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M4 Corridor around Newport Design Options Report Volume 1

http://m4newport.com/

Welsh Government

M4 Corridor around Newport

Design Options Report

M4CaN-DJV-GEN-ZG-GEN-RP-CX-0001

1October 2015

CVJV/AAR

3rd

Floor

Longcross Court,

47 Newport Road,

Cardiff

CF24 0AD

Welsh Government M4 Corridor around Newport


M4CaN-DJV-GEN-ZG-GEN-RP-CX-0001 | | 1October 2015 M4CaN-DJV-GEN-ZG_GEN-RP-CX-0001.docx

Contents

Page

1 Introduction 1

2 Vision and Objectives 4

3 Stakeholder Engagement 6

4 Appraisal Criteria 10

5 High Level Option Review 13

6 Shortlisted Options Appraisal 31

7 Summary 80

Tables Table 5.1: Long List of options Considered

Table 6.1: Option M1 - Mainline Appraisal Ch 4+400 – 5+000m



Table 6.4: Option M5 – Mainline Appraisal Ch 8+800 – 11+400m


Table 6.6: Option SR2b – Side Road Appraisal Ch 7+800m, Lighthouse Road

Table 6.7: Option SR3d – Side Road Appraisal Ch 12+250m Nash Road/ Meadows

Road

Table 6.8: Option SR4 - Side Road Appraisal Ch 18+000 North Row

Table 6.9: Option J1 – Junction/Interchange Appraisal Ch 1+500 – 4+400m

Castleton Interchange


Docks Way Junction


Glan Llyn Junction

Table 6.12: Option S1 – Structural Appraisal Ch 8+400 – 8+600m River Ebbw

Structure

Table 6.13: Option G1: Chainage 5+100 to 19+200 – Embankments on Gwent

Levels

Table 6.14: Option D1 - Drainage Appraisal Ch 8+600 – 11+200m River Usk

Crossing

Table 6.15: Option D8 – Drainage Appraisal Ch 21+000m Water Treatment Area

11

Table 6.16: Option D9 – Drainage Appraisal Ch 4+300 – 20+000 Reen Mitigation



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Table 6.17: Option D10 - Drainage Appraisal Ch 4+300 – 20+000m Edge of

Carriageway Drainage Detail

Table 6.18: Option N1 – NMU Appraisal Ch 5+700 – 6+100 Green Lane/ Percoed

Lane

Table 6.19 Option N3 – NMU Appraisal Ch 20+200 Green Moor Lane

Table 7.20 List of options recommended for acceptance

Table 7.2 Summary of effects on land required from the SSSI

Figures Figure 4.1: Process Flowchart for Option Identification and Appraisal

Appendices

Appendix A

Initial, High Level Sift of Options – Appraisal Matrix

Appendix B

Lighthouse Road Options Development File Note

Appendix C

Review of Fence Line Location File Note

Appendix D

Levels Drainage Design File Note

Appendix E

Gradient of Mainline East of Castleton File Note



M4CaN-DJV-GEN-ZG-GEN-RP-CX-0001 | | 1October 2015 Page 1

1 Introduction

1.1 Context

1.1.1 The Welsh Government has awarded a Professional Services Contract for the next stage of Scheme development and environmental surveys for the M4 Corridor around Newport (M4CAN) up to publication of draft Orders and an Environmental Statement. The contract has been awarded to a Joint Venture of Costain, Vinci and Taylor Woodrow with consultants Arup and Atkins, supported by sub-consultant RPS. The team shall be developing proposals in anticipation of publishing draft Orders and an Environmental Statement in spring 2016 and a Public Local Inquiry later that year. This process will then inform the next stage of Ministerial decision making.

1.1.2 Since 1989 there have been various studies to identify the problems and propose possible solutions. The M4 Corridor around Newport WelTAG Stage 1 (Strategy Level) Appraisal concluded that a new section of 3-lane motorway to the south of Newport following a protected (TR111) route, in addition to complementary measures, would best achieve the goals and address the problems of the M4 Corridor around Newport and should be progressed for further appraisal. These options have subsequently formed the basis for the development of the draft Plan, which was published in September 2013 and was the subject of public consultation from September to December 2013.

1.1.3 Having taken into account the responses to this participation process, as well as the appraisals of the draft Plan, the Welsh Government has decided to publish a Plan for the M4 Corridor around Newport. Alongside this Plan, the Welsh Government has published updated strategy-level reports, including a Strategic Environmental Appraisal Statement, to demonstrate how the participation process has informed its decision making. It also announced in July 2014 a revised preferred route, which will protect a corridor for planning purposes. These documents can be accessed from the website http://m4newport.com.

1.2 Purpose of Report

1.2.1 This report provides the details of the design options considered during the option development phase of the Key Stage 3 appraisal process for the M4CaN scheme. The appraisal has taken the published 2014 TR111 scheme as the baseline (referred to from this point on as the ‘conceptual design’ and all options developed have been compared and appraised against the conceptual design.

1.2.2 The purpose of this report is to present the findings of option development to Welsh Government to allow them to make decisions on the scheme to be taken forward.




1.2.3 Alternative designs have been considered which would add value to the conceptual design.

1.2.4 The Welsh Government identified three specific areas for consideration, namely:

1. Interchanges and junctions

2. Geotechnical Mitigation

3. Highway Boundary Treatments (Options for access for maintenance ranging from minimum access tracks through to full access track alongside the length of the scheme).

1.2.5 Additionally, the scope of the report has been expanded to include all aspects of the design where design options were considered which would have resulted in a change to land-take for the scheme, including:

1. Mainline route alignment options

2. Side road options

3. Drainage options

4. River Usk bridge

5. Complementary measures options (Junction 25/25A)

1.2.6 The design options considered are documented and appraised within chapter 6.

1.3 Report Layout

1.3.1 The report is presented in two volumes, as follows:

Volume 1 – main report

Volume 2 – supplementary information, including drawings and technical notes.

1.3.2 This report, Volume 1, is laid out as follows:

a) Chapter 1 – Introduction

b) Chapter 2 – Vision and Objectives, compiles the objectives that inform the option appraisal and decision process.

c) Chapter 3 – Stakeholder Engagement, describes the stakeholder engagement that has been completed by the project team and looks forward to further stakeholder liaison required as the scheme progresses to draft Orders stage.

d) Chapter 4 – Appraisal Criteria, provides a summary of the multi-criteria appraisal used to sift and assess the options.

e) Chapter 5 – High Level Option Review, presents the long list of options identified for consideration. The long list of options is initially appraised and shortlisted options are identified.




f) Chapter 6 – Shortlisted Options Appraisal, comprehensive appraisal comparing the preferred shortlisted option with the conceptual design option.

g) Chapter 7 – Summary.




2 Vision and Objectives

a) The aims of the Welsh Government for the M4 Corridor around Newport are to: Deliver a more efficient and sustainable transport network supporting and encouraging long-term prosperity in the region, across Wales, and enabling access to international markets.

b) Make it easier and safer for people to access their homes, workplaces and services by walking, cycling, public transport or road.

c) To produce positive effects overall on people and the environment, making a positive contribution to the over-arching Welsh Government goals to reduce greenhouse gas emissions and to making Wales more resilient to the effects of climate change.

2.1.1 The Scheme aims to help to achieve or facilitate these aims as part of a wider transport strategy for South East Wales, as outlined within the Prioritised National Transport Plan.

2.1.2 The Transport Planning Objectives (TPOs), or goals, are:

a) TPO 1: Safer, easier and more reliable travel east-west in South Wales.

b) TPO 2: Improved transport connections within Wales and to England, the Republic of Ireland and the rest of Europe on all modes on the international transport network.

c) TPO 3: More effective and integrated use of alternatives to the M4, including other parts of the transport network and other modes of transport for local and strategic journeys around Newport.

d) TPO 4: Best possible use of the existing M4, local road network and other transport networks.

e) TPO 5: More reliable journey times along the M4 Corridor.

f) TPO 6: Increased level of choice for all people making journeys within the transport Corridor by all modes between Magor and Castleton, commensurate with demand for alternatives.

g) TPO 7: Improved safety on the M4 Corridor between Magor and Castleton.

h) TPO 8: Improved air quality in areas next to the M4 around Newport.

i) TPO 9: Reduced disturbance to people from high noise levels, from all transport modes and traffic within the M4 Corridor.

j) TPO 10: Reduced greenhouse gas emissions per vehicle and/or person kilometre.




k) TPO 11: Improved travel experience into South Wales along the M4 Corridor.

l) TPO 12: An M4 attractive for strategic journeys that discourages local traffic use.

m) TPO 13: Improved traffic management in and around Newport on the M4 Corridor.

n) TPO 14: Easier access to local services, residential and commercial centres.

o) TPO 15: A cultural shift in travel behaviour towards more sustainable choices.




3 Stakeholder Engagement

3.1 Introduction

3.1.1 In line with the Costain Vinci Joint Venture’s commitment to active stakeholder engagement, we have held initial meetings with core Statutory Bodies and a cross-section of local communities. This contact gives a good understanding of the significant issues which need to be considered when developing options. As the scheme develops we shall maintain close contact with all parties to ensure their ongoing support for the scheme and our ongoing understanding of their concerns.

3.2 Statutory Bodies and Undertakers

3.2.1 There have been numerous meetings with Statutory Bodies to date as follows:

3.2.2 Newport City Council (6th May 2015 onwards)

3.2.2.1 An initial meeting was held on the 6th May in order to introduce the

Contractor Joint Venture team (CJV) and the Design Joint Venture

(DJV) team, and to establish lines of communication. Newport CC

expressed their support for the scheme, offering to assist with the

progression of the scheme, including providing land ownership and

tenant information. Newport CC also cited a number of requests for

the scheme, including avoiding the landfill site, clean links from

junctions to the Steelworks Access Road (SAR) and Newport

Southern Distributor Road (SDR), balancing ponds to become

amenity areas, and for landscaping to address visual impact.

3.2.3 Monmouthshire County Borough Council (6th May 2015 onwards)

3.2.3.1 An initial meeting was held on the 6th May to introduce the teams and

the scheme. Monmouthshire iterated their support for the scheme, but

stated that they would retain some level of objection to ensure

mitigation is suitably addressed. Main areas of interface were

identified as side roads, NMU connectivity, biodiversity and landscape,

PROWs and noise / air quality. Further meetings have been held, and

continue, on these topics.

3.2.4 Cardiff City Council (8th May 2015 onwards)

3.2.4.1 An initial meeting was held on the 8th May 2015 to introduce the

teams and the scheme. Further meetings were held throughout the

development of the scheme to provide an update on the project and

inform the Non-motorised User Context Study, Wider Economic

Impact Assessment and transport modelling.

3.2.5 South Wales Trunk Road Agent (18th May 2015 onwards)

3.2.5.1 An initial meeting was held on 18th May with the primary objective to

discuss the future maintenance of the motorway, as well as the

reclassification of the existing M4. A key objective would be to




minimise the whole life, operational costs by providing low

maintenance designs and reducing residual risks. The provision of a

new maintenance depot (and salt barn) at Glan Llyn to replace the

existing facility at Wilcrick was discussed, as well as the maintenance

requirements for the Usk Crossing, and the motorway drainage

channels. Further meetings have been held, and continue, on these

topics.

3.2.6 Associated British Ports (27th July 2015 onwards)

3.2.6.1 Associated British Ports (ABP) have a Statutory Undertaker role as

owners and operators of Newport Docks. A meeting was held on the

27th July 2015 to explain the development of the scheme. There were

exchanges of correspondence and subsequent meetings to discuss

the impacts of the scheme and land owner and leasee information.

3.2.7 Newport Harbour Commissioners

3.2.7.1 Newport Harbour Commissioners (NHC) have a Statutory Undertaker

role as navigation authority for the Rivers Usk and Ebbw. Whilst there

have been meetings between the Welsh Government and NHC

during the historical development of the scheme, at the time of writing

this report, meetings in the current phase were yet to take place.

