Technical Report WA/92/33

A geological background for planning and development in the ‘Black Country’

J H Powell, B W Glover and C N Waters

BRITISH GEOLOGICAL SURVEY

TECHNICAL REPORTWA/92/33 Offshore Geology Series

A geological background for

Cover illustrations planning and development in the Front Cover View of the Dudley Canal and Cobb’s Pit, Warrens Hill Park, Dudley. ‘Black Country’ BackCover Top;Severn Sister’s Cavern, Wren’s Nest Nature Reserve (SSSI). Galleries and roof- supporting pillarsin workmgs of the J H Powell, B W Glover and C N Waters steeply dipping Much Wenlock Limestone (Lower Quarried Limestone). Contributors Bottom; Basal Coal Measures conglomerate resting Engineering geology A Forster unconformably on, and Hydrogeology S W Fletcher, E L Parry and C A Thomas overstepping steeply dipping Silurian strata. The Hayes; archival (National Rivers Authority) photograph, 1921. Planning B R Marker Geographical index UK, Central England, West Midlands

Subject index Geology, planning, thematic maps, mineral resources, hydrogeology, mining, engineering geology.

Production of this report was partly funded by the Departmentof the Environment, but the views expressed in it are not necessarily those of the Department

Maps and diagrams use topography based on Ordnance Survey mapping

Bibliographic reference POWELL,J H , GLOVER,B W, and WATERS,C N. 1992. A geologi- cal background for planning and development in the ‘Black Country’. British Geological Survey Technical ReportWAl92133.

0NERC copyright 1992 Keyworth,Nottingham British Geological Survey1992 BRITISH GEOLOGICAL SURVEY

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Printed by J EC Potters & Sons Ltd, Stamford, Lincolnshire CONTENTS FIGURES

ExecutiveSummary 1 1. Sketch map showing the regionalsetting of the study area 1 Limitations 3 2. Published BGS geological mapsof the Black Country area4 Introduction 5 3. Map of the Black Country study area showingthe Objectives 5 borough boundaries, component BGS1 : 10 000-scale Sources of information 5 and 150 000-scale maps and the boundaryof the exposed coalfield 7 The Thematic Geological Maps 6 4. Generalised bedrock geological mapof the Black Country18 GeographicalBackground 9 5. Generalised vertical section of the strata 21 6. Generalisedhorizontal cross-sections 22 PlanningBackground 10 7. Schematic diagram showing the generalised Introduction10 stratigraphical relationships of the Carboniferous ThePlanning System 10 rocks in the Black Country 23 DevelopmentPlans 10 8. Comparative vertical sections through the Coal Control of Development10 Measures26 Informationrequirements 11 9. Generalised structural map of the Black Country Strategic planning issues 12 showing the major faults and folds 29 10. Generalised distribuition of superficial Drift Key Issues for which geological informationis deposits in the area 32 required 14 11. Cartoon showingthe relationship of Drift deposits in Housing,construction and infrastructure 14 theBlack Country 33 Derelictland 14 12. Generalised distribution of Made Ground and Worked Minerals15 Ground36 Waterresources 15 13. Mineral resources of the Black Country 39 Wastedisposal 16 14. Historical trends of mining reflected in the Conclusion16 distribution of working mines. A, 1861: B, 1902: C, 194540 Geologicalbackground 17 15. Summary of various types of mining methods 41 Bedrockgeology and structure 17 16. Generalised distribution of the engineering Superficial (drift) deposits 33 geological categoriesof superficial (drift) Made Ground, fill and worked ground 35 deposits50 17. Generalised distribution of broad engineering Geological Resources and Constraints Relevant to geological categoriesof the bedrock in the Black Planningand Development 38 Country 58 Introduction , 38 18. Generalised developmentof general subsidence due Geologicalresources 38 to collapse of disused workings 66 Mineralresources 38 19. Diagramatic developmentof mining voids and crown Groundwaterresources 45 holes68 Additionalresources 45 Geological constraints 48 Properties and stability of bedrock and superficial TABLES resources48 Groundwater: potential for contamination andrising 1. Main sources of archival information 5 groundwater levels 65 2. Summary of previous Geological Survey/BGS Human activities affecting ground conditions 65 geologicalmapping 6 3. Publication of small-scale (1 inchto 1 mile) Glossary 7 1 geological maps covering the Black Country 6 4. DevelopmentPlans 11 Acknowledgements 72 5. Selected documents giving planning advice and guidance 12 TechnicalAppendices 73 6. Amount of derelict land justifying reclamation at Appendix 1. Datasources 73 1 April 1988, by type, in the metropolitan boroughsof Appendix 2. List of mineral industry operators 74 the BlackCountry 14 Appendix 3. List of statutory bodies relevantto planning 7. Amounts of derelict land reclaimed betweenApril, anddevelopment 74 1982 and March 1988in the metropolitan boroughs Appendix 4. List of 1: 10 000-scale geological maps and of the Black Country 15 accompanyingTechnical Reports 75 8. Present bedrock geological nomenclature comparedto theprevious schemes 19 References 76 9. Principal bedrock geologicalunits in the Black Country area and their economic uses 20 10. Subdivisions of the Much Wenlock Limestonein the BlackCountry 24 11. Carboniferous rocks present inthe Black Country PLATES and their economic importance 28 12. Approximate thicknessof the principal coal seams 1. Warren’s Hall Park, Dudley. Viewof the Dudley in the South Staffordshire coalfield 28 Canal (lookingnorth-east) near the entrance of the 13. Details of the Superficial (Drift) Deposits in the Black Netherton Tunnel. Cobb’s EnginePit and two pit Country34 mounds are relics of coal workings at Windmill End 14. Types of former quarries andpits in the Black Colliery. The high ground representsthe dolerite Country area andthe constraints that they may outcrops at Rowley Regis and TansleyHill. The present to development46 steep slope inthe vicinity of Cobb’s EnginePit 15. Mineral extraction and waste disposalpossibilities in marks the line of the Russell’s Hall Fault 9 theBlack Country 47 16. Geological Sites of Special Scientific Interest (SSSI) 2. Exhumed ‘pillar and stall’ workings in the in the Black Country area 48 Stinking Coal; Dibdale Road opencast site 25 17. Major geological constraints to development and their possible risks 49 3. The Thick Coal at Dibdale Road opencast site 25 18. Engineeringgeological categories 52 19. Coefficient of volume compressibility, Mv 53 4. Volcaniclastic tuff and brickclay; Tansey Green 20. Coefficient of consolidation, Cv 53 Quarry 27 21. Sulphates in soil and groundwater 53 22. Summary geotechnical data forthe superficial 5. Palaeosols in the Etruria Formation; Tansey Green materials 54-55 Quarry 27 23. Summary geotechnical data for the bedrock materials 56-57 6. The Wednesbury-Coseley Fault; Patent Shaft 24. Categories of slope 63 opencast site 31 25. Summary of types and methodsof coal mining and associated problems for land use 67 7. The unconformity betweenthe Etruria Formation and 26. Index of Silurian limestone mines (from Ove Arup& overlying Halesowen Formation; Ketley Quarry 3 1 Partners, 1983) 69 8. Dolerite workingsat Hailstone Quarry, Rowley Regis 62 PREFACE

This report and the accompanying thematic geological maps result from a study, carried out between 1989 and 1992, which was commissioned by the Department of the Environment andjointly funded by the Department and the British Geological Survey. The principal aim of the study was to produce a synthesis of geological information relevant to the planning of land-use and developmentin the ‘Black Country’.

The study area includes the metropolitan boroughs of Dudley and Sandwell and parts of Wolverhampton MBC, Walsall MBC, South Staffordshire County and Bromsgrove District. The study area is covered by 14 Ordnance Survey 1: 10000 quarter sheets which comprise parts of four 150 000 geological sheets, Dudley (167), Birmingham (168), Lichfield (153) and Wolverhampton (154). Primary geological survey of the area at 1: 10 560 scale was carried out in the late 19th and early 20th centuries by officers of the Geological Survey, notably J Beete-Jukes, T H Whitehead, T Eastwood andR W Pocock. Revision geological mapping at 1: 10 000 scale of those parts of the sheets covering the exposed coalfield was carried out between 1976 and 1979 by R J 0 Hamblin (SO 99 NW, SW), M RHenson (SO 99 NE, SE, and SP 09 NW,SW) and D Wilson (SO 98 NW and part of SO 99 SE). During the present study these sheets were partially revised as a desk study with limited field checking, butwith a completefield survey to delineate areas of made ground and disturbed ground, by the following officers: B W Glover (SO 99 SW, SE), J H Powell (SO 99 NW, NE) and C N Waters (SO 98 NW, SP 09 NW). Revision geological surveyat 1: 10 000-scale was carried out for the remainder of the study area by B W Glover (SO 89 SE, 98 SE, and SP08 SW), J H Powell (SO 88 SE, 89 NE, 98 SW, andSP 08 NW)and C N Waters(SO 88 NE,98 NE, and SP 09 SW). The engineeringgeology study was carried out by A Forster, and a hydrogeological contribution was provided by S W Fletcher, E L Parry and C A Thomas (National RiversAuthority). B R Marker (Department of the Environment) contributedthe planning section. The thematic geological maps were produced by P Turner, using digital methods, at BGS Keyworth. The project leader was J H Powell, the programme managers A J Wadge and J I Chisholm, and the nominated officer for the Department of the Environment, B R Marker.

The willing cooperation of landowners, tenants and quarry companiesin allowing access to their lands and undertakings is gratefully acknowledged. We are also grateful to all the holders of data for allowingus to transfer them to the National Geosciences Information Centre, BGS, Keyworth. We are especially grateful to British Coal Technical Services and Research Executive and British Coal Opencast Executive for access to abandoned mine plans and exploration data. We acknowledge the assistance provided by the officers of the various local authorities in the Black Country area, and of many other organisations, including the Severn-Trent Water Authority, National rivers Authority and British Rail, who have readily provided information andadvice.

EXECUTIVE SUMMARY cludes the metropolitan boroughs of Dudley and Sandwell and parts of Wolverhampton MBC, Walsall MBC, theCity This study, carried out between 1989 and 1992, was com- of Binningham, South Staffordshire County and Broms- missioned by the Department of the Environment and fund- grove District. The study area of 348 km2 is mostly urban ed jointly by the Department and the British Geological but includes someagricultural land in the south and west; it Survey. Its principal aimwas to producea synthesis of includes the southern part of the South Staffordshire Coal- geological information relevantto the planning of land-use field, south of the Bentley Troughfaults. and development in that part of the West Midlands conur- The rapid growth of the Black Country was linked to the bation known as the ‘Black Country’. This report is aimed development of the Industrial Revolution in the eighteenth at those involved in planning and development. Theresults and nineteenth centuries, based on exploitation of local min- are presented in a style which, it is hoped, will meet the eral resources suchas coal, fireclay, ironstone, limestone, needs of both those with and without previous geological foundrysand and aggregates. The pressure of economic knowledge. Much of the information is provided on a se- growth made the creation of a canal and railway system es- ries of ten thematic maps, each of which concentrates on a sential in maintaining the continued growthof the area; com- specific aspect of the geology relevantto the use of land. In munications were more recently improved by the construc- addition to the information contained in the report, sources tion of urbanmotorways. The proximity of theBlack of other moredetailed data are indicated. Country to the City of Birmingham, to the east of the coal- field, ensured the rapid developmentand continuing redevel- opment of the area. However, the area is now undergoing re- The study area generation following the relative decline of heavy industry The study area (Figure 1) comprises that part of the West which is being replaced by light industry, new high technol- Midlands conurbation known as the ‘Black Country’; it in- ogy manufacturing and warehouse-typeservice industries.

10

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90

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80

70

90 00 10 20 30

Figure 1 Sketch map showing the regional setting of the study area.

1 Sources of information the resource,mineralworkings and may themselvespresent problems for land usesafter extraction has ceased. The information used in the report was acquired in two Underground mining for coal has a long history in the main ways.Firstly, geological data were acquired and com- area, but the last working pit at Baggeridge closed in 1968. piled from various sources, most notably from the databas- Limited coal resources remain in the ground, but only coal es and archives of BGS, British Coal, Local Authorities lying at shallow depth in the exposed coalfield is consid- and the NRNSevern-Trent Water Authority, and from sev- ered to be potentially exploitable. eral geotechnica€ consultants andprivate companies. These Thegroundwater resources of the areaare reviewed, data are mostly in the formof memoirs, maps, underground with particular emphasis on the importance of the Triassic mine plans, borehole, shaft and trial pit records, and site in- Sherwood Sandstone aquifer. There may be scope for in- vestigation reports. Secondly,a detailed field geological creased abstraction from this source, although high nitrate surveywas undertaken by BGSgeologists at a scale of levels may present a problemlocally. 1:10 000. This covered about 55% of the area; the remain- Otherresources are discussed in some detail. Inthe ing part, having been surveyed in the1970s, was subject to Black Country a unique concentrationof nationally impor- partial revision only. tant geological sites, close to major urban centers, has po- tential for tourism, and for educational interest. Geological Geology Sites of Special Scientific Interest (SSSI) are highlighted. The bedrock geologyof the'Black Country' area comprises Waste disposal sites are provided by areas of past and pre- a wide variety of sedimentary rocks including limestone, sent mineral extraction. Sound bedrock foundation condi- conglomerate,sandstone, siltstone, mudstone, coal, iron- tions and the soils of most use to agriculture are related to stone and claystone. These rocks were deposited in marine bedrock types. and terrestrial environments spanning the Silurian to Trias- sic periods, from about 430to 225 million years ago. Older Geological Constraints rocks are known to occur at depth. Igneous dolerite rock was intruded into the sedimentary Potentially adverse ground conditions are the main geolog- pile in late Carboniferous times, about 300 million years ical constraint for consideration in planning and develop- ago. ment. Assessment of ground conditions includes not only Insome parts of thearea the bedrock is overlain by the properties and stability of bedrock and superficial mate- poorly consolidated, superficial (drift) deposits which pre- rials, but also the changes to the subsurface brought about dominantlyconsist of till (boulder clay), silt, sandand by man, such as mining and any consequent subsidence, gravel.These deposits include the products of recent quarrying and landfill. These two aspects, the natural geo- downslope movement andriver action, and were laid down logical properties and man-made modifications,are consid- during Quaternary glacial, interglacial, and postglacial pe- ered separatelyin the report. riods. Superficial deposits locally infill deep, pre-glacial, The suitability of bedrock and superficial materials for bedrock channels. Large areas of the Black Country are foundations in the Black Country area depends mainly on covered by a layer of man-made deposits overlying both their geotechnical properties. The various parameters relat- the bedrock and superficial deposits; this comprises made ing to the behaviour of ground materials and to their reac- ground and fill materials, much of it a product of mining tion to engineering structures are reviewedin the report and heavyindustries in the area. and tables of properties based on data from a total of over The survey has resulted in a considerable improvement 7854 test or sample pointsare given. to the geological knowledge of the area. Much new detail Modification of theland surface and subsurface by has been added to the geological map and this has resulted human activities takes two forms. Firstly, excavation and in a new synthesis of the geological structure of the area, removal of material leaving voids or pits, as in mining and with a revision of the stratigraphy and history of sedimen- quarrying, and, secondly, addition of material as fill either tation. This has allowed mineral resources such as brick into former excavations or purely as constructed landfill. clay, dolerite, sand and gravel, coal, and groundwater re- Manyconstraints are placed on development by these sources to be more clearly defined and constrained. changes, and particular care must be exercisedby develop- The revised geological maps also provide a sound basis ers in the area since many of these activities were carried for development and redevelopmentof the area. out before written records werekept. Along history of shallowand deep mining for coal, ironstone, and fireclay in thearea has left a legacy of Geological Resources shafts, adits, shallow workings and backfilled opencastpits The 'Black Country' area is well endowed with mineralre- which present problems for landuse. The outlines of docu- sources and to a lesser extent groundwater; other local re- mented workings, and the approximate cropof the coals, at sources influenced by ground conditions include soils for surface or beneath drift deposits, are shown on the thematic agriculture, sound foundation conditions andsites for waste maps. Many of the early workings are poorly documented, disposal. which means that in the central, exposed coalfield, where Forplanning purposes, the mineralresources fall into mining has a longer history, unrecorded former workings twocategories, those that can be extracted by surface may occur at shallow depths in any area where a coal, or working and thosethat can be mined or recoveredat depth. mineral seam thick enough to have been considered work- In the area, the former include opencast coal, sand, gravel, able, lies near the surface. Documented shafts and adits are dolerite, brick clay, and mine stone, all of which are ex- shownon thematic maps, but responsibility forlocating ploited at present. Areas in which these resources occur are shafts at or close to these sites rests on the site owner or de- delineated on thematic maps, and the potential resources veloper. The report contains information on subsidence re- are discussed fully. Conflicting claims on land from the ex- lated to deep mining, particularly the problems posed by tractive industry, agriculture or the urban developer haveto geological faults withrespect to differential subsidence, be resolved by the planner. Any construction will sterilise and dangerous gas migration.

2 Underground limestone mining has taken place in many Map 5b. Surface mineral resources and quarrying(north); areas where the Silurian limestones are present at depth. 1:25k An intensive programme involving theinvestigation, moni- Map 6a. Underground mining (south); 1:25k toring and treatmentof mined limestonecavities is continu- Map 6b. Underground mining (north); 1:25k ing. Theproblems associated with areas undermined for Map 7. Slope steepness and selected geomorphological limestone are outlined and areas known to be affected are features; 1:50k shown on the thematic maps. Map 8. Hydrogeology;1:50k In view of the poor quality of the early historical records Map 9a. Engineering geology; superficial (drift) deposits; of colliery-based and limestone mining,all development in 1:50k these areas requires very careful geological investigations Map 9b. Engineering geology; bedrock; 1:50k to ascertain whether there is anyrisk of subsidence. Copies of this report and its maps can be obtained from Tabulated information is presented for the former quar- theBritish GeologicalSurvey, Keyworth, Nottingham ries and pits in the area, with notes onthe special problems NG12 5GG. Archival dataare held at the same address. each may present to development. The increasing use of such pits for waste disposal, and the hazard fromtoxic leachates and dangerous gases suchas LIMITATIONS methane and carbon dioxide, to which this may give rise, are highlighted. Attention is drawn to the possible presence This report has been produced by the collation and inter- of unrecorded or poorly documentedbackfilled excavations pretation of geological, geotechnical and related data from in certain parts of the area, and the need for well-planned a widevariety of sources. site investigations in such places. The special problems of The report aims to provide a general introduction to the fill as a foundation materialare also considered. geological factors relevant to land-use planning and control The constraints imposed by undergroundwater in the of development, and as background information for those area are of two types. Firstly, restrictions are placed on de- preparing desk studies on specific development proposals. velopment by the need to protect the Sherwood Sandstone The data on which it is based are not comprehensive and aquifer from pollution. Secondly, rising groundwater levels vary in quality, and this is inevitably reflected in the report. beneath parts of the City of Birmingham may cause prob- Local features and conditions may not be represented, and lems for the foundations of buildings. Both aspects are re- manyboundaries shown may be only approximate. The viewed in the report. dates of the revision geological mapping are shown in Fig- Other geological factors which were examined include ure2 and no information subsequent to thesedates has local geological structure andslope stability whichmay been taken into account. For these reasons:- give rise to problematical ground conditions and could then Thisreport provides only general indications of act as constraints to development.In addition, possible groundconditions and must not be relied upon as a risks to health from exposureto radioactive radon gas ema- source of detailed information about specific areas, or nating from subsurface materials and, on a regional scale, as a substitute for site investigations or ground surveys. earthquakes may also have some relevance to land use and Users must satisfy themselves, by seeking appropriate development. professional advice and by carrying out ground surveys Appropriate site investigation should always be carried and site investigations if necessary, that ground condi- out prior to development. tions are suitable for any particular land use or devel- opment. References, glossary, appendices and thematic maps Dataused in preparing this report and the associated maps are held by theNational Geosciences Information The report concludes with a reference list and glossary of Service of the British Geological Survey at Keyworth, and, terms used, together with appendices providing information exceptfor some confidential records, can be consulted on sources of borehole, trial pit and shaft data and a list of thereby prior arrangement. mineralindustry operators, and statutory authorities. The thematic maps which accompanythis report are as follows: NOTES Map 1. Distribution of records (boreholes,shafts and trial pits); 1:50k All National Grid references inthis report lie in the 100 km Map 2a. Bedrock geology (south); 1:25k squares SO and SP (Figure 2). The majority of Grid Refer- Map 2b. Bedrock geology (north); 1:25k ences, that is, thoselocated within square SO are given Map 3a. Distribution and thicknessof superficial (drift) de without the letter prefix; those lying within squares SP are posits(south); 1:25k preceded by the letters SP. Grid references to specific lo- Map 3b. Distribution and thicknessof superficial (drift) de calities are given to eight figures (accurate to within10 posits (north); 1:25k m); more generallocations are given to six figures. Map 4a. Distribution of Made and Worked ground(south); Each borehole or shaft registered with BGS is identified 1:25k by a four-element code (e.g. SO 98 NW 15). The first two Map 4b. Distribution of Made and Worked ground(north); elements define the 10 km square (of the National Grid) in 1:25k which the borehole issituate4 the third element defines the Map 5a. Surface mineral resources and quarrying(south); quadrant of that square,and the fourth is the accession 1:25k number of the borehole.

3

INTRODUCTION information for those preparing deskstudies on specific de- velopment proposals. The geological information contained The information in this report was obtained during a three on these maps is highly selective as it is not possible to re- year contract, commissioned by the Department of the En- produce at the reducedscales all of the information present vironment in 1989. The work was jointly funded by the on the new 1:10 000 geological standards. British Geological Survey (BGS) and the Department of Furthermore, the quality of data on someof the thematic the Environment. maps is very variable; the variability of data is covered, The report provides geological information as a back- below, under the discussion of the thematic maps. It must ground for land-use planning and development purposesin be stressed that the information provided on the thematic the Black Country area. The underlying geological frame- maps and in the report is interpretive, of variable quality, work is described with special emphasis on aspects rele- vant to potential land use such as mineral resources, past and is distributed unevenly. Consequently, the maps and and present mining and quarrying, foundation conditions report are not a substitute for on-site investigation. Fur- and groundwater. thermore, the report shouldact as a guide to other more de- The intention of the report is to provide the geological tailedsources, such as the British Geological Survey information in a form which assumesthat some readersmay archives of non-confidential boreholes and other data, in- have little geological or geotechnical background knowl- cluding, most importantly, the 1: 10 000 geological stan- edge. Hence, technical terms are kept to the minimum and a dards, and accompanying Technical Reports, and theorigi- glossary of terms is included to assist the reader. The form nal field-slips, which are the fundamental sources on which of presentation adopted is in line with the recent emphasis much of thereport is based. Attention is drawn also to placed by the Department of the Environment on producing other sources of advice, including those which should be separate applied geological maps as a way of communicat- consulted in terms of water, planning and mining interests. ing results to a wider audience than traditional reports con- It is strongly recommendedthat the maps and report should strained by a limited geological approach. be used in conjunctionwith one another. Eachmap has only a limited descriptive key; a fuller detailed description and indications of limitations on the information is con- Objectives tained in the report. The aimsof the project were twofold: 1. To produce new geological maps at 1: 10 000-scale Sources of information for that part of the area surveyed at the beginning of the century; that is, all areas except for the exposed coalfield The thematic maps and reports have been produced using areas which were surveyed in the 1970s (Figure 2). These archival information and by modern geological mapping. latter areas were partially revised as a desk study with lim- The mainsources of archivalinformation are listed in ited field checking, but with a complete field survey to de- Table 1. Previous geological work carried out by the BGS lineate areas of man-made and disturbed ground. is summarised in Table 2, and the coverage by published 2. To produce q set of thematic maps at 1:25 000 or small scale (1 inch to 1 mile and 1:50 000) geological maps 1:50 000 scales, and to collate various geological, geotech- is shown in Figure3 and Table 3. nical and other relevant informationin a report intended for Geological mapsof most of the area of the exposed coal- useprimarily by land-useplanners and developers. The field were revised in the late 1970's (Figure 3) and pub- thematic maps delimit areas andsites with specific geologi- lished at 1: 10 000-scale with accompanying open-file re- cal characteristics relevant to land-use planning and devel- ports listing selectedboreholes and shafts. These sheets opment. Each thematic map highlights a particular aspect have been further revised during the present survey to in- of the geology. cludeareas of madeground and worked ground, based The maps and report should be used, together, as a gen- mainly on subsurface information and limited field check- eral introduction to geological factors relevant to land-use ing. Exceptfor minor amendments and the addition of planning and control of development, and as background Made Ground categories, these maps are published as sec-

Table 1 Main sources of archival British Geological Survey Geological maps and memoirs, field slips information (formerly the Geological and notebooks: dating from1850's. Survey & Institute of Borehole, well and trial pit logs: Geological Sciences) locations shown on Ordnance Survey 1: 10560 maps. Historical earthquake records. Geophysical data. Engineering geological data

British Coal Abandoned mine plans. Opencast Site files

Ove Arup (DOE) Abandoned limestone mine plans

Aerial photographs Delineation of mineral workings and major new constructions; historical records.

Severn-Trent WaterLNational Details of underground water supply Rivers Authority including hydrographs and analyses. Flood Limits

Local Authorities Site investigation boreholeand trial pit data. Abandoned limestone mine plans and borehole data from remedial investigations

5 Table 2 Summary of previous MAP SERIES AREA DATE OF SURVEY Geological SurveyBGS geological mapping 1852-1898 areaCountry Black Series Old (1 inch to 1 mile) County1-1922revisionssheetswith Black1Country 19 area (6 inches to 1 mile) to Silurian 1946-1953Silurian to mile) 1 to inches (6 NationalexposedSheetsMostly1977-1978Gridthe (1:lO 000)coalfield with open file reports

Table 3 PublicationSHEET of MILEBGS 1 NUMBER INCHTO 1 150000 EDITION small-scale (1 inch to m ile) geological mapsgeological1 mile) Wolverham~ton 1929 153 S,D covering the Black Country Lichfield 154 1926 S,D Dudley 167 1939 D 1939 167 Dudley 1975 S-D (RC)

Birmingham 168 1924 S,D 1924 168 Birmingham

(RC) Reconstituted at 150000 scale without geological revision S Solidedition D Driftedition (includes solid) S-D Solid and drift edition combined ondeditions without major changes to thegeological 1:25 000-scale, covering the south and north of the area. boundaries. The accompanying Technical Reportsare pub- Each thematic map highlights a particular aspect of the ge- lished as secondeditions with additional details of the ology; they should be used in conjunction with thereport. geology of the sheet area. The remainder of the project area, comprisingthe sheets towards the south-east and 1:25 000 map number western margins of the area, for which there were no mod- Map no. and theme ScaleSouthNorth ern geological maps, were subject to full geological revi- sionincluding field survey. These sheets are published 1. Distribution of records 1:50k with the latest O.S. topographical base and are accompa- 2. Bedrock geology 1:25k2B 2A nied by Technical Reports describing the geology of the 3. Distribution and thickness sheet area. The component 1: 10 000 sheets are listed in of superficial (drift) deposits 1:25k 3A 3B Appendix 4. All the maps and reports are available from 4. Distribution of Made and BGS, Keyworth. Worked Ground 1:25k4B 4A The thematic maps at 1:25 000 and 1:50 000 scale, ac- 5. Surface mineral resources companying this report,have been compiled using the and quarrying 1:25k5B 5A 1: 10 000 geological maps and other datato produce a mod- 6. Underground mining 1:25k 6B 6A ern synthesisof the geology of the area. 7. Slope steepness and In urban areas such as the Black Country the ability to selected geomorph- updatethe geological maps is largely dependanton the ological features 1:50k borehole, shaft and trial pit data. As part of this project 8. Hydrogeology 1:50k BGS actively acquired sub-surface data from a variety of 9A. Engineering geology, sources such as local authorities, site investigation compa- superficial (drift) deposits 1:50k nies, geotechnical consultants andothers. The sites of these 9B. Engineering geology, registered records is shown on Map 1:50k 1; atthe time of publi- bedrock cation this holding for the project area was about 17 000. The cooperation of those providing data (Appendix 1) is Distribution of records (Map 1) gratefully acknowledged. Access to the geological records, including the borehole database, may be made by contact- This map shows the location of boreholes, trial pits and ing the Manager, Information Services, British Geological shafts registered in the BGSdatabase at Keyworth. The Survey,Keyworth, Nottingham NG 12 5GG (Tel: 0602- shaft records are not as complete as those held by British 363100). Appointments must be made in advance. A con- Coal, Bretby. Summary records of selected boreholes and sultation fee is usually charged. shafts for each 1: 10 000 sheet are included in the relevant The sections of thereport on groundwater were con- Technical Report for that sheet; selected details are also tributed by S W Fletcher, E L Parry and C A Thomasof the presented on the face of the map. NationalRivers Authority, and is based on their well Individual records vary from simple lithological logs to records. site investigation reports and detailed lithological descrip- tions; some of the records are held in confidence and may be consulted only after permission hs been granted by the THE THEMATIC GEOLOGICAL MAPS owner of theinformation. The original non-confidential records may be examined at BGS, Keyworth, Nottingham The results of this geological survey are presented as a se- NG 12 5GG, by prior appointment, or copies of the records ries of thematicgeological maps at various scales (see can be sent in response to postal enquiries; in either case a below).Some themes are shown on two sheets, at fee is charged.

