Chapter 14 Geology and Soils - Northumberland€¦ · An earthworks Specification in accordance with the HA Series 600 will need to be produced for the scheme as part of the detailed

Chapter 14 Geology and Soils

Document Reference MNB Part 6.1.15

Regulation Reference 5(2)(a)

PINS Reference Number TR010010

AECOM A1-SENSLR: MNB – Environmental Effect Assessment – Part 2: Environmental Statement 14-2

Introduction

14.1 This chapter identifies baseline conditions with reference to soils, geology and potential ground contamination from previous land uses along the route of the proposed road and describes how they may be affected by the development. It sets out in detail the effects that the construction and operation of the bypass and its associated infrastructure may have and identifies mitigation measures to avoid, reduce or offset any adverse effects.

14.2 Specifically this chapter considerers effects on:

Site Designation;

Geology and Geomorphology;

Minerals;

Soils; and

Contaminated Land.

14.3 Hydrogeology has been assessed in Chapter 13 Road Drainage and the Water Environment.

Legislation and Policy

14.4 Part IIA of the Environmental Protection Act (1990), as amended, provides a legislative context for the assessment of contaminated land. Contaminated land for the purpose of Part IIA is defined as ‘land which appears to the Local Authority [acting on Statutory Guidance] to be by reasons of substances in, on or under the land that:

14.5 ‘Significant harm is being caused or there is a significant possibility of such harm being caused’: or

14.6 ‘Pollution of Controlled Waters is being, or is likely to be caused’.

14.7 The proposed route is being developed by NCC and its representatives. The development will adhere to guidance detailed in the following Planning Policy documents:

Northumberland County Council, Northumberland, Local Minerals Plan, 2000;

Castle Morpeth District Local Plan - adopted by Northumberland County Council (http://www.cmlocalplan.co.uk/frset.html) and

National Planning Policy Framework (NPPF) which replaced PPS 9 - Biodiversity and Geological Conservation (for Geological RIGS).

14.8 The following legislation has also been considered:

The Dangerous Substances Directive (78/464/EEC);

Pollution Prevention and Control Act 1999;

Environmental Protection Act 1990;

Wildlife and Countryside Act 1981 (amended 1985) (For Geological SSSI’s);

Chapter 14 Geology and Soils


Control of Pollution Act 1974;

Control of Pollution (Oil Storage) (England) Regulations 2001;

Contaminated Land (England) Regulations 2000; and

Anti-Pollution Works Regulations 1999.

Methodology

14.9 The following Section describes the method used to determine likely significant effects on geology and soils.

Scope of Assessment

14.10 An assessment of the likely geological effects of the proposed road scheme is necessary, as there may be direct effects on geology, underlying soils and potential mineral resources.

14.11 The assessment includes a review of information provided by Statutory and non statutory bodies in relation to site designation, geology, minerals, soils and contaminated land.

14.12 The assessment covers the construction and operation of the bypass and covers the area within the proposed road corridor (footprint of the works).

14.13 Table 14.1 describes a range of development parameters that were used to undertake the assessment. Development parameters are defined in Table 2.3 of Chapter 2.


Table 14.1: Design Parameters

Development Parameter Is the information important in the assessment of ‘likely significant effects’? Why?

If so how was the information included in the assessment, and in what form?

Red Line Boundary Yes, as it is this boundary (footprint) which defines the limit of works

The assessment of baseline conditions has been established for the area within the proposed road corridor.

Vertical Road Alignment Yes, as it is this extent of the road corridor.

The assessment of baseline conditions has been established for the area within the proposed road corridor.

Horizontal Road Alignment No N/A

Number of carriageways No N/A

Location of roundabouts No N/A

Area of development See red line boundary comment

N/A

Volume of earthworks Yes As described in Table 2.3 of Chapter 2.

Footprint of earthworks Yes

As Table 2.3 of Chapter 2 and see Height and angle of repose of embankments below.

Height and angle of repose of embankments

Yes

A preliminary geotechnical assessment of slope stability by hand calculation was undertaken prior to ground investigation which indicated that embankments and cuttings with side slopes of 1 vertical to 2.5 horizontal would be feasible for glacial till soils and this slope angle is adopted for all the earthworks along the length of the scheme. Manual calculations of have been repeated for selected earthwork sections by computer aided slope stability analysis, using specialist software SLOPE V12.01, leased from GEOSOLVE and recommendations for construction have been assessed and reported as part of geotechnical design works. Slope stability calculations have shown acceptable factors of safety for all earthwork cuttings and embankments, assuming laminated clay is not used in embankment construction. The use of laminated clays soils within embankments with slope angles of 1 vertical to 2.5 horizontal is not recommended and shallower slope angles would be required

Depth of cuttings Yes As described in Table 2.3 of Chapter 2.