3.2.8 Network Rail

3.2.8.1 Regular engagement has been held with Network Rail throughout

KS3, with particular input sought during the development of each

Approval in Principle for structures that will cross the railway.

3.2.9 Utility Companies

3.2.10 The following utility companies have been engaged during Key Stage 3:

a) BT Openreach

b) Dŵr Cymru Welsh Water

c) National Grid

d) Traffic Wales / Welsh Transport Technology Consultancy

e) Virgin Media

f) Wales & West Utilities

g) Western Power Distribution

3.3 Statutory Environmental Bodies

3.3.1 A key part of the stakeholder engagement is through the operation of the Environmental Liaison Group (ELG) which meets quarterly, and brings together the key statutory consultees (e.g. Natural Resources Wales, Newport CC, Monmouthshire CC, Welsh Government, South Wales Trunk Road Agent).




3.3.2 The purpose of these meeting is both to inform stakeholders of the scheme progress as well as engage them in debate about design and scheme development issues. This ensures the full understanding by the stakeholders of the scheme requirements but also facilitates acceptance of proposals by all parties concerned.

3.3.3 The first introductory meeting with Natural Resources Wales was held on 9th April 2015. Environmental liaison meetings were held every month during KS3 and technical meetings have continued regularly throughout KS3.

3.3.4 Meetings to inform other statutory environmental bodies and to discuss design and environmental mitigation measures have been held with Cadw, Newport City Council and Monmouthshire County Council.

3.4 Other Stakeholders

3.4.1 The following other stakeholders have been engaged during Key Stage 3:

a) Air Products

b) Magor Brewery

c) Solutia

d) TATA

e) Private land owners and other businesses directly affected by the scheme

3.5 Community Engagement

3.5.1 Ten Public Information Exhibitions were held across the Newport area to explain the scheme and introduce the team. These were held in five locations, over two days at each location:

a) Castleton Village Hall – 7th and 8th September, 2015;

b) Caerleon Town Hall – 10th and 11th September, 2015;

c) Nash Community Hall – 14th and 15th September, 2015;

d) Magor Ebenezer Baptist Church – 16th and 17th September, 2015;

e) Newport Lysaght Institute – 25th and 26th September, 2015.

3.5.2 Four additional exhibitions were held at Swansea Bus Station (9th September, 2015), Cardiff St Davids Centre (18th September, 2015), Newport Kingsway Centre (21st September, 2015) and Carmarthen Market (23rd September, 2015).

3.5.3 All fourteen of the exhibitions were very well attended, with 2783 people attending the ten full exhibitions. Generally the scheme received strong support and was well understood, with many registering surprise at how far north the proposed motorway alignment was. Key feedback received and used to inform the options development included:




a) Noise mitigation and landscaping around the west of Magor;

b) Cross-route connectivity for NMUs;

c) Justification for Glan Llyn Junction and the layout proposed for

Magor Junction;

d) Environmental impacts, particularly across the Gwent Levels

SSSI;

e) Drainage impacts across the Levels.




4 Appraisal Criteria

4.1 Areas for Review

4.1.1 Option appraisals have been carried out for the three main areas identified by the Welsh Government (refer to Section 1.2.4) and the five further areas where options were considered which would have resulted in a change to land-take for the scheme (refer to Section 1.2.5).

4.2 Appraisal Method

4.2.1 Option Appraisal has been carried out following the option identification and appraisal protocol as set out below in Figure 4.1.

Figure 4.1: Process Flowchart for Option Identification and Appraisal

Review and agreement of the Objectives

Development of areas for review to meet objectives

Develop long list

High Level Options Review

Workshop to score options against appraisal criteria

Discard options where other options add move value

High level 1st sift of long listed

options

Detailed appraisal of short listed options against appraisal criteria

Short Listed Options

Appraisal

Discarded options where

no added value over the

conceptual design

2nd

sift of shortlisted options

Recommendations for changes to the Conceptual Design

Confirmation of scheme to be developed into preliminary design

4.2.2 The appraisal of the options has been made under a series of consistent headings or topics, as follows:




a) Engineering – assesses the impacts of options upon a wide spectrum of engineering criteria, including:

i. Geometry – an appraisal of the geometric design, and compares (where applicable) to relevant design standards. Also considered departures from standard

ii. Junctions – interaction with road junctions

iii. Side Road Interface – impact the option would have upon the side road network

iv. Rail Interface – impact upon the rail network

v. NMU Interface – impact upon the NMU network (pedestrians, cyclists and equestrians)

vi. Structures – impact upon structures

vii. Flooding and Drainage – impact upon flooding and drainage

viii. Lighting – impact upon lighting

ix. Communications – impact upon highway communications (ITS, telephones, variable message signs, etc)

x. Geotechnics – geotechnical implications of the options

xi. Utility Services – impact upon utility service, including diversions, or protection works

xii. Construction Issues – appraisal of buildability issues

b) WelTAG appraisal criteria, which includes:

i. Economic

ii. Environmental, including the requirements of Section 28G of the Wildlife and Countryside Act with respect to the Gwent Levels SSSIs.

iii. Social aspects

c) Other criteria, including:

i. Traffic impacts

ii. Cost

iii. Safe by design - CDM design considerations of constructability and maintenance

iv. Deliverability

4.2.3 The high level 1st sift of options (Chapter 5) has been undertaken on the basis of presenting all options within a scoring matrix (Volume I, Appendix A), and the above headings (and associated sub-headings) have been scored against a defined scoring mechanism. In each case, the conceptual design is taken as the baseline option and has been scored as zero for all headings. In comparing the alternative design options to the conceptual design, the following 3-point scoring criteria has been adopted:

+1 improvement upon conceptual design




0 little difference to conceptual design

-1 poor performance in relation to the conceptual design

4.2.4 Scores have been summated and a total score for each option provided. However, where an appraisal has been deemed to be exceptionally poor, this has been highlighted as red, and commentary provided in the comments column.

4.2.5 Where more than one option exists for any area, the best performing alternative is shortlisted for more detailed appraisal. Consequently, any option with a better performing alternative has been rejected at the initial sift of options stage.

4.2.6 Options which have been shortlisted have been taken forward into the 2nd sift of options, called the shortlisted options appraisal, see Chapter 6. This more detailed appraisal of options compares the alternative option to the conceptual design, and provides a table summarising the benefits and detriments compared against the conceptual design. This appraisal has been undertaken on qualitative basis, again using the same appraisal criteria as outlined in Section 4.2.2.

4.2.7 Appraisal of options against carbon criteria has not been considered in the level of detail of each option. Transport Planning Objective 10 states: Reduced greenhouse gas emissions per vehicle and/or person kilometre. A summary comment regarding the options recommended and their contribution to achieving TPO 10 is included in the summary section at the end of this report.




5 High Level Option Review

5.1.1 The review areas identified in Section 4.1 have had a number of sub-option designs developed which have been considered and appraised. This section provides an overview of the initial high level first stage sift of options, as outlined in Section 4.2.

5.1.2 An appraisal matrix has been developed which presents the full initial appraisal of options, which includes the associated option scoring methodology (see Section 4.2.3). The full appraisal matrix is presented in Volume I, Appendix A.

5.1.3 Table 5.1, below, provides a summary of the results of the high level sift of options, and presents those options to be taken forward for a more detailed appraisal in Chapter 6.

5.1.4 Drawings or sketches have been provided for the options that were considered for the high level sift of options, and are presented in Volume II of this report. It should be noted that because of the developing status of the design during the design options phase of the study, several of the option drawings are basic sketches or extracts from drawings that are work in progress.




Table 5.1: Long List of options Considered

Option No.

Brief Description Status After Initial Sift

Comments

Mainline

M1 Location along scheme: Chainage 4+400 – 5+000m.

M1a Mainline passing over the Church Lane side road Conceptual design

Refer to Conceptual Design drawing in Volume 2 and to further appraisal in section 6.3.

M1b Mainline lowered and Church Lane side road raised. Mainline passes under Church lane side road.

Short listed Refer to design option sketch in Volume 2 and to further appraisal in section 6.3.

M1c Mainline passing over the Church Lane side road, with Church Lane lowered to reduce the fill requirement for the mainline.

Discarded Option rejected as it causes drainage difficulties at Church Lane.

M2 Location along scheme: Chainage 3+700 – 5+000m

M2a Mainline vertical alignment utilises a 3% gradient Conceptual design


M2b Mainline vertical alignment utilises a 4% gradient with no climbing lane


M2c Mainline vertical alignment utilises a 4% gradient with a climbing lane provided

Discarded Climbing lane appraisal carried out. No climbing lane required. Refer to appraisal in Appendix E to Design Options Report Volume1.


M3a Vertical alignment over Duffryn Rail Crossing providing a headroom clearance of 4.78m

Conceptual design - discarded

Unacceptable headroom clearance for Network Rail. Refer to Conceptual Design drawing in Volume 2.

M3b Vertical alignment over Duffryn Rail Crossing providing a headroom clearance of 5.5m

Chosen design Option accepted. Refer to design option sketch in Volume 2. There would be a small increase in the land required by the scheme from the SSSI due to the increased embankment height.


M4a Horizontal alignment positions the mainline to cross the South Conceptual Refer to Conceptual Design drawing in Volume 2 and to further




Option No.


Comments

Wales Railway 350m east of Green Lane. Results in a high skew crossing of the M4 over the railway

design appraisal in section 6.5.

M4b Horizontal alignment positions the mainline to cross the South Wales Railway 250m west of Green Lane. Produces a more perpendicular crossing of the M4 over the railway


M4c Relocate alignment further to the north, crossing Lighthouse Road and South Wales mainline railway simultaneously

Discarded Refer to design option sketch in Volume 2.

This option would realign the motorway closer to the residential area of Duffryn, which would introduce negative social and environmental effects. The design entailed a triple-stacked structure of M4, Lighthouse Road and railway which would be a high cost structure, and would have resulted in negative landscape effects.


M5a Mainline horizontal alignment over the Newport Docks and the River Usk crossing

Conceptual design


M5b Horizontal alignment altered to introduce a straight alignment on the main span and back span. Realignment to reduce the skew to the River Usk, reducing the length of the crossing.



M6a Mainline horizontal alignment in the vicinity of Solutia, Nash Road and the approach to the Glan Llyn junction

Conceptual design


M6b Mainline horizontal shift to the north by tightening up geometry to avoid impact upon pylon



M7a Horizontal alignment passing through Tata Steel slurry lagoons Conceptual design – chosen design

Refer to Conceptual Design drawing in Volume 2.

Alternative option M7b discarded – see below.

M7b Shift the mainline alignment north into the Tata contaminated land at Tata Steel, to reduce the land take from the SSSI.


Option discounted because of increased uncertainty and risk associated with impacts upon much larger volumes of contaminated material within




Option No.


Comments

the Tata slurry lagoons. This would have resulted in significant cost increases to the project.


M8a Mainline is aligned close to the A4810 Steelworks Access Road (SAR) in the vicinity of the crossing of the South Wales railway at Magor.



Option discarded as the design provided inadequate separation between the proposed M4 mainline and the A4810 Steelworks Access Road. The option would have necessitated considerable lengths of retaining walls and/or earthworks steepening works to provide separation.

M8b Mainline was realigned to the south-east, which provided separation between the proposed M4 and the SAR.

Chosen design Refer to design option sketch in Volume 2.


M9a The proposed M48 to existing M4 link dual carriageway road cross-section is modelled as a dual 2 lane motorway (D2M)


Option rejected because the link road is to be provided as Trunk Road, and not motorway standard

Refer to TD 27/05 Figure 4-1a.

M9b The proposed M48 to existing M4 link dual carriageway road cross-section is modelled as a dual 2 lane all purpose road (D2AP)

Chosen design Further appraisal unnecessary. This area of the scheme is remote from the SSSI land.

Refer to TD 27/05 Figure 4-3a.


M10a Mainline cross-section incorporating a 1.6m wide central reserve with a vertical concrete barrier (VCB). Includes a departure.

Conceptual design – chosen design


Further appraisal unnecessary.