6

BedrockUndergroundgeology2B) (Maps 2A, mining6B) (Maps6A, These maps depict the bedrock (solid) geological forma- These maps show the outline of abandoned colliery-based tions at outcrop; superficial and man-made deposits are not minesderived from knownrecords held by theMines shown.The geological sequence and approximate thick- Records Office, British Coal, Bretby. In some areas more ness of the formations is shown in the generalised vertical than one seam may have been mined, at successive levels. section. The lithology of the formations is described briefly The extent of abandoned limestone mines is shown sepa- in this report and in more detail in the relevant Technical rately; this infomation is derived partly from the records Reports for the component 1: 10 000-scale sheets. Addition- held by British Coal, and partly from the maps and.plans al structural information is givenin Figures 6 and 9. accompanying the DOE commissioned reportby Ove Arup andPartners (1983). The Index of KnownLimestone Distribution and thicknessof superficial (drift) deposits Mines is that established in the Ove Arup report. The lime- (Maps 3A, 3B) stone mine data are taken fromthat report and updatedAp- pendices. An active programme of investigation of the These maps show the distribution of the drift deposits; limestone mines is taking place. The outline of the maxi- bedrockformations are not shown separately. Detailed mumextent of underminedareas is generalisedand ap- descriptions of the drift deposits are given in this report, proximate at this scale and should not be relied upon for and in more detail in the relevant Technical Reports for site investigation purposes. the 1: 10 000-scale sheets. The boundaries of the deposits The sites of known shafts are indicated; at some locations are generally conjectural, and many of the drift deposits more than oneposition is shownfor a shaft, where theorigi- are characterised by rapid lateral and vertical variations. nal record is uncertain (two or moregrid references may be Only the drift deposit at surface is shown; it may be un- given for a particular shaft). The positions are generalised derlainby, or interdigitate with other drift deposits at from records held by British Coal, Bretby, and should only depth. be used as a guideto the density of shafts in an area. Driftthickness contours (isopachyte lines) show the Fordetailed local information about the position of thickness of drift, contoured in 5 m intervals. The contour shaftsand the delineation of abandonedcolliery-based data are based largely on borehole data and to a lesser de- mines the original surveyor’s mineplans and shaft register gree on local exposures. Consequently, where sub-surface held by British Coal, Bretby, must be consulted. For addi- data are sparse, considerableuncertainty exists as to the tional information on past mining activity and abandoned thickness of the drift deposits. mineshafts, particularly for the limestone mines, the records heldby the Building Control Officerof the relevant Distribution of Made and Worked Ground (Maps4A, Metropolitan District Borough Council (Dudley, Sandwell and Wolverhampton) should be consulted. 4B)

Made ground is shown only where the deposit is 2 m thick Slope steepness and selected geomorphological features or over. In some areas this is present as distinctive topo- graphical features which can be easily delineated; in other (Map 7) areas, such as the older parts of the exposed coalfield, the Thismap is intended to highlightareas of steepslope Made Ground has been spread out, more or less evenly, which may present a constraint to development. The slope over a wide area as a result of successive periods of rede- steepness contours are generated from the 150000-scale velopment. Where the deposit does not form a distinctive Ordnance Survey digital contour data at 10 m contour in- topographical feature, theboundaries shown on the map tervals. The slope steepness categoriesare those considered are conjectural. by most engineers to represent significant angles of slope. Most Made Ground consists of a heterogeneous mix- This map should be utilised in conjunction with the Engi- ture of excavated rock and soil, building rubble, and do- neering Geology maps (9A, 9B) whichoutline the geotech- mestic and industrial refuse. The Made Ground, therefore, nical properties of the materials and show the position of is not categorised according to its content on these maps. landslips. Where these deposits were locally identifiable in the field Selected geomorphological features are shown in order or from archival sources, such as colliery waste mounds, to highlight the principal landforms in the area, and their the nature of the deposit is indicated on the 1: 10 000- relationship to the underlying geology. scale maps. Hydrogeology (Map 8) Surface mineral resources and quarrying (Maps 5A, This map shows the outcrop of the principal aquifers in the 5B) region and their summary characteristics, aquifer protec- The surface mineral resources are shown as various cate- tion zones surrounding abstracting licensed wells, summa- gories together with the sites of the known quarries. The ry well data, and additional features of hydrogeological and latter may be open, working, or partially to wholly back- hydrological interest. Further information on the hydroge- filled (see Maps 4A, 4B). Coal is present throughout much ology of the Black Country area and abstraction rates is of the Coal Measures outcrop shown on these maps. The given in this report. approximate location of the principal coal seams at crop, and sub-cropping beneath the drift deposits, is shown in Engineering geology, superficial deposits (Map 9A) and Maps 2A and 2B. The generalised areaof near-surface coal bedrock (Map 9B) resources is shown in Figure 13 as the areas in which coal seams are predicted to come to crop or be found within These maps show the distribution of the engineering geo- 50 m of the surface; no assessment or predictionis made as logical categories of both bedrock and superficial deposits to the the quality, thickness, or extent of former mining of and summaries of their geotechnical properties. The engi- the seams in the area. neeringgeological categories are cross-referenced to the

8

Plate 1 Warren's Hall Park, Dudley.View of the Dudley Canal (lookingnorth-east) near to the entrance of the Netherton Tunnel. Cobb's EnginePit and two prominentpit mounds are relics of coalworking at Windmill End Colliery. The high ground represents thedolerite outcrops at Rowley Regis and TansleyHill. The steep slope in the vicinity of Cobb's EnginePit marks the line of the Russell's Hall Fault. bedrockformations and superficial deposits shown on the1940's. However, new light manufacturingindustry Maps 2A, 2B, 3A, and 3B, respectively. Areas of landslip and service industries are replacing many of the traditional are also shown. These maps should be used in conjunction industries. Deepcoal mining ceased in the 1960'~~and with Map 7 (Slope steepness). Theengineering geology many of the sites of former large steel complexes, such as mapsare intended for regional feasibility studies and Bilston and Patent Shaft (Plate 8), have been exploited for should not be used to supplant detailed site investigation opencast coal prior to reclamation and regenerationto vari- and geotechnicalstudies of a site. ous urban uses, including industrial and housing estates. Except for localised, short-term opencast coal workingsthe only extractive industries presently working in the areaare GEOGRAPHICAL BACKGROUND brick clay, dolerite (aggregate), and sand andgravel. The topography of the area reflects the underlying geol- Physical setting ogy (Figures 4, 10). The central part, which largely com- prises the coalfield, is defined to the west by the Western The study area (Figure 1) comprises part of the West Mid- Boundary Fault and to the east by both the Eastern Bound- lands conurbation - the Black Country - and a narrow ary Fault, and the Great Barr Fault. The greater part of the tract of agricultural land to the south and west; it covers an exposed coalfield is topographically higher than the sur- area of 348 km2. The area is mostly urban and includes the rounding, downfaulted areas to the east and west which are metropolitan boroughs of Dudley and Sandwell and parts underlain by Triassic sandstone. Areas of lower elevation of Wolverhampton MBC, Walsall MBC, the City of Birm- are largely confined to thevalleys of theTame, in the ingham, South Staffordshire County and Bromsgrove Dis- north-east, and the Stour in the south-west. Mostof the up- trict (Figure 3). The component 1:10 000 National Grid land area lies above the 100 m contour, with many of the Sheets are shown in Figure 3, andlisted in Appendix 4. hills rising above 200 m in elevation; the highest point is The rapid growth of the Black Country in the 18th and the Four Stones in the Clent Hills (304 m). Withinthe coal- 19th centuries was linked to the development of the Indus- field numerous faults and folds bring older rocksto the sur- trial Revolution,based on the exploitation of abundant, face as prominent hills, such as the Silurian limestones of varied local mineral resources such as coal, ironstone, fire- Wrens Nest and Castle Hill. These folds form part of a clay, brick clay, limestone, foundry sand, and aggregates. prominent north-east-trending ridgethat extends from Sed- Economic growth necessitated the construction of good gley, in thenorth-west, through the Silurian limestone communication routes, including a network of canals and ridges, to Rowley Regis (intrusive dolerite) and Frankley railways, and more lately, urban motorways. These factors Beeches in the south-east. The ridge, which represents the and the proximity of theBlack Country to theCity of main watershed of the district, and of central England, is Birmingham, to the east, ensured the continued develop- defined by the trace of the Russell's Hall Fault (Plate l), ment of the area. The major heavy industries, on which the and is largely due to the presence of hard, resistant strata prosperity of the area was based, have beenin decline since such as intrusive dolerite and Silurian limestoneon the

9 north-east side of the fault. In the south of the area, the re- appropriate__ _ intervals. The plans are based on extensive sur- sistant Clent(Breccia) Formation forms the eponymous veys of social, economic and physical characteristics and hills. The hard Kidderminster conglomerate gives rise to a trends which planningauthorities compile for their areas. series of ridge-like escarpments, at Wollaston and Stour- There are four typesof development plan: bridge, in the west, and at Warley, in the east. In general, a) Structure Plans set out strategic policies and certain key however, the Triassic Sherwood Sandstone is typified by proposalsfor counties and are prepared by theCounty gently undulating topography, suchas the well drained area Councils : these are comprised of a written statement and a between Harborne through Edgbastonto Handsworth. Gen- key diagram; tly undulating topography is also typical of the drift cov- b) Local Plans give more detailed policies, indicate pro- ered areas, typified by the low-lying region around Darlas- posals and allocate land for various uses within the strate- tonand Wednesbury, and to theeast of thecoalfield, gic framework set out in the structure plan: these are pre- between Smethwick and Handsworth. paredby district and borough councils outside the To the south-east of the ridge that forms the major wa- Metropolitan areas: local plan provisions are shown on an tershed, streams drain to the west via Smestow Brook, the Ordnance Survey base map; Stour and its tributaries to the Severn; to the east of the c) Subject Plans can be prepared to consider issues which ridge, the Tame and its tributaries the Rea and Hockley are of particular significance in an area, for instance miner- Brook, flow towards theTrent, and eventually to the North als and waste disposal plans prepared by some shire coun- Sea. Parts of these river valleys have been canalised, and ties; and together with the railways they formed the principal com- d) UnitaryDevelopment Plans which are prepared by munication routes until the rise of the urban motorways. Metropolitan Boroughs andconsist of a strategic part 1 and TheTame flows south-eastwards alonga broad valley a more specific part 2 which mirror the functions of the which was formerly subjected to flooding. In contrast the structure and local plans prepared elsewhere. streams in the west such as the Stour and Smestow Brook Most planningissues are dealt with by district authorities flow along more steeply incised channels. but some , such as minerals and waste disposal, are county matters. In the Metropolitan Authority areas there are no counties; thus the boroughs are responsible for all planning PLANNING BACKGROUND issues. TheMetropolitan Borough Councils within the study Introduction area have prepared their Unitary Development Plans, and A principal objective of this study is to present applied ge- placed them on deposit (Table 4). In some cases, the public ological information, relevant to land use and the develop- inquiry has been held. In all cases, adopted Unitary Devel- ment of land, in a form suitable to be taken account of in opment Plans should be operative by, the end of 1993. The theplanning process. Before discussing the geological remainderincludes small parts of the shire counties of characteristics of thearea it is pertinent, therefore, to Staffordshire and Hereford and Worcester where plans of briefly summarise some points about the planning process, the other types exist. the planning context in the Black Country, and the ways in which geological informationrelates to planning issues. Control of Development The second key element of the planning system is the con- The Planning System trol of development. For most types of development, the The town and country planning system was established in prospective developer must submit a planning application 1947 and remains unchanged in its essential requirement to the relevant local authority for consideration and deci- that planningpermission is requiredfor development to sion by the PlanningCommittee. The development plan proceed. The legislation is now embodied in the Town and provides an essential framework for such decisions. CountryPlanning Act, 1990, as amended by subsequent If the planning authority fails to issue a decision within a Acts. The planning system is administered by the Depart- statutory period or refusesthe application, the applicant has ment of the Environment but is operated by local planning the right of appeal to the Secretary of State for decision. authorities - the district, borough and countycouncils. Appeals may also be lodged in respect of planning condi- The process aims to regulate the development and useof tions attached to a consent granted by the local authority. land in the public interest. It is intended to facilitate much In such cases a local planning inquiry may be held before needed development whilst striking an appropriate balance an inspector appointed by the Department of the Environ- with the need to conserve and protect the environment and ment. In a very small proportionof cases which involve is- the quality of life. This is no easy task since, in these rela- sues of more than local importance, the applicationmay be tively crowded islands and particularly in extensively ur- reservedfor decision by theSecretary of Statefor the banised areas, there are many potentially competing uses Environment. for land and manyconstraints on particular uses. It isexpected that anyapplication should be accom- The main features of the system are development plans panied by sufficient information on the proposal to allow and the control of development. the planning authority to come to an informed decision. In- deed, the authority has the power to request additional in- formation on issues of importance if this has not been pro- Development Plans vided at the outset. The planning authority is also obliged Development plans are mandatory documents prepared by to seek the view of various statutory consultees, and may local authorities. Theseprovide the contextfor deciding also seek views of members of the public who are likely to planning applications and identify sites needed to meet de- be affected by the proposed development, before any deci- mands for various land uses and developments. Preparation sion is reached, andmay consult more widely. takes account of the views expressed in public consulta- Planning permissions may be issued to stated conditions tions, and plans are reviewed, and updated if necessary, at aimed at controlling the way in which the proposed devel-

10 Table 4 DevelopmentPlans

DISTRICTSTRUCTURE PLAN“OLD STYLE’ LOCALPLANS UNITARY (THAT HAVE REACHED DEVELOPMENT ADOPTION STAGE ONLY PLANSDISTRICTWIDE PLAN

BirminghamWest Midlands Country * UDP on deposit April Structure Plan 1991 (approved March 1986)

Coventry II UDP on deposit April II 1991

Dudley II UDP on deposit August 1991

Sandwell * UDP draft March 1991

Solihull * UDP on deposit1 September 1990

Walsall * UDP on deposit October 1991

Wolverhampton * UDP on deposit May 1991

Bromsgrove Herefore and Worcester Hagley and Clent Local Draft Plan March 1992 County Structure Plan Plan adopted (approved June 1990) September 1991

South Staffordshire Structure Southern Area Local Draft Plan September Staffordshire Plan (approved March 1991) Plan adopted January 1982 1991

* A number of past District local plans have been adopted. Details can be obtained from the relevantlocal authority. UDP-Unitary Development Plan opment is undertaken and to reduce any affects of the de- Groundwater resources could, for example, become con- velopment on the environment or the local population. The taminated or development of a site could cause instability local authority is responsible for enforcing suchconditions. or underground migration of gas. Geological information may be relevant, therefore, to a number of aspects of for- ward planningof land use and controlof development. Advice issuedby the Departmentof the Environment Soundinformation on such issues maybe required at In order to facilitate the smooth operation of the plan- several stages in the planning process, forinstance: ning system, the Department of the Environment issues ad- a) wide-ranginginformation of thecharactersistics of vice to local planning authorities anddevelopers in the an area requiredby: form of Circularsand Guidance Notes. Some of these, - the local planning authority for formulationof which describe the general features of the planning system planing policies and proposalsin development or relate to specific issues which are relevant in the study plans area, are listed in Table 5. - local interests when assessingdraft development plan policies Information requirements - the Departmentof the Environmentwhen considering the regional and national implications Since the system is concerned withthe use of land, the na- of such policies. ture of the ground may be important. The majority of de- b) site specific information required by: velopment proposals involve building or construction and - prospective developers, andtheir consulants, the stability of the ground may be an issue. In other cases, when selecting sites and preparing planningappli- such as the extraction of minerals, the development itself cations relates to ground material. Implementation of development - local planning authorities when deciding such and the resulting land uses may have adverse effects of the applications environment and these haveto be considered before adeci- - other interests when consideringthe implications sionis made or when drawing up planning conditions. of proposed developmentprior to any decision Suchenvironmental effects may also relate to earth re- being made orat a local planning inquiry. sources orto the nature of the ground.

11 Table 5 Selected documents giving DOE Circulars planning advice and guidance 21/87 Developmentof contaminated land 27/87 Nature Conservation 15/88 Environmental assessment 17/89 Landfillsites: development control

Planning policy guidance

1. General policy and principles (1992) 2. GreenBelts (1988) 3. Land for Housing (1988) 4. Industrial and Commercial Development and Small Firms (1988) 12. Development plans and Regional Planning Guidance( 1992) 14. Development on Unstable Land (1990)

Minerals Planning guidance

1. General considerations and the development plan system (1988) 2. Applications, permissions and conditions (1988) 3. Opencast coal mining (1988) 6. Guidelines for aggregates provision in England and Wales (1989) 7. The reclamation of mineral workings (1989)

Derelict land grant advice

1. Derelict land grant policy (1991)

(Note: all are published by HMSO)

If a developmentis likely to have significant environmental - providing housing requirements and improving the effects, the developer may be required to submit an envi- housing stockin each MetropolitanDistrict; ronmental assessment. In general terms, such assessments - providing highquality industrial sites by both re- are needed for major projects which are of more than local cycling industrial land and releasing greenfield sites;- importance;some smaller scale projects which are pro- - conserving thenatural and built environments; and posedfor particularly sensitive orvulnerable locations; - improving the environmentin the Black Countryby and, less commonly, projects with unusually complex and ‘loosening theexisting urban structure’ and enhanc- adverse environmentaleffects (DOE, 1988a). ing the physical andsocial infrastructure; Results such as those from the present study are a useful The West Midlands Regional Forum of Local Authori- source of geological information which canbe drawn upon ties picked up, and expanded upon, these themes in a con- in preparation of environmental assessments. The present sultation report on key planningissues in the region (1 991) study contains information which contributesto the first of which was a first step in preparing regional planning guid- these two levels of consideration but theresults are general ance. This report emphasisedthat serious problems of dere- andcannot be used for site specific purposes.They do, liction in the Black Country and lack of the service sector however, give a general context which is relevant to the growthenjoyed by nearbyBirmingham. Particular prob- early stages of examination of alternative sites and helps in lemswere a deficiency of modern infrastructure and of identification of the range of issues which may need spe- high quality industrial sites. It was felt, however, that the cial consideration during any specific site investigation. It area is poised to benefit from major infrastructure projects is usual for developers and their advisers to seek relevant such as the western and northern orbital motorways. Im- informationfrom a wide range of sourcesat this ‘desk proved access should assist in making the area more com- study’ stage. The present results and, more particularly, the merciallydesirable and, therefore, rejuvenate the local database on which they are founded, allow this to be done economy. In planning terms, this would mean increasing more quickly and more thoroughly for the issues covered demand for goodsites for development, part of which than is otherwise possible. mightbe realised through derelict landreclamation and urban renewal. This accent on development is necessary for economic prosperity but it could have environmental Strategic planning issues disbenefits. However, the Regional Forum also recognised Strategicplanning guidance, resulting from joint con- the great potential in the Black Country for ‘greening the sideration by the local planning authorities and the Depart- urban environment’. ment of the Environment, was issued for the West Mid- The need to promote development and redevelopmentin lands metropolitan areato give a context for preparationof the Black Country is being addressed by the local authori- UnitaryDevelopments Plans (DOE, 1988b). This empha- ties and the Black Country Development Corporation and sised the need to revitalise the subregional economy andto an Enterprise Zones has been created in Dudley. rejuvenate innercity areas, for instance, by:

12 TheGovernment White Paper ‘This Common Inheri- eral and water resources,despoiled or derelict land and tance’ (Anon, 1990) indicated the need to work towards a landscapes, and ageing landscapesin need of rehabilitation. more ‘sustainable environment’by : The present report contributes to these for the part of the - working towards the resolutionof conflict between Region studied; directly in the case of minerals and water; development and mobility pressuresand the conserv- and indirectly through information, on ground conditions, tion of what is bestin both the ruraland urban envi- which relates to both land which is currently derelictand to ronments; land which could become derelict in future. Such informa- - maintaining economic growth withoutmaking ex- tion will help to inform the debateon options and strategic cessive demands on natural resources;and choices which will aim to:- - combating pollution without jeopardising economic - securethe preservation and conservation of the growth. common and collective inheritance; The aim of planning to strike the best balance between - ensure themost effective use of built resources; these contrasting aspirations requires an adequate informa- aidselective exploitation of naturalresources; and tion base. The Regional Forum proposed surveys of the - leave a legacyof natural and built resourcesto future natural environment to identify, amongst other things, min- generations.

13 KEY ISSUES FOR WHICH a1 motorways and the Black Countrylink to these. The ini- GEOLOGICAL INFORMATION IS REQUIRED tial selection of such road lines takes in a variety of eco- nomic and social factors but also needs to take account of The following sections review briefly some of the planning ground conditions on the various alternative routes since issues in terms of the results of this study. these may have a major impact on construction costs. The groundconditions are rarely overridingin the selection process since engineering solutions to most problems can Housing, construction and infrastructure be found, but they can give some forewarning of expendi- TheRegional Forum identified that much of the Black ture implications. Country is urbanised but a significant part of the housing stock and infrastructure needs to be improved. Conversely, Derelict Land limited areas of greenfield sites which could be used for additional development havean environmental value which The government attaches high priority to the reclamation of might sometimes outweigh their use for such purposes. A derelict land, which has arisenfrom past industrial and extrac- great deal of this undeveloped land is designated as Green tive industries. To this end, derelict land grant is made avail- Belt which placesstrict limitations on the types of develop- able and is allocated by region. The target expenditure in the ment which are likely to be appropriate. West Midlands in1991192 was$36.8 million (DOE, 1991a). Deterioration of housing stock and other buildings is an A recentsurvey (DOE, 1991b)indicated that the Black inevitable ageing process butthis can be exacerbated where Country contained some 1761 hectaresof derelict land, over44 existing structures are on ground which is subjectto move- per centof which related to past mineral extraction (Table 6). ments such as mining subsidence, shrinking and swelling The whole of the present study areais within an Assisted of clays or shales, or heave due to mineralogical changes. Area.This qualifies relevant local authorities, theBlack Chemical reactivity of groundwater can also give rise to Country Development Corporation and English Industrial damage to foundations. Estates Corporations for 100 per centgrant, and other bod- Understanding of the distribution of these factors can give ies for 80 per cent grantin respect of schemes approved by prior warning of where deterioration may be most extensive the Department of the Environment. Vigorous derelict land or, in the case of mining instability, where properties may be reclamation initiatives from the local authorities and the severely damaged and land may become derelict. BlackCountry Development Corporation are underway. The selection of sites for new developmentor re-use Over 800 hectares of land were reclaimed between April needs to proceed on arational basis whether at the level ap- 1982 and March 1988 (Table 7). propriate to Local Plans and Part 2 of Unitary Develop- These initiatives includea major programme to over- ment Plans, or the selection of individual sites by prospec- come problems arising from abandoned mines in the Much tive developers. The most cost effective sites are those in Wenlock Limestone which is guided by the Black Country which the foundation conditions are good. Less expendi- Limestone Advisory Panel. About 222 million was spent ture is needed, for example, on ground treatment or reme- on this between 1983 and 1987, and a forward programme dial measures prior to construction where sound rock or of investigation, monitoring and remedial action is continu- compact granular deposits are close to the ground surface. ing. However, the Black Country also has a legacy of other Similarly the thickness of soft materials may influence the extractive sites andland contaminated by industrial pro- depth to which foundations have to be placed or the ways cesses which may require treatment (Table6). in which underground development, suchas tunnelling, are The identification of land which has been mined or quar- carried out. Applied geological information helpsin identi- ried, of tips, and of made ground and fill which may be fication of areas with good ground properties and, in more contaminated, can contributeto the preparation of registers extreme cases, the extent of minedground which could of land which is being, or has been, put to a contaminative give rise to damage if appropriate measures are not incor- use. Localauthorities are chargedwith compiling and porated into foundations and building design. maintaining registers of such land (DOE, 1991~).The in- The Regional Forum also stressed the likely benefits of formation can also help with the preparation of strategies improved road accessto the area both in terms of peripher- for reclamationof derelict land.

Table 6 Amount of derelict land Dudley Sandwell Walsall Wolverhampton justifying reclamation at 1 April, 1988, by type, in the Metropolitan CollierySpoil 170 9 58 0 Boroughs of the Black Country 20 10 47 (hectares) Other spoil heaps 45 Excavations and pits 38 19 56 0

Derelict railway land 20 52 59 25

Mining subsidence 153 77 192 12

General industrial dereliction 91 232 182 42

Other dereliction 4 71 37 40

TOTAL 521 480 594 166

Source:DOE, 1991b

14 Table 7 Amounts of derelict WolverhamptonWalsall Sandwell Dudley land reclaimed betweenApril, 1982and March 1988 in the Collieryspoil 5heaps 698 14 Metropolitan Boroughsof the Black Country (hectares) Other spoil14 heaps 38 7 9 Excavations65 & pits 32 8 13

Derelict railway18 land 3514 28

General industrial 18 55 66 dereliction 55 18 80

Mining subsidence - - 122

Other forms of dereliction 14 17 5 16

TOTAL 235 174 25 0 148

Source:DOE, 1991b.

Recentresearch (R Tymand Partners, 1987)demon- sources of the right compositions,thus the options for strated that the two commonest causes of delays and addi- quarry locations are limited. However, quarrying is a de- tional costs to derelict land reclamation schemes were the structive process which may have adverse environmental presence of unforeseen undermining or contamination by- effects such as noise and dust. Mineral Planning Authori- past industrial processes. Thus, early awareness of gener- ties attempt to guide working to the least harmful loca- alised information relevant to these topics is valuable to tions. Planning conditions are set to limit the environmen- help ensure that design of reclamation schemes takes ac- taleffects of workingand to securereclamation of count of all relevant factors. workings to appropriate after-uses. However, information The reclamation of derelict land has obvious benefits of on the mineral resources of an area, interpreted from geo- reducingor removing potential hazardsand facilitating logical mapping, is needed for the various options to be productive uses of vacant land. Such uses may be for built identified. development,thus reducing the pressure on greenfield In addition, knowledge of the resources allows informed sites, orfor amenity uses contributing to the process of decisions to be taken on whether development which might ‘greening’ the urban landscape and so to the opportunities sterilise them should be allowed. An alternative to sterilisa- for recreation and improvementsto the quality of life. tion is extraction of the mineral before the subsequent de- velopmentis commenced thus securing a double benefit Tourism and education from asite. A large part of theBlack Country is urbanised so a The Black Country has a rich industrial archaeology and major proportion of the remaining mineral resources have vernacular architecture heritage which is displayed at the alreadybeen sterilised, are in small fragmented sites BlackCountry Museum; itself areclaimed derelict site. which are unlikely to beeconomic to work,or are so The Dudley Canal Trust has developedvisitor access to the close to housing that working would not normally be ac- original canal which was used to transport stone from the ceptable.Even so, resourcesdo remain in surrounding mines beneath Castle Hill in Dudley. Nearby Dudley Zoo Green Belt land and there may be exceptions in the more takes advantage of the high ground of the Much Wenlock urbanised areas. Opencast working of coal, for example, Limestone outcrop. has been carried out on land reclamation sites (Grimshaw, In addition to these facilities, the Black Country has ten 1990), sometimes to excavate shallow mines and infill the Sites of Special Scientific Interest designated to maintain land to make it safe, for instance around the Bilston Steel- their availability for research and, in some cases, educa- worksand Patent Shaft Steelworks sites. Oldmine tips tional purposes.The best known of theseis the Wren’s may also be washed to extract fine coal particles before Nest National Nature Reserve which is a focus for many the material is landscaped or transported away for other schooland student visits, although part is fenced off in uses, such as fill. In both cases, the value of the extracted order to prevent access to dangerous mine sites. coal may help to defraythe costs of thereclamation In addition to such formally designated sites, there are works. many others of more local value which could contribute to similar purposes. This might be keptin mind when, for ex- Water resources ample, land formerly worked for minerals is reclaimed for new uses. The results of the present study drawattention to Water resources occur bothat the ground surface and with- many of the key geological features in the area. in the ground. Resources in the rivers of the Black Country are limited Minerals and much of the local supply is pipedfrom elsewhere. However, there are locally significant sources of ground- Minerals are needed by society for many purposes, for ex- water which are extracted from wells, principally within amplecoal for energy production; sand, gravel and sandstones. Groundwater accumulates in pores, cracks and crushed rock for construction; or clay forbricks, pipes and cavities in rocks over a long period of time. If depleted by tiles.Minerals can only be extracted from geological excessive extraction, it can take a very long time to be re- plenished. Equally, it may be vulnerable to pollution from Decomposition and chemical reaction within these give boreholes, mines or the ground surface. For these reasons, rise to noxious gases and chemical leachates. Fluid wastes groundwater abstraction and safeguarding of water quality are sometimes disposedof down boreholes. Allof these can are subject to strict regulation by the National Rivers Au- give rise to serious safety or pollution problems unless strict thority. Such regulations arise from legislation outside the controls are observed. Containment measures are taken to planning system but planning still has a part to play since prevent leakage from sites, especially to prevent pollution some land uses give rise to greater risks of contamination. of water resources. Whilst adequate containment measures Thus the National Rivers Authority is a statutory consultee can be carried out for a wide range of geological settings, on planningapplications. the least expensive tend to be those in fine-grained rocks Groundwater is not only vulnerable to contaminants re- with few fractures and fissures such as some clays. Again leased below the ground surface. Where permeable rocks the geological maps can give some guidanceon the parts of are present immediately beneaththe soil profile, percolating an area within which suitable sites are most likely to be rainwateror water from rivers ordrainage systems may found. carry contaminants downto the groundwater resource. Such vulnerable areas can partly be defined by consideration of Conclusion the relationships between geological materials present in an area and known water resource horizons(aquifers). In summary, the key planning issues in the study area are the rehabilitation of housing, the provisionof industrial sitesand infrastructure such as roads, reclamation of Waste Disposal derelict landand the ‘greening’ of the urbanlandscape, Although a greater emphasis is being placed on recycling, safeguarding of water resources, conservation of the natu- modern society produces large quantities of wastes. Some ral environment, provision of waste disposal facilities and, are chemically inert and can be safely used as fill, for in- where appropriate, the extraction or safeguarding of the re- stance in construction works or disusedquarries, but many maining mineralresources. others are more difficult to deal with. Most domestic and Geological information on ground conditions, landinsta- industrial wastes are disposed of in landfill sites, often in bility and water and mineral resources can help to inform abandoned quarries. any debate on meeting theseobjectives.

16 GEOLOGICAL BACKGROUND Devonian rocks which, at depth, locally form steep sided highs, (Figure 7). The area lay close to the southern margin Introduction of the Pennine Basin which includes all of the presently separate coalfields of central andnorthern England. The The geology of an area influences many fundamental natu- southernmargin of thebasin approximates to thearea ral resources as well as constraints to land use. An appreci- around the Clent and LickeyHills which formed part of the ation of the geological background thus has considerable land barrier termed the Wales-Brabant Massif. Sand, silt, importance, especially in an area of such diverse geological and mud, derived mostly from Scandinavia was deposited materials as the Black Country. The geology of the area by the southerly flowing rivers and deltas; thickly vegetat- may be considered in three tiers - bedrock, at the base, ed peaty swamps developed onthe flood-plain. Occasional- overlain by generally unconsolidatedsuperficial or drift de- ly the Pennine Basin was invaded by the sea, resulting in posits with a relatively thin further layer of man-made and the deposition of marine shales (marine bands) that can be disturbed material at the surface. In some areas the drift correlated over wideareas. and man-made deposits may be absent, or the man-made Fluctuations in the rates of subsidence, and sedimenta- deposits may directly overlie the bedrock. Thesethree parts tion, and fluctuations in worldwide (eustatic) sea-levels are are considered separatelyin the following description. reflected in the distinct cyclicity of the Coal Measures. A typical, completecycle begins with marine or brackish Bedrock geology and structure shales (such as the named marine bands) which pass up The Black Country area includes a wide variety of sedi- through lacustrine and deltaic deposits consisting of mud- mentary rocks and smaller outcrops of intrusive igneous stones, siltstones and sandstones. Colonisationof the delta- rock (dolerite) (Figure 4). The sedimentary rocks at out- top by plants during periods of relatively low subsidence crop range in age fromSilurian to Triassic, and consist pre- resultedin the formation of thickpeats underlain by dominantly of sandstone, siltstone, mudstone, conglomer- leached soils (seatearth fireclays); after burial andcom- ateand limestone, with seams of coal,ironstone and pactionunder sediments of subsequentcycles the peats fireclay (Table 8). were eventually convertedto coal, at depth. The geologicalhistory of the bedrock in the Black Coun- The delicate balance between subsidence and sedimenta- try is outlined below, together with a brief description of tion is reflected in the great variation of the thickness of the the rock units, in upward sequence, in the subsequent sec- coal seams and interseam thickness over the area. Com- tion. A simplified geological map of the area is shown in pared to theadjacent Cannock Coalfield, however, the Figure4, but for details Map 2 andthe component Black Country area, south of the Bentley Faults (Figure 9) 1: 10 000-scale sheets should be consulted. The geological experienced relatively little subsidence, which resulted in a successionis shown in the generalised vertical sections relatively thin overall sequence and the amalgamation of a (Figure 5), and geological cross-sections (Figure 6) show number of thin seams to produce thicker seams (Plate 3) the disposition of the strata across the area. The main char- such as the Staffordshire Thick Coal (9-1 1 m thick). How- acteristics of the principal bedrock formations are shownin ever, south of a line between Halesowen and Wollescote, Table 9. The nomenclature of the rock units has evolved thethickness and quality of the coalseams deteriorates over the last century, so for comparison the modern names rapidly, and the sequence consists largely of mudstone and are compared to previous nomenclaturein Table 8. fireclay, reflecting the proximity of the southern margin of the basin (Figure 7). GEOLOGICALHISTORY Duringlate Carboniferous times there was a gradual The oldest rocks, at outcrop, in the Black Country are transition to deposition in a well-drained, fluvial environ- the Silurian strata which were depositedin a warm, shallow ment manifested in the ‘red-bed’ Etruria Formation. Pre- shelf-sea between about 430410 million years ago. During dominantlyred mudstones were deposited in oxidising Llandovery times the sea lapped on to the land surface, to conditions in a flood-plain environment whichwas periodi- the east, and deposited sandstones and shales with a rich cally cut by fluvial channels in which coarse-grained sand- shellyfauna. These beds were succeeded, in Wenlock stone and conglomerate were deposited. Dolerite was in- times, by shallow water mudstones and siltstones, and this truded into the Carboniferous strata in Westphalian C times type of sedimentationcontinued throughout most of the whenthese sediments were buried at shallowdepths. It Silurian. However, at times the supply of silt and mud di- takes the form of dykes (cutting sub-vertically through the minished, and during slight falls in relative sea-level, lime- rock)and laterally transgressivebodies such as sills and stoneswere deposited. The limestones are composed of lopoliths which broadly follow pre-existing sub-horizontal abundant and variedshelly fossils and shell debris; in Wen- bedding discontinuities. Volcanic rocks were erupted, lo- lock times small patch-reefs developed, rich in corals, cal- cally, at the surface. Following a phase of uplift and ero- careous sponges and algae. Regression of the sea in late sion in late Wesphalian C time, the Halesowen Formation Silurian to early Devonian times, associated with the Cale- marks a brief return to sedimentation in alluvial and lacus- donian mountain-building episode, resulted in a change of trine environments, similar to the Coal Measures. sedimentation as streams fed sand and silt into the basin In late Carboniferous and early Permian times, uplift and during a gradual transition from a marine to a continental faulting of the highlands to the south of the Pennine Basin environment. The latter include fluvial sediments, deposit- resulted in rejuvenation of rivers which deposited sand, silt ed on the coastal plain, with some winnowed horizons rich and mud on broad alluvial plains in well-drained, oxidising in the remainsof fresh-water fish. conditions reflected in thered colour of thesediments The area was subjected to gentle folding, uplift and ero- (Keeleand Enville formations). In early Permian times, sionduring the Caledonian mountain-building episode, subsequent to the deposition of the Enville Formation, a about 380 million years ago. period of erosion occurred which was followed by deposi- Subsequent to the Caledonian earth movements, the Coal tion of coarse-grained breccia, the Clent Formation (Figure Measures were laid down in deltaic and swamp-like envi- 7). The latter was deposited as alluvial fans at the foot of ronments over the eroded, irregular floor of Silurian and an emergent mountain front, located south and west of the

17

Table 8 Present bedrock geological nomenclature comparedto the previous schemes.