Landscape planting No N/A

Arched Structure design – type, diameter etc.

No N/A

Location, type and volume of SUDS

No N/A

Location of surface water outfalls

No N/A


Development Parameter Is the information important in the assessment of ‘likely significant effects’? Why?

If so how was the information included in the assessment, and in what form?

Route of replacement PRoW

No N/A

Cut and fill balance Yes

Soil properties and ground investigation laboratory test data for consideration of earthworks, material classification, acceptability criteria and reuse have been assessed and reported as part of geotechnical design works. General earthworks materials have been classified, in accordance with HA Specification for Highways Works, Series 600. Limited fluvio-glacial soils will be encountered in earthwork cuttings and these soils should be retained for used as Overlaying Material to Corrugated Steel Structures. Upper glacial soil intercepted in cuttings is suitable for reuse in embankments at slope angles 1 vertical to 2.5 horizontal. Use of laminated clays soils within embankments with slope angles of 1 vertical to 2.5 horizontal is not recommended. An earthworks Specification in accordance with the HA Series 600 will need to be produced for the scheme as part of the detailed design works and for use in construction.

Lighting – location, type, number, and height of lighting columns

No N/A

Bridge, large structure designs

No N/A

Changes to the provision for pedestrians and cyclist

No N/A

Vehicle speed rating for the bypass

No N/A

Gradient No N/A

Road surface characteristics No N/A


Assessment Method

14.14 The assessment for Geology and Soils has been undertaken in accordance with guidance provided in DMRB Volume 11, Section 3, Part 11. The assessment of baseline conditions has been established for the area within the proposed road corridor by referring to various sources of information including a number of previous desk-based study reports as well as a number of ground investigation factual reports that are available for the site, as listed below:

Sources of information reviewed include:

1:50,000 Geological Survey Sheets 9 (Rothbury) and 14 (Morpeth);

1:10,000 Geological Sheets NZ18NE and NZ28NW;

British Geological Survey, Geology of the Morpeth District, Sheet Description of the British Geological Survey 1:50 000 Series Sheet 14, Morpeth;

British Geological Survey, Technical Report WA/90/19, Geology and land-use planning: Morpeth – Bedlington – Ashington;

Multi-Agency Geographical Information for the Countryside (MAGIC) website (soil quality data);

Envirocheck Report (including databases held by the Ordnance Survey, BGS, English Nature, Local Authorities, Environment Agency, DEFRA); (see Appendix 14.1);

Durham Mining Museum; and Exploratory borehole logs from previous ground investigations (detailed below).

Desk-based Study and Ground Investigation reports relating to part or all of the scheme include:

Scott Doherty Associates, A1 to South East Northumberland Link Road, Risk Assessment Desk Study, reference SDA/95013/Final, dated May 1996, undertaken on behalf of Northumberland County Council;

Ian Farmer Associates, A1 to South East Northumberland Link Road Ground Investigation Factual Report (Volumes 1 & 2), Ground Investigation Factual Report, reference NCC0616, dated December 1996 undertaken on behalf of Northumberland County Council;

Scott Doherty Associates, A1 - South-East Northumberland Link Road, Ground Investigation Phase 1, A1 Interchange to How Burn Crossing, Interpretative Report, reference SDA/95013/Final, dated September 1997, undertaken on behalf of Northumberland County Council;

Scott Doherty Associates, A1 - South-East Northumberland Link Road, Phase 2 Ground Investigation, Interpretative Report, reference SDA/95013(2)/Final, dated June 1997;

A1 South East Northumberland Link Road, Stage 2 Environmental Assessment, Department of Transport Design Manual for Roads and Bridges, Volume 11,


February 1999, Northumberland Technical Services Consultancy & Anthony Walker and Partners;

Scott Doherty Proposed A1 to South East Northumberland Link Road, Desk Study Review, May 2001, Northumberland County Council;

NCC Operational Services, A1 - South-East Northumberland Link Road, A1-A192 Link Section: St. Leonard's Interchange, Ground Investigation Factual Report, dated June 2003, undertaken on behalf of Northumberland County Council;

Wardell Armstrong, Pegswood / Beechcroft Opencast Site, Compaction Specification - Road Corridor, reference NT00021/Report 002, dated January 2004, undertaken on behalf of H J Banks & Company Ltd;

Wardell Armstrong, Pegswood / Beechcroft Opencast Site, Road Corridor, Compaction Verification Report, reference NT00021/Report 009 (Rev A), dated November 2004, undertaken on behalf of H J Banks & Company Ltd;

Scott Doherty Associates, A1 - South-East Northumberland Link Road, A1-A192 Link Section, St. Leonard’s Interchange, Ground Investigation Interpretative Report, Draft, SDA/02059/Draft, (Undated), 2003;