M10b Mainline cross-section incorporates a 1.2m wide central reserve with a VCB, 3.0m hard shoulder and 10.5m wide carriageway (3 lanes). Includes departures.


Initial discussions with representatives from WG, via a Departures Panel, indicated severe concerns over the safety implications associated with this proposed reduced cross-section. Insufficient examples elsewhere on the network are available to fully support the submission of such a departure from TD27/05.




Option No.


Comments

M10c Mainline cross-section incorporates a 2.5m wide central reserve with a VCB. Compliant design (TD27), no departure

Discarded Refer to TD 27/05 Figure 4-1a.

Side Roads

SR1 Location along scheme: Chainage 4+630m - Church Lane

SR1a Church Lane passing under the proposed M4 as an underbridge Conceptual design


SR1b Church Lane passing over the proposed M4 as an overbridge Short listed Refer to design option sketch in Volume 2 and to further appraisal in section 6.8.

SR2 Location along scheme: Chainage 7+400m - Lighthouse Road

SR2a Lighthouse Road as an overbridge over the proposed M4, with the side road alignment along the line of the existing Lighthouse Road

Conceptual design


SR2b Lighthouse Road as an overbridge over the proposed M4, with the side road alignment offline and to the west of the existing Lighthouse Road

Short listed Refer to design options file note in Appendix B to Volume 1 of this Design Options Report and to further appraisal in section 6.9.

SR2c Lighthouse Road as an overbridge over the proposed M4, with the side road alignment offline and to the east of the existing Lighthouse Road

Discarded Refer to design options file note in Appendix B to Volume 1 of this Design Options Report. Option would directly impact upon farm and/or residential buildings with this alignment

SR3 Location along scheme: Chainage 12+250m – Nash Road/Meadows Road

SR3a Replacement side road provided to the west of Nash Road, connecting Nash Road on the southern side of the proposed motorway to Nash Road on the northern side of the motorway. Local alterations to the Meadows Road/Nash Road junction on the northern side of the motorway to maintain connectivity.

Conceptual design


SR3b Replacement side road provided to the west of Nash Road, connecting Nash Road on the southern side of the proposed motorway to Nash Road on the northern side of the motorway. An extended northern section connects to a locally amended Nash


Would require excessive length of new side road and would enclose larger area of land west of Nash Road.




Option No.


Comments

Mead into the industrial estate. The Meadows Road/Nash Road junction on the northern side of the motorway is stopped up.

SR3c Replacement side road provided to the east of Nash Road, connecting Nash Road on the southern side of the proposed motorway to Meadows Road on the northern side of the motorway. The alignment is placed to the west of the commercial property on Meadows Road. The Meadows Road/Nash Road junction on the northern side of the motorway is stopped up. A connection is provided through the industrial estate between Nash Mead and Nash Lane.


Option rejected due to unacceptable vertical gradient required on the northern approach to the overbridge bridge.

SR3d Replacement side road provided to the east of Nash Road, connecting Nash Road on the southern side of the proposed motorway to Meadows Road on the northern side of the motorway. The alignment is placed to the east of the commercial property on Meadows Road. The Meadows Road/Nash Road junction on the northern side of the motorway is stopped up. A connection is provided through the industrial estate between Nash Mead and Nash Lane.


SR4 Location along scheme: Chainage 18+000m – North Row

SR4a North Row diverted approximately 15m to the east of its current alignment, but aligned parallel to the existing road, passing over the proposed M4CaN on an overbridge. The old side road would be stopped up.

Conceptual design


SR4b Existing North Row stopped up, and realigned to the east of its current alignment to avoid impacting upon existing electricity pylon

Discarded Refer to design option sketch in Volume 2. Option rejected due to unacceptable vertical gradient required on the northern approach to the overbridge bridge.

SR4c Existing North Row stopped up, and realigned to the west of its current alignment to avoid impacting upon existing electricity pylon


SR4d North Row stopped up, and traffic diverted east to connect into Bareland Street


Option rejected due to journey time and access impacts to local




Option No.


Comments

communities.

Junctions and Interchanges

J1 Location along scheme: Chainage 1+500 – 4+400m – Castleton Motorway Interchange

J1a Mainline stays on-line but replaces existing motorway carriageway before crossing over the A48 and down towards Duffryn. Eastbound A48(M) merges with the M4 eastbound diverge slip to form a new A48(M) to the north of the motorway corridor, whilst the link to the new M4 crosses the A48(M) to the south of the M4 and then crosses the M4 motorway to merge into the M4. The westbound link from the M4 to the A48M lies to the south of the motorway corridor, whilst the old M4 westbound link to the A48M crosses the mainline to the east of the current overbridge.

Conceptual design

Refer to Conceptual Design drawing in Volume 2 and to further appraisal in Section 6.12.

J1b Mainline stays on-line but replaces existing motorway carriageway before crossing over A48 and south-eastwards towards Duffryn. Eastbound links are located to the north of the proposed motorway corridor with the A48(M) merging with the eastbound diverge slip to form new A48(M), whilst the westbound links remain to the south.

Short listed Refer to design option sketch in Volume 2 and to further appraisal in Section 6.12.

J1c This option was derived from the 2006 TR111 layout, whereby the proposed mainline carriageway is diverted to the north of the existing corridor before passing beneath the existing M4 carriageway and over the A48. The existing M4 carriageway remains largely intact to accommodate the A48(M)


Option rejected due to the excessive volume of cut generated in the slopes and the large extent of land-take required to the north of the M4 corridor. Additionally, it would be difficult to excavate under the existing M4 and maintain traffic flow during construction.

J1d Similar to J1c, except the mainline carriageway veers to the north of the existing approximately 1km to the west of the A48(M) overbridge to reduce the impact to the north of the M4. The existing M4 carriageway remains largely intact to accommodate the A48(M).


Option rejected due an increase in the number, and cost, of structures compared to other options. This option would also have a significant impact upon New Park Farm. It would be difficult to maintain existing traffic flows during construction, leading to complex traffic management and potential safety concerns.

J2 Location along scheme: Chainage 7+800 – 9+800m – Docks Way Motorway Junction

J2a Grade-separated roundabout junction on the proposed motorway Conceptual Refer to Conceptual Design drawing in Volume 2 and to further




Option No.


Comments

connecting a new dual carriageway link road between the motorway and the Newport Southern Distributor Road (SDR). The new link road is aligned along the eastern edge of the Docks Way landfill site, and connects into the new Docks Way junction on the northern side

design appraisal in Section 6.13.

J2b Grade-separated roundabout junction on the proposed motorway connecting a new dual carriageway link road between the motorway and the SDR. The roundabout is located 200m further to the west in an effort to reduce the interface between the east-facing slip roads and the cable-stayed structure. A new link road would be aligned along the eastern edge of the Docks Way landfill site, passing under the proposed M4, connecting into the new Docks Way junction on the southern side.


The alignment of the dual carriageway link road as it loops under the proposed M4, and connects into the Docks Way junction roundabout on the southern side, results in significant impact to industrial buildings within Newport Docks

J2c Grade-separated roundabout junction on the proposed motorway connecting a new dual carriageway link road between the motorway and the SDR. The roundabout is located 200m further to the east in an effort to reduce the interface between the east-facing slip roads and the cable-stayed structure. A new link road would be aligned along the eastern edge of the Docks Way landfill site, passing under the proposed M4. Immediately on the southern side of the motorway a new roundabout is provided enabling the link road an instant change in direction to the west to connect into the new Docks Way junction on the southern side. Reduced impact on buildings within Newport Dock


The alignment of the dual carriageway link road results in direct impacts to industrial buildings within Newport Docks

J2d Grade-separated roundabout junction on the proposed motorway connecting a new dual carriageway link road between the motorway and the SDR. The roundabout is located 200m further to the east in an effort to reduce the interface between the east-facing slip roads and the cable-stayed structure. A new link road would be aligned along the eastern edge of the Docks Way landfill site, connecting into a new roundabout in the northern side of the M4. From this roundabout, the link road connects into the new Docks Way junction on the northern side.





Option No.


Comments

J3 Location along scheme: Chainage 14+200 – 15+900m – Glan Llyn Motorway Junction

J3a Grade-separated roundabout junction on the proposed motorway connecting a new dual carriageway link road between the motorway and the A4810 Steelworks Access Road (SAR). Main junction roundabout positioned to the east of Monks Ditch.

Conceptual design


Requires diversion of two National Grid overhead lines

J3b Grade-separated roundabout junction on the proposed motorway connecting a new dual carriageway link road between the motorway and the SAR. Main junction roundabout positioned to the west of Monks Ditch.


Accommodates two sets of National Grid overhead cables and pylons

J3c Grade-separated dumb-bell roundabout junction on the proposed motorway connecting a new dual carriageway link road between the motorway and the SAR.


Traffic appraisal demonstrated a grade-separated dumb-bell junction was unable to provide sufficient traffic capacity for design year traffic.

J4 Location along scheme: Chainage 20+850m – Newport Road/ Steelworks Access Road Junction

J4a Newport Road/ Steelworks Access Road junction is provided as an at-grade roundabout with an inscribed circle diameter of 58m

Conceptual design – chosen design


J4b Newport Road/ Steelworks Access Road junction is provided as an at-grade 4-arm traffic signal junction.


Traffic signal junction was assessed to provide insufficient traffic capacity for design year traffic under new core scenario and diverted additional traffic through Magor and Undy villages towards Junction 23

J5 Location along scheme: Chainage 23+600m – M48 Roundabout

J5a At grade roundabout located at the new western terminal point of the M48 motorway, ICD of 100m. Dual two lane link to J23 roundabout



Traffic appraisal demonstrated an at-grade roundabout of these dimensions was unable to provide sufficient traffic capacity for design year traffic.

J5b At grade partially signalised roundabout, ICD of 100m with segregated free flow left turn lanes. Dual three lane link to J23 roundabout


Traffic appraisal demonstrated an at-grade roundabout of these dimensions was unable to provide sufficient traffic capacity for design year traffic.




Option No.


Comments

J5c At grade signalised ‘hamburger’ style through-about roundabout, with dedicated link for east-bound traffic from the reclassified M4 to the new M4

Chosen option Refer to design option sketch in Volume 2.

J6 Location along scheme: Chainage 23+600m – Junction 23

J6a Grade-separated roundabout motorway junction, comprising a two-bridge elongated roundabout, ICD of 100m. Solution utilised the existing B4245 underbridge (under existing M4)



Traffic appraisal demonstrated this form of junction was unable to provide sufficient traffic capacity for design year traffic.

J6b Grade-separated signalised roundabout motorway junction, comprising a two-bridge elongated roundabout, ICD of 90m. Solution utilised the existing B4245 underbridge (under existing M4)


Traffic appraisal demonstrated this form of junction was unable to provide sufficient traffic capacity for design year traffic under new core scenario.

J6c Grade separated M4 junction, with westbound free-flow link road between M4 and D2AP link to existing Junction 23A. New signalised junction and roundabout on B4245 to provide access to M4. Eastbound off, eastbound on and westbound on slip roads connected to M48 “through-about” (Westbound on slip makes use of existing M48 to M4 link road.)

Chosen option Refer to design option sketch in Volume 2.

J6d As J6c, but including an additional eastbound free-flow link road between D2AP and M4 eastbound. M48 junction no longer “through-about”, but conventional signalised roundabout.


Considered an over-provision of traffic capacity, rejected due to costs.

Structures

S1 Location along scheme: Chainage 8+400 – 8+600m – River Ebbw Structure

S1a River Ebbw bridge comprising a 193m length span which crossed over the River Ebbw, the flood bund, sea wall reen and access track

Conceptual design

Refer to Conceptual Design drawing in Volume 2 and to further appraisal in Section 6.15.

S1b Reduced length River Ebbw bridge with a span of 169m, which only spanned the River Ebbw. The sea wall reen was provided in a separate culvert adjacent to the bridge and the access track along flood bund was provided for in a separate adjacent underbridge


Option rejected because the provision of New Dairy Farm overbridge (Option S1c) would negate the need for an underpass




Option No.


