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

Annex E LA Consultation on interim report

Name:

Local Authority:

Job Title:

Department or discipline (e.g. Env Health or similar, Building Standards, Planning):

Comments in relation to Section 5 and Annex C:

Note: If any part of Section 5 is not relevant to your discipline, please state N/A

Section 5 (5.10 onwards) discusses each of the key stages in Annex C in detail. Annex C presents a flow chart setting out the proposed process for good practice in the regulation of mine gas risk to development under planning and building standards. The process described does not specifically cover consultation with the Coal Authority, which is likely to be occurring in parallel as they are a statutory consultee for all developments in areas of former or proposed coal workings.

Post consultation notes – Not every respondent commented on every question and only comments directly relevant to the questions are presented.

Affirmative comments (e.g. agree) are not presented.

Comments were broadly supportive of the proposed good practice approach and peer review template.

Receipt of planning applications – screening of sites (5.10 to 5.14, including Table 5-1)

Respondent 1: Please provide clarification that the terms 'Reporting Area' and 'Development Low Risk Area' are used interchangeably, for the avoidance of doubt (as the planners like to say).

We don't have Coal Authority Mine entries, Past or probable or Previous incident layers in our GIS, except zoomed out beyond 1:25,000 scale which makes it difficult to interpret accurately.

Respondent 3: Agree, it would be expected that planners would undertake the bulk of screening by reviewing Coal Authority GIS layers and also internal GIS layers where applicable.

Respondent 4: Initial screening of all planning applications should be carried out by Planning and not Environmental Health as they receive and log all applications.

I think it important that other mine-related risks are addressed as part of this screening process to limit duplication of work at a later date, to ensure developers are made aware of all mining risks to be dealt with as part of the development and to prevent perhaps more significant mining risks being overlooked at this stage in favour of mine gas.

Respondent 5: Consider that the Coal Authority should provide more details of records of mine gas or potential risk of mine gas as part of their standard CON29M reports as it would highlight the need for applicants/developers to consider mine gas risks at an early stage of development as standard practice in areas of historical mining.

Respondent 7: All applications are screened for coal mining issues using CA information. Contamination assessments are required for all applications for a new building.

5.22 Agree. But in reality we often get RS submitted after site works have commenced on site…..

Respondent 1: Please provide clarification that the terms 'Reporting Area' and 'Development Low Risk Area' are used interchangeably, for the avoidance of doubt (as the planners like to say).

We don't have Coal Authority Mine entries, Past or probable or Previous incident layers in our GIS, except zoomed out beyond 1:25,000 scale which makes it difficult to interpret accurately.

Respondent 3: Agree, it would be expected that planners would undertake the bulk of screening by reviewing Coal Authority GIS layers and also internal GIS layers where applicable.

Respondent 4: Initial screening of all planning applications should be carried out by Planning and not Environmental Health as they receive and log all applications.

I think it important that other mine-related risks are addressed as part of this screening process to limit duplication of work at a later date, to ensure developers are made aware of all mining risks to be dealt with as part of the development and to prevent perhaps more significant mining risks being overlooked at this stage in favour of mine gas.

Respondent 5: Consider that the Coal Authority should provide more details of records of mine gas or potential risk of mine gas as part of their standard CON29M reports as it would highlight the need for applicants/developers to consider mine gas risks at an early stage of development as standard practice in areas of historical mining.

Respondent 7: All applications are screened for coal mining issues using CA information. Contamination assessments are required for all applications for a new building.

5.22 Agree. But in reality we often get RS submitted after site works have commenced on site…..

Submission and review of desk study and site investigation report (5.15 to 5.22)

Respondent 1: Although a desk study/SI/geotechnical report may be submitted for planning applications and maybe available on a shared document management system, Building Standards would not usually review these reports part of an initial planning application. The is no requirement to do so and quite separate processes. The Annex C flowchart appears to indicate a "linked application check" at the "Planning application submitted" stage. Appreciated this may be referring to when a BW application is submitted and at this point Building Standard may check back to see if a previous planning application.

Respondent 2: (Might I suggest 'SI' is written 'site investigation' or in fact I prefer 'ground investigation'.). Typo at 5.19: it should read 'discharge of the relevant planning condition' (not application).

I agree with all of 5.23. (I would like to think that 'model' conditions cover all eventualities with advice being offered on how to achieve discharge of conditions; agreeing model wording took a long time first time around! However, I appreciate this is best practice, so 5.24 is fine as well.)

Respondent 4: Advice should be provided on how to approach extensions on existing sites (which may or may not have mine gas protection measures installed).

Submission of a desk study prior to a planning permission decision will cause delays in determination and have implications for Planning Performance Indicators.

