A5 Western Transport Corridor
Section 3: South of Omagh to Aughnacloy
Geotechnical Preliminary Sources Study Report (GW163)
796036/0600/R/007A
9th June 2009
Produced for DRD Roads Service (Western Division)
Prepared by Marguerite Rea Geotechnical Engineer
Mouchel Geotechnics Shorefield House 30 Kinnegar Drive Holywood County Down BT18 9JQ
028 9042 4117 028 9042 7039 [email protected] www.mouchel.com
Disclaimer This report presents the findings of a Preliminary Sources Study that was undertaken to establish the geotechnical and geo-environmental constraints and potential risks associated with the proposed scheme. This report presents a review of the information obtained during the desk study in accordance with the guidelines that were issued by the Highways Agency (HA) in HD22/08“Managing Geotechnical Risk,” (implemented in Northern Ireland by Roads Service Standard RSPPG_E008). The objective of this report is to cover the geotechnical risks, investigation implications and feasibility of all scheme options.
Mouchel has prepared this report on the basis of the available information received during the study period. Although every realistic effort has been made to obtain all relevant information, all potential contamination, environmental and / or geotechnical constraints or liabilities associated with the site may not necessarily have been revealed. Any interpretation and advice given in this report should be considered preliminary and suitable for planning purposes only. It should not be used for detailed design unless confirmed by a ground investigation.
This report has been prepared and written for the exclusive benefit of the DRD Roads Service for the purpose of providing geotechnical and geo-environmental information relevant to the proposed scheme. The report contents should be only used in that context. Moreover, new information, changed practices or new legislation may necessitate revised interpretation of the report after the date of its submission.
Note on BSEN14688
Soils and rocks in this document have been described in accordance with BSEN1468 and BSEN14689, in accordance with the implementation of Eurocode 7 in the UK with historic site investigation records complying to BS 5930 (1981) and British Standard CP2001 Site Investigations (1957).
Format of Drawings
To aid with the management of the large volume of information gathered and assessment of parameters, drawings referenced throughout this report can be viewed and interrogated electronically within the Arc Reader (GIS) File accompanying this report, on hard drive. Although the referenced drawings can be selected from the navigation pane the reader is however also encouraged to navigate freely around the GIS model and turn layers on and off at will to compare and contrast features. Arc Reader contains the geo-environmental information for the entire scheme. Arc Reader not only presents the information spatially but also provides additional supplementary information about the features shown, either by hovering over and/or clicking on the symbology for the particular geo-environmental feature. General advice on how to use Arc Reader is also contained within Appendix A
796036/0600/R/007A i June 2009 © Mouchel 2009 Contents
1 Introduction ...... 1 1.1 Background ...... 1 1.2 The Scheme...... 1 1.3 Purpose of the Report ...... 6 1.4 Format of the Report ...... 7
2 Sources of Information and Desk Study...... 8 2.1 Sources of Information ...... 8 2.2 Previous Ground Investigations ...... 11
3 Field Studies...... 12 3.1 Drive through Survey ...... 12 3.2 Walkover Survey ...... 12 3.3 Quarry and Landfill Survey...... 12 3.4 Peat Surveys...... 13 3.5 Preferred Route Corridor Survey ...... 13 3.6 Preliminary Ground Investigation...... 13 3.7 Other Field Work ...... 15
4 Site Description...... 16 4.1 General...... 16 4.2 Geography & Topography...... 18 4.3 Land Use ...... 20 4.4 Historical Mapping...... 23 4.5 Aerial Photography...... 23 4.6 Geology...... 25 4.7 Hydrogeology and Groundwater Vulnerability ...... 32 4.8 Hydrology ...... 33 4.9 Other Statutory Consultee Responses ...... 38
5 Ground Conditions ...... 43 5.1 Anticipated Soils...... 43 5.2 Made Ground ...... 45 5.3 Superficial Soils...... 46 5.4 Bedrock ...... 55 5.5 Groundwater...... 56 5.6 Contaminated Land...... 58
796036/0600/R/007A ii June 2009 © Mouchel 2009 6 Preliminary Engineering Assessment ...... 59 6.1 Superficial Soils...... 59 6.2 Cuttings ...... 62 6.3 Embankments ...... 62 6.4 Subgrade...... 63 6.5 Structure Foundations...... 63 6.6 Contaminated Land...... 64 6.7 Soil Chemistry ...... 65 6.8 Other Geotechnical/Man-Made Problems/Obstacles...... 65
7 Comparison of Projects Options and Risks...... 67 7.1 Statement of Preferred Route Options...... 67 7.2 Initial Reduction to Preferred Route...... 69 7.3 Establishment of Geotechnical Risk Register ...... 74 7.4 Geotechnical Classification ...... 75 7.5 Annex A...... 75
8 Figures and Drawings...... 76
9 Geotechnical Certificate ...... 79
Appendices
APPENDIX A: Guidance on Navigating the GIS Data
APPENDIX B: Geological Long Sections
APPENDIX C: Annex A to the Preliminary Sources Study
APPENDIX D: Historical Mapping
APPENDIX E: Water Quality
APPENDIX F: Copies of Statutory Consultee Responses
APPENDIX G: Preliminary Risk Register
796036/0600/R/007A iii June 2009 © Mouchel 2009 Tables
Table 1.1-1 Key Phases under current Commission ...... 1 Table 1.2-1 Engineering Constraints within study area ...... 4 Table 1.2-2 Scheme split and allocated PSS Reports...... 6 Table 2.1-1 Sources of Information...... 8 Table 2.1-2 Statutory Undertakers (Utilities) ...... 10 Table 2.2-1 Summary of Ground Investigation Reports for Section 3: South of Omagh to Aughnacloy...... 11 Table 3.0-1 Drawings showing location of field survey data …………………………….. 12
Table 3.6-1 Summary of Preliminary GI Works ...... 14 Table 4.1-1 Summary of Topographical Zones within Section 3...... 16 Table 4.5-1 Principal Differences between Historical Mapping and Current Aerial Photography ...... 23 Table 4.6-1 Solid geology strata within Sub-Section 3A...... 26 Table 4.6-2 Solid geology strata within Sub-Section 3B...... 27 Table 4.6-3 Solid Geology strata within Section 3C ...... 28 Table 4.6-4 Drift geology of Sub-Section 3A ...... 30 Table 4.6-5 Drift geology of Sub-Section 3B ...... 31 Table 4.6-6 Drift Geology of Sub- Section 3C ...... 32 Table 4.8-1 Principal Watercourses ...... 34 Table 4.8-2 River Classification Scheme ...... 34 Table 4.8-3 Summary of River Pollution Incidents...... 35 Table 4.8-4 Water Abstractions...... 36 Table 4.8-5 Summary of Consented Discharges to Controlled Waters...... 37 Table 4.9-1 Summary of Potentially Contaminated Land Uses within Section 3 with Risk Rating...... 38 Table 4.9-2 The status of Quarries throughout Section 3...... 40 Table 4.9-3 Part A, B and C Industrial Processes ...... 40 Table 4.9-4 Habitas Sites...... 42 Table 5.1-1-1 Summary of Ground Conditions...... 43
796036/0600/R/007A iv June 2009 © Mouchel 2009 Table 5.2-1 Geotechnical properties of Made Ground...... 45 Table 5.3-1 Geotechnical properties of Peat...... 47 Table 5.3-2 Geotechnical properties of River Alluvium...... 49 Table 5.3-3 Geotechnical properties of Glacial Till...... 51 Table 5.3-4 Geotechnical properties of Glaciofluvial Sands and Gravels ...... 55 Table 6.7-1 Potential contamination identified from Industry Profiles ...... 64 Table 6.9-1 Areas of Soil Instability...... 65 Table 7.2-1 Earthwork Volume Totals...... 73 Table 7.2-2 Ranking of Geotechnical issues affecting Route Options ...... 73
796036/0600/R/007A v June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
1 Introduction
1.1 Background The A5 Western Transport Corridor (WTC) is one of the key strategic corridors in Northern Ireland. The A5 extends from Londonderry City, County Londonderry to the village of Aughnacloy in County Tyrone adjacent to the border with the Republic of Ireland. The study area is 88km long, extending from a point just north of New Buildings (S of Londonderry City) to Moy Bridge at the Irish Border as shown on Drawing 796036-0600-D-00061.
Mouchel has been commission by DRD Roads Service to act as client advisor providing technical, project management and design services up to selection of the preferred route option phase for project. The key phases to be completed in the context of the requirements of standards TD37/93 and HD22/08 are summarised below:
Table 1.1-1 Key Phases under current Commission
A5 Commission Stage HD22 (Geotechnical) Activities & TD37 (Scheme Appraisal) Output Output Ph1 – Business. Case & Statement of Intent Initial Constraints Report Corridor Constraints Ph2 – Public Consultation Data Collection Data Collection Ph3 – Options Development - Preliminary Options Report 1 (SAR1) Ph4 – Select Preferred Route Preliminary Sources Study Preferred Option Report 2 Report (SAR2)
The current scope of works also includes the procurement of the detailed ground investigation, though the commission may be extended to provide services to take the road up to and through detailed design, construction, including procurement, preliminary design, orders, detailed design and public inquiry.
1.2 The Scheme 1.2.1 Regional Context The A5 Western Key Transport Corridor scheme which is being delivered through the Regional Strategic Transport Network – Transport Plan (2005) and will become the main north-south route in the west of the province replacing the existing A5. It will provide a strategic link between Dublin, Londonderry and Donegal with links to three cross border routes, feeding into the N2 in the Republic of Ireland at the Moy Bridge border crossing and providing crucial links with both Dublin and Northern Ireland at Strabane-Lifford (A38/N14) and Londonderry (N13).
796036-0600-R-007 1 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Along the existing A5 route within Northern Ireland regional context within the extent of the scheme itself there are strategic links between the urban centres of Londonderry, Strabane, Newtownstewart, Omagh, Ballygawley and Aughnacloy. The A5 connects to the Northern Ireland Strategic Network at the A4/M1 east-west route (Belfast to Enniskillen) in the south of the province and the A6 (Belfast to Londonderry) route in the north of the province. Important links are also made at Omagh with the A32 (Enniskillen - Omagh) and the A505 (Cookstown – Omagh). The regional context of the A5 is shown on Figure 1.2-1 below.
Figure 1.2-1 Regional Context Plan
A5: Extends from Londonderry to Aughnacloy
The scheme involves the upgrade of the A5, from the Irish border at Aughnacloy (H127 412), via Omagh and Strabane to the southern outskirts of Londonderry in the vicinity of New Buildings (H522 667), potentially to dual carriageway standard and either on or off line of the existing road.
Existing local improvements to the A5 include the Strabane and Newtownstewart By- passes and the Omagh Throughpass.
796036-0600-R-007 2 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
1.2.2 Description of the Proposed Works The existing A5 WTC is a ‘patch work’ of differing width single carriageway roads with intermittent stretches of climbing lanes and few overtaking opportunities. In excess of 200 side road junctions currently connect with the A5 with over 420 domestic / commercial accesses, excluding those in the six urban centres along the route.
The 88km route of the current A5 runs through Co. Londonderry and Co. Tyrone as described from north to south below:
Along shelf on steep hillside beside the River Foyle between Londonderry and New Buildings, Along edge of floodplain of (tidal) River Foyle between New Buildings and Strabane, Through Strabane on the line of former railway including a crossing of the Mourne River, Through Victoria Bridge and Sion Mills on the west bank of the Mourne River, Newtownstewart bypass (constructed around 2002) crossing Strule River twice, Along the west bank of Strule River through steep sided narrow valley between Newtownstewart and Mountjoy, A single carriageway “Through-pass” through Omagh on the line of the former railway (not intended to be part of the final works), Following a long north facing slope south of Omagh through moorland and , drumlin terrain closer to Omagh, Climbing a steep ridge along a twisting alignment between Garvaghy and Ballygawley, Roundabout intersection with the A4 at Ballygawley (the northern section of the Ballygawley-Aughnacloy Road is currently being improved to 2+1 standard as part of the A4/A5 improvement DBFO works), Through Aughnacloy, Across a bridge at the River Blackwater at Moy Bridge on the Co. Monaghan border. The intention is to select a route that may comprise on-line dualling of the existing alignment, an off line deviation to the west or east, or a combination of all three of these options as discussed in Section 1.2.3 below.
796036-0600-R-007 3 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
1.2.3 Study Area / Evolution of Preferred Corridor An engineering study area between 10 and 20km wide was initially identified, for consideration of alternative schemes (as shown by the red dashed line in Figure 1.2-2 below and Drawing 796036-0600-D-00061). Three broadly defined improvement strategies were considered within this study area;
• a route to the west of the existing A5,
• an on-line development of the existing A5 and
• a route to the east of the existing A5.
These strategies were further developed into a large number of potentially feasible 1km wide corridors that could improve the local and strategic links. The various corridors were evaluated at a high level on the basis of all likely engineering and environmental constraints, with the key constraints listed in Table 1.2-1 below.
Subsequent elimination of areas based on the engineering and environmental constraints as listed below assisted in narrowing the study area down to a preferred corridor of approximate 2.5km width, either side of the existing A5 for which potential options for the selection of the preferred route emerged as shown in Drawing 796036-0600-D-00061 and discussed further in Chapter 7. As highlighted in Section 1.4 below, Chapters 1-4 will focus information pertaining to the engineering study area whilst Chapter 5 onwards will focus on the preferred route corridor.
Table 1.2-1 Engineering Constraints within study area
Section Engineering / Environmental Constraint Newbuildings to South of Steep terrain in the east, namely Gortmonly Hill and Knockavoe Strabane (Section 1) McKean’s Moss ASSI bog Active sand and gravel extraction sites South of Strabane to South of Development areas of Sion Mills, Victoria Bridge and Omagh Omagh (Section 2) Steep terrain of Bessy Bell to the west Cavancaw gold mine to the west of Omagh Ulster American Folk Park South of Omagh to Aughnacloy Peat at Deroran Bog, Cranny Bog and Tonnagh Bog (Section 3) Sand and gravel extraction sites at Eskragh High ground to the east, namely Slievemore and Slievedivena
796036-0600-R-007 4 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Figure 1.2-2 A5 Western Key Transport Corridor Study Area
Section 3 (South of Omagh to Aughnacloy) – Context of this report
1.2.4 Scheme Split To facilitate the management of the vast quantity of data collected for the study area the 88km scheme has been split into three roughly equal parts referenced as Sections 1, 2 and 3 and shown in Figure 1.2-2. To allow for more detailed review of the information these sections have been further divided into sub-sections.
A separate Preliminary Source Study Report and Annex A has been produced for each Section. The section/subsection extents and the Preliminary Sources Study Report pertaining to each of these are shown in Table 1.2-2.
796036-0600-R-007 5 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
This report will deal specifically with Section 3 - the geographical area south of Omagh to Augnacloy.
Table 1.2-2 Scheme split and allocated PSS Reports
Preliminary Sources Study Section Extents Report Reference:
Section 1 New Buildings to South of Strabane 796036-R-0600-005
Section 1A New Buildings to Cloghcor
Section 1B Cloghcor to North of Strabane
North of Strabane to South of Section 1C Strabane
Section 2 South of Strabane to South of Omagh 796036-R-0600-006
Section 2A South of Strabane to Douglas Bridge
Section 2B Douglas Bridge to South of Mountjoy
Section 2C South of Mountjoy to South of Omagh
South of Omagh to Aughnacloy Section 3 796036-R-0600-007
South of Omagh to Gortaclare / Section 3A Moylagh Section 3B Gortaclare / Moylagh to Ballygawley Section 3C Ballygawley to Aughnacloy
1.3 Purpose of the Report This report presents the findings of the Preliminary Sources Study (PSS) that was undertaken to establish the geotechnical and geo-environmental constraints and potential risks associated with the proposed scheme. It provides the geotechnical and geo-environmental evidence that supports the decision making at POR1 and POR2 stages in selection of a preferred corridor and then a preferred route. The scope of the study was necessarily constrained by the scheme design under development by the project team and was carried out in accordance with the Statement of Intent (ref 796036-0600-R-00001) previously issued.
796036-0600-R-007 6 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
1.4 Format of the Report Following the Introduction, Chapter 2 identifies the information consulted as part of the desk study, Chapter 3 describes the field studies (including a preliminary ground investigation undertaken for the scheme), Chapter 4 presents the site description, Chapter 5 describes the ground conditions on site and Chapter 6 details the preliminary engineering assessment. Finally Chapter 7 presents a geotechnical comparison of the project options and risks.
Chapters 1 to 4 of this report will detail information relating to the entire 88km scheme within the wider Engineering Study area. From Chapter 5 onwards this Preliminary Sources Study Report will focus specifically on information pertaining to Section 3, the area south of Omagh to Aughnacloy and focus on information pertaining to the Preferred Route Corridor.
As outlined in section 1.2.4, three separate Preliminary Sources Study Reports will be produced reflecting the respective geographical split in the scheme.
