Publication - Research and analysis

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

Published: 9 February 2024
Directorate: Local Government and Housing Directorate
Topic: Building, planning and design
ISBN: 9781835216491

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.

Supporting documents

Annex D Template for peer review of mine gas related reports

Table 1a: Report and site details
Report 1
Review reference:
Site name:		Planning ref:	Building standards ref:
Site area (ha.):		Grid reference:	Site address:
Date of review:		Reviewed by:	Approved by:
Summary of development:
Review/ check requested:	Planning ☐ Building Standards ☐ Has planning permission been granted? Yes ☐ No ☐
Report title:			Report date:
Report type:	Desk study/ PRA ☐ SI report ☐ Remedial strategy ☐ Design report ☐ Verification report ☐ Other ☐		Report author:
Report 2
Report title:			Report date:
Report type:	Desk study/ PRA ☐ SI report ☐ Remedial strategy ☐ Design report ☐ Verification report ☐ Other ☐		Report author:

Table 2a: Detailed peer review findings – Desk study (mine gas)
Report author, title, reference and date:
Aspect	Information in report	Review comments
Does the report cover the whole site?^[3]	Yes ☐ No ☐
Scope of works completed:	Review of site history ☐ Review of environmental setting ☐ LA/SEPA consultation? ☐ Site reconnaissance ☐ Initial conceptual site model (CSM) development ☐ Preliminary Risk Assessment (PRA) ☐
Current use:
Summary of historical map review On-site:
Adjacent land:
Are there any previous investigations that have been reviewed?	Yes ☐ No ☐ If Yes:
Geology and hydrogeology
Superficial deposits (including details of permeability):
Bedrock (including fractures):
Groundwater (and depths):
Is the site in a Coal Authority (CA) coal mining reporting area?	Yes ☐ No ☐ N/A ☐
Is the site in a CA development high risk area (DHRA)?	Yes ☐ No ☐ N/A ☐
Has the CA responded as a statutory consultee for a DHRA?	Yes ☐ No ☐ N/A ☐
Is a CA Consultants Coal Mining Report (or similar) included and the findings discussed? (note that a Consultants Report provides greater detail than a CON29M report)	Yes ☐ No ☐ N/A ☐
Are there mine shafts/ entries on site or within 50m of the site boundary?	Yes ☐ No ☐ N/A ☐
Are there shallow workings on site or within 50m of the site boundary?	Yes ☐ No ☐ N/A ☐
Depth to coal seams and workings known?	Yes ☐ No ☐ N/A ☐
Are workings flooded or likely to be flooded?	Yes ☐ No ☐ N/A ☐
Faults or other potential pathways connecting surface to deeper unflooded workings?	Yes ☐ No ☐ Unknown ☐
For sites in former coal mining areas, has a Coal Authority report been ordered and has the CL:AIRE Good Practice for Risk Assessment for Coal Mine Gas Emissions decision tool been applied?	Yes ☐ No ☐ N/A ☐
Has a Coal Mining Risk Assessment (CMRA) been submitted (and reviewed as part of the desk study)?	Submitted: Yes ☐ No ☐ N/A ☐ Reviewed and discussed: Yes ☐ No ☐ N/A ☐
Any proposed (or likely) credible future changes that could impact on mine gas risk (e.g. water levels, grouting etc.)?	Yes ☐ No ☐ Unknown ☐
Is the site in an area of non-coal mining or quarrying?	Yes ☐ No ☐ Unknown ☐
Site reconnaissance observations (evidence of past coal mining identified)?	Yes ☐ No ☐ Unknown ☐
Any additional relevant information reviewed or commented on in Desk Study review relating to mine gas?	Yes ☐ No ☐
Has a preliminary CSM been included and has mine gas been specifically included in it?	Yes ☐ No ☐ Schematic CSM provided? Yes ☐ No ☐
Does the preliminary CSM include any design/ construction aspects that could influence mine gas risk e.g. foundations, drainage, grouting ?	Yes ☐ No ☐
Are the receptors identified appropriate (e.g. buildings and persons using the buildings, including off-site)?
Summary of report conclusions for mine gas:
Is further data collection e.g. SI recommended in the report?	Yes ☐ No ☐
Review summary:
Is the desk study of sufficient extent and scope with respect to considering ground conditions and mine gas?		Yes ☐ No ☐
Summary of review points requiring further consideration:	1. 2.