IT systems required to ensure linking of reports to address gazetteers, document sharing systems etc may take some time and budget to provide at LAs who do not currently have such systems available.

In general, specific training and guidance for officers peer reviewing mine-related risks reports is considered necessary to ensure risks are appropriately identified and dealt with as part of the site development.

It would be useful for uniformity of approach, if standard conditions could be drafted for LAs in conjunction with the CA rather than individual LAs coming up with their own conditions. The CA have previously suggested the standard contaminated land planning conditions are not appropriate for dealing with mining issues.

Respondent 5: 5.21 As part of the peer review process the CL Team would consider a development site for both aspects of Planning & BS considerations at the same time and issue our review response to both allocated Planning Officer & Building Standards Surveyor (when known).

Respondent 7: In general the procedures adopted in [our LA] follow those suggested in the document with the exception of requiring a desk study prior to approval. Normally information on contamination, if not submitted with the application, is required using conditions unless there is a very strong reason (known mine gas issues/ landfill site/ gas works) to require this prior to granting permission.

Planning decision and setting conditions (5.23 to 5.25)

Respondent 2: I agree with all of 5.23. (I would like to think that 'model' conditions cover all eventualities with advice being offered on how to achieve discharge of conditions; agreeing model wording took a long time first time around! However, I appreciate this is best practice, so 5.24 is fine as well.)

Respondent 5: 5.24 Currently not a specific CL planning condition for gas remedial measures – any mine gas risk assessments or remedial measures and validation would be dealt with under the above conditions.

5.25/5.26 Agree – but we very rarely get Phase 1/2/3/4 reports submitted before a planning application is granted (usually granted with conditions attached) so identification of a Characteristic Situation CS4 is unlikely to be identified at an earlier stage of the planning process.

Respondent 7: Standard contaminated conditions are applied to every application for a new building. These conditions are worded in a very general way and the detailed/ specific issues are addressed through the peer review process. Conditions are not discharged until all issues have been adequately addressed.

Submission and review of remediation strategy (5.26 to 5.29)

Respondent 5: 5.26 – as per comments in 5.25

5.27 Agree – But this information is not something we regularly get submitted as part of submitted remedial strategies.

5.28 CL Team peer review procedures as per our comments in 5.19 & 5.20

5.29 The CL Team complete general peer reviews of submitted Phase 1/2/3 & 4 reports not detailed technical reviews. As CLOs we are not expert technical reviewers. The responsibility for accurate and appropriate detailed risk assessments and remedial designs for any contamination risks (including mine gas) lies with the developer/representative consultants/architects/contractors.

Aspects specific to building warrant applications (5.30 to 5.34, including Table 5-2)

Respondent 1: Upon receipt of a BW application and commencement of assessment against the standards, regardless if there has been a linked Planning application with relevant SI's and Contaminated land Team input, we would ask for copies of SI's/reports to be provided as part of the BW submission. These would still form part of the BW application and provide audit trails etc.

Respondent 2: Table 5-2: should there be an additional line in the table covering any grouting of mine workings that has been carried out on site (including whether a pre-mixed cement grout was used or they just poured dry materials into the hole)?

Keeping a database of properties where gas protection measures have been installed is something we keep saying we should do but have not consistently managed to achieve.

Respondent 4: Screening of Building Warrant applications should be carried out by Building Standards rather than Environmental Health as they are dealing with all incoming warrant applications.

Respondent 5: As a matter of urgency, I strongly recommend that the BS Mandatory Technical Guidance should be revised to include all mine gas along with radon gas.

Table 5.2 – Should include a line/column regarding mine consolidation works and potential impact of mine gas migration.

Also consideration of mine shaft location accuracy – 20m distance potentially not conservative enough - confirmation if indicated mine shafts has been accurately located by ground investigation or if indicative position.

Respondent 7: Contamination assessments are required for all building warrant applications for new buildings, large extensions or on sites where previous remedial measures have been required (such as a conservatory on a site where gas protection measures were required).

Review of design report for gas protection measures (5.35 to 5.38)

Respondent 1: Regarding 5.38, Building Standard case officer may be able to review gas protection measures (if common typical proposals) without need to consult with Planning or Contaminated Land Team. This 5.38 clause states: "The findings of the review(s) are documented and retained on a shared document management system, and directly linked to a property gazetteer." Would suggest the clearing or approval of protection measures is not specifically highlighted to planning/contaminated land team. The approved details/drawings would form part of the approval package associated with the building Warrant.

Respondent 2: This is not really my area of expertise. Only this morning I had to query a verification report that stated 'passive ventilation layer' in the text but appeared to show no provision in the design drawings or photographs. We EHO/ CLO are not qualified to interpret foundation design drawings.