GEOLOGY OF SOUTH STAFFORDSHIRE COALFIELD GEOLOGICAL SOCIETY SPECIAL REPORT BLACK COUNTRY PROJECT S (Whitehead et al., 1927) MY Triassic (Warringtonet al., 1980) AM Permian (Smith et al., 1974) PB Silesian (Ramsbottom et al., 1978) 0 Silurian (Cockset al., 1971) L - Keuper Marl Mercia Mudstone Group Mercia Mudstone Group MMG Keuper T T T R R R Lower Keuper Sandstone Bromsgrove Formation Bromsgrove Sandstone Formation BgS I Sherwood I I A A Sherwood A Upper Mottled Sandstone S SandstoneWildmoor Sandstone Formation S SandstoneWildmoor Sandstone Formation WmS S S Group S Group S Pebble Beds I Kidderminster Conglomerate I Kidderminster Formation Kdm I Bunter C 1 C C Lower Mottled Sandstone Bridgnorth Sandstone Formation Bridgnorth Sandstone Formation BnS P P E E Hopwas Breccia R Hopwas Breccia R M M I I Breccia Groul A Clent Breccia Formation A Clent Formation Cle N N C C Calcareous Enville Enville - Beds Conglomeratc Beds Group A 0 C C STEPH- R A Group A A ANIAN B L R W Bowhills Formation R f Enville Formation En 0 Upper B E B w N M Coal Keele Beds 0 S Keele Formation F 0 Keele Formation Ke I E Measures N TD N Halesowen Beds I P Halesowen Formation I Halesowen Formation Ha F A F H F [ H E S E E Etruria (Old Hill) Marl A C Old Hill Marl Formation A C EtruriaFormation R U R R { Et 0 R 0 0 U E Middle Coal Measures U { Coal Measures U 1Coal Measures CM S S S NA S - Passage Beds Red Downton Beds DEVn Ledbury Formation LbY Downton Downton Temeside Beds Temeside Temeside Shales Group TemesideShales Formation Tsh Downton Castle Sandstone 1Group Downton Castle Sandstone ______------Downton Castle Sandstone Formatior DCS S i S I Upper Ludlow Shales Whitcliffe Beds I Whitcliffe Formation wc L Ludlow Aymestry (Sedgley) Limestone Sedgley Limestone L Aymestry Limestone Formation AL Lower Ludlow Shales Lower Ludlow Shales U Elton Formation Elt U R _____----______- R Wenlock (Dudley) Limestone Dudley Limestone I Much Wenlock Limestone Formation I A MWL A Wenlock Wenlock Shales Wenlock Shales N Coalbrookdale Formation Cbd N Woolhope (Barr) Limestone Barr Limestone Barr Limestone Formation BL ...... Buildwas Formation Bw

Llandovery Upper Llandovery Sandstone Rubery Shale Rubery Formation RbY Rubery Sandstone Table 9 Principal SYSTEM FORMATION OR PRINCIPAL ECONOMIC USE bedrock geological GROUP LITHOLOGY units in the Black Countryareaand Triassic Mercia Red mudstone with Brickmaking their economic uses Mudstone thin sandstones Bromsgrove Fairly compact Formerly used as Sandstone red sandstones, building stone; good locally pebbly water supply Wildmoor Soft red Moulding sand in the Sandstone sandstones foundry industry Kidderminster Pebble beds and Building sand and Formation red sandstones andgravel

Permian Bridgnorth Red sandstone Building sand Sandstone Clent Formation Breccia, mudstone Brick clay (mudstones and sandstone in north of area)

Carboniferous* Enville Formation Keele Sandstone, Brick and tile making Formation mudstone and (mostly Etruria Fm.) Halesowen conglomerate Sandstones used Formation locally as building stone Etruria Formation

Coal Measures Sandstone, shales, Coal, fireclay and mudstone with ironstone of former coal, ironstone, economic importance and fireclay seams Intrusive igneous Dolerite Road metal

Silurian to Downton Sandstone, Sandstone (Gornal) Devonian Group siltstone and used as building mudstone stone Chiefly Aymestry Limestone formerly Limestone Limestone and worked for flux in the Much Wenlock and calcareous production of pig iron; Limestone** mudstone agricultural lime Barr Limestone (intercallated with calcareous mudstone units)

* see Table 1 1 for details ** see Table 10 for details area. The erosional phase stripped off much of the Enville Theindividual bedrock units (groups,formations and Formation, in the south of the Black Country area, so that members) are briefly described, below, in sequential order. the Clent Breccia locally rests unconformably on the Keele The nomenclatureis summarised in Table 8. Formation.Later in Permian times, downfaulting of the areas to the west of the coalfield led to the development of CAMBRIAN-ORDOVICIAN a basin in which aeolian (dune-bedded) Bridgnorth Sand- Rocks of this age do not crop out in the area, but have been stone was deposited in anarid desert environment. proved in boreholes in the Walsall area, below the Silurian A further phase of uplift and erosion resulted in an un- Rubery Formation. They comprise hard, pale grey quartzite conformity at the base of the Triassic Sherwood Sand- and by analogy with similar rocks exposed in the LickeyHills, stone Group, so that it locally overlies rocks ranging in south of the area, they are included in the Lickey Quartzite. age from the Upper Carboniferous (Keele Formation) to Permian(Bridgnorth Sandstone). The group is charac- SILURIAN AND DEVONIAN terisedby coarse-grained conglomerate, sandstone and less commonly mudstone, which were deposited in fluvial Rocks of Silurian and Devonian age are the oldest exposed and lacustrine environments, in a semi-arid climate. The strata in the area. They appear at the surface in two main characteristicred colouration is due to thepresence of areas. In the north-east, near Walsall, Silurian shales (cal- iron oxides. careous mudstone and siltstone), together with subordinate The final phase of deformation, in post-Triassic times, limestone and sandstone give rise to gently undulating to- resulted in the downfaulting of the the Triassic strata to the pography.Between Dudley and Sedgley, hard Silurian east and west of the boundary faults which define the rela- limestone interbedded with softer shales are folded to form tively uplifted block, the coalfield. three prominent hills (Dudley Castle Hill, Wren’s Nest and

CLENT LYE OLDBURY HAMSTEAD S HILLS ssw NNE

-7WALES- BRABANT MASSIF

Figure 7 Schematic diagram showing the generalised stratigraphical relationships of the Carboniferous rocksin the Black Country. Notto scale. Vertical lines indicate non-deposition or erosion of strata. MB- marine band. V- volcanic rocks. B-basaltic intrusion. Sandstones in Keele and Enville formations are shown stippled

Hurst Hill-Sedgley Beacon). Smaller outcrops are present Coalbrookdale Formation at Netherton, Lye and Wollescote. Silurian and, to a lesser Formerly termed the Wenlock Shales, this unit consists of extent, Devonianrocks underlie the CarboniferousCoal richly fossiliferous, greyish green shales with thin, nodular Measures, at depth, over mostof the area. limestone beds, ranging in thickness from 152-213m. The Llandovery Series forrnation crops out over alarge area to the east of Walsall, and in the cores of the Silurian folds at Castle Hill, Wren’s Rubery Formation Nestand Hurst Hill. TheCoalbrookdale Formation was This unit crops out in small fault-boundedinliers along the also proved below the Coal Measures in boreholes in the line of the Eastern Boundary Faultat Great Barr. It is about east of the coalfield at Sandwell, and in the south-east of 90 m thick, and consists of yellow, fine-grained, fossilifer- area between Walsall and Halesowen. ous sandstone intercalated with shaley partings and occa- Much Wenlock Limestone Formation sional fossiliferous calcareous beds. Thisformation, locally known as theDudley Limestone, Wenlock Series crops out alongthe northeastern borderof the Walsall inlier, Buildwas Formation and around the periclinal folds at Castle Hill, Wren’s Nest and Hurst Hill, and has been proved below the Coal Mea- The Buildwas Formation forms the basal unitof the Wenlock sures in numerous boreholes between Walsall and Rowley Series, and consists of about 22 m of greenish-grey shales. It Regis. In this area the formation (Table 10) is sub-divided has been proven in boreholes in the Walsall district, but does into an Upper and Lower Quarried Limestone, 10 m and 13 not crop out. m thick, respectively, separated by the Nodular Limestone (37 m thick); the latter consists of nodular, shelly limestone Barr Limestone interbeddedwith thin partings of grey-greencalcareous A narrow outcropof interbedded fossiliferous limestone and mudstone and siltstone. The Quarried limestones consist of shales, the Barr Limestone, is present north of Great Barr. hard, bioclastic limestone, rich in shelly fossils, and include The unit is about 9 m thick and was formerly worked for large, hemispheroidal masses of unbedded limestone rich in lime in quarries and shallow adits in the Walsall area. It was fossils which are interpreted as patch-reefs. The names re- also proved, at a depth of -1 35m OD in a gate road from flect the former importance of the the subdivisions to the Springfield CollieryNo. 1 shaft [958 8831, Rowley Regis. quarrying industry, and the upper and lower units were ex-

23 ~ Table 10 I LITHOSTRATIGRAPHICALDIVISIONS THICKNESS Subdivisions of the Much Wenlock SERIES I TERMS OLDTHIS REPORT Limestone in the ~ ~ Black Country LUDLOW ShaleLudlow FormationLower Elton SERIES

Passage Beds 8.6-10.4 m W Upper Quarried Limestone Member Upper Quarried Limestone E Much Wenlock N L LimestoneBeds Nodular Limestone Nodular 3 1.1-37.8 m 0 Member Formation KE LimestoneQuarried Lower Quarried Lower 12.2-16.2 m R BedsBasement Member Limestone T Coalbrookdale Formation Wenlock ShaleWenlock CoalbrookdaleFormation S ploited, down-dip, as shallow adit mines (back cover), and sandstone rich in winnowed, phosphatised fish remains. It later from shafts as deep mines. is overlain by buff, silty sandstone and shales, which pass upward to yellow-buff, commonly cross-bedded sandstone, Ludlow Series in total about 20 m thick. The lower beds are exposed at Elton Fornation Turner’s Hill and the sandstone forms a large outcrop at The Elton Formation, formerly known as the Lower Lud- Gornal where it was erroneously shown on previous maps low Shales, crops out around the Silurian inliers of Castle as part of the Coal Measures. Small outcropsare present at Hill, Wren’s Nest, Hurst Hill and to the north and east of Netherton and the Hayes. Sedgley; a small outcrop occurs at The Hayes, near Lye. It Temeside Shales Formation comprises about 152 m of greenish grey, buff-weathering shales and sandy mudstones with thin beds of limestone This unit consists of about lorn of purple mudstone and nodules, similar to the Coalbrookdale Formation. The beds siltstone withpurple and green, micaceous, fine-grained are rich in shelly fossils. sandstone; locally thin bone beds contain abundant fish re- mains. The outcrop is restricted to small inliers at Turner’s Aymestry Limestone Hill, Netherton, Lye and Wollescote, and has been proved This formation, knownlocally as the Sedgley Limestone, is in a numberof boreholes in the latter area. about 8 m thick and occurs around the southward plunging Ledbury Formation synclinal fold south of Sedgley Beacon, andfarther north at Park Hill. South of Sedgley the Aymestry Limestone forms The Ledbury Formation is the stratigraphically highest unit a broad outcrop along the axis of an anticlinal fold. Small present below the unconformable Coal Measures. It comes to outcrops are present at Turner’s Hill, Netherton and The crop in small inliers at Wollescote and Netherton and has been Hayes. It consists of about 8 m of nodular limestone with proved in boreholes to underlie the Coal Measures at Bag- greenish grey shaly calcareous mudstone. geridge, andin the Lye area. About 80mof the formation have been proved in boreholes in the Lye area where it consists of Whitelife Formation red, purple and green micaceous siltstone and sandstone. Formerly known as the Upper Ludlow Shales, this forma- CARBONIFEROUS tion crops out at Sedgley, Turner’s Hill, Lye and Saltwells, where it consists of flaggy, silty shales with limestone nod- Coal Measures ules and thin sandstone. The beds range in thickness from The Coal Measures comprise the oldest Carboniferous rocks 9-15 m, and have yieldedan abundant shelly fauna. in the area (Table1 l), and rest unconformablyon Devonian or Pridoli Series Silurian rocks (back cover). The Vanderbeckei Marine Band, which is locally present above the Stinking Coal (Figure 8) Downton Group has been used to sub-divide the Coal Measures into Lower and The beds above Ludlow strata, in this area, are termed the Middle divisions, but since the marine band cannot be traced DowntonGroup which comprises the Downton Castle over much of the coalfield, the Coal Measures are considered Sandstone, Temeside Shales and Ledbury Formation. The here, and on the thematic maps, a as single unit. DowntonGroup underlies the unconformableCoal Mea- In the Black Country the Coal Measuresrange in thickness sures over much of the northwestern and southern parts of from 94-152m the thickness diminishing gradually, but irreg- the coalfield, and is exposed in a number of small inliers ularly, from north to south. Coal seams(Table 12; Plates 2,3) (back cover). The top of the Pridoli Series coincides with comprise only a small part (13-17%) of the total thickness of the boundary between the Silurian and Devonian systems, the Coal Measures; the remainder consists of mudstone and and in this area is not well defined; it is tentatively taken at siltstone (‘shales’), fireclay, and sandstone with thin beds of a level in the upper part of the Ledbury Formation (White ironstone. The complete cycle, described above, is frequently and Lawson, 1989). not present due to variations in conditionsat the time of depo- sition. Thus, there may be considerable variation, across the Downton Castle Sandstone Formation area, in the thickness of the interseam strata, particularly the The Ludlow Bone Bed, about 0.38 mthick, is present at the sandstones.The latter generallyrepresent the deposits of base of this formation,and consists of acoarse-grained major fluvial channels and their overbank deposits; locally

24

Plate 2 Exhumed ‘pillar and stall’ workings in the Stinking Coal exposed at Dibdale Road opencast coal site prior to excavation.

.-

, Plate 3 Exposed - .- face of theThick _.. . _. I

Coalat the Dibdale I .._.. - - ...... Roadopencast coal -.),. .. ,~ . .I‘ - , .-A .-.. site. Note the ._,- .. .. -. ,.

~.. e<.. :. I., . - _, . . s . .I . .>-; , .i :.- .- collapse of 2 ._ -2...... overburden, including redened, burnt shaleinto old workings on the right.

the channel sandstones may erode all, or part, of the underly- with the underling Coal Measures is hard to define since ing coal seamresulting in a ‘washout’. the transition to redbeds is highly gradational and occurs A generalised section through the Coal Measures show- lower down the sequence in the south of the area. The top ing the principal seams of coal, ironstone and fireclay is is marked by an erosional unconformity at the base of the shown in Figure 8. Variations in the thickness of the coal Halesowen Formation (Plate 7). Uplift and subsequent ero- seams is shown in Table 12. sion at the end of Etruria Formation times resulted in great variation in the thickness of the formation in the area. Re- Etruria Formation gionally, it ranges in thickness from 61-207 m, but in areas The Etruria Formation consists of a ‘redbed’ sequence of such as Penn it is locally absent, at depth. The formation is mudstone and siltstone characterised by predominantly red the principal brick clay resourcein the area. colours but with variegations of grey, brown and yellow, together with greenish grey, coarse-grained sandstones and Halesowen Formation conglomerates,known locally as ‘espleys’ (Plates 4, 5). This formation marks a return to Coal Measures type sedi- Thin,poor quality coals are also present. Theboundary mentation. It ranges in thickness from 76-152 m, and con-

25 Figure 8 Comparative vertical NORTH-CENTRAL (WEDNESBURY) sections through the Coal (S099SE) Measures in the north-central KEY and south of the coalfield. Datum Mudstone, siltstone, fireclay (m) line is Stinking (Vanderbeckei) ETRURIA FORMATION (Et) and fine-grained sandstone Marine Band, above the \ Stinking Coal. \ ...... Majorsandstone \ rn' \ \ TWO FOOT COAL (0.5-1.0) \ 0-0 Ironstone \ Il \ BROOCH COAL (0.5-1.5) \ \ SOUfH (LYI (SO98SW

ETRURIA FORMATION (Et); diachronous boundary, Aegiranurn Marine Band not proven

TWO FOOT COAL (0.0-0.4)

Thick Coal Rock (0-35) BROOCH COAL (0.3-1.2) Maltby Marine Band not proven HERRING COAL (0.3-0.6)

Pins and Pennyearth Ironstone (0.0-2.5)

Thick Coal Rock (0-18)

FLYING REED COAL (0.7-1.8)

THICK COAL (5.5-12.0) UPPER THICK COAL (1.2-2.5)

Grains Ironstone (0.7-2.0) Gubbin Ironstone(0.0-1.2) Coal (0.0-1.2) MIDDLE THICK COAL (1.2-2.4) LOWER THICK COAL (1.2-8.0) Gubbins Ironstone, locally HEATHEN COAL (0.9-1.8) UPPER HEATHEN COAL (0.4-0.9) Four Foot Earth Fireclay(1.0) below UH

I 1.. RUBBLE COAL (LOWER HEATHEN) Top Rock Sandstone (0.5-1.8) I <:*:.: .. LOWER HEATHEN COAL (0.4-1.2) Bottom Rock Fireclay (0.8-5.0) with thin ironstone Vanderbeckei Marine Band not proven STINKING COAL; poorly developed STINKING COAL (0.5-3.3) OLD MINE CLAY (m) (1.0-2.7) 9New MineCoal Rock (0.9) New MineCoal Rock b MINE NEW COAL (1.0-3.5) .... NEW MINE COAL (up to1.0) FIRECLAY COAL 2-3 leaves (0.6-2.1) k eNEW MINE CLAY; up to 3seams (0.7-2.3) 1; : ::ins HillsRough and ..- - 0 0 0 White Ironstone ..... I.;/ I ..... BOTTOM COAL and HOLERS ..... 2-4 leaves (0.9-3.5) ..... Thin coal ..... Ball Measure Ironstone E.. BOTTOM COAL HOLERS (0.5-0.9) FIRECLAY COAL; I, I Gubbin and Balls Ironstone(1.5) NEW MINE CLAY (1.025); up to3 seams of flreclay I:\ -1 MEALY GREY (SINGING) COAL (0.0-1.2) ...... Sandstone interbedded with grey and red mottled ... .. mudstone, thin fireclays and ironstones...... F ...... 1'. F

LUDGBRIDGE CONGLOMERATE

26

Plate 4 Volcaniclastic tuff bed (dark grey) overlying purple- red mudstones and siltstones, and greenish pebbly sandstones (‘espleys’). Etruria Formation, Tansey Green Quarry (brick clay resources).

Plate 5 Purple and yellow-grey palaeosol (fossil soil) horizons and green, pebbly sandstone (left) in the Etruria Formation. Tansey Green Quarry (brick clay resources).

sists of grey-green mudstone and siltstone, and thick beds sandstones,passing upto orange-redmudstone, siltstone of yellow weathering, locally pebbly, sandstone. Thin coals and sandstone typical of the Keele Formation. At depth, in (less than 0.5 m thick) underlain by seatearth fireclays are the Hamstead area, the Halesowen Formation passes grada- present, but with the exception of workings at Baggeridge tionally and laterally into the Keele Formation (Figure 7). Pit, they are too thin to have been worked. Thin beds of Nodular (caliche) limestone beds and thin Spirorbis lime- palegrey Spirorbis limestone, deposited in fresh-water stones are also present. The Keele Formation increases in lakes, occur locally. The formation rests unconformably on thicknessfrom about 140 m in thesouth of the area, to the Etruria Formation (Figure 7). 274 m in the north. Keele Formation Enllille Formation Theboundary between the KeeleFormation and Hale- Thisformation is lithologically similar tothe underlying sowenFormation is gradational and diachronous. It is Keele Formation, butis distinguished by the presence of marked by amottled zone of purple-redmudstones and thickbeds of pebbleconglomerate, rich in limestone,

27 UN IT LITHOLOGYTable 11 UNIT ECONOMIC IMPORTANCE Carboniferous rocks present within the BlackEnville Formation Red sandstone and marls Sandstones formerly used locally for building Country and their purposes economic importance KeeleFormation Red marls and sandstones Brickmaking; sandstones formerly used locally for building purposes

HalesowenFormation Grey marls with clays Sandstones formerly used locally and sandstones for building purposes

EtruriaFormation Red and purple mark Brickmaking and pebbly sandstones

CoalMeasures Shales, claysand Former shallow and deep mining of coal, fireclay sandstones with coal, and ironstone; coal locally exploited in opencast ironstone, and fireclay mining seams dolomiteand chert clasts, and pebbly sandstones. The characterised by a speckled (mottled) appearance due tothe sandstones are generally red-brown in colour and have a presence of feldspar grains, and by large-scale cross-bed- higher proportionof quartz compared to the underlying for- ding formed during depositionof the sand as aeolian dunes. mation. The formation ranges in thickness from 61-198 m and crops out to the west of the Western Boundary Fault TRIASSIC and to the eastof the Eastern Boundary Fault. Shenvood Sandstone Group

PERMIAN The base of the Triassic Sherwood Sandstone Group is unconformable, so that it overlies rocks ranging in age Clent (Breccia) Formation from the Upper Carboniferous to Permian. The group is In the type area of the Clent Hills, this formation consists subdivided into three formations, in upward sequence, the of coarse-grained breccia set in a soft red-mauve mud- KidderminsterFormation, Wildmoor Sandstone and stone matrix; at depth the rock is stronger due to the pres- Bromsgrove Sandstone. The boundaries between the for- ence of a calcite cement. The pebble clasts predominantly mations are often difficult to trace due to the similarityof consist of sub-angularfragments of volcanicigneous the sandy lithologies. The characteristic red colouration is rocks mostly derived from older Precambrian rocks. As due to the presence of iron oxides. The Sherwood Sand- the formation is traced northwards from the Clent Hills, stone Group outcrop flanks the coalfield to the east and the proportion of breccia decreases, with a concomitant west of the boundary faults and is the best aquifer in the increase in the proportion of mudstone and thin beds of region. sandstone. Thus, in the Baggeridge area the formation is characterised by mudstone and siltstone with thin beds of Kidderminster Formation sandstone,locally with lenses of smallpebbles. The The lower part (c.20 m thick) of this formation consists of boundary with the underlying Enville Formation is diffi- well-rounded pebble conglomeratewith a weakly cemented cult to trace in the north of the area, due to the similarity sandstonematrix; the pebbles are composed of hard of the non-pebbly strata. In the Clent Hills the formation quartzite, sandstone, vein quartz and, more rarely, igneous is 137 m thick; to the north around Baggeridge it is esti- rocks; where the conglomerate is locally cemented by cal- mated to be 243m thick. cite it forms a hard rock. The lower conglomerate-dominat- edpart of theformation passes gradationally up to red Bridgnorth Sandstone sandstone with thin beds and lenses of conglomerate, in The Bridgnorth Sandstone is up to 60 m thick and is re- total about 60 m thick. The formation crops out along the stricted in outcrop toa narrow strip in the west of the area, flanks of the coalfield which represented a topographical adjacent to Smestow Brookand the Stour valley.It consists highduring deposition of thebasal conglomerate. The of red, fine- to medium-grained sandstone with abundant junction with the overlying Wildmoor Sandstone is grada- rounded quartz grains indicative of its aeolian origin. It is tional.

Table 12 NAME APPROXIMATE THICKNESS (in metres) Approximate thickness of the Two Foot Coal 0.22 - 0.9 1 principal seamsin the *Brooch Coal 0.30 - 1.82 South Staffordshire Flying Reed Coal (where separated from coalfield; main the Thick Coal) 0.15 - 0.45 worked seams shown *Thick Coal 5.47 - 9.14 thus: * *Upper Heathen Coal 0.61 - 1.52 .*Lower Heathen (Rubble) Coal 0.23 - 1.22 Stinking (Sulphur) Coal 0.15 - 1.82 *New Mine Coal 0.45 - 3.96 Fireclay Coals 0.45 - 2.74 *Bottom Coal (including Bottom Hollers Coal) 0.30 - 3.65 Mealy Grey Coal c.0.70

28 oa

9E

9C

8E

5

n Principal fault; tickindicates downthrow side

A Reverse fault; triangle on hangingwall side -Axial plane trace of principal anticline __jt_ Axial plane trace of principal syncline

Approximate margin of Silurian‘banks’, at depth

Scale 0 5 km

Figure 9 Generalised structural map of the Black Country showing the major faults and folds.

29 Wildmoor Sandstone Pre-Coal Measures structures This formation consists of soft, red-orange, fine- to medi- Most of the principal faults in the Black Country area prob- um-grained sandstone with occasional thin mudstone beds; ably originated as pre-Carboniferous structural lineaments, its speckled (mottled) appearance is due to the presence of which have been repeatedly reactivated during subsequent weathered feldspar grains. It forms extensive outcrops to deformationevents. Three pre-Carboniferous structural the east and west of the coalfield, and ranges in thickness grains are present, namely: north-west-trending (Charnian), from 61-152 m. The fine grain-size, small clay content and north-trending(Malvernian) and north-east-trending poor cementation made it ideal for exploitation as mould- (Caledonian). The most distinctive pre-Carboniferous de- ing sand for usein the foundry industry. formation event is the Late Caledonian phase (c. 380 mil- lionyears ago) of north-west-south-eastcompression, Bromsgrove Sandstone which resulted in the regional tilting of Silurian to Lower The Bromsgrove Sandstone crops out near Stourbridge and Devonian strata toward the north-west and the formationof Penn, to the west of the coalfield, and at Selly Oak in the north-north-west-trending folds, such as the Netherton An- south-east of the area. Red-brown sandstone, pebbly sand- ticline. A number of north-west- to north-north-east-trend- stone and pebble conglomerates with a strong calcareous ing faults were active prior to the deposition of the Coal cement are typical. The clasts include rounded quartz peb- Measures. bles and angular fragments of locally derived mudstone. In the Penn area the formation rests disconformably on the Westphalian A to C structures (Coal Measures to Etruria Wildmoor Sandstone, above which it frequently forms a Fm. times) markedescarpment such as at Tettenhall, nearWolver- During the Westphalian A to B the district was located at hampton. The Bromsgrove Sandstone was formerly quar- the southernmargin of the regionallysubsiding Pennine ried, to a limited extent, for building stone. Basin, which controlled the deposition of the Coal Mea- sures. However, deposition of the Coal Measures and over- Mercia Mudstone Group lying Etruria Formation was also influenced by synsedi- The Mercia Mudstone forms a small outcrop to the south- mentary-faulting, resulting froma phase of north-south east of the Birmingham fault, in the south-east corner of the extension.North-west- and north-east-trending basement area, near Selly Oak. It is about 150 m thick and comprises lineaments, such as the Western Boundary Fault, Russell’s a monotonous sequence of red and red-brown, calcareous Hall Fault and Dudley Port Trough, werereactivated. East- clays and mudstones with occasionalthin beds of green silt- west trending grabens, suchas the Tansey Green andBrier- stone and fine-grained sandstone, known locally as ‘sker- ley Hill Troughs, and half grabens, present in the north of ries’. The calcareous mudstone was formerly exploited for the exposed coalfield, were initiated during this phase of brick manufacture orfor agricultural purposes (marling). extensional faulting, which was accompanied volcanic ac- tivity reflected in the dolerite intrusions such as Rowley IGNEOUS INTRUSIONS AND VOLCANIC ROCKSOF Regis and BarrowHill. CARBONIFEROUS AGE Intrusive igneous rocks (dolerite) occur in association with Variscan structures (post EtruriaFm. to Clent Fm. times) the Coal Measures and Etruria Formation at several locali- During late Westphalian C to early Westphalian D times ties in the Coalfield. They crop out at Rowley Regis (Plate (post-Etruria Fm. to pre-Halesowen Fm.) the district was S), Pouk Hill (nearWalsall), Wednesfield, Barrow Hill affectedby a phase of west-north-west-east-south-east (TanseyGreen), Netherton, and Gornal Wood. Dolerite compression,which resulted in uplift and erosion of sills and dykes have also been proved, at depth, in many Carboniferous strata, prior to the deposition of the Hale- boreholes. Dolerite is an intrusive form of basalt and is a sowen Formation (Figure 7, Plate 7). These earth move- hard, dark grey, medium-grained, crystalline rock largely ments represent part of the Variscan (Hercynian) Orogeny composed of feldsparand ferromagnesian minerals. The (mountain building episode) which lasted from late West- dolerite was intruded in Westphalian C times and takesthe phalian to early Permian times. form of veins, dykes (cutting sub-vertically through the The main front of intensive mountain building move- rock)and laterally transgressivebodies such as sills and mentslay to thesouth, in SouthWales and Cornwall. saucer-shaped bodies (lopoliths) which broadly follow pre- Major structural lineaments,such as theRussell’s Hall existing sub-horizontalbedding discontinuities. Thedo- Fault, werereactivated and are typified byreverse and lerite was formerly exploited for roadstone and aggregate strike-slip components of displacement. The compression throughout the area, but there is only one remaining opera- also produced the series of north-north-west-trending peri- tional quarry, at Rowley Regis. clines of Castle Hill, Wren’s Nest and HurstHill and tight- In the Tansey Green area thedolerite intrusion at Barrow ened the pre-Carboniferous Netherton Anticline about the Hill is associated with intrusive agglomerate (composed of same north-north-east-trending foldaxis. sedimentary and igneous fragments) and extrusive airfall Following a phase of relative structural inactivity during tuffs and breccias. theWestphalian D to Stephanian (Halesowen Fm. to Enville Fm.) times the district was affected by a further STRUCTURAL GEOLOGY phase of approximately east-west compression. Thisresult- The disposition of the strata of the Black Country results ed in the regional uplift of the coalfield bounded by the from the effects of earth movements which can be distin- Western Boundary Fault (to the west) and Great Barr Fault guished as five major phases. The earth movements (phas- (to the east), with the greatest uplift occurring to the south. es of deformation and tectonic activity ) are manifested as Asa result the Permian Clent Formation rests uncon- faults and folds (Figure 9) which are described below, in formablyupon stratigraphically older rocks toward the sequential order. south of the district.

30

Plate 6 View along the exhumed Coseley- Wednesbury Fault (looking east). Note the dragof the downthrow strata (left), including two thin coal seams, against the fault. The surface of the lower seam (Two Foot) has been cleaned prior to excavation. Patent Shaft Opencast Site.

Plate 7 Halesowen Formation sandstone (yellow) unconformably overlying mudstones and sandstones of the Etruria Formation (purple-grey). Note the irregular boundary. Ketley Quarry(brick clay resource).