Faber Maunsell, Morpeth Northern Bypass, Geotechnical and Geo-environmental Review Report, Northumberland County Council, April 2007 Morpeth (Ref. 53101/IDAG Rev 0);

Faber Maunsell, Morpeth Northern Bypass, Supplementary Desk Study – Mining & Site Conceptual Model, Northumberland County Council, October 2008 (Ref. 53101/IDAG/002, Rev0) (see Appendix 14.1);

Northumberland County Council, Morpeth Northern Bypass, DfT Bid for Programme Entry, Volumes 1 and 2, 22/10/08 with Amendments to September 2009;

Northumberland County Council, Highways Laboratory, Morpeth Northern By-Pass – Ground Investigation – Preliminary, Investigation using the Panda 2 Dynamic Cone Penetrometer, Report Reference No. S1776, January 2010; and

Allied Exploration & Geotechnics Limited, Ground Investigation Report, Morpeth Northern Bypass Ground Investigation, Contract Number 3746, dated March 2010.

14.15 Information relating to the site has been reviewed in order to establish the current baseline conditions relating to Geology and Soils for the proposed route corridor prior to construction of the bypass. As assessment of the effects of existing baseline conditions, as well as the effects of the development on prevailing conditions are then assessed. Details of mitigation measures that may be required to avoid, prevent, minimise, reduce or offset effects, together with residual and cumulative effects following mitigation, are provided.

14.16 In order to make an assessment of the construction, environmental and human health risk a conceptual model needs to be developed for the site. This requires an examination of the ‘Source-Pathway-Receptor linkages’ to define construction, environmental and human health risk associated with existing and future conditions. The


first step of the model development is to identify both the contaminants of concern from possible sources and potential receptors on and around the site. The risk assessment is undertaken in accordance with the precautionary principle, in which a pathway is assumed to exist unless there is reasonable contrary evidence. The risk associated with each source-pathway-receptor linkage is a product of the probability that a significant pathway exists and the severity of the potential effect. A Preliminary Site Risk Assessment is provided in the Faber Maunsell (now AECOM) Supplementary Desk Study – Mining and Site Conceptual Model report (Faber Maunsell, 2008, Appendix 14.1). The risk assessment broadly follows the methodology detailed in CIRIA C552, Contaminated Land Risk Assessment, A Guide to Good Practice, 2001.

14.17 The site risk assessment has been reassessed in light of environmental testing undertaken as part of the recent ground investigation completed by AEG in March 2010 and the results of the of this risk assessment have been incorporated into this Chapter. The risks identified during the desk study have been updated in light of the findings of the ground investigation works and these have been used as the basis for the identification of effects.

14.18 Subject headings in this chapter are discussed as prescribed in DMRB Volume 11, Section 3, Part 11, Geology and Soils. There is however no specific methodology detailed in DMRB Volume 11, Section 3, Part 11 for assessment of risk to Geology and Soils, and determination of effect, importance, magnitude and significance. Therefore, the terminology and qualitative terms adopted for this Chapter are based on guidance provided in DMRB Volume 11, Section 3, Part 10, Road Drainage and the Water Environment (HD45/09). Specifically the methodology and terminology detailed in HD45/09 has been adopted, as summarised below:

HD45/09 - Table A4.3 - Estimating the Importance of an Attribute;

HD45/09 - Table A4.4 – Estimating the Magnitude of an Effect on an Attribute;

HD45/09 - Table A4.5 - Estimating the Significance of Potential Effects; and

HD45/09 - Table A4.6 - Qualifying Conditions for Overall Assessment Scores

14.19 Assessment methodology and terminology has been described in detail in Chapter 13 of this report, Road Drainage and the Water Environment.

14.20 The Importance of an attribute, specifically relating to Soils and Geology is provided in Table 14.2 below:


Table 14.2 Criteria to Determine Receptor Importance Importance Criteria Aspect Typical Examples

Very High

Attribute has a high

quality and rarity on

regional or national

scale.

Geology/Soils - Site protected by International or EU

legislation (World Heritage Sites, Geopark).

High

Attribute has a high


local scale.

Geology/Soils - Site protected by UK legislation e.g. Site of Special Scientific Interest.

Medium

Attribute has a

medium quality and

rarity on local scale.

Geology/Soils

- Site of local geological importance (Local Geological Site – previously Regionally Important Geological Site).

- Areas of potential mineral resource. - Areas with soils of best and most

versatile agricultural value.

Low

Attribute has a low


local scale.

Geology/Soils - Sites with little or no local geological/soils interest.

14.21 The Magnitude of an attribute, specifically relating to Soils and Geology is provided in Table 14.3.

Table 14.3 Criteria to Determine Effect Magnitude Magnitude Criteria Aspect Typical Examples

Major Adverse

Results in loss of

attribute and/ or

quality and integrity

of the attribute.