1.4.1 Format of Drawings To aid with the management of the large volume of information gathered and assessment of parameters, drawings referenced throughout this report can be viewed and interrogated electronically within the Arc Reader (GIS) File accompanying this report, on hard drive. Although the referenced drawings can be selected from the navigation pane the reader is however also encouraged to navigate freely around the GIS model and turn layers on and off at will to compare and contrast features. Arc Reader contains the geo-environmental information for the entire scheme. Arc Reader not only presents the information spatially but also provides additional supplementary information about the features shown, either by hovering over and/or clicking on the symbology for the particular geo-environmental feature. General advice on how to use Arc Reader is also contained within Appendix A.
796036-0600-R-007 7 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
2 Sources of Information and Desk Study
2.1 Sources of Information The information sources and documents that have been consulted as part of the preparation of this PSS report, and in general accordance with the guidelines set out in HD22/08 are summarised in Table 2.1-1 and Table 2.1-2. Also included within these tables are details of how the information is pertinent to the scheme.
Table 2.1-1 Sources of Information
Information Data gathered Application of information Source Ordnance Survey Current OS mapping Man-made obstructions/voids/sources of contamination Historical Ordnance Survey of Man-made obstructions/voids/sources of Northern Ireland Maps contamination Historical mapping Digital historical mapping for 1830’s, 1860’s & 1900’s Former/present mining/quarrying and land- filling - Identification of geo-hazards Ortho Aerial photography (2006) Former/present mining/quarrying and land- filling - Identification of geo-hazards Aerial photographs (usually Former/present mining/quarrying and land- dating back to 1946) held by the filling – Identification of geo-hazards Public Records Office Soil Maps Determine soil types & other properties, geomorphology & physical geography, vegetation & land use Topography Maps Representation of the relief with contours Digital Terrain Mapping Digital representation of the relief Geological Survey 1:250 000 Geological Map of Solid geology along route corridor of Northern Ireland Northern Ireland (Solid Edition) 1:250 000 Geological Map of Quaternary deposits along route corridor Northern Ireland (Quaternary Edition) 1:250 000 Groundwater Identification of the vulnerability of Vulnerability Map of Northern groundwater to contamination - Aquifer Ireland recognition & groundwater conditions 1:250 000 Hydrogeological Map Hydrogeological risk assessment – Aquifer of Northern Ireland recognition & groundwater conditions 1:50 000 Solid Edition – Sheets Underlying Geology - Solid geology along 11, 33, 34, 45, 46. route corridor 1:50 000 Drift Edition – Sheets Underlying Geology - Drift deposits along 11, 33, 34, 45, 46. route corridor 6” Scale Field Maps Detailed Geological map Geological field slips Identification of likely ground conditions
796036-0600-R-007 8 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Information Data gathered Application of information Source Mineral Extraction Records Former/present mining/quarrying and land- filling - Identification of mineral extraction hazards Borehole Records Historical information on geotechnical & groundwater conditions Abandoned Mines Records Former mining location of shafts adits & abandonment plans - Identification of mining hazards Oil/Gas Extraction Former or present oil/gas extraction Website - Mineral Licensing Minerals & petroleum exploration & development in Northern Ireland Website - Petroleum Licensing Petroleum Licensing: September 2004, map indicating licenses applied by for by exploration companies Northern Ireland Contaminated Land Database Present/previous landfills & potentially Environment contaminating sites Agency Water Quality Management Unit Sensitivity of ground/surface water for drainage design, pollution incidents, consented industrial discharges, sewage discharges, designated groundwater extraction points. Industrial Pollution Unit Identification of industrial operations, COMAH sites – Enforcements, prohibitions, prosecutions Water Quality Includes GQA chemical & biological classification results for river Landscape Character Areas Landscape. Geological and biodiversity summaries Waste Licensing Unit Register of licensed & exempt sites Londonderry, Building Control Records of ground conditions for individual Strabane, Omagh buildings – this information is large in volume and Dungannon and therefore will be consulted when District Councils necessary for small parts of the scheme. Environmental Health Records of potential contaminating sites/landfills/fuel installations Planning Department Planning Applications, geotechnical & contaminated ground conditions The Department of Historical Ground Investigation Historical information on geotechnical and Finance and Reports groundwater conditions Personnel, Central Procurement Directive Geological Survey Co. Monaghan Drift maps Drift geology for Northern / Republic of of Ireland Ireland border area Quarry and mineral database Identification of mineral extraction hazards for Northern / Republic of Ireland border area Land Slides in Ireland Mouchel Internal A4/A5 Ballygawley Intersection PSSR & GI Records
796036-0600-R-007 9 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Information Data gathered Application of information Source Records A5 Newtownstewart Bypass Geotechnical design details A5 WTC Preliminary Options Report Geotechnical Walkover Survey Methodology Geotechnical Initial Key Constraints 796036- 0600-R-003A Geotechnical Statement of Intent 796036- 0600-R-00001 Public Records Current & Historical Ordnance Man-made obstructions/voids/sources of Office Survey of Northern Ireland Maps contamination Aerial photographs (usually Former/present mining/quarrying and land- dating back to 1946) held by the filling Public Records Office Department of Planning Service May provide reference to data submitted with Environment planning applications & also mineral planning (Planning details Services) British Geological GeoIndex Various Information including, SI’s, Shafts & Survey Adits, Mineral occurrence, topography, geology Department for Section Engineers: Information on ground conditions; Regional Subsidence; Earthwork Records; Previous Development: Londonderry Investigations Roads Service - Strabane Section Engineers Omagh Dungannon Agriculture & Rural Rivers Agency Culverted watercourses, low flow water Development: course and any pollution incidents to Rivers Agency watercourses Department of Website - Mosaic 4 Utilities Information on utilities from DRD Water Culture Arts & Service, Rivers Agency, DRD Roads Leisure Service, NTL, Phoenix Gas, & NIE.
Table 2.1-2 Statutory Undertakers (Utilities)
Authority Relevance to Scheme Phoenix Natural Gas Gas Service Locations Firmus Energy Gas Service Locations Northern Ireland Electricity Electricity service locations British Telecom Telecommunication service locations Cable & Wireless Telecommunications Telecommunication service locations Bytel Connections Telecommunication service locations Eircom UK Telecommunication service locations NI Water Water service locations The findings of these sources are discussed in Chapters 3 to 5.
796036-0600-R-007 10 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
2.2 Previous Ground Investigations The Central Procurement Directorate (CPD), part of Department of Finance and Personnel (DFPNI), has undertaken numerous ground investigations within the study area. The ground investigations were carried out for the various government sectors then known as Department of Finance (DOF) and Department of Health & Social Services (DHSS). GSNI have also provided selected borehole records and Mouchel already hold records for a number of ground investigations. A summary of the data held by Mouchel and obtained from both CPD and GSNI for Section 3 (South of Omagh to Aughnacloy), is shown in Table 2.2-1. Details of these logs including material descriptions and any test results are described in Chapter 5 and hyperlinked within the exploratory hole location plan in GIS on Drawing 796036-0600-D-00062.
Table 2.2-1 Summary of Ground Investigation Reports for Section 3: South of Omagh to Aughnacloy
Source of Information No. of Holes Max Depth (m)
CPD 105 28.30
GSNI 75 116.40
Mouchel Historical Boreholes 230 25.00
796036-0600-R-007 11 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
3 Field Studies
This chapter provides details of a number of surveys which have been carried out for site characterisation purposes to identify the key geotechnical constraints within the area under consideration. All relevant observations made during the survey are recorded and discussed further in Chapter 4. Photographs and survey notes for the surveys can be viewed within the following Drawings:
Table 3.0-1 Drawings showing location of field survey data
Survey Drawing Reference Drive Through Survey Notes & Photographs 796036-0600-D-00063 Walkover Survey Reports and Photographs 796036-0600-D-00064 Mineral Extraction Sites & Landfill Survey 796036-0600-D-00065 Peat Survey 796036-0600-D-00066 Preliminary Ground Investigation Location Plan and 796036-0600-D-00067 Photographs
3.1 Drive through Survey An initial familiarisation of the A5 study area was undertaken on 3 rd and 4 th March 2008 by Mouchel personnel to identify the key geotechnical constraints within the Stage 1 engineering study area. The results are illustrated on Drawing 796036-0600- D-00063.
3.2 Walkover Survey Mouchel personnel undertook a more detailed survey of the engineering study area from the public highway from 18 th March to 25 th April 2008 inclusive. The walkover survey was carried out as part of the geotechnical procedure to identify, inform and cross check from the published data the geological, geomorphological and man- made issues that might affect selection of a route and ultimately require a design solution. The key geological & geomorphological features recorded during site reconnaissance are illustrated on Drawing 796036-0600-D-00064. Walkover reports, prepared by Mouchel, detailing the geological and geomorphological features are hyperlinked within this drawing in the GIS Model. The final walkover report, report No. 796036-0600-R-013 summarises the results of the walkover survey.
3.3 Quarry and Landfill Survey Additional site survey work was undertaken in August 2008 during the data collection period to establish the status of the various gravel pits, quarries and landfill sites identified throughout the study area. This survey supplemented initial records obtained from the statutory agencies which did not make clear the current status of the sites, i.e. operational or disused, backfilled or open scars in landscape. The photographs and observations are shown on Drawing 796036-0600-D-00065.
796036-0600-R-007 12 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
3.4 Peat Surveys A preliminary visual survey of the peat bogs identified throughout the study area was undertaken from the public highway on 28 th July 2008 to confirm the type of peat bog i.e. blanket (upland) peat, inter-drumlin accumulations or raised (lowland) bog. A high level review of the stability of the peat bogs was also undertaken with observations recorded on Drawing 796036-0600-D-00066. Additional survey work may be required when a preferred route option is established.
3.5 Preferred Route Corridor Survey Mouchel staff undertook a visual assessment of the key geotechnical constraints specific to the preferred route corridor on the 23 rd & 24 th September 2008.
3.6 Preliminary Ground Investigation The aim of the ground investigation was to obtain outline geotechnical data to allow a comparison between the route options and to assist in the decision making process of identifying the preferred route.
3.6.1 Rationale The following aspects were investigated:
Nature and depth to rock, where rock excavation might be expected Nature and thickness of peat and soft alluvial soils where these have to be crossed. The bearing properties & settlement characteristics of the soft deposits and their ability to support the carriageway and embankments Possible instances of made and contaminated ground 3.6.2 Description of Field Work A preliminary Ground Investigation was carried out between the 16 th February 2009 and 20 th March 2009. The works were designed and specified by Mouchel as reported within Annex ‘A ’report (ref. 796036-0600-R-009, December 2008) which is included in Appendix C.
The ground investigation works were undertaken by Soil Mechanics under their current framework with Roads Service. All ground investigation works were carried out as specified in Annex A in accordance with the Manual of Contract Documents for Highways Works (Volume 5, Section 3, Part 4) and BS 5930 (1999). Selected amendments were made to the Section 3 schedule following a route rationalisation process in January 2009. Under sub-contract to Soil Mechanics, Lankelma performed the Cone Penetration Tests and the window sampling was undertaken by Paul Mullin Site Investigations. Mouchel monitored the works full-time on site. The locations of the exploratory holes are shown on Drawing 796036-0600-D-00067 and a summary of the findings are presented in Table 3.6-1 below.
796036-0600-R-007 13 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Table 3.6-1 Summary of Preliminary GI Works
Location Type of No. of Holes Max Depth (m) Typical Exploratory Hole Completed Bedrock Depth (m)* Section 1 Borehole 3 31.6 5.5 – 7.5
CPT 19 27.9 1.6 – 9.4
Window Sample 53 6.0 1.1 – 6.0
Section 2 CPT 2 7.3 Not determined
Window Sample 26 5.0 1.6 – 5.0
Dynamic Probe 39 9.4 1.7 – > 9.5
Section 3 Borehole 2 22 14-18
CPT 4 11.36 Not Determined
Window Sample 20 6 1 - >6
Dynamic Probe 42 7.1 1.4- >7.1
* depth to bedrock shown is a typical average for the section, though it boreholes tend to be on river floodplain areas, where depth to be rock can be significantly greater.
Representative small disturbed samples were taken at approximate depth intervals of 0.5m, 1.5m and 3.0m below ground level and stored in airtight containers for identification, description and testing purposes. Classification testing was performed on the collected samples to determine moisture conditions and Atterberg Limits.
Standpipes were installed in BH01-S and BH02-S to a depth of 22m & 18m respectively and in 10 No. window sample holes to a maximum depth of 6m to monitor groundwater levels.
The laboratory results are summarised in Chapter 5. The draft factual report by Soil Mechanics (report ref Y9901) contains the logs, in-situ field tests and results of laboratory testing and has been issued separately to this report. Logs are also hyperlinked within the exploratory hole location plan in the GIS Model, Drawing 796036-0600-D-00067.
796036-0600-R-007 14 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
3.7 Other Field Work Topographic, drainage, ecological and archaeological surveys have been separately carried out by Mouchel and are reported separately. No issues have been identified that are likely to have an impact on any geotechnical issue.
796036-0600-R-007 15 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
4 Site Description
This chapter summarises the available background information that is relevant to the geotechnical and geo-environmental conditions within the engineering study area pertaining to Section 3 of the scheme, as detailed in Chapters 1,2 & 3 of this report. From Chapter 4 onwards will detail information specifically for Section 3, the region from the South of Omagh to Aughnacloy.
4.1 General The study area is a 14km wide area associated with the section of the existing A5 carriageway which extends through County Tyrone from south of Omagh before terminating at Moy Bridge where it meets the N2 at the Irish border south of Aughnacloy.
The existing A5 intersects two key routes, the B46 which extends from Carrickmore in the east to Ballinamallard in the west and further south the strategic A4/M1 east- west route between Belfast & Enniskillen at the Ballygawley roundabout junction. The A5 also links to the A28, B35/B128 and N2 at Aughnacloy. The existing A5 is a patchwork of single lane carriageway, climbing lanes and segments of overtaking lanes. The road network is mainly at grade but is in significant areas of cut around Slievemore and to the north of Aughnacloy with large embankments encountered around the Gortaclare / Moylagh area and over the Ballygawley Water.
Although there are no district towns present within the area, numerous settlements exist primarily located along the aforementioned routes. Aughnacloy and Ballygawley are the two key settlements to the south and east of the area, Augher and Clogher to the southwest, further north Garvaghy through which the existing A5 passes, Newtownsaville and Eskragh in the west with Sixmilecross, Beragh, Seskinore and Fintona situated along the B46. Drawing 796036-0600-D-00068 illustrates the main geomorphological features in Section 3. This area can be divided into three discreet zones which are defined by the underlying geology and topographical form as described in more detail in Section 4.2 below and summarised in Table 4.1-1.
Table 4.1-1 Summary of Topographical Zones within Section 3
Geography Topography South of Omagh to Gortaclare / Moylagh Drumlins (less pronounced – small scale) Gortaclare / Moylagh to North of Ballygawley Sandstone ridge North of Ballygawley to Aughnacloy Drumlins (large scale)
796036-0600-R-007 16 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
The north of the section from Omagh to Gortaclare/Seskinore is characterised as a deeply undulating lowland drumlin landscape with patches of marsh in low-lying areas between the drumlins. Drumlin heights in this area vary between 4 to 10m with typical 1:10 to 1:5 side slopes. Inter-drumlin areas are at low level at less than 100m AOD.
Moving south the landscape is dominated by an upland area of broad sandstone ridges dissected by short steep glens, The north facing slopes are long and gentle, but the south facing slopes form a steep escarpment. The ground rises towards the south east to the summits of Slievedivena (290m AOD) and Slievemore (313m AOD).
South of this “Slievemore” ridge is a broad lowland corridor with small rounded hills in the Clogher Valley. Around Aughnacloy the landscape is dominated by large scale drumlins. The drumlins here are better developed and higher than around Omagh, with heights of up to 20m and side slopes of 1:8 – 1:5.
Peat is sporadically found throughout the area with a prominent blanket peat bog on the high ground of Slievemore in the east as shown in Figure 4.1-1. A large raised peat bog is found to the north west of Beragh and extensive peat bogs are present in the north of this section in the Tattyreagh – Seskinore Forest area.
Figure 4.1-1 Blanket peat bog on Slievemore
This area incorporates 4 key river catchments: Camowen, Quiggery and Drumragh Basins which all feed into Lough Foyle, and the Blackwater catchment which transfers in a southerly direction towards Lough Neagh. The Drumragh River, Camowen River and Quiggery Water to the north flow within narrow valleys between the drumlins. The broad shallow valleys of the Eskragh Water and Garvaghy Water, which are tributaries of these, cut through the high ground along the sandstone ridge, running perpendicular to the ridge axis. To the south, the two main river valleys of the Ballygawley Water, which flows through a deep broad valley, and the River Blackwater, which forms a band of broad flat ground, are the principal watercourses of the Blackwater catchment.
796036-0600-R-007 17 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
The area is predominantly rural with agriculture as the key land use in the form of animal grazing and minor grain crop growing. Mineral extraction is also prevalent throughout the area with sand and gravel pits occurring particularly around Eskragh and on the summit of Slievemore. 4.2 Geography & Topography A 3-D interpretation of the terrain is shown on Drawing 796036-0600-D-00068 which shades the relief in 100m intervals, whilst Drawing 796036-0600-D-00069 conveys the steepness of the terrain by colour coding the slope gradient.
