideration by the environmental consultant within the submitted report, and also consideration by the EHO/ CLO reviewing the submitted report. The consideration of off-site receptors was rarely seen in reports. The impact of a development, through the development itself or preparatory enabling works, on gas migration is not a frequent occurrence. However, when this occurs the potential risks can be significant. The previous report (SG, 2019a) also identified that off-site gas migration was an area currently lacking in detail within a risk assessment.

4.53 In LAs where there were gaps in interdisciplinary working, in some cases Building Standards would request review of relevant reports by the EHO/ CLO. In others, reports were accepted by Building Standards without review or were reviewed by the Building Standards officer if they considered it was within their level of competency.

4.54 Design reports and associated drawings prepared to detail proposed gas protection measures in accordance with BS8485 (BSI, 2019) reports were specifically discussed with all LAs consulted. Such reports can be complex, require an understanding of foundation and building design and how this interacts with mitigation needed of identified mine gas risks.

4.55 It was found that design reports were not consistently requested or submitted when gas protection measures were identified as being required. This may be due to a lack of awareness of applicants and their consultants in relation to BS8485 (BSI, 2019).

4.56 The detailed engagement interviews also identified there was inconsistency and uncertainty within a number of LAs regarding the discipline taking responsibility for the review of design reports.

4.57 In some LAs the EHO/ CLO felt competent to review design reports up to a certain complexity (e.g. standard building details, Characteristic Situation 2 only), whereas others felt that this should be the role of Building Standards due to their greater understanding of foundation and building design. One LA stated that if the reports were complex, they sought external peer review of the report.

4.58 However, not all Building Standards officers interviewed felt they had sufficient competency to review design reports. In some LAs if design reports were submitted, they were not reviewed in detail, with reliance placed on the applicant's design engineer to have appropriately designed and specified gas protection measures, installation and verification plans.

4.59 Verification reports demonstrating that the gas protection measures have been installed and verified appropriately were consistently required and reviewed in many LAs in relation to discharge of relevant planning conditions. One LA Planning department did not always ensure a verification report was submitted and did not proactively monitor compliance with planning conditions in this regard, which would appear to be a gap in regulation of mine gas risk.

The role of site inspections in verification of remediation to mitigate the risks from mine gas

4.60 With respect to Building Standards there were differing views with two LA departments stating that they did not routinely require the submission of a verification report, relying instead on officer inspections. This is in contrast to the initial consultation which indicated reliance on the verification report, sometimes supplemented by site inspections. Some consultees also felt that verification reports couldn't be used as supporting evidence for a Completion Certificate submission. This is possibly because verification reports are not covered within the technical handbooks.

4.61 Where there was a good level of interdisciplinary working, the reports submitted, and reviews of those reports, were shared between Planning and Building Standards. In LAs where there were gaps in interdisciplinary working, verification reports were not routinely shared between departments. This can lead to reports being required to be submitted twice, and the applicant potentially being presented with differing or conflicting comments on the report.

Processes in place to ensure that an amendment to the building warrant for the foundation design does not provide a risk of creating pathways for mine gas

4.62 Foundation design is not always known, or may be incomplete, at the time of the planning application and submission of the mine gas risk assessment (contained within a SI report) and related remediation strategy. Changes to foundation design may have implications for the previous prepared and approved SI report and remediation strategy via the creation of preferential gas migration pathways. Furthermore, mine grouting/ stabilisation works at a site may alter the ground gas regime, the implications of which may not have been considered fully at the time of preparing the SI report and/or remediation strategy. This was specifically cited by one LA where, following consultation, the CA required specific ground stabilisation works. This then had resulting implications for the ground/ mine gas risk assessment prepared on the basis of no ground stabilisation works.

4.63 Foundation design changes can occur before the building warrant application is made or during construction (i.e. after issue of the Building Warrant). It is noted that significant changes to foundation design are not common but can have significant implications in relation to gas migration when they do occur (such as cited in the Gorebridge IMT report).

4.64 Such design changes should come to light during the building warrant application process. However, it is also possible that an amendment to the foundation design is only identified by Building Standards at the time of the Completion Certificate submission. The onus is on the applicant for the Completion Certificate to ensure mandatory standard 3.1 has been satisfactorily complied with. The LA verifier will make reasonable enquiry to that effect.

4.65 All LAs consulted agreed that identifying foundation amendments in relation to potential mine gas risks could be missed as was identified as a factor in the Gorebridge incident. Identifying such amendments is important to ensure that any implications for the mine gas risk assessment are considered and any changes required to the design of gas protection measures have been identified and appropriately designed (or redesigned). On receipt of an application to amend a building warrant, the Building Standards officer would need to be aware of the potential implications for mine gas issues previously identified, and action that accordingly. If the EHO/ CLO was consulted on all amendment applications, it would be time consuming to cross reference these with previous applications where mine gas issues had been identified. This is where the design reports and verification reports should ensure that gas protection measures have been designed and installed appropriately.

D. Decommissioning of gas monitoring well installations or other boreholes

Key Issues identified

4.66 Gas monitoring wells, installed as part of intrusive site works for geo-environmental, geotechnical or mining purposes, can create preferential pathways for gas migration from workings at depth to the surface or near surface, and from there to ingress into buildings. This was identified as a factor in the Gorebridge incident and cited in the Gorebridge IMT report.

4.67 It is therefore good practice for the decommissioning and sealing of gas monitoring wells to be discussed in the remediation strategy with evidence of this having been completed being presented in the verification report.