Geology/Soils

- Loss of the resource and/or quality and integrity of resource; severe damage to key characteristics, features or elements.

Moderate

Adverse

Results in effect on

integrity of attribute,

or loss of part of

attribute.

Geology/Soils

- The site’s integrity will not be adversely affected, but the scheme may lead to a loss of or damage to key characteristics, features or attributes.

Minor Adverse

Results in some

measurable change

in attributes quality

or vulnerability.

Geology/Soils

- A measurable minor negative effect on key characteristics, features or attributes is evident.


Magnitude Criteria Aspect Typical Examples

Negligible

Adverse

Results in effect on

attribute, but of

insufficient

magnitude to affect

the use or integrity.

Geology/Soils

- Minor alteration to one or more characteristics, features or elements or no observable effect.

Minor Beneficial

Results in some

beneficial effect on

attribute or a

reduced risk of

negative effect

occurring.

Geology/Soils

- A measurable minor positive effect on key characteristics, features or attributes is evident.

Moderate

Beneficial

Results in

moderate

improvement of

attribute quality.

Geology/Soils - A moderate positive effect on

key characteristics, features or attributes is evident.

Major Beneficial

Results in major

improvement of

attribute quality.

Geology/Soils - A major positive effect on key

characteristics, features or attributes is evident.

14.22 The Significance of the Potential Effects on Soil and Geology is in Table 14.4.

Table 14.4 Significance Criteria

Importance of Attribute

Magnitude of Effect

Negligible Minor Moderate Major

Very High Neutral Moderate/Large Large/Very Large Very Large

High Neutral Slight/Moderate Moderate/Large Large/Very Large

Medium Neutral Slight Moderate Large

Low Neutral Neutral Slight Slight/Moderate

Note: Shaded boxes indicate a ‘Significant Effect’. All others are ‘Not Significant’. Where a choice of two

effect significance descriptors is available, only one should be chosen. This allows for professional

judgement and discretion assessing effects.

Limitations and Assumptions

14.23 Data has been obtained from a number of statutory and non statutory bodies, previous reports (by others), and other external sources as identified in paragraph 14.14. The authors of this report are not required to identify insufficiencies or mistakes in the information provided by the user or owner or from any other source, but have sought to compensate for these, where obvious in the light of other information.

14.24 No further consultation responses were awaited at the time of writing this report.


Baseline Conditions

Introduction

14.25 The proposed route is approximately 3.8km long and extends from the A1 (at approximately NZ 180 868) to the A197 Whorral Bank roundabout (at approximately NZ 211 875) passing over U6010 Fulbeck Lane, Cotting Burn, How Burn and extends over three defined areas of the former opencast (now restored) coal mining site at Pegswood Moor. The proposed scheme infringes on the former Pegswood Moor Opencast site and crosses geomorphological features associated with How Burn and Cotting Burn. Topographically, the route follows a gently undulating profile from west to east with natural land surrounding the A1 at approximate level of 63 to 65m AOD, down to approximately 61m AOD at the east end of the scheme. Ground level at Cotting Burn and How Burn is approximately 55m and 59m AOD, respectively. At the west edge of the restored workings at Pegswood Moor a low valley type feature is present at a level of approximately 55m AOD; this carries a small surface drain which forms a tributary to How Burn.

14.26 Land use records and site history were studied and reported in detail in the Supplementary Desk Study report, October 2008, Ref. 53101/IDAG/002, Rev0 (see Appendix 14.1). Site history was examined for the east portion of the route (Pegswood to How Burn) and for the west part of the route (How Burn to the A192 and the A1). In summary, the east part of the route at Pegswood Moor has been subject to underground and opencast mining activity over a significant time period. The position of the historic shafts and colliery sites identified are shown on Drawing 53101/IDAG/812 (see Appendix 14.1). Historical references also mention one or more levels or adits driven from How Burn, although the locations of these entrances, if indeed they exist, are unknown. The boundary extent of Pegswood Moor Opencast Site (provided by others) is shown on Drawing 53101/IDAG/803B (see Appendix 14.1).

14.27 The west portion of the route has historically been used as farmland with the only development associated with a local access road identified as U6010 Fulbeck Lane and Rose Cottage, which is to be demolished. A domestic oil storage tank is present at Rose Cottage. At the west end of the route is the A1 trunk road, which runs in both cut and embankment and was constructed in the early 1970s.

Site Designation

14.28 The site and route alignment is not designated as a Site of Special Scientific Interest (SSSI) in relation to geological or geomorphological features that are considered of national importance.

14.29 The site is not designated a Regionally Important Geological Site (RIGS) that would be considered of regional or local importance.


14.30 No Geological Conservation Review records suggest that the site is likely to be given SSSI or RIGS status in the future.