4.2.1 Omagh – Gortaclare/Seskinore (Sub-Section 3A) This area lies within the Omagh Farmlands Landscape Character Area (LCA) and is a lowland drumlin landscape. The poorly developed drumlins are typically between 5-10m high and 50-200m wide with side slopes generally between 1:10 and 1:5 as illustrated in Figure 4.2-1. Inter-drumlin areas are at low level at less than 100m AOD. The drumlin landscape gives way to high ground towards the east. The drumlin topography also becomes less pronounced to the south and southeast of the area as the ground rises towards the sandstone ridge.
Figure 4.2-1 Lowland drumlin landscape south of Omagh
Narrow, sinuous river valleys of the Drumragh River, Camowen River, Ballynahatty and Quiggery Water tend to follow and widen gaps between the drumlins. These catchments all feed into the main River Foyle catchment basin and flow north towards Lough Foyle.
4.2.2 Seskinore/Gortaclare – Ballygawley (Sub-Section 3B) This region is an east north east – west south west ridge high in relief, with ground levels generally above 100m AOD, dominated by the summits of Slievemore (313m AOD) and Slievedivena (290m AOD) in the east (Figure 4.2-2). The northwest facing slopes of this ridge fall at a shallow gradient towards Omagh and are cut by broad shallow valleys of the Eskragh Water and Garvaghy Water. The Seskinore River is formed when the Routing Burn and the Eskragh River converge approximately
796036-0600-R-007 18 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
2.5km south east of Seskinore. In general, these watercourses flow in a southeast to northwest direction.
Figure 4.2-2 High ground of Slievemore
Conversely, the southeast facing slope, which is fault controlled, is typically of 1:5 gradient, though locally occurs as steep as 1:3. The ridge is crossed by a number of valleys and natural passes one of which has been adopted by the current A5 alignment northwest of Ballygawley and by other minor roads including the B83 and B186. Streams originate amongst marshy areas which descend through incised valleys on steep slopes to the lower regions.
Land is particularly constrained around the development areas of Garvaghy and Eskragh and the valleys through the sandstone ridge are steep sided, narrow and sinuous.
4.2.3 Clogher Valley & Aughnacloy (Sub-Section 3C) The terrain in this area comprises very closely packed drumlins in the Clogher Valley. The drumlins here are better developed and higher than around Omagh, with heights of up to 20m and side slopes of 1:8 – 1:5 (Figure 4.2-3). Deep inter-drumlin areas are often infilled with soft soils and linked by rivers and streams. The valley is crossed by the Ballygawley Water and Blackwater River, both of which have locally broad, flat flood plains (Figure 4.2-4).
796036-0600-R-007 19 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Figure 4.2-3 Drumlin landscape in Sub-Section 3C
Figure 4.2-4 River Blackwater tributary
To the east of Aughnacloy and Ballygawley, the ground rises to form the rocky high ground of Big Hill, Burnt Hill & Branny Hill (120mAOD) which have localised steep slopes
4.3 Land Use Land use within the study area is predominantly agricultural, mainly pastoral but with some local arable use (grain and fodder crops). Beyond the boundaries of the main towns of Ballygawley and Aughnacloy and the settlement areas of Moylagh, Gortaclare, Garvaghy and Newtownsaville, residential development is sporadic and generally isolated to single dwellings and farmsteads. Sand and gravel extraction activities are located at Eskragh in the west and on the high ground of Slievemore in the east.
796036-0600-R-007 20 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
A review of soil distribution across the area reveals the dominant soil type as (90%) Gley developed on Old Red Sandstone till or Old Red Sandstone conglomerate till. At Slievemore an area of peat (10%) is present.
The Agricultural Soil Classification indicates a mosaic of Grade 2, 3a, 3b and 4 land representing good quality, moderate quality and poor quality agricultural land respectively. Grade 3a land is dominant with grade 4 land generally associated with the areas of peat. Grade 2 agricultural land is limited and mainly corresponds to the areas of sand and gravel deposits in particular at Eskragh and Garvaghy.
4.3.1 South of Omagh – Gortaclare/Seskinore (Sub-Section 3A) The predominant land use in the area is pastoral farming. Drumlins in the area provide well drained farmland with less productive agricultural land in the inter- drumlin areas which are generally wetter and marshier.
The main settlements within this section are Edenderry in the north and Seskinore and Moylagh / Gortaclare in the south. These are small settlements which are primarily agriculture based. Individual farmsteads and houses are located along local roads and spread throughout the sparsely populated rural landscape. Industries are mainly limited to a food processing plant and petrol filling stations.
Seskinore forest comprises a mixture of mature woodland and carr woodland developed on lower drumlin slopes, marshy inter drumlin areas as well as peat bogs and covers an area of approximately 1km 2. There is evidence of some commercial forestry.
An extensive area of raised peat bog (approximately 750,000m 2) was noted to the south of Tullyrush. The peat typically protrudes 6 to 8m above the surrounding area. There are widespread areas of similar raised peat bog east of the A5 and south of Omagh in the area between Eskermore, Gortaclare, Beragh and Omagh. The peat is exploited on both a commercial and domestic scale. Characteristic of areas of peatlands, there are significant, though sporadic, areas of fly tipping and artificial infilling throughout the section.
The predominant soil classification is 3a with small areas of Grade 2. These are described as good quality and very good quality agricultural land respectively. Areas of peat reduce the land quality to Grade 4 which is of limited agricultural use whilst alluvial deposits associated with the main watercourses are classified as Grade 3b which is moderate quality agricultural land.
4.3.2 Seskinore/Gortaclare – Ballygawley (Sub-Section 3B) This upland section comprises a diverse mosaic of pastures, woodland with marshy hollows and abandoned quarries. The area is generally used for rough pasture, with few well drained fields. Large areas in the highlands are poorly drained with marshland giving rise to small streams. Around Slievemore in the east the land use is mainly coniferous plantations and upland bog and peat, with some extensive sand
796036-0600-R-007 21 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
and gravel quarries. The lower slopes of Slievemore are generally used for grazing cattle with limited marsh areas and damp woodlands located in the hollows.
Settlements in this section include Beragh, Sixmilecross, Eskragh, Garvaghy, Newtownsaville and Roscavey. These communities are primarily agriculturally supported with the exception of the sand and gravel pits situated at Eskragh and Slievemore. Outside of the settlement areas, isolated single rural dwellings are common. Aside from the sand and gravel extraction operations, commercial sites within the section are limited to petrol filling stations. A number of waste water treatment works are located in the area at Eskragh, Garvaghy and Altamooskan. Knockmany forest is privately managed.
Large elevated valley areas are shallow in depth, with streams originating amongst the marshy areas and descending through incised valleys on steep slopes to the lower regions. Fly tipping is common in the section particularly next to peat bog northeast of Tullycorker.
The predominant soil classification in the section is good quality Grade 3a agriculture land with minimal areas of very good quality Grade 2, mainly restricted to the sands and gravels at Eskragh. Areas of peat reduce the land quality to Grade 4 which is of limited agricultural use whilst alluvial deposits associated with the main watercourses and poor quality clays are classified as moderate quality Grade 3b agricultural land.
4.3.3 Clogher Valley & Aughnacloy (Sub-Section 3C) Residential development is focussed to the town of Aughnacloy in the south of the section and the smaller settlements of Ballygawley in the east and Augher and Clogher in the west. Land Use within Aughnacloy town includes both filling stations and waste water treatment works. Elsewhere in the section isolated single dwellings are located sporadically and agriculture is the main industry. A large active landfill is situated at Tullyvar with a smaller reclaimed landfill to the east of the Aughnacloy town.
Significant areas of Forest Service managed woodland and private grant-aided woodland are located within this section in Favour Royal Forest and Gallagh and Lismore Woods.
Grade 3a and 3b land dominate this region with limited Grade 4 land. Extensive areas of Grade 3b are associated with the wide alluvial floodplains of the Ballygawley Water and River Blackwater and their tributaries.
796036-0600-R-007 22 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
4.4 Historical Mapping Historical mapping for the study area was obtained from the Ordnance Survey of Northern Ireland and Public Records Office for Northern Ireland. Copies of the maps are included within the Arc Reader (GIS) model as Drawings 796036-0600-D-00070 to 796036-0600-D-00075 and convey the historical development of the study area since 1830 to present day. Appendix D provides information on the features identified within the study area with a summary provided below.
During the 19 th Century, industry was predominantly in the form of corn and flax mills, located across the section. Numerous gravel pits are shown on the mapping of 1834 and later appear as scars in the landscape. By 1960 the traditional milling industries had diminished across the landscape along with many of the small gravel pits and quarries. The Clogher Valley Railway ran west to east from Clogher to Ballygawley and then south to Aughnacloy in the early 20 th Century however is disused with many parts reclaimed and redeveloped by the 1960s.
Some Industrial development has occurred in close proximity to residential centres particularly around Aughnacloy with modern light engineering works identified in current mapping.
A number of rivers have altered course and straightened for agricultural purposes and where Loughs have reduced in size, bog land is now a feature.
4.5 Aerial Photography Aerial photographs were obtained from the OSNI and are shown in relation to the study area on Drawing 796036-0600-D-00076.
A comparison between the historical mapping through the years and the recent aerial photography shows that the area has experienced extensive recent development, primarily residential, but with some industrial as summarised in Table 4.5-1.
Table 4.5-1 Principal Differences between Historical Mapping and Current Aerial Photography
Location Grid Description of Change Reference South of Omagh to Gortaclare / Seskinore (Sub-Section 3A) South of Omagh to 250544, Great Northern Railway (Portadown to Londonderry Branch) Beragh 369928 now dismantled and much of the railway line overgrown.
Southeast of 248832, Arvalee WWTW appears on aerial photography Omagh 372127
South of Gortaclarre 251963, A petrol filling station is now present adjacent to the existing / Moylagh 364230 A5.
251322, Legacurry WWTW appears on recent mapping and aerial West of Gortaclare 364438 photography
796036-0600-R-007 23 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Location Grid Description of Change Reference Northwest of 250751, Loughpatrick has reduced in size. Beragh 368618 Gortaclare / Seskinore to Ballygawley (Sub-Section 3B)
254088, Barony Bridge Flax mill has now been demolished 362129
Slievemore 260518, Sand and gravel pits at Fallaghearn have been significantly 363053 extended in recent years on aerial photography
256010, Garvaghy New residential development 360206
251115, Sand and gravel pits at Eskragh have been significantly Eskragh 359344 extended
256970, Sixemilecross WWTW appears on recent mapping and Sixmilecross 367827 aerial photography
Clogher Valley & Aughnacloy (Sub-Section 3C) 256651, Augher Flax mill and saw mill have now been demolished 353802
254214, Clogher Residential development 352437
259133, East of Augher Straightening of River Blackwater 353753
264541, Tullyvar Site of quarry has now become an active landfill site 352286
266541, Aughnacloy Residential development 352286
Northeast 266816, Gas works on historical mapping is now no longer visible on Aughnacloy 352389 aerial photography
North of 265557, Clogher Valley railway line now closed and redeveloped to Aughnacloy 354206 form part of existing A5
796036-0600-R-007 24 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
4.6 Geology 4.6.1 Structure & Faulting The nature of the landscape and terrain is very much a function of the underlying solid geology. The solid geology can be viewed on Drawing 796036-0600-D-00077 and the geological successions are shown in Table 4.6-1, Table 4.6-2 and Table 4.6-3 below. The underlying geology of the study area is structurally complex, but falls into two provinces: the mainly Devonian rocks dominant to the north of the section and the mainly Carboniferous rocks dominant to the south. Strata boundaries are largely fault controlled and significant ENE-WSW trending faults divide this section into 3 blocks of different strata. Section 3 is south of the Omagh Thrust Fault and the Sperrin Mountains.
In the north are two fault lines which merge to form one fault across the section: the Tempo-Sixmilecross Fault and the Killadeas-Seskinore Fault. These faults come together at Gortaclare/Moylagh and pass across the south of Sub-Section 3A and the north of 3B. The joints have disturbed the rock layers and show a change in strata as shown in Table 4.6-2 and Table 4.6-3.
Between this northern fault and the Clogher Valley fault in the south lies a ridge of high ground comprising Carboniferous rocks from the Gortfinbar Conglomerate Formation overlain to the northwest of the area by the Raveagh Sandstone Formation and to the south by the Ballyness Formation.
The Clogher Valley Fault to the south in Sub-Section 3C passes west to east. Better described as a fault zone, this consists of up to 3 subsidiary faults and forms the southern steep face of the Slievemore ridge.
4.6.2 Bedrock Geology 4.6.2.1 South of Omagh – Gortaclare/Seskinore (Sub-Section 3A) This northern section is underlain by Devonian and Carboniferous age strata which are largely sandstones in this section. The sequence bounded to the south by the major NE-SW trending Killadeas – Seskinore Fault and the Tempo – Sixmilecross Fault. The dominant strata are the Shanmullagh Formation. This formation largely consists of purplish to red-brown sandstones, siltstones and mudstones inter-bedded in varying proportions.
Other younger formations are locally present include the Ballyshannon Limestone Formation, Claragh Sandstone Formation and Greenan Sandstone Formation, along with the older Tyrone Volcanic group. These are largely present in the far north of this section and associated with the complex Omagh Thrust Fault. The latter two strata particularly are limited in extent with the far east of the study area.
796036-0600-R-007 25 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Table 4.6-1 Solid geology strata within Sub-Section 3A
Geological Spatial/Geographic Age Description Rock Type Context
Palaeogene Dolerite and Olivine Basalt and Dolerite, intermediate grain South west of Basalt (D) size intrusive and lava flow igneous strata, Seskinore. Only present
associated with the Antrim Basalts. as a thin wedge.
Greenan Green mudstone laminae in the sandstone North of Edenderry. Sandstone Only present as a thin Namurian Formation wedge. (GNNS) Ballinamallard Mudstone and siltstone, greyish red, rarely In the area of Seskinore
Carboniferous Mudstone greyish green and to the west. Formation (BLM) Ballyshannon Limestone, dark bluish grey, some silty mudstone, Present as a small Limestone fossiliferous; rare chert wedge southwest of
Dinantian Formation Omagh (BAL)
Claragh Coarse grained, pebbly arkosic sandstone with Present as a small Sandstone channels and planar cross-lamination features. wedge south of Omagh Formation (CLSG)
Upper Raveagh Sandstone, very coarse grained, fine South east of Seskinore. Sandstone conglomerate, fawn and grey, arkosic. Only present as a thin
Formation wedge. (RSF) Palaeozoic Barrick Hill A fine-grained, usually porphyritic plagioclase West of Edenderry. Andesite feldspar with amphibole or biotite. Only present as a thin Member wedge. (BHAM) Middle Devonian Gortfinbar Conglomerate, purplish brown, clasts boulder and Limited presence to the
Conglomerate pebble sized, volcaniclastic, rare vein quartz, south of the Formation quartzite and greywacke; sandstone, coarse- Shanmullagh Formation, (GOCF) grained. along the Killadeas- Seskinore Fault. (subsidiary vesicular, flow banded lava) Shanmullagh Brown coarse grained pebbly sandstone, thin Covers a wide area to Formation purplish grey fine-grained sandstone and the north of the Tempo- Lower (SHAN) mudstone. Also consists of purplish grey Sixmilecross Fault. sandstone and mudstone laminae with ripples. Sandstone also in channels (up to 2 m deep) & consists of sand siltstone, reddish brown mudstone. Copney Pillow Fine to medium grained, locally porphyritic ocean West of Edenderry. Lava floor basalt, with some pink chert or fine-grained Only present as a thin Ordovician Formation hyaloclastite breccia. wedge. Arenig (CPL) Tyrone Intermediate Lavas and volcanistic tuffs, rhyolites, West of Edenderry. Volcanic banded chert, jasper and argillaceous sediment. Only present as two Group small wedges. (TVG)
796036-0600-R-007 26 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Granite (Gb) Coarse to very coarse grained, granular, mottled In the area to the west of in white, pink and red colours on white with some Edenderry to section
Caledonian Ordovician dark grains, containing quartz, alkaline feldspar end. and plagioclase in variable amounts. Quartz A fine-grained igneous rock that contains isolated West of Edenderry. Feldspar large crystals of quartz and feldspar. Only present as a thin
Porphyry wedge. (qFb)
Proterozoic Corvanaghan Gritty, medium-to coarse-grained, grey and West of Edenderry. Moinian Formation pinkish grey psammite with minor schistose and Only present as a small
pelitic rocks. wedge. (CV)
4.6.2.2 Seskinore/Gortaclare – Ballygawley (Sub-Section 3B) The two major geological fault lines form the northern (Killadeas – Seskinore Fault line) and southern (Clogher Valley Fault) boundaries of this up-thrust central block forming the Slievemore Ridge, which comprises coarse conglomerates (and minor volcanic lavas) of the Gortinfinbar Conglomerate Formation, again of similar Devonian Age. The conglomerate contains mainly volcanic cobbles, with some quartzite and sandstone. In the Northwest of this section, the strata become finer in grain size of the red brown coloured Raveagh Sandstone Formation, whilst the younger Ballyness Formation is a red and purplish red sandstone and conglomerate. Throughout this area, the conglomerate and sandstone will be very close to surface.