4.68 However, guidance documents discussing this in relation to gas migration are very limited. Those LAs that sought decommissioning on a site-specific basis stated that it was often hard to justify this to an applicant and their consultant without guidance to refer them to setting out the rationale for this. SEPA (undated) and Environment Agency (2012) guidance on decommissioning redundant boreholes and wells are focused on the protection of groundwater only.

4.69 Decommissioning of monitoring wells was routinely required by two LAs when it was identified the monitoring wells could act as a preferential pathway for gas migration. Others were unaware of this good practice approach in relation to mine gas, with one LA stating in the absence of supporting guidance it was regularly very difficult to persuade applicants and their consultants of the need for decommissioning. If decommissioning was undertaken or proposed to be undertaken, several LAs cited the difficulty of locating all monitoring wells and hence a failure of the developer to be able to undertake complete decommissioning across a site. The CL:AIRE (2021) Good practice for risk assessment for coal mine gas emissions has since been published and includes reference to the need for decommissioning of site investigation wells in the watch note of Section 12.2 on site investigation and reiterates this within its key conclusions and recommendations. This should hopefully provide sufficient weight to persuade applicants of the need to decommission wells.

4.70 No LAs required decommissioning as part of a mine gas specific planning condition. This was required as part of the remediation strategy, with supporting evidence provided in the Verification report.

E. The need to supplement guidance or technical standards relating to the assessment and mitigation of mine gas risks to development

Key issues identified

4.71 Consultees were asked about whether they felt there was a need to update existing land contamination technical guidance, supplementary planning guidance or the Building Standards technical handbooks (domestic and non-domestic; SG, 2020b) in relation to mine gas issues. It is noted that the more recent June 2023 editions of the Building Standards technical handbooks still do not include any guidance or reference to mine gas (or ground gas).

4.72 Additional technical guidance is required in relation to mine gas risk assessment. This issue was not considered in detail as it was covered in the 2019 research report (SG, 2019). As noted previously, the CL:AIRE (2021) Good practice for risk assessment for coal mine gas emissions has since been published and includes detailed guidance specific to mine gas investigation and risk assessment.

4.73 Where a LA used the EPS (2019) 'Land contamination and development guidance' there was a consensus that additional sections relating to mine gas would be beneficial to all parties involved in the development process. Currently guidance on mine gas risk assessment, and on decommissioning of gas monitoring well installations was agreed by all LAs consulted to be limited. Where a LA had internal Supplementary Planning Guidance prepared relating to land contamination, it was agreed these could benefit from the inclusion of mine gas. However, it is noted that support may be needed for LAs to draft relevant sections and ensure consistency in the approach across Scotland.

4.74 All LA consultees agreed unanimously that additions to the two Building Standards technical handbooks were required in relation to mine gas (and ground gas). With regard to mandatory standard 3.1 some were of the view that the technical handbooks are not adequate given that they do not mention mine gas or even ground gas. Some consultees commented that the lack of specific reference to ground gas in the technical handbooks has led to push back from developers when more information is requested in support of a building warrant. With 2023 updates to the technical handbooks continuing to omit mine gas and ground gas, this issue persists.

4.75 As a minimum some consultees felt that the technical handbooks should refer to key technical standards and guidance, e.g. BS8485 (BSI, 2019), CIRIA (2007, 2014) C665 and C735. Clarity on what is required for verification to support acceptance of the completion certificate, including the value and importance of the independent verification report required to comply with BS8485 (BSI, 2019) / CIRIA C735 (2014). The consultees acknowledged that there was a balance to be achieved between being overly prescriptive and ensuring the required information was submitted in relation to mandatory standard 3.1.

Examples of good practice or areas of improvement in the processes discussed

4.76 In summary, areas of good practice identified in the detailed consultation phase are as follows:

  • Clearly defined roles and responsibilities, in relation to mine gas and development control. Understanding of each other's roles and overlapping areas of technical capability leads to effective regulation.
  • One of the key elements to effective regulation of potential mine gas issues is the early and accurate identification of developments where there is the potential for mine gas issues. The shared GIS is also used for identifying potentially contaminated land unrelated to mine gas.
  • Relevant datasets that are up to date and held in shared GIS are used to identify/ screen sites, and all officers are aware which are applicable to understanding potential mine gas issues.
  • A shared document management system leads to effective regulation of mine gas issues.
  • Linking Building Warrant applications to planning applications supports the consistency of regulation and avoids duplication of effort.
  • Peer review of all submitted reports, with the exception of design reports, (using a structured review template) is led by the EHO/ CLO.
  • Where needed, relevant planning conditions are agreed between the Planning Officer and the EHO/ CLO.

4.77 Areas for improvement identified are:

  • Reports that cover suitability for use and mandatory standard 3.1 should only be subject to peer review by one discipline, with consistent comments being returned to the applicant/ developer.
  • Consideration of off-site receptors is an area currently lacking in detail within mine gas risk assessments.
  • There is a lack of awareness, and technical capability, in some LAs in relation to peer review of design reports for gas protection measures.
  • Decommissioning of gas monitoring wells is poorly understood by applicants/ developers/ consultants. There is a lack of technical guidance with regards to decommissioning requirements.
  • Additional technical guidance is required in relation to mine gas risk assessment.
  • Planning guidance and Building Standards technical handbooks require additional information on mine gas risk assessment.
  • The use of radon maps for the identification of potential mine gas issues is not considered to be a suitable line of evidence.



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