Permo-Triassic structures (post-Cler~tFm. to pre- block (theexposed coalfield), bounded by theWestern Shenvood Sandstone times) Boundary Fault (to the west) and Eastern Boundary Fault During the Permian, displacement on the Western Boundary (to the east),against Permo-Triassic strata (Sherwood Fault formed a topographical high to the east and a basin to Sandstone Group). A number of reverse faults of Variscan the westof the fault, withinwhich the aeolian Bridgnorth age were reactivated as normal faults, such as the Russell's Sandstone was deposited. Subsequently, a phase of uplift and Hall and Hayes faults. Since movement has occurred along erosion occurredprior to the deposition of theTriassic Kidder- many of the faults from Carboniferous to Permian times it minster Formation which rests unconformably on olderstrata. is not generally possible to determine the amount of dis- placement in post-Triassic times. Post-Triassic structures The final deformationevent comprisesa majorphase of Seismici~ east-west extensional faulting. This resulted in the juxtapo- Seismic activity, reflected in earth tremors in theBlack sition of Carboniferous strata within aN-trending horst Country, is relatively slight. Not all the historically record-

31

edtremors are related to movementalong major faults; Till and Sandy Till some of the smaller earthquake recordsare probably due to Till, also known as boulder clay, occursas broad spreads in the sudden collapse of old mine workings. Earthquakesare thenorth-east and east of the area(Figure 10) where it discussed further in the section on Geological Constraints commonly interdigitates with Glaciofluvial Sand and Grav- to Development. el and other glacial deposits. Till consists of brown or or- ange stiff clay with well-rounded to sub-angular pebbles, Superficial (drift) deposits cobbles and boulders (erratics) of various bedrock litholo- gies that havebeen incorporated into theice-sheet and Superficial (drift) deposits comprise all the sediments laid transported to its depositional site. Consequently, the errat- down during Quaternary and Recent times (the last 2 mil- ics are composed of a wide range of lithologies ranging lion years), and largely consist of the unstratified or poorly from far-travelled, exotic clasts, such as Welshigneous stratified deposits of the ice ages, interglacial periods and rocks, to those plucked or eroded from the local bedrock, postglacial times (Table 13). The deposits of the Anglian such as Sherwood Sandstone and Coal Measures. Where glaciation are mostly restricted to the north and east of the the sand contentof the matrix is high, the deposit is termed .. area, andthose of the later Devensian glaciation to the Sandy Till, but the latter is only distinguished on the map north around Wolverhampton. Locally thedrift deposits in- by a symbol since it is difficult to draw a line between the fill deep, pre-existing channels cut into the bedrock, such two types. Generally, the Till depositsare thin (less than 10 as the Moxley channel (Figure 11). The temporal relation- m) but locally the Till, intercalated with other glacial de- ships of the drift deposits are shown in Table 13 and Figure posits, reaches up to 35 m in drift-filled, bedrock channels 11, and their distribution is generalised in Figure 10 (see such as the Millfield and Moxley channels(see p.35). also Maps 3A, 3B). In the West Bromwich area Tills deposited during the The drift deposits overlie bedrock of various ages, andin Anglian glaciation, comprising an upperand lower Till, general are sub-divided on the basis of their lithology, de- separated by sand-dominatedGlaciofluvial Deposits and positional environment, landform, or a combination of all clay-dominatedGlaciolacustrine Deposits, have been de- these characteristics, often with a reference to the age of scribed (Pickering, 1957; Horton, 1974; Keen 1989). These the deposit(Table 13). The principal lithologies are till Tills are not distinguished separatelyin this report. Similar- (boulder clay), sand and gravel, silt, and clay. They were ly, the Tills of the Anglian glaciation are not distinguished, depositedenvironmentsin ranging from glacial, here, from those of the later Devensian glaciation. periglacial, and fluvial to lacustrine, during climatic peri- ods which fluctuatedfrom glacial (very cold) to interglacial Glaciofluvial Deposits (Sand and Gravel) (warm, temperate). The superficial deposits are described These deposits are less extensive than the Till (Figure 10) briefly below. The form andorigin of the steep-sided, drift- with which they are commonly associated. They consist filled bedrock channels are dealt with separately. of red-brown, fine- to medium-grained sand, and pebbly

Glaciofluvial Later BURIED Sand and Gravel Devensian Glaciofluvial Devensian Till Glaciofluvial Sand and Gravel and Glaciofluvial Sand Till CHANNEL (Outwash) Glaciofluvial (Outwash) Sandy Till Terrace and Till River Terraces I f' P

Till, Glaciolacustrine (Sheet-like) Deposits and Peatin Buried Channef

Alluvium Till

Head Glaciolacustrinesand clay, silt, and Peat

Glaciofluvial Deposits Bedrock t River Terraces etc. Figure 11 Cartoon showing therelationships of the Drift deposits in the Black Country area. Not to scale.

33 Table 13 Details PERIODEPOCH STAGE DEPOSITREFERRED TO IN TEXT ENVIRONMENT CLIMATE of the Superficial (Drift) Deposits in R Alluvium (silt, clay, sand, gravel.) Black Country E FluvialDeposits.Terrace River C warm Q E Flandrian to Peat; Lacustrine Deposits Mainly cool U MainlyN Deposits Lacustrine Peat; (clay and silt) lacustrineA silt) T and (clay T c. 10 000 yearsBP E Till in Tettenhallglacial, area Glacial, R Devensian Glaciofluvial Terrace mainly glaciofluvial N P Deposits. &cold periglacial A L ? R E Glaciofluvial Depositsmainly Periglacial Y I Interglacial Fluvial Terracecold fluvial and S Deposits withglacio-possibly T Glaciolacustrine Deposits glacio-fluvialtemper- or o Anglian phases ate lacustrine c (or E Wolstonian) Till, Glaciolacustrine & veryglacio- Glacial, N in GlaciofluvialDeposits fluvialglacio-and cold E buried channels cold to lacustrine

sand with beds and lensesof pebbly gravel. The glacioflu- patcheswith a terrace-like topography, adjacent to the vial sand and gravel was deposited by streams flowing on Stour, near Stourbridge. The deposit has yielded a varied top of, within, and at the base of the ice-sheet. Hence, the fauna of mammalian bones including mammoth, hippopo- deposits frequently occur as lenses interbedded with the tamusand wooly rhinoceros. The deposit represents the Till(Figure 11). Insome areas, around Hamstead and highest terrace of the Stour valley and was probably de- Sandwell, the deposits are subdivided on the basis of dis- positedin interglacial orimmediately post-glacial times tinctive landform into Glaciofluvial Sheet or Glaciofluvial during a phaseof rapid fluvial discharge. Terrace deposits. The Glaciofluvialsand and gravel de- posits found to the west of the coalfield, around Iverley, River Terrace Deposits Kingswinford and Wombourne are not associated withtill, This category includes the four river terraces of the Stour, and are thought to represent the productof glacial outwash the fourthbeing the topographicallyhighest and earliest streams which flowed southof the limitof the ice-front. formed; it also includes undifferentiated river terrace de- posits the age of which is not determinable. The fourth and Glaciolacustrine Deposits (sand, silt and clay) third river terraces were probably formed during, or imme- These deposits were laid down in lakes associated with the diately after, the last (Devensian) glacial phase. ice-sheet, where water was temporarily ponded. They are The terrace deposits occur at various elevations above characterised by fine grain-size and fine lamination, thelat- the present-day level of the alluvial flood-plain; they prob- ter resulting from the settling of grains through suspension ably represent the eroded remnants of formerly extensive in quiet-water conditions. Often the sand, silt and clay are alluvial plains that were sequentially deposited as the river interlaminated, reflecting fluctuations (possiblyseasonal) eroded down to its present level. The deposits consist of in thesupply of sediment.‘Rubbery’ clays occur in the yellow-brownand red-brown sand and gravel. Insome glaciolacustrine sequence around Harborne. Silt and fine- areas the individual terrace deposits are typified by a par- grained sand is associated with the deposits present in the ticular suite of pebble clasts; the fourth terrace is devoid of Moxley Channel, near Darlaston. In the latter area, and in pebbles derived from the Glaciofluvial deposits and may the Proto-Ford and Millfield channels the Glaciolacustrine predate the latter; the third terrace, however, contains abun- deposits, intercalated with Till and Glaciofluvial deposits, dantexotic igneous clasts, similar to the clasts in the reach up to 35 m thick (Maps3A and 3B). Glaciofluvial deposits. Thesecond and first terraces are At Quinton, younger Glaciolacustrine deposits are asso- considered to be post-glacial in age. ciated, at depth, with organic peat deposits (Horton, 1974; Keen, 1989); the presence of organic peats and Glaciola- Head (solifluction deposits) custrine deposits may signify an amelioration of the cli- Head is a term used for deposits derivedby the mass wast- mate typical of an interglacial phase. ing of thebedrock or superficial deposits, usually in periglacial conditions such as those subsequent to the last Glaciofluvial fan deposits ice age. When seasonally thawed, these water-saturated de- Small patches of brown sandy loam with quartz pebbles posits tend to move downslope, under gravity, over imper- and sub-angular fragmentsof the local Clent Breccia, occur meablefrozen ground (permafrost) below. Head is thus immediately west of the Western Boundary Fault in the typified by the unsorted debris of the local bedrock or drift Stourbridge-Hagley area. The deposit is less than 5m thick deposits. Since a veneer of Head or similar weathered ma- and is considered to represent the eroded remnants of allu- terial is present in most areas that were formerly glaciated, vial fans which deposited local material, derived from the the deposit is only shown where it is more than lm thick. higher groundto the west, at the foot of the scarp. Typical of the deposit is the orange-red clay (up to2 m thick) overlying the Halesowen Formation, near the Hagley Road, Interglacial terrace deposit which represents downslope movement of the Keele Forma- This deposit is about 3m thick and consists of sand, and tion mudstone. Head also occurs on the slopesof the Rowley pebbly sand with gravellenses. It forms two small, isolated Regis ridge as an admixture of clay and dolerite fragments.

34 Because it represents adownslope mass wasting deposit, Thedeposits infilling thechannels have been locally Head may contain relicshear surfaces, of importance to slope workedfor sand and gravel and brick clay. Wherethe stability and foundation design (Hutchinsonet al, 1973). channel-fill deposits overlie Coal Measures, the drift de- posits were often encounteredin mine workings; ingress of Lacustrine deposits (including peat) water at the boundary (‘sand-fault’) was a hazard to mine Small patches of lacustrine alluvium occur in areas where operations. streams have flooded broad areasof the flood plainin post- glacial times. The deposits are generally less than 5 m thick Made ground, fill and worked ground and predominantly comprise silt and clay with lenses of sand. In some areas thin beds of peat or organic clay are Human influence on the ground in the heavily urbanised present, resulting from the establishmentof swampy condi- Black Country has been substantial. Figure 12 and Maps tions on the lakeflat. 4A,4B indicate the wideextent of man-made deposits, such as Made Ground, backfill and colliery waste. Distur- Alluvium bance of the original ground surface has much wider rami- Most of the streams andrivers in the areaare flanked by al- fications,however, and includes all built-up and land- luvial floodplain deposits. The alluvium generally consists scaped areas. The constraints imposedon planning and of silt and clay overlying coarser beds of sand and gravel, development by thesedeposits are dealt with fully later although these lithologies are often found interbedded. In (p.48). Thevarious deposits and categories of disturbed places the alluvium resembles the lacustrine deposits de- groundare defined and described below. The Made scribed above, and in places the two deposits merge both Groundshown on the maps represents the deposits that laterally and vertically. The thickness of the deposit is un- were identifiable at the time of the survey. The deposits predictable because of local irregularities in the floor of were delineatedby recognition in the field and by examina- river valley. The alluvium of the Stour valley forms a tract tion of documentary sources, including aerial photographs about200 m wide, and is about 5 m thick; the alluvial and topographical maps. Made Ground covers muchof the floodplain of the Tame is up to 300 m wide and, in the urban area to some extent, but deposits can only be shown past, was was proneto flooding. onmaps of thechosen scales wherethey are over 2 m The extent and frequency of flooding has been reduced thick. Thus, only the more obvious Made Ground can be by the construction of artificial levees and canalisation of mapped by these methods andthe boundaries shown are, in the Stour and Tame; the reduced risk of flooding has en- places, conjectural. abled thealluvial floodplain to be built on inplaces. Pleistocene mass movement (landslip) Made Ground Landslipsresulting from rotational or planar shear of This category comprises areas where the ground is known bedrock and superficial (Drift) deposits are present on, or to have been deposited by man on top of the original land below,some of thesteeper slopes, notably within the surface though, in some cases, the topsoil and subsoil have Etruria Formation, below the scarp at the baseof the over- been removed first. It includes embankments, colliery spoil lying Halesowen Formation (Maps7, 9A & 9B). Landslips tips, landscaped ground, and othersignificant construction- may date from the period immediately after the last ice- al areas. In the historically older parts of the coalfield, such age(Devensian) but some are still active at thepresent asBilston, Wolverhampton and Darlaston, the original day. hummocky made ground (predominantlycolliery spoil) has been smoothed over prior to urban development. Conse- BURIEDBEDROCK CHANNELS quently the Made Ground does not form topographicalfea- The pre-glacial topography of the east and north-eastparts tures, and the extent of the deposit is, here, based largely of theBlack Country is characterised by anumber of on shallow borehole andtrial pit data. buried bedrock channels; the formof the channels is gener- Made Ground in the Black Country is a heterogeneous ally reflected in the thickness contours of the infilling drift deposit, and includes a variety of rock waste such as shale, deposits. The best defined of these are the NW-trending sandstone,and poor quality coal, anda wide variety of Moxley Channel, near Darlaston, the Proto-Tame and the man-made deposits suchas building rubble, pulverised fuel Millfield Channel,located in the WalsalVHamstead area ash(PFA), and industrial, chemicaland domestic waste. (Figure10; Maps 3A, 3B). They comprise steep sided The last two of the types listed represent a small proportion channels cut into the bedrock prior to the deposition of the of the whole, but are significant since they may produce drift deposits, and subsequently infilled with various drift hazardous toxic leachates or gases such as potentially ex- depositssuch as Till, Glaciofluvial sand and gravel, plosive methane. Glaciolacustrine deposits, and less commonly interglacial No categorisation of Made Ground type has been made deposits such as organic peat (Horton, 1974). In places the inthis study since records of thetype of depositare drift deposits infilling the channels are 35 mthick. In some sketchy and inadequate for a deposit that can vary greatly areas the present-day streams, such as the Tame and the both laterally and vertically. Individual records of a site Ford, partly follow the trendof the low ground occupiedby could give rise to spurious assumptions on the natureof the the channels. deposit as a whole, andof the safety of the site. Where the The precise sub-drift form of the channels has been the MadeGround was exposed in cuttings andexcavations subject of much debate (Pickering, 1957; Kelly, 1964; Hor- during the survey, the nature of the deposit is indicated on ton, 1974; Waters 199 lb). Borehole data collected during the component 1: 10 000-scale geological maps. thepresent survey have enabled better definition of the The most extensive areasof Made Ground are located in form of the channels. It appears that the Proto-Tame Chan- the historically oldest parts of the exposed coalfield where nel was less extensive than previously thought and is sepa- the thickermore easily minedseams, such as theThick ratedfrom the more southerly Millfield Channel by a Coal, crop out (Wednesbury, Darlaston, Willenhall, Tipton, bedrock ridge (Map 3B). Bilston). In some of these areas borehole evidence indi-

35 cates that there is a continuous smoothed spreadof colliery Whereexcavations have been used as wastedisposal spoil more than 2 m thick, and locally about 10 m thick, sites they may contain a mixture of material, the nature of overlying bedrock or drift. This is a consequence of the which is often unreliably recorded; they may contain or- haphazard, small-scale mining techniques which generated ganic and chemical wastes which can produce hazardous muchwaste material. Althoughmuch of the spoil was toxic leachatesor gases, including potentially explosive smoothed over prior to the urbanisation of the coalfield methane. The nature of the material in backfilled pits and area, the more prominentpit mounds, usually built up adja- quarries is similar to Made Ground, discussed above. How- cent to the colliery, are still evident. ever, there is the addedrisk of poor drainage in the excava- Some of the colliery mounds have been excavated for tions which may also lie close to the water-table. Further- ‘minestone’, essentially the shaley, non-coaly part of the more, toxic leachates and gases, including methane, both spoil, which is used for fill material. Areas known to have generated within the fill, may migrate through permeable been worked are Oldnall, Cradley Park and Sandwell Park strata, and/or alongfaults and joints,to emerge at some dis- collieries. tance from thesite. Sites of opencast coal extraction are a special category Worked and Made Ground (principally backjilled quarries, of backfilled excavations.At more recently excavatedsites, pits and other excavations) the nature of the fill material is carefully monitored. These This category comprisesareas where the natural ground has sites, such as Amblecote, Bilston and PatentShaft, are also been cut away and then partlyor wholly backfilled with compacted during backfilling to provide useful ground for Made Ground. The BlackCountry area is dotted with back- development. filled excavations for opencast coal, sand and gravel, sand- rock, brick clay, dolerite, limestone and marl. The types of Worked ground former quarries and pits and the special problems they pre- Worked ground includes areas where the ground is known sent to development are listed in Table 14, and are discussed to have been cut away in, for example, unfilled quarries further in the section on constraints to development. In some and pits. As noted above many of the sites of former quar- cases there isno surface indication of the pit or quarry, ries are wholly or partly backfilled, and as more urban and where the backfill is landscaped orthe area built on. The lo- industrial waste is disposedof by burial rather than inciner- cation of these sites is taken from documentary sources such ation, the pressure to use the remaining opensites becomes as archival topographical and geological maps. In general greater. However, some of the disused, unfilled pits and there is no information available on the nature of the fill ma- quarries, such as Dalton’sClay Pit [936 8701 have, by terial, although in some cases boreholes penetrating the fill virtue of their unique geological and/or biologicalfeatures, provide apartial record. Boreholes must beclosely spaced in been designated as urban parks, nature reserves or Sites of order to give atrue picture over an individual site. Special Scientific Interest (Table 16).

37 GEOLOGICALRESOURCES AND CONSTRAINTS orthe urban developer; any construction will, of course, RELEVANTTO PLANNING AND DEVELOPMENT sterilise theresource for the foreseeable future. Thework- ings themselves may present problems as to post-extraction Introduction land use, which are likelyonlyresolved to be by resorting to geotechnical or hydrogeological advice. For instance, The general geological and geographical characteristics of i’. backfilling and reinstatement is the aim, then a decision an area represent the bones on whichthe main body of land must be made as to which infilling material can be used, use planning and development decisions have to be made. bearing in mind ground conditions, to ensure the least envi- The geological framework dictates the mineral and water ronmental damage. resource potential and the suitability of foundation condi- Underground mining may involve local subsidence dam- tions in an area, including the factors which lead to insta- ageand produces waste material, thedisposal of which bility. One of the main purposes of land-use planning is to commonly creates a demand for tip sites. The area tipped ensure the best useof land in the public interest by, for ex- ample,avoiding the sterilisation of valuablemineral de- over becomes sterilised for shallow mineral extraction, and posits or high gradeagricultural land. Planners may also be presents the planner with problems regarding land use of faced with decisions regarding the suitability of land for the new artificial landforms.In addition, informationon ground conditions can be used to ensure that informed de- variouspurposes; many constraints, of varying severity, may be imposed by the underlying geology. cisions are made prior to land allocation for tipping. Whilst The following sectionidentifies and describes geological further underground mining in the Black Country is unlike- resources and constraints so that they may be placed along- ly in the near future, the legacy of old mine voids, shafts side other factors which are underconsideration by the and tips occurs extensively. planner, such as existing and proposed land use, demand The mineral resourcesof the area (Maps 5A, 5B)are de- for housing and industrial development, communications, scribed in detail in the following sections, and their distri- conservation and amenityareas, archaeological interest and bution is summarisedin Figure 13. agricultural land potential. Coal and associated fireclay and ironstone The South Staffordshire Coalfield has a total area of about Geological Resources 175 square kilometres and can conveniently be dividedin to Mineral deposits and groundwaterare the principal geolog- the ‘exposed’and ‘concealed’ coalfields (Figure 4). The ical resources, but other resources, influenced by ground former representsthat area where the coal seamsare present conditions, include soils, areas with sound bedrock founda- at or near the surface, and is delimited on its east and west tion conditions, and landsuitable for waste disposalsites. sides by the major boundaryfaults. Although inparts of this The Black Countryis well endowed with minerals, princi- area, theCoal Measures are overlain by thenon-coaly pally coal, ironstone, fireclay, brick clay, limestone, dolerite, EtruriaFormation, these areas are traditionally included sand and gravel, and water resources. To a large extent, the within the ‘exposed’ coalfield. The ‘concealed’ coalfield in- historical prosperity of the area was founded on their local cludes those areas to the east and west of the major bound- availability. Water was useful both for surface communica- ary faults where the Coal Measures are overlain by a con- tions and for industrial and domestic supply from aquifers. siderable thickness of barren Upper Carboniferousrocks. Much of the area has beenbuilt upon, but production of The principal worked seams andtheir thickness are shown opencast coal, brick clay, dolerite aggregate,gravel and in Figure 8 and Table 12. In the southern part of the coal- sand still takesplace (Harris et al., 1991).In addition, field, south of a line between Lye and Halesowen, the Coal groundwaterobtained from the Sherwood Sandstone Measures thin out below the overlying Upper Carboniferous aquifer makes an important contribution to the water sup- rocks. North of the Bentley Faults, in the Cannock Coalfield, ply of the Black Country and its environs, although do- thethick, coalesced coal seams, typical of theSouth mestic water is mostly supplied from outside of the study Staffordshire Coalfield, split into numerous thinner seams. area. Coal and associated ironstone seams have been mined in the Black Country since medieval times to supply the MINERALRESOURCES local iron industries. All the worked coals are of the bitu- For the purposeof this report mineral resources cover those minousvariety. In the northern part of thecoalfield minerals and other geological deposits which have a poten- (Wolverhampton, Tipton, Wednesbury) the seams below tial for economic exploitation. the Thick Coal such as the New Mine, Fireclay, and Bot- Mineral reserves, those quantified deposits which could tom coals, are both thicker and of a better quality than be economically extracted, are not considered here because elsewhere in the area, althoughthe Bottom Holers and many factors such as land values, extraction costs and prox- Mealy Grey coals are generally of poor quality. The Stink- imity to markets have to be considered before reserves can ing (Sulphur) Coal (Plate 2) is impure and rich in pyrite be identified; this requires comprehensive evaluation and is and was mined in only a few places. The Heathen Coal well beyond the scope of the present study. The mineral re- (locallysplit into an upper and lower seam) and the source potential of the area is almost entirely confined to Brooch Coal are of good quality, and the Two Foot Coal those materials which are presently worked e.g. opencast was worked for household coal in the northern part of the coal, dolerite aggregate, brick clay, sand and gravel, but is coalfield. The famous Thick Coal (Plate 3), up to 10 m limited by the extent of existing surface development. Other thick, was subdivided by miners into named partings, each minerals not presently extracted butof possible, though lim- withits distinctive mining and burning characteristics. ited, economic potential are also briefly discussed. North of theBentley Faults, whichseparate the South With regard to planning, mineral resources fall into two StaffordshireCoalfield from the Cannock Coalfield, the categories, those that can be extracted by surface workings Thick Coal splits into about 12 separate seams interbedded and those that can be mined or recovered at depth. In the with non-coal bearing strata. In the far south of the coal- former case, the planner may be presented withconflicting field,around Lye and Halesowen, the lowermost coal claims on the land from the extractive industry, agriculture seams fail and are replacedby fireclays.

38

Boundary of exposed coalfield (Coal Measures & Etruria Formation)

...... Outcrop of Carboniferous rocks ...... (stipple-freeside) mSilurian strata

Scale 0- 5 krn

Figure 14 Historical trends of mining reflected in the distribution of working mines. A, 1861; B, 1902; C, 1945. After Wise (1948,Figs. 56-58).

Mining methods are described in the section on Con- depth,overlain by theEtruria Formation (Brierley Hill, straints to Development: Mining Subsidence, and are sum- Netherton, Lye, Cradley, Old Hill). Dwindling production marised in Table 25 and Figure 15. The historical develop- from the olderparts of the coalfield during the later part of ment of coal mining in the Black Country is illustrated in the 19th century resulted in exploration in the concealed Figure 14. In the middle of the 19th century, the peakperi- coalfield. To the east of the Eastern Boundary (Great Barr) odof production, the exposed coalfield was dotted with fault, coal was mined from Heath Pits, Sandwell Park and many small pits, particularly in the north around Wolver- Hamstead collieries where the Thick Coal was mined at hampton,Bilston, Tipton and Wednesbury, where the depths of between 386 m and 572 m. Inthe south of the ex- Thick Coal comes to crop, and to a lesser extent to the posed coalfield, pits at Beech Tree, Oldnall, and Cradley south-west of the Russell’s Hall Fault, around Netherton. Park worked coal from shallower depths(c. 150 m), but the In 1860 the coalfield produced about 8 million tonsof coal southern margin of the coalfield was limited by the the andabout 0.75 milliontons of ironstonefrom 410 col- rapid thinning and poorquality of the seams south of a line lieries. By 1900,exhaustion of theseams and poor betweenWollescote and Halesowen. In the west of the drainage in the northern part of the coalfield, led to an ex- coalfieldmining concentrated on Himley Colliery, the pansion of the southern and south-westem areas of the ex- largest mine at the turn of the century, butafter exploration posedcoalfield where coal-bearing strata lie at greater borings in the concealed coalfield, to the west of the West-

40 Figure 15 Summary Bell- pit n of varioustypes of (sideview) mining methods (after Littlejohn, 1979 and Healy and Head, 1984)

Pillar and Stall (plan view)

pillar .

Square works (plan view)

Longwall (plan view)

coa I ‘conveyor

... stonepack A ...... (sideview) collapsed roof after support wlthdrawl coal cutter section A A

ernBoundary Fault, revealed large reserves, thefocus Bentley Faults (Wolverhampton,-Walsall area) to the Can- moved to Baggeridge Colliery which operated from 19 12 nock Coalfield, outside of the present study area. to 1968 at depths of about 520 m. Opencast mining was carried out by the early miners Between the wars most of the pits in the exposed coal- wherethe seams, particularly theThick Coal, came to field closed and in the 1950’s the only viable pits were crop. There are few records of the extent of the workings, Sandwell Park and Hamstead, to the east of the exposed but in most areas where the Thick Coal crops out it was coalfield, and Baggeridge to the west. The last deep mined workedin ‘openworkings’. Large scale, opencastopera- coal was won in 1968 when Baggeridge Colliery closed. tions have developed since 1940. Much of the area had by The focus of coal mining had by then moved north of the then been sterilised due to urban and industrial develop-

41 ment, but a numberof small sites in the northof the coal- Saltwells Wood, Brierley Hill, and near Merry Hill; clays field, northeast of Willenhall, worked the seams below abovethe Flying Reed Coal were also worked near the Thick Coal such as the Bottom, Fireclay, and New Deepfieldsand at Oak Farm. The refactory and semi- Mine coals. De-industrialisation, changes in land use and refactory clays were utilised in the manufacture of fire- redevelopment freed a numberof sites that were formerly bricks, sanitary ware, drain pipes and pottery. Pits at Et- sterilisedsuch as Amblecote railway sidings, Bilston tingshallPark Farm worked clays associated with the SteelWorks, Patent Shaft Steel Works, and Milking Bottom Coal for coarse pottery goods. Bank.These sites have mostly worked the Thick Coal Fireclay production in the Black Country declined along and/or higher seams such as the Brooch, Flying Reed and with deep coal mining inthe early part of this century, and Two Foot coals; controlled excavation and backfilling to- has now ceased. gether with remedial work on extant mine shafts has al- lowed these sites to be redeveloped subsequent to coal Dolerite (aggregate and coated stone) extraction. The chief sources of road aggregate and coated stone (tar- Since the relatively thick coal seams of the Black Coun- mac) in the area are the dolerite bodies intruded into the try lie at relatively shallow depths (generally less than 35 Carboniferous rocks (see p.30). The largest of these intru- m), the potential areafor opencast coal mining is great sions and the only one presently worked is at Rowley Regis (Figure 13). However, much of the area remains sterilised where it islocally known as the Rowley ‘rag’. Dolerite was by urban and industrial development, andin many areas the formerly worked from smallerintrusions at Pouk Hill (near shallow seams have been worked out by past mining. In Walsall), Barrow Hill, Cooper’s Bank, and to a limited ex- some areas the pillars left by the oldermining methods tent near Wolverhampton. Thelateral and vertical extent of may provide sufficient mineral to justify extraction, as at these igneous bodies is difficult to predict since they vary the Dibdale Road site (Plate 2, 3). Spontaneous combustion rapidly in thickness andmay pass over ashort distance to a of some of the shallow, thick seams has reduced them to lower or higherlevel in the rock sequence. burnt shale of no economic worth. As with most resources The Rowley Regis dolerite represents a saucer shaped the economics of extraction will depend on access restric- body (lopolith) whichis thickest in itscentral part (c. tions, proximity to local markets, the volume of extractable 100 m), wedging out rapidly towards the margins. No evi- coal, land values, the cost of remedial work, and of course dence of a vertical feeder pipe was found when the area the market value of the coal. The most promising areasare below the intrusion was largely undermined for coal. At in the central part of the exposed coalfield where the gen- Rowley Regis the dolerite is characterised by the presence tly-dipping, thick seams, particularly the Thick Coal, lie at of three distinctive joint patterns and small faults which shallow depth with little or no overburden and coal could have partly controlled the quarryingoperations. be extracted from opencast workings. Much of this area is The dolerite was formerly used to make paving blocks, covered by existing surface development, but there could andadmixed with concrete to makeconcrete slabs, but stillbe potential for extraction during development of most of the past and all of the present output is usedin the medium- to large-scale industrial sites. production of crushed aggregate or coatedstone. It is unlikely that the economics of the coal industry in Most of thequarries in the main area of production the UK will make further deep mining viable in the Black aroundRowley Regis, such as Rough Hill [962 8891, Country. Yewtree Lme [967 8691 and Bury Hill Park[977 8911, Ironstone productionceased in the early part of this have been partly or wholly backfilled (Map 5A). The work- century,although the nodular sideritic (iron carbonate) ing quarries (Appendix 2) at Hailstone and Edwin Richards seams were an important local source of supply in the 17th, ((Plate 8) [965 8841, formerly separated by a narrow road- 18th and 19thcenturies. Ironstone was generally workedin way, are about 100 m deep. conjunction with associated coals. The last workings for The potential for future exploitation of the Rowley Regis ironstone,in the 1920’s, were in the White Ironstone dolerite is limited by planning considerations suchas steril- (below the Heathen Coal) at Gornal Wood and Baggeridge isation by urban and industrial development of the area ad- Colliery. Chemical analysis of this seam gave an iron con- jacent to the existing working quarries, and geological fac- tent of 27-36% metallic iron (Whitehead et al., 1927). The tors such as thelensoid shape of the intrusion and the Gubbin Ironstones (above the Heathen Coal) were also an nature of the associated bounding faults. A programme of important source (32-39% metallic iron) and were princi- closely spaced boreholes would be required to determine pally worked at Himley and Shut Endcollieries. the precise lateral extent and thicknessof the dolerite body, Theprincipal fireclay districtextended northwards and also the thickness of any overburden (Etruria Forma- from Lye, Stourbridge and Wollescote to Shut End (Oak tion and Made Ground). Outsideof this area other planning Farm) and Gornal; in the southern part of the coalfield considerationsand the small size of the intrusions limit the main workings extended eastwards as far as Whitley their potential as a major sourceof dolerite. Colliery,near Cradley. The fireclay seams are thickest and greatest in number in the lower partof the Coal Mea- Brick Clay suressequence, and, geographically, near the southern Bricks have been manufactured from a variety of geologi- margin of the coalfield where the associated coal seams cal formations in the Black Country, but the industry was, deterioraterapidly and, in places, are replaced by and still is, mainly based on the workings in the Etruria seatearth fireclays. Below the levelof the Thick Coal, the Formation (locally termed the Etruria or Old Hill Marl). Bottom Rock Clay, Old Mine Clay and New Mine Clay Operators are listed in Appendix 2. (up to five separate seams) were of the best quality and The outcrop of the Etruria Formation generally forms longest worked. Analyses of the Old Mine Clay (White- a broad strip surrounding the Coal Measures which it over- head et al., 1927) gave 77% silica and 13% alumina, for lies. It is particularly suited to brick manufacture because thepuresest white clay. In addition, fireclays were the clays, mudstones and siltstones have a high content of worked just below the Heathen Coal. Above the level of ironoxide (Fe3+)which givesthe characteristic red theThick Coal, the Brooch Clay was worked near colouration (Holdridge, 1959). Furthermore, the heteroge-

