BUCKHILL COLLIERY SPOIL TIP DERWENT FOREST, BROUGHTON MOOR

INSPECTION REPORT 2009/10

GC20549/G1/02 Issue: Rev. A, June 2010

Undertaken For:

Allerdale Borough Council Cumbria County Council NWDA

Inspection of Buckhill Colliery Spoil Tip Derwent Forest, Broughton Moor

O.S.G.R. 305400E, 531900N

DOCUMENT VERIFICATION

Report Reference: GC20549/G2/02 Issue: Rev. A Date: 15/VI/10

Prepared by: S.J.J.Ferley BSc. MSc. CEng. MICE FGS Principal Geotechnical Engineer (For and on behalf of Capita Symonds Ltd.) Checked by: M.W.Penny BEng FGS Senior Geotechnical Engineer (For and on behalf of Capita Symonds Ltd.) Approved by: M.Briggs BSc, CEng, MICE Project Manager (For and on behalf of Capita Symonds Ltd.)

Revision History

Revision Date Description Prepared Checked Approved

0 31/III/10 SJJF MWP MB A 15/VI/10 Amendment to update §4.2.8 SJJF MWP MB

This document has been prepared by Capita Symonds Limited within the terms of the Contract with the Client to whom this document is addressed. Capita Symonds Limited disclaims any responsibility to the Client and others in respect of matters outside the scope of the said contract. No person other than the Client and their professional advisors shall rely on it in any respect and no duty of care shall be owed to any such third party by Capita Symonds Limited.

This document is of UK origin and is © Capita Symonds Limited. The contents of this document shall not in whole or in part be stored in any retrieval system nor be reproduced or transmitted in any form by photocopying or any optical, electronic, mechanical or other means, without the prior written permission of the Managing Director, Capita Symonds Limited, 1 Proctor Street, London WC1V 6DW.

Capita Symonds, Kingmoor Business Park, Carlisle, Cumbria. CA6 4SJ Derwent Forest Three Year Holding Programme Cumbria County Council Buckhill Colliery Spoil Tip Inspection Report

CONTENTS ...... PAGE

1.0 INTRODUCTION ...... 1 1.1 BACKGROUND ...... 1 1.2 PREVIOUS INVESTIGATIONS ...... 1

2.0 SITE DESCRIPTION ...... 2 2.1 GENERAL ...... 2 2.2 GEOLOGY ...... 2 2.3 MINING HISTORY ...... 2

3.0 INSPECTION RESULTS ...... 3 3.1 DESK BASED RESEARCH ...... 3 3.2 SITE OBSERVATIONS ...... 4 3.3 LABORATORY TEST RESULTS ...... 4

4.0 ENGINEERING ASSESSMENT AND RECOMMENDATIONS ...... 5 4.1 TIP STABILITY ...... 5 4.2 CONCLUSIONS AND RECOMMENDATIONS ...... 5

APPENDICES

APPENDIX A: MAPS AND PLANS A/01 Site Location A/02 Layout Plan of Spoil tip

APPENDIX B: LABORATORY TEST RESULTS

APPENDIX C: PHOTOGRAPHS

APPENDIX D: SOURCES OF INFORMATION D/01 Published Information D/02 General Sources of Information D/03 Ground Investigation Reports D/04 Computer Programs D/05 Standards, Statutes and Guidance on Statutes

CAPITA SYMONDS Report GC20549/G1/02 Carlisle i Rev. A: 15/VI/10 Derwent Forest Three Year Holding Programme Cumbria County Council Buckhill Colliery Spoil Tip Inspection Report

1.0 INTRODUCTION

1.1 BACKGROUND

1.1.1 At the request of Allerdale Borough Council work was carried out on behalf of Allerdale Borough Council, Cumbria County Council and the Northwest Regional Development Agency, (The Clients) to inspect the spoil tip at the former Buckhill Colliery and assess the current condition. The tip is located in a large area of former MOD land near Broughton Moor, Cumbria, O.S. grid reference (NY) 305735E, 531945N.

1.1.2 The inspection regime required as part of the commission involves repeat visits annually for a total of three years. The subject of the current report is the second visit undertaken, in March 2010.