On the southern edge of this section, the Clogher Valley Fault consists of a complex of several interlinked faults and some of these have dropped down blocks of the younger Ballyness (sandstone) and Clogher Valley (mudstone) Formations. These fault lines are clearly visible in the 3-D digital terrain model.
Table 4.6-2 Solid geology strata within Sub-Section 3B
Geological Rock Age Description Spatial Context Type
Palaeogene Dolerite And Basalt Olivine Basalt and Dolerite, Occurs in several locations, to the (D) North, the East and the South East
as small wedges and the most prominent, a long thin section to the North West.
Namurian Ballinamallard Mudstone and siltstone, greyish red, North West of the section. Only Mudstone rarely greyish green. present as a thin wedge. Formation (BLM)
Viséan Viséan Maydown Is a Limestone formation with abundant South of the section, running central Limestone Asbian corals and brachiopods. to east. Only present as a thin Formation wedge. (MYLF)
Clogher Valley Fossiliferous mudstone, siltstone, Occurs to the South of the section. Formation sandstone and thin crinoidal limestone. Present as many wedges to the (CVG) south along two fault lines.
796036-0600-R-007 27 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Geological Rock Age Description Spatial Context Type
Ballyness Red and purplish red sandstone and Occurs to the South of the section. Formation (BYC) conglomerate. Present as many wedges to the south along two fault lines. Raveagh Sandstone, very coarse grained, fine Overlies the Gortfinbar Formation in Upper Sandstone conglomerate, fawn and grey, arkosic the NW of section 3B. Formation (RSF)
Gortfinbar Conglomerate, purplish brown, clasts Covers a wide area of the section Conglomerate boulder and pebble sized, and the predominant rock type. Formation volcaniclastic, rare vein quartz, (GOCF) quartzite and greywacke; sandstone, coarse-grained.
Devonian (subsidiary vesicular, flow banded lava) Middle Shanmaghery Sandstone, purplish brown, red and North East of Section, South of Six Sandstone green stained, coarse-grained, Mile Cross. Only present as a thin Formation (SMSF) calcareous, micaeous, fining upwards, wedge. with thin siltstone and mudstone intercalations; parallel, cross and ripple laminations and desiccation cracks. Basal conglomerate with pebbles of vein quartz, quartzite, biotite granite, tuff, jasper and mica schist.
Lower Shanmullagh Brown coarse grained pebbly North East of Section, around Beragh Formation (SHAN) sandstone, thin purplish grey fine- and Six Mile Cross. Only present as grained sandstone and mudstone. a small wedge north of T-S fault.
4.6.2.3 Clogher Valley & Aughnacloy (Sub-Section 3C) The Clogher Valley is underlain by Carboniferous age rocks of the Clogher Valley and Maydown Limestone Formations. Rocks of the Clogher Valley Formation are described as a fossiliferous mudstone, with bands of sandstone and limestone, while the Maydown Formation is a fossil rich limestone. This forms the high ground east of Aughnacloy and is one of the few strata in the district that may be a significant groundwater resource. This area is highly faulted with a number of subsidiary faults of the Clogher Valley Fault.
Table 4.6-3 Solid Geology strata within Section 3C
Age Geological Rock Type Description Spatial Context
Palaeogene Dolerite And Basalt (D) Olivine Basalt and Dolerite, North and South of Aughnacloy. intermediate grain size Only present as two small wedges.
C a r b o Palae nifero Viséa ozoic Carrickaness Sandstone Coarse-grained, pebbly lithic Present as two wedges to the us n Formation (CRSF) sandstone. South East, the larger spreading
west to Aughnacloy.
796036-0600-R-007 28 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Age Geological Rock Type Description Spatial Context
Meenymore Formation Sandstone, brown; micritic Present as two small wedges to (MEF) limestone; mudstone, grey with the South West of the section, sparse marine fauna of corals, South of Augher. brachiopods and nautiloids. Dartry Limestone Limestone, dark grey, bluish black Occurs as several small wedges to Formation (DARL) chert, fine-grained, fine-grained, the South of Augher. fossiliferous; thin mudstone. Maydown Limestone Is a Limestone formation with Present to the North and to the Formation (MYLF) abundant Asbian corals and South, covering a large area. branchiopods. Bundoran Shale Mudstone, dark grey, yellow Present as a wedge to the South Formation (BUNS) staining; with siltstone, calcareous East of Aughnacloy. fossiliferous limestone. Thin basal multicoloured clay. Clogher Valley Fossiliferous mudstone, siltstone, Occurs as a wedge to the west,
Tournaisian Formation (CVG) sandstone and thin crinoidal covering most of the North West of limestone. the section, including Augher, and occurring south of Ballygawley. Ballyness Formation Red and purplish red sandstone Occurs as a wedge across the (BYC) and conglomerate with clasts central area of the section from mainly of white quartz pebbles. east to west.
Devonian Gortfinbar Conglomerate Conglomerate, purplish brown, Present as two small wedges to Middle Formation (GOCF) clasts boulder and pebble sized, the East and West, South of volcaniclastic, rare vein quartz, Ballygawley and Augher. quartzite and greywacke; sandstone, coarse-grained.
4.6.3 Superficial Geology The superficial geology of the engineering study area comprise of Glacial, Alluvial, and Peat soils, with extensive rock outcrop deposits as shown on Drawing 796036- 0600-D-00078 and indicated below in Table 4.6-4, Table 4.6-5 and Table 4.6-6.
This sub section is underlain by glacial deposits, comprising mainly Glacial Till with Glaciofluvial Sands & Gravels primarily in the main valleys. Alluvial Deposits are generally encountered on the banks of the main rivers and their associated floodplains. Peat indicated throughout the area occurs primarily in three forms, the raised peat bog which occurs in the low-lying ground within the Omagh Farmlands; the upland Blanket Peat Bog which has accumulated on the crest of Slievemore and areas of peat which have formed within the waterlogged drumlin hollows in the Clogher Valley. Rock Outcrops occur in areas of high ground.
4.6.3.1 South of Omagh – Gortaclare/Seskinore (Sub-Section 3A) The area is dominated by Glacial Till, forming drumlins of stony clay. Land adjacent to the main watercourses is generally underlain by local narrow bands of River Alluvium, which extends up to 50-100m wide near Beragh. Both Glaciofluvial Sands and Gravels and Lake Alluvium are also associated with in the river valleys, which are of glacial origin.
796036-0600-R-007 29 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Extensive peat bogs are noted throughout the area particularly to the north east of this area, with numerous pockets of lowland raised peat bog particularly in the region SE of Omagh, around Tattyreagh and Seskinore Forest. Small pockets of peat also occur to the west, and sporadically throughout the area in general. Rock Outcrop is shown to be at or close to the surface to the east and south east of the existing A5 around Seskinore where the ground rises towards the Slievemore ridge.
Table 4.6-4 Drift geology of Sub-Section 3A
Drift Deposits Spatial Context Glacial Deposits The area is largely shown to comprise Glacial Till deposits with the exception of those areas where rock is at or within a close proximity of the ground surface, particularly west and south west of the existing Glacial Till A5 around Seskinore where the ground rises towards Crocknatummoge and the Slievemore ridge.
Glaciofluvial Sand & Gravel deposits occur west of the existing A5 adjacent to the Seskinore River Valley. Sporadic pockets occur east of the A5 with more extensive deposits further east around Glaciofluvial Sand & Gravel Coolesker and Eskerrnore.
Alluvium Deposits Extensive alluvial deposits occur along the Camowen, Cloghfin and Seskinore Rivers. Thin tracts of alluvium is also associated with smaller watercourses such as the Raw Burn and the Tattykeeran Burn, River Alluvium to the west of the area, and the Letfern Burn to the south.
Lake Alluvium is generally recorded in low-lying, poorly drained areas. Two pockets of Lake Alluvium Lake Alluvium deposits are noted, one to the north of Seskinore, where previously a mill pond was situated and the other to the north of Seskinore, Peat Deposits Extensive areas of raised peat bog occur throughout this region predominatly in the low-lying inter- Raised Peat Bog drumlin areas, SE of Omagh and around Tullyrush, Tattyreagh & Seskinore Forest.
Rock Outcrop Shanmullagh, Gorfinbar As indicated above rock is shown close to the ground surface to the west and south west of the existing Conglomerate, Formations A5 around Seskinore where the ground rises towards Crocknatummoge and the Slievemore ridge
4.6.3.2 Seskinore/Gortaclare – Ballygawley (Sub-Section 3B) The central high ground area is shown to be extensively drift free. Land adjacent to the main watercourses, including the river banks and old or existing floodplains, of the Eskragh and Cloghfin Waters is generally underlain by river alluvium comprising soft / loose clay and sand.
Glacial Sand and Gravel outwash deposits are present on the margins of the uplands at Eskragh, Raveagh, Augher, Garvaghy and north of Ballygawley. Two deglacial sand and gravel complexes are designated by NIEA/GSNI as being of geological interest :- one to the west at Kilgreen and the other adjacent to the existing A5 at Ballymacilroy, which is considered more sensitive due to its geomorhological importance existing as series of raised flat topped units in the landscape. Eskers and other glacial features of these delta gravels are locally present. 796036-0600-R-007 30 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Extensive blanket peat dominates the summit of Slievemore and the east of the region. A number of smaller pockets of peat occur to the west of Garvaghy and on Crockandarragh and Crocknatummoge. Lowland Raised Peat Bog is locally present mainly to the north of the area, as well as a local area adjacent to the A5 S of Garvaghy.
Rock outcrops of the Gortfinbar Conglomerate Formation dominate this area of high ground.
Table 4.6-5 Drift geology of Sub-Section 3B
Drift Deposits Spatial Context
Glacial Deposits Due to the presence of significant areas of rock outcrop associated with this region of high ground, Glacial Till Glacial Till deposits are less extensive and are primarily only in the north east and south of the area. Glaciofluvial Sand & Gravel is present along the banks of the Ardunshin River to the south east, of the Eskragh Water and Routing Burn. The substantial deposits at Eskragh are currently being Glaciofluvial Sand & Gravel exploited for commercial use. Further deposits exist to the north and east of Garvaghy and south along the Curran River at Ballymacilroy which is a designated deglacial sand and gravel Complex. A further designated complex also exists at Kilgreen. Alluvium Deposits Extensive alluvial deposits to the east of the area along the Eskragh River west of the region River Alluvium adjacent to the Cloghfin River with smaller tracts associated with both the Routing Burn and Ardunshin River. Peat Deposits Pockets of Peat Bog are shown to be present in the inter-drumlin areas to the north and north west of Raised Peat Bog the area as well as an accumulation in a hollow adjacent to the A5 S of Garvaghy. Blanket Peat Bog caps the mountains of Slievedivena and Slievemore to the east and both Blanket Peat Bog Crocknahummoge and Crackandarragh to the west. Rock Outcrop Gortfinbar Conglomerate, Singificant areas of rock outcrop associated with the high ground to the west and to the east on Raveagh Sandstone, Slievemore.
4.6.3.3 Clogher Valley & Aughnacloy (Sub-Section 3C) The majority of the overlying material in the Clogher Valley is Glacial Till (boulder clay) formed into tightly packed oval shaped drumlins. Around the main watercourses, including the River Blackwater, Ballygawley Water and Ravella River, there are substantial deposits of soft alluvium, as well as on the river banks and in the surrounding inter-drumlin areas that are presently or were historically flood plains. The Blackwater particularly has associated tracts of alluvial sand and clay as much as 200m wide.
There are local deposits of Sand and Gravel in the vicinity of these river valleys, the main deposits are located to the north of the Ballygawley River, north of the Lisadavil River and within the locality of Augher.
796036-0600-R-007 31 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Raised Peat Bogs occur mainly to the west and north of the area. Peat accumulations are widespread in the inter-drumlin hollows, with the largest deposits found to the north of Augher.
The high ground to the east of Aughnacloy is largely devoid of drift soil cover, with bedrock at or close to the surface.
Table 4.6-6 Drift Geology of Sub- Section 3C
Drift Deposits Spatial Context Glacial Deposits Glacial Till is the dominant suerpficial deposit throughout the area, forming stony clay Glacial Till drumlins Glaciofluvial Sand & Gravel is located in the vicinity of the Ardushun River, the Tullybroom River, the Lisadavil and the River Blackwater. Extensive deposits extend Glaciofluvial Sand & Gravel along the Ballygawley Water to the north east and the Fedden river to the north of the area. Alluvium Deposits The most significant areas of River Alluvium are at the confluence of the River Blackwater running west to east, the Ravella River to the south of Aughnacloy and along River Alluvium the Ballygawley water. Alluvial deposits also extend adjacent to the River Blackwater, Mullans River, Ballygreenan, Roughan River and Annaghilla River. Peat Deposits Sporadic areas of peat bog occur mainly in the inter-drumlin hollows throughout the Peat Bog area, the most significant pocket located to the north east of Augher near Annaloughan Hill. Rock Outcrop Gortfinbar Conglomerate, Substantial rock outcrop is shown in this area particularly to the south east where the Ballyness, Clogher Valley and ground rises to the summits of Black Hill, Burnt Hill and Ivy Hill. Maydown Limestone Formations
4.7 Hydrogeology and Groundwater Vulnerability The resource potential for the aquifers underlying the study area and significance of pollution occurring thereto are shown on the hydrogeological map and groundwater vulnerability map in Drawing 796036-0600-D-00079 and 796036-0600-D-00080 respectively.
To the north from South of Omagh to South of Garvaghy the area is dominated by Devonian sandstone or conglomerate aquifers of limited or local potential. Sporadic areas of highly productive aquifers with inter-granular flow (typically glacial sands and gravel layers or alluvial deposits) are spread throughout this area, namely North West of Beragh, Eskragh, Altamooskan and Slievemore, all of which are of limited extent. A single area underlain by impermeable rock (underlain by Beragh Granite) exists north of Beragh.
796036-0600-R-007 32 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
In the southern part of the section the Clogher Valley formation is characterised as an aquifer with dominant flow in fissures which are locally important such as those around Clogher, Augher, Ballygawley and west of Aughnacloy. There are areas of highly productive aquifers with intergranular flow based mainly around the village of Clogher. To the south of Augher and the south east of the area these aquifers are classified as having dominant flow in fissures (due to the presence of fractured sandstone/conglomerate and limestone formations) and either highly productive or locally important.
The vulnerability of aquifers is controlled by the presence and nature of the overlying soil/superficial cover. Typically throughout the area, either no drift cover is present or Boulder Clay covers the bedrock. Localised glacial sands and gravel layers, peat or alluvial deposits are present. In terms of vulnerability the Boulder Clay provides the best aquifer protection, with the others offering little or no protection.
The Groundwater Vulnerability Map of Northern Ireland indicates that the area can be categorised into four groundwater vulnerability classes:
• Type A – high: high permeable geology, high soil leaching potential • Type A – low: high permeable geology, low soil leaching potential • Type B – high: moderate permeable geology, high soil leaching potential • Type B – low: moderate permeable geology, low soil leaching potential
The area between Edenderry and Ballygawley (Carboniferous & Devonian sandstone strata) is largely an aquifer described as Type B (Moderately permeable with low soil leaching potential). Locally, areas of Type B (Moderately permeable with high leaching potential) occur such as those to the east and north of Beragh, near Eskragh, to the northwest and east of Augher and to the northwest and east of Ballygawley. In these areas the drift cover is either absent or permeable alluvial deposits provide only limited or no aquifer protection.
Between Ballygawley and Aughnacloy the dominant aquifer is described as Type A (highly permeable – fractured Carboniferous sandstone, mudstone & limestone) with low or high leaching potential, intersected with Type B (moderately permeable) with either low or high leaching potential.
4.8 Hydrology The principal watercourses are shown on Drawing 796036-0600-D-00081 and listed in Table 4.8-1 along with other water quality information discussed in Section 4.8.1 below lists the principal watercourses migrating throughout the area between Omagh and Aughnacloy. For further details see the POR 2 drainage report.
796036-0600-R-007 33 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Table 4.8-1 Principal Watercourses
Watercourse Name Drainage Catchment Camowen River Camowen Cloghfin River Cloghfin, Seskinore River Quiggery Eskragh Water Quiggery Routing Burn Quiggery River Blackwater Blackwater Ballygawley River Ballygawley There are numerous additional minor water courses in the area, particularly in the Clogher Valley.
4.8.1 Water Quality Northern Ireland Environment Agency (NIEA) monitors the water quality in terms of biological and chemical class on several watercourses within the study area in line with UK standards. The classification scheme for both chemical and biological quality is provided below in Table 4.8-2. More detailed descriptions for these classifications are provided in Appendix E along with the full results of the biological and chemical classifications of the watercourses. The locations of the monitoring points are indicated on Drawing 796036-0600-D-00081.
Table 4.8-2 River Classification Scheme
Chemical & Biological Classification A Very Good B Good C Fairly Good D Fair E Poor F Bad
The chemical classification for all test sites in Sub-Section 3A is noted to be GQA (General Quality Assessment) class A – D, very good to fair with generally improving conditions across the five sites since 2001/2003. In Sub-Sections 3B and 3C the chemical classifications in 2007 were also generally class A-C with the exception of Letfern Burn and Routing Burn. The poor chemical classifications and high biological classifications at these locations would suggest organic pollution in the watercourse such as a sewage or manure spill.