42 neous nature of the formation which ranges from red, pur- of scattered, small pits such as those at Smethwick [SP 013 ple, yellow and green mudstone to green and yellow sand- 8921, Stone Cross [SP 009 9451 and Bustleholm [SP 015 stone, makes it possible to blend the raw material to pro- 9451, to the east of the coalfield, and at Norton [887 8221, duce high quality bricks of various colours and hues. The Kingswinford[883 8761, Compton[876 9831 andWall high iron oxidecontent facilitates theproduction of the Heath [873 9801 to the west. Only the pits at Wall Heath valuableengineering (blue) brick of greatstrength and and Stewpony [8658451 (immediately west of the area) are durability, which is producedat very high temperatures and presently active, althoughthe resource area is relatively in reducing conditions so that the ferric iron is reduced to a small. There is, however, potential for small-scale opera- ferrous state and combines with the silica to form a vitre- tions in the deposits of the Kingswinford and Norton-Ha- ous material that infills the pore spaces in the brick. The gley areas. presence of thin coaly beds, locally, within the lower part Glaciolacustrine sand was formerly worked near Moxley of the formation has theadditional advantage of increasing [971 952; 971 955; 966 9651 where its fine grain-size and the furnace temperature through combustion, thereby re- low clay content made it ideal for use as moulding sand in ducingthe amount of fuelrequired to heatthe furnace. the local foundries: most of the pits at Moxley have either Brick works in the Etruria Formation were concentrated in been wholly or partly backfilled, others are being utilised the south, south-east and south-west of the exposed coal- as nature reserves, urban parks or fishing lakes. The extent field, aroundOld Hill, Cradley,Lye, Brierley Hill and of former workings, small outcroparea, and sterilisation by Kingswinford. Present day workings are restricted to the urbandevelopment leave little resource potential inthe latter area, at Tansey Green [9128981 (Plates 4, 5), Himley Glaciofluvial sand. [897 8891, Ketley[897 8891 andBaggeridge [900 9141. Much of the resource area has beensterilised by urban and Bedrock deposits industrial development, and manyof the former pits are The soft, poorly cemented nature of the lower part of the wholly orpartly backfilled. Sherwood Sandstone Group and, to a lesser extent, the Sterilisation of much of the traditional resource, de- Bridgnorth Sandstone led to their exploitation for both scribed above, and economic pressures favouring proximi- moulding sand, and building sand and aggregate. Thiscate- ty to the market, led to exploitation of other brick clay re- gory is sometimesreferred to as ‘sand-rock’. sourcesin the area. Weathered surface clays of the The Wildmoor Sandstone was extensively worked for CoalbrookdaleFormation wereworked for brick clay moulding sand in the Compton (Wolverhampton) [88 981, near Walsall and near BeaconHill, Sedgley. However, this Amblecote [89 941, Wombourne [875 9381 and [872 9421, source is too calcareous for the manufacture of bricks un- Kingswinford [890 8871, Cot Lane [886 8771 and Stour- less the calcium carbonate has been removed by weather- bridge [90 941 areas, but production hasnow ceased. These ing. The clays of the Keele Formation are generally un- sites were favoured by their proximity to either the Stour- suitable because they are also too calcareous and have a bridge canal orthe Staffordshire and Worcestershire Canal, low iron content; they were worked together with the over- which ensured low transport costs. The only working quar- lying Glaciolacustrine clay with which they were mixed, ry (at the time of the survey) was at Wall Heath [873 9801, at California, near Harborne [SP 0368341. Glaciolacustrine where the overlying Glaciofluvial sand and gravels is also clay was also workedfor brick clay at BaggotsBridge extracted. The quarry in the Wildmoor Sandstoneat Iverley Brick Works [9718571, near Moxley. [886 8 151 is recorded as supplying silica sand for use in the Clays of the Clent Formation were worked to a limited fireclayindustry. Because the Wildmoor Sandstone is extent in the north-west of the area, near Penn [905 9951. mostly drift-covered in the east of the area, it was only ex- The Enville Formation was exploited for brick clayin the ploited for local use in scattered, small pits such as those north-east of the area at Springfield [928 9921, where it near Smethwick [021 8741 and [037 8911, and at Selly Oak was mixed with Till, and further south at [916 9731. In the [042 8291. Many of the large quarries in the Stourbridge exposed coalfield the Coal Measures (at around the level area have beenbuilt in, since they offer level, dry sites; the of the Thick Coal and New Mine Coal) and the overlying majority of those in the Compton area are unfilled, but are Till wereexploited in small pits [919 8671, [989 9951, now fringedby urban development. [961 9971 forbrick and tile clay, in theWillenhall and The demand for moulding sand sharply decreased in the Wolverhamton areas. At some of the latter sites colliery later part of this century, in line with the nationwide de- spoil tips were utilised; spoil from the Diamonds Ironstone cline in output of the iron and steel industries, and particu- workings between Willenhall and Walsall were also used larly the closure of many of the foundries in the Black in brick manufacture. Southeast of the Birmingham Fault, Country. However, the potential resource area to the west the Mercia Mudstone Group was worked in small pits of the coalfield is large. The Wildmoor Sandstone is con- [SP 026 830; SP 049 8171, but the main centre for produc- sidered to betoo fine-grained, insufficiently ‘sharp’ and tion from this source lay outside of the area, around Kings with too high a clay content for useas cement-mix sand, al- Norton. though it could be mixed with higher grade sandto produce None of the minor resources described above is currently an acceptable product. It could also be utilised as a general worked for brickclay, and the relatively poor quality of the building sand. clays, in comparisonwith the Etruria Formation, makes The lower, pebbly part of the Kidderminster Forma- their exploitation in the future unlikely. tion was formerly worked as a source of sand and gravel for aggregate. Because the pebble-rich beds are generally Sand and gravel present only in the lower part of the formation, the quarries are restricted to that part of the outcrop. Principal sites in Glacial deposits the west of the area are the scattered small pits and quarries Sandand gravel for use as aggregateand building sand along the ridge-like outcrop between Iverley [8758101 and were formerly worked fromsuperficial (drift) deposits such Ridgehill Wood [878 8841; the most extensive of these is as the Glaciofluvialsand and gravel and Glaciolacu- along The Ridge [88 841, near Wollaston, at New Wood strine sand. The former deposit was worked in a number [882 8551 andRidgehill Wood. The formation was also

43 worked for aggregate in small pits near Himley, at [891 nomic potential. The limestone was used as a flux in the 9101, [889 9371, and farther northnear Penn [886 9521, iron industry, and was calcined for agricultural lime and [888 9511. In the southof the area, small pits weqe excavat- cement lime. The close proximity of limestone, coal and ed in Hagley Park [924 8041 and south of Wychbury Hill ironstone was one of the factors that established the pre- [920 8 141. In the east of the Black Country the workings eminence of the Black Country in the iron industry. Lime- are restricted to small pits near Warley [SP 008 8591, [SP stone also occurs as thin beds in the Upper Carboniferous 001 8691 and [SP 014 8661, Hamstead [SPO46 9491 and strata as the Spirorbis limestones, but these were never of Harborne [SP 002 8421 and [SP 014 8421. any economic importance. Although the resource potential of the Kidderminster The most important limestone resource was the Much Formationfor aggregate is small, theupper non-pebbly Wenlock Limestone which was worked in the 17th, 18th, part of the formation is presently quarried for building sand 19th and 20thcenturies initially in quarries and later, as the at Highdown Quarry [879 8 151. This quarry was formerly surface resources became depleted, as shallow adit mines backfilled in part, and the fill material hadto be removed to anddeep mines (back cover). The history, development temporary store in order to exploit the sandstone at the andextent of the mining,and remedial measures to be deeper levels of the quarry. taken to reduce the risk of collapse of old workings, is con- Glaciofluvialsand and gravel was formerly extracted sidered in detail in a report commissioned by the Depart- from the upper part of the quarry, but all the present pro- ment of the Environment, and carried out by Ove Arup & ductioncomes from the sandrock. The site clearly illus- Partners: A Study of Limestone Workings in the West Mid- trates the needfor foresight in planningfor mineral re- lands, 1983. Consequently, only a summary is given here. sourcesbefore existing quarries are backfilled. It also The Much Wenlock Limestone is subdividedinto an Upper suggests that the upper non-pebbly part of the Kiddermin- QuarriedLimestone Member, about 10 m thick, and a ster Formation, where the outcrop is notsterilised by urban LowerQuarried Limestone Member, about 13 m thick, development, has significant potential for exploitation as separated by the Nodular (Limestone) Member, about 35 m building sand in the Stourbridge-Iverley area. thick (Table 10); only the upper and lower members were The Bridgnorth Sandstone was formerly worked to a worked.These last consist of strong, blue-grey, thin- to limited extent in small pits such as those near Wollaston medium-bedded, bioclastic limestone with thin partings of [880 8041, and to thenorth at Checkhill[853 8811. The grey-green shale; the intervening nodular member consists characteristic rounded grains make it unsuitable for sharp of blue-grey, thinly bedded, nodular clayey limestone, and cement-mix sand; this factor, together with its small out- calcareousmudstone. Large, irregular ovoid masses of crop area, limit its resource potential, although it could be unbedded limestone within the Lower and Nodular mem- used as a general buildingsand. bers, known locally as ‘crog balls’, represent the remains of fossil patch reefs. Their massive nature made quarrying Mine Stone (colliery waste) difficult. The limestone is cut by a set of joints which, in Large quantities of waste were produced as a by-product some areas, controlled the layoutof the mines. of underground mining in the Black Country. This materi- The mines were generally workedby similar methods to al, known as mine stone, consists of shale, mudstone, silt- the local coalmines, that is by pillar and stall methods stone, sandstone, ironstone, waste coal and seatearth. All (Figure 15) although the worked stall areas were typically of the former collieries and pits have extensive areas of largerthan in the coal mines. Where the beds dipped mine stone adjacent to their shafts. However, in the older steeply, as on the limbs of the folds at Wren’s Nest and parts of theexposed coalfield wherethere were many Castle Hill, the earliest method of working was on one hor- small working pits, such as the Tipton, Wednesbury and izontal level as elongate galleries parallel to the strike of Darlaston areas, thewaste material was spreadout, or the beds; this method generated large, unsupported voids landscaped prior to urban development in the latter part of with occasional pillars orientated at right-angles to the dip the last century and the early part of this century. Land- of the beds (back cover). The depth of mining ranged from scaping of the waste has also taken place at some of the extensions from surface quarriesto 260 m, butthe majority morerecently worked collieries (Sandwell Park, Bag- were within 20 to 70 m depth. Some of the mines were ex- geridge), either for urban redevelopment or parkland. Con- tensions from existing coal mines. An estimated 19 million sequently most of this resource is sterilised, or represents tons (7 million cubic metres)of limestone was extracted by existing foundation material. However, some of the col- quarrying and mining, the majority of it from the Much lieries in the south of the Black Country have mound-like Wenlock Limestone, between 1750 and 1900. This has re- resources of mine stone that could be utilised as fill mate- sulted in about 220 acres (0.9 km2) of quarries and over rial. These include the waste tips adjacent to Cradley Park 390 acres (1.6 km2) of abandoned mines. [936 8421, Oldnall[932 8381, WassellGrove [934 8201 The principal areas of quarrying and mining (Maps 5, 6; andOld Hawn [962 8491; otherresources are present Table 14) are generally located adjacent to the outcrops of north-west of Willenhall [956 9941. Use of mine stone is the Silurian inliers, such as Wren’s Nest, Castle Hill, and limited to some extent by its mineralogy since it may con- Hurst Hill, and the the area north-east of Walsall where the tain disseminated pyrite, which could decompose causing Silurian strata crop out. Deep mines, workedbelow the Coal foundation problems, and waste coal or carbonaceous ma- Measures, are also present in the area between Walsall, Dar- terial which can undergo combustion after burial if proper laston and Wednesbury, andin the Rowley Regisarea. precautions (such as compaction) are not taken to exclude The extent of former workings has exhausted the lime- air. stone resource at outcrop, and the deep mines are no longer economically viable. Theworkings around the inliers at Limestone Dudley, however, havepotential as attractions for scientific Limestone was formerly worked from the Silurian strata, study, tourism and recreational areas (see page 48). namely, in descending sequence, the Aymestry Limestone, Constraints on developmentposed by theabandoned the Much Wenlock (Dudley) Limestone and the Barr Lime- limestone minesare considered further in a later part of this stone, but none is regarded as having a present-day eco- report.

44 GROUNDWATERRESOURCES plex, with at least two aquifers being present in the Sher- Contributed by the National Rivers Authority woodSandstone unit. Groundwater quality isgenerally good but the upper aquifer has a tendency for highnitrates Wateris an important resource without which develop- to be present, derived mostly from agricultural application ment is impossible. The study area lies wholly in the Sev- of nitrate-based fertilisers. The lower aquifer generally has ern-Trent region of the National Rivers Authority (NRA) a low nitrate content so water of a reasonable quality can whomonitor and protect groundwater resources. The be abstracted by designing the borehole to abstract a pro- majoraquifer in the area is the Sherwood Sandstone portion of its water from the loweraquifer. Group(Map 8) whichcrops out along the western and The Birmingham aquifer unit is not utilised for public eastern margins of the coalfield. Most of the study area is, supply; the hydrogeology of this unit in relation to rising however, underlain by Carboniferous strata which are not groundwaterlevels is consideredfurther in the section considered to be a major aquifer as far as abstraction of 'Geological Constraints'. Although the SherwoodSand- water is concerned. The NRA aquifer protection policy ap- stone in the south-east of the area forms part of a major plies to both major and minoraquifers throughout the area. aquifercentered on the City of Birmingham,the area Thelocations of alllicenced groundwater abstraction -. . around SmethwicW Handsworth has witnessed a long his- boreholes and observation boreholes, which monitor long tory of industrial development which has resulted in con- term changes in the groundwater levels, are shown in Map taminated land and deterioration in the groundwater quali- 8. Specific details of the individual licences and groundwater levels are available from the National Rivers Authority,Soli- ty - hull, West Midlands. Other strata The area is drained by the Rivers Stour and Tame and There are no major public water supply boreholesin either their tributaries such as Hockley Brook. Together with an theCarboniferous strata or the Silurian and Devonian extensive canal network these waterways contributed his- strata, which together crop out over most of the central torically to watersupply, drainage (particularly mines) coalfield area. Since these strata are not consdered to be and communications (Map 8). The hydrology of the sur- major aquifers, the NRA does not monitor levels in them face water and drainageis beyond the scope of this report, andfew data are available. However,these strata have andfor further information on resources and planning yielded good local supplies of groundwater predominantly matters the reader is referred to the National Rivers Au- for industrial purposes. Borehole yields are generally poor thority. due the generally impermeable natureof the strata; the best Sherwood Sandstone Aquifer yields are derivedfrom the thicker permeablesandstone beds in the Carboniferous strata. Licenced abstraction rates The Sherwood Sandstoneaquifer, which crops out over the for the wellsin this area are shown in Map 8. eastern and western marginsof the Black Country, supplies The natural quality of the groundwater is generally poor large quantities of water to Stourbridge, Wombourne and due to the metals and sulphate and chloride minerals pre- Wolverhampton, in the west of the study area. Within the sent within the rocks. Much of the coalfield area has a long area which could be affectedby future developments in the history of heavy industry and consequently much of the western part of the study area there are six public water land is contaminated.The groundwater quality has also supply boreholes (Churchill, Hagley, Norton, Mill Mead- been affected in many places. Indeed, there have been di- ow, Coalbourne Brook, and Tack Lane) located within the rect discharges of liquid industrial wasteinto old mine boundary. However, the hydrogeological importance of the workings in parts of the area, although these practices have western outcrop should not be minimised since the aquifer now largely ceased. protection zones of a number of public supply wells, locat- The Silurian shales and limestones locally contain small ed outside of the study area, impinge on the western mar- quantities of groundwater, particularly where the old lime- gin of the area. stone mines are flooded. These old workings are progres- The outcrop of the Sherwood Sandstone Group has been sively being infilled with a rock paste forstability purposes divided into three discrete groundwater management units. (see section on Underground Limestone Workings in Geo- The western aquifer outcropis divided into the Stourbridge logical Constraints). and Wombourne units, and the eastern outcrop is represent- The rocks of the Mercia Mudstone Group represent an ed by the Birmingham unit. The groundwater resources for these units are: aquiclude confining the groundwater in the the underlying Sherwood Sandstone, in the south-east corner of the study

... AquiferAssessedLicencedActual area. The sandstone aquifer is not utilised for groundwater Unit ResourceAbstractionsUnit Abstractions in this area. The Carboniferous dolerite of which the Rowley Regis 23.95 intrusion has the largest outcrop is generally impermeable, Stourbridge 56.17 (55.39) 45.69 (45.03) although there may be some fissure flow in highly frac- Wombourne 60.68 69.14 (63.75) 51.72 (50.40) tured, jointed rock. It is not utilised for groundwater. Birmingham 34.98 40.19 ( - ) 14.89 ( - ) ADDITIONALRESOURCES (Figures are in megalitres per day; 1 megalitre = 1 million litres. Public water supplyabstractions are bracketed) Areas with sound foundation conditions Areas with good bearing capacity and foundation condi- Both units of the western aquifer are over-licenced, and the tions are an important resource, particularly in areas like Stourbridge unit is grossly over-abstracted. With the excep- theBlack Country that havebeen considerably under- tion of the Wolverhampton urban area (see later), no con- mined. Most of the bedrock materials provide sound foun- sideration would be given to new abstraction licences in ei- dation conditions, but local factors, considered in the sec- ther unit. This may pose an obstacle to development in the tionon Geological Constraints, may pose particular area. The hydrogeology of the western aquifer area is com- problems to ground stability.

45 Table 14 MINERAL GEOGRAPHICALTYPE OF PRESENTSTATE POSSLBLE Types of former DISTRIBUTIONWORKING CONSTRAINTS quarries and pits TO DEVELOPMENT in the Black Country area and Coal Central, exposed Opencast Complete Differential (opencast) coalfield pit backfill settlement. the constraints Drainage problems that they may present to andSand SmestowShallowand PartiallyStouror Drainage problems development.completely gravel Gravel valleys Brook where backfilled. pits backfilled pits Risk of migration of leachate, and pollution risk

Sand Eastern and Small to Partiallyor Waste disposal westerncompletely margins large poses pollution of area (mostlybackfilled quarries, risk to outcrop of above the underlying Shenvood Wildmoor Sst.) watertable Sst. aquifer. Porous rock surrounds quarry (risk of gas or leachate migration)

Brick South and :ut into Limited Slope failure of Clay west (mostly hillslopes backfill of steep backwall or outcrop of or deep pits many larger talus on side Etruria Fm.) pits. Small slopes. Drainage pits: partial problems of clay to complete fill in base and sides; backfill possible leachate migration in ‘espley’ sst.

Dolerite Rowley Regis Quarries Small quarries Slope failure of partially to steep backwall or completely talus on side backfilled; slopes; possible deep quarries leachate migration open or partially along joints to completely backfilled.

Silurian Dudley- to Open Small Sudden collapse of limestone Sedgley, partially quarries caverns; instability of Walsall andlarger sub- backfilled faces; leachate surface caverns migration in permeable 1st.

These include the presenceof favourable foundation conditions than therest of the Black (a) mine shafts and adits Country. Sites on the Sherwood Sandstone, despite local (b) undermined areas problems associated with running sand during the excava- (c) former excavations tion for foundations, present the most favourable sites for (d) steep slopes development. (e) running sand in foundations (f) peat deposits Waste Disposal Sites (g) poorly compacted Made Ground deposits The geology of a site considered for waste disposal is of Unexpectedfactors contributing to ground instability prime importance since the natureof the bedrock or super- may occur such as the presence of Head with relic shear ficial material, and the geological structure, such as faults planes or unconsolidated material with pockets of loose andjoints, influence the potential formigration of any sand. Preliminary site investigations should alwaysbe car- toxic or explosive substances, including gases, out of the ried outfollowing the guidelines set outin BS 5930: site and in to the atmosphere or the groundwater (Table ‘Code of Practice for Site Investigations’. Areas of known 14). The economics of exploitation of a mineral at a partic- undermining are shown on Map 6, although this may not ular site may be influenced by the potential for utilisation represent all areasundermined from colliery-basedand of the void as a landfill site (Table 15). In addition, back- limestone mines, since historical records are not complete. filling and restoration of a site may be an important factor Many of the problems associated with ground conditions in planning considerations. in these areas can be mitigated by good foundation engi- The ideal site is a large excavation in impermeable, dry neering practice. As a general rule, the area within the ex- strata which canbe backfilled with inert waste and compact- posed coalfield, and the marginal areas of the concealed ed to the former ground level, for use as open recreational coalfield,where mining has taken place, have less space, construction or agriculture. Unfavourable geological

46 Table 15 Mineralextraction MINERALVOLUME BEDROCK SPECIAL FACTORS IN andwaste disposal possibilities EXTRACTIONCREATED CHARACTER WASTE MANAGEMENT in the Black Country. Brick Clay Large Clay Brick Generally Deep excavation impermeable

Dolerite Moderate Dolerite Generally Deep excavation impermeable

Coal Small (after Limited May be deep and backfill of permeability narrow excavation spoil

Sand and Small Permeable Possible high water Gravel levels

Sand Moderate Permeable Bedrock is major (Shenvood aquifer Sandstone) sites, such as those in permeable sand andgravel, or highly drained, clayey till are present, these influence the local jointed porous bedrock, may be converted into useful sites soil and drainage conditions which, therefore, differ from by the construction of sealed cells for the waste and the thosethat might be predicted from the nature of the controlled venting of any gases such as methane and car- bedrock. bon dioxide. This is a costly operation and the best plan may be not to use these sites for waste disposal. Careful Geological sitesof scientific and educational interest consideration should be given to proposals for backfilling In a conurbation such as the Black Country, exposures of of quarries since the mineral deposit in the existing quarry rocks and their included fossils, and superficial deposits, may provide a valuable local resource in the future; re- which demonstrate the geology and geomorphology of the moval of backfill material could make extraction of the area are an important resource for education, research and mineral uneconomic. recreation. This is particularly so in the Black Country, be- Thereare few large-scale mineral extraction sites cause its scientifically important sites reflect not only the presently in operation in the Black Country;sites are limit- development of the geological sciences, but also the indus- ed to small-scale extraction of dolerite, brick clay and sand trial archaeological history of the area, which was based on and gravel (Table 15). Opencast coal excavations do not the exploitation of the mineral resources. Some sites serve generate large voids because the volume of extracted min- thedual purpose of preservingthe indigenous flora and eral is small and the waste materials generally produce a fauna as well as the geological features. The Wren's Nest larger volume than the in situ bedrock. Former sites, not site is world renowned for its exposures of Silurian strata presently backfilled, includethose worked for sand and and the limestone caverns. gravel, sand (bedrock), sandstone, dolerite and brick clay Sites can be protected by their designation as a Site of (Table 15). However,some of these sites are designated Special Scientific Interest (SSSI) or as a Regionally Im- Sites of Special Scientific Interest (SSSI), (Table 16); oth- portant Geological/Geomorphological Site (RIGS)both ers have potential for this status or for use as recreational administered by English Nature. Geological and biological areas. SSSI's in the Black Countryare listed in Table 16. The Na- In some parts of the Black Country waste material has tionalScheme for Geological Site Documentation been spread on derelict, unused or low-lying waterlogged (NSGSD), initiated in 1977 and administered by English land. These include the flood-plain of the Tame Valley Nature (then the Nature Conservancy Council), provides a [98 98 and 96961 and reclamation sites such as those near source of informationon sites forplanners, researchers, Neachells, to the east of Wolverhampton [93 991 (Maps educationalistsand others. In the Black Country this 4A, 4B). Such spreads of Made Ground over a wide area scheme is organised by volunteers from the Black Country may have the disadvantageof sterilising mineral deposits, Geological Society together with local museums such as such as smd and gravel, opencast coal or brick clay. Dudley Museum, who keep up-to-date records of the vari- ous sites. Soils p:apx-!,ys >*;7.d Cj,:v.l:!q-Jel-s :lee(:!. :-~?, be m;i;yF: rkjat" givzfi3 .. .% . -. >. Classification of the +2lit;r of a;r1cvLj&r~iia.;ir: is, In !$$Jhi;;;]jc; ;ye;i:,J:F,;\; .;:ch ii'i j;jr\~';Cq+!n~,, b;{ ":y'!j;,i :*;T:d !gab-;-

/1 ,. .>437,~ :JJ;T~Z]~ ;s.$;<-; --!-;>;.>9 ;-L-l-)T,, ~;;,;-,;~~+~.f,,vL;-,F:2.!;cx.; -d' ;$?Ll,-Li,;;{:I;i 'c.,:-sc.,I._..,. :..ALJj.-:r.:;---. .- I 1. 1,; ~!~?:\:i:r; ~i~~,;;~~~~~;,;ileLt;,.;c,;%,!<-~L,,I~ i:f ;i i:,;i,.:;cLii>.,;-' L;<,;,~',? :.,? .-,c .2'Gr....-,.; ;::x,.;; - . ... , p!; >sc L , c- we t3c; c.aiy;,;,,;7:-JiL,-,'{;-*( . ,I ~ ,. I- i%T',.:)(;;-.I, * /a. ,,,-:': '-;. ,,:, -2 :-j,::,-.;; fC-0 jjlC I* :<,,7 :,""--,, ji<<{i;,<7>+ ~c~cjlj?, ;- !ap '-I':,-; [~.,>?-;<;<;.;p;-* ;j.-;,-i ~~:~T~~y , '._ _.i?i.' , . -. il"*;%.? L_ A. fsu. II ...I ...... L ~...8- ..I. F:::x,r%;, ... . , _. -.;+.,- f;i-:kt!i-q <'...,,s:-:,.. 4 i;--;;.!;j ;<;,A,:.TT~',: ,<,{, :,:::; ).:-E ;- c,?-,.... ~ Q;? ~j',.t;~~$;,.y-~~;~'~,vl~s E,fI;:i;,,:;?. i-\,i;27>!.? is.'G[:>;2c;:;E!'i;j<-;: c;;;;;;>-rpi-,,!ie 3 I" -.- .- ~ , .. * thepoorer Grade L!. j-lnc! i.; c;.. ;:yi<; C~?;?~PC- ~;;.;~~-~c~;:-jf~y.- -;--,F-T-;f;;j Cj7'1P) ~pj.:!:~~PS.'.1L.I_.L. -(';[pi:..-,. i I , c;;;.,c;i;.e ,;;;:E,>psJ-: i:T

I_ ous strata, such as the Ei~i~~~~;;!~~7fi,~vil!z&;IC; ;~.,eple fc,r L[pi,:jj*!e ge.&p;c;..,r f:;?:i!J;,F:; \s::-:rpI' . liii L, IJ:..-i-F-~"ft'pjr:.-.L .<-L i,,r L> ic; ,c13?,ed mations(Maps 2A, 2B). Thin soils developed on the neeessay, fhe most valuabie feztales rriay bc py-eserl/ei:$ Clent Formation are suitable only for park and heathland leaving part of the quarry faceclear. with limited pastoral application. Where superficial de- Some of the sites designated RIGS in the NSGSD may posits (Maps3A, 3B), particularly 'veneers' of poody- deserve elevationto SSSI status. Sites for considerationare: Table 16 Geologicaland GeologicalSites biological Sites of Special Scientific Interest (SSSI) in the SITENAME GRID REFERENCE GEOLOGICAL INTEREST Black Countryarea. Brewin's Canal Section SO 936 876 Exposure of Coal Measures, unconformably overlying Downton Castle Sandstone (Silurian)

Bromsgrove Road Cutting SO 971 835 Exposures of Halesowen Formation sandstones

Doulton's Clay Pit SO 936 870 Exposures of Coal Measures (Westphalian A and B), including the Stinking Coal

Hay Head Quarries SP 048 987 Former workings in theBarr Limestone

Ketley Clay Pit SO 898 888 Exposures of the Halesowen Formation unconformably overlying the Etruria Formation

Turner'sHill SO9 909 18 Exposures of Ludlow rocks, Downton Group and Coal Measures

WollastonRidge Quarry SO 883 848 Kidderminster Formation unconformably overlying Bridgnorth Sandstone

Wren'sNest National SO 937920 Excellent exposures of Wenlock and Ludlow rocks, including the Much Wenlock Limestone; limestone mines

In addition, the following Geological SSSI is situated just outside of the study area:

Draw End Railway CuttingWenclock002 035rocks SK

Biological Sites

Fens Pools SO 920 866

Illey Pastures SO 977 812

(a) exposures of the Silurian strata, Downton Group and works, the early recognition of problems which may arise unconformable Coal Measures at the Hayes [9294 8449 to is of great importance, because unforeseen problems lead 9302 84461 (back cover) to additional costs and delays, and, in some cases, solu- (b) exposures of the Keele and Enville formations, andthe tionsmay be prohibitively expensive. Assessment of unconformableKidderminster Formation, along the rail- groundconditions includes not only the properties and way cutting between Halford's Lane Bridge and Watville stability of bedrock and superficial materials, but also the Road Bridge [SP 025 1 8977 to 0257 89741 and [SP 0291 changes to the subsurface brought about by man, such as 89561 miningand any consequent subsidence, quarrying and (c) quarries at Barrow Hill in the Carboniferous dolerite landfill. These two aspects, the natural geological proper- and agglomerate, andthe Etruria Formation [915 8961. ties and man-made modifications (Table 17), are consid- ered separately below.

Geological Constraints PROPERTIES AND STABILITY OF BEDROCK AND SUPERFICIAL Potentially adverse ground conditions are the main geo- MATERIALS logical constraint for consideration in planning and devel- The suitability of bedrockand superficial materials for opment.Appropriate site investigations (Anon, 198 lb) foundations depends mainly on their geotechnical proper- utilising drilling, trial pitting and soil sampling, together ties. The various parametersrelating to the bearing strength with geotechnical and geochemical testing of fill, superfi- of natural materialsand to their reaction to engineering cial and bedrock materials at a site, are important in as- structures are reviewed below. Consideration is also given sessing the suitability of a site for development or rede- to fill treated as a geologically significant deposit. Large- velopment.Although most ground problems can be scale landfill operations are a relatively recentdevelop- overcome by appropriateengineering or construction ment, made necessary by a massive increase in industrial

48 Table 17 Majorgeological MAJORCONSTRAINTS POSSIBLE RISKS constraints to development and their possible risks A NATURAL

Behaviour of ground Low bearing capacity; variable compressibility; materials swellinghhrinkage of clays; frost heave; sulphate attack on concrete; asphyxiating and explosive gases from natural sources.

Stability of natural Slope failure; landslip; solifluction (creep); and excavated slopes rockfall.

Groundwater Rising groundwater levels causing flooding of basements and swelling below foundations; contamination of groundwater aquifers. Fluctuations in groundwater may affect mine stability

B MAN-MADEB

Abandoned coal mines Explosive and asphyxiating gases (methane and carbon dioxide) emanating from abandoned mines.

Mining subsidence Crown hole development due to roof failure and (coal and limestone) general subsidence due to pillar collapse.

Quarries and Pits Low bearing capacity and variable compressibility of fill; drainage problems; explosive and asphyxiating gases in fill materials (methane and carbon dioxide), and migration of gases to surrounding areas; leachates polluting soil, groundwater and surface water; toxic residues in soil; slope failure; rockfall.

Constructional Variable compressibility of fill*; toxic and explosive gases in fill material; leachate migration; swelling; sulphate attack on concrete.