1.1.3 Existing desk-based information was researched as part of the study. This information is referenced in the relevant sections of the report, and a list of sources of information is included in Appendix C.

1.1.4 As part of the study site visits were undertaken between 6th and 13th January 2009 and 15th to 18th March 2010 to inspect the spoil tip and its surroundings, and to confirm the topography of site.

1.1.5 The comments given in this report and the opinions expressed assume that the site conditions do not vary outwith the extents revealed by this investigation. There may be, however, conditions within the site, particularly in relation to moisture content changes and weathering, which have not been disclosed by the investigation and consequently have not been considered in this report. Capita Symonds accepts no liability for the completeness or accuracy of third party records.

1.1.6 This document has been prepared by Capita Symonds Limited within the terms of the Contract with the Clients to whom this document is addressed. Capita Symonds Limited disclaims any responsibility to the Clients and others in respect of matters outside the scope of the said contract. No person other than the Clients, their professional advisors, and Beneficiaries under the Deed of Warranty shall rely on it in any respect and no duty of care shall be owed to any such third party by Capita Symonds Limited.

1.2 PREVIOUS INVESTIGATIONS

1.2.1 Reference was made to the Coal Authority, but no information regarding the spoil tip was located within their archives.

1.2.2 Capita Symonds have carried out investigations at the site in the past, including the determination of strength parameters for the spoil material. Results from this investigation are included in Appendix B.

CAPITA SYMONDS Report GC20549/G1/02 Carlisle 1 Rev. A: 15/VI/10 Derwent Forest Three Year Holding Programme Cumbria County Council Buckhill Colliery Spoil Tip Inspection Report 2.0 SITE DESCRIPTION

2.1 GENERAL

2.1.1 The site is located near to Broughton Moor in West Cumbria at O.S.G.R. (NY) 305735E, 531945N. The site location is shown on Figure A/01.

2.1.2 The area is mixed in character, generally thickly wooded with conifer plantations in the Centre and West of the site, with rough gorse thickets to the North, and open grazing land to the South and East. Much of the site has been used for munitions storage from the late 1930’s when the Admiralty developed the facility until closure of the depot in the early 1990’s, and many storage magazines still remain, although in varying states of dereliction. The majority of the area in all some 300ha, including the former Buckhill Colliery, is ring fenced by concrete post and wire mesh fencing.

2.2 GEOLOGY

2.2.1 The superficial geology beneath the Made Ground of the spoil tip is indicated on the 1:50,000 and 1:10,000 scale maps published by the Geological Survey to consist of Glacial Till (Boulder Clay) of Devensian age. The Glacial Till is essentially composed of a heterogeneous unsorted mixture of lithology ranging from cobble and gravel down to a matrix of relatively impermeable boulder clay with isolated lenses of more sandy or gravelly material. The overall thickness of the Glacial Till varies significantly across the site in a complex manner, and the results of previous ground investigations indicate a superficial thickness varying from a few metres to up to thirty metres. Drift is generally thinner towards the North East of the site, but significant post-glacial erosion is evidenced by the deeply incised gills crossing the site, where it may be conjectured that the drift cover is thinner at the base of these valleys. The presence of buried pre-glacial stream channels where thicker drift occurs cannot be discounted.

2.2.2 The geological map shows that the site lies on solid geology of the Coal Measures, part of the Carboniferous. The Coal Measures are formed from superimposed cyclothems of shale, siltstone, coal and sandstone. The area is traversed by several intersecting major fault sets, leading to complexities in interpreting the precise correlation of cyclothems between adjacent faulted blocks. The fault zones between adjacent blocks will also cause significant disruption due to jointed and locally shattered zones. In addition, over the area of the site the cyclothem horizons may vary significantly, with individual units lensing out. It is known that local washouts or “nips” occur in coal seams in the area.

2.3 MINING HISTORY

2.3.1 Coal mining has historically been undertaken in the area by shallow methods (“bell pits”) and deeper underground mining methods, predominantly associated with the Buckhill Colliery. The area became a Ministry of Defence logistical base in the late1930’s: this involved closure and partial removal of the Buckhill Colliery in the centre of the site.