Comments

S1c Reduced length River Ebbw bridge with a span of 169m, which only spanned the River Ebbw. The sea wall reen was provided in a separate culvert adjacent to the bridge. Add New Dairy Farm overbridge to the west of the River Ebbw. Divert access track over new overbridge and do not provide the underpass.


Geotechnical

G1 Location along scheme: Embankments on Gwent Levels

G1a Embankments designed with 1 vertical to 2 Horizontal (1:2) side slopes.

Conceptual design

Refer to further appraisal in Section 6.16.

G1b Steepen side slopes to 1:1.5 to reduce earthworks and land take. Short listed Refer to further appraisal in Section 6.16.

G1c Slacken side slopes to 1:2.5 to reduce earthworks risk with soft underlying ground.

Discarded Option rejected due to the additional impact on SSSI where the stability risks can be mitigated through geogrid basal reinforcement.

G2 Location along scheme: Castleton interchange cutting

G2a Designed with 1:3 side slopes due to lack of ground investigation during early design stages and poor nature of rock.

Conceptual design

Conceptual design accepted.

G2b Steepen side slopes to 1:2 to reduce earthworks and land take. Discarded Option rejected due to increase in cost and construction complexity as rock stability measures required and also negative impact on essential landscape mitigation.

G3 Location along scheme: Castleton interchange embankment

G3a Embankments designed with 1:2 side slopes.

Conceptual design

Conceptual design accepted.

G3b Steepen side slopes to 1:1.5 to reduce earthworks and land take.

Discarded Option rejected due to increase in cost for imported fill and geogrid reinforcement and negative impact on essential landscape mitigation.

Drainage

D1 Location along scheme: Chainage 8+600 – 11+200m – River Usk Crossing Drainage Solution

D1a For West of River Usk crossing, collect drainage from carriageway and outfall into ABP Docks through petrol interceptor. For East of River Usk, collect drainage and outfall into dock on east bank of

Conceptual design

Refer to design option sketch in Volume 2 and to further appraisal in Section 6.17.




Option No.


Comments

River Usk through petrol interceptor.

D1b Collect and carry all surface water from the R Usk bridge to an existing pond on the eastern side of the R Usk, and a secondary waterway

Discarded Option rejected because it would result in WG sharing the use of outfalls with other areas of the dock. Lack of control unacceptable

D1c Collect and carry all surface water from the R Usk bridge to new pollution treatment lagoon on the eastern side of the R Usk, and discharge into the R Usk through a new ditch


D2 Location along scheme: Chainage 4+700m – Water Treatment Area No 3

D2a Water treatment area no. 3 located to north of Church Lane to provide attenuation lagoon for side road drainage associated with the provision of Church Lane being an underbridge


Option rejected because the design of Church Lane changed to an overbridge solution, and WTA no. 3 no longer required

D2b Remove pond to avoid OH pylons and redesign the drainage network to accommodate drainage elsewhere.

Chosen Option Option accepted. Refer to sketch in Volume 2. No change to the land required from the SSSI.


D3a Water treatment area no. 4 is located adjacent to All Saints Church Conceptual design - discarded

Option rejected because the vertical alignment of highway was revised to avoid the need to divert overhead electricity cables at CH5990 (conceptual design chainage), therefore WTA no. 4 was located in the wrong location to suit the alignment. i.e. the low point of the alignment and thus the discharge point for the drainage is no longer at the position of the WTA4 in the conceptual design.

D3b Move pond to chainage 5+800 and split into separate ponds either side of the M4 mainline to allow sufficient falls to the drainage network

Chosen Option Option accepted. Refer to sketch in Volume 2.

Whilst this option moves the location of the WTA in to the SSSI land, the position is essential to be compatible with the highway alignment which avoids diversion of overhead electricity cables at CH 5990 (conceptual design chainage). The low lying nature of the land and high ground water levels mean that it would not be possible to locate the WTA remote from the alignment low point and run a connecting length of pipe. The alternative, to move the overhead electricity cables, would give increases in project cost and programme and would, itself,




Option No.


Comments

disrupt the SSSI. The proposed location of the WTA4 for option D3b is considered to offer an appropriate balance between delivery of the scheme, impacts on the SSSI and impacts on overhead electricity cables.


D4a Water treatment area no. 5 is located to the south of the M4 carriageway, between Pont-y-Cwcw and the Sea Wall Reen


Option rejected because WTA was located in a field which was allocated for future pylon construction by National Grid.

Revised location (D4b) was also beneficial to minimising earthworks volumes. The conceptual design location of the pond is within SSSI land.

D4b Relocate WTA to adjacent to Duffryn Rail line Chosen Option Option accepted. Refer to sketch in Volume 2. The proposed location is also within SSSI land and is of a similar area so there is no material net change to the land required from the SSSI.


D5a Water treatment area no. 7 is located to the west of Julians Reen on south side of M4 carriageway


The conceptual design location of the pond is not within SSSI land. Option rejected in order to locate the pond to north of carriageway in order to reduce impact on SSSI. Option also had a potential clash with OH pylons

D5b Pond moved to the north of carriageway Chosen Option Option accepted. Refer to sketch in Volume 2. The proposed location is also not within SSSI land.


D6a Water treatment area no. 8 is located to the north of the M4 carriageway, located within known contaminated land associated with the Tata-owned secondary reed bed


The conceptual design location of the pond is within SSSI land. Option rejected because WTA located in a contaminated reed bed area used by Tata Steel, not appropriate for water treatment

D6b WTA moved east to avoid impacting upon the Tata reed bed area Chosen Option Option accepted. Refer to sketch in Volume 2.The proposed location is also within SSSI land and is of a smaller area so there is net reduction to the land required from the SSSI.

D6c WTA moved into an existing pond area to the south of the existing Discarded Option rejected for environmental reasons, because of the ecological




Option No.


Comments

Tata reed beds, on the southern side of the M4. This area has been recently ecologically improved.

area.

D6d WTA moved to an area south of the proposed Glan Llyn Junction Discarded Option rejected because it is of restricted use because of the proximity by a series of OH Pylons.


D7a Water treatment area no. 10 is located on the southern side of the proposed M4, opposite the Europark Development.


Option rejected because the M4 mainline horizontal alignment changed, resulting in a clash with the original location for WTA 10. The conceptual design location of the pond is within SSSI land.

D7b WTA remains on southern side of M4, but is moved to the east by approximately 400m

Chosen Option Option accepted. Refer to sketch in Volume 2. The proposed location is also within SSSI land and is of a similar area so there is no material net change to the land required from the SSSI.


D8a Route surface water runoff from the new M4 adjacent to Junction 23A in a south westerly direction to Water Treatment Area 11, located immediately to the south of the Paddington to Fishguard rail link. Resulted in drainage runs of up to 12m deep. Large diameter pipes required to be constructed below the Paddington to Fishguard rail link

Conceptual design

Refer to conceptual design drawing volume 2 and to further appraisal in section 6.18.

D8b Raise the alignment of the B4245, (Newport Road) and the M4 mainline. This would allow the majority of the M4 between Ch 20400 and 21000 to drain in an easterly direction into the catchment of the St Brides Brook/Mill Reen. Avoids the need to lay large diameter pipes below the main railway line

Discarded Option rejected because to construct the attenuation ponds, it would be necessary to prevent flood water from the reen entering the WTA. This option would result in a loss of flood plain storage and potentially flood conveyance within the Mill Reen, resulting an an increase to flood risk in the locality.

D8c Utilise the area between the existing Junction 23A and the new M4 as a secondary WTA. Locate the reed bed immediately to the east of St Brides Road. This option would mean the WTA (and corresponding pipework) would be considerably smaller.

Discarded Option rejected as it would be constrained by the depth of excavation required to accommodate the storage lagoon. Current ground levels vary between 23 to 28m AOD. The pond would need to have an invert level of between 12.0 and 13mAOD, (depending on dilution requirements). This would have resulted in the requirement to install large diameter pipes through the bridge structure at St. Brides Road in order to transfer flow from the east of St. Brides Road. It was considered unlikely that there would be sufficient headroom in the




Option No.


Comments

system to prevent flooding (to the required level) in the upstream network by progressing with this option.

D8d Same as above but with a third pond located to the north east of St. Brides Road. 11a flows can be conveyed south into the catchment area for WTA10.

Short listed Refer option sketch in Volume 2 and to further appraisal in section 6.18.

D9 Location along scheme: Chainage 4+300 – 20+000 – Development of Reen Mitigation Strategy

D9a Provide compensatory reens along the whole of the Levels, on both sides of the proposed M4 where possible.

Conceptual design


D9b Provide compensatory reens along the whole of the Levels on the north side of M4 motorway carriageway with field ditches on south. Where possible use existing ditches instead of placing new ones on the south of highway to fit within the historical landscape

Short listed Refer option sketch in Volume 2 and to further appraisal in section 6.19.

D10 Location along scheme: Chainage 4+300 – 20+000 – Edge of Carriageway Drainage Detail

D10a Grass-lined channel Conceptual design

Refer to further appraisal in section 6.20 and to options appraisal in Appendix D.

D10b Concrete-lined channel Discarded Option rejected because it did not provide the environmental benefits, including initial water quality treatment, of grass-lined channel. Concrete-lined channel also vulnerable to cracking (through settlement)

D10c Rockfill channel Short listed Refer to further appraisal in section 6.20 and to options appraisal in Appendix D.

Highway Boundary Treatments

H1 Location along scheme: Embankments on Gwent Levels

H1a Highway boundary fence offset 3m from the toe of the embankment/ cut off ditch.

Conceptual design

Refer to detailed option evaluation in Appendix C and to further appraisal in section 6.21.

H1b Move highway boundary fence closer to the toe of embankment to reduce impact on SSSI

Chosen Option Refer to detailed option evaluation in Appendix C and to further appraisal in section 6.21.

Complementary Measures




Option No.


Comments

For complementary measures options, refer to the Complementary Measures report, M4CaN-DJV-GEN-ZX_GEN-RP-CX-001

Non-Motorised Users (NMU)

N1 Location along scheme: Chainage 5+700 – 6+100 – Green Lane/Percoed Reen

N1a Green Lane diverted under M4 mainline in an underbridge to the west. Percoed Lane diverted into same underbridge to maintain connectivity. Resultant solution provides for NMU and Private Means of Access (PMA).

Conceptual design


N1b Green Lane and Percoed Lane both stopped up. No connectivity provided across M4 for NMUs or PMA at this location.

Discarded Lack of connectivity for NMUs unacceptable to stakeholders.

N1c Green Lane diverted over M4 mainline across an overbridge to the west. Percoed Lane diverted onto same overbridge to maintain connectivity. Resultant solution provides for NMU and PMA access across the M4.

Discarded Geometry of M4 would require alteration for a Green Lane overbridge solution. Green Lane would be on a significant embankment, as the M4 climbs to cross the South Wales mainline. The resultant additional cost was considered unacceptable.

N1d Green Lane diverted over M4 mainline on an overbridge to the west. Percoed Lane diverted onto same overbridge to maintain connectivity. Resultant solution provides for NMUs only (lightweight structure).

Discarded Geometry of M4 would require alteration for a Green Lane overbridge solution. Green Lane would also be on a significant embankment as the M4 climbs to cross the South Wales mainline. The resultant additional cost was considered unacceptable.

N1e Green Lane diverted under M4 mainline in an underbridge to the west. Percoed Lane diverted into same underbridge to maintain connectivity. Resultant solution provides for NMUs only (reduced headroom structure).

Discarded This solution would have resulted in a significant diversion for NMUs on the Cardiff-Newport Cycle track that would have been unacceptable.

N1f Percoed Lane diverted over M4 mainline on an overbridge to the east. Green Lane connected into Percoed Lane, providing NMU and PMA access across the M4.

Discarded An overbridge structure would have been more costly to provide for PMA access versus only NMUs, with a central pier required in the proposed motorway. The resultant additional cost was considered unacceptable.