Geology and Geomorphology

14.31 Sources of information and documents reviewed as part of this assessment are detailed in paragraph 14.14.

14.32 Published British Geological Survey (BGS) maps and intrusive ground investigation indicate the site is underlain by glacial till of varying thickness ranging from 25m at the west end of the scheme to 10m in the vicinity of Cotting Burn. East of How Burn, opencast coal workings were present at Pegswood Moor, these are now infilled and restored. From opencast mine completion plans, significant depths of made ground up to 80m are anticipated within the Pegswood Moor Opencast site, however, the route only infringes on three areas of known infill (proved by intrusive ground investigation to be up to 12m depth), see Drawing 53101/IDAG/803B (Appendix 14.1).

14.33 The glacial deposits are an over consolidated lodgement till which typically exhibits a threefold division comprising the upper stony clay, middle sands and gravels, and the lower boulder clay. The lower part of the upper stony clay is often noted to be become soft and more plastic and is often laminated.

14.34 Localised sands and gravels are mapped within the vicinity of the route. These intercept the route at Cotting Burn, How Burn, Pegswood Moor and Whorral Bank. A separate deposit of sand and gravel intercepts the route at St. George’s roundabout.

14.35 Bedrock comprises the Carboniferous Millstone Grit which extends from the A1 to a position inferred immediately east of St. George’s roundabout, west of How Burn. The Millstone Grit comprises an interbedded sequence of sandstones, fine grits, siltstones and thin coals. East of St. George’s roundabout, bedrock comprises the Carboniferous Coal Measures strata, an interbedded sequence of sandstones, siltstones, mudstones, seat earth and coal which overlie the Millstone Grit. The Carboniferous strata dip to the southeast.

14.36 The Pegswood Moor Fault represents a major structural discontinuity in the vicinity of the route and runs in a west-north-west to east-south-east direction, extending from just south of East Shield Farm (How Burn) to the south of the intersection of the A197 and the B1337, downthrowing to the north east by 30 to 40m, see Drawing 53101/IDAG/811 (see Appendix 14.1). The alignment of the route is south of the Pegswood Moor Fault.

14.37 It is considered that geomorphological features of significance intersected by the route are the natural valley features associated with How Burn and Cotting Burn.

Minerals

14.38 Fifteen named coal seams subcrop on the east portion of the route, as shown on Drawing 53101/IDAG/811 (please be aware that all drawings referred to in this section


are included in the report provided in Appendix 14.1). The seams demonstrate the regional dip to the southeast.

14.39 The extent of previous mining is discussed in detail in Faber Maunsell Supplementary Desk Study report, October 2008, Ref. 53101/IDAG/002, Rev0 (see Appendix 14.1).

14.40 Historically the area has been mined from ancient times that pre date modern records with the earliest recorded workings from Cottingwood Colliery dated circa 1730. Mining is also known at Banks Colliery (pre 1888), Jubilee Colliery (pre 1924), and Morpeth Moor Colliery (pre 1948). A number of known worked seams underlie the route at Pegswood Moor, and given the outcrop of seams at Pegswood, unrecorded shallow mine workings may also be present, see Drawing 53101/IDAG/803B. A number of mine adits are also known to be located along the banks of the How Burn Valley.

14.41 Recent mining activity comprised significant opencast workings at Pegswood Moor, immediately north of the east portion of the route. These workings were completed in 2002. From mining completion plans produced by HJ Banks for the site, thirteen seams of coal were worked, see Drawing 53101/IDAG/813 (in the report contained in Appendix 14.1). However, most of the opencast was in land north of the route, and the route only effects on the three small areas previously identified by Wardell Armstrong. Wardell Armstrong (reference NT00021/Report 009 (Rev A), dated November 2004) has reported re-excavation and compaction of the soils within these infill areas. Recent ground investigation completed by AEG (March 2010) has proved the presence of these areas and proved a maximum depth of infill of approximately 12m.

14.42 The report in Appendix 14.1 includes various drawings that show the extent of known workings at Pegswood Moor Opencast, the Top Busty Seam (Q1), the Old Man (Q2), the Little Seam (R), the Brockwell Seam (S) and the Choppington Brockwell (T) seam are included in the Faber Maunsell Desk Study.

14.43 The effect of the scheme on the historic mine workings has been assessed. Ground investigation to determine the extent of any remedial works that may be required has been completed by AEG in 2010.

14.44 It is considered that mine workings that may influence the surface have been proved along the full east extent of the scheme.

14.45 Subsidence may result from a collapse of a conical void below ground surface which has migrated through the ground, due to collapse of historic mine workings. The consequences of subsidence below a road pavement range from loss of serviceability to complete collapse.