CAPITA SYMONDS Report GC20549/G1/02 Carlisle 2 Rev. A: 15/VI/10 Derwent Forest Three Year Holding Programme Cumbria County Council Buckhill Colliery Spoil Tip Inspection Report 2.3.2 The underground network of shafts, tunnels and stopes may affect groundwater movement, and it known that a significant discharge occurs at Ewanrigg, Maryport, through an interconnecting adit. Movement of significant volumes of mine water may occur, often at high hydraulic head: mobile groundwater may act as a trigger for rapid collapse of poorly capped or infilled mine shafts, or shallow workings.

3.0 INSPECTION RESULTS

3.1 DESK BASED RESEARCH

3.1.1 The primary sources of information concerning potential abandoned mineshafts are historic Ordnance Survey maps, large scale geological maps, and historic air photographs dating from the mid 1940’s. As a first pass assessment these sources of information were scanned, and then plotted and compared to the current site layout using GIS.

3.1.2 Historic air photographs obtained from the National Monuments Record office were examined stereoscopically to assess the changes that have occurred to the spoil tip since closure of Buckhill Colliery. Three ages of photography were studied, 1946 at 1:10,000 scale, 1950 at 1:10,000 scale, and 1985 at approximately 1:3,000 scale.

3.1.3 Detailed examination of the different ages of mapping and photography confirm the gradual expansion of the spoil heap by end tipping away from the Upcast shaft location in a South Westerly direction. The maximum extent of the tip occurred immediately prior to closure of the mine. A mineral railway passed in cutting through the tip in a North-South direction to service a former coking oven: this now forms a macadam road joining the Northern and Southern halves of the site.

3.1.4 Air photographs from 1946 indicate that the West corner of the tip was excavated between 1939 and 1946. It is likely that the excavated material was used either to construct the blast mounds around some of the magazine stores, or to provide infill for Upcast shaft. Investigation of the Downcast shaft indicates that the shaft is still open over the greater part of its depth.

3.1.5 Excavations into the toe of the South Eastern side of the tip were completed prior to 1946 in order to accommodate a line of six small laboratory type buildings.

3.1.6 Air photographs taken of the area in 1985 show work in progress excavating the North Western side of the spoil tip. It is believed that this was used to construct further blast bunds around magazines, undertaken by the American government who operated the base at the time.

3.1.7 The existing configuration of the tip has a large excavation on the North corner, undertaken after 1985. A car park area now covered in demolition refuse now occupies what was the Northern edge of the spoil tip. This work also must have been completed post 1985.

3.1.8 The outline of the tip is indicated on Figure A/02. General photographs are included in Plates 1 and 2

CAPITA SYMONDS Report GC20549/G1/02 Carlisle 3 Rev. A: 15/VI/10 Derwent Forest Three Year Holding Programme Cumbria County Council Buckhill Colliery Spoil Tip Inspection Report 3.2 SITE OBSERVATIONS

3.2.1 The South Eastern and South Western faces of the tip stand at an angle of between 35º and 40º, and are thickly vegetated with gorse and occasional Scots Pine saplings over a ground cover of sparse grass. It is believed that these faces are standing at the natural angle of repose of the material when first tipped. No signs of potential instability were observed at the time of the site inspection, although debris was noted on the macadam surfaced road at the toe of the tip. It is not obvious where this material originated, and there is no sign of loss of material from the crest of the slope: the debris may the result of horseplay on the part of trespassers.

3.2.2 The North Western face of the tip, and a large part of the extreme Northern corner, are standing at overall angles in excess of 45º: these slopes are the result of excavations carried out from the 1940’s to the 1980’s, and are largely less densely vegetated or clear of vegetation. The upper parts of the slope are vertical or sub-vertical, and in some places have a distinct overhang at the crest of the slope, formed by roots of vegetation growing on the plateau at the top of the tip. The lower part of the slope is formed by loose debris resting at an angle of 40º to 45º. Many signs of continuing slippage were observed.

