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

1. Context

Project background

1.1 The current research project follows on from and implements some of the findings of a previous research project on the prevalence of carbon dioxide (CO₂) derived from disused mineral (coal) mines and the implications for residential buildings. This project was delivered by RSKW (part of RSK Environment Ltd.) and the report 'Research project to investigate prevalence of CO₂ from disused mineral mines and the implications for residential buildings' was published by the Scottish Government in September 2019 (SG, 2019a).

1.2 The 2019 research report arose following a number of cases of ill health recorded in April 2014 affecting some residents in the former mining area of Gorebridge, Midlothian. An Incident Management Team (IMT) was set up by NHS Lothian to investigate the cases. It was discovered that the residents had been suffering from health issues related to CO₂ exposure. Radiocarbon analysis indicated that the CO₂ was derived from a geological origin indicating that old coal mines were the root cause. Recommendations were made by the IMT to the Scottish Government, some of which relate to Building Regulations.

1.3 The 2019 research report identified a number of options for further consideration to address the issues raised in the Gorebridge IMT report and those gathered in evidence during stakeholder and expert consultation in the previous research project. The specific items to be taken forward within the current research project, are:

• 'Option 4: Improve co-ordination and communication between planning, Building Standards and Environmental Health Officer / Contaminated Land Officer or similar (EHO/ CLO) staff in some local authorities and provide additional budget for training or external specialist support where needed.

Option 4 will in turn support Option 1:

• Option 1: The use and enforcement of model planning conditions as well as changes to Scottish Planning and Building Standards and guidance to cover adequate assessment of mine gas (including worst-case conditions) should be considered.'

1.4 The 2019 research report identified that current standards and guidance documents were limited in their coverage of specific factors relating to mine gas risks associated with development, as opposed to other sources of ground gas. Furthermore, the 2019 research report identified that EHO/ CLO staff felt they had a lack of experience and expertise in relation to the potential risks posed by CO₂ mine gas.

1.5 Of those participants in the 2019 research project, there was a general consensus that submissions in relation to ground gas (which typically include mine gas in affected areas) were highly variable and often failed to consider temporal and/ or cumulative effects. During a stakeholder workshop held as part of the 2019 research project, 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.

Project requirements

1.6 The research project requirements were set out in the contract award letter issued by the Building Standards Division (BSD), Scottish Government, to RSK on 9 December 2020, and a subsequent update to the research project prior to publishing was set out in meetings and correspondence during November and December 2023.

1.7 The remit of the project, as established by BSD, relates to CO₂ (coal) mine gas only and the associated potential risks to development. The Gorebridge IMT report uses the term 'mine gas' within their report when discussing just carbon dioxide. Within this project, the focus has been on CO₂ from mine workings, but we have also considered the related issues from coal mine gas generally. Furthermore, the authors recognise that some of the issues under consideration may have a wider bearing on the regulation of other sources of ground gas and land contamination of which mine gas is a sub-set.

1.8 This report considers the regulation of risks of mine gas to development associated with former coal workings. The findings may also be relevant to mine gas from other types of mining, e.g. oil shale or mineral mines, as well as wider ground gas/ land contamination issues. Consideration of risks under current use (for example under Part IIA of the Environmental Protection Act 1990) is out with the scope of this project. This issue was considered within the scope of the 2019 research report (SG, 2019a)

1.9 The project comprises three main stages:

• Stage 1 - Project Start Up
• Stage 2 – Stakeholder engagement
  • Stage 2a/b: Online survey with 23 Local Authorities (LAs) and analysis of findings
  • Stage 2c/d: Detailed stakeholder engagement comprising interviews with up to eight local authorities and analysis of findings
  • Stage 2e: Interim reporting
• Stage 3 – Review of findings with LAs and final reporting

1.10 The following sections sets out the main requirements of each project stage.

1.11 The final project output was to document our findings and further options for consideration/research, as detailed in this report. In addition, there has been a further stage completed to review and update the report in December 2023 in advance of publication.

Stage 1: Project start up

1.12 In Stage 1 a project inception meeting was attended to define, clarify, and agree the project scope, objectives and delivery deadlines. The relevant stakeholder organisations, i.e. the 23 LAs previously identified to be located within coal mining affected areas of Scotland (SG, 2019a), were also agreed at this time. Stakeholders within these LAs were identified to be staff in Environmental Health/ Contaminated land officer (CLO) roles and in Planning/ Development Management and Building Standards departments.