* Only if fill unsuitable, or badly compacted. and domestic waste. Fill commonly includes chemical and sulphate levels are given in Tables 19, 20, and 21, respec- organicwastes, each of which may provide difficult or, tively. No new sampling or testing was undertaken so that sometimes, hazardous conditionslocally. datapoints are, to a large extent, concentrated in areas In considering thestability of engineering structures sev- where development has taken place. Sample coverage of eral geological factors, in addition to geotechnical proper- geological units is generally good. The chemical tests (ph ties, mustbe examined. These include local geological and sulphate) quoted are those most commonly listed in structure and slope stability, and the possible presence of routine site investigations; at some sites, particularly those mining cavities. Anyof these may give rise to difficult where contaminated ground is suspected, additional tests ground conditions which can thenact as a constraint to de- for chemical and biological contamination should be car- velopment. Site specific investigations shouldalways be ried out. Full details of the coverage and quality of data, carried out prior to development. Further aspectsto be con- the methodology used in processing the data, the limita- sidered are the possibility of risks to health from exposure tions of results and analysis of geotechnical properties are to radioactive radon gas emanating from subsurface materi- provided in a separate report(Forster, 1991); simplified de- als and from methane and carbon dioxide emanating from scriptions of thegeotechnical tests andparameters are methane-bearing strata, abandoned mines or landfill sites. given in the Glossary. Lithological descriptions in this sec- On the regional scale, earthquakes may present problems tion are based on engineering geological terminology; the for some typesof development. principal lithological component is shown incapitals in ac- These factors are reviewed in detail in the following section.cordance with BS 5930: Code of Practice for Site Investi- gation. Due to the sampling limitations of the dataset some BEHAVIOUROF GROUND MATERIALS of the less common lithologies within each formation are Contributed by A Forster not represented in the summary data. Geotechnical data are The engineering geological assessment of the superficial not available for some formations with small outcropareas, and bedrock units in the area was based on information ab- such as the Rubery Formation, Barr Limestone, Aymestry stracted from published scientific papers and 559 site in- Limestone, Whitcliffe Formation and Downton Group. The vestigation reports. Data from atotal of 7854 test or sample engineering geological category of these bedrock units, as points were used. The data are summarised in Tables 22 shown on Maps 9A and 9B,is inferred from their principal and 23. Categories of compressibility, consolidationand lithological characteristics.

49

The description of geotechnical properties which follows SPT valuesmay be found down to depths of 25 m. deals with materials inthree groups: Undrainedcohesion, median value 60 kPa (firm) ranges Made Ground and fill from very soft to stiff and shows an almost random distri- Superficial (drift) deposits bution with depth. Bedrock Moisture content has a median value of 21% and shows a very wide rangein value, with values as highas 50% oc- The bedrock, superficial (drift) and Made GroundEill ma- curring at 12 m depth. The bearing capacity is commonly terials of the Black Country can be convenientlyclassified lowand is likely to varyover short distances, possibly for the purposes of land-use planning on the basis of their leading to uneven settlement. geotechnical properties (Maps 9A, 9B; Table18). Plasticity data show the material to comprise mainly in- organic clays of low, intermediate or high plasticity but a Made Ground and Fill very wide range is present with some samples in almost Made Ground and Fill are general terms for man-made de- every categoryof plasticity and grain size. posits, generally found within planned areas of landfill or Chemical tests show conditions to be neutral or slightly backfill, but including athin, locally patchy veneer beneath acidic and sulphate content to conform mainly to class 1 most urban areas of the Black Country. The distribution of conditionsfor sulphate attack onburied concrete (Anon Made Ground is shown on Maps 4A, 4B, and generalised 1981a) but someclass 2, class 3 and a fewclass 4 or 5 con- in Figure 12; the deposit is shown only where it is more ditions are indicated. Where past industrial activity has re- than2 m thick. All geotechnical investigations should sulted in contaminated ground, tests for chemical and bio- allow for the presence of made ground overlying super- logicalcontamination should be included in the site ficial (drift) deposits or bedrock. investigation. Potential hazards to people , including those The geotechnical properties of Made Ground are diffi- undertaking building or site investigation work, and possi- cult to predict. Its behaviour is dependent on its composi- ble corrosive leachate attack on services and buried con- tion, the manner in which it was placed, and the method crete below the water table (Eglington, 1979), should beas- and degree of compaction. The problems associated with sessed. Made Ground and fill include the generation of methane, In terms of its engineering characteristics, Made Ground carbondioxide and hydrogen sulphide gases, toxic and fill is classified as a heterogeneous deposit (Table18). leachates from waste disposal sites, buried voids and un- derground combustion. In the case of Made Ground com- Superficial (drift) deposits posed of colliery waste, conditions are more predictable, The superficial deposits of the Black Country may be di- butswelling due to pyrite decompositionbelow founda- videdinto four categories based on their lithologyand tions may pose a problem at somesites. geotechnical characteristics (Table 18). Soils (in the engi- When fill material is utilised as part of an engineering neering sense) are initially classified on grain-size. The dis- scheme, the material used should be placed in a controlled tribution of engineering geological categoriesof superficial manner and compacted to a specific density. Fill used as (drift) deposits is shown in Figure 16 and map 9A. part of a waste disposal in backfilled quarries and pits In general, cohesive soils are fine-grained materials such may vary from relatively inert, inorganic waste such as as claysand silts; non-cohesive soils are coarse-grained mine waste or building rubble to organic domestic refuse. materials such as uncemented sands and gravels. The finer The geotechnical properties of such a site will depend on soils, clays and silts, where the component particles adhere the nature of the fill material, and the geological struc- to eachother by natural inter-particle forces are termed ture, lithology and geotechnical properties of the superfi- ‘cohesivesoils’. The coarser soils, sands and gravels, cial deposits or bedrockof the excavated pit or quarry. In where the component particles do not naturally adhere one the case of organic material and any chemical wastes the to another without a cementing agent are termed ‘non-co- nature of thematerial may change with time as decay hesive soils’. Further classification of soil is made on the proceeds. The decay of organic material in domestic refuse basis of plasticity tests (liquid and plastic limit) for cohe- may cause a loss of volume of up to 50%, andmay result in sive soils, and detailed particle-size analyses for non-cohe- thegeneration of methaneand hydrogen sulphide, and sive soils. toxic leachate. Migration of potentialy explosive gases and The buried bedrock channelsinfilled with drift deposits, toxic liquids may then take place throughthe fill deposit or locally up to 35 m thick, located in the west and north- into adjacent strata by way of interconnected pores or open west of theBlack Country are of greatsignificance to fissures. Excavation is usually possible with normal dig- geotechnical investigations and foundation conditions. The ging equipment but stability may be poor and support will form and types of fill of these deposits are briefly dis- be necessary. Precautions should also be taken, in pits and cussed on p. 35. It is important that detailed site investiga- trenches, against the possibility of toxic materialsbeing tions are carried out on or adjacent to these buried chan- presentand the accumulation of carbondioxide and nels (Maps 3A, 3B), since the drift deposits infilling the methane. depressions are typically heterogeneous and are subject to Made Ground and fill in the Black Country consists of a rapid lateral variation. wide variety of materials both natural, such as clay, sand, Head is a heterogeneous deposit (like Made Ground and silt, gravel, mudstone, sandstone and colliery waste (which comprises a mixture of these materials together with car- fill) and together with peat (organic deposit), it is described bonaceous shale and coal), and artificial, such as brick rub- separately. ble, foundry slag, ashand domestic wastit.. In the study Heterogeneous Deposits area, geotechnical data (Table 22) for Made Ground and fill are biased towards colliery spoil which repesents the Head most widespreaddeposit. Head is derived from superficial or bedrock materials by Standard penetration test (SPT) ranges from less than 4 the weathering, erosion and downslope movement of de- to 33 (very loose to dense) with a median valueof 11. Low posits ona local scale, during periglacial conditions, by Table 18 Engineering geological categories

ENGINEERING TYPE OFDEPOSIT OR GEOLOGICAL UNIT LITHOSTRATIGRAPHICAL UNIT A Over consolidated Till (Boulder Clay) Sandy Till Cohesive B Normally consolidated Glaciolacustrine Deposits(silt and clay) Alluvium (other than alluvial gravel) Lacustrine Deposits

Glaciofluvial Deposits Glaciofluvial Terrace Deposits Interglacial Fluvial Terrace Deposits Glaciolacustrine Sand River Terrace Deposits

Head Made Ground Peat

Aymestry Limestone UpperQuarried Limestone Much Strong Rock Nodular Limestone Wenlock LowerQuarried Limestone Limestone Barr Limestone 1 Dolerite

Bromsgrove Sandstone Sandstone Wildmoor Sandstone with some conglomerate Kidderminster Formation

Bridgnorth Sandstone A Downton Castle Sandstone Rubery Formation

Mercia Mudstone BEDROCK Mudstone Clent B.reccia (northern part of area) (SOLID) with some siltstone Elton Formation and fine sandstone Coalbrookdale Formation Temeside Shales Foramtion

Clent Breccia (southernpart of area) Interbedded mudstone Enville Formation and sandstone Keele Formation Halesowen Formation Etruria Formation Coal Measures Ledbury Formation Whitclifle Formation

Lithostratigraphical units shown in italics have small outcrop areas for which there are no geotechnical records. The Engineering Geological Category of these units is inferred from their principal lithological characteristics Table19 Coefficient of CLASSDESCRIPTION OF Mv (m2MN) EXAMPLES volume compressibility, COMPRESSIBILITYcompressibility, volume Mv 5 Very high >1.5 Very organic clays and peats and claysorganic Very >1.5 high Very 5

4 High 0.3-1.5 Normallyconsolidated alluvial clays, e.g. estuarine clays

3 Medium 0.1-0.3 Glaciofluvial clays, Lacustrine clays

2 Low 2 0.05-0.1(Boulder Till clays)

1 low Very >0.05 overconsolidatedHeavily 'boulder clays'. Stiff weathered rocks

Table 20 Coefficient of CLASS Cv (m2/year)PLASTICITY INDEX SOIL TYPE consolidation, Cv 1

2 0.1- >25 High Plasticity

3 1-10 25-15 Medium Plasticity

4 10-100 15 orless Low Plasticity

5 > 100 SILTS

Table 21 SulphatesinCLASS TOTAL SO3 (%) SO3 In 2:l SO1L:WATER SO3IN GROUNDWATER soil and groundwater. <0.2 <30 1 <0.2

2 0.2-0.5 30-1 20

3 0.5-1 .o120-500 1.9-3.1

5 >500 >2 >5.6 processes such as solifluction, soil creep and hill wash. Head Organic Deposits is commonly thin, up to 2 m thick, but greater thicknesses Peat may accumulate in hollows and at the foot of slopes. Com- positionvaries with that of theparent material as do Organic deposits such as peat, and organic rich clay and geotechnical properties which tend to be similar to those of silt, occur locally as channel infills within alluvium and la- the remoulded parent. On slopes, Head may contain relic custrine deposits, but are not common, at surface, in the shear surfaces which may be reactivated even on shallow study area. The geotechnical properties of peat are taken slopes if the stability of the slope is reduced by, for exam- from investigations outside of the Black Country, but the ple, undercutting during excavation, orby introducing water results are considered comparable. into the slope (Hutchinson et al, 1973). Where Head is thin Engineering problems causedby peat and highly organic it is usually removed before foundations are placed. Where silts are due to the low strength, high compressibility and the deposit is thick, its low strength and high compressibili- high groundwater content. Peat commonly occurs in rela- ty can lead to excessive settlement. Excavations in Head tively small, isolated bodies which may be susceptible to will require support, and water inflowmay cause collapse. differential settlement compared to the adjacent less com- pressible materials. Concrete foundations may suffer dam- Head may vary from a cohesive clay with a soft to stiff age due to sulphate or acid attack by acidic groundwater. consistency such as the red clay found adjacent to the Ha- Organic deposits may generate methane, but therisk is less gley Road which is derived from the Keele Formation, or a than in backfilled landfill sites. non-cohesive material composed of gravel or rock frag- Engineering solutions to these problems include removal ments with a looseto dense relative density. of the peat and replacement by inert fill, raft foundations, Chemical tests indicate that conditions are near to neu- piled foundations and the use of chemical attack-resistant tral pH and sulphate content conformsto class 1 conditions mixes for buriedconcrete. for sulphate attack on buried concrete (Anon 198la). Cohesive Deposits This category (Table 18) is subdivided into overconsoli- Table 18 Engineering geological categories. dated and normally consolidated types (see Glossary for

53 Density Undrained Triaxal Type of Compression Test Deposit Moisture ,iquid ’lastic ’lastic Bulk Dry SO3 Undrained IZ)” 3PT Content imit Limit ndex Density Density lass Cohesion 0 N’ % % 36 % MgIm3 MgIm3 kPa

Head 20 52 12 14 12 26 18 25 24 26 26 46 20 40 22 18 2.10 1.72 6.40 1 62 0 31 2378 17 51 i2 !1 24 .1 29 1.982.24 1.55 1.91 5.20 6.80 1 1 43 118 08 13 3096 14 1.832.29 5.8017.20 1 33 163 0 11

~~

4lluvium 45 92 50 50 50 56 53 23 24 51 49 :xcluding 33 22 36 19 18 2.01 1.57 7.10 1 24 0 gravel 67 12 16 32 !8 44 15 23 12 22 1.862.16 1.31 1.84 5.80 7.70 1 67 1 13 05 4 42118 13 !3 2752 14 27 11 1.702.24 1.121.95 6.607.80 1 1 7 141 0 18 10 63 10

Slaciofluvial 508 96 40 40 40 52 41 79 74 39 39 Sand and 22 15 26 17 10 2.15 1.84 7 .OO 1 72 4 Gravel 33 14 18 13 !3 1832 15 7 14 2.092.34 1.762.00 6.207.40 1140 122 0 12 9 48 11 21 19 2336 13 4 18 2.042.35 1.712.14 5.507.70 1124 210 0 25 5 81 8 26 4.909.10 120 600 0 39

Alluvial and 36 3 3 Glaciofluvial 30 6.50 1 Terrace 48 20 6.507.10 11 Deposits 85 14

Alluvial 24 2 2 Gravel 26 6.70 17 49 17 6.507.00 12 11 68

~ ~~

Glacio- 54 359 228 225 228 280 285 19 20 196 19( lacustrine 16 20 30 19 12 2.06 1.71 7.10 1 86 3 Deposits 26 12 23 17 17 36 16 21 8 16 2.002.11 1.63 1.81 6.807.20 1 1191 62 09 10 42 10 28 14 24 2548 14 6 23 1.842.21 1.381.89 6.507.50 1 1531 40 0 18 4 93 11 87 20 5585 12 3 33 1.332.27 0.722.02 3 290 0 3c

Till 263 686 320 321 32 1 517 298 187 184 357 35’ 24 14 28 15 14 2.19 1.94 6.60 1 80 4 12 44 12 11 3517 14 13 1818 10 2.112.26 1.842.05 5.407.30 11125 40 0 12 6 90 10 4521 20 11 21 7 24 2.022.32 1.732.12 4.307.70 1122 184 0 17 4 295 9 31 17 2452 10 4 31 1.882.37 1.492.16 4.008.10 12260 10 0 28

Made Grounc 706 282 55 5 53 114 71 289 295 107 10 and Fill 11 21 43 24 21 1.99 1.62 7.00 1 60 3 6 2720 16 39 2651 20 27 17 1.802.13 1.491.77 6.507.40 1241 102 09 4 33 13 6937 19 29 17 38 13 1.612.19 1.31 1.92 6.208.20 12147 19 0 13 2 54 10 . 8260 24 14 40 8 55 1.492.27 0.852.05 5 70 9.30 14205 10 0 1s

Number of values Median value P ercentile Quartile values Quartile Percentile 50%:5F values 90 4;;97.52.5 Key for explanation offields

Table 22 Summary of geotechnical datafor superficial materials (seekey for explanation of fields).

54 racture Jnconfmed :alifornia Particle size analysis Consolidation :::nationQuality pacing :ompressive Compaction #caring 1 ldex ltrength .atio c’lay Silt Sand ;ravel MV ;SI dPa via Dry Optimum 1.B.R % % ‘0 :lass nmc lensity M.C. b 70 dg/rn3 %

18 18 23 23 5 0 10 71 16 2 3 7 7 14 17 62 80 3 13 3 10 2 23 11 85 2 85

88 88 20c 20E 8 3 3 4 0 4 33 58 1 2.05 11 9 0 0 2 11 19 55 !9 3 76 1 1.9213 2.05 9 5 14 0 3 0 17 10 79 8 88 0 8 0 23 3 87 1 97

29 29 35 35 0 0 11 87 0 0 0 1 8 17 $0 92 0 0 0 20 3 2 76 94

~

13 13 18 18 0 2 11 87 0 0 0 3 7 26 70 90 0 0 38 10 5 $2 93

11 11 65 1 44 24 2 8 19 4460 1 13 1 1: 13 13

~

18 17 24 29 34 7 7 t 0 27 41 33 2 1.86 14 13 0 45 6 15 21 61 16 67 13 1.63 1.95 11 22 2 lb 0 16 0 6463 5 92 1 3 1 13

41 60 30 65 25 41 44 84 18 46 33 94 5 62 5 15 98

55 Density Undrained Triaxal Lithostrati- Compression Test graphical I jPT Moisture Liquid Plastic Plastic Bulk ,H Unit DV so3 Undrained 0" N Content Limit Limlt Index Density Density Class Cohesion 0 % % % % Mg/m3 Mg/m3 KPa

Mercia I 1 2 7 Mudstone II 19 6.10 1

Bromsgrove 32 8 6 6 6 5 5 6 6 5 5 Sandstone I48 15 27 14 14 2.19 1.89 6.50 1 57 6 !I 236 13 1928 25 13 16 11 14 2 13 232 1.86 1.92 1.40 6.60 1151 63 01 12 248

Wildmoor 84 20 19 Sandstone 109 7.35 1 j4 16: 1.85 7.50 11 33 23( 1.60 8 00 11 13 30(

Kidderminster 7 1 1 Formation 112 8.00 8 57 20(

7 Bridgnorth 13 1 1 2 1 1 Sandstone 107 10 2 05 7 60 1 30 0 70 III

Clent 87 43 17 17 17 17 11 17 17 23 23 Formation 66 13 39 18 21 2 19 1 89 7.10 1 86 13 $3 16: 11 16 34 44 16 19 18 27 2.08 2.27 1.77 2.00 i.50 7.60 1155 18 110 6 19 19 301 9 30 50 21 1529 15 2.04 2.32 5.307.80 1133 140 1 27 12 901

Enville 7 Formatlon 50 50 50

Keele 111 29, 191 19 19( 168 15( 29 32 130 131 Formatlon I62 12 40 19 21 2.24 2.02 72 1 109 11 60 27' 60 10 14 35 45 17 21 25 17 2.18 229 1.94 2.1C 7 00 7.60 1169 139 4 18 50 371 50 8 17 28 52 15 23 13 31 2.082 35 1.832.15 7 00 8.60 1143 195 0 25 14 99 6 22 25 60 13 26 9 37 2.00 240 1.732.23 5.90 10.00 1117 260 0 33

Halesowen 79 38 19 19 19 24 22 11 11 29 29 Formation 120 16 39 20 20 2 10 1.84 7.00 1 I03 16 50 201 50 12 18 31 46 17 22 12 25 2 03 2.23 175 1.95 5.50 ..7.30 1162 147 3 25 21 301 21 21 8 23 53 14 23 7 33 1 99 2.32 1.70 2.11 1114 175 0 30 13 29 601 7

Etruria 56 92 30 29 29f 363 27t 91 91 294 29 Formation 50 14 40 20 19 2.16 1.92 7 1 103 6 46 77 11 17 33 45 18 22 15 24 2.10 2.24 1.81 2.0( 5.80 7.30 1156 144 0 14 30 21 13 9 29 52 17 24 10 29 2.00 2.29 1.67 2.0E 5.50 7.90 1230 180 0 23 17 28 25, 7 18 60 15 28 I 37 1.85 2.36 1.50 2.15 5.90 8.50 1311 254 0 28

19 14 59 60 59 8C Coal 62 15 41 20 22 2.07 Measures 39 9f 2( 11 37 48 18 23 27 18 199 2.1' 22 19 8 2f 33 57 16 27 12 30 1.90 23( 9 36 6 3: 31 63 14 32 10 38 1.70 2.3'

Elton 18 3 3 3 3 7E Formation 46 3 43 28 15 2.63 18 8: 23 21 56 35 32 14 24 2.622.6)

Upper 3 3 Quarried 0 2 68 Limestone 01 2.68 2.61

Nodular 1: 3 3 3 I1 Limestone 1 49 28 19 2.65 11 40 52 24 33 16 21 2 65 2.61

Lower 1 2 Quamed 0 2.70 Limestone

Coalbrookdall 51 2. 2c 2( 20 2: Formatlon 183 15 31 19 15 2 15 85 25 12 I' 30 35 21 17 12 18 208 22 50 28 8 I' 28 54 14 2: 11 32 2.03 2 3'

Dolerite e 68 46 9.

Table 23 Summary of geotechnical data for bedrock materials (see keyfor explanation of fields). :ock 'racture :ahforn Particle size analysls Consolidation luality pacmg mnng Number of values )eslgnation Idex -atio Median value Quartile values jilt Sand ;ravel \?V V ;SI Z.B.R 6 RQD 7 values ro % :lass :lass % nm 97.5

2 Key for explanation offields 15 84 1

2 2 15 I! 18 80 2 56 161 5367 9: 22 76 44 107 20.

2: 2; 2 16 80 2 12 2( 72 8L IO 21 66 8t

15 80 2 3 2: 70 91

2 81 8 61.5 16.51 33 9 $4 75 2 12 65 5 I( 0 82 3 2f 0 97 2 4(

5 5 1 1. 13 34 2 3 13 16 12 26 :2 61 I !: 12 1' 5

14 13 II

12 3 3 48 I I:35 68

157 41 2 3 41 999 1:14 65 500 99' 3 81 250 99' 3 95 167 99

25 40 59 200 31 82 50 50 8 92 20 99 3 99

17 2( 86 250 65 93 184 99'

45 91 87 999 63 94 333 99

9 9 83 999 12 95 999 99

5 60 999 12 9! 999 99

Cohesive Deposits Alluvium and Lacustrine Deposits This category (Table 18) is subdivided into overconsoli- The Alluvium andlacustrine deposits of the study areapre- dated and normally consolidated types (see Glossary for dominantly consist of CLAY which is oftensilty, sandy or definition). gravelly and less commonly organic. Silty and clayey In general the overconsolidated materials, such as Till SAND are also present in significant amounts with smaller (Boulder Clay) and Sandy Tilloffer good bearing capacity amounts of SILT and some GRAVEL. but may contain patches of softer material and lenses of Penetration test data show a wide range of values and sand and gravel. Shrinking and swelling of the clays is un- when plotted against depth no clear relationship is evident likely to be a problem, and sulphate attack on buried con- due to the wide range in material type. However, when split crete below the water table is unlikely. Excavations may into subsets based on lithology a generaltrend of increase in usually be accomplishedby digging equipment, butmay be value with depth is apparent. Clay lithologies vary from firm difficult if boulders are present. The stability of excava- to hard over the depth range of 1 to 8m and gravel litholo- tions is usually good unless water-bearing gravel, sand or gies from medium denseto very dense over the depth range silt cause running conditions, flooding and side collapse. 2 to 8 m. The relationship for sand is scattered but ranges Trafficabilityshould be reasonably good except where from loose nearsurface increasing rapidly to very dense. No patches of soft clay are present. relationship is apparent for silt. Undrained cohesion for silt and clay lithologies has a Till and SandyTill median value of 24 kPa (soft) and ranges from verysoft to Samples analysed in the study area indicate that the Till is stiff. Moisturecontent for clays and silts, medianvalue predominantly an overconsolidated silty sandy or gravelly 22%, shows a fairly wide spread in value down to 6 m CLAY with some silty clayey or gravelly SAND, with a depth but no correlation is seen with depth except where variable pebble content. Sandy Till has a higher proportion the deposit has been buried by thick fill and moisture con- of sand in the clayey matrix and is often interbedded with tent has dropped to between 10% and 18%. thin lenses of clayey SAND and GRAVEL. Plasticity data show the alluviumto comprise mainly in- The median valueof standard penetrationtests for Till is organic clay of low and intermediate plasticity. A few or- 24 (very stiff) and ranges from 6 (firm) to 90 (very hard). ganic clays and silts of high and very high plasticity are SPT results show an increase in value with depth from 1 present and some sandy clay of low plasticity. Moisture metre to 12m depth. Undrained cohesion has a median content is usually greater than, or close to, the plastic limit value of 80 kPa (stiff) and ranges from soft to very stiff. It which isindicative of a normally consolidatedclay. shows a tendency to increase with depth but high values Chemical tests show conditions close to neutral with a occur nearto the surface. median pH value of 7.1 and class 1 conditions for sulphate Moisture content, median value 14%, shows a spread in attack on buriedconcrete. values from 6% to 53% down to a depth of 9 m, but below this the range is 8%to 18%. Glaciolacustrine Deposits Plasticity data show the Till (Boulder Clay) to be an in- Glaciolacustrine Deposits consist mainly of normally con- organic clay of low plasticity. The data plot above the A solidated silty CLAY or clayey SILT; either may also be line of Casagrande plasticity chart (Casagrande 1948) and sandy, gravelly or organic(peaty). on, or a little below, the T line (Boulton and Paul 1976). Gravelly, silty or clayey SAND is also present together Theimplication is that thosesamples which fall on, or with small amountsof clayey or silty PEAT. close to, the T line, are of relatively undisturbed lodgement The median value for standard penetration testN value for Till but those which fall closer to the A line are flow till or undifferentiated sand, silt and clay Glaciolacustrine Deposits have been disturbed by periglacial processes and weather- is 16 ( stiff clay, medium dense sand) and ranges from 10 ing. Plots of moisture content against plastic limit show a (stiff clay, loose/medium dense sand) to 42 (hard clay, dense majority of samples to have a moisture content below the sand). The N value is greater with increasing depth. The me- plastic limit and confirm the interpretation of the material dian value of undrained cohesion for silt and clay lithologies as predominantly overconsolidated lodgementtill. Consoli- is86 kPa (stiff) andranges from 40 kPa to 153 kPa. dation data show the Till (Boulder Clay) to have very low Undrained cohesion results show a slight trend of increase in to medium compressibility withfairly fast consolidation. value with depth butthere is considerable scatter. Chemical tests indicate slightly acidic or acidic condi- Moisture content has a median value of 20% and values tions to prevail. Class 1 conditions for sulphate attack on range from about 10% to 30%; there is a distinct fall in buried concrete are usually found, but class 2 conditions moisture content towards a value of about 10% at 40 m are sometimes present. depth. The exceptionsto this trend are samples of highly or- The normally consolidated Alluvium, Lacustrine De- ganic material from between 8 m and 18 m which have posits andGlaciolacustrine Deposits offer poor bearing moisture contents inthe ranges 30% to 170%. capacity and may suffer severe, possibly uneven, settle- Plasticity data show that the Glaciolacustrine Deposits ment.Settlement may be rapid, over peat or laminated comprise a number of different materials, chiefly consist- silt, sand and clay, or slow on soft clay. These deposits ing of inorganic clays of low plasticity with some samples are easily dug but the excavation stability may be poor in the intermediate plasticity category. and require more support than normal practice. Traffica- Consolidation dataindicate that, in general, the Glaciola- bility is poor; a desiccated crust may be present which custrine Deposits have lowto medium compressibility with gives reasonable trafficability until disrupted when traffi- medium to fastconsolidation. However, the variation in cability will deteriorate rapidly. Sulphate attack on con- lithology found within the Glaciolacustrine Deposits will crete buried below the water table is unlikely, but aggres- give a wide rangein consolidation behaviour. sive ground-water conditions may be found in or near to Chemical tests show close to neutral pH conditions to peat deposits. Silt lithologies close to the surface may be prevail and sulphate content to conform to class 1 condi- susceptible to frost action. tions for sulphate attack on buried concrete'.

59 Non-cohesive deposits Much Wenlock Limestone Thenon-cohesive deposits comprise Alluvial gravel, The Upper and Lower Quarried Limestones Members (UQL GlaciofluvialDeposits (sand and gravel), Glaciofluvial and LQL, respectively) consist of LIMESTONE with thin TerraceDeposits, Interglacial FluvialTerrace Deposits, SILTSTONE partings. The LQL has a rock quality designa- GlaciolacustrineSand and River Terrace Deposits. They tion (RQD) median value of 83%, and high fracture spacing offer good bearing capacity with very low and rapidsettle- indices classify it as‘good’ quality; amedian unconfined ment. Standard penetration test results may be an unreli- compressive strength of 58 MPa (two values 40 and 76) in- able guide to bearing capacity due to the coarse nature of dicate that it is a moderately strong rock, although this value the deposit. ispossibly lower than expected for this formation.The Excavations may be accomplished by digging equipment Upper Quarried Limestone has a similar lithology and the but sides may require support to maintain stability. Water rock quality designation median value is 86% (good). The inflow into excavations below the water table may be ex- medianvalue for unconfinedcompressive strength is 81 cessiveand require dewatering measures to betaken. MPa (3 values) which classifies it as a strongrock. Ground will be free draining and trafficability should be The Nodular Limestone consists of interbedded LIME- good. Material is generally suitable as fill and as a source STONEand SILTSTONE. The rock quality designation of aggregate but some selection will be necessary in the values are high with a median value of 86% (good). Un- Glaciofluvialand Glaciolacustrine deposits. Sulphate at- confined compressive strength with a median value of 37 tack on concrete buried belowthe water table is unlikely. MPa indicate it to be a moderately strongrock. Alluvial Gravel Dolerite Alluvial gravel is not distinguishedon the maps, but pock- No data were available for dolerite in the Black Country, ets and lenses may be present withinthe Alluvium. The de- but in general it is a strong rockwith a high bearing capaci- posit consists of GRAVELor sandy GRAVEL locally, ty; low and high angle cooling jointsmay be present which with thin intercalations of SAND and sandy CLAY. Stan- couldinduce failure on high angle slopes, particularly dard penetration test data show it to be mainly medium wherethe dolerite is in contactwith mudstones of the dense, and particle size analyses confirm it is a GRAVEL Etruria Formation. or sandy GRAVEL. Sandstone RiverTerrace Deposits, Glaciofluvial Terrace Deposits, Sandstone formations generally offer good bearing capaci- and Interglacial Fluvial Terrace Deposits ty with very low and rapid settlementof weathered materi- al. Some silty or fine sandy lithologies may be frost sus- Thesedeposits mainly comprise sandy GRAVEL or ceptiblenear to thesurface and affect shallow(<0.5m GRAVEL. Standard penetrationtest data show the material deep)foundations such as concrete paths. Excavatability to be be mainly medium dense or dense, and particle size depends, in part, on the weathering state, varying from dig- analyses confirm itto be a sandy GRAVEL or GRAVEL. gable in the weaker sandstones (Bridgnorth and Wildmoor Glaciofluvial Deposits and Glaciolacustrine Sand formations)and weathered material, to rippable in the strongersandstones (Bromsgrove Sandstone). The lower These deposits consist of impure sands andgravels, includ- part (c.20 m) of the kddenninster Formation is a locally ing sandy GRAVEL and gravelly SANDwith a small com- cemented pebble conglomerate which may prove unsuit- ponent of silt or clay. Standard penetration test data show able for excavationby digging or ripping and require pneu- that they range from looseto dense, but are generally medi- matic tools or blasting. Excavations should be stable in un- um dense. weathered materialbut support will be needed in weathered Bedrock materials materialwhich may be reduced to sand.Trafficability should be very good but with the possibility of some silty, Theengineering geological classification of thebedrock sandy clay being presentin some formations whichmay im- strata, based on their lithology and geotechnical character- pair trafficability when wet. No sulphate or chemicalattack istics, isoutlined in Table 18, and their distribution is on concrete buriedbelow the water table is likely. shown in Figure 17 and Map 9B. The general characteris- tics regarding design considerations are described below, Bridgnorth Sandstone followed by moredetailed information on each of the This unit is a SANDSTONE or silty SANDSTONE which bedrock formations. weathers to a SAND or silty SAND. Standard penetration test values show an increase with depth and range from40 Strong rock (dense) to >50 (very dense sandto weak rock). This category is characterised by very good bearing capaci- ty except where ground is undermined by limestone work- Kidderminster Formation ings in the Upper or Lower Quarried Limestone members The Kidderminster Formation consists of a weakly cemented of the Much Wenlock Limestone (see p.23) Excavation is SANDSTONE or SAND with a median penetration test value difficult and may require blasting in Dolerite and the Upper of 112. At outcrop the lower part (c. 20 m) of the formation and Lower Quarried Limestones. The Nodular Limestone generally consists of poorly cemented CONGLOMERATE, may be rippable especially where weathered. Slope stabili- which locally formsa strong rock where it is cementedby cal- ty is controlled by discontinuities within the rocks. Low cium carbonate. Conglomerate and pebbly sandstone beds de- angle cooling joints in dolerite and thin mudstone beds in crease in abundance upward through the unit. the Upper and Lower Quarried Limestonesmay be a prob- lem where they are coincident with hill slope or intersect Wildmoor Sandstone Formation an excavated face with a dip into the excavation. Sulphate TheWildmoor Sandstone consists of siltyor gravelly or chemicalattack on buried concreteis unlikely. SANDSTONEor SAND. The median penetration test