3.2.3 The road cutting through the tip is lined by brick masonry walls 1m to 1.5m in height retaining the toe of the tip. These are in poor condition, with spalling and disintegrating bricks, and longitudinal cracks along the bed joints running the full length of the wall. (Plates 3 and 4)

3.2.4 There is no evidence of water seepage on the faces of the spoil tip, but a pond at the Eastern corner is fed by seepage from the toe of the tip and from the backfill to the retaining wall.

3.3 LABORATORY TEST RESULTS

3.3.1 Four trial pits were excavated in the side slopes of the tip by hand in 2005. Bulk samples of the tip material were recovered and sent to the laboratories of Allied Exploration and Geotechnics in Chester-le-Street, County Durham. The laboratory is UKAS registered, number 1367.

3.3.2 The samples were tested for particle size distribution, natural moisture content, and shear strength by large shear box testing. Results are included in Appendix C.

3.3.3 The results of particle size distribution testing indicate that the material is a clayey very gravelly SAND/very sandy GRAVEL. The gravel is fine to medium, and generally tabular, of predominantly Mudstone, but including Slate, Brick and burnt Shale.

3.3.4 Natural moisture contents ranged from 9% to 14%.

3.3.5 Five no. shear box test were undertaken in the laboratories of the University of Newcastle upon Tyne. The results of tests carried out at natural moisture content provided angles of internal friction that ranged from 32º to 43º, with a mean of 38º.

3.3.6 Saturation prior to testing raised the moisture content to between 20% and 29%. The corresponding peak angle of internal friction reduced to a mean of 31º.

CAPITA SYMONDS Report GC20549/G1/02 Carlisle 4 Rev. A: 15/VI/10 Derwent Forest Three Year Holding Programme Cumbria County Council Buckhill Colliery Spoil Tip Inspection Report 4.0 ENGINEERING ASSESSMENT AND RECOMMENDATIONS

4.1 TIP STABILITY

4.1.1 In its existing configuration the Southern slopes of the tip are considered to be reasonably stable provided pore water pressure does not accumulate. The existing vegetation will also provide some reinforcement to the near surface layers of the tip.

4.1.2 The Northern slopes are the result of excavation into the original tip, and are unstable, with evidence of continued surface slippage and an overhang at the crest of the slope.

4.1.3 The brick masonry retaining wall supporting the Eastern side of the tip is in very poor condition, and is potentially unstable.

4.1.4 No significant deterioration of the tip was observed during the 2010 inspection. Small scale slippage and gradual erosion of the exposed surfaces continues.

4.2 CONCLUSIONS AND RECOMMENDATIONS

4.2.1 Reference to the Occupiers Liability Acts of 1957 and 1984 indicates that the Client owes a common duty of care to persons entering any of the Derwent Forest site, either inside or outside the security fence, and that to a different extent such duty is owed to visitors (persons entering the site in pursuance of an explicit or legally implied right to do so) and trespassers (persons who have no such explicit or implied right). The 1957 Act specifically concerns “visitors”, and the 1984 Act “trespassers”.

4.2.2 The common duty of care under the 1957 Act is a duty to take such care as in all the circumstances of the case is reasonable to see that the visitor will be reasonably safe in using the premises for the purposes for which he is invited or permitted by the occupier to be there.

4.2.3 A slightly lesser duty is enjoined under the 1984 Act. A duty of care exists if the occupier is aware of the existence of a danger, has “reasonable grounds to believe” that a person may come into the vicinity of the danger “whether the other has lawful authority for being in that vicinity or not”, and “the risk is one against which, in all the circumstances of the case, he may reasonably be expected to offer the other some protection”. In this circumstance, the duty is to take such care as is reasonable in all the circumstances of the case to see that nobody suffers injury on the premises by reason of the danger concerned.

4.2.4 If appropriate the 1984 Act allows the discharge of the duty of care by “taking such steps as are reasonable in all the circumstances of the case to give warning of the danger concerned or to discourage persons from incurring the risk”. The 1957 Act explicitly states, and some case law suggests, that account should be taken of children being less careful than adults, as they have a different concept of danger, and are naturally more inquisitive. Where a warning has been given it will not absolve the occupier of liability, unless in all the circumstances it was enough to enable the visitor to be safe. The issue would be whether the warning was sufficient to enable the visitor to be reasonably safe, and in cases such as young children or the illiterate warning signs may not be adequate protection. Any warning must enable an entrant onto the premises to take reasonable precautionary measures.

