Redhurst Quarry, South Staffordshire, ML7 4NZ Environmental Act 1995 Periodic Review of Old Mineral Permission. Coal Mining Risk Assessment Report

Transcription

1 Redhurst Quarry, South Staffordshire, ML7 4NZ Environmental Act 1995 Periodic Review of Old Mineral Permission Coal Mining Risk Assessment Report Ref: February 2014

2 Ibstock Building Products Ltd Ref: CONTENTS 1.0 INTRODUCTION Background Scope of Work and Study Limitations Data Sources SITE DETAILS AND SETTING Site Vicinity Description GEOLOGICAL ASSESSMENT Geological Setting Geological Setting MINING ASSESSMENT Mining Reports Coal Mines in Vicinity MINE ABANDONMENT PLANS Mining Assessment SUMMARY AND CONCLUSIONS CLOSURE Drawings Drawing 1 Abandonment Plan 9384 (Sheet 4) Drawing 2 Abandonment Plan 9384 (Sheet 5) Drawing 3 Abandonment Plan 9384 (Sheet 7) Drawing 4 Abandonment Plan 9384 (Sheet 6) Drawing 5 Abandonment Plan 9384 (Sheet 8) Drawing 6 Abandonment Plan 9384 (Sheet 4) Drawing 7 Abandonment Plan 9384 (Sheet 3) Drawing 8 Abandonment Plan 9384 (Sheet 9) Drawing 9 Abandonment plan 8840 (Sheet 2) Drawing 10 Abandonment Plan WMOC168 APPENDICES Appendix A Coal Authority Report

3 Ibstock Building Products Ltd 3 Ref: INTRODUCTION 1.1 Background This report has been prepared as part of the review of the existing mineral planning permission (SSEA/10) together with a small extension to the mineral extraction area to enable efficient working at Redhurst Quarry in Staffordshire hereafter referred to as the site. The following sections of the report introduce the site, the assessment works undertaken and their results, along with a preliminary assessment of the mining risk under the site. 1.2 Scope of Work and Study Limitations The purpose of this report is to present the findings of the Coal Mining Risk Assessment in relation to the extraction of mineral from Redhurst Quarry. The objectives of this report are to: Provide information on the geology and mining of the site; including The location and stability of mine entries; The extent and stability of shallow mine workings; Outcropping coal seams and potential for unrecorded mine workings; and Hydrogeology, minewater and mine gas. In addition consideration of the following: If surface coal resources are present, whether extraction of the mineral resource is practicable and viable; Whether Coal Authority permission is required to intersect, enter, or disturb any coal or coal workings during site investigation or development work; and Provide indicative recommendations for any remedial or further detailed investigative works, as required. The work comprised the following phases: Initial Phase A review of historical map records; Acquisition of a Coal Authority Report; Review of Mine Abandonment Plans; A review of information held on British Geological Survey websites; and Collating information about site conditions and assessing the potential mining risks. A site inspection has not been undertaken as part of this commission; however an opportunity has been taken to review publically accessible data. Assessment and Reporting A summary of the published information is presented and this information has been interpreted to assess mining instability risk at site.

4 Ibstock Building Products Ltd 4 Ref: Data Sources This report has been produced following consultation with the sources of information summarised in Table 1. Information Type Table 1 Information Sources Source Geology British Geological Survey (BGS). England & Wales Sheet 154 Lichfield (solid & drift) British Geological Survey Borehole Records Mining Coal Authority Mining Report ( ) Mine Abandonment Plans Coal Authority Web Site aspx