60 value is 109. Few tests results fall in the range N = 10 to N phate attack on buried concrete. However, gypsum beds are = 50 indicating loose to dense sand; most test results fall in present in the Mercia Mudstone and some high sulphate the N >50 range indicating very dense sand or weak rock. values up to and including class 5 are present. Particle size data (22 samples) -confirm that the Wildmoor Sandstone is predominantly a silty sand with median parti- Clent Formation (northernpart of the area) cle size values of clay O%, silt 15.5%, sand 80% and gravel In the northern part of the Black Country the typical brec- 1.5%. cia lithology of the Clent Hills is absent and the formation is represented by SILTSTONE, silty CLAY and SAND- Bromsgrove Sandstone STONE,and less commonly clayey, silty or gravelly TheBromsgrove Sandstone predominantly consists of SAND and sandy or gravelly CLAY. Standard penetration SANDSTONEand gravelly SANDSTONE, occasionally test values for clay lithologies show an increase in value silty orclayey, and weathers to clayey, silty orgravelly from about 10 (stiff) to 50 (hard) in the depth range 2 to 6 SAND. Silty or sandy MUDSTONE beds may also be pre- m. Penetration test data for N >50 (weak rock) mainly re- sent,which weather tosilty, sandy or gravelly CLAY. late to sand or silt lithologies and show a wide scatter with Standard penetration test values for sand lithologies range no correlation with depth. Undrained cohesion for mainly from 6 (loose) to 50 (dense) and extendas extrapolated val- clay lithologies has a median value of 86 kPa (stiff) and ues to 250 (weak rock). Rock quality designation data for ranges from soft to very stiff over the depth range 0 to 6 m. sandstone lithologies give a median valueof 56% (fair) and The median value for rock quality designation for Clent range from poor to good. The higher values and hencebet- Formation as a whole is 33% (poor) and ranges from very ter quality rock are associatedwith well-cemented, con- poor to good. Plasticity datashow the ClentFormation glomeratic sandstonerather than sandstone. clays to be inorganic clays of low to intermediate plasticity . Moisture content is usually belowthe plastic limit. Chem- Mudstone ical tests show conditions to be close to neutral, pH 6. Sul- Unweathered mudstones generally offer good bearing ca- phate tests show conditions to be class 1 for sulphate attack pacity, although weathered mudstone will be softened to a on buriedconcrete. greater or lesser extent and will offer lower bearing capaci- ty accordingly. The mudstones are unlikely to cause prob- Elton Formation lems due to swelling or shrinking clays except for some The Elton Formation is a heavily overconsolidated SILT- higher plasticity layers which may have a higher potential STONE with some LIMESTONE bands, weathering to a for shrinking and swellingwhen weathered and remoulded. silty CLAY or clayey SILT. RQD has a median value of The mudstones will soften on exposure to water and exca- 59% (fair) and ranges from very poor to excellent. Uncon- vations should be protected with a blinding of lean con- finedcompressive strengths havea median value of 35 crete. Excavations should be achievable by digging with MPaand classify theElton Formation as amoderately the possibility that harder mudstone and occasional sand- strong rock. Standard penetration test N values for material ston;, limestone or conglomerate beds may require ripping. within 10 m of the surface and, therefore, presumed to be Excavations may be stable in the short termbut may re- moreor less weathered,range from 15 at about 1 metre quiresupport for long term stability. Sulphate attack ondepth to >50 at about11 m. Plasticity values(3 samples) buried concrete is unlikely except in the Mercia Mudstone indicate an inorganic silty clay of intermediate to high plas- which may containgypsum, although this isoften leached ticity. out of the near-surface zone. Consequently, foundations in the weathered zone are unlikely to suffer attack. Traffica- Coalbrookdale Formation bility of themudstone formations may be poor in wet This formation consists of heavily overconsolidated MUD- weather. STONEor SILTSTONE, weathering to silty CLAYor clayeySILT; nodular LIMESTONE is also present. The Mercia Mudstone unconfined compressive strength of the formation ranges Too few data wereavailable from the project area fof com- from about 100 kPaat 4 m depth to approximately 1.5 MPa ment on the geotechnical properties of the Mercia Mud- at 10 m depth. This wouldclassify the unweathered materi- stone Group. However, the Mercia Mudstone of the Cov- al as aweak rock. Laboratory triaxial tests onmaterial entry area is similar to that of the Black Country and the from the softened 0 to 4 metre zone give undrained cohe- the following comments are taken from geotechnical stud- sion values in the range 40 to 200 kPa (median 84 kPa). ies in the Coventry area (Hobbs 1990). Fiverock quality designationvalues from 33 and 93 m The Mercia Mudstone is a heavily overconsolidated, fis- depth fall in the range 39% to 99% with the higher values sured CLAY which may be weathered to a depth of 10 m at the greater depth. Plasticity data show the formation to or more. Penetration test values show a general increase be a clay of low to intermediate plasticity; only two sam- with depth from about N= 30 (very stiff) at 2 m to N = >30 ples fall into the highclassification. The plasticity data are (hard) at 3 m; below 3 m N increases as the material be- mainly from samples in the 0-4 m depth zone and show a comesprogressively harder and may be classified asa range of 10% to 18% for plasticity index, but some sam- weak rock. The median value of undrained cohesion is 108 plesnear the surface, at less than1 metre depth, have kPa (stiff) with a consistency range from verysoft to hard. much higher plasticity indices of about 38%. Undrainedcohesion increases generally with depth over the depthrange 2-18 m. Plasticity datashow the Mercia Interbedded Mudstone and Sandstone Mudstone to bea clay of low to intermediate plasticity withInterbedded mudstone and sandstone usually offer good afew samples in the high plasticity category.Consolida- bearing capacity when themudstones are unweatheredand tion data indicate theMercia Mudstone to be of low to the site is notundermined by past coal, ironstone, fireclay moderatecompressibility and to consolidate fairly rapidly. orlimestone mining. Mining-induced hazards include Chemical tests indicate conditions to be slightly alkaline, ground collapse, underground fires in abandonedworkings median pH is 8.7, and to conform usually to class 1 for sul- and coal seams, and methane migration into underground

61 space giving a risk of explosion. Excavation of weathered Moisture content has a median value of 12% and ranges material is often possible with digging equipment but sand- from 6% to 27%, but this decreases to 5% to 18% below 10 stone units and unweathered material may require ripping, m depth. Plasticity data show Keele Formation clays to be the use of pneumatic tools or blasting. Mudstones will soft- inorganic clays of mainly low to intermediate plasticity but en on exposure to water and excavations should beprotect- with a significant number of samples in the high plasticity ed with a blinding of lean concrete. The sandstone beds class. may carry water and form spring lines on hillsides soften- ing the mudstones to the detriment of the stability of the Halesowen Formation slope. Sulphateattack on buried concrete is unlikely al- TheHalesowen Formation mainly consists of SAND- though some Coal Measures rocks containpyrite which has STONE or clayey SANDSTONE which weather to silty or caused problems due to pyrite breakdown and calcium sul- clayey SAND, interbedded with MUDSTONE and SILT- phate formationin some areasof the UK. STONE which weatherto silty or sandy CLAY. Penetration test results show a trend of increasing value with depth; the Clent Formation (southernpart of ai-ea) majority of values are greater than N= 50 and are classed as Geotechnical datafor the breccia-dominated faciesof this for- very dense sand or weak rock. The median value for un- mation, typical of the southern part of the outcrop, are sparse. drained cohesion for clay lithologies is 103 kPa (stiff) and The breccia has a weak clayey, locally carbonate matrix, and ranges from very soft to very stiff. Median moisture con- weathers to a clayey GRAVEL. The geotechnical characteris- tent, for mainly clay lithologies, is 16%. There is a distinct tics for the breccia are probably very similar to those of the drop in moisture content at a depthof 4 m from a range of gravelly clayof the northern partof the area (see above). about 7%-30% to 5%-12% which is interpreted as the ef- fects of weathering in the near-surface zone. Plasticity data Enville Formation for clay lithologies show the Halesowen Formation claysto The EnvilleFormation is a heavilyoverconsolidated silty be inorganic clays of low to intermediate plasticity. CLAY. At outcrop the formation predominantly consists of MUDSTONEinterbedded with thin SANDSTONE;both Etruria Formation lithologies are expected to have geotechnical properties simi- The Etruria Formation mainly consists of CLAYSTONE lar tothe underlying Keele Formation. Locally, however, andSILTSTONE with occasional sandy or gravelly well-cementedlimestone-chert CONGLOMERATES are SANDSTONE beds. In some areas it can be regarded as a present which are expected to fall in the ‘strong rock’catego- ‘soil’, mainly heavily overconsolidated CLAY, occasional- ry. ly sandyor gravelly; silty orsandy GRAVEL is locally present. Penetration test datafor mainly clay lithologies Keele Formation show a general increasewith depth down to 10 m. The me- TheKeele Formation predominantly consists of heavily dian N value for rock lithologies is 65 and ranges from overconsolidated MUDSTONE or SILTSTONE weather- about 50 to 186. The median N value for soil lithologies is ing to silty sandyor gravelly CLAY, with thin beds of 50 and ranges from about 21 to 87. Median undrained co- SANDSTONE which weathersto gravelly SAND. Penetra- hesionfor clay lithologies is 103 kPa, stiff, andranges tion test data show little correlation with depth in the N = 0 from soft to very stiff. Undrained cohesion shows a clear to 50 range. The undrained cohesion of Keele Formation increase with increasing depth from about20 kPa at 2 m to clay lithologies, median value 109 kPa (stiff) shows little about 180 kPa at 12 m. Median moisture content is 14% correlation with depth. and shows a distinct change at 10 m depth where the range

- Plate 8 Dolerite workings at

HailstoneQuarry, ,, Rowley Regis. Note the prominent vertical joints. Roadstone/ aggregate resource. Table 24 SLOPE GRADIENTANGLE AGRICULTURAL CONSTRUCTIONAL Categories of DESCRIPTION (degrees) PROBLEMS PROBLEMS slope (after Demek 1972, Level to gentle 10 in <1 4.7 Practical limitationsminimal Young 1972, or gently Crofts 1973, inclined. and Small and Clark 1982) Moderate or 1 in 10 5.7-18.4 Difficulties for Major industrial strongly to large scale construction and inclined. 1 in 3 mechanical engineering agriculture. structures present Soil erosion a difficulties. Limit problem for railways.

Steep to >1 in 3 A8.4 Mechanical Extreme difficulty precipitous cultivation in most construction and vertical highly including roads and problematical housing. requiring special measures (viz. contouring and terracing). of moisture content drops from about10% to 40% down to workings on one side of a fault may result in subsidence- about 5% to 22%. Plasticity data show Etruria Formation induced damage along a zone parallel to the fault. Conse- clays to be mainly inorganic clays of low or intermediate quently, site investigations should attempt to precisely lo- plasticity. cate any faults whose presence is suspected from surface or underground information. It is advisable not to place rigid Coal Measures constructions across faults, but if this is unavoidable then The lithologically heterogeneous Coal Measures predomi- appropriate engineering solutions allowing for differential nantly consist of heavilyoverconsolidated SILTSTONE, settlementshould be adopted. No differentialmovement weatheringto silty or silty sandy CLAY, and SAND- along faults other than that induced by mining subsidence STONE. Penetration test values show a wide range from has been noted in the area. about 10 at 2 m depth to 350 (extrapolated value) at about Joints are common in the more massive bedrock units, 16 m. The high N values relate almost entirely to siltstone particularly the sandstones, limestones and dolerite. They lithology. Undrained cohesionshows a steady but scattered may have an effect on the stability of rock faces where increase with depth from the surfaceto 15 m depth. Uncon- water pressure or tree roots can induce slab failure; stress fined compressive strength values are few with a median releaseduring quarrying or excavation may alsoinduce value of 6.5 MPa for siltstone at about 15 m depth. Values open joints, particularly where the joints lie parallel or sub- of 36 MPa for siltstone and 50 MPa for sandstone are also parallel to the exposed face. Bedding plane joints are es- recorded.Rock quality designation values for the depth sentially the surfaces between the naturally stratified lay- range 0 to 50 m for siltstone and sandstone have a median ers; where the beds dip steeply at a rock face or on a slope, value of 62% (fair) and rangefrom very poor togood. such as the steep folds of the Silurian inliers, large areasof RQD for sandstone is generally higher than siltstone with a thebedded rock face may becomeunstable. Mining-in- lowest value of about 22% (very poor); RQD for siltstones duced subsidence may widen joints in the overlying strata. dropsto 0% (very poor)in the depth range 8 to 28 m. Roof collapse in the Silurian limestone mines is chiefly due Moisture content has a median value of 15% and decreases to to the effects of softening and removal of clay infill of in value from a range of 6% to 30% near to surface to a joints or solution along joints in the roof strata which be- range of 6% to 21% below 10 m. Plasticity data show the clay lithologies to be inorganic clays of mainly intermedi- come weakened, resulting in collapse of the roof of the ate plasticity. Coal Measures clays havelow compressibili- mines. At depths of 100 m or more, the weightof the over- ty and a medium rate of consolidation. Class 1 conditions lyingstrata is sufficient to cause the crushing of softer, for sulphate attack on buried concrete are usually found; a jointed strata, such as the Elton Formation, which forms few class 2 values and a single class 3 value have been the roof above theUpper Quarried Limestone. recorded. In weathered mudstone bedrockand clay-rich superficial deposits, small-scale faults and joints (fissures and shears) Geological structures caused by periglacial cryoturbation may be present. Relic shears in these deposits may affect foundation conditions; Faults and folds in the bedrock and superficial structures in excavated slopes may be subject to failure along the shear the Drift deposits or weathered regolithmay have an im- surfaces (Hutchinson et al., 1973). Cryoturbated materials portant effect on foundation conditions. are in a remoulded condition and have less strength than Bedrock faults shown on Maps 2A, 2B and in Figure 9 the parent deposit. commonly juxtapose strata of different lithology with dif- Stability of natural and excavated slopes ferent geotechnical properties (Plate 6). Insuch cases, load- ing may induce differential settlement resulting in struc- The stabilityof slopes is dependanton three main factors: turaldamage. In underminedareas, collapse of disused (a) the slope angle

63 (b) the nature, structure and strength of the underlying ma- Potentially explosive and toxic gases (radon, methane, car- terial (bedrock, superficial deposits or fill), and bon dioxide, hydrogen sulphide) (c) the influence of groundwater. Radon is a naturally occuring radioactive gas which origi- [Jndisturbed natural slopes have generally attained a con- nates from the decay of uranium present in geological ma- siderable degree of stability in our present climate; excava- terials, soiland groundwater, with minor amounts pro- tion, construction or exceptional climatic conditions may duced by building materials. TheNational Radiological disturb this equilibrium, and may present problems in cer- Protection Board (NRPB) have establishedthat exposure to tain circumstances. high levels of radon radiation will increase the risk of lung Slope steepness in the Black Country area is dividedinto cancer in the population. The main areas at risk are those variouscategories shown in Map7 and Table 24. Steep where the bedrock is granitic, or where uraniferous miner- slopes present little hazard to development provided water alisation is present, such as parts of Cornwall and Scotland. is not introduced to the slope and they are not undercut by However,marine bands in theCoal Measures and cav- excavation or natural features such as rivers. However, for- ernouslimestones such as theCarboniferous Limestone mer landslips andincipient unstable ground have been have been shown, in other areas, to produce relatively high recorded at anumber of localities (Map7). Areas most levels of radon, particularly in zonesadjacent to major prone to landslip inthe Black Country are thosewhere faults. No systematic monitoring records for radon levels mudstone-dominated strata such as the Etruria Formation are available for the Black Country. It is recommended, are overlain by water-bearing rock, such as the sandstone therefore, that reconnaissancesurveys are carried out in of the Halesowen Formation near The Hayes [93 1 8411, areas of cavernous limestone such as the Much Wenlock and interbedded sandstone/mudstoneunits such as the Coal Limestone of the Dudley area and parts of the Coal Mea- Measures near Stourbridge [9 10 8471. Heterogeneous de- sure outcrop, particularly where the marine bands rest un- posits such as Made Ground, fill and Headare also suscep- conformably on the Silurian limestone, and adjacent to the tible to landslip where they are present on steep slopes, major faults. Thick deposits of Made Ground consisting of such as Bury Hill [937 8941 (Hutchinson et al., 1973). colliery waste provide anothertarget for monitoring. Ingress of water in the permeable sandstones may increase the porewater pressure in the mudstones leading to failure Methane isa colourless, odourless, inflammable gas along relic shears and faults. Landslip may occur when the (CH4) which forms an explosive mixture with air at con- toe of a slope is disturbed by excavation, loading on the centrations of between 5 and 15% by volume. It is generat- slopeor the introduction of water.Small landslips have ed in landfill sites from the breakdown of buried organic been noted in canal cuttings in unconsolidated Glacioflu- material(anaerobic biodegradation) such as plant and vial sand and gravel near Spon Lane[SP009 8971. wood debris, organicdomestic material and coal waste; Failuresin competent rock types such as sandstone, during the first few years following burial, 1 tonne of do- limestone and dolerite are controlled by structural disconti- mestic waste produces about 30 cubic metres of methane nuities such as joints, faults andbedding planes. Steep annually. It is also generated during the mining of coal, and faces can fail by rock fall, planarsliding and wedge failure. may be liberated from the surface outcrops of coal seams, Preventive measures include the construction of concrete alonggeological faults, abandonedmine shafts and bell buttresses and rock bolting and the appropriate alignment pits (Staff et al., 1991). Methane is also a significant con- and angle of cut faces. Netting and the provision of catch tributor to ‘greenhouse gases’ in the atmosphere.Where fences, ditches or banks may be used to control the effects methane is generated biogenicallyit is accompanied by the of minor rock-fall. production of carbon dioxide(C02). Both gases can cause asphyxiation by the exclusion of air. If groundwater levels Earthquakes in abandoned mines rise, then there is a risk that entrapped methane and carbon dioxide maybe ‘pushed’ to the surface The Birmingham-Black Country regionis characteristically due to increased gas pressurisation. Migration of the gas a low seismicity area and is not known to have suffered may take place through the fill material, or via pore spaces fromany damaging earthquakes in the past. The largest and fissures (faults; joints) in the adjacent bedrock. Sites known historical earthquake was themagnitude 4.0 ML with known high levels of methane generation should be Birmingham event of 14 July 1940. Earthquakes this size carefully managed and monitored so that the gas is drained occur approximately once per year on Britain and its sur- or vented off by controlled collection or flaring. The risk of rounding waters. In the last twenty years, only a few small lateralmigration of landfillgases (and associated events have occurred in the area; the largest of which was leachates) can be reduced by the installation of impervious the magnitude 1.4 ML earthquake of 12 March 1986 which membranes between thelandfill material and the rock face, also had its epicenter in the Birmingham area. The region and/orbetween the fillmaterial and any overlying con- has also been shaken by two large, recent British earth- struction. Underground spaces in buildings on methane- or quakes. Both the magnitude 5.4 ML Lleyn Peninsula event carbon dioxide-bearing rocks andsoils should be positively of 19 July 1984 and also the magnitude 5.1 ML Bishop’s ventilated to avoid the build up of gas. In addition the fill Castle event of 2 April 1990 gave rise to intensities of IV material shouldbe vented to release any trapped gases. MSK in the Black Country. Hydrogensulphide (H2S) isa colourless, poisonous Movement on major faults, at depth, is thought to be the gas, with an unpleasant smell. It may be generated in land- cause of the earthquakes. Although the Black Country area fill sites where rotting organic materialis present. is crossed by many major faults, including the Western and If the landfill site is well managed the methane generat- Eastern boundary faults, historical records indicate that the ed can be utilised to provide a local source of fuel. Thus, a area is characterised by low seismicity. brick-claymanufacturer, for instance, could generate Detailed analysis of local seismic risk to major construc- methane from a carefully controlled landfill site created by tions such as pipelines and dams can be obtained from the excavatingthe brick-clay; methanethus generated could BGS Global Seismology Research Group, Edinburgh. then be used to fire the brick-kilns.

64 Guidelines for the control and treatmentof landfill gases parts of the Sherwood Sandstone outcrop will be included are set out in Department of the Environment publications inthe Source Protection Zones rather than as aMajor such as circulars 21/87 and 17/89, ICRL Guidance Note Aquifer.The current and new policies are implemented 17/78 and HMIP Waste Management Paper27. both by the NRA, withits own legislation, and via closeli- aison with other bodies suchas Planning Authorities using GROUNDWATER:POTENTIAL FOR CONTAMINATION AND RISING their relevant legislation. GROUNDWATER LEVELS Contributed by the National Rivers Authority. Rising Groundwater Levelsin the Birmingham aquiferunit Groundwater considertaions present constraints to land use The eastern part of the study area encompasses part of the in the Black Country area in two ways. Firstly, restrictions SherwoodSandstone aquifer centered on Birmingham. must be placed on developments which might cause pollu- Over the past century this aquifer has been extensively de- tion to themajor Sherwood Sandstone aquifer or other veloped for groundwater supply with mostof the heavy in- minor aquifers (Map 8), and, secondly, rising groundwater dustrial users in the area depending on their own wells and levelsmay cause problems beneath parts of theurban boreholesrather than relying on public water supplies. conurbation, particularly the coalfield area and the Sher- Groundwater development for public water supply usage wood Sandstone outcropin the east. has been limited due to the ready availability of surface water, via aqueduct, from the Elan Reservoirs in central Aquifer/Groundwater Protection Wales. The National Rivers Authority is charged with protecting TheBirmingham aquifer unit was characterised by the groundwater resourcesof the area. Prevention of pollu- falling groundwater levels from 1900-1960 (Land, 1966). tion is an important aspectof water resource management. Groundwaterabstraction reached a peak in the early TheNRA Severn-Trent Region currently operates an 1950’s after which there has been a gradual drop in both Aquifer Protection Policy which divides the area into four licensed and actual abstractions. This has been primarily zones relating to theimportance of the groundwater re- due to a pronounced decrease in industrial activity in the sources and proximity to public water supply and major Birmingham area; total abstractions now stand at 15 me- potable supply abstractions. The zones are defined below galitres per day, which is only thirda of what they were in and are outlined in Map 8. 1960. Zone 1 is defined as the area within lkm radius of public This reduction inabstraction has caused arise in ground- water supplies and other major potable supply abstractions water levels, with some observation boreholes recording a such as CrownExempt supplies to hospitals(Map 8). rise of over10 m in 16 years withinthe Birmingham Thesezones are generallylocated on the Triassic Sher- aquifer unit. This rise is most marked justto the east of the wood Sandstone outcrop inthis study area; the exception is study area and coincides with the area of greatest decrease the supply to the hospital at Churchfield which is sourced in industrial abstraction. There are noobservation bore- in Carboniferous strata. holes in the study area but itis estimated that the rise, over Zone 2 is the outcrop of the Sherwood Sandstone aquifer the same period, has probably been less, of the order of 6 and representsthe rest of the outcrop outsideof Zone 1. m, and no problems have been reported as a result of this. Zone 3 isdefined as minor aquifer outcrop where A research programme , instigated by CIRIA, entitled ‘Ris- groundwaterprovides locally importantabstractions for ingGroundwater Levels in Birminghamand the Engin- many uses, but in this area primarily for industry. It in- eering Implications’ will be published in March 1992, and cludes the Carboniferousstrata and the Clent Formation. will have some relevance to the study area. Due to rising Zone 4 is defined as non-aquifer where groundwater is groundwater levels the NRA is currently actively encour- not generally consideredto be present in significant quanti- aging increased groundwater abstraction in the Birming- ties. This zone includes the Silurian shales and limestones, ham aquifer area. Yields are generally good, but ground- the Mercia Mudstone and the igneous dolerite such as the water quality is extremely variable and the applicant, who Rowley Regis intrusion. requires a licence to abstract, is warned that the water may The NRA is currently producing a new national ‘Policy not be of potable standard. and Practice for the Protectionof Groundwater’. This doc- ument defines slightly different zones based on the vulner- HUMANACTIVITIES AFFECTING GROUhm CONDITIONS ability of the groundwater and sources. Policy statements Shallow and deep mining, and quarrying activities in the are made on a rangeof potentially polluting activities. The Black Country area have left a legacy of voids and pits, draft documentis currently out for public consultation some filled and others open. Most of the early mining oper- prior to review and final publicationlater in 1992. The Re- ations wereunrecorded and uncontrolled, and many are sourceProtection Zones A (MajorAquifer), B (Minor recorded inaccurately. Furthermore, unrecorded backfilling Aquifer) and C (Non Aquifer) broadly equate to the cur- of voids,together with constructed made ground, took rent Zones 2, 3, and 4, respectively, as listed above. The place until 1970 when thelicencing was introduced for Siurian limestones, however, are likely to be defined, in landfill sites. The following sections review the constraints the new document, as Minor Aquifers. The main differ- imposed on developmentby mining and former landuse. ence will be the Source Protection Zones defined,initially, around major potable supplyabstractions. These areas will Coal and Colliery-Based Mining include three protection zones including an inner protec- The long history of colliery-based mining (coal, fireclay tion Zone 1, defined to protect from bacterial contamina- andironstone) has left a legacy of shallowworkings, tion, an outer protection Zone 2, and the source catchment shafts, adits andbackfilled opencast pits whichpresent Zone 3, defining the area whereall the recharge will even- problemsfor land use, such as miningsubsidence, shaft tually reachthe borehole(s). These zones will varyin collapse and poor foundationconditions. shape and size according to local hydrogeological circum- Mining methods are summarised in Table 25 and Figure stances, and will be defined on a progressive basis over 15, and the historical development of coal mining in the the next few years. The effect, in this area, will be that Black Country isillustrated in Figure 14.

65 Figure 18 Generalised development of general subsidence dueto collapse of disused workings. \ \ / \-zone of possible disturbanc 2 \ / \

Early mining was restricted to small pits or shallow ‘bell in the more modern mines such as Sandwell Park, Ham- pits’ which exploited the seams near the outcrop. In order stead and Baggeridge. With this method subsidence gener- to mine the seams at depth, a ‘pillar and stall’ method was ally takes place within ten years of extraction, but even introduced to support the roof of the mine (Plate 2); in then collapse of formerly supported areas such as roadways many mines the supporting pillars of coal were subsequent- may occur. Subsidence takes place as a ‘wave’ as the roof ly mined and the roof allowed to collapse. A new method is allowed to collapse behind the working face; the void is of mining termed ‘square works’ extraction, a precursor to also filled with mine waste created by the mining. Since modern longwall methods, was introduced in the 17th cen- the last deepmines in the BlackCountry closed in the tury and was adopted by many though not all collieries. In 1960’s, it is assumed that subsidence has ceased from the this method the whole of a long face of coal was extracted most recent longwall mines. Although the amountof subsi- in front of gate roads which servicedthe face; the roof was denceis largely predictable, thepresence of geological allowed to collapse behindthe working face (Plate 3). faults may cause differential subsidence, particularly where Subsidence induced by longwall mining can to a great coal has been extracted only from the upthrow side of the extent be predicted, but accurate prediction of subsidence fault. Geological faults are usually shown as a line on the and ground movementsresulting from the collapse of older map, but in reality, many faults are not single planes, but mineswhich employed pillar and stall orsquare work consist of a series of closely spaced, sub-parallel disconti- methods are unpredictable, due to the collapse of voids and nuities forminga fault zone upto tens of metreswide. the crushing of supporting pillars. Surface instability and Other factors affecting subsidence include the dip of the subsidence is largely a function of the thickness and width seam, method of waste stowage, the nature and structure of of the mined seam andthe depth of the workings. In gener- the overlying strata (including superficial deposits), and al, the greater the depth of workings the more the effects of surface topography. Settlement in a deep seam my trigger subsidence will be attenuated through overlying strata, so further settlement in higher seams. that the effect at surface will be less, although it will extend Prior to developing a site, the developer should inform over a wider surfacearea. The effects of subsidence are not British Coal of the proposals, particularly in relation to restricted to the area above the workings, but, on average, foundation design, at the local Group Headquarters respon- extend at an angle from the edge of the workings and the sible for deep mines (Appendix3). ground surface of about 35 degrees from the vertical, in a Bell pits (Figure 15) were used until the 17th century, sub-horizontal seam (Figure 18). largely in areas where the seams crop out with low dips, The surface stability in undermined areas is partly de- and in areas where the overlying superficial deposits are pendant on the method of mining (Figure 15; Table 25). thin. Many pits were not backfilled and they were left to Old, shallow worlungs at less than 50 m below rockhead collapse naturally after abandonment. Consequently the fill are the most significant in terms of surface stability, but material may have a low bearingcapacity. Areas of former worlungs at greater depths may occasionally produce sur- bell pits may be characterised by the presence of low cones face subsidence. The weightof new buildings, as a result of of waste material and/or shallow depressions along theline redevelopment of a site, may affect the ground stability, of the outcrop of the seam. particularly where the workings are near the surface. Fur- Pillar and stall methods (Figure 15) replaced bell pits thermore, the subsidence may bemigrating upwards to- in the 16th and 17th centuries; access to the mine was ei- wards the surface from old workings. ther by adit or vertical shaft. The roof was supported by Subsidence is assumed to have taken place soon after unworked pillars of coal, but after initial extraction, the mining where longwall methods (Figure 15) were used, as pillars were subsequently ‘robbed’ as the mined area was

66 Table25 Summary of types TYPE OF MINING AREA METHOD PROBLEMS FOR LAND USE and methods of coal mining and (Periodused) associated problems for land use Crop workings Exposed Direct working 1. Very shallow workings. (Middle Ages coalfield of coal at 2. Line of subsidence and earlier) surface. along the crop.

Bell pits (Middle ages & Exposed Shaft c. 1.25 I. Risk of voids remaining. 16th century) coalfield diameter up to 2. Shaft sites poorly known. 12 m deep: 3. Shaft infilling variable radial working and doubtfully compacted. to 10 m from shaft.

Pillar and Exposed Coal cut along 1. Up to 60% coal may be left, stall coalfield grid of roads so site investigation may (from 15th to with not detect worlung. 17th century) rectangular 2. Overlying beds of high pillars left strength (such as for support. sandstones) may have resisted collapse leaving large voids. 3. Collapse may result in cavities and breccia pipes in rock above; or in crown holes, at surface. 4. Shaft sites poorly known. 5. Shafts variably backfilled and doubtfully compacted.

Panel working Progressively Coal extracted 1. Collapse of face underground and longwall deeper along produces subsidence and (from 18th workings continuous lowering of ground surface. century) from coalface (up Effects usually immediate colleries to 200 m wide). and assumed to be largely on, and Temporary over within a few years. later to support of 2. Differential subsidence along east and roof then faults at surface can lead west of, collapse of to severe damage. exposed all except 3. Variable backfilling and coalfield. lateral capping procedures applied roadways. to shafts.