Stage 2: Stakeholder engagement

1.13 In Stage 2 an online survey was developed to seek views from the stakeholders on a range of relevant issues. The issues included how the different stakeholders engage internally to share information and seek specialist advise on mine gas issues, the technical guidance they refer to and how mine gas issues are regulated under the planning application and building warrant application processes.

1.14 For this task a request was sent out by email to one or more contacts within each of the three disciplines (Environmental Health, Planning, Building Standards). This contained a link to an online survey comprising 30 questions.

1.15 Based on the findings of the online survey, interviews were planned with up to eight LAs, where possible with representatives from all three disciplines. The first aim of this stage was to understand in more detail how the internal relationships work in the context of regulating the potential risks from mine gas to development and any limitations; the second aim was to identify evidence of common practice, good practice, and any gaps with regards to the regulation of development where there are potential risks associated with mine gas.

1.16 Following the completion of the stakeholder engagement and analysis of the findings, an interim report was produced (this report).

Stage 3: Review of findings and reporting

1.17 Following on from Stage 2 and the preparation of the interim report, Section 5 of the interim report, alongside Annex C and Annex D, were issued to all participants in the detailed engagement interviews to seek their feedback. This comprised the six LAs involved in the detailed consultation phase.

1.18 Comments received from the LAs were collated and incorporated into the final report where considered relevant to do so. A summary of the feedback is included as Annex E to the report.

1.19 Following this a final report has been prepared considering comments made on the interim report and associated Annexes from LAs, where appropriate.

Legislative context

1.20 The regulation of land contamination issues in relation to proposed development, which includes risks associated with mine gas, is overseen by LAs through Planning and Building Standards. In order to provide context of the various roles, we set out below the key elements of the Planning and Building Standards systems in Scotland at national and local levels as they operate in the development of sites and individual properties.

1.21 Following this, an outline of the roles of Environmental Health Officers (EHO) and Contaminated Land Officers (CLO) are discussed. Environmental Health is used generically to be the discipline within which the EHO/ CLO (or similar role) is typically found. However, it is acknowledged that the role of the EHO/ CLO may sit within differing departments or sections depending on the LA. The officer title for this role may also vary. The term EHO/ CLO is used in relation to any officer that performs a technical role in relation to review and assessment of information relating to land contamination issues, including mine gas.

1.22 The key elements presented are specific to the current research project.

Planning regime

1.23 The planning system in Scotland is overseen by the SG who is responsible for the development of legislation and national planning policy (SG, 2019b).

1.24 The primary responsibility for the delivery of planning services in Scotland lies with the 32 local planning authorities (PAs) and the two national park authorities: the Cairngorms and Loch Lomond and the Trossachs.

1.25 Planning permission primarily relates to the siting, appearance and use of the proposed building or other development. This includes considering the effect the proposed development may have on neighbouring properties and the surrounding environment.

1.26 The main primary legislation setting the structure of the planning system is the Town and Country Planning (Scotland) Act 1997. The 1997 Act has been amended by the Planning (Scotland) Act 2019, introducing a broad range of changes to the Scottish planning system.

1.27 Scotland's fourth National Planning Framework (NPF4) was adopted and published on 13 February 2023. NPF4 replaces NPF3, it includes national planning policy and also replaces Scottish Planning Policy (SPP). Together the national planning framework and local development plans (prepared by planning authorities) now form the statutory development plan. Section 25 of the Act sets out that decisions on planning applications are to be made in accordance with the development plan, unless there are material considerations that indicate otherwise.

1.28 Circulars, guidance and Planning Advice Notes (PANs) provide advice on planning matters.

1.29 The authors note that PAN 33, Development of contaminated land, was prepared in 2000 and re-published by the Scottish Government in 2017 (SG, 2017). PAN 33 (SG, 2017) is particularly relevant as it covers land contamination and related issues including 'flammable and toxic gases'. PAN 33 is therefore directly relevant to the regulation of mine gas risks associated with development.

1.30 PAN 33 also states that one of the key principles adopted by SG is the 'suitable for use' approach and identifies land contamination as a material planning consideration. The "suitable for use" approach consists of three elements:

1. ensuring that land is suitable for its current use -identifying land where contamination is causing unacceptable risks to human health and the environment

2. ensuring that land is made suitable for any new use, as planning permission is given for that new use

3. limiting requirements for remediation to the work necessary to prevent unacceptable risks to human health or the environment in relation to the current use or future use of the land for which planning permission is being sought

PAN 33 says that risks need to be assessed on a site by site basis. It is the responsibility of the developer to undertake an adequate risk assessment of a site, and to propose measures to ensure that these risks are appropriately addressed. PAN 33 also includes extracts from Model Planning Conditions, the addendum to circular 4/1998, The Use of Conditions in Planning Permissions.