Respondent 6: It is acknowledged that this section of the document notes that a stand alone design report should be submitted for CS3 or above. I have no objection to this proposal. It is assumed that a key purpose of this distinction is to raise the importance of the design report to relevant parties, e.g. developers.

Respondent 4: Section 5.37 is ambiguous in terms of who is responsible for reviewing the report. I think the principle of the types and number of protection measures to be installed should be agreed with EH but anything more technical than that should be reviewed by BS due to their in depth buildings knowledge.

Respondent 5: Not the CLOs area of expertise. As CLOs we are not expert technical reviewers. The responsibility for accurate and appropriate detailed risk assessments and remedial designs for any contamination risks (including mine gas) lies with the developer/representative consultants/architects/contractors.

Building warrant approval (5.39 to 5.40)

Respondent 1: Agree…..consultation with Contaminated Land team unlikely if the amendment is only for change to detailing. Would likely only consult again if further risks or change in contamination to the land was identified. This is unlikely and usually the SI/reports for the initial BW application covers all identified risks on site.

Respondent 5: 5.40 Generally, the CL Team would not be informed of any amendments to BWA that might have impact on potential mine gas risks. If there has been a foundation design change that may impact proposed remedial measures then it would be the responsibility of the developer/applicant/representative consultant/architect to the review the design change, ensure there is no significant mine gas impact, amend remedial measures if required and inform Building Standards and CL Team of the change.

Installation and verification of gas protection measures (5.41 to 5.42)

Respondent 1: Protection measures likely to be/should be highlighted on the BW Construction Compliance Notification Plan (CCNP) so reasonable enquiry is required to confirm installation is as per approved BW details etc. Building Standards officer could maybe sample inspect first protection measures on site If not too specialised or (more commonly) agree with site management that suitable "sign-off" evidence/verification will be provided from specific installers or site engineer for each installation.

Review of verification report (5.43 to 5.47)

Respondent 1: Not aware of any Approved Certifiers of Constructions schemes available in Scotland for covering gas protection measures. Common certifiers of construction consist of Electricians (SELECT scheme) and plumbers and similar for drainage, heating and plumbing (SNIPEF scheme). Issuers of these certificates unlikely to need to view/be concerned with verification reports for gas protection measures.

On receipt of verification reports/evidence, Building Standards unlikely to refer to Contaminated Land Team/Planning. No requirement to do so within BS legislation/procedures. Therefore in this regard I am unsure how Planning/Contaminated Land team co-ordinate process to be passed verification report or ensure this has happened.

Respondent 2: Just to note that, in Scotland, verification rarely if ever meets the requirements of [CIRIA] C735. It would be difficult for the local authority to insist on full compliance, because that would result in no development work ever being completed.

Respondent 3: Agree. Borehole decommissioning could be included here.

Respondent 4: I think the majority of officers reviewing verification reports would require guidance and training to ensure they are able to carry out this task competently.

Respondent 5: Agree that reports should include measures to decommission boreholes. However in our experience, it would be very difficult for Falkirk Council to insist on full compliance to C735, without mandatory statutory guidance/regulations in relation to mine gas issues being enforceable.

Acceptance of building warrant completion certificate (5.48)

Respondent 1: As above….we have no process/procedure to pass verification reports to Contaminated Land. If Building Standards officer review of report/evidence appears acceptable and covers for the protection measures as approved and proposed, Completion Certificates can be accepted.

Comments in relation to Annex D – peer review template:

Note: We assume comments in relation to Annex D will primarily be made by an EHO/ CLO (or similar), or a Building Standards Officer if they technically review any of the submitted reports.

Please state the peer review question number in Annex D that relates to the table and detail your comment in relation to that question (or state if it is an additional peer review question you are suggesting).

Table 2a: Detailed peer review findings – Desk study (mine gas)

Respondent 2: Point 1: yes, spot on! (It's amazing how often the coal report is for an adjacent or nearby site.)

Point 24: also very important (see comments in relation to Table 5-2 above).

Respondent 4: I do not have comment on any of the templates specifically but would note that this creates a significant amount of extra work for the officers dealing with relevant applications. In addition, I think guidance for officers on what should be expected to satisfy each of the various sections of the tables would be essential (for example what constitutes 'adequate evidence', 'appropriate', 'sufficient' etc in each case).

Respondent 5: CL Team would rarely get Phase 1 report that would detail Points 8. to 18. Sometimes receive separate CMRA Report that covers some of the points but not detailed mine gas risk assessment.

Table 2b: Detailed peer review findings – Site investigations (mine gas)

Respondent 2: Point 4: where does definition of shallow workings as <30 m depth come from?

Point 7: ground gas should be measured in wells that are not intended for groundwater testing.

Point 9a: always check to see if the response zone was flooded.