N1g Percoed Lane diverted under M4 mainline through an underbridge to the east. Green Lane connected into Percoed Lane, providing NMU and PMA access across the M4.

Discarded Geometry of M4 would require alteration for a Percoed Lane underbridge solution. The resultant additional cost was considered unacceptably high.




Option No.


Comments

N1h Percoed Lane diverted over M4 mainline on an overbridge to the east. Green Lane connected into Percoed Lane, providing NMU only access across the M4 (lightweight structure).

Short-listed Refer to design option sketch in volume 2 and to further appraisal in section 6.22.

N1i Percoed Lane diverted under M4 mainline through an underbridge to the east. Green Lane connected into Percoed Lane, providing NMU only access across the M4 (reduced headroom structure).


N1j Percoed Lane diverted under M4 mainline through an underbridge to the east. Green Lane stopped up. NMU only access across the M4 (reduced headroom structure).


N1k Percoed Lane diverted over the M4 mainline over an overbridge to the east. Green Lane stopped up. NMU only access across the M4 (lightweight structure).

Discarded An overbridge structure would have been more costly to provide for PMA access versus only NMUs, with a central pier required in the proposed motorway. The resultant cost was considered unacceptable.

N1l Green Lane diverted under M4 mainline in an underbridge to the west. Percoed Lane stopped up. Resultant solution provides for NMUs only (reduced headroom structure).


N1m Green Lane diverted over M4 mainline on an overbridge to the west. Percoed Lane stopped up. Resultant solution provides for NMUs only (lightweight structure).


N2 Location along scheme: Chainage 8+400 – Wales Coastal Path

N2a Provide for the Wales Coast Path to cross M4 through the Ebbw River structure. Diverting PMA and NMU route alongside the proposed motorway from the point where the motorway would cross the existing alignment of the NMU and PMA route.

Conceptual design


N2b Provide for the Wales Coast Path to cross M4 through a separate structure behind the abutment of the Ebbw River structure. Diverting PMA and NMU route alongside the proposed motorway from the point where the motorway would cross the existing alignment of the NMU and PMA route.

Discarded The length and geometry of the diversion were unacceptable to stakeholders.

N2c Provide for the Wales Coast Path and PMA route to cross the M4 Short listed Refer to design option sketch in volume 2 and to further appraisal in




Option No.


Comments

using an overbridge provided online to the existing NMU and PMA route.

section 6.23.

N3 Location along scheme: Chainage 20+220 – Green Moor Lane

N3a Maintain Green Moor Lane, diverting alignment under Llandevenny Rail bridge. Maintain vehicular access across the M4 (existing reduced headroom under SAR bridge).

Conceptual design

Refer to conceptual design drawing in volume 2 and to further appraisal in section 6.24.

N3b Stop up Green Moor Lane, do not provide access across the M4 Discarded Lack of connectivity unacceptable to stakeholders

N3c Maintain Green Moor Lane, diverting alignment under Llandevenny Rail bridge. Access provided for NMUs only.

Discarded No alternative vehicular access to allotments to the east of the M4 provided. Unacceptable to stakeholders

N3d Maintain Green Moor Lane, diverting alignment under Llandevenny Rail bridge. Access under M4 provided for NMUs only. Alternative vehicular access to allotments provided from Blenheim Close.

Short listed Refer to design option sketch in volume 2 and to further appraisal in section 6.24.

N3e Maintain Green Moor Lane on its current alignment, passing over the M4 on overbridge, or via an underbridge.

Discarded Unacceptable vertical geometry - gradients for either an overbridge or underbridge solution too severe.

N3f Stop up existing Green Moor Lane. Divert to the north, connecting into existing SAR roundabout. New Green Moor Lane alignment passing over M4 on overbridge.

Discarded Unacceptable vertical geometry with the gradient too severe.




6 Shortlisted Options Appraisal

6.1 Introduction

6.1.1 Each option shortlisted from Section 6 for more detailed evaluation is appraised in the tables below in line with the methodology described in Section 4.

6.2 Costs

6.2.1 In our determination of cost effects, we have considered positive and negative changes to the overall delivery budget and the likely impact on maintenance.

6.3 Mainline Carriageway Option M1: Chainage 4+400 – 5+000m

6.3.1 The conceptual design envisages the M4 mainline vertical alignment falling from the Castleton interchange using a 3% gradient before being levelled off to keep the alignment approximately 8m above ground level as it passes over Church Lane. The proposed section of carriageway with a 3% gradient would run from a point where the new motorway crosses the A48 to a point approximately 750m to the east. The motorway would therefore be on embankment throughout this section with the requirement for substantial import of fill material. Church Lane would remain on its existing alignment, requiring only minor improvements for junction connections and forward visibility.

6.3.2 The mainline alignment in this vicinity is fully compliant with the DMRB with no departures from standard.

6.3.3 The mainline drainage would drain longitudinally via edge of carriageway concrete channels in this area, discharging to water treatment areas (WTA) adjacent to the scheme. Church Lane, under the M4 would be a low point. It would not be possible to connect this back into the mainline drainage and it would therefore require its own WTA and outfall point. The most convenient location for this additional WTA would be a small parcel of land immediately to the east of the Duffryn Link roundabout, but this would impact upon an existing overhead electricity pylon. The most convenient drainage solution would be to connect the side road drainage back into the existing Newport County Council (NCC) surface water drainage network, which would require approval of NCC.

6.3.4 Design Option M1b proposes an alternative alignment which inverts the mainline and side road such that, compared to the conceptual design, the mainline would be lowered and Church Lane raised to pass over the mainline on a bridge.

6.3.5 The key considerations of option M1 are:

a) Aim to minimise the footprint of the works

b) Aim to reduce the cost of the scheme

c) To provide more efficient surface water drainage solution for Church Lane

d) To minimise disruption during construction of earthworks movements




6.3.6 Appraisal


Sub-Option Number: M1b

Benefits Detriments

Weltag Economy Reduction in the scheme cost.

None identified.

Environment Reduced construction stage disruption from earthworks. Smaller works footprint. Does not change the land required from the SSSI.

None identified.

Social Less land-take and CPO required from the Golf Club required as the earthworks slopes do not extend as far as the conceptual Design.

Disruption to side road during construction

Engineering Long term Simpler vertical geometry as the main line carriageway continues down from Castleton at a grade of 4% to cross Church Lane at grade. Church Lane is diverted and re-aligned over the mainline to tie back into the Duffryn Link Road at a new roundabout.

None identified.

Short term Reduced earthworks movements. Utilities in Church Lane will need to be diverted – Conceptual Design left the existing side road (and utilities) in place.

Traffic Long term No change from the conceptual design.

Short term No change from the conceptual design.

Safe by Design

Long term No change from the conceptual design.

Short term Off-line construction removes risk of conflict with traffic on Church Lane. Reduced earthworks movements.

None identified.

Deliverability Cost Saving in bridge construction as deck only carries a side road compared to the full motorway for the conceptual design. As the mainline runs at-grade there is a saving of 250,000 m3 fill

None identified.

Risk Removes risk of conflict with traffic on Church Lane.

None identified.

Buildability The proposed structure is off-line and smaller than the conceptual design would require.

None identified.

Programme Off-line construction would allow more flexibility in the program.

None identified.

6.3.7 Changing the mainline alignment by lowering mainline would deliver cost savings as a result of reduced bridge costs and reduced earthworks movements. The option M1b alignment would reduce the scheme footprint and would not require any additional SSSI land. It is therefore recommended Option M1b is accepted and that the scheme progresses with the revised alignment.





6.4.1 The conceptual design included a 3% maximum vertical gradient along the entire length of the M4CaN scheme, which is the desirable maximum grade for a motorway (as stated in DMRB TD 9/93). In this vicinity, utilising a 3% gradient coming down from the Castleton Interchange, the conceptual design resulted in a significant earthworks embankment between the Interchange and Church Lane, of up to 18m in height. This imposed a requirement for a substantial import of fill material.

6.4.2 Design Option M2b proposes a 4% maximum gradient for the mainline in this location. This would enable the mainline to be lowered from the Castleton Interchange more quickly reducing earthworks import requirements, and consequently reducing the footprint of the works.


a) Aim to minimise the footprint of the works

b) Aim to reduce the cost of the scheme

c) To minimise disruption during construction of earthworks movements




6.4.4 Appraisal



Benefits Detriments

Weltag Economy Reduction in the scheme cost.

None identified.

Environment Reduced construction stage disruption from earthworks. Smaller works footprint. Does not change the land required from the SSSI.

None identified.

Social Less land-take and CPO required from the Golf Club required as the earthworks slopes do not extend as far as the conceptual design.

None identified.

Engineering Long term Reduced works footprint. Reduced land take required from the SSSI.

Short term Reduced earthworks movements None identified.

Traffic Long term No change from the conceptual design

Short term No change from the conceptual design

Safe by Design

Long term No change from the conceptual design


Deliverability Cost The lower embankments result in a saving of 220,000 m3 fill compared to the Conceptual Design

None identified.

Risk None identified. None identified.

Buildability Reduction in volume of fill required None identified.

Programme Programme advantage of reduced placement of material

None identified.

6.4.5 The proposed change to the vertical alignment, to incorporate a 4% longitudinal gradient was assessed and the traffic flows, and HGV percentages, were determined to be insufficient to require a climbing lane. Therefore no climbing lane is proposed with the alternative. Changing the mainline alignment to incorporate a 4% gradient would reduce the import fill requirements for the scheme and this would have the effect of reducing the footprint of the scheme. The option does not change the land taken from the SSSI. The alternative would deliver cost and programme savings. It is therefore recommended that Option M2b is accepted and the scheme progresses with the revised alignment.


6.5.1 The conceptual design continues from the existing Duffryn Link Road corridor to cross the mainline railway in the vicinity of Fox Covert at a high skew angle, although this helps to minimise the impact upon the Wentlooge Levels to the south by keeping the proposed new motorway to the as far to the northern extent of the SSSI as practical, and provide a perpendicular crossing at Lighthouse Road. However, this results in a high skew crossing (approximately 70 degrees) of the South Wales Mainline railway, which would result in a high cost structure.

6.5.2 Design option M4b proposes an alternative alignment which aligns the M4 mainline to the south of the conceptual design, resulting in the alignment crossing Green Lane some 250m to the southwest. This results in a reduced skew structure (approximately 45 degrees) over the railway and aligns the




mainline further away from the residential area of Duffryn. However, the length of the alignment would be some 200m longer.

6.5.3 The key considerations of option M4b are:

a) The footprint of the scheme

b) The impact upon the SSSI

c) The cost of the scheme – reduce skew of railway bridge structure

d) Impact upon residential area of Duffryn




6.5.4 Appraisal



Benefits Detriments

Weltag Economy Reduced scheme cost None identified.

Environment Alignment lies further away from residential areas of Duffryn and therefore reduced noise impact to outskirts of Newport.

The alignment has a greater impact on the Levels and the SSSI as it extends further south and crosses the railway line 600m further to the west than the conceptual design

Social Alignment lies further away from residential areas of Duffryn and therefore reduced noise impact to outskirts of Newport.

None identified.

Engineering Long term Smaller bridge to maintain. Tighter horizontal geometry required to straighten alignment over railway line (reverse curve from Lighthouse Road into a 1020m bend)

Short term Skew angle of the railway bridge reduced from approximately 70 to 45 degrees.

None identified

Traffic Long term No change from the conceptual design.

Short term No change from the conceptual design.

Safe by Design

Long term Smaller bridge to maintain. None identified

Short term Shorter bridge beams; lighter lift weights, fewer lifts over the railway, shorter bridge.

None identified

Deliverability Cost Shorter direct span for bridge over railway. Reduced cost of structure.

Additional 200m of carriageway construction

Risk Additional impact upon the SSSI – risk of objection to the scheme.

Buildability Simpler bridge construction over the railway.

None identified

Programme More simple bridge construction - reduced construction programme.