14.46 Remedial options for pavement construction have been assessed and reported as part of geotechnical design works. Options considered include geogrid reinforcement incorporated into the unbound granular or a thickened granular sub base construction to provide a reinforced flexible pavement. The purpose of the geogrid would be to even out


any stresses in the pavement due to settlement of the ground from collapsed workings and limit the potential for unacceptable differential settlement and cracking in the pavement surface. If ground settlement occurs under these circumstances it is likely that the pavement surface would over time ‘dip and hollow’ and may need to be periodically resurfaced. Whole term maintenance costs and resurfacing works will need to be considered. This option does not provide any safeguard against catastrophic failure and sudden collapse events.

14.47 Ground investigation indicates that none of the proposed structures are underlain or affected by historical mine workings at a depth that could affect the integrity of the foundations. Therefore compensation grouting of potential mine workings is not proposed as part of the scheme.

14.48 Local sand and gravel resources are noted along the alignment of the route on the Northumberland Local Resources Plan.

14.49 The Northumberland Local Resources Plan identifies Pegswood as an area of coal resources. The plan pre dates the opencast mining at Pegswood Moor Opencast and coal has since been extensively extracted by opencast methods.

Soils

14.50 Information provided on MAGIC.gov.uk for agricultural soil classification as supplied by DEFRA (published 2002) indicates that soils for the entire route are classified as Grade 3 (moderate to good). It should be noted that soil classification at Pegswood Moor is unlikely to have been updated since closure of Pegswood Moor Opencast in 2003.

14.51 Soil information from the Soil Survey of England and Wales and Cranfield University National Soils Institute show the site to be underlain by soils of the Dunkeswick P, Nercwys, and Soil 92C and disturbed workings associated with opencast coal workings.

14.52 The Dunkeswick P soils are described as slowly permeable soils that impede percolation resulting in rapid runoff. They are described as seasonally waterlogged for long periods in winter. The soils are suitable for arable cropping and intensely managed grasslands. The Nercwys soils are described as relatively dry because the slowly permeable subsoil is underlain at shallow depth by permeable bedrock. Soils are mainly cultivated for grass but also include cereal crops such as barley. Soils associated with restored workings tend to be associated with permanent grasslands.

14.53 The Environment Agency Aquifer Vulnerability Map, Sheet 2, 1:25,000 shows that the site is underlain by a Minor Aquifer. The soil has been classed as ‘Low’ leaching potential for the majority of the site. However, the route does infringe on areas with soils of high leaching potential at How Burn Wood and soils of intermediate leaching potential in the area of Cotting Burn. Typically, urban environments and restored mineral workings area classified as ‘U’, indicative of high leaching potential and worst-case vulnerability


classification due to site use, however Pegswood Moor has not been designated in this way.

14.54 It is noted that aquifer designations in England have recently been amended by the Environment Agency. The Carboniferous Bedrock is now designated as a ‘Secondary A’ bedrock aquifer, the sand and gravel deposits are also recorded as a ‘Secondary A’ drift aquifer’ according to the Environment Agency website. Assessment of the effect on groundwater and the water environment is provided in Chapter 13.

Contaminated Land

14.55 Historical development and land use is discussed in detail in the Faber Maunsell Desk Study (2007). A site conceptual model is included within the desk study, see Appendix 14.1. This has been used as a basis to define effects of the scheme on Geology and Soils within this chapter.

14.56 Historical maps show potentially contaminative uses on the east portion of the site at Pegswood Moor to be associated with the historical underground mining and opencast mining at Pegswood Moor. The west portion of the route has historically been used as farmland with the only development associated with a local road identified as U6010 Fulbeck Lane and Rose Cottage, which is to be demolished. A small domestic use oil storage tank is associated with the property at Rose Cottage.

14.57 The A1 is present on the west side of the route, constructed around 1973. The embankment is constructed of made ground comprising reworked natural clay soils and is not anticipated to include any significantly contaminated soils. The site risk assessment has been reassessed in light of environmental testing undertaken as part of the recent ground investigation completed by AEG, Ground Investigation Factual Report, dated March 2010, and this has been used as the basis for the Identification of effects.

14.58 AEG Ground investigation works comprised 39 cable percussive boreholes, with rotary core follow on into bedrock in selected holes. Boreholes extended to a maximum depth of 45.7m. Ground investigation also included 30 machine excavated trial pits to a maximum depth of 4.6m and 41 window sample boreholes to maximum depth of 10.55m.