796036-0600-R-007 34 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
The Biological GQA categorises most of the sites within Section 3 between 2001 and 2007 as class A-C, very good to fairly good. The exceptions are Stroancarbadagh Burn in Sub-Section 3A and Ballygawley River and Lissenderry Feeder in Sub- Section 3C where the biological classification of fair indicates polluted watercourses.
4.8.2 River Pollution Incidents The NIEA have confirmed a total of 53 pollution incidents 2 of which are classified as incidents of high severity, 12 of medium severity and 39 incidents of low severity. The high and medium pollution incidents are detailed in Table 4.8-3 below and their locations indicated on Drawing 796036-0600-D-00082. Details of all the river pollution incidents are provided in Appendix E. These appear to largely relate to sewage or farm effluent spills.
Table 4.8-3 Summary of River Pollution Incidents
River Pollution Incident Easting Northing Severity Omagh – Gortaclare/Seskinore (Sub-Section 3A) Pollution at Moylagh Road, Beragh 251700 364600 Medium Farm Effluent into Letfern at Moylagh 250500 363700 Medium Stream from Letfern Burn, Seskinore River 251400 363600 Medium Farm yard pollution into river at Augher Point Road 251521 364016 Medium Seskinore/Gortaclare – Ballygawley (Sub-Section 3B) Farm effluent in waterway at Greenmount Road, Beragh 252300 362300 Medium Vehicle wash run off from Ballynasaggart Road, 260200 358200 Medium Ballygawley Effluent escape 260700 357700 Medium Discharge from Ballygawley Pork 260700 357600 Medium Pollution 260700 357600 Medium Clogher Valley & Aughnacloy (Sub-Section 3C) Ballygawley Water badly polluted 262300 356900 Medium Dead fish in Ballygawley Water 261400 357800 Medium Pollution of Ballygawley Water tributary 260801 357587 High Dead fish in Ballygawley Water 262900 357400 High Sewage in storm drain at Old Omagh Road, Ballygawley 262600 357700 Medium
4.8.3 Water Abstractions The NIEA provide details of historic groundwater abstractions as detailed in Table 4.8-4 below. Also shown is the vulnerability of the aquifer from which the groundwater was abstracted. There are no current licensed water abstraction points within the area.
796036-0600-R-007 35 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Table 4.8-4 Water Abstractions
Description Easting Northing Vulnerability
Omagh – Gortaclare/Seskinore (Sub-Section 3A) Historic Groundwater Abstraction 245358 363495 Type B - Low Historic Groundwater Abstraction 246824 368124 Type B - Low Historic Groundwater Abstraction 247095 363262 Type B - Low Historic Groundwater Abstraction 248576 366188 Type B - Low Historic Groundwater Abstraction 248260 367584 Type B - Low Historic Groundwater Abstraction 250210 366900 Type B - Low Historic Groundwater Abstraction 250400 367500 Type B - Low Historic Groundwater Abstraction 250640 362950 Type B - Low Historic Groundwater Abstraction 251350 368400 Type B - Low Historic Groundwater Abstraction 251380 368373 Type B - Low Historic Groundwater Abstraction 252300 367900 Type B – High Historic Groundwater Abstraction 252310 367860 Type B – High Historic Groundwater Abstraction 252380 367871 Type B – High Historic Groundwater Abstraction 253327 366378 Type B – Low Seskinore/Gortaclare – Ballygawley (Sub-Section 3B) Historic Groundwater Abstraction 253390 361140 Type B – High Historic Groundwater Abstraction 253465 361150 Type B – High Historic Groundwater Abstraction 253590 364750 Type B – Low Historic Groundwater Abstraction 253600 362900 Type B – Low Historic Groundwater Abstraction 253601 365503 Type B – Low Historic Groundwater Abstraction 253759 365892 Type B – High Historic Groundwater Abstraction 253888 359902 Type B – Low Historic Groundwater Abstraction 254116 361529 Type B – Low Historic Groundwater Abstraction 254650 360830 Type B – Low Historic Groundwater Abstraction 254732 365736 Type B – Low Historic Groundwater Abstraction 254799 362810 Type B – Low Historic Groundwater Abstraction 255700 365710 Type B – Low Historic Groundwater Abstraction 255700 365375 Type B – Low Historic Groundwater Abstraction 255874 359667 Type B – Low Historic Groundwater Abstraction 256060 360310 Type B – Low Historic Groundwater Abstraction 256488 356167 Type B – Low
796036-0600-R-007 36 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Historic Groundwater 258500 358800 Type B – Low Abstraction Clogher Valley & Aughnacloy (Sub-Section 3C) Historic Groundwater Abstraction 259700 355000 Type B – Low Historic Groundwater Abstraction 259700 355900 Type B – Low Historic Groundwater Abstraction 259976 355377 Type B – Low Historic Groundwater Abstraction 260500 355800 Type B – High Historic Groundwater Abstraction 260700 357100 Type B – Low Historic Groundwater Abstraction 261800 355800 Type B – Low Historic Groundwater Abstraction 262700 356400 Type B – Low Historic Groundwater Abstraction 262700 358200 Type B – Low Historic Groundwater Abstraction 263000 355600 Type B – Low Historic Groundwater Abstraction 263217 359024 Type B – Low Historic Groundwater Abstraction 263600 355400 Type B – Low Historic Groundwater Abstraction 266700 352300 Type B – High Historic Groundwater Abstraction 269396 354353 Type B – Low
4.8.4 Consented Discharges to Controlled Waters Table 4.8-5 lists the consented discharges to both groundwater and surface water..
Table 4.8-5 Summary of Consented Discharges to Controlled Waters
Industry Type Discharge description Location Easting Northing
Omagh – Gortaclare/Seskinore (Sub-Section 3A)
Killyclogher Road, Food Processing Discharge from fish farm 249300 373500 Ballinamullan, Omagh.
Discharge from vehicle 114 Carnalea Road, Vehicle Washing 247680 363050 washing Seskinore, Omagh.
Seskinore/Gortaclare – Ballygawley (Sub-Section 3B)
Discharge from sand and Eskragh Road, Eskragh, Minerals 251310 359620 stone washing Omagh.
Discharge from vehicle 135 Curr Road, Beragh, Vehicle Washing 253650 362550 washing Omagh.
Altamuskin Road Private sewage Private Sewage Development, 259900 364000 discharge Sixmilecross, Omagh.
796036-0600-R-007 37 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Industry Type Discharge description Location Easting Northing
Discharge from sand and Mullans Quarry, 203 Minerals 260900 363300 stone washing Altamuskin Road, Sixmilecross, Omagh. Clogher Valley & Aughnacloy (Sub-Section 3C) Private sewage 20 Corrck Road, Corick, Private Sewage 254700 353400 discharge Clogher.
Discharge from Food Processing Main Street, Augher. 256300 353900 creamery
Haddens Quarry / Discharge from non-inert Tullyvar Waste Disposal Waste Disposal Site 262500 353000 waste disposal site Site, Derrymeen Bridge, Aughnacloy.
Private sewage 64 Armaghlughey Road, Private Sewage 264860 356770 discharge Ballygawley
The consented discharge from the Tullyvar landfill is the most significant.
4.9 Other Statutory Consultee Responses Statutory and non-statutory authorities identified in Section 2.1 were contacted to obtain additional relevant geological, environmental and public register information. Copies of the responses received from the statutory consultees are included in Appendix F. The locations of all identified constraints reported by the statutory consultees are shown on Drawing 796036-0600-D-00083. A summary of the pertinent information within the study area is included in the following sections.
4.9.1 Man-made Features / Contaminated Sites Potentially contaminated sites as identified by the NIEA Land Quality database, Tyrone and Dungannon Council offices and identified from historical mapping are shown in the GIS model within Drawing 796036-0600-D-00083. These sites have been assessed by Mouchel and assigned a risk rating according to the perceived level of potential contamination associated with the land use. A summary of the main land uses identified within the Preferred Corridor together with associated risk ratings is given in Table 4.9-1.
Table 4.9-1 Summary of Potentially Contaminated Land Uses within Section 3 with Risk Rating
Land Use Risk Rating Number of sites Section Section Section 3A 3B 3C Landfill High 0 0 2
Petrol Station/Fuel Storage High 1 4 10
Mineral Works Medium 13 72 22
Engineering Works Medium 0 0 1
796036-0600-R-007 38 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Sewage Works Medium 7 8 26
Joinery Works Medium 0 1 3
Railway Land Medium 1 0 2
Textile Works (flax/linen) Low 2 3 3
Food Preparation/Processing (mostly Low 13 9 9 corn mills) Reclaimed Land (miscellaneous- Low 35 37 59 mostly infilled sand and clay holes)
It should be noted that the risk rating given is in relation to the potential nature and scale of contaminants that may be present. Assessment of the pathway – receptor linkage has not been carried out at this stage.
4.9.2 Contaminated Land There are a number of disused mills and kilns located throughout the area. Historically these would have been largely water powered corn and flax mills which should present a low risk to ground contamination, though there may have been some fuel storage and possible accidental spillage of chemicals in storage areas or during processing.
Several petrol stations/fuel storage areas are located throughout the area including a petrol station at Moylagh, Garvaghy and around Aughnacloy which may present associated hydrocarbon contamination.
A significant high risk contamination site within Section 3 is the active landfill site at Tullyvar and a reclaimed landfill site to the east of Aughnacloy. Potential contamination will depend on the history of the site and the range of materials handled there. Tullyvar is a licensed Hazardous Waste landfill. Potential hazards include landfill gas which may vent to the atmosphere or migrate into ground around the landfill and leachate breakout to surrounding ground or into the groundwater.
The disused Clogher Valley railway roughly extends through Sub-Section 3C running east from Clogher to Ballygawley and then south to Aughnacloy and the ground may potentially have associated ash & cinder contamination.
Several wastewater treatment sites are located throughout Section 3 close to the main residential areas including Gortaclare, Garvaghy, Ballygawley and Aughnacloy which may present a medium to low contamination risk to adjacent ground and water.
796036-0600-R-007 39 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
4.9.3 Mineral and Petroleum Exploration The GSNI has confirmed there is no oil or gas exploration within the study area. No coal or metal workings have been exposed in the area, though some mineral veins are shown on the 1:50,000 geological maps.
There are two significant areas of active sand and gravel extraction occurring, namely at Eskragh and close to Altamuskin as shown on Drawing 796036-0600-D- 00083. There are also a large number of disused quarries throughout the area particularly within the limestone of the high ground to the east around Aughnacloy. These may have been backfilled and reclaimed with unknown material and therefore have the potential to contain contamination and/or poor geotechnical properties. A summary of the quarries and their status within the area is shown below in Table 4.9-2.
Table 4.9-2 The status of Quarries throughout Section 3
Number of sites
Quarry Description Omagh – Seskinore/Gortaclare – Clogher Valley & Gortaclare/Seskinore Ballygawley (Sub- Aughnacloy (Sub- (Sub-Section 3A) Section 3B) Section 3C)
Backfilled 36 82 62 Disused 8 14 17 Active 0 7 0
4.9.4 Industrial Installations The NIEA Industrial Pollution Unit regulates and controls the activities of industrial activities under The Pollution Prevention and Control Regulations (Northern Ireland) 2003. Part A of the regulations takes into account a wide range of environmental issues whilst Parts B and C control emissions to air only. Part C processes are controlled by District Councils. Table 4.9-3 summarises the industries with current Part A, B or C permits. Part A and B details have been provided by NIEA with Tyrone and Dungannon District Councils providing information on Part C processes.
Table 4.9-3 Part A, B and C Industrial Processes
Industry Permit Site Operator Address
Omagh – Gortaclare/Seskinore (Sub-Section 3A)
796036-0600-R-007 40 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Food Processing A or B F Charlton – Poultry Unit F Charlton Poultry Unit, 41 Curr Road, Beragh, BT79 0UW Seskinore/Gortaclare – Ballygawley (Sub-Section 3B)
Food Processing A or B C Rainey – Poultry Unit C Rainey Poultry Unit, 368 Curr Road, Ballygawley, BT70 2EG. Food Processing A or B S Bell – Poultry Unit S Bell Poultry Unit, 49 Garvaghy Hill, Ballygawley, BT70 2EF. Clogher Valley & Aughnacloy (Sub-Section 3C)
Industrial Pollution A Tullyvar Landfill Site Tullyvar Landfill Site, (Pending) 130 Tullyvar Road, Aughnacloy BT69 6BN Feed Producer C T J Booth Feeds T J Booth, Ballynanny Road, Ballygawley, BT702LZ Feed Producer C Boyd’s Feeds Boyds Feeds, Clogher Mart, Station Road, Clogher, Co. Tyrone, BT6 OAH Petrol C Poundhill Filling Station Poundhill filling station 2 Moore Street, Aughnacloy, BT69 6AY
4.9.5 Environmental Considerations An Environmental Assessment Report (EAR) is being prepared for the scheme which will detail the impacts of the scheme on the study area. This report should be consulted for in depth environmental information.
A number of sites exist across Section 3 which have been identified as part of the Earth Science Conservation Review by Habitas to be of geological interest and are summarised in Table 4.9-4.
796036-0600-R-007 41 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Table 4.9-4 Habitas Sites
Site Features
South of Omagh to Gortaclare / Seskinore (Sub-Section 3A)
Murrins Complex Area between Beragh and Gortaclare characterised by a series of eskers up to 1km long, 5-10m high and 10-40m wide. Gortaclare / Seskinore to Ballygawley (Sub-Section 3B)
Ballygawley Delta To the north and northwest of Ballygawley this complex is characterised by Complex deltas and outwash deposits of sand and gravel. Fintona Hills Complex Between Fintona and Roscavey, the Fintona Hills Complex shows a variety of ice marginal and subglacial landforms such as esker ridges and kame terraces. Clogher Valley & Aughnacloy (Sub-Section 3C)
Plaister Quarry Situated northeast of Aughnacloy, Plaister Quarry is a disused quarry exposing a small thickness of limestone from the Maydown Formation. Drummond Quarry This abandoned and flooded quarry located to the east of Aughnacloy is the only quarry in Northern Ireland excavated entirely into the Bundoran Shale Formation.
796036-0600-R-007 42 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
5 Ground Conditions
5.1 Anticipated Soils Historical ground investigation information obtained from GSNI and CPD, published geological maps and information from a Preliminary Ground Investigation undertaken by Mouchel form the basis for the ground conditions described in this section.
Although limited historical ground investigation information exists for the area south of Omagh to Ballygawley (Sub-Sections 3A & 3B) more detailed information on ground conditions exists for sub-section 3C from a recent ground investigation undertaken as part of the A4 Annaghilla Road and A5 Tullyvar 2+1 road improvements.
All historical borehole logs and test results are hyperlinked within the ARC Reader (GIS) Model on Drawing 796039-0600-D-00062. Logs and corresponding test results for the Preliminary GI are also included in the Draft Factual Report (Ref Y9901), and on Drawing 796039-0600-D-00067. Geological long sections produced for sub-section 3C on drawings 796036-0600-D-30011, 796036-0600-D-30012 and 796036-0600-D-30013 are presented in Appendix B.
The following table 5.1-1 below summarises the geological deposits encountered and material thickness for Section 3.
Table 5.1-1 Summary of Ground Conditions
Strata Depth (m) Thickness Notes bgl (m) South of Omagh to Gortaclare / Seskinore (Sub-Section 3A)
Encountered in 3 exploratory holes River Alluvium 0 – 11.0 11.0 Maximum depth of 11m recorded in CP01S
Encountered in 2 exploratory holes Maximum depth of 9m recorded in SI138SW/5 Peat 0 – 9.0 0.8 – 9.0 Soft ground anticipated to be peat encountered in 8 dynamic probe tests to a maximum depth of 4.5m in DP38S.
Encountered in 14 exploratory holes Glaciofluvial Sands and 0.2 – 11.5 0.5 – 3.4 Gravels Maximum depth of 3.4m recorded in WS10S
Encountered in 14 exploratory holes Glacial Till 0.5 – 18.0 2.0 – 17.5 Maximum depth of 17.5m recorded in BH01S (depth varies depending on position on drumlins)
796036-0600-R-007 43 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Encountered in 15 exploratory holes Bedrock 2.5 – 22.0 3.5 + Shallowest depth to rock encountered is 2.5m in SI138SW/5
Gortaclare / Seskinore to Ballygawley (Sub-Section 3B) Encountered in 3 exploratory holes River Alluvium 0.1 – 4.1 1.1 – 4 Maximum depth of 4m recorded in WS16S
Soft ground anticipated to be lake alluvium encountered in 1 dynamic probe Lake Alluvium 0 – 2.0 2.0 test to a maximum depth of 2.0m in DP03S.
Encountered in 1 exploratory holes (WS12S) Peat 2.3 – 2.9 0.6 Soft ground anticipated to be peat encountered in 14 dynamic probe tests to a maximum depth of 3.5m in DP33S.