Alignment lies outside extents of TR111

6.5.5 The proposed change to the horizontal alignment would shift the alignment to the south of the conceptual design and reduced the skew of the bridge crossing over the South Wales Railway mainline from 70 to 45 degrees. This would reduce the cost of the bridge structure and reduce programme risk.

6.5.6 However, the horizontal shift would align the motorway away from the TR111 published alignment and further into the SSSI, and is therefore considered unacceptable. The option M4b was therefore rejected in favour of the conceptual design.


6.6.1 The conceptual design for the mainline over the Newport Docks and River Usk crossing section utilised a horizontal geometry compliant to the DMRB for a design speed of 120kph. The alignment passed directly over the North Dock Cut, crossing the River Usk on a skew of 57 degrees, skirting the southern edge of Stephenson Street Industrial Estate. The bridge crossing over the




River Usk required a clear span of 500m as there is a requirement to keep the bridge piers outside of the wetted channel of the river.

6.6.2 Design Option M5b proposes a changed horizontal alignment of the mainline to reduce the skew over the River Usk by 5 degrees. The alignment changes also straightened M4CaN horizontal alignment over the bridge, removing curvature from the main span and the back spans of the bridge. This would simplify construction techniques for the bridge. The alignment changes involved tightening the mainline radius on the eastern side of the bridge from 1020m to 720m, which is a 1-step relaxation, and incorporated a 1-step relaxation in stopping sight distance. This is a permissible combination of relations as the location is away from a junction.

6.6.3 The alignment change would introduce a 1-step departure from standards regarding forward visibility on the western side of the bridge, for lane 3 on the east-bound approach to the bridge.

6.6.4 The eastern tower was repositioned slightly closer to the edge of the wetted channel for the River Usk. These changes resulted in a reduction in the main span for the River Usk crossing from 500m to 440m, delivering a cost saving for the bridge. There is no change to SSSI land taken by the scheme for option M5b and the positioning of the bridge in relation to the River Usk SAC is equivalent to the conceptual design.


a) Avoid impact to the River Usk SAC

b) The cost of the scheme – aim to reduce main span of structure

c) Impact upon Newport Docks and Stephenson Street Industrial Estate

d) Buildability of the structure




6.6.6 Appraisal



Benefits Detriments

Weltag

Economy Reduced scheme cost None identified.

Environment Equivalent to the conceptual design

Social None identified Greater impact upon Stephenson Street Industrial Estate – passes through the middle of Marshalls’ business.

Engineering Long term Shorter span on structure. Removal of curvature from main and backspans has significant benefits to the design of the structure

Introduced a 1-step departure on the east-bound approach (western side of the bridge).

Short term Straightening of main and back spans means easier to build



Safe by Design

Long term Maintenance on the main span is reduced due to shorter span.

Introduced a 1-step departure on the east-bound approach (western side of the bridge).

Short term Straightening of main and back spans means easier to build, less complicated construction techniques.

None identified.

Deliverability Cost Significant cost reduction due to reduction of cable stayed main span from 500m to 440m.

None identified.

Risk Reduced risk during construction due to shorter main span.

Marshalls’ business may need to be relocated.

Buildability The same construction method is to be used for the main span

Increased complexity of construction of temporary works during construction of east tower

Programme Easier to construct the bridge, should result in programme savings

Time to potentially relocate Marshall’s business before construction commences.

6.6.7 Design option M5b would deliver cost savings in relation to the River Usk cable stayed bridge by reducing the main span from 500m to 440m. The revised alignment also straightened the main and back spans of the bridge which would have associated benefits in terms of buildability. However, the alternative introduces a 1-step forward visibility departure into the scheme and would have a more significant impact upon the businesses within the Stephenson Street Industrial Estate.

6.6.8 There is no change to SSSI land taken by the scheme for option M5b and the positioning of the bridge in relation to the River Usk SAC is equivalent to the conceptual design. On balance, it is recommended that the alternative design Option M5b is accepted and is incorporated into the scheme.


6.7.1 The conceptual design aligned the proposed mainline carriageway (describing west to east) to pass to the south of the Solutia Industrial Site, then passing to the south of the Meadows Road/Nash Road intersection at Pye Corner on an left hand 1440m radius, before reversing to a shallow right hand radius to pass




to the north of the Whitson Electrical Sub Station. This alignment impacts upon a key Western Power 132kV overhead electrical power line pylon which is located on the southern side of the proposed new motorway at chainage 12+700m. This power line supplies the Severn Tunnel Pumping Station, so is of critical importance and would be expensive to divert with long programme lead in times of two years to implement.

6.7.2 Design Option M6b provides an alternative alignment for the mainline which would realign the horizontal alignment to avoid the Western Power high voltage overhead electrical power line pylon by shifting the alignment north, with a maximum centreline offset of 27m occurring at CH 12560. The impact of this alignment shift is to move the proposed new motorway closer to the business International Automation and Control Systems (IAC). The realignment would directly affect this property, resulting in a loss of an area of car parking, but would not directly impact the building.

6.7.3 The alignment shift would not have any material change to the SSSI land required for the scheme but would have a marginal benefit of moving the alignment further north which is in line with the overall principle of keeping the alignment as far to the northern edge of the SSSI as practical. At CH 12700, the proposed new motorway is not in the SSSI. Both the conceptual design and the proposed new motorway cross the SSSI boundary at Julian’s Reen which is at CH 13070 in the conceptual design.

6.7.4 The key considerations of option M6b are:

a) Aim to reduce the capital cost of the scheme

b) Reduce programme risk due to long lead in times for moving a pylon

c) Impact to power supply to the Severn Tunnel Junction, consideration of impact upon Network Rail.

d) Alignment constraints imposed by National Grid pylon to the north of the M4CaN (east of Tatton Road)

e) Impact upon commercial property of IAC.




6.7.5 Appraisal



Benefits Detriments

Weltag Economy Avoids impact to pylon which carries power to the Severn tunnel pumping station

Direct impact upon IAC property – loss of car parking area

Environment Slight positive effect compared to the conceptual design moving the alignment further north and away from the SSSI.

None identified.

Social Reduced programme delay risk on implementing the scheme.

Direct impact upon IAC property – loss of car parking area

Engineering Long term No change from the conceptual design

Short term Avoids engineering works to divert pylon

Works would be required to IAC’s property

Traffic Long term None identified. Moved mainline further towards the Nash Road/ Meadows Road intersection. Makes side road redesign more complex


Safe by Design


Short term Avoids pylon diversion – less risk during construction

None identified.

Deliverability Cost Significant utility diversion savings as a result of not being required to divert Western Power pylon

Costs of works and compensation to IAC.

Risk Avoids pylon diversion – less risk during construction

Buildability Avoids pylon diversion. More complex side roads works at Nash Road/Meadows Road.

Programme Substantial programme savings associated with not impacting upon Western Power pylon, which would have required diversion.

None identified.

6.7.6 Design Option M6b would deliver significant cost savings in relation to the conceptual design. These would be as a result of no longer being required to divert a Western Power pylon. The alternative would move the mainline closer to a private business, affecting the car parking, but it is considered this is could be mitigated. There is a slight benefit to the SSSI by moving the alignment further north. It is therefore recommended that Design Option M6 is accepted and the alternative design is incorporated into the scheme.




6.8 Side Road Option SR1: Chainage 4+630 Church Lane

6.8.1 Option SR1 relates to the Church Lane side road. The conceptual alignment has Church lane passing under the proposed M4 in an underbridge, whereas the alternative alignment takes Church Lane over the proposed motorway on an overbridge.

6.8.2 This option is closely linked to Option M1 (Section 7.4) which deals with the vertical alignment of the proposed M4 in this location, and as such the appraisal of option SR1b has been undertaken in combination with that for Option M1. As discussed in Section 7.4, clear benefits exist over the conceptual design in favour of the alternative, so it is therefore recommended that design option SR1b is accepted and the scheme progresses with the revised alignment.




6.9 Side Road Option SR2: Chainage 7+400 Lighthouse Road

6.9.1 The conceptual design for the Lighthouse Road side road was based upon utilising the existing road corridor, and looking to align the road largely along its current alignment. The side road would pass over the proposed new motorway on a bridge, where it is on a 1.5m high embankment. The side road bridge would be approximately 8.5m above the surrounding land. The resulting embankment from the approaches would have a significant impact upon the existing property, farm and field accesses, all of which would require realignment to tie them in.

6.9.2 The proposed construction methodology for Lighthouse Road for the conceptual design would involve initially building a temporary alignment away from the existing road to enable traffic to be switched away from the construction works. In addition, the existing utilities along Lighthouse Road would need to be temporarily diverted to the temporary road to enable the new side road to be constructed. Once constructed, the utilities would be switched back into the new verges of Lighthouse Road.

6.9.3 Design option SR2b provides for alternative alignment which would realign Lighthouse road to the west of its current alignment. The residual carriageway from the existing Lighthouse Road would be retained to serve as an access road for an existing farm and buildings to the south of the proposed new motorway, and field access for the land to the north. New junctions would be provided either side of the proposed new motorway to connect the new access road into the diverted Lighthouse Road.

6.9.4 Design option SR2b would greatly simplify the construction works required for this part of the scheme. Building an offline alignment would have the benefits of enabling the existing road to be kept open without the need for a temporary road diversion, and would also avoid the need to divert the utilities twice. There would be less disruption to the residents in the vicinity of the new bridge.

6.9.5 This section of the proposed new motorway and Lighthouse Road is wholly within the Gwent Levels St Brides SSSI. The design option SR2b would take more land from the SSSI than the conceptual design due to the new bridge being built off the line of the existing Lighthouse Road.

6.9.5.1 The key considerations of option SR2 are :


b) Maintain access to local properties and fields and minimise land take and disruption

c) Simplify construction and disruption to residents during construction

d) Increase in land required from the Gwent Levels St Brides SSSI




6.9.5.2 Appraisal

Table 6.6: Option SR2b – Side Road Appraisal Ch 7+800m, Lighthouse Road

Sub-Option Number: SR2b

Benefits Detriments

Weltag Economy Reduced scheme cost None identified.

Environment Reduced impact on residents adjacent to Lighthouse Road.

Greater land take within St Brides SSSI

Social Re-uses existing road for access road Reduces impact (land take and access arrangements) on Fair Orchard Farm

None identified.

Engineering Long term Reduces length of diversion with tie in to existing carriageway to the north instead of into existing bridge over the railway line

Tighter horizontal geometry than with conceptual design, but comparable to existing conditions along Lighthouse Road

Short term Simpler construction sequencing, assuming OH diversion is done in advance, followed by Side Road diversion, followed by M4CaN construction. Reduced skew of structure over M4. Avoids temporary road diversion of Lighthouse Road.

None identified.


Short term Existing road can stay open during construction (reduced Traffic Management)

None identified.

Safe by Design


Short term Reduced TM requirements and interfaces with existing road. More off line working away from live traffic.

None identified.

Deliverability

Cost Cost savings:

• Reduced skew of Lighthouse Road overbridge

• No double handling of utility diversions

• Simpler construction methodology, offline easier to build

None identified.

Risk Less disruption to road users and residents.

More land required from SSSI

Buildability Simpler to construct offline layout compared to online design

None identified.

Programme Reduced programme as a result of simpler construction methodology

None identified.

6.9.6 The alternative design would be a far simpler solution to construct and would reduce the amount of traffic management required to keep the existing road open during construction. In addition, with the alternative design being an offline solution, the diversion of the existing utilities could be done in a single operation.

6.9.7 Option SR2b would take more land from the SSSI to the west of the existing Lighthouse Road, due to the off line construction.




6.9.8 Access to the existing farm, properties and fields could be provided relatively easily compared to the conceptual design, minimising disruption to the local residents. It is considered that the alternative proposal would deliver cost savings and it is therefore recommended that design option SR2b is accepted and is incorporated into the scheme.




6.10 Side Road Option SR3: Chainage 12+250 – Nash Road/Meadows Road

6.10.1 The conceptual design for how the side roads of Nash Road and Meadows Road, provided a diversion for Nash Road to the west of its current alignment, crossing the M4CaN on an overbridge. This route would provide low impact to residential properties and businesses in the area.