1.31 A number of PAs have published their own supplementary planning guidance on land contamination issues (to accompany PAN 33). Environmental Protection Scotland (EPS) also published updated guidance 'Land contamination and development: Guidance for assessing and addressing land contamination issues to meet the requirements of Contaminated Land regulators in Scotland' in August 2019 (EPS, 2019).

1.32 Both the local planning authority and Building Standards have the role of ensuring that developments are 'suitable for use', taking into account specialist advice if necessary. In terms of land contamination, to ensure that land is made suitable for the proposed new use, planning authorities should require that applications include suitable provision for site assessment and where applicable, remediation measures.

1.33 When considering a planning application, a planning officer will need to consider, with specialist advice (from within the authority or externally), whether or not the developer has adequately identified and assessed the sources of contamination and put forward a suitable remediation scheme for the proposed use. SEPA has a role as a statutory consultee in the planning process for elements such as contamination risks to the water environment and flooding but does not have a role in the regulation of mine gas risks. Planning permission may be granted on the condition that development will not be permitted to start until a site investigation (SI) and assessment has been carried out and that the development itself will incorporate measures shown in the assessment to be necessary (mitigation or remediation). Pre-commencement planning conditions are normally included to this effect; some LAs require submission of a desk study and SI interpretive report in advance of granting planning permission.

1.34 Where applicable, a remediation strategy (RS) / remediation method statement (RMS) is commonly required under a planning condition. In the context of CO2 mine gas, where mitigation or remediation is required, this typically involves the installation and verification of gas protection measures to buildings.

1.35 The Coal Authority (CA) is a statutory consultee on planning applications for development within an area of coal working or former or proposed coal working notified by the CA to the planning authority^[2]. The CA is not a consultee for Building Warrant applications.

1.36 Mine stabilisation works, i.e. grouting of former workings, may also be required to mitigate geotechnical risks, e.g. settlement or subsidence, and this has the potential to affect mine gas risks. Drilling into workings and mine grouting as permitted activities regulated by the CA.

Building Standards

1.37 Building Standards relates to the design and construction of the proposed development, with the Building Regulations requiring minimum standards to be met. This includes ensuring buildings are safe, efficient, and sustainable.

1.38 Responsibility for the Building Standards system in Scotland sits with BSD under the Scottish Government's Directorate for Local Government and Communities.

1.39 Under The Building (Scotland) Act 2003, Scottish Ministers may make building regulations for purposes including "securing the health, safety, welfare and convenience of persons in or about buildings". These regulations were published as The Building (Scotland) Regulations 2004 (as amended).

1.40 The Scottish Government publishes several documents covering procedural and technical guidance which are reviewed on a regular basis. They also conduct any necessary research and consult on changes to the building regulations and associated Technical Handbook guidance on behalf of the Scottish Ministers.

1.41 Information on the Building Standards system is available via the Building Standards website. The latest versions, the 'Technical Handbook 2023: Domestic' and 'Technical Handbook 2023: Non-domestic' (SG, 2023) were updated in 2023, for use from 5 June 2023. These documents do not provide any information on ground gases, including mine gas, although radon is covered specifically. The equivalent document in England titled 'Approved Document C – Site preparation and resistance to contaminants and moisture' was reviewed and updated in 2013. This includes references to ground gas risk throughout the document with a small section covering methane and other ground gases.

1.42 Although the Building Standards system is overseen by BSD, the regulations are enforced at a local authority level. Local authorities are also appointed as building standards verifiers tasked with granting building warrants when they are satisfied proposed work meets building regulations and accepting completion certificates where completed works also comply. The Building (Scotland) Regulations 2004 implement building standards that are required to be met in the completed building so that there will be no threat to the building or the health of the people in and around it due to the presence of harmful or dangerous substances (mandatory standard 3.1). This is the standard which would apply to ground gas/ mine gas. Mandatory standard 3.2 relates to the emission and containment of radon gas.