Encountered in 4 exploratory holes Glaciofluvial Sands and 0.2 – 3.5 3.3 Gravels Maximum depth of 3.3m recorded in WS15S
Encountered in 1 exploratory holes Glacial Till 0.2 - 14 0.5 – 8 Maximum depth of 8m recorded in BH02S
Encountered in 1 exploratory holes Bedrock 1.3 - 18 4 + Shallowest depth to rock encountered is 1.3m inDP06S Clogher Valley & Aughnacloy (Sub-Section 3C)
Encountered in 36 exploratory holes Made Ground 0 - 4 4 Maximum deoth of 4m recorded in SI Y5002D TTP205B
Encountered in 14 exploratory holes River Alluvium 0.3 – 9.1 2.7 – 8.8 Maximum depth of 8.8m recorded in
Encountered in 2 exploratory holes Maximum depth of 0.3m recorded in WS13S Peat 1.3 – 1.6 0.3 Soft ground anticipated to be peat encountered in 11 dynamic probe tests to a maximum depth of 2.4m in DP11S
Glaciofluvial Sands and 0 – 4.5 1.1 – 2.0 Encountered in 7 exploratory holes Gravels
Encountered in 2 exploratory holes Glacial Till 0.1 – 5.0 0.5 – 3.8 Maximum depth of 3.8m recorded in WS19S (depth varies depending on position on drumlins)
Encountered in 9 exploratory holes Bedrock 1.0 – 85.0 76 + Shallowest depth to rock is 1m
796036-0600-R-007 44 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
5.2 Made Ground Although made ground was not recorded in ground investigation records available for the area south of Omagh to Ballygawley the presence of these materials should not be discounted and can be expected where roads have been improved and land levelled for development. Made ground was identified in a number of exploratory holes within the area south of Ballygawley (Sub-Section 3C), during a recent preliminary ground investigation within WS04S adjacent to the active landfill at Tullyvar, adjacent to an historic landfill east of Aughnacloy within WS08S, in BH02S southeast of Garvaghy and within WS19S southwest of Ballygawley.
Made ground was also encountered in six exploratory holes pertaining to a previous ground investigation undertaken for the A4/A5 Corridor Improvement Scheme at Annaghilla and Tullyvar. The exploratory holes were carried out close to the existing road network therefore it is likely the made ground, generally comprising gravels, is residual road construction materials or infill material from the road construction.
This material was encountered to a thickness of between 0 and 4m and was present from ground level to 4.0m bgl. It was generally described as either soft to firm brown sandy gravelly silt / clay or medium dense red brown slightly clayey, sandy, silty fine to coarse sand / gravel. A summary of the test results obtained for the made ground are provided in Long sections 796036-0600-D-30011, 796036-0600-D-30012 and 796036-0600-D-30013 in Appendix B illustrate the extent of these deposits.
Table 5.2-1 Geotechnical properties of Made Ground . Six samples were tested for natural moisture content resulting in an average value of 16.6%. Atterberg tests indicate the material to be variable and of low to high plasticity.
Figure 5.2-1 shows SPT N value plotted against depth and illustrates the variable nature of the made ground, though it is generally of firm – stiff consistency, or better. Long sections 796036-0600-D-30011, 796036-0600-D-30012 and 796036-0600-D- 30013 in Appendix B illustrate the extent of these deposits.
Table 5.2-1 Geotechnical properties of Made Ground
No. of tests Min Mean Max Natural moisture content (%) 6 7.8 16.6 29.8 Liquid Limit (%) 6 28 37 71 Plastic Limit (%) 6 15 18 36 Plasticity Index (%) 6 6 18 35
796036-0600-R-007 45 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Figure 5.2-1 SPT N Value vs depth for Made Ground
SPT N value 0 20 40 60 80 100 0
1
2
3
4 Depth(m)
5
6
7
8
5.3 Superficial Soils 5.3.1 Peat Peat generally described as pseudo-fibrous black sandy peat was encountered in 38No of exploratory holes throughout the area. As identified in section 4.3 peat to the north of the section occurs in the form of raised bog and within inter-drumlin areas. Further South between Gortclare and Ballygawley, peat occurs in the form of blanket peat associated with the high ground and to the south as low level peat accumulations between drumlins.
796036-0600-R-007 46 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Several areas of peat were identified between Omagh and Gortaclare, To the north of the section is the raised (2m+ agl) peat bog to the north-east of Tattykeel where historical ground investigation has confirmed peat up to 9m bgl however with no consistency or strength description of the material. Recent in-situ density tests show the organic peat to be very soft with a dynamic probe blow count of less than 5.
An extensive area of raised peat bog lies south of Tullyrush. Here, walkover surveys have revealed the peat protrudes to a maximum of 8m above the surrounding ground level and is described as firm and pseudo-fibrous with a partially sandy consistency.
Between Gortaclare / Moylagh and Ballygawley, peat is typically restricted to the very high ground to the east. On Slievemore and Slievedivena, extensive blanket peat bogs are present up to 2.5m deep. To the southeast of Garvaghy an area approximately 800m in length was identified as very soft ground extending to 4m in depth during insitu tests and is likely to be peat according to geological mapping.
South of Ballygawley, peat is limited to inter-drumlin areas within the Clogher Valley. This peat is not extensive, but the thickness can be highly variable and locally significant.
Table 5.3-1 summarises data obtained for peat from historical ground investigations.
Table 5.3-1 Geotechnical properties of Peat
No. of tests Min Mean Max Natural moisture content (%) 1 200 200 200 Liquid Limit (%) 81 22 40 113 Plastic Limit (%) 80 12 20 71 Plasticity Index (%) 80 10 19 52 It should be noted that index properties of peat are not always meaningful, due to the fibrous nature of the material.
5.3.2 River Alluvium Alluvium was encountered in low-lying areas within the vicinity of rivers and streams throughout the area. In the north, alluvial deposits associated with a tributary of the Camowen River were identified during in-situ field tests and show medium dense becoming very dense sand present to a depth of 5m. At Moylagh, further in-situ testing reveals alluvial deposits associated with a tributary of the Quiggary Water extending to a depth of 11m. The material is described as fine grained with occasional bands of medium dense sandy silt becoming very dense sand. In-situ density testing of the same tributary within the vicinity of Gortaclare / Moylagh, show soft material to a depth of 4m.
796036-0600-R-007 47 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Between Gortaclare / Moylagh and Ballygawley, alluvial deposits are shown along the main watercourses and tributaries of the Routing Burn, Eskragh Water and Camowen River. The alluvial floodplain associated with the east to west flowing Routing Burn is approximately 100m wide and ground investigations reveal firm sandy gravelly silts and dense sands to a depth of 4m.
In-situ density tests along the Routing Burn floodplain show soft / loose deposits extending to a depth of approximately 3m. These deposits are likely to be alluvial in nature according to the geological mapping. Around Ballymackilroy, alluvial material is described as medium dense sand and firm sandy gravelly silt and is present to depth of 4.15m which is supported by in-situ density tests.
The Eskragh Water in the west of the area has an associated 20 to 30m wide alluvial floodplain. The alluvial floodplain of the Camowen River in the east extends to 100m wide.
The Ballygawley Water and River Blackwater and their associated alluvial floodplains dominate the south of the area. The River Blackwater has an extensive floodplain comprising material of variable nature, stiff sandy silt and very stiff fine grained material. In-situ density testing shows soft / loose material extending to 3m which is likely to be alluvial deposits according to geological mapping. The Ballygawley Water alluvial material comprises very dense sand to depths of 2-3m.
Table 5.3-2 summarises the known properties of the river alluvium within Section 3. The high variation in properties, as shown for moisture content in
796036-0600-R-007 48 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Figure 5.3-1, is characteristic of the changeable nature of the material with SPT results likely to be influenced by the high gravel content.
Table 5.3-2 Geotechnical properties of River Alluvium
No. of tests Min Mean Max Natural moisture content (%) 20 5.3 16 31 Liquid Limit (%) 4 24 29 34 Plastic Limit (%) 3 14 16 18 Plasticity Index (%) 4 0 11 16 SPT “N” value 8 6 26 58
796036-0600-R-007 49 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Figure 5.3-1 Moisture content v depth for River Alluvium
5.3.3 Lake Alluvium Soft material identified during in-situ density testing at Rarone is likely to be lake alluvium to a depth of 2m. Historical field surveys of the area describe the material as soft brown clay. Further patches of lake alluvium are located sporadically across the northwest of Section 3.
5.3.4 River Terrace No significant areas of river terracing were identified in the section.
5.3.5 Glacial Till Glacial Till is found extensively across the section and is the dominant drift geology type. The ground investigation revealed the till varies in thickness between 1m and 18m. Thickness is largely a function of the position of exploratory holes on the side / top of drumlins.
796036-0600-R-007 50 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
In the north, between south of Omagh and Gortaclare / Moylagh the glacial till is described as firm becoming stiff with depth, red brown gravelly sandy silt and clay. The material becomes increasingly gravelly with depth and also contains numerous cobbles and boulders. The measured glacial till varies in depth between 2m and 3.5m though is likely to be significantly more on drumlins.
Between Gortaclare / Moylagh and north of Ballygawley and to the east, the glacial till is described as firm becoming stiff with depth brown sandy gravelly silt and clay. The glacial till varies in depth between 0m and 5m. Rock is predominantly at or close to the ground surface in this area and limited information is available for glacial till. In-situ density tests show firm to stiff material.
From north of Ballygawley to Aughnacloy, glacial till is described as firm becoming stiff with depth, grey / brown sandy gravelly silt and clay. The material varies in depth between 1.8m and 5m. Again, this could be much greater on the drumlins.
Glacial Till deposits are extensively shown on Drawings 796036-0600-D-30011, 796036-0600-D-30012 and 796036-0600-D-30013 in Appendix B in the area of Annaghilla and Tullyvar in Sub-Section 3C as part of the A4/A5 ground investigation.
Glacial till properties across the section vary and are summarised in Table 5.3-3.
Table 5.3-3 Geotechnical properties of Glacial Till
No. of tests Min Mean Max Natural moisture content (%) 133 3.4 16.9 70 Liquid Limit (%) 85 22 39 81 Plastic Limit (%) 94 11 19.8 71 Plasticity Index (%) 108 0 18 52 SPT “N” value 345 2 31 129 Max Dry Density 8 1.69 1.93 2.18 Optimum Moisture Content 85 7.5 10 20
Plasticity index values range between 0 and 52 with an average value of 18, classifying the material as intermediate plasticity clay.
Moisture content was found to vary as shown in Figure 5.3-2 with an average of 20% at a depth of 2m reducing to 10% at a depth of 3m below ground level. Historical records show moisture content of 10% for optimum compaction during re-use of the material, though this seems abnormally low. The natural moisture content is significantly wetter than this in the uppermost 2m.
796036-0600-R-007 51 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Figure 5.3-2 Moisture content v depth for Glacial Till
SPT ‘N’ values within the till range from 2 to 129 with an average value of 35.
796036-0600-R-007 52 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Figure 5.3-3 shows ‘N’ values plotted against depth. A very high scatter is evident and may be affected by the presence of cobbles/boulders, though a general reduction in N-value is apparent in the topmost 5m.
Using the Stroud & Butler relationship of Cu = 5N (approx for till) a design line for clay consistency would be around
Cu = 40kPa at 0m
Cu = 75kPa at 2m
Cu = 150kPa at 6m
Cu=200kPa at 10m
796036-0600-R-007 53 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Figure 5.3-3SPT N value v Depth
5.3.6 Other Outwashes of glaciofluvial sands and gravels are noted across the section.
Between south of Omagh and Gortaclare / Moylagh, sand and gravel mounds are noted to the east at Tattykeel and Coolesker. Ground investigation within this area revealed the material to comprise medium dense brown gravelly silty fine to medium sand. Grey sand deposits are located west of Seskinore.
796036-0600-R-007 54 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
At Garvaghy, between Gortaclare / Moylagh and north of Ballygawley, the material is described as medium dense becoming very dense with depth, brown slightly silty slightly gravelly fine to coarse sand. These deposits are up to 3.5m deep. Extensive sand and gravel deposits are noted around Eskragh in the west, which are described as up to 3.6m deep unsorted red sand and gravel. Large scale commercial extraction of these deposits is noted at Eskragh. At Knockmany, outwash deposits of sand and gravel lenses with pebble bands are noted up to 4.5m deep. Extensive sand and gravel deposits occur north of Ballygawley, described as clayey red fine sands.
In the south of the section, between Ballygawley and Aughnacloy, sand and gravel deposits are found at Augher and Clogher. Historical borehole records show this material to comprise fine to medium coarse sandy gravel to a depth of 10m below the ground surface. Glaciofluvial deposits are also located northeast of Aughnacloy. Historical records show these deposits to comprise red sands and gravels.
A summary of the data available for glaciofluvial sands and gravels is given in Table 5.3-4.
Table 5.3-4 Geotechnical properties of Glaciofluvial Sands and Gravels
No. of tests Min Mean Max Natural moisture content (%) 23 4 13.2 39 SPT “N” value 4 4 24 52
5.4 Bedrock The preliminary ground investigation does generally not attempt to establish a weathering profile of the bedrock. Termination of the holes occurred when bedrock was encountered with the exception of two rotary boreholes.
5.4.1 South of Omagh to Gortaclare / Moylagh To the south of Omagh the area is predominantly underlain by sandstone of the Shanmullagh Formation. Weathered bedrock is found from ground surface in parts though typically at 3-4m below ground surface with intact material recorded at depths of between 7m and 13m. Weathered material is generally described as gravel consisting of shale, siltstone and a little sandstone with open vertical fissures. Bedrock is generally described as hard fine red sandy mudstone and, in the north, hard grey sandstone.
796036-0600-R-007 55 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
5.4.2 Slievemore Ridge Geological mapping shows the Slievemore ridge to comprise sandstone rock of the Gortfinbar Conglomerate Formation. Accordingly, at the south of the ridge the ground investigation identified strong interbedded red brown conglomerate comprising gravel of igneous rocks, sandstone and siltstone, at a depth of 15m below ground level within a borehole through a drumlin. However a ground investigation at the north of the ridge revealed limestone from a depth of 19m below ground surface. The limestone is described as strong, locally very strong, brown grey with subvertical discontinuities.
5.4.3 Ballygawley – Aughnacloy Historic ground investigations in this area confirm the structure of the geological map (solid edition) and indicate the area to be underlain by rocks of the Carboniferous Period, primarily from the Maydown Limestone Formation and Clogher Valley Group.
In the west, around Augher and Clogher, rock from the Clogher Valley Group is predominant. Records generally describe the bedrock as broken limestone found at a depth of 6m below ground surface.
Around Ballygawley in the east, bedrock is shown to be shallow at a typical depth of 5m below ground surface. It is described as dark grey fine grained carboniferous rock and is likely to be part of the Maydown Limestone Formation. This rock type emerges again in an extensive area north of Aughnacloy. Here the rock is present from 1m below the ground surface and is generally described as dark grey argillaceous limestone and extends to depths of 45m - 60m. A 10m thick layer of mudstone was recorded between depths of 30-40m below ground surface.
To the west of Aughnacloy, black shale was recorded from ground surface to a depth of 60m.
5.5 Groundwater Groundwater strikes have been recorded from historical ground investigations and monitoring as part of the recent Preliminary Ground Investigation is on-going. Therefore at this stage no long term monitoring has been carried out and the following results should be used as an indication only of possible groundwater regimes. Table 5.5-1 summarises the groundwater strikes and monitoring results from the Preliminary ground Investigation.
796036-0600-R-007 56 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Table 5.5-1 Groundwater strikes and monitoring results form Preliminary Ground Investigation
Exploratory Hole Date Water Level Water Bearing Comments Reference (m BGL) Stratum South of Omagh to Gortaclare / Seskinore (Sub-Section 3A) 13 March 2009 2.10 * Silt SP installed to 3.4m WS01-S 19 March 2009 1.83 Silt
3 April 2009 2.03 Silt WS10-S 13 March 2009 0.20 * Sand WS11-S 16 March 2009 2.20 * Silt WS02-S 16 March 2009 1.00 * Silt 16 March 2009 1.80 * Gravel SP installed to 2m 19 March 2009 0.92 Clay WS20-S 3 April 2009 0.98 Clay 9 June 2009 1.16 Clay 16 March 2009 1.40 * Gravel SP installed to 2.22m 19 March 2009 Silt WS03-S 0.82 3 April 2009 0.86 Silt 9 June 2009 0.97 Silt 16 March 2009 2.40 * Silt SP installed to 3.2m WS05-S 19 March 2009 2.70 Silt
3 April 2009 2.70 Silt 4 March 2009 Dry - SP installed to 22m
19 March 2009 2.96 BH01-S Clay 3 April 2009 2.61 Clay 9 June 2009 3.30 Clay Gortaclare / Seskinore to Ballygawley (Sub-Section 3B) 17 March 2009 2.90 * Sand Sp installed to 4.05m 19 March 2009 4.05 Silt WS15-S 3 April 2009 3.90 Silt 9 June 2009 3.58 Silt WS16-S 17 March 2009 2.80 * Silt 5 March 2009 13.0 * Clay SP installed to 18m BH02-S 17 March 2009 1.80 Made ground
9 June 2009 2.72 Made ground Clogher Valley & Aughnacloy (Sub-Section 3C) 17 March 2009 2.80 * Sand SP installed to 4.3m 19 March 2009 4.05 Silt WS13-S 3 April 2009 3.90 Silt 9 June 2009 3.58 Silt 18 March 2009 1.10 * Sand SP installed to 3.4m 19 March 2009 0.49 Made ground WS19-S 3 April 2009 0.42 Made ground 9 June 2009 0.64 Made ground WS08-S 18 March 2009 2.90 * Silt WS09-S 19 March 2009 3.50 * Silt WS18-S 19 March 2009 4.10 * Silt * indicates water strike during drilling 796036-0600-R-007 57 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Within the extensive peat area to the south of Omagh, standing water levels in boreholes were recorded historically at 1-3m below ground surface. Elsewhere in the east between Omagh and Gortaclare, recent ground investigation has also identified groundwater at depths of 1-3m below ground surface within the glacial material in WS05-S and WS20-S. To the west of this area groundwater levels were a little higher, recorded at depths of 1-2m below ground surface, typically within silt in WS01-S and WS03-S. Post drilling monitoring has shown the groundwater levels to initially rise slightly before equilibrating to natural groundwater levels of 1-2m below ground surface.