5 Ibstock Building Products Ltd 5 Ref: SITE DETAILS AND SETTING 2.1 Site Vicinity Description Redhurst quarry is located within South Staffordshire approximately 2km north east of Wolverhampton and 1km south east of Cannock. The quarry is situated within the green belt and bordered by agricultural land to the north, west and south and the A462 (Warstone Road) to the east. Much of the quarry is enclosed by a belt of mature trees which form part of the surrounding field boundaries or screening for the nearby motorway M6 and M54 motorways. For identification purposes, the quarry is centred on National Grid reference SJ Redhurst quarry is divided into three areas known as Areas A, B and C. Area A is the largest and most northerly area and the only current operational part of the quarry. Area B is the smallest area and located centrally, whilst Area C is the most southerly area. Mineral extraction is currently taking place within Area A and is progressing in a southerly direction. Unsurfaced haul roads provide access to the extraction area and a number of dewatering and settlement lagoons are situated within the worked quarry void. Soil and overburden that has been stripped to enable mineral extraction is stored in a number of storage mounds within this area. Area A is bordered to the north by Hilton Lane and fields and to the east by Warstone Road. The area is bordered to the south by Area B and to the west by fields and M6 motorway. Area B and the land in this area comprises of vegetation including grass, scrub and a belt of mature trees which enclose this area. Area B is bounded to the north by the mineral extraction taking place in Area A and by Warstone Road (A462) to the east. To the south, Area B is bordered by Hobnock Road whilst fields and M6 border this area to the west. Area C is separated from Area A and B by Hobnock Road which runs in a roughly east to west direction. Area C is bordered to the north by Hobnock Road which provides access directly into this area. Area C is bordered to the east by Bursnips Road, to the south by small fields and to the west by the trees alongside the M54 motorway. Mineral extraction has yet to commence in Area C which comprises of previously developed land. Buildings and structures from the previous use of the area have been removed however some surfacing remains. A traveller s site is located on the eastern side of Area C which is accessed from Bursnips Road. Ground levels prior to mineral extraction were between m AOD. However ground levels within the site vary significantly since mineral extraction commenced. It is proposed to extract mineral to a depth of 50m AOD. 3.0 GEOLOGICAL ASSESSMENT 3.1 Geological Setting The mining risk assessment has been undertaken to address any potential mining impacts that may influence the proposed development. The potential mining impacts and implications of the proposed development have been identified and a mining risk assessment of the site was undertaken. Geological information and maps were obtained from the British Geological Survey and 1:50,000 scale Ordnance Survey maps were reviewed. Additional searches were undertaken from the Coal Authority to address the extent of coal mining undertaken at the site, including Mining Reports, Abandonment Plans and Geological Plans.

6 Ibstock Building Products Ltd 6 Ref: This report gives a detailed review of the mining activity which has taken place on the site and in close vicinity to the site, much of which is in the form of traditional underground mining. The geological setting and mining framework of the development site and surrounding area are described in the following sections. 3.2 Geological Setting Redhurst Quarry is located in an area underlain by Carboniferous strata (Westphalian). The strata are locally and regionally faulted and fractured Drift Geology The extent of the Drift Geology underlying the site is shown on the 1:50,000 Solid and Drift Geology Edition, Sheet 154 for Lichfield, published by the British Geological Survey. The drift geology across much of the site comprises predominantly glacial till (boulder clay), and a small region of alluvium to the north of Area A. The drift geology is typically expected to be between 3 and 10m thick Solid Geology The extent of the Solid Geology underlying the site is shown on the 1:50,000 Solid and Drift Geology Edition, Sheet 154 for Lichfield, published by the British Geological Survey. The solid geology comprises, Etruria Marl (Etruria Formation) consists of red to reddish brown mudstones interbedded with thin beds of sandstone, which overlies the Pennine Middle Coal Measures Formation (PMCM) (Westphalian). The Mitre Fault is located only approximately 50m from the south-western corner of the proposed final excavation. The trend of the fault is approximately north-north-east to south south-west. This fault marks the limit of the eastern extent of the Etruria Marl Formation at this location, with Westphalian Coal Measures present to the east of the fault, immediately below the glacial till and underlying the Etruria Formation to the west. The Lower Coal Measures comprise sandstones, siltstones and coal seams with seatrocks. They tend to occur in upper coarsening cycles with mudstones at the base passing up through siltstone and sandstone to a root bed underlying the coal seam. Thin clayband ironstones with layers of nodules are common in the mudstone beds above the coal seams. blackband or slatyband ironstones also occur Hydrogeological Setting The drift geology in the area comprises predominantly Glacial Till, likely to be between 3 and 10m thick, and generally classified as being of low permeability, firm to stiff clay. The Carboniferous Lower Coal Measures are classified as moderately permeable, which seldom produce large quantities of water for abstraction, but are important for local supplies and in supplying baseflow to rivers.