Opencast Scattered Excavation of 1. Compaction may be incomplete, mining localities pit, extraction locally, on older sites. (from 1940) in exposed of coals, 2. Differential settlement coalfield. backfill with possible along sides of spoil; former workings. restoration of 3. Natural drainage altered. site. abandoned. Weakening of the pillars induced haphazard ing the mining of coal, and may migrate along geological roof collapse. Subsidence is, therefore erratic and unpre- faults, shafts, and adits, or be present in old bell-pits. The dictable, and may take place as a result of floor heave, gases may also migrate through permeable strata, within crushing of pillarsor roof collapse (Healy and Head, pore spaces or as dissolved gases in water. Rising ground- 1989). Voids left after mining may be subjectto roof col- water table may pressurise the gas in the voids and causeit lapse. In some cases the void is filled by the roof materi- to migrate to higher levels. al which is subjectto an increase in its bulk; in others the void may propagate upwards until it meets a competent Documentation of mined ground stratum such as a strong sandstone. In extreme cases the The most serious problem associated with former workings void will continue to generate towards the ground surface is poor documentation. The 1872 Coal Mines Regulation to form a crown hole (Figure 19). Crown holes are un- Act stipulated that accurate plans be lodged with the Mines usualabove coal mines deeper than 70m (Healyand Inspectorate, but prior to this date only the larger mines Head, 1989). It is not possible to predict this type of col- were documented. Similarlythe position of many of the as- lapse. sociated shafts, bell pits and adits are poorly recorded and may remain open below a near-surface capping. The out- Mine Gases line of abandonedcolliery-based workings is shown on Dangerous gases such as methane, carbon dioxide and car- Maps 6A, 6B. It should be noted, however,that the bound- bonmonoxide may accumulate in anyvoids remaining aries are generalised and approximate, and that unrecorded after collapse of workings. These gases are generated dur- former workings may occur at shallow depths; commonly

67 Figure 19 Diagramaticdevel- opment of miningvoids and soil overburden &\\\\\x\\\---’ crown holes.

weak thinly bedded shales and mudstones

massive sandstone

limestone roof rock en

crown hole

soil overburden

more than one seam has been worked withinthe demarcat- Head, 1989), and the DOE publication ‘Treatment of Dis- ed area. The sites of known shafts and adits are also shown used Mine Openings’(7/1/223). on Maps 6A, 6B; other unrecorded shafts and adits may exist. Where the site of a shaft is uncertain, two sites may Spoil tips be shown. Responsibility for locating shafts, adits and un- Coalmining produces large amounts of waste material; dermined areas lies with the site owner or developer. The someis used to backfill theworkings but considerable data have been taken from British Coal and BGS records, amounts remain as waste tips. Much of the waste produced which maybe incomplete.Records of shafts andaban- during early mining operations in the Black Country was donedmines are lodged with the British Coal Mines spread evenly over the land surface as constructional made Records Office, Bretby (see Appendix 3), who should be ground. However, some of the more recently worked pits, consulted for detailed information prior to the development particularlythose in theconcealed coalfield, have tip of any site. Additional records may be held by the Building mounds. The possibility of exploiting this material is con- Control Officer or Structural Engineer of the appropriate sidered in an earlier section on Mine Stone; otherareas have Metropolitan Borough Council (Appendix3). Guidance for been converted to recreational parkland. The existing tips engineers and planners involved with the planning and de- such as those at Oldnall, Cradley Park and Old Hawne col- velopment of sites previouslyundermined for coal and lieries presenta constraint to development.The tips are otherminerals is given in theCIRIA/DoE publication, steep-sided and composedlargely of compacted shale, poor ‘Construction over abandoned mine workings’ (Healy and quality coal,mudstone, siltstone andsandstone. Internal

68 Table 26 Index of Silurian limestone mines (from strength of the limestone pillars and the roof. Furthermore, Ove Arup & Ptnrs, 1983) the limestone mines wererarely backfilled with mine waste so that the void was left intact. Most of the voids filled with Index Mine Seams Approximate water soon after abandonment; someof those in the Dudley no. name worked depth (m) area remained dry because they lie above the level of the * canal into which they drained. Crushing of the pillars, roof 1 Arboretum L 25 collapse and floor heave contribute to the infilling of the 2 Bentley U&L 120 & 165 voids through time. The sudden collapse of the roof may 3 Birchills U&L 140 cause upward migration of the void as a chimney shaped 4 Blackham U&L 120 & 165 conduit, until the surface is reached when a crown hole is 5 Castle Hill U&L 10 to 30 6 Coneygre U 200 formed (Figure 19). A well publicised crown hole devel- 7 Cow Pasture U 155 oped in the middle of Dudley cricket ground, above part of 8 Darlaston Green U 200 theabandoned Castlefields Mine, in 1985;no injury or 10 Dudley Port, damage to constructions was caused. Ensells U 175 The generation of crown holes is unpredictable, and a 11 Dudley Port, cautious approach to development of such sites is required. D&B U 225 Development or redevelopment should be conditional on 12a East Castle U&L 15 & 25 site investigations establishing the extent of former work- 12b Castlemill U&L 15 to 90 ings and whether voidsare present. General subsidence oc- 12c Castlefields U 30 to 100 curs where the roof collapses but the chimneys do not mi- 13 Dudley Port, grate up to surface level, oftendue to thepresence of Giles U 190 14 Grovelands U 195 strong competent strata above the void which prevents fur- 15 Hay Head BL 20 ther upward passage (Figure 19). In 1978 substantial subsi- 16 Hay Head dence over a cavern, at depth, resulted in damage to indus- (3 Crowns) BL 20 trial buildings in Sandwell. Where a large area of the mine 17 Hurst Hill U&L variable roof collapses in this manner,a conical shaped zone of 18 James Adams L? 50 to 90 general subsidence may occur above, and outwards, from 19 James Bridge U 200? the area of collapse in a manner similar to coal-mining in- 21 Littleton Street L 55 to 70 ducedsubsidence (Figure 18). The Ove Arup study has 22 Mons Hill U&L 15 to 30 shown that about 100 collapses have beensufficiently large 23 Moss Close L 10 to 50? to generate identifiable surface disturbances. Since the last 24 Peal Street L? 1O? 25 Pennant Hill U&L 125 mine was abandoned in 1935, the number of surface distur- 26 Springhouse BL 335 bances has continued at a steady rate of about one distur- 27 Tividale U 190 bance every 1.5 years. About two thirds of the identified 28 Trough Pits U 195 surface disturbances occurred above mines wherethe depth 29 Wolverhampton of the roof is less than 30 m. General subsidence, in con- st U&L 70 & 100 trast to crownhole development, is largely restricted to 30 Wren's Nest U&L 10 to 70 mines deeper than 70m, and theis only form of disturbance 31 Yew Tree U&L 220 & 260 noted in mines deeper than 100 m. - Although many of the mines were poorly documented, U = Upper Quarried Limestone recent studies (Ove Arup and Partners, 1983) have locat- L = Lower Quarried Limestone BL= Barr Limestone ed, mapped and recorded the sites of most of the former mines in the Black Country. Records and updated appen- dices of this study are held by the relevant Metropolitan drainage can be expected to be poor, and combustion of Borough Council. The outlines of currently known lime- contained fragmentary coal could take place leadingto heat stonemines are shown on Maps 6A, 6B; the depths of generation and subsidence. Furthermore,the waste tips may workings and seam, or seams, worked are given in Table generate noxious gases suchas methane and carbon dioxide 26. In view of the potential for subsidence or crown hole if drainage conditions withinthe tip material are poor. developmentin undermined areas, they require careful archival, geological and geotechnical investigations. Site Underground limestone mining investigation boreholes may penetrate pillars leading to Underground mining of Silurian limestone is considered in an underestimation of the extent of former workings. The the section on mineral resources. The constraints placed on Ove Arup study has shown that the principal factors to be planning and development of undermined limestone areas taken into account in assessing relative risk of an under- are similar to those outlined in the section on coal andcol- minedarea are: the geology (sequence of strata),the liery-based mining. The areas of known underground lime- depth,the layout, and the age of themine. They have stone mines are shown on Maps 6A, 6B.As with coal min- drawn up consideration zones around the known mines ing the principal risk is subsidence dueto collapse of voids. and assessed the relative risk of collapse for each mine. There are special factorsassociated with the limestone Recommendations for methods of monitoring, site inves- mines which affect surface stability (Ove Arup & Partners, tigation and remedial work to be undertaken in the treat- 1983). The limestonewas mined by pillar and stall methods, ment of the mine are also outlined in the report; guidance but in areas of steeply dipping strata elongate galleries were is also given on the structural design of buildings to with- produced with sub-horizontal floors and pillars orientated at stand ground disturbance. It should be pointed outthat the right angles to the steeply dipping roof of the mine (back overall relative risk is low since only 12 of the 100 or so cover). In general, thickness of the extracted material was disturbances have caused damage to propertyand there greater and the proportion of void to pillar was much larger has been no loss of life attributable to the surface distur- than in thecoal mines, due to thegreater mechanical bances; the area affected by surface disturbance is about

69 12 acres, a small fraction of the total undermined area. may be present either as a primary componentof the fill, or Experimentalstudies designed to monitor incipient col- generated by secondarychemical or biological reactions lapse of abandoned mines have been carried out using mi- within the fill. These can migrate within the fill or into ad- croseismictechniques (Miller et al., 1987;1989). These jacent permeable strata, either within the pore spaces of the techniques may have an application in detecting roof falls surrounding deposit or along joints, fractures and faults. in air-filled andflooded abandoned mines, in order to Landfill sites situated on the Sherwood Sandstone aquifer give warning of surface or near-surface disturbance, such or Glaciofluvial and alluvial sands and gravels cause par- as crown hole development, which may result from pro- ticular risks, especially if the site is in hydraulic continuity gressive collapse. Other methods of monitoring, applica- with the aquifer. In a similar manner gases generated with- ble to mines deeper than 70m, comprise optical level sur- in the fill can migratelaterally or vertically, and may accu- veysand horizontal strain measurements of theground mulate within buildings or voids suchas tunnels or excava- surfaceabove a mine; these methods may detect strain tionsnearby or at some distance away. Migration of dueto subsidence caused byroof collapse,at depth. methane from a landfill site at Loscoe, Derbyshire resulted Changes in the condition of open mines can also be moni- in explosion at some distance from thelandfill site (Aitken- tored, in some cases, by visual inspection (near-surface, head and Williams, 1987). accessible mines) and by remote cameras lowered down Siteswith known high levels of methanegeneration boreholes (deep, inaccessible mines). should be carefully managed and monitored so that the gas Themost feasible engineering solutions recommended is drained or vented off by controlled collection or flaring. for treatmentof the mines are: The risk of lateral and vertical migration of landfill gases (a) infillingthe voids by injectinggrout comprising and associated leachates can be reduced by the installation gravel, sand, pulverised fuel ash (pfa) or colliery waste, to- of impervious membranes betweenthe landfill material and getherwith cement in variousproportions. The injected the rock face, and/or betweenthe fill material an any over- material should spread outin the voids and thereby prevent lyingconstruction. Underground spaces in buildings on block-falls from the roof and spalling from the pillars, so methane-bearing ground should be positively ventilated. In that further collapse is largely eliminated and void migra- the latter case the fill material should be vented to release tion minimised or prevented. This will improve the stabili- any trapped gases in order to prevent build upof gas. If the ty of the overlying strata. landfill site is well managed the methane generated can be (b) bulk excavation and controlledbackfilling of shallow utilised to provide a local source of fuel. worlungs. Guidelines for the control and treatment of landfill sites (c) additional design measures may be incorporated into are set out in Department of the Environment publications the design of the buildings above the areaof risk. such as circulars 21/87and 17/89, ICRLGuidance Note 17/78 and HMIP Waste Management Paper27. Quarries and pits Surface extraction of minerals is restricted to smalland Constructional landfill and tips medium sized pits and quarries; although large-scale exca- This category comprises fill that is deposited on the origi- vations are created by opencast coal mining, the sites are nal land surface; it may be spread out to form a generalrise short-lived and are backfilled and the land reclaimed soon in the land surface levels (sometimes as componsation for after extraction. Many of the pits and quarries have been subsidence), dumped as more obtrusive colliery waste tips backfilled, others partially filled anddegraded, some are (p.67), or used as constructional material for embankments. flooded while others remain open. Former excavationspre- Theareas of constructionalmade ground are shownon sent constraints to development related to: Maps 4A, 4B. In general, the older parts of the exposed (a) geotechnical problems of variable fill types and vari- coalfield, such as the Tipton, Wolverhampton, Darlaston, able ground conditions such as drainage between the natu- and Willenhall areas are covered by made ground between ral surface andthe fill, and variable compactionof the fill, 1 and 10 m thick, and locally it is up to 20 m thick. Else- (b) properties and nature of the fill material and any risks where it is more local in its occurrence and often formsdis- associated with the migration of gases (such as methane or tinctive landforms. carbon dioxide) orleachates, from the fill to the atmosphere Constraints to development occur where the fill is com- or into the surrounding bedrock orsuperficial deposit, posed of materials of low bearing strength or high com- (c) risk of failure of steep slopes created within the exca- pressibility, and in areas where the material has not been vation. sufficientlycompacted. Organic waste may generate A knowledge of the extent and type of former excava- methane or other noxiousgases, and toxic leachate residues tions can resolve many of the problems for development. may be present. Artificially steep slopes on embankments Former pits and quarries are shown on Maps 4A, 4B; they and at the edges of constructional landfill sites may be sub- have been sited using archival geological and topographi- ject to slope failure, especially in areas of poorly managed cal maps, but other excavations no doubt exist. In some groundwaterflow or poorly compacted material. Low- cases the boundaries of the excavations are approximate. lying sites such as the Tame Valley were prone to flooding Thorough site investigations should be carried out in areas prior to tippingand the construction of artificial levees. of known or suspected backfilled workings. Table 14 sum- Settlement of alluvial deposits such as clay, peat and or- marises the types of former excavation, their distribution ganic rich soils, beneath a cover of fill, may lead to rising and the problems theymay pose for development. water table within the fill material and the generation of methanefrom organic material due to biodegradation in Landfill anaeorobic conditions. Superficial materials such as Head The use of quarries and pits for landfill waste disposal may or soil, below the fill deposits, may forma weak layer present a hazard from the generation of noxious or explo- which could act as a zone of potential failure if overloaded sive gases such as methane, carbon monoxide and carbon by constructionon the stronger fill, or act as azone of dioxide (p.64), and toxic leachates. Liquid toxic residues shear failure if the fill has been placed on slope.a

70 GLOSSARY EXPOSURE An area of a rockunit that is unobscured by soil or othermaterials. ADIT Horizontal or low angle (walkable) entranceinto a FAULT A fracture in rock along which displacement of mine. one side relative to the other has takenplace. AEOLIAN DEPOSITS Sediments depositedafter transport FAUNA Animalsof a region or periodcollectively. by wind. FELDSPAR A rock-forming mineral composedof silicon, AGGLOMERATE Volcanic rocks consistingof fragmental aluminium, oxygen and variable amountsof potassium, volcanic and/or sedimentary material which have been sodium and calcium. formed by explosive activity within a volcanic system. FIRECLAY A fossil soil commonly foundin association Clasts are generally greater than 2 centimetres in diameter. with coal seams.It is especially useful as arefractory min- AIRFALL TUFF Consolidated,subaerially deposited vol- eral. canic ash. FLOODPLAIN Atract of land bordering ariver, mainly in ALLUVIAL FAN A massof sediment depositedat a point its lower reaches, and consistingof alluvium depositedby where there is a decreasein gradient e.g. from a mountain the river. to a plain. FLUVIAL Of or pertainingto a river. ANGLIAN Apart of the Pleistocene epoch dating from ap- FOSSIL An organictrace buried by natural processes, and proximately 0.38-0.45 Ma and representing a periodof subsequently permanently preserved. glaciation over muchof England. FRACTURE SPACING INDEX A measureof the average ANTICLINE A rockstructure in which beds are folded length of intact rock core pieces. The unit length is divided convexly upwards. by the number of fractures within the unit. AQUICLUDE A bodyof relatively impermeable rockthat FORMATION Distinctiveunit of sedimentary rock with does notreadily transmit water. defined and mappable boundaries, AQUIFER A bodyof rock that is sufficiently permeable to GLACIAL Of or relating to the presence of ice orglaciers; yield groundwaterto boreholes, wells andsprings. formed as result of glaciation. BEDDING The arrangementof sedimentary rocksin beds GROUP A stratigraphical unit usually comprising one or or layers of varying thickness andcharacter. more FORMATIONS withsimilar or linkingcharacteris- BEDROCK Unweathered rock beneaththe soil or DRIFT tics. cover. GROUNDWATER Water containedin saturated soil or BIOCLASTIC Term appliedto sediments madeof broken rock below the watertable. fragments of organic skeletal material. HEAD An earthy deposit containing angular fragments BONE BED A sedimentary layer characterisedby a high produced as a result of SOLIFLUCTION in proportion of fossil bones, scales and teeth. PERIGLACIAL regions. BOULDER CLAYAn alternative name for TILL. INLIER A limited areaof older rocks completely surround- BRECCIA A rock consisting mainlyof angular pebbles ed by younger rocks. It may be produced by erosion, fault- implying minimumtransport. ing or folding. CALICHE A fossil soil characterised by concentrations of INTERGLACIAL Ice agesare often divisible into periods calcium carbonate commonlyin the form of nodules. The of maximum advance and periodsof ice retreat. A period soil formation is commonly associatedwith an arid to of retreat is referred to as an INTERGLACIAL. semi-arid climate. JOINT A fracture in a rock betweenthe sides of which CHERT A rock composedentirely of silica with no visible there is no observablerelative movement. crystalline structure. LACUSTRINE Pertainingto lakes. CONGLOMERATE A rock consistingof rounded frag- LAMINATED Descriptionof very thin bedding less than ments implyingrather more transport than a breccia. 10 millimetres thick. CROSS-BEDDING Aseries of inclined bedding planes LEVEE Raised embankmentof a river, showing a gentle having somerelation to the direction of current flow. slope away from the channel.May be natural or man-made. CRYSTALLINE Composedof crystals. LITHOLOGY The characteristics of a rock suchas colour, CUESTA A hill or ridge with a a gentle slope (DIP- grain size and mineralogy. SLOPE) on oneside and a steep slope (ESCARPMENT) LIQUID LIMIT The moisture contentat the point between on the other. the liquid and theplastic state of a clay. DEVENSIAN A geological succession dating from ap- LOPOLITH Concordant igneousintrusion that has a sag- proximately 0.12-0.10 Ma (part of the Pleistocene epoch) ging, saucer-like form. and representing a periodof glaciation which partly cov- MARINE TRANSGRESSION Arelative rise in sea level ered England. which results in the invasionof a large area of land by the DIP-SLOPE The generally gentle slope which conforms sea. closely to the dip of the underlying strata: marking one side MARINE REGRESSION Arelative fall in sea level result- of a cuesta. ing in the withdrawalof the sea from a large areaof land. DOLERITE A medium-grainedintrusive basic igneous MARL A calcareous mudstone containing35-65% cal rock. cium carbonate. DYKE A sheet-like igneous body which cuts across bed- MARLING The incorporationof calcareous mudstoneinto ding. the soil as a formof mineral enrichment. The‘marl’ was ESCARPMENT The slope marking the steepside of usually locally quarried from suitable carbonate-rich strata. CUESTA: generally formedby the resistance to erosion of MASSIVE Containing novisible internal structure. a rockunit near thecrest. MEMBER A distinctive, defined unit of strata within a for- ESPLEY A local mining and quarrying term appliedto mation. greenish coarse-grained, often pebbly sandstones presentin METHANE A colourless, odourless, inflammable gas the Etruria Formation. (CH4); forms an explosive mixture withair.

71 NORMALLY CONSOLIDATED Normally consolidated derground mining, clay shrinkage or responseto overbur- deposit, such as clay, that is compacted by exactly the den. amount to be expected from the pressure exertedby the SUPERFICIAL DEPOSIT A general term foran unconsol- overburden. idated depositof QUATERNARY age overlying bedrock. OROGENY A periodof mountain building. STANDARD PENETRATION TEST (SPT)An in-situ test OUTCROP The area over whichparticular a rock unit oc- for soil where the number of blows (N) with a standard curs at the surface, whether exposed ornot. weight falling through a standard distanceto drive a stan- OVERCONSOLIDATED Overconsolidateddeposit, such dard cone or sample tube set a distance is counted. A mea- as clay, that in previous geological times was loaded more sure of the bearing capacityof a soil. heavily thannow and consequently has a tendencyto ex- SYNCLINE A rockstructure in which beds are folded con- pand if it has accesss to water. cavely upwards. PERIGLACIAL Saidof an environment beyond the pe- SYNSEDIMENTARY Occurring simultaneously with sed- riphery of an ice sheet influencedby severe cold, where imentation ordeposition. permafrost and freeze-thaw conditionsare widespread. TILL Unsorted mixtureof clay, silt, sand, gravel and boul- PERMEABILITY The property or capacityof a rock, sedi- ders deposited from melting ice without subsequentre- ment or soil for transmitting afluid. working by meltwater. PLASTICITY INDEX The difference betweenthe water UNCONFORMITY A substantial break in astratigraphic contents of a clay at theliquid and at the plastic limits. It sequence where strata are missing. There may be an angu- shows the rangeof water contents for whichthe clay is lar relationship between the strata above and below thesur- plastic. face of unconfonnity. PLASTIC LIMIT The water contentat the lower limit of VEIN A mineral orlithic infilling of a fault or otherfrac- the plastic state of a clay. It is the minimum water content ture in a rock: usually sheet-like or tabular. at which a soil can be rolled into a thread 3mm in diameter WASHOUT A coal mining termused to describe a channel without crumbling. cut into strata (usually coal) subsequently filled by sedi- POINT LOAD TEST Indextest to give an indicationof ment such as sand or silt. strength; usually carried out on rockcore. PLUNGE The angle between theaxis of a fold (ANTI- CLINE or SYNCLINE) andthe horizontal. ACKNOWLEDGEMENTS PYRITE The most widespread sulphide mineral, FeS2. QUARTZITE A sandstone rich in quartz grains - usually We acknowledge the kind assistance of the local landown- over 75%. ers, tennants, quarryoperators and councils in permiting RIVER TERRACE Approximately planar surfacein a val- access to their lands and undertakings. We thank all the ley above the present river level, representing the dissected local authorities, geological and geotechnical consultants, remnants of an abandoned floodplain produced during a private companies and other organisations, such as British former stageof deposition. Coal, British Rail and the National Rivers Authorty, who ROCK QUALITY DESIGNATION (RQD) The percent- supplied us with borehole and trial pit data (Appendix 1). age of constant diameter core>lOOmm in length recovered Weacknowledge the assistance and constructive com- in a single core run. An indication of the fracture state of ments, throughout the project, provided by the members of the rock mass. the Steering Committee. SEATEARTH A typeof fossil soil commonly found inas- sociation with coal. Thanks go to Rebecca Dann, Matthew Frost, Mark Maw- SILL Asheet-like body of igneous rock which conformsto sonand Chistopher McMurray who collected and sited bedding or otherstructural planes. much of the borehole data, and who assisted at various SOLIFLUCTION The slow, viscous downslope flowof stages of the project. We are grateful to Keith Holmes for waterlogged surfacematerial, especially over frozen helpand advice on computer methods, and to Maureen ground. Ritchie for information onseismicity. SPIRORBIS A small worm-like(annelid) fossil occasion- ally found in strata deposited in fresh water e.g. limestones Finally, we would like to acknowledge the advice, com- of the Keele and Halesowen Formation. ment and support given by Drs. D Brook and B R Marker Genus: Spirorbis, Order: Tubicolar Annelides. of the Department of the Environment throughout the study SUBSIDENCE Thesettling of the ground or a building in and inthe compilation of the report. response to physical changes inthe subsurface suchas un-

72 TECHNICAL APPENDICES logue consistingof a site map at 1: 10 560 or1 : 10 000-scale and a borehole register, together withthe individual records. The sheet numbers includedin this study and the Appendix 1 DataSources numbers of boreholes in each catalogueare listed below: Borehole Data Sources of borehole data collected duringthis study are listed below. Those marked with anasterisk * are major Sheet No. Boreholes Total sources: registered number (a) Public authorities before this of *Birmingham City Council,Industrial Research Laborato- study registered ries boreholes *Dudley MBC S088NE Kingswinford 69 382 *Sandwell S088SE Stourbridge 48 209 *Walsall MBC S089NE Penn 41 207 *Wolverhampton S089SE Wombourne 46 180 (b) Private companies including consultants and nation- S098NE Rowley Regis 34 4 1628 alised industries S098NW Brierley Hill 56 41639 ARC Ltd S098SE Halesowen 16 1367 Applied Geology Ltd SO98SW Lye 14 054 1 Ascough & Associates S099NE Willenhall and Baggeridge Brick PLC Darlaston 1968 2538 Baynham Meikle Partnership S099NW Wolverhampton 859 1185 Hobson Associates S099SE Dudley and British Coal Opencast Executive Wednesbury 737 3300 British Geotechnical SO99SW Dudley and *British Railways Board Sedgley 673 1526 Burne Associates SP08NW Smethwick 146 653 Bryant Homes Ltd SPO8SW Harborne 79 273 Cameron Taylor Partners SP09NW Walsall 410 930 Bylander Waddell Partners Ltd SPO9SW Hamstead 344 790 Cooper MacDonald& Partners Clayton, Bostock,16,348Hill & Rigley 6629 Totals S M Cooper and Associates Douglas Technical Services Mine Plans Exploration Associates Fairclough Civil Engineering Ltd Coal, ironstone andfireclay *Geotechnics Ltd Copies of all known colliery abandonment plans, together with G K N Keller Foundations many of the abandonment plansof the Silurian limestone Griffin Mellors & Associates mines, are held by the Mining Records Officer, British Coal, *Ground Exploration Ltd Technical Services and Research Executive, Bretby, Stafford- *Ground Investigation& Piling shire; the original plans are housed at Staffordshire House, Stoke on Trent. Abandonment plans are byheld British Coal in Groundworks (Dudley)- now J.P. & B. Ian Farmer Associates the public domain, but are not avadable for reference at BGS. M & J Drilling Services *Johnson, Poole& Bloomer Silurian limestone Keith Palmer Associates In addition to the abandonment plansof Silurian limestone L V Ingram & Partners mines heldby British Coal, noted above, an up to date register McCarthy & Stone (Development) Ltd of all the known limestone mines and approximate outlinesof Norwest Holst Soil Engineering Ltd the workings are heldby the Building Control Officerof the *Ove Arup & Partners relevant Metropolitan District Council. Parkman Consulting Engineers For WolverhamptonMBC, mines other than coal and lime- Redland Bricks stone are held at the Central Library, Wolverhampton. "Rendel Geotechnics Ltd Robinson James Partnership Ltd Hydrogeology *Sir Alexander Gibb& Partners Hydrogeological data heldby the National Rivers Authority Soils & Materials Testing consist of: Strata Survey Ltd (a) A data bankof all licensed wells, boreholes and springs. Structural Design Partnership These data give the permitted ratesof abstraction, the specific *Subsoil Surveys Ltd location and the depth and diameterof the wellor borehole. Geo-Research Ltd Abstraction data are confidential where they relate to individu- Tarmac Roadstone (Western) Ltd al industrial users. T & L Explorations Ltd (b) A data bankof groundwater chemistry relating allto pub- "Wardell Armstrong Ltd lic water supply sources and a few selected industrial sources. Wimpey Homes Ltd (c) Limited data on long-term changes in groundwater levels. The borehole dataare catalogued in the BGS archivesat Similar dataare held by the Hydrogeology Group, BritishGe- Keyworth on individual 1: 10 000-scalesheets, each cata- ological Survey, Wallingford.

73 Appendix 2. List of Mineral Industry Operators (1992) Appendix 3. List of statutory bodies relevant to planning and development 1. Brick Clay Baggeridge Brick, Baggeridge Wood Quarry[SO 1. Coal 899 9111, Fir Street, Gospal End, Sedgeley, British Coal* DY3 4AA Technical Services and Research Executive, Hinton, Perry and DavenhillLtd., Ketley Quarry Bretby, Staffordshire DE15OQD [SO 897 8891 Dreadnought Works, Pensnett, Brierley Hill, DY5 4TH British Coal** Ibstock Brick, Himley Quarry[SO 897 9021 Group Surveyor & Minerals Manager Pensnett TradingEstate, Stallings Lane, Midlands and Wales Group Kmgswinford, Dudley. Beaumont House Redland Bricks Ltd., Stourbridge Brickworks [SO Coleorton 910 8981 Tansey Green Road, Kingswinford, Leicestershire LE6 4FA Brierley Hill, DY6 7LS *Responsible for plansof abandoned mine workings 2. Dolerite aggregate and coated stone **Responsible for deep mines ARC-Western, Edwin Richards Quarry [9698831 Portway Road, Rowley Regis, Warley, British Coal Opencast Executive B65 9DN Staffordshire House Tarmac-Western, Hailstone Quarry, [9688791 Berry Hill Road Portway Road, Rowley Regis, Warley, Stoke on Trent Staffordshire ST4 2NH B65 9DW Responsible for current andfuture opencast mining 3. Coal Opencast Executive,British Coal, Staffordshire 2. Planning and development House, Stoke onTrent, Staffordshire. Former Dudley Metropolitan Borough Council recent workings at Bilston, Dibdale Road and 3 St James Road Patent Shaft sites. Dudley West Midlands DY1 1HZ 4. Sand and Gravel, and sand-rock Davies, F. & Sons Ltd., Enville Road Quarry[SO Sandwell Metropolitan Borough Council 873 8991 Enville Road, Wall Heath, West Wigmore Buildings Midlands Pennyhill Lane Element, T., Stewpony Quarry [SO 865 8451 (east West Bromwich B71 3RZ of study area)HalesowenStreet, Oldbury, Warley Wolverhampton Metropolitan Borough Council D J Shakespeare, Highdown Quarry [8798161, Civic Centre (Sherwood Sandstone)16 Oak Lane, BrierleyHill, West Saint Peter’s Square Midlands Wolverhampton WV1 1RG Walsall Metropolitan Borough Council Darwall Street Walsall WS1 1TW

Birmingham City Council Baskerville House Broad Street Birmingham B1 2M0

Black Country Development Corporation Black Country House Rounds Green Road Oldbury West Midlands B69 2DG

3. Groundwater supply and sewage disposal National Rivers Authority Severn Trent Region Abselon House 2297 Coventry Road Sheldon Birmingham B26 3PU

All applications forlicences to drill and test pump bore- holes for water should besent to the above address and not to BGS.

74 4. Geology Appendix 4. List of 1: 10 000-scale geological maps and Various Actsof Parliament ensurethat information ob- accompanying technical reports tained from the sinkingof boreholes andshafts for miner- als , including petroleum, and for water, is madeavailable Each component 1: 10 000-scale map in the study area has to the British Geological Survey. an equivalent Technical Report describing the geology of The following operations must benotified in writing to the the sheet, including generalised logs of selected boreholes British Geological Survey: and shafts held in the BGS archives. Copies of these re- The sinking of a new borehole or shaft to a depthof more ports may be ordered from BGS, Keyworth, Nottingham, than 30 m (15 m for water),or the deepening of an existing NG12 5GG. Thereports and authors are listed below: borehole or shaft to a depthof greater than 30 m (15 m for water). Sheet no. SheetnameTechnical Author Any person carrying out these operationsis also required report no. to: S088NE Kingswinford WN91/39 Waters C N (a)Keep a recordof the nature and depthof the strata en- S088SE StourbridgeWA/91/70 Powell J H countered, S089NE Penn WN91/76 Powell J H (b)Retain specimens of cores and chippingsfor examina- S089SE WombourneWA/90/76 Glover B W tion, S098NE RowleyRegis WA/91/55 Waters C N (c) Allow properly authorised oficersof the British Geo- S098NW BrierleyHill WN91/62 Wilson D logical Surveyfree access to specimens and records. and Waters In addition BGSwill be pleased to receive recordsof shal- CN low boreholes andtrial pits for the area. These records are S098SE WA/90/74Halesowen Glover B W sited on 1: 10 000 scale maps and archivedat BGS, Key- SO98SW Lye WN91/59 Powell J H worth. The dataare used to update the geological database S099NE WA/91/78Willenhall Hamblin and geological mapsof the area. Data of a commercial na- and Darlaston RJO, ture can be held ‘commercialin confidence’. Henson For minerals andsite investigation boreholes, written no- M R,Powell tices should be sent to: JH The Manager S099NW Wolverhampton WN91/77 Hamblin National Geosciences Data Centre RJOand British Geological Survey Powell J H Keyworth S099SE Dudley and Nottingham NG 12 5GG Wednesbury WA/91/73Hamblin RJOand For water, writtennotification should be sent to: Glover B W The Manager so99sw Dudley and Hydrogeology Research Group Sedgley WN91/72 Hamblin British Geological Survey RJOand Maclean Building Glover B W Crowmarsh Gifford SP08NW Smethwick WA/91/71Powell J H Wallingford OX10 8BB SPOSSW Harborne WA/90/75Glover BW SP09NW Walsall WN91/63 Hamblin 5. Geological conservation R J 0, Henson English Nature M R, and Northminster House Waters C N Peterborough PE1 1UA SPO9SW Hamstead WN91/08 Waters CN

Black Country Geological Society Honorary Secretary 16 St Nicolas Gardens Kings Norton Birmingham B38 8TW

Keeper of Geology Dudley Museum-and Art Gallery St James’ Road Dudley DY1 1HU

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