Across the sandstone ridge, limited information is available with groundwater strikes typically varying in depth between 2-3m below ground surface. On the lower slopes of Slievemore, groundwater was struck in BH02-S at a depth of 13m below ground surface, close to the bedrock level. Three months post drilling, this groundwater level has risen to 2.7m below ground surface.
In the south, at Ballygawley, a slight groundwater flow was noted at a depth of 2.35m within a borehole close to the Ballygawley Water during a historical ground investigation in 1988 resulting in standing water level at 1.7m below ground surface. Groundwater was encountered during the Preliminary Ground Investigation in WS19- S close to the Ballygawley Water at a depth of 1.1m which during subsequent monitoring has equilibrated at a level 0.5m below ground level.
At Augher and Clogher, groundwater was noted within the sand and gravel bands at varying depths between 1.5-4m below ground level. To the south around Aughnacloy, groundwater strikes were encountered either within the glacial material at typical depths of 3-4m below ground surface in WS08-S, WS09-S and WS18-S or were found historically at depths of 6-10m within the bedrock.
5.6 Contaminated Land A number of areas of made ground were identified in Section 5.2 however it is likely the made ground, generally comprising gravels, is residual road construction materials and therefore no significant contamination is suspected. Chemical analyses of samples from the areas reveal no elevated levels of contaminants within the ground, with values within Soil Guideline Values for residential use.
Not all the potentially contaminated sites identified have been comprehensively investigated however.
796036-0600-R-007 58 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
6 Preliminary Engineering Assessment
The following assessment is specific to the preferred corridor identified, though the principles could be extended to any corridor within the engineering study area.
6.1 Superficial Soils The information provided below is based on the results from the preliminary A5 ground investigation undertaken in February 2009, previous GSNI and CPD ground investigations of the area and past engineering experience of working in locations with similar ground conditions.
6.1.1 Made Ground Made Ground deposits will be locally encountered along the chosen route alignment. Due to the variability of the Made Ground, it may be necessary to remove or stabilise the material prior to placing the pavement foundation. Made Ground deposits are not considered suitable for reuse as an earthworks material unless proved otherwise by testing.
6.1.2 Peat Two Significant deposits of peat are present north of the section from Omagh to Ranelly up to 9m deep with sporadic pockets of peat located elsewhere throughout the section, typically 2-3m deep. In-situ density testing and the engineering parameters available show the material to be very soft consistency, with a high moisture content and therefore likely to be highly compressible, with low shear strength. Peat can undergo large secondary consolidation settlements continuing over lengthy time periods therefore incurring significant maintenance issues and costs. The material is an unstable platform for earthworks and is unsuitable for re- use in the works.
For shallow deposits of peat up to 4m deep, it is likely to be more economical to excavate and replace with granular material/rock fill to create a stable platform for embankments. Where peat extend deeper than 4m and it is not economical to replace the poor material, expensive measures to engineer across these deposits may be required such as a piled and basally reinforced platform.
The primary option with peat should be to adjust the horizontal alignment to avoid these areas which are costly to construct and have long term maintenance problems.
796036-0600-R-007 59 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
6.1.3 River Alluvium Tracts of low lying soft alluvium associated with watercourses and floodplains are expected throughout the area with significant deposits expected to be encountered on the principal watercourses such as the Ballygawley River and River Blackwater floodplains. This material comprises soft clay / silt and sand of varying density from loose to dense which is slightly silty and gravelly in places and is found up to 11m deep. There may also be a significant organic content. Alluvium is likely to prove a difficult foundation material for earthworks / pavement and may be too wet or variable to yield anything other than Class 4 (landscape) fill. The weak material also gives rise to settlement issues and if not excavated and replaced with rock fill or overdug to reach a stable formation then techniques such as surcharging or band drains to accelerate settlement should be considered. Where deep alluvial deposits occur at the sites of bridge structures piled foundations will be required either working in shaft friction in the glacial till or end bearing in the underlying rock.
While the above comments are generally the case for alluvium, preliminary investigations have indicated that in many cases, only the upper 3m are soft or variable and below that Alluvium is either absent or formed of medium dense to dense sand. If the variable upper layers can be removed/replaced, spread foundations might be feasible, though thorough ground investigation to confirm consistency will be required.
6.1.4 Lake Alluvium Lake alluvium comprising soft brown clay is likely to have similar foundation issues to river alluvium. The weak soils are found at Rarone in Sub-Section 3A up to a depth of 2m below ground level. These deposits are unsuitable to support structure foundations or earthworks and would give rise to significant settlements unless replaced.
6.1.5 Glacial Till A variable thickness of glacial till is anticipated across the section. In general, deposits range from around 2-5m bgl extending up to 20m bgl within the drumlins. A thin cover of till is likely where rock is in close proximity to the surface, particularly across the Slievemore sandstone ridge.
Glacial till generally comprises low permeability clay or silt matrix with variable sand and gravel deposits. The material throughout the area is typically described as red brown gravelly sandy silt and clay. Sand is fine to coarse and gravel is subangular to subrounded fine to coarse of mixed lithologies. Visual evidence where drumlins have been excavated in the area is that clasts up to 100-150mm diameter are typically present.
Using the relationship between plasticity index and angle of shearing resistance suggested by Sladen and Wrigley (1983), assuming an average plasticity index of 18 would give a φ’ value of 30°.
796036-0600-R-007 60 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Shear strength has been conservatively correlated with SPT ‘N’ values using the relationship suggested by Stroud and Butler where cu = 5N based on a plasticity index of 18. The results indicate a high degree of scatter, but generally a firm consistency (c u=70kPa) above 3m depth, and very stiff (c u=135kPa) below 3m depth.
A moderately conservative design line would be
Cu = 40kPa at 0m
Cu = 75kPa at 2m
Cu = 150kPa at 6m
Cu=200kPa at 10m
Shallow foundations are expected to be suitable for structures founded on glacial till at 3m or greater depth.
The moisture contents were found to vary with an average of 20% at a depth of 2m reducing to an average of 10% at a depth of 3m below ground level.
In general, the glacial till should yield class 2C (stony cohesive) fill, though the moisture content is likely to be variable and may require reconditioning treatment to lower the moisture content before classifying for reuse. Initial estimates, based on this and evidence from the A4/A5 works are that around 60% might be suitable for re-use above 2m depth and 85% suitable below 2m.
6.1.6 Other Areas of sand and gravel encountered across the section typically comprise medium dense, becoming very dense with depth, red brown gravelly silty fine to coarse sand in layers up to 3.4m thick. Shallow foundations are likely to be suitable in this material for most highways structures. The sand and gravel is likely to be a good aggregate source for re-use during the construction works generating Class 6 granular fill.
6.1.7 Rock In the north of the section and across the Slievemore ridge, bedrock consists of hard red sandy mudstone with open vertical fissures, hard grey sandstone and conglomerate of greywacke and sandstone. It is likely this rock will be prone to fragmentation, therefore it is anticipated that 50% would yield Class 6 aggregate and the remainder Class 1.
South of Ballygawley, limestone is the primary rock type most of which is likely to provide good quality Class 6 aggregate. Information on the quality of the limestone is limited at this stage therefore the excavation techniques which may be required is uncertain however blasting may be necessary.
796036-0600-R-007 61 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
If founded on rock, pavement and structure foundations will be very good and it may be possible to dispense with a pavement capping layer.
6.2 Cuttings Both temporary and permanent rock cutting slopes are likely to stand at steep angles in the region of 1v:1h subject to assessment of joint and bedding orientation. The nature of sandstones is that they are prone to weathering, so steeper slopes are not advised at this stage. At this stage, there is not enough information to make an assessment of the excavatability of the rocks likely to be encountered in any cuttings that may be required. Ripping or breakers may just be feasible in the sandstone, but blasting should not be discounted.
Cut slopes through glacial till are likely to be at 1v:2.5h due to the anticipated high groundwater levels. However, the side slope gradients of earthworks are likely to be refined once information from a route specific ground investigation becomes available. Drainage should be incorporated into any cut slopes at the crest and toe of the slope to aid stability both during excavation and in the long term. Significant cuttings may require mid-level berms to improve stability.
Attention should be given to bands of sand within the glacial till which may be water bearing and require groundwater control methods to prevent collapse of the slope.
Orientated fabrics may be encountered if cuttings are required through drumlins. These fabrics can induce decreased soil strength and friction characteristics in certain directions and therefore safe slope angles may have to be reduced in these areas. Careful observation during cutting will be required.
Sidelong cuts into the toe of slopes tend to be the most sensitive as the toe is unloaded and potentially high groundwater is present. Special attention should be given to these and it may be necessary to slacken slopes to 1:3 in such areas. The potential for high volumes of water percolating through fractured rockhead should also be considered, which can impact on stability.
6.3 Embankments It is anticipated that embankments will be constructed using site won material, namely glacial till and glacio sands and gravels. In general, 1v:2.5h side slopes would be expected to be stable, other than as described above. The ground conditions encountered beneath the embankments are generally likely to consist of glacial till overlying weathered bedrock. Due to the overconsolidated nature of the till this foundation should be adequate with satisfactory settlements.
796036-0600-R-007 62 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Drainage should be installed at the crest of the embankment slopes in order to prevent surface water running down and into the face of the slopes. Ground treatment beneath embankments where embankments cross low-lying ground in alluvial streams and river valleys, staged construction or surcharging of embankments may be required to ensure settlements are within acceptable limits, particularly to control differential settlements at the interface between embankments and structures.
Particular areas of embankment sub-formation treatment may be required if embankments are required to cross areas of Peat. As mentioned in 6.1.2 above this may involve excavation and replacement with granular fill if these materials are not encountered to depths of greater than approximately 4m. There are a number of potential solutions to solve these issues, including load transfer platforms, ground improvement with band drains and staged construction to avoid failure of soft and compressible ground. Any excavations within Peat or alluvium may encounter significant groundwater ingress which would compromise stability, and must be allowed for in design. Drainage will need to be designed for acidic groundwater conditions where Peat is present.
6.4 Subgrade Where the formation is constructed across rock, then a CBR value in excess of 15% is expected and is likely where the alignment crosses the Slievemore ridge and the sandstone bedrock expected within a close proximity to the ground surface reducing/eliminating the need for a capping layer.
Much of the route will be constructed on in-situ or re-worked glacial till. The condition of this is not known, but typically a CBR of around 3% is likely to be achievable. The material is likely to be susceptible to changes in moisture, softening upon contact with surface water and is likely to suffer a reduction in strength upon re-working. Very soft spots may be encountered when crossing inter-drumlin hollows; here additional over-excavation or the use of geotextiles may be required.
In embankment situations, careful selection of fill to use the sandier material at the crest may allow an improved CBR of up to 5%.
To the north of the section, extensive areas of peat occur which is unsuitable as a foundation material. This should be replaced or bridged as discussed above.
6.5 Structure Foundations A large number of structures are anticipated to assist crossing of watercourses and road junctions with retaining structures expected where land constraints do not permit side slopes. The structure foundations adopted will depend on the ground conditions at the particular structure location however the majority of the structures are likely to use spread foundations, founding in either the glacial till or bedrock.
796036-0600-R-007 63 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
For bridge crossings over the main watercourses of the Ballygawley Water and River Blackwater, the shallow alluvial ground conditions are unsuitable for foundations, though there is evidence that below 3m, medium dense sand and gravel is present. Pile foundations will be adequate, though piling in gravel is difficult due to water control. Alternatively spread foundations on the deeper gravels may be possible, though thorough ground investigation will be required to prove consistency of the ground.
Shallow foundations in the glacial deposits may encounter groundwater; this will need to be controlled to limit flows into excavations which could affect stability of side walls if not suitably supported. Should piled foundations be required to be installed through soft material, the effect of negative skin friction and lateral forces induced by surcharge pressures on the loads may need to be considered.
6.6 Contaminated Land The majority of the scheme is to be constructed on greenfield land and there is no evidence to suspect widespread contamination. Section 0 determined a number of areas of made ground however no elevated levels of contaminants within the ground were identified.
A number of isolated fuel storage sites, sewage treatment works and industrial works exist across the corridor which may have associated contamination issues and the disused railway land of the Clogher Valley Railway exists through Section 3C. Table 6.6-1 lists some of the potential contamination issues associated with the above industries as identified by The Department of the Environment Industry Profiles.
Table 6.6-1 Potential contamination identified from Industry Profiles
Industry Potential contamination Garages and Filling Stations Hydrocarbons, oils and solvents Heavy metals Sewage Treatment Works Metals Organic compounds Treatment chemicals Asbestos Railway Land Hydrocarbons, oils and solvents Metals Ash and fill
Engineering Works Chemicals Heavy metals Asbestos
796036-0600-R-007 64 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
The contaminants present on a site will depend on the history of the site and the range of materials handled there. Site specific ground investigations will be required should any of these sites be encountered, to identify the nature and extent of any contamination.
There are several disused and backfilled quarries in the area. Given the age of the quarries, it would be expected that the infill material would be substantially inert however if a route impacts the site, intrusive investigations should be used to determine the nature of the material.
The disposal of contaminated material off site will require adherence to the relevant Waste Management License Regulations and Duty of Care Regulations.
Due to the nature of a road scheme, the end result will be a covered site therefore any risk to human health from contaminated land should be minimal. Any risk to controlled waters should be identified and addressed as part of the ground investigation.
6.7 Soil Chemistry Sulphate and acid conditions are not expected to be significant. However, consideration should be given to the effects of chemically aggressive ground and groundwater on buried concrete. Structures should be designed on the basis of the results of laboratory testing on site specific samples.
6.8 Other Geotechnical/Man-Made Problems/Obstacles There is no evidence to indicate other geotechnical problems such as natural solution features or mining in the area. A number of small areas of soil instability have been identified during site surveys undertaken in April 2008 and are listed in Table 6.8-1 below.
A number of backfilled quarry workings and sand pits are located across the section. Should they lie within the proposed works then information would be required on the infill material and the adequacy of its compaction.
Table 6.8-1 Areas of Soil Instability
Observation East North
Soil Slippage/ Terracing 253107 365804
Soil Slippage/ Terracing/ Backscar 251102 363504 Soil Slippage/ Terracing 252685 360274 Soil Slippage/ Terracing 249012 359184 Soil Slump 258068 360084
796036-0600-R-007 65 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Soil Slippage/ Terracing 254986 361414 Soil Slippage/ Terracing 262691 357826 Soil Slump 263830 353752
796036-0600-R-007 66 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
7 Comparison of Projects Options and Risks
7.1 Statement of Preferred Route Options 7.1.1 Preferred Corridor The Engineering Study Area was selected to encompass the majority of feasible routes between Londonderry and Aughnacloy and was up to 10km wide. An initial filtering of the engineering study area to establish a preferred corridor was carried out during July and August 2008.
The Preliminary Options Stage (POR1) was intended to narrow the study area to a 1km wide corridor which could be studied in greater detail. A number of feasible preliminary road alignments, with no departures from standard for vertical and horizontal alignments, were drawn up to assist in the assessment. Consideration was given to the relative merits of the following disciplines:
Engineering
• Highway alignment
• Ground conditions
• Flooding & Drainage
• Utilities
• Buildability
Environment
• Landscape
• Ecology
• Noise / Air Impact
• Archaeology
Economics
• Cost
• Traffic & Economic Benefits
796036-0600-R-007 67 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
The following aspects relating to ground conditions for the entire scheme were considered:
7.1.1.1 Terrain High ground associated with the Slievemore Ridge in the south would result in severe and significant earthworks and should be avoided where possible. In the case of the ridge, as this runs perpendicular to the orientation of the road, it was agreed that the corridor should utilise existing “passes” through the ridge where possible.
Rising ground east of Aughnacloy will be hilly and hard to excavate, so should be avoided if possible.