Point 24: again very important (future grouting must not be dealt with in isolation).

Respondent 6: In regard of Q13. I often find the data is presented in pdf format. There may be scope to note in this section, if the data can be provided in a format to support its interrogation / analysis, e.g. excel. Highlighting this within Table 2b may play a small part in supporting the timeous review of submissions.

In regard of Q7. The sealing of the well can be of key importance. There may be some value in bringing this out in Q7 or another question within this table.

Respondent 5: Point 5. Very rarely get mine gas monitoring boreholes. Usually shallow boreholes within superficial soils are monitored for ground gas. Cost implications for monitoring both mine gas and ground gas in differing strata. Would need clear and precise regulatory guidance and BS Technical Handbook updated to enforce this requirement.

Perhaps monitoring for mine gas should be included as mandatory as part of any mine consolidation works and include pre- grouting, during grouting and post grouting monitoring to determine impact of any consolidation works on mine gas migration and appropriate gas remedial measures to be incorporated into proposed buildings. Appropriate decommissioning of boreholes could be linked to this too if relevant.

Table 2c: Detailed peer review findings – Remediation strategy (mine gas)

Respondent 1: Generally Building Standards will review site investigations/geotechnical reports and establish what Characteristic Situation has been identified and the protection measures that have been proposed (if any). Details/plans of protection measures would then be assessed that they are suitable and in accordance with relevant standards (typically BS 8485 and radon guidance etc). Table 2c appears to cover general process.

Respondent 2: Point 8a: Perhaps re-word to recommend verification of decommissioning, which is not routinely requested at present.

Respondent 6: Footnote 4 doesn't appear to be detailed. Presented in question 13.

Respondent 5: We are not routinely made aware of any foundation design changes that would impact mine gas risk. Please refer to comments in 5.39 to 5.40.

Table 2d: Detailed peer review findings – Verification report (mine gas)

Respondent 1: Common ways to establish if protection measure have been suitably constructed would be by individual plot "sign-offs" by specialist contractors or site engineer (and maybe inspection by BS case officer if simple designs). A general/final verification report may not be produced/available until site is completed, so require specific evidence for each plot requiring completion certificate acceptance.

Respondent 2: Point 1: On some larger sites, the developer will ask the local authority to accept phased verification and sign-off of individual sets of plots. This can usually be accommodated, but requires extra vigilance on the part of the council to ensure all requirements are met.

Point 3: see comment in relation to 5.43 to 5.47 above.

Respondent 5: Point 2. – We are not routinely made aware of any foundation design changes that would impact mine gas risk. Please refer to comments in 5.39 to 5.40.

Point 3. Agree that verification should be completed in accordance with CIRIA C735 and other relevant technical guidance, etc. However in our experience, we don't always get information submitted in accordance C735 and it would be very difficult for Falkirk Council to insist on full compliance to C735, without mandatory statutory guidance/regulations specifically in relation to mine gas issues being enforceable.

Points 4 to 11. Detailed review points but in reality as above comments….

Also in small scale development such as extensions – what would be the advice from you/Government on appropriate verification of installation of gas remedial measures? Ideally would be a specialist certified under GPVS scheme but in reality this could prove economically prohibitive for small development and often it is the builder/contractor who verifies with photographic record and written certification. I can't think of many sites in which a certified specialist has verified gas remedial measures. Perhaps this is something that the private sector consultants and contractors should push for and raise awareness of necessity to clients. We currently cannot enforce this requirement easily or practically.

Table 3 Mandatory BS Technical Standard 3.1/3.2 needs updated ASAP to include consideration of all mine gases.

Extra comments

Comments in relation to Annex C – process flowchart:

Respondent 2: Please note: the CLO/EHO doesn't discharge planning conditions (central column), they can only make recommendations to the planning department (and building control).

I feel this diagram is over-complicated and would benefit from reflecting the phased approach (desk study, ground investigation, remedial action, verification) consistently across all three columns.

Respondent 5: Please note: The Contaminated Land Team (SCLO and CLOs) don't discharge planning conditions (central column), we only make recommendations to Development Management (Planning & Building Standards) that the planning or building warrant application can be purified in relation to general contaminated land conditions .

The flowchart is very detailed and perhaps over-complicated and would benefit from reflecting the phased approach (desk study, ground investigation, remedial action, verification) consistently across all three columns. The Contaminated Land Team's review process is similar for both Planning and Building Standards consultations and could be linked between all three columns. We don't review BS8485 design reports and drawings in significant detail as not our area of expertise. In addition we regularly don't receive Phase 1, 2, 3 or 4 reports prior to planning applications being approved (usually subject to conditions attached including CL conditions (as detailed in comments section of 5.23 to 5.25).