Table 2b: Detailed peer review findings – Site investigations (mine gas)
Report author, title, reference and date:
Aspect	Information in report	Review comments
Does the report cover the whole site?^[4]	Yes ☐ No ☐
Scope of works completed:	Objectives ☐ Initial CSM ☐ Scope of works/ methodology ☐ Factual data ☐ Mine gas GQRA ☐ Refined CSM ☐ DQRA ☐
Site investigation review
Summary of SI scope:
Sufficient number of boreholes to determine if workings present at shallow depth <30m? (note probable unrecorded workings <30m deep is presented in a CA Consultants Report)	Yes ☐ No ☐
Summary of mine gas monitoring scope (proposed and actual):
Ground conditions encountered (including workings):
Gas monitoring well design:
Strata monitoring wells response zone installed in:
Do response zones span multiple strata or worked seams and surrounding strata?	Yes ☐ No ☐
Groundwater monitoring undertaken (details and depths):
Gas monitoring (scope and dates): Have all proposed monitoring rounds been completed? Continuous or spot monitoring (or both)	Yes ☐ No ☐ Continuous ☐ Spot ☐ Both ☐
Are any response zones flooded or partial flooded at the time of monitoring (details of which/when):	Fully Yes ☐ No ☐ Partially Yes ☐ No ☐
Is all mine gas related factual data presented in appendices?	SI logs ☐ Monitoring data ☐ Reports or other outputs ☐
Has gas sampling/ monitoring equipment has been calibrated appropriately?	Yes ☐ No ☐ Unknown ☐
Has an appropriate level of investigation been undertaken in relation to mine gas, as identified within the desk study?	Yes ☐ No ☐
Have appropriate figures been presented e.g. geological cross section/ ground model?	Yes ☐ No ☐
Risk assessment review
Is the mine gas / ground gas assessment consistent with BS8485:2015+A1:2019 and the CSM?^[5]	Yes ☐ No ☐
Has the CL:AIRE Good Practice for Risk Assessment for Coal Mine Gas Emissions decision tool been applied risk?	Yes ☐ No ☐
Has depleted oxygen been discussed?	Yes ☐ No ☐ N/A ☐
Are the recorded gas concentrations concluded to be due to mine gas (or other ground gas sources)?	Yes ☐ No ☐
For a mine gas detailed quantitative risk assessment (DQRA) have appropriate input parameters been selected and referenced and their use fully justified?	Yes ☐ No ☐ N/A ☐
Are there any data gaps, uncertainties or issues which are stated to require clarification?	Yes ☐ No ☐
Report conclusions
Are the revisions to the CSM appropriate to the outcomes of the mine gas risk assessment and the development proposals? Has an updated/refined schematic CSM been presented?	Yes ☐ No ☐ Yes ☐ No ☐
Are gas protection measures proposed?	Yes ☐ No ☐ N/A ☐
Does the CSM sufficiently consider any proposed ground stabilisation/ grouting works and their implications?	Yes ☐ No ☐ N/A ☐
Does the CSM consider off-site receptors (e.g. if enabling works alter ground conditions/ migration pathways)?	Yes ☐ No ☐ N/A ☐
Have data gaps/ uncertainties been considered appropriately (e.g. credible future changes)?	Yes ☐ No ☐
Are there any other issues relevant to the mine gas risk assessment such that additional clarification is required?	Yes ☐ No ☐
Summary of report conclusions for mine gas:
Is further data collection e.g. supplementary SI or gas monitoring recommended in the report?	Yes ☐ No ☐
Review summary:
Is the SI and risk assessment of sufficient extent and scope with respect to considering ground conditions and mine gas?		Yes ☐ No ☐
Summary of review points requiring further consideration:	1. 2.