7 Ibstock Building Products Ltd 7 Ref: MINING ASSESSMENT 4.1 Mining Reports A coal mining report has been undertaken for the site. The site is located within a Coal Mining High Risk referral area. The findings of the report can be summarised as follows: The property is in the likely zone of influence from workings in 10 coal seams at 80m to 410m depth and last worked in In addition the property is in an area where the Coal Authority believes there is coal at or close to the surface. This coal may have been worked at some time in the past. The property is not in the likely influence of any present underground coal workings or future surface mine workings. Within, or within 20 metres of the site there is 1 known mine entries. The property is within the boundary of an opencast site from which coal has been removed by opencast methods. There are no records of gas emissions from the site. The Mining Report is included in Appendix A. 4.2 Coal Mines in Vicinity There are a number of recorded mines and collieries in the vicinity of the site. The seams identified in the Mining Report were worked from Holly Bank Colliery (SJ ). The colliery was opened in the late 1800 s and continued until 1952; three shafts have been identified which were used by the colliery, these are No.5, No.7 & No.15 pit. 5.0 MINE ABANDONMENT PLANS A search of the mine abandonment plans was undertaken for the site and a total of ten plans were identified and assessed as part of this in the mining assessment (Appendix B), the extents of which are shown on the following drawings:-. Drawing No. Abandonment Plan Seam(s) Drawing 1 Abandonment Plan 9384 (Sheet 4) Robins Drawing 2 Abandonment Plan 9384 (Sheet 5) Brooch Drawing 3 Abandonment Plan 9384 (Sheet 7) Eight Feet Drawing 4 Abandonment Plan 9384 (Sheet 6) Four Feet Drawing 5 Abandonment Plan 9384 (Sheet 8) Heathen Drawing 6 Abandonment Plan 9384 (Sheet 4) Yard Drawing 7 Abandonment Plan 9384 (Sheet 3) Five Feet Drawing 8 Abandonment Plan 9384 (Sheet 9) Cinder Drawing 9 Abandonment plan 8840 (Sheet 2) Shallow & Deep Drawing 10 Abandonment Plan WMOC168 Essington Opencast Abandonment Plan 9384 (Sheet 4) Robins Seam Based on the mining plan, the recorded mine workings shown for the Robins Coal Seam partially underlay Areas A and C. Based on evidence from the plans, the seams were worked at between -15m and -22m AOD within the footprint of Areas A and C. The workings are therefore in excess of 66m below the proposed base of the mineral extraction (50m AOD). Hence these workings do not to impact the development. No Risk.