14.59 Contamination testing has been undertaken on selected samples of soil and prepared leachate along the proposed route of the bypass. The sampling strategy, analytical suites and quantity of testing undertaken was developed in order to evaluate environmental risks and meet regulatory requirements under waste regulation. Chemical tests were scheduled for a broad range of metals associated with colliery sites, traditional screening analytes including asbestos, speciated polycyclic aromatic hydrocarbons (USEPA Priority 16 PAHs) and split banded petroleum hydrocarbons (which are referred to as the TPHCWG suite). Geochemical testing was also included to assess risk of aggressive ground conditions to buried concrete, as well as Waste


Acceptance Criteria (WAC) testing which has the dual purpose of providing evidence of environmental risks through leaching and indicating classification of waste for disposal e.g. Inert.

14.60 The findings of the contamination assessment are summarised below:

Representative samples of Topsoil, Made Ground and natural soils have been tested to assess the risk of soil contamination by substances that are toxic to humans or harmful to controlled waters. No evidence of significant contamination has been found in these samples to suggest that any of the materials tested cannot be re-used on the scheme.

Surplus non-organic soils are likely to classify as Inert Waste for the purposes of waste regulation (other than Topsoil, Organic Clay or Peat not passing WAC), although this would need to be confirmed by verification testing to comply with UK waste regulation.

Re-use of uncontaminated surplus topsoil and subsoil may be excluded from waste regulation at the discretion of the Regulator or under forthcoming EU Directives. The advice of the Environment Agency needs to be obtained to determine whether re-use of surplus topsoil or subsoil will require Environmental Permitting, Waste Exemption or an EA position that waste regulation is not required on a site specific basis.

As a matter of principle we advise that Made Ground should be used within the areas of generation in order not to depreciate greenfield areas of the scheme. Specifically, material generated from the St. Leonard’s A1 Junction should be re-used within the A1 approach embankments, and Made Ground from the Pegswood Moor section should be re-used within the area of the former Pegswood Moor Opencast mine.

It is concluded that no significant sources of contamination have been identified for the site conceptual model of the scheme.

14.61 Discussion with the Local Authority Contaminated Land Officer has taken place and planning conditions agreed. If, during development, contamination not previously identified is found to be present at the site then no further development (unless otherwise agreed in writing with the Local Planning Authority) shall be carried out until the developer has submitted, and obtained written approval from the Local Planning Authority for a remediation strategy detailing how this unsuspected contamination shall be dealt with. The remediation strategy shall be implemented as approved.

Identification of Effects

14.62 The following section identifies the potential effects of the soils and geology that may occur as a consequence of the proposed development. The potential effects are first assessed assuming no mitigation. The significance of the potential effects has been undertaken in accordance with the methodology detailed in paragraph 14.14 onwards and are detailed along with possible mitigation measures in Tables 14.5 and 14.6. For the purposes if this ES effect identification has been separated into two phases, construction and operation:


14.63 A summary of all the effects considered is presented in Tables 14.5 and 14.6, respectively. Where some effect has been identified, these are discussed below.

Identification of Effects - Construction Phase (Table 14.5)

14.64 The magnitude of effects identified during the construction phase, relating to potentially contaminative soils and spillages of fuels from construction plant are considered Moderate Adverse and Slight Adverse, respectively. Potentially contaminated soils have development implications which may include transport and disposal costs, regulatory implications, re-use of site won materials, importation of clean soils, planning restrictions and onerous construction procedures.

Identification of Effects - Operational Phase (Table 14.6)

14.65 The magnitude of effects of the operational phase is as follows:

14.66 Construction of an embankment over the existing valley features at How Burn and Cotting Burn to create the road crossing is considered to be of Minor Adverse on Geology and Geomorphology due to very localised changed to the topography and valley features at the burn crossings.

14.67 Loss of topsoil and agricultural soils resulting from construction and operation of the scheme is considered to be Minor Adverse.

14.68 Loss of potential sand and gravel mineral resources below the land take area is considered to be of Minor Adverse.

14.69 Loss of potential coal mineral resources below the proposed development area is considered negligible. This magnitude would have been considered Minor Adverse, however, as the coal mineral resource at Pegswood Moor immediately north of the route has already been extracted and ‘won’ the magnitude is reduced.

14.70 Significance of effect from contaminated land effects are considered to be of Slight Adverse significance. Made ground soils (for example originating from the A1 cutting or low cutting in Pegswood Restored Opencast) will be reused on site as landscaping material. Where soils are found to be contaminated, they will be assessed and re-used on site if possible, or treated and disposed of off-site at a Licensed Waste Management facility in accordance with UK waste regulations. However, contamination test results of soils sampled as part of recent ground investigation works have not identified any significantly contaminated soils on the site.

Cumulative Effects

14.71 It is also proposed to provide access from St. George’s Roundabout to a proposed new mixed development comprising a new hospital and residential housing, south of the site, on land previously occupied by St. George’s Hospital. The scope of the proposed


development is not fully defined, although significantly adverse cumulative effects to Soils and Geology are not anticipated.