1.43 When applying for a building warrant, design details are required to be submitted. In the context of the current research project these relate to site investigation reports (relating to land contamination and including mine gas where relevant), foundation design and gas protection measures, where applicable. These submissions are assessed by, or via, the Building Standards department to check the proposed work complies with the Building Regulations before issue of the building warrant.

1.44 Any changes to the design covered by the building warrant require the applicant to apply for an amendment to the building warrant. In the context of the current research project these amendments relate to changes in foundation design that may alter the previously submitted mine gas risk assessment. In turn, changes to the risk assessment may have implications for the design of gas protection measures.

Environmental Health/ Public Protection

1.45 Within this report the term 'Environmental Health' is used in the broadest sense of the term for the discipline that has the technical expertise in land contamination assessments, including ground gas. This may include Environmental Health Officers (EHO), Contaminated Land Officers (CLO), 'Geotechnical' staff, Public Protection staff or similar. Some LAs, particularly the larger ones, have a number of EHO/ CLOs that specialise in land contamination issues; whereas in other cases an EHO will have a wider role covering issues such as air quality, noise and nuisance, permitting etc. as well as land contamination issues.

1.46 In some LAs this role is based in the Planning Department or in some cases in development and regeneration departments. More commonly, the role(s) may sit within a wider Environmental Health/ Services or Public Protection Department. We are not aware of any instances where the Environmental Health discipline is based in the Building Standards department (except where this department is combined with planning).

1.47 The Environmental Health discipline typically provides scientific and technical support to Planning and/ or Building Standards with regards to land contamination, including mine gas risk assessment. Environmental Health is not responsible for enforcing any element of the development control process. Some departments engage external peer review support for one or more type of report submitted through the development control process.

Relevant technical standards and guidance

1.48 The 2019 research report (Section 6; SG, 2019a) provided a detailed appraisal of existing technical standards relating to ground gas assessment and mitigation, which remains current. Key references referred to in the 2019 report include:

• British Standard (BSI, 2019), BS 8485:2015+A1:2019 Code of practice for the design of protective measures for methane and carbon dioxide ground gases for new buildings
• British Standard (BSI, 2013), BS 8576:2013 Guidance on investigations of ground gas
• CIRIA (2014), C735, Good practice on the testing and verification of protection systems for buildings against hazardous ground gases.
• CIRIA, (2007), C665, Assessing risks posed by hazardous ground gases to buildings
• Chartered Institute of Environmental Health, (CIEH, 2008), The Local Authority Guide to Ground Gas (currently out of print).

1.49 Subsequent to the production of the 2019 research report and the initial data gathering and consultation phase of this research project, key technical guidance documents relating to mine gas risk assessment have been published. These fill some of the previously identified gaps in available data and guidance with regards to mine gas risk assessment and the review of submitted reports. While the assessment of the research project's consultations has been undertaken on the basis of information available at the time (December 2020-January 2021), comment is given where the more recent guidance may have a direct impact on the consultant responses and subsequent recommendations on good practice within local authorities.

1.50 Key documents published since this report was originally drafted in 2021 comprise:

• Land Contamination Risk Management, LCRM, originally published in October 2020 by the Environment Agency in October 2020 and last updated in July 2023 (EA, 2023).
• CL:AIRE (2021) Good practice for risk assessment for coal mine gas emissions, published in October 2021, and
• NHBC (2023) NF94 Hazardous ground gas, an essential guide for housebuilders, published in May 2023.

1.51 LCRM provides overarching guidance for the assessment and management of land contamination. Although developed for England and Wales and not currently formally adopted for use within Scotland due to an ongoing review of certain divergences in regulatory policy and terminology, SEPA has stated that they consider it to present good practice guidance on the approach to the assessment of potential land contamination constraints. This guidance can be used where it is demonstrated to be appropriate for site specifics and relevant regulatory regimes, such as planning and building control.

1.52 The CL:AIRE (2021) Good practice for risk assessment for coal mine gas emissions is the most pertinent guidance document to have been produced . The document is intended to 'be regarded as essential reading towards understanding coal mine gas risk assessment' and is intended to supplement BS8485:2015+ A1:2019 (BSi, 2019). It highlights the Gorebridge incident as a contributing factor to the need for additional guidance on mine gas assessment, as well as the recommendations of the 2019 Scottish Government research project on mine gas risk. The intended audience is those involved in commissioning and undertaking coal mine gas risk assessments to support proposed development, and local authority officers involved in regulating development management through the planning or building control regimes. It is therefore directly relevant to the regulation of mine gas risk for development in Scotland.