8 Ibstock Building Products Ltd 8 Ref: Abandonment Plan 9384 (Sheet 5 )- Brooch Seam Based on the mining plan, the recorded mine workings shown for the Brooch Coal Seam partially underlay Areas A and B. Based on evidence from the plans, the seams were worked at -67m AOD within the footprint of Area A. The workings are therefore in excess of 115m below the proposed base of the mineral extraction (50m AOD). Hence these workings do not to impact the development. No Risk Abandonment Plan 9384 (Sheet 7) - Eight Feet Seam Based on the mining plan, the recorded mine workings shown for the Eight Feet Coal Seam partially underlay Area A. Based on evidence from the plans, the seams were worked at approximately -100m AOD with the footprint of Area A. The workings are therefore in excess of 150m below the proposed base of the mineral extraction (50m AOD). Hence these workings do not to impact the development. No Risk Abandonment Plan 9384 (Sheet 6) - Four Feet Seam Based on the mining plan, the recorded mine workings shown for the Four Feet Coal Seam partially underlay Area A. Based on evidence from the plans, the seams were worked at -106m AOD within the footprint of Area A. The workings are therefore in excess of 150m below the proposed base of the mineral extraction (50m AOD). Hence these workings do not to impact the development. No Risk Abandonment Plan 9384 (Sheet 8) - Heathen Seam Based on the mining plan, the recorded mine workings shown for the Heathen Seam partially underlie Areas A, B and C. Based on evidence from the plans, the seams were worked at -127m AOD beneath Area A, at -158m AOD beneath Area B and at -2m AOD beneath Area C. The workings are therefore a minimum of 52 metres below the proposed base of the mineral extraction (50m AOD). Hence these workings do not to impact the development. No Risk Abandonment Plan 9384 (Sheet 4) - Yard Seam Based on the mining plan, the recorded mine workings shown for the Yard Seam do not extend below the proposed development are therefore these workings do not to impact the development. No Risk Abandonment Plan 9384 (Sheet 3) - Five Feet Seam Based on the mining plan, the recorded mine workings shown for the Five Feet Coal Seam partially underlay Area C. Based on evidence from the plans, the seams were worked at -113m AOD within the footprint of Area C. The workings are therefore in excess of 160m below the proposed base of the mineral extraction (50m AOD). Hence these workings do not to impact the development. No Risk Abandonment Plan 9384 (Sheet 9) - Cinder Seam Based on the mining plan, the recorded mine workings shown for the Cinder Seam do not extend below the proposed development are therefore these workings do not to impact the development. No Risk

9 Ibstock Building Products Ltd 9 Ref: Abandonment plan 8840 Shallow and Deep Seams Based on the mining plan, the recorded mine workings shown for the Shallow Seam do not extend below the proposed development are therefore these workings do not to impact the development. No Risk Based on the mining plan, the recorded mine workings shown for the Deep Coal Seam partially underlay Area C. Based on evidence from the plans, the seams were worked at -285m AOD within the footprint of Area C. The workings are therefore in excess of 300m below the proposed base of the mineral extraction (50m AOD). Hence these workings do not to impact the development. No Risk Abandonment plan WOC168 Essington Opencast Based on the mining plan, it is evident that opencast operations have taken place along the eastern boundary of Area C. A total of 5 seams were worked in this area (Upper Charles, Middle Charles, Lower Charles, Brooch & Wyrley Yard) to a maximum depth of metres below ground level which is m AOD. There are no records of how the opencast area was restored, it is assumed that it was simply backfilled with overburden material. Whilst the former extraction operations do not present a direct mining risk to the proposed development, the nature of the backfilled material should be considered as part of any extraction envelope design or future use of the site Mine Entries There is one recorded mine entry within the quarry site boundary, based on Coal Authority records, the position of the mine entry is shown on the drawing within Appendix A. There is no record of what steps, if any, have been taken to treat the mine entry. There is no information relating to whether the mine entry is a shaft, an adit, an air vent or an exploration hole etc. There may be possible mine gas emissions associated with the mine entry along with issues related to groundwater within the mine entry. A review of publically available borehole records indicates that there is a borehole located at approximately the same position as the recorded mine entry. It is therefore possible that it is simply a borehole and not actually a mine entry. Based on the position of the mine entry, within the boundaries of the development and the lack of information regarding what the mine entry actually is, along with the risks associated with mine gas and mine water, if it is intercepted during quarry operations, it is therefore considered to pose a Medium Risk. There is a possibility that there are further unrecorded shafts but given the volume of information for the site (abandonment plans, mine entries, borehole records, etc) it is considered unlikely that there are unrecorded entries, this is therefore considered to pose a Low Risk. However, if during construction works a mine entry is uncovered then this will need to be treated and capped in accordance with Coal Authority guidance Unrecorded workings Information contained on abandonment plan 9384 Sheet 8 (Heathen Seam) indicates that there is a shallower seam in the geological sequence named the Seven Feet Seam which is recorded on one of the mine shafts 20 yards above the Robins Seam. Assuming the position