Table 2c: Detailed peer review findings – Remediation strategy (mine gas)
Report author, title, reference and date:
Aspect	Information in report	Review comments
Does the report cover the whole site?^[6]	Yes ☐ No ☐
Have there been any design changes to the development (e.g. foundations) since the desk study/ SI reports?	Yes ☐ No ☐
Have all mine gas linkages requiring remediation/ mitigation been identified?	Yes ☐ No ☐
Have gas protection measures been designed in accordance with BS8485 (noting correct building type and gas protection score)?	Yes ☐ No ☐
Has appropriate verification and validation testing of gas protection measures been recommended^[7]?	Yes ☐ No ☐
Have the impacts to off-site receptors been considered during remedial actions for mine gas, and are controls required?	Yes ☐ No ☐ N/A ☐
Are there other issues which are stated to needed to be considered in relation to mine gas?	Yes ☐ No ☐ N/A ☐
Where there are existing monitoring wells that could represent gas migration pathways, does the report discuss decommissioning of monitoring wells to seal gas migration pathways? Is the proposed decommissioning (and verification) of monitoring wells appropriate?	Yes ☐ No ☐ Yes ☐ No ☐ N/A ☐
Is a foundation works risk assessment required to avoid the creation of preferential pathways for gas migration during development?	Yes ☐ No ☐
Where this report includes detailed design of gas protection measures (i.e. that required in BS8485) are the detailed drawings and appropriate to the CS?	Yes ☐ No ☐
Does the report state that a stand alone design report (and associated drawings) in accordance with BS8485 will be prepared?	Yes ☐ No ☐
Summary of report conclusions for mine gas:
Review summary:
Is the report sufficient to demonstrate that all identified mine gas pollutant linkages will be mitigated to ensure the site is suitable for its proposed end use and addresses mandatory standard 3.1?		Yes ☐ No ☐
Summary of review points requiring further consideration:	1. 2.

Table 2d: Detailed peer review findings – Verification report (mine gas)
Report author, title, reference and date:
Aspect	Information in report		Review comments
Does the report cover the whole site?^[8]	Yes ☐ No ☐
Has the verification report for the gas protection measures been prepared by a Specialist under the Gas Protection Verification Scheme (GPVS)?	Yes ☐ No ☐
Have there been any relevant design changes to the development (e.g. foundations) since the remediation strategy?	Yes ☐ No ☐ Unknown ☐
Have the ground gas protection measures been installed and verified in accordance with the Remediation Strategy and CIRIA C735?	Yes ☐ No ☐
Have any other relevant remediation activities been undertaken and verified in accordance with the Remediation Strategy?	Yes ☐ No ☐
Have any unexpected contamination/ made ground/ coal mining features been identified during earthworks and has this been dealt with appropriately?	Yes ☐ No ☐ Unknown ☐
Has appropriate evidence been presented for decommissioning of monitoring wells?	Yes ☐ No ☐ N/A ☐
Is there a requirement for long-term monitoring and/ or future verification work?	Yes ☐ No ☐ N/A ☐
Are there other issues which need to be considered in relation to mine gas?	Yes ☐ No ☐ N/A ☐
Is there a revised / updated CSM confirming that all identified mine gas pollutant linkages have been addressed, that the site is suitable for use?	Yes ☐ No ☐
Summary of report conclusions for mine gas:
Review summary:
Is the report sufficient to demonstrate that all identified mine gas pollutant linkages have been mitigated to ensure the site is suitable for its proposed end use and addresses mandatory standard 3.1?			Yes ☐ No ☐
Summary of review points requiring further consideration:		1. 2.

Table 3: Summary peer review findings
Following the review, it is considered the following to apply: -
Summary	Applicable
Planning regime
The investigations, assessments and/or remedial strategy presented are considered sufficient to support that no mitigation measures for mine gas are needed.	√ or n/a*
The investigations, assessments and/or remedial strategy are considered sufficient to progress development; post-works verification reporting should be provided once works are complete.	√ or n/a*
Further information/ submissions are required.	√ or n/a*
Can the further assessment or remediation required be conditioned?	√ or n/a*
Can the following relevant planning conditions be discharged?	√ or n/a*
Quote condition No. and full detail here	√ or n/a*
Quote condition No. and full detail here	√ or n/a*
Building standards (see notes below)
Confirmation the proposals show compliance with mandatory standards 3.1 and 3.2^	√ or n/a*
More information is required to demonstrate compliance with mandatory standards 3.1 and 3.2^ – please refer to summary of review points requiring further consideration in detailed peer review table above	√ or n/a*

* delete as applicable; ^ review relates to design phase only; construction and verification are dealt with through completion certificate(s)

Notes for Building standards:

'Standard 3.1: Every building 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.'

'Standard 3.2: Every building must be designed and constructed in such a way that there will not be a threat to the health of people in or around the building due to the emission and containment of radon gas.'

Contact

Email: buildingstandards@gov.scot

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Information

Annex D Template for peer review of mine gas related reports

Contact

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