6.10.2 However, Nash Road to the north of its intersection with Meadows Road is speed restricted and has been traffic calmed using vertical speed restraint measures (speed humps, etc). It is therefore unsuitable to act as the main through route for traffic and Meadows Road serves this purpose. The existing junction between Meadows Road and Nash Road is currently a T-junction, with Nash Road forming the junction with Meadows Road. The conceptual design was based around this T-junction being amended to make the Nash Road to Meadows Road a straight ahead alignment such that through traffic could undertake this manoeuvre unimpeded. However, this would result in an extremely tight radius on the new side road of approximately 10-15m, which is considered to be a safety concern. In addition, it has been established that this area contains a complex mixture of utility services including a high pressure gas main, intermediate pressure gas main, BT and overhead electricity. Building any new infrastructure in this area would involve numerous utility diversions with associated cost and programme implications.

6.10.3 Design option SR3d has been developed which would provide the side road diversion to the east of the current Meadows Road/Nash Road through route. This would connect Nash Road, to the south of the proposed new motorway, with Meadows Road, to the north. The resulting alignment would be slightly shorter than the conceptual design.

6.10.4 To provide enhanced connectivity between Nash Road and Meadows Road to the north of the proposed new motorway, it is proposed to open a new road link to connect Nash Road with Meadows Road by extending the existing road, Nash Mead, to form a new junction with Nash Road. This would avoid the need to reconfigure the existing Nash Road/Meadows Road junction, which is the area containing numerous utility services.

6.10.5 Whilst the proposed new motorway at this location is not within SSSI land, the southern end of the route of Nash Road for option SR3d would be within the SSSI for a length of 300m whereas the conceptual design route of Nash Road is wholly outside the SSSI. However, the existing Nash Road is also within the SSSI for the southern 125m of the diversion and so the net effect can be considered as an additional 175m of road within the SSSI.

6.10.6 The key considerations of option SR3 are :


b) Minimise impact upon existing utility services

c) Maintain good connectivity between Nash Road and Meadows Road

d) Simplify construction sequencing

e) Land required from the SSSI

6.10.7 Appraisal




Table 6.7: Option SR3d – Side Road Appraisal Ch 12+250m Nash Road/ Meadows Road

Sub-Option Number: SR3d

Benefits Detriments

Weltag Economy Reduced scheme cost. None identified.

Environment None identified. Increased land required from the SSSI.

Social Improved connectivity with existing side road network by linking direct to Meadows Road.

None identified.

Engineering Long term No significant difference from the conceptual design

Short term Reduced impact upon existing utility services

Traffic Long term Improved linkage between Nash Road and Meadows Road

None identified.

Short term Less disruption during construction. None identified.

Safe by Design

Long term In the conceptual design the existing junction of Nash and Meadows Road would be reconfigured into a tight and potentially hazardous bend. This is avoided in option SR3d.

None identified.

Short term Proposed side road amendments at Nash mead allow early separation of traffic from construction activities.

None identified.

Deliverability

Cost Reduced length of route and reduced impact upon utilities

None identified.

Risk Reduced interface with existing utility services.

None identified.

Buildability Reduced impact upon existing utility services, simplify construction

None identified.

Programme Reduced impact upon existing utility services, shorter programme

None identified.

6.10.8 Design Option SR3d would result in a shorter side road diversion and provide a better connection between Nash Road and Meadows Road. Furthermore, it would remove any construction works from an area known to contain a number of utility services. The alternative would result in both cost and programme savings and it is therefore recommended that design option SR3d is accepted and incorporated into the scheme. The alternative requires additional land from the SSSI compared to the conceptual design.




6.11 Side Road Option SR4: Chainage 18+000 – North Row

6.11.1 The North Row conceptual design diverted the side road by approximately 15m to the east of its current alignment, but aligned the road parallel to the existing road. North Row would then pass over the proposed new motorway on a bridge and tie back into the existing North Row. The old side road would be stopped up.

6.11.2 Through discussions with National Grid and Western Power, it has been established that the conceptual design for North Row would impact upon a series of overhead high voltage power lines, resulting a significant cost impact to the scheme.

6.11.3 Design Option SR4c offers an alternative alignment that would realign the side road approximately 350m to the west. The revised alignment would tie into the A4810 at the existing roundabout which provides access to the Tata steelworks. The North Row diverted alignment would pass over the proposed new motorway on a bridge before tying back into the existing North Row. This alignment would avoid any impact upon the overhead high voltage power lines or pylons, thus producing a large cost saving when compared with the conceptual design.

6.11.4 The key considerations of option SR4 are:


b) Minimise impact upon existing utility services

c) Land take from the SSSI




6.11.5 Appraisal

Table 6.8: Option SR4 - Side Road Appraisal Ch 18+000 North Row

Sub-Option Number: SR4c

Benefits Detriments

Weltag Economy Cost savings. None identified.

Environment Avoids requirement for any SSSI land that may be required to implement power line diversions.

Slight increase in land severance. Side road crosses reens and ditches Additional land required from the SSSI for the permanent works.

Social Option SR4c provides equivalent connectivity as the conceptual design.

Engineering Long term None identified. Realignment of North Row is not as straight as the conceptual design.

Short term Avoids power line diversions. Less disruption to A4810 during construction.

None identified.

Traffic Long term Connecting into existing roundabout reduces the number of junctions on the A4810.

None identified.


Safe by Design

Long term Removal of a T-junction from Steelworks Access Road has the potential to reduce accidents

None identified.

Short term Avoids construction works associated with the diversion of overhead power lines and/or pylons

None identified.

Deliverability

Cost Avoids costly diversion of National Grid and Western Power overhead power cables

None identified.

Risk Removes risks associated with diversion of power lines

None identified.

Buildability Avoids diversion of National Grid and Western Power overhead power cables

None identified.

Programme This solution does not require any National Grid or Western Power utility diversions which would have significantly affected programme

None identified.

6.11.6 Design option SR4c would avoid impacts upon National Grid power lines, which would be very expensive to divert, thus the alternative delivers significant cost savings for the scheme. It is therefore recommended that design option 4c is accepted and is incorporated into the scheme. The alternative does require additional land from the SSSI compared to the conceptual design

6.12 Junction Option J1: Chainage 1+500 – 4+400 Castleton Motorway Interchange

6.12.1 The conceptual design for the Castleton Interchange provides free-flow connection for the following links:

a) M4CaN to A48(M) – westbound link

b) M4CaN to existing M4 – westbound link




c) A48(M) to reclassified M4 – eastbound link

d) A48(M) to M4CaN – eastbound link

e) Existing M4 to reclassified M4 – eastbound link

f) Existing M4 to M4CaN – eastbound link

g) Reclassified M4 to Existing M4 – westbound link

h) Reclassified M4 to A48(M) – westbound link

6.12.2 The conceptual design for the interchange would retain the existing M4 mainline approximately on its existing alignment, but would lower the existing motorway levels of the carriageway (eastbound) before crossing over the A48 and down onwards towards Duffryn. Eastbound the existing A48(M) merges with the eastbound diverge slip to form new A48(M) to the north of the motorway corridor, whilst the link to the new M4 crosses the A48(M) to the south of the M4 and over the motorway to merge. Westbound links remain to the south of the motorway corridor.

6.12.3 The links for the conceptual design were designed to minimise the footprint of the scheme, and to minimise the volume of cut to be generated by the scheme from the northern side of the interchange. This has a positive impact upon reducing land take from the New Park and Penylan farms, but would reduce the amount of excavated material available for the scheme elsewhere, where large volumes of fill material are required. However, the resulting interchange links are close together, and surround the existing live motorway. This would mean the method of construction would be complex, with numerous complex traffic management regimes required and this would impose a programme constraint upon the scheme. In addition, the interchange links contained sub-standard horizontal and vertical geometry which constrained the visibility through the junction.

6.12.4 Design option J1b layout for the Castleton Interchange provides the same connections as the conceptual design (see 7.13.1.1), but has an altered geometry. As with the conceptual design, the proposed new motorway mainline would stay approximately on the line of the existing M4, but would be lowered before crossing over the A48 and south-eastwards towards Duffryn. Eastbound links would be located to the north of the proposed motorway corridor with the A48(M) merging with the eastbound diverge slip to form new A48(M), whilst the westbound links remain to the south.

6.12.5 The key benefits of the alternative design would include;

a) Providing a DMRB compliant horizontal and vertical geometry, providing

desirable visibility through the junction

b) Fewer bridges to construct compared to the conceptual design

c) Maintain three running lanes in both directions during construction

d) Avoid impacting upon the high pressure gas main to the east of the

interchange

6.12.6 The key considerations of option J1 are:

a) Aim to improve the buildability, reduce traffic disruption and reduce the

capital cost of the scheme

b) Impact upon the existing high pressure gas main

c) Land take for the scheme




d) Impact upon properties

e) The number of structures




6.12.7 Appraisal

Table 6.9: Option J1 – Junction/Interchange Appraisal Ch 1+500 – 4+400m Castleton Interchange

Sub-Option Number: J1b

Benefits Detriments

Weltag Economy Reduced scheme costs. None identified.

Environment Reduced impact to south of A48 compared to conceptual design

Wider overall footprint and greater cut to the north of the M4 corridor. Loss of farm land

Social Overall smaller footprint of motorway junction.

The M4 eastbound diverge slip road cutting slope impacts upon New Park Farm for 150m on the southern extents of the property Both options would require the loss of properties to the south of the M4 corridor, however, the alternative design would additionally take Berry Hill Cottage

Engineering Long term Reduced maintenance with fewer structures.

None identified.

Short term The M4 eastbound diverge and westbound merge slip road contain 2 lanes plus hard shoulder and hard strip which would enable 3 running lanes to be provided during construction. The footprint of the alternative provides more opportunity for simpler traffic management.

Greater land take to the north and greater earthworks excavations.

Traffic Long term Priority given to M4 through interchange with 3 continuous lanes provided to the mainline in both directions, which would avoid unnecessary weaving manoeuvres and lane changes. Ghost island layouts are provided to the east bound diverge and west bound merge which satisfy design year traffic flows for the interchange links. Compliant geometry and visibility through interchange links and slips, whereas visibility in conceptual design was constrained by and bends in alignment/ major structures.

Number of mainline lanes provided is an over-provision as a lane drop/gain could be applied in each direction.

Short term The footprint of the alternative provides more opportunity for simpler traffic management.

None identified.

Safe by Design

Long term 4 major structures to maintain, which is two fewer than the conceptual design.

The alternative design contains extensive cutting slopes, up to 70m wide which would need to be maintained.

Short term 4 major structures to construct, which is two fewer than the conceptual design.

None identified.





Benefits Detriments

A structure spanning the HP gas main has been designed to avoid the foundations of the Interchange bridges affecting the pipe, and also enables access for maintenance. The conceptual design required excavation and diversion of the gas main.

Deliverability

Cost Significantly cheaper than conceptual design as there are fewer large structures to construct and less volume of fill to south of A48

Additional earthworks to cut on north side of junction

Risk Overall lower risk than the conceptual design for the several reasons presented in this table.

Some additional risks, as identified in this table, but over the benefits outweigh increases.

Buildability Fewer bridges to construct than concept design. Closer balance of cut and fill to north and south of M4. The layout can be constructed whilst minimising disruption to the existing M4 and A48M traffic, whilst the Conceptual Design would have been difficult to construct without extensive diversions.

Additional cut to north of M4 corridor which will need to be taken across the M4 corridor for deposition

Programme The construction programme for the Conceptual design was on the critical path due to the complexity of the structures. The alternative design programme was shorter due to its simpler construction and phasing.

None identified.

6.12.8 Design option J1b would result in a simpler layout which would be easier to understand by the motorists, and would also enable 3 lanes to be provided in each direction during the construction phases of the works. A significant cost saving would be achieved by reducing the structural works, the construction programme as well as potential impacts on the utilities. There is no change to the amount of land taken from the SSSI with design option J1b. It is therefore recommended that the design Option J1b is accepted and is incorporated into the scheme.