Mitigation

14.72 The significance of all construction phase risks is reduced to Neutral by the adoption of good working practices and implementation of a construction environmental management plan during construction. The Contractor would be required to provide method statements for the works for input into the construction environmental management plan. Special precautions over and above this are not considered necessary for this proposed development.

14.73 There are no mitigation measures that can be reasonably included in the scheme to reduce the significance of the effect identified on Geology and Geomorphology during the operational phase. However, this effect is very localised and may be offset by other factors associated with the development, for example as amenity access (cycle path and footpath) are created.

14.74 Mitigation measures for potential loss of topsoil, sand and gravel mineral resources will be to ensure that where these soils are excavated, they will be reused as part of the development.

14.75 There are no economically viable mitigation measures to reduce the effect resulting from loss of agricultural soils or future isolation of sand and gravel resources due to the development (i.e. they are locally covered by the road construction).

Residual Effect

14.76 Table 14.5 summarises the residual effects of the proposed bypass on Geology and Soils during the construction phase and Table 14.6 during the operational phase, respectively.

Summary and Conclusion

14.77 Residual significance following mitigation for construction phase risks is defined as neutral (i.e. neither adverse nor beneficial).

14.78 Residual significance following mitigation for operational phase risks is defined as neutral or minor adverse, which is defined as a minor negative effect, that although measurable, is not considered a ‘Significant Effect’.


Table 14.5 Summary of Potential Effects and their significance – Construction Phase

Potential Effect Feature Quality Importance Magnitude Significance Mitigation

Residual Significance

(with mitigation)

Contaminated Land

Accidental spillages or leakages

Soil N/A Medium Minor Adverse Slight Good construction practice and or site operation will reduce significance to Neutral.

Neutral

Mobilisation of existing contaminants in made ground during earthworks

Soil N/A Medium Moderate Adverse

Moderate Good construction practice and or site operation will reduce significance to Neutral

Neutral

Mobilisation of existing contaminants in made ground during earthworks

Human Health N/A Medium Moderate Adverse

Moderate Good construction practice and or site operation will reduce significance to Neutral.

Neutral

Waste soil treatment and disposal

Soils N/A Medium Minor Adverse Slight

Generation of waste will be minimised through re-use of suitable excavated soils as substitutes for imported material. An appropriate framework for re-use of soils will be provided in the Earthworks Development and Waste Management Plan for the scheme. Unsuitable soils will be treated and reused as part of the development under Environmental Permits or exemptions where applicable. Waste soils unsuitable for treatment will be disposed of off-site to an appropriately licensed landfill under Duty of Care Regulations.

Neutral


Table 14.6 Summary of Potential Effects and their significance – Operational Phase Potential Effect Feature Quality Importance Magnitude Significance Mitigation Residual

Significance (with mitigation)

Site Designation

Change in Site Designation e.g. RIGS and SSSI (geology)

Site Designation (site is currently unclassified)

Low Low Negligible Neutral

None required. Significant excavation or cutting to expose rock is not proposed; therefore status is unlikely to change.

Neutral

Geology and Geomorphology

Infilling existing valley features

How Burn Cotting Burn

Medium Medium Minor Adverse Slight

Construction of road and cycle path will provide amenity access therefore Slight Adverse, so overall Significance may be Minor Beneficial

Slight Adverse

Soils

Loss of topsoil / agricultural soils classified as moderate to good (MAGIC.gov.uk)

Agricultural soils

Medium Medium Minor Adverse Slight Topsoil is to be reused within landscaping areas.

Slight Adverse

Minerals

Loss of mineral resource below land take area

Coal Mineral resource

Medium Low Negligible Neutral

Most seams have been mined by opencast methods immediately north of the route from Pegswood Moor Opencast. Future mining of limited exposures below the route is considered unlikely.

Neutral

Loss of mineral resource below land take area

Sand and Gravel resource

Medium Medium Minor Adverse Slight

Any sand and gravels excavated as part of excavation of shallow cuttings / earthworks will be incorporated into the scheme.

Slight Adverse

Contaminated Land

Accidental spillages or leakages

Soil N/A Medium Minor Adverse Slight Swales/ditches are proposed on site Slight Adverse

Existing surface contaminated soils

Soil Human Health Underlying aquifer

N/A Medium Minor Beneficial Slight

Construction of the road will provide an impermeable cover to any potential contaminated soils within Pegswood.

Slight Beneficial


Potential Effect Feature Quality Importance Magnitude Significance Mitigation Residual Significance (with mitigation)

Site Designation

Localised contamination from oil storage tank at Rose Cottage

Soil Human Health

N/A Medium Negligible Neutral The oil storage tank will be removed as part of construction.

Neutral

Documents

Chapter 14 Geology and Soils - Northumberland€¦ · An earthworks Specification in accordance with the HA Series 600 will need to be produced for the scheme as part of the detailed