CAPITA SYMONDS Report GC20549/G1/02 Carlisle 5 Rev. A: 15/VI/10 Derwent Forest Three Year Holding Programme Cumbria County Council Buckhill Colliery Spoil Tip Inspection Report 4.2.5 Under the Coal Industry Act 1994 ownership of coal in mine spoil tips does not rest with the Coal Authority.

4.2.6 It is recommended that specialist legal advice should be sought regarding detailed interpretation of the Acts referenced above. The following recommendations are made to provide mitigation measures that are considered reasonable in the circumstances prevailing at the Derwent Forest site.

4.2.7 It is recommended that the tip is inspected on a six monthly basis initially, in order to accumulate sufficient information to determine the baseline condition against which future deterioration can be assessed: this inspection should be carried out by suitably experienced geotechnical personnel.

4.2.8 The tip in its current configuration is unstable on the Northern faces, and there is an immediate danger of collapse of the overhanging and vertical parts of the slope. There is currently a post and wire fence surrounding the area.

4.2.9 It is recommended that in the longer term the tip should be re-profiled to a more stable shape, to be based on a design in accordance with the shear strength parameters obtained for the tipped material.

4.2.10 In the case of parts of the tip which were inaccessible at the time of the walkover survey, estate management operations which may expose these locations should be notified to a geotechnical specialist, and the situation reviewed in order to update the understanding of the potential risk involved at the location.

4.2.11 If estate management works are proposed in the vicinity of the spoil tip, the advice of a geotechnical specialist should be sought at an early stage, in order that appropriate risk management measures are designed for the work.

4.2.12 It was noted whilst carrying out other geotechnical inspection work around the site that there are other colliery spoil tips within the Client’s land ownership. Under the Mines and Quarries (Tips) Act 1969 the owners have a legal obligation to carry out regular inspections of abandoned mine and quarry tips: it is therefore recommended that inspections of these tips be carried out forthwith.

CAPITA SYMONDS Report GC20549/G1/02 Carlisle 6 Rev. A: 15/VI/10

APPENDIX A: MAPS AND PLANS

A/01 Site Location A/02 Layout Plan of Spoil Tip

.

Buckhill Colliery

Legend Land Ownership Boundary

Reproduced from, or based on, Ordnance Survey map material with the permission of the Controller of Her Majesty's Stationery Office. Crown Copyright, Licence No. 10009596 Cumbria County Council. Unauthorised reproduction infringes Crown Copyright and may lead to prosecution or civil proceedings. Scale: DERWENT FOREST THREE YEAR HOLDING REGIME Kingmoor Business Park INSPECTION OF COLLIERY SPOIL TIP Carlisle 1:50,000 CA6 4SJ Site Location Fig. No.: GC20549/G1/A/01 Date:27/II/09 Drawn:S.J.J.F. Checked:M.W.P. .

Extent post 1985

Extent at 1946

Retaining Wall

Extent at 1938

Area of seepage and ponding

Reproduced from, or based on, Ordnance Survey map material with the permission of the Controller of Her Majesty's Stationery Office. Crown Copyright, Licence No. 10009596 Cumbria County Council. Unauthorised reproduction infringes Crown Copyright and may lead to prosecution or civil proceedings. Scale: DERWENT FOREST THREE YEAR HOLDING REGIME BUCKHILL COLLIERY SPOIL TIP INSPECTION Kingmoor Business Park Carlisle 1:5,000 CA6 4SJ Layout of Spoil Tip Fig. No.: GC20549/G1/A02 Date:27/II/09 Drawn:S.J.J.F. Checked:M.W.P.

APPENDIX B: LABORATORY TEST RESULTS

APPENDIX C: PHOTOGRAPHS

Derwent Forest Three Year Holding Programme Cumbria County Council Buckhill Colliery Spoil Tip Inspection Report

Plate 1: General view of Spoil Heap from the West.