7.1.1.2 Soft Ground There are a number of areas of peat, (especially East and southeast of Omagh) and alluvium which would cause excessive problems with settlement or costly replacement / foundation solutions to earthworks. These are particularly present at the following locations, the extents of which were limited within the preferred corridor:
7.1.1.3 Drumlin terrain Where drumlins occur, it is expected that the hollows between drumlins will be infilled with soft clay and peat which would require additional excavation to establish suitable foundations for earthworks. While it would not be possible to avoid the drumlin landscape, routes which took the shortest length across drumlin fields would be least affected. This particularly affects the area around Omagh and the Clogher Valley.
7.1.1.4 Industrial & Contaminated land. The largely rural nature of the area means that areas of industrial and potentially contaminated land are scarce however to limit the associated costs of remediation, potential routes should avoid these areas including:
• Significant current / historic landfill sites at Tullyvar (south of Ballygawley). • Sand & gravel workings (issues of unknown backfilling and risk of sterilising future resource), Eskragh and Fallghearn / Lurganboy (north of Ballygawley)
796036-0600-R-007 68 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Considering all of the above issues,the preferred corridor in Section 3 avoids where possible the extensive peat deposits south, east and southeast of Omagh and also Seskinore Forest, tying in to Section 2 as close as possible to the west side of Omagh, whilst maintaining a connection to the existing A5 alignment. Through the Slievemore ridge, the corridor divides into two limbs (east and west) to facilitate existing passes through the ridge south of Garvaghy and south of Newtownsaville respectively. The eastern option should avoid the high ground of Slievemore in the east and also south and west of Garvaghy, both of which contain blanket peat. The western limb should avoid the active sand and gravel pits at Eskragh, Knockmany Forest and the high ground with blanket peat south and west of Garvaghy on Tycanny Hill. These merge together again in the Ballygawley / Anaghilla area before the corridor once again diverges to allow consideration of options east and west of Aughnacloy. The corridor around Aughnacloy is restricted to passing as tight to the town as the constraints of the terrain, the “Thistle” (a landscape feature) and Blackwater River floodplain will permit. The eastern option should avoid the high ground and two protected environmental sites, Plaister Quarry and Drummond Quarry northeast of Aughnacloy The corridor includes the Tullyvar landfill which should be avoided by any potential routes but allows consideration of adoption of the ongoing improvements to the A5 at Ballygawley-Tullyvar.
7.2 Initial Reduction to Preferred Route Within the preferred corridor four alignments have been proposed; purple (fully east of the existing A5), green (fully west), red (west, then east S of Ballygawley) and pink (combination). These alignments are based on avoiding all major constraints of the disciplines involved (highways, environment, drainage, land aspects, structures) together with the minimum departures from standards for horizontal and vertical alignment. Details of the assessments are provided below.
7.2.1 Option F - Purple The Purple route, initially a western alignment, moves east at Drumconnelly to traverse an undulating drumlin topography, generating cuttings 3-17m deep and embankments up to 16m high primarily in glacial till locally expected to be around 4m deep. Earthworks will largely be in glacial clay. The beginning of the alignment crosses small pockets of peat within the inter-drumlin hollows for approximately 200m, and skirts an area of peat at chainage 63500-64000 where deposits extend to 8m below ground level (bgl). At Tullyheeran, between chainage 66000 to 66500, the route may encounter soft ground as it passes between two significant areas of peat 2.5m deep.
796036-0600-R-007 69 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Continuing east of the A5 across the sandstone ridge, the route cuts through glacial till and rock up to 16m deep and crosses river valleys on embankments 4-19m high. Substantial cutting through the sandstone conglomerate can be expected in parts from which 85% of the material generated may be suitable for re-use and is likely to predominantly comprise a red/brown pebbly sandstone (60% of which should qualify as class 6 selected fill). An area of peat (700m long) is crossed at CH77000 where deposits are expected to be up to 4m deep. As peat is highly compressible, weak, and forms a very poor road foundation expensive measures may be required to engineer across these deposits. Further south, alluvial soils 3-5m deep associated with the Ballgawley Water and Routing Burn floodplains are encountered with localised deposits of 10m deep possible within the river valley on the northern slope of the ridge (CH 68500). Cutting through local sand and gravel deposits at CH73000 and CH75500 should yield good quality aggregate suitable for re-use. At CH71500 the route impacts a backfilled quarry, which could be expensive to reclaim and remediate.
To the south, the alignment passes north of Tullyvar to continue to the east of Aughnacloy through the pronounced drumlin landscape typical of the “Dungannon drumlins and hills”. This will entail substantial cuts through glacial till up to 12m deep and embankments across inter-drumlin areas and stream valleys up to 10m high. A number of asymmetric cuttings are required which necessitates meticulous observation during construction for plains of weakness and instability within the drumlins. Excavations will predominantly be in glacial clay of which around 60% is expected to be suitable for re-use. Around Black Hill and to the south, shallow rock is likely to be encountered where 60-70% may be suitable for re-use in the works.
The inter-drumlin areas tend to be soft and although rock can be at shallow depth it is likely that soft ground (up to a depth of 2m) will have to be removed to establish suitable foundations for the embankments. Limestone can be expected within 2m of the ground surface between CH84000-87500 with rock arisings from cuttings generating Class 6 aggregates. The route passes north of the Tullyvar Landfill crossing two backfilled quarries at CH 86000 and impacting another backfilled quarry at CH 87500. These areas are currently reclaimed and the associated contamination risk is expected to be low. To the east of Aughnacloy, the route crosses low lying alluvial deposits, anticipated to be 3-5m deep, associated with local watercourses of the Blackwater River catchment.
796036-0600-R-007 70 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
7.2.2 Option E – Green The Green option follows the initial western alignment of the Purple route before continuing on a western alignment past Seskinore and Moylagh. Cuttings up to 14m deep can be expected through the drumlin terrain with embankments between 2 and 9m high across the interdrumlin areas. Much of the excavated glacial till is likely to be too wet for re-use without further treatment, with 50% likely to be unsuitable for re-use. Localised pockets of peat less than 2m deep may be encountered (such as that around CH63500) and soft lake alluvium (around CH65000) which would require removal and replacement with rock fill before the commencement of any construction. Small rock cuts through the Shanmullagh Sandstone Formation may be required from CH65000-67000 where rock is likely to be shallow at 4mbgl.
As the alignment crosses along the west of the Slievemore ridge, substantial cuttings 5-21m deep are produced through an area where rock is in close proximity to the surface (approximately 2-5mbgl) from CH71000-79000. Rock will provide an excellent foundation for the road pavement and may omit the need for a capping layer. The most significant cuttings are generated on the northern and southern slopes where large rock cuts up to 21m can be expected. A large proportion (85%) of the material won across the ridge is likely to be suitable for re-use with only 60% of the glacial clay from the southern links (Tycanny Hill to Aughnacloy) suitable. A backfilled quarry is impacted at CH68000 of which the composition and compaction of the backfilled material is unknown. Around Newtownsaville the route crosses tracts of alluvium up to 150m long associated with floodplains of the Routing Burn & its tributaries. At Moylagh alluvial deposits up to 11m deep have formed within the river valley delineating the northern boundary of the ridge at the Tempo-Sixmilecross fault. Any bridge structures over this area should avoid foundation on the fault line as zones of broken less stable rock may occur with implications on bearing capacity.
To the south, the Green alignment crosses drumlin terrain, which is less pronounced to the west of Aughnacloy, generating cuttings predominantly through glacial till of which 60% of the material generated is expected to be suitable for re-use. Embankments up to 10m high can be expected across the watercourses within the Ballygawley Water and Blackwater River catchments which migrate through the inter-drumlin areas. Alluvial deposits are generally not expected to exceed 2-3m deep due to the presence of rock within close proximity of the ground surface throughout the area. Due to the variable nature of the soft alluvium, the material may require excavation before construction or the use of surcharging or band drains to accelerate the settlement. At Aughnacloy the route is very constrained between town and river a number of sites are impacted which could have associated contamination issues and potentially incur significant decontamination works, including a petrol station (CH89600), waste water treatment works (CH89400) and backfilled quarry (CH86250).
796036-0600-R-007 71 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
7.2.3 Option B – Red The Red route initially follows an eastern alignment around Tattykeel/Ranelly on embankment up to 12m high across 600m of low lying peat which is up to 9m deep. For deposits of peat deeper than 4m, a piled basal reinforced load transfer platform may be required to support the embankments across the peat. At Tattykeel/Ranelly, the route crosses to the west requiring extensive cut and fill as it passes west across the undulating drumlin landscape. Cuttings will predominantly be in glacial till, of which 45% is likely to be suitable for re-use, but may also require cuttings from CH69000-70000, where rock is expected within 2-3mbgl. The route may cross localised areas of peat and alluvium associated with tributaries of the Camowen River at CH65000.
The Red alignment follows that of the Green route across the sandstone ridge. Further south the Red alignment extends west of the Green route from CH 81000- 84500 with cuttings through drumlins up to 15m deep and embankments 4-11m high across Annaghilla River and inter-drumlin areas before moving east to follow the alignment of the Purple route to the north of Tullyvar landfill.
Subsequently, the Red route travels the furthest east onto higher ground generating significant earthworks with cuttings and embankments of maximum depth / height 24m and 14m respectively. Within the vicinity of these deep cuttings, rock is expected to be encountered within 3-5m of the ground surface and is likely to be strong limestone which may require blasting however should generate Class 6 selected fills. Founding materials will be generally glacial till or rock however where loose sand is expected at CH92000 and where areas of alluvium are crossed the founding conditions will have to be improved. Techniques such as surcharging or band drains may be required to accelerate settlement or for shallow deposits, the material may be excavated and replaced with rock fill to provide a suitable platform.
7.2.4 Option C – Pink Route The Pink route initially follows the Red alignment before continuing east through Rannelly and Gortaclare. At Tattykeel, the route is substantially on embankment to cross low lying peat up to 9m deep at CH62000 and alluvium 2m deep associated with tributaries of the Camowen River. The Pink alignment continues on an eastern path following the Purple route across the sandstone ridge before passing to the south of Tullyvar landfill site predominantly on embankments 7-10m high. The Pink route creates a large cutting, 23m deep, through the side of a drumlin at CH87250 before re-joining the Purple route to pass to the east of Aughnacloy.
7.2.5 Comparison of Routes Table 7.2-1 below provides a rough estimation of the quantities of cut and fill which will be generated along each of the alignments within Section 2 of the scheme. These figures are based upon all cuttings and embankments being provisionally at 1v:3h side slopes.
796036-0600-R-007 72 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Table 7.2-1 Earthwork Volume Totals
Alignment Total Cut Volume (m 3) Total Fill Volume (m 3) Purple 5 576 900 3 802 800 Green 5 017 600 3 311 700 Red 6 247 200 4 413 987 Pink 5 817 900 4 042 900
Considering the volumes of cut generated and fill required for each route, the Green route has the smallest volumes and best cut / fill balance (excess of 1.6Mm3 of material) however the fill is of poorer quality for re-use than the Purple and Red routes. The Red route requires the greatest amount of excavation (including high volumes of rock) and has an excess of almost 2Mm3 of material. The Purple and Pink routes both generate an excess of approximately 1.8Mm3.
Table 7.2-2 below summarises the main geotechnical constraints that will impact upon each of the alignments.
Table 7.2-2 Ranking of Geotechnical issues affecting Route Options
Alignment Issue Purple Green Red Pink Size of earthworks (volume) Fill re-usability Amount of Rock Excavation Peat / soft ground Contaminated sites Structure foundation problems
OVERALL RATING
/ / / - / / /
Positive neutral negative
796036-0600-R-007 73 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
7.2.6 Statement of Preferred Route on Geotechnical Grounds It is difficult to differentiate between routes as the key geotechnical issues largely affect all of the routes to a similar degree or the effects counter or balance each other out. Based on the extent of soft ground, earthworks balance and avoidance of significant man-made features the Green route emerges as a slightly preferable route option. The Pink and Purple routes generally encounter more soft ground particularly peat, with extents 4-5m deep encountered on the Red and Pink route links at Tattykeel and similarly further south through the Pink/Purple route links at Tullyheeran, Roscavey and Garvaghy.
The Green route is shorter with the least length of earthworks however relief is high to the south west of the sandstone ridge generating large cuttings (up to 21m deep) on the western (Green/Red) alignments. Alternatively, the eastern Pink route has large earthworks up to 23m deep to the south of Tullyvar. The western alignments through the Slievemore ridge (Red/Green) require marginally more rock excavation than those to the east as rock is closer to the surface 1-3m bgl for a greater distance.
As the geological trends and the topographic zones characteristic of this section run perpendicular to the route alignments the quality of excavated fill generated is similar for each of the alignments. An exception is the high quality of the material generated as the Red route crosses limestone north of Aughnacloy where more suitable material is generated compared to corridors to the west.
All routes have the potential to encounter potentially contaminated soils however more significant contamination is likely to be associated with the Green route link at Aughnacloy which impacts a petrol station.
Overall, the green route is marginally most favourable as it is
a) shortest
b) encounters least peat
it is likely though that a combination route, substantially based on the green but with local variants, especially in the far north and south will be adopted.
7.3 Establishment of Geotechnical Risk Register A suggested format for the geotechnical risk register is given in Appendix G. This is intended to be compatible with that in HD22/08 as well as the Highways Agency Risk Model (HARM) risk management model. This has been developed and incorporated into the overall project risk and opportunity register, but will be required to be developed as the project proceeds.
796036-0600-R-007 74 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
7.4 Geotechnical Classification In the absence of major structures or unusually difficult ground conditions, it is proposed that the scheme is assigned to Geotechnical Category 2 in accordance with HD22/08 and in line with the Statement of Intent.
7.5 Annex A Annex A for the Main Ground Investigation will be issued separately to this report.
796036-0600-R-007 75 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
8 Figures and Drawings
Figure 1.2-1 Regional Context Plan
Figure 1.2-2 A5 Western Key Transport Corridor Study Area
Figure 4.1-1 Blanket peat bog on Slievemore
Figure 4.2-1 Lowland drumlin landscape south of Omagh
Figure 4.2-2 High ground of Slievemore
Figure 4.2-3 Drumlin landscape in Sub-Section 3C
Figure 4.2-4 River Blackwater tributary
Figure 5.2-1 SPT N Value vs depth for Made Ground
796036-0600-R-007 76 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
Figure 5.3-1 Moisture content v depth for River Alluvium
796036-0600-D-00061 A5 Western Key Transport Corridor Scheme Split
796036-0600-D-00062 Historical Exploratory Hole Locations
796036-0600-D-00063 Drive through Survey Notes & Photographs
796036-0600-D-00064 Walkover Survey Reports and Photographs
796036-0600-D-00065 Quarry and Landfill Survey
796036-0600-D-00066 Peat Survey
796036-0600-D-00067 Preliminary Ground Investigation Locations
796036-0600-D-00068 3-D interpretation of the terrain
796036-0600-D-00069 Steepness of the terrain
796036-0600-D-00070 Historical OS Mapping 6 inch 1 st Edition c1830
796036-0600-D-00071 Historical OS Mapping 6 inch 2 nd Edition c1860
796036-0600-D-00072 Historical OS Mapping 6 inch 3rd Edition c1904
796036-0600-D-00073 Historical OS Mapping 6 inch 4th Edition c1930
796036-0600-D-00074 Historical OS Mapping 1:10,000 1st Edition c1960
796036-0600-D-00075 Historical OS Mapping 1:10,000 2nd Edition c2007
796036-0600-D-00076 Current Orthophotography
796036-0600-D-00077 Bedrock Geology
796036-0600-D-00078 Superficial Geology
796036-0600-D-00079 Hydrogeological Map
796036-0600-D-00080 Groundwater Vulnerability Map
796036-0600-D-00081 Surface Water Quality Information
796036-0600-D-00082 River Pollution Incidents
796036-0600-D-00083 Man-Made / Potentially Contaminated Features
796036-0600-R-007 77 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
796036-0600-D-00084 Existing Ground Conditions
796036-0600-D-300011 Long Section of historical borehole data - Tullyvar (1 of 2)
796036-0600-D-300012 Long Section of historical borehole data - Tullyvar (2 of 2)
796036-0600-D-300013 Long Section of historical borehole data - Annaghilla
796036-0600-R-007 78 June 2009 © Mouchel 2009
A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
This Certificate is:
(a) received* (see note) (b) received with comments as follows:* (see note) (c) returned marked "comments" as follows:* (see note) Signed: Overseeing Organisation Geotechnical Advisor Name: Date:
Note:
'Received' = Submission accompanying certificate is accepted. 'Received with comments' = Submission accompanying certificate generally acceptable but require minor amendment which can be addressed in subsequent revisions. 'Returned marked comments' = Submission accompanying certificate unacceptable and should be revised and resubmitted.
796036-0600-R-007 June 2009 © Mouchel 2009 A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
APPENDIX A:
Guidance on Navigating the GIS Data
A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
APPENDIX B:
Geological Long Sections
A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
APPENDIX C:
Annex A to the Preliminary Sources Study
A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
APPENDIX D:
Historical Mapping
A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
APPENDIX E:
Water Quality
A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
APPENDIX F:
Copies of Statutory Consultee Responses
A5 Western Transport Corridor Preliminary Sources Study Report – Section 3
APPENDIX G:
Preliminary Risk Register