10 Ibstock Building Products Ltd 10 Ref: of the seam remains constant with the Robins Seam, the workings would be at approximately 3m AOD. The workings, if they are extend beneath the proposed development, would therefore be in excess of 45m below the proposed base of the mineral extraction (50m AOD). Hence these workings would not to impact the development. No Risk 5.2 Mining Assessment Abandonment plans confirm that underground mining has taken place beneath the site in 7 No. worked seams of coal. A mine entry is present within the boundary of Area C. Based on abandonment plans 9384 and 8840 the Robins, Brooch, Eight Feet, Four Feet, Heathen, Five Feet & Deep Coal Seams are partially developed under the site, from depths of -15m AOD to -250m AOD. The workings of the Robins Coal are the shallowest known workings present at -15m AOD and as the base of clay extraction is 50m AOD the workings are unlikely to impact the site. 5.3 Risk Assessment For the purposes of this mining risk assessment all aforementioned sources (abandonment plans, coal authority reports, available borehole records etc) have been assessed and assigned a relative degree of risk to highlight potential areas of concern based on identified features and potential future actions. Table 2 Risk Assessment Risk Status No Risk Low Risk Medium Risk High Risk Action Identified feature(s) not considered to pose any risk to proposed development. No further action required. Identified feature(s) are unlikely to pose a risk to the proposed development and further action may be required such as intrusive site investigation works. Identified feature(s) may present a risk to the proposed development and further actions are likely to be required including but not limited to an intrusive site investigation works and potentially ground improvement works. Identified feature(s) present a risk to the proposed development and further actions are required including but not limited to an intrusive site investigation works and potentially ground improvement works. Based on the Mine Abandonment plans, the depth of the shallowest recorded seam beneath the site (Robins Seam) is -15m AOD so risk from past mine workings must be considered No Risk. However, there is a recorded mine entry within the boundary of Area C, which is considered to present a medium risk to the development.

11 Ibstock Building Products Ltd 11 Ref: In addition there are risks associated with the possible presence of mine gas and or mine water related to the presence of the mine entry. Based on the above, it is suggested that investigatory works are undertaken to locate the position of the mine entry (which may turn out to be a borehole) and try and determine it s function, size, any capping or treatment detail. It is further recommended that the extents of the former opencast workings are delineated to allow an appropriate pit design to be determined. Any future investigation on this site will require Coal Authority permission to undertake drilling into Coal Measures.

12 Ibstock Building Products Ltd 12 Ref: SUMMARY AND CONCLUSIONS The mining assessment has established the site has been subject to underground coal mining. Based on the evidence from the mining abandonment plans seven seams have been extracted beneath the site, at depths which will not impact the proposed development. Based on the Risk Assessment undertaken for the site it has been determined that the known underground former mine workings are present at a depth in excess of 50m below the likely base of the proposed mineral extraction. It is therefore suggested that the risks presented by these workings can be classified as No Risk. There is a possibility that shallower unrecorded workings are present at depth in excess of 45m below the base of the proposed mineral extraction. It is therefore suggested that the risks presented by these workings can be classified as No Risk. There is a possibility that a mine entry exists within the boundary of the development site which represents a Medium Risk. It is recommended that investigatory works are undertaken to locate this entry and any possible impacts it may have on the proposed development. It is also suggested that the position of the former opencast operations are determined to allow appropriate design of the proposed development.

13 Ibstock Building Products Ltd 13 Ref: CLOSURE This report has been prepared by Consulting Limited with all reasonable skill, care and diligence, and taking account of the manpower and resources devoted to it by agreement with the client. Information reported herein is based on the interpretation of data collected and has been accepted in good faith as being accurate and valid. This report is for the exclusive use of Ibstock Building Products; no warranties or guarantees are expressed or should be inferred by any third parties. This report may not be relied upon by other parties without written consent from. disclaims any responsibility to the client and others in respect of any matters outside the agreed scope of the work.

14 Ibstock Building Products Ltd Ref: APPENDICES Appendix A Coal Authority Report