Plate 2: View of excavated area in Northern corner of tip

CAPITA SYMONDS Report GC20549/G1/02 Carlisle C1 Rev. 0: 31/III/10 Derwent Forest Three Year Holding Programme Cumbria County Council Buckhill Colliery Spoil Tip Inspection Report

Plate 3: General view of retaining wall in road cutting.

Plate 4: Close up of degraded brick masonry in retaining wall

CAPITA SYMONDS Report GC20549/G1/02 Carlisle C2 Rev. 0: 31/III/10

APPENDIX D: SOURCES OF INFORMATION D/01 Published Information D/02 General Sources of Information D/03 Ground Investigation Reports D/04 Computer Programs D/05 Standards, Statutes and Guidance on Statutes

Derwent Forest Three Year Holding Programme Cumbria County Council Mine Entry Inspection Report

D/01: References to Published Information

Author Reference Publisher Information Obtained 1:10,000 Geological Map Sheet British Geological Detailed geology of area of NY03SW, Combined Solid & Survey interest. Drift edition 1:10,000 Geological Map Sheet British Geological NY03SW, Locations of Survey Boreholes and Shafts Geological Map Sheet 22, British Geological General geology of area of Maryport: 1:50,000 scale Solid & Survey, 1995 interest. Drift 1st 2nd and 3rd Edition 1:2,500 Ordnance Survey Previous uses of the site scale plans since 1864. Digital and Landline map data Ordnance Survey reproduced at various scales HMSO, 1999 Barnes, R.P.; Geology of Workington & British Geological Young, B.; Maryport Survey, 1988 Frost, D.V.; Technical Report No. WA/88/3 Land, D.H.

CAPITA SYMONDS Report GC20549/G2/02 Carlisle D1 Rev. 0: 31/III/10 Derwent Forest Three Year Holding Programme Cumbria County Council Mine Entry Inspection Report D/02: General Sources of Information

Source Information Obtained British Geological Survey, Report on solid and drift geology of the area of interest: Murchison House, locations and descriptions from abandonment plans (where West Mains Road, available) of shafts and workings. Index of abandonment Edinburgh EH9 3LA plans held. Information based on published 1:10,000 scale geological and thematic maps, field slips and survey work

summarised in BGS Report EE00/1055. Coal Authority No information concerning spoil tip Mining Reports Office, Lichfield Lane Mansfield Nottinghamshire NG18 4RG CAPITA SYMONDS Stereoscopic Air Photographs of area of interest. Geotechnical Group, Kingmoor Business Park, Carlisle CA6 4SJ National Monuments Records Stereoscopic Air photographs at various scales dating from Office, the mid 1940’s Air Photographs Section, Kemble Drive, Swindon SN2 2GZ Cumbria County Council Historic Ordnance Survey maps and plans. Public Records Office, No other relevant archive records known. Alma Block, The Castle, Carlisle CA3 8UR

D/03: Ground Investigation Reports

Source Date Title & Contents Information Obtained Capita Symonds March Phase I Land Quality Background information; Report SS20199 2001 Assessment: Broughton Moor historic and local setting; (Two Volumes) preliminary assessment Allied Exploration 2/XI/05 Buckhill Colliery Samples Laboratory Test Data & Geotechnics Report SLS634:

CAPITA SYMONDS Report GC20549/G2/02 Carlisle D2 Rev. 0: 31/III/10 Derwent Forest Three Year Holding Programme Cumbria County Council Mine Entry Inspection Report D/04: Computer Programs

Program Version & Date Publisher Use ACCESS 9.0.6926 SP-3, Microsoft Maintenance of archive ground 2000 investigation and other databases. ArcMap 9.0, build 535, ESRI GIS 2004 AutoCAD Map 2008 Autodesk Preparation of maps and plans

D/05: Standards, Statutes and Guidance on Statutes

Publisher Number Date Title British Standards BS5930 1999 Code of Practice for Site Investigations Institution Incorporating Amendment No. 1, 2007 HMSO 1957 Occupiers Liability Act HMSO 1984 Occupiers Liability Act

CAPITA SYMONDS Report GC20549/G2/02 Carlisle D3 Rev. 0: 31/III/10