1.53 CL:AIRE (2021) considers a number of factors relevant specifically to coal mine gas risk assessment, including those related to the history and methods of mining; sources of mine gas, migration pathways and barriers; and effects of changing groundwater levels. It highlights that research into previous incidents involving mine gas show that uncontrolled mine gas emissions that pose a significant risk to development are generally associated with one of the following scenarios:

• A point source emission from a specific abandoned mine entry affecting a few square metres of ground (mainly bulk advection).
• A localised emission where gas has escaped from a specific mine entry and migrated along shallow, permeable migration pathways affecting a few tens of square metres of ground, or
• An extended area emission where gas is migrating to the surface through the permeable ground overlying an extensive area of shallow, gassy mine workings directly beneath the permeable strata (or via fault zone from deeper strata).

1.54 The guidance states that deep workings do not generally pose a significant risk of gas emissions through the overlying strata unless they are connected to the surface by shafts, boreholes, etc. The risk of mine gas emissions from permanently flooded workings is significantly reduced. Based on this, the guidance presents an overall mine gas risk assessment process, including data requirements relevant to each assessment stage and a risk zoning approach. It also includes advice on the detailed assessment of gas monitoring data and other suitable lines of evidence.

1.55 Other aspects of the guidance are as follows:

• Mine gas risk assessments and mitigation design should be carried out by 'competent persons' based on qualifications and experience/ proven track record. Relevant qualifications include chartership with an appropriate organisation and additional accreditation such as SoBRA, SQP, SiLC or RoGEP. A proven track record means a regulator or consultant who regularly deals with the technical aspects of mine gas. For example, someone with knowledge and experience of the development planning regime or someone who regularly deals with the technical aspects of land contamination.
• That it is essential to understand the different methods of working coal and the effect this has on the likely presence of a mine gas hazard being present below a site and the risk of emissions into buildings.
• Development of a robust and visual mine gas-specific conceptual site model (CSM) is a vital part of mine gas risk assessment. To aid this, the guidance includes detailed discussion on mine gas sources, migration pathways and barriers, as well as the effect of changing groundwater levels on gas risks. This should be refined continually through the assessment process.
• To aid risk assessment, a decision support tool is provided, which utilises data available from the Coal Authority and site-specific geological and hydrogeological data to categorise sites from 'no mine gas risk' through to 'high risk' zones. Moderate and high risk zone sites require detailed mine gas risk assessment, including suitable site investigation and use of a multiple lines of evidence approach to risk assessment. The report highlights that coal mine gas risk assessment using the gas screening values and 'points system' as presented in BS8485:2015+A1:2019 (BSi, 2019) on their own is unlikely to be appropriate where there is a risk of mine gas emissions and should be used with extreme caution.
• The guidance highlights how to identify and manage current and future uncertainties in the assessment, including climate change and other reasonably foreseeable events. These are noted to be a requirement of LCRM (EA, 2023) as well as the National Quality Mark Scheme for land contamination (NQMS).
• The effects of foundations and other below ground infrastructure on migration pathways and the integrity of low permeability 'barrier' layers should be considered within the mine gas risk assessment, and if amended subsequently in the design process, the gas risk assessment should be reviewed and updated.
• It is highlighted that it is vital that site investigation boreholes should be decommissioned and sealed in a manner that prevents them acting as pathways for mine gas into buildings.
• Case studies are included to illustrate key issues under discussion.

1.56 The NHBC published guidance document NF94 (2023) Hazardous ground gas, and essential guide for housebuilders in May 2023. The document, aimed at residential housing developers, supersedes previous NHBC guidance released in 2007, and contains a concise yet detailed account of the NHBC's expectations with regards to ground gas risk assessment, including mine gas. NF94 presents the whole process of ground gas risk assessment (including mine gas), and gas mitigation design and verification. It should be noted that NF94 is a research and advisory publication and not a prescriptive standard.