6.13 Junction Option J2: Chainage 7+800 – 9+800 Docks Way Motorway Junction

6.13.1 This conceptual design for the Docks Way Junction involves providing a grade-separated roundabout junction on the proposed new motorway at the south east corner of the Docks Way landfill site. A new dual 2-lane all-purpose carriageway link road would also be provided to connect the new junction with the A48 Newport Southern Distributor Road (SDR). The link road would skirt along the eastern edge of the landfill site and connect with the SDR via a new roundabout. The positioning of the new motorway junction and the link road was such as to sit adjacent to the landfill site, without impacting upon the site.

6.13.2 The location of the proposed conceptual motorway junction would mean the east-facing slip roads would impact upon the back spans of the River Usk cable-stayed structure, complicating its design and construction, and having a consequential impact on construction cost.

6.13.3 Design option J2d for the Docks Way Junction was developed which repositioned the grade-separated roundabout approximately 250m to the east of the conceptual design location. A new dual carriageway link would connect to the Docks Way junction, running parallel with the motorway (eastbound) for a distance of 250m to connect into a new at-grade roundabout. The new dual carriageway link road would then turn 90 degrees to then connect with the SDR, utilising the same alignment as for the conceptual design.

6.13.4 The slip road connections from the Docks Way junction onto the proposed new motorway would have a different configuration to the conceptual design. The east bound merge slip road would connect from the new at-grade roundabout along the new dual carriageway link road (connecting the M4CaN with the SDR) to the motorway, whereas all other three slip roads would connect from the motorway to the Docks Way junction grade-separated roundabout. In order to maintain the benefits of a shorter, straighter River Usk crossing, to tie the east bound merge slip road into the new dual carriageway link road, the proposed at-grade roundabout would be raised in elevation to approximately 7m above the surrounding ground level.

6.13.5 The alternative design has the following key features:

a) Avoids the need to take the new dual carriageway link road under the

motorway – deletes one structure from the project

b) Impact upon Newport Dock land or building to the south of the motorway

c) Enables the mainline alignment to be straightened over the main River

Usk crossing

d) The west facing slip roads associated with the Docks Way junction would be shifted 250m east. This means the vertical alignment of these slip roads could no longer be tied in at the western abutment of the River Ebbw crossing and results in the need to provide three separate decks over the River Ebbw bridge; one for the mainline and one for each slip road. This slightly increases the footprint west of the River Ebbw and hence the land required from the SSSI.

6.13.6 The key considerations of option J2d are:


b) Reduce impact upon Newport Docks land

c) Reduce impact upon properties within Newport Docks

d) Reduce the number of structures




e) Simplify construction methodology for the main River Usk crossing

6.13.7 Appraisal

Table 6.10: Option J2 – Junction/Interchange Appraisal Ch 7+800 – 9+800m Docks Way Junction

Sub-Option Number: J2d

Benefits Detriments

Weltag Economy Reduced impact on Newport Docks land. Reduced scheme cost.

None identified.

Environment None identified. Increase in land required from the SSSI on the west bank of the River Ebbw. Visual impact considered more significant

Social Equivalent to the conceptual design in respect of impact on the Newport Docks.

Engineering Long term Removal of one underbridge – simplified maintenance.

None identified.

Short term Removal of one underbridge – simplified construction.

Greater earthworks movements.

Traffic Long term None identified. Additional roundabout on link road will slow traffic flow, compared to conceptual design

Short term Not applicable – off line construction.

Safe by Design

Long term One underbridge deleted - reduced maintenance requirements

Road gradients increased on approach to at-grade roundabout (although compliant with DMRB). Additional roundabout junction added to the scheme – junctions are biggest accident locations. Two new two new slip road bridges over the River Ebbw, increased maintenance.

Short term Reduced working at height None identified.

Deliverability

Cost Cost savings associated with removal of one dual carriageway underbridge.

Additional costs associated with two new slip road bridges over the River Ebbw

Risk Reduced construction risk. Benefits outweigh the detriments.

Buildability Removal of one underbridge – buildability savings

Additional fill requirements to elevate the now at-grade link road roundabout. Two new two new slip road bridges over the River Ebbw, increased buildability difficulty.

Programme Removal of one underbridge – programme savings

Two new two new slip road bridges over the River Ebbw, programme increases.

6.13.8 The alternative design would result in the removal of one dual carriageway underbridge from under the proposed new motorway, but the inclusion of two slip road bridges over the River Ebbw.




6.13.9 Design option J2d would reduce the impact upon Newport Dock’s land and property and utilise an area of waste land for the construction of a new link road (to the south of the Docks Way landfill site). The option increases the land from the SSSI on the west bank of the River Ebbw. It would result in cost savings, and it is recommended that design option J2d is accepted and is incorporated into the scheme.




6.14 Junction Option J3: Chainage 14+000 – 15+200 Glan Llyn Motorway Junction

6.14.1 The conceptual design for the Glan Llyn junction provided a grade separated roundabout junction immediately to the east of Monks Ditch. A new dual carriageway link road was provided to connect the new motorway junction with the A4810, by forming a fourth arm onto the existing A4810 roundabout.

6.14.2 The position of the conceptual design motorway junction resulted in the east-facing slip roads both passing through an area of known contaminated land associated with the Tata Steelworks Lagoons. This contaminated material was proposed to be excavated, treated and/or stabilised and reused as fill material within the construction works. However, the treatment of this contaminated land is an expensive operation and would result in significant costs to the scheme.

6.14.3 In addition, there are two sets of National Grid overhead power cables crossing the proposed new motorway to the east of Monks Ditch. There would be insufficient headroom beneath the cables and the east facing slips, resulting in significant diversion costs.

6.14.4 Option J3b provides an alternative junction location which relocated approximately 400m to the west of the conceptual design. The junction would link to the A4810, as with the conceptual design, by forming a fourth arm onto the existing A4810 roundabout. However, the link road would now cross Monks Ditch, requiring an additional structure.

6.14.5 This shift of junction location had the effect of reducing the impact the east-facing slip roads would have on the contaminated land, reducing the amount of contaminated land to be excavated with the scheme.

6.14.6 In addition, moving the motorway junction to the west, and slightly realigning the proposed new motorway to the south, it was possible to design the longitudinal profile of the east facing slip roads to satisfactorily pass under the existing overhead power lines, thus avoiding expensive diversion costs. Although Option J3b requires more land from the SSSI than the conceptual design the lengths of reen and ditch affected locally would be very similar in extent.

6.14.7 The key considerations for option J3 are:


b) Minimise impact upon the existing overhead power lines

c) Minimise volume of contaminated land to be excavated and treated

d) Avoid increasing land take from the SSSI




6.14.8 Appraisal

Table 6.11: Option J3 – Junction/Interchange Appraisal Ch 14+200 – 15+900m Glan Llyn Junction


Benefits Detriments

Weltag Economy Reduced scheme cost. None identified

Environment Reduced impact on Tata Steelworks Lagoons. Reduced excavation of contaminated material.

More land required from SSSI, although lengths of reen and ditch affected very similar

Social None identified.

Slight impact on existing Lafarge/ Tarmac batching plant

Engineering Long term None identified. One additional culvert required (Monks Ditch) – maintenance requirements

Short term Avoids overhead power line diversions and/ or special measures around pylon bases. Reduced excavation of contaminated material.

One additional culvert required (Monks Ditch) – construction requirements

Traffic Long term Equivalent to the conceptual design.

Short term Equivalent to the conceptual design.

Safe by Design

Long term Moving the junction away from the overhead power lines will decrease the risk of striking the power lines during maintenance.

None identified.

Short term Moving the junction away from the overhead power lines will decrease the risk of striking the power lines during construction. Moving the junction away from the Tata Steel lagoons will reduce exposure to contaminated materials during construction.

None identified.

Deliverability

Cost Large cost saving as diversions of OH cables not required. Reduced volume of contaminated material to be excavated and treated.

One additional large culvert (Monk’s Ditch).

Risk Overall reduced construction risks for diversions of cables and contamination excavations.

Buildability Reduced working with contaminated material

Additional culvert structure




6.14.9 Design option J3b proposals would result in moving the position of the proposed motorway junction away from contaminated material, reducing the impact of the scheme on this material. It would avoid the need to divert National Grid overhead power lines, resulting in a significant cost saving for the scheme. The option does require additional land from the SSSI. It is nevertheless recommended that design option J3b is accepted and incorporated into the scheme.




6.15 Structures Option S1: Chainage 8+400 - 8+600 – River Ebbw Structure

6.15.1 The conceptual design for the proposed new motorway mainline incorporated a bridge crossing of the River Ebbw which had a total length of 190m. This total length crossed over the River Ebbw, its western flood defence bund, an access track, and Sea Wall Reen. The access track along the top of the bund provides maintenance access for Natural Resources Wales (NRW). The conceptual design included plans to divert the Wales Coast Path under the new River Ebbw Underbridge along the NRW access track.

6.15.2 Design option S1c proposes shortening the River Ebbw structure by 21m, to a reduced total length of 169m. This would be achieved by repositioning the west abutment closer to the River Ebbw to be in line with the western flood defence bund. The Sea Wall Reen would be diverted into a separate culvert structure to the west of the River Ebbw Underbridge and a new bridge (New Dairy Farm Overbridge) would be provided approximately 400m to the west of the River Ebbw Underbridge. The new bridge would carry the existing side road, Heol Pont-y-Cwcw and the Wales Coast Path over the proposed new motorway, which would minimise the diversion of the Wales Coast Path from its existing course on Heol Pont-y-Cwcw. It is proposed that NRW gain access to the River Ebbw western flood defences from Heol Pont-y-Cwcw, with New Dairy Farm bridge used to provide access between the bund sections located north and south of the motorway. New rights of access would be required to connect the existing NRW access track to Heol Pont-y-Cwcw due to the severance of the existing track by the new location of the west abutment.

6.15.3 The key considerations for option S1 are:

a) Minimising the size of the River Ebbw Underbridge structure

b) Managing flood risk during construction of the west abutment

c) Minimising impact on SSSI land (to the west of the River Ebbw)

d) Maintaining access to the flooding bunds for Natural Resources Wales

e) Retaining the Wales Coast Path close to its existing course on Heol

Pont-y-Cwcw.




6.15.4 Appraisal

Table 6.12: Option S1 – Structural Appraisal Ch 8+400 – 8+600m River Ebbw

Structure

Sub-Option Number: S1c

Benefits Detriments

Weltag Economy Reduced bridge length is more economical. Reduced land required for diversion of the Wales Coast Path and private means of access.

None identified.

Environment Smaller structure, reduced structural material usage.

Additional land required from SSSI in order construct embankments for approaches the New Dairy Farm access bridge.

Social Reduced diversions for Wales Coast Path and for New Dairy Farm.

Increased diversion for NRW to inspect and maintain the length of the flooding bund.

Engineering Long term Reduced maintenance associated with a smaller structure.

Additional maintenance of the New Dairy Farm access bridge.

Short term Reduced design and construction programme from reducing size of structure.

Interface of west abutment and flood defence bund requires additional consideration. Additional construction of the New Dairy Farm access bridge.

Traffic Long term More direct route for NMUs using Wales Coast path. More direct access for New Dairy Farm.

NRW may not be satisfied with access to flood defence bund from southern and northern approaches – consultation required.


Safe by Design

Long term Reduced maintenance associated with a smaller structure. Requires less work at height over water.

West abutment now forms part of flood defence and will need appropriate maintenance. Additional maintenance of the New Dairy Farm access bridge.

Short term Reduced structure size reduces the number and size of girders. Reduced material handling.

Flood risk when west abutment constructed – flood defence must not be compromised during construction. Additional construction of the New Dairy Farm access bridge.

Deliverability

Cost Cheaper solution.

Risk Reduced construction risk associated with a smaller structure.

NRW may not be satisfied with