1.57 The report highlights the following key elements:

• Competent professionals must be employed to advise on ground gas. This includes professional membership and accreditations such as chartered status, SiLC, and SoBRA accreditation.
• Ground investigation and gas monitoring should be targeted to specific development hazards as outlined in a robust CSM. Investigation methods should inform a 'lines of evidence' approach to assessing ground gas risk. Gas monitoring should be reliable, incorporate potential 'worst case' conditions, and support further quantitative risk assessment methods.
• Risk assessments should be robust and repeatable. A range of tools and approaches are available the assessment of sites affected by low, moderate and high gas hazards. The installation of ground gas membranes is not a suitable replacement for poor investigation and assessment practice.
• Gas protection design is not just about adding up points in BS8485:2015+ A1:2019 (BSi, 2019). Design reports should provide the rationale and justification for the full scope of gas protection measures. The specification of materials within gas protection design should be undertaken by the designer and include consideration of the material suitability in construction and context of the wider development design.
• Installation of gas protection should be undertaken by competent professionals in accordance with the design. Measures should be verified to prove their effectiveness and reported. Following installation, gas protection measures must be protected from damage.

1.58 With respect to mine gas specifically, this is considered within NF94 Section 1.4.6 'Identification of high-risk scenarios' and links back to the relevant guidance provided in CL:AIRE (2021).

Mine gas related reports supporting development applications

1.59 There are up to six types of reports relating to mine gas assessment and mitigation that may be submitted to support a planning or building warrant application, which are briefly explained below. Report terminology varies between guidance documents and consultants, and reports combining one or more elements may be prepared.

Desk study/ preliminary investigation

1.60 The objective is to provide information on past and current uses of the site and surrounding area, along with the nature of any hazards and physical constraints. An initial conceptual model is developed, and a preliminary qualitative risk assessment completed to identify and assess potential pollutant linkages. A pollutant linkage comprises a source (a contaminant or pollutant in or under the land that has the potential to cause harm or pollution) and a receptor, linked by means of a pathway. The pathway is a route by which a receptor is or could be affected by a contaminant or pollutant. The pollutant linkages inform the design of the intrusive investigation. In the context of this report, the source is mine gas. The receptors are residents/ other site occupiers and building structures, and pathways are the means by which gas can migrate from depth to near surface and ingress into buildings. All three elements need to be in place for the pollutant linkage to be complete and a potential risk to be realised.

Site investigation

1.61 The objective is to obtain data on the nature and extent of contamination, the geology, geochemistry, soil, hydrogeology, and hydrology of a site. The intrusive works provide data to review the initial conceptual model and to update the risk assessment based on those findings. The investigations provide data for the selection and design of remedial works, if required.

Detailed ground gas risk assessment

1.62 The objective is to further assess risks presented by either ground gas/ mine gas to a proposed development through the additional assessment of ground conditions, soil permeability, the nature of ground gas sources and their generation potential and interpretation of ground gas data undertaking further interpretation of multiple lines of evidence in order to present a detailed assessment of gas risk at a development site. The need for a detailed ground gas risk assessment is dependent on the overall risk level and site complexity. For example, the 2021 CL:AIRE guidance states that a detailed ground gas risk assessment must be undertaken for sites classified as 'high' or 'moderate' risk zones in relation to mine gas. Use of the empirical approach in BS 8485 comprising simple derivation of a site Characteristic Situation is not appropriate when mine gas risk is present at a site.

Remediation strategy or remediation method statement

1.63 The objective is to identify remediation options, complete an evaluation of options if required and select the final remediation option in relation to each pollutant linkage identified as being complete following the intrusive site investigation. The remediation strategy should include a verification plan, setting out details of how data will be collected and assessed to demonstrate remediation objectives have been met. In relation to gas protection measures the information required relates to the building type and gas protection score (points), setting out how this will be achieved.

Design report for gas protection measures

1.64 A design report should present the detailed design and specification of the gas protection measures as detailed in BS8485:2015 + A1:2019 (BSI, 2019). This is normally required in relation to the building warrant application as it relates to the design and construction phase of the development. A design report may not necessarily be required in relation to any planning condition, due to the detailed technical nature of the report. However, design reports may be submitted in relation to an application to discharge planning conditions relating to remediation.

1.65 Table 8 of BS8485 (BSI, 2019) sets out the information to be included in the design, installation and verification reports relating to ground gas protection measures. A verification plan for the installation of the membrane should be part of the detailed design. This report may replace the need for a detailed remediation strategy if gas protection measures are the only remediation (mitigation) measure required at a development.

1.66 The design report, where gas protection measures are required, should form part of the approved plans that accompany the building warrant issued.

Verification report

1.67 The report should present evidence to show that remediation has been successful. In relation to mine gas this will be directly related to presenting an accurate description of the measures actually applied and present the evidence gathered to confirm that installed measures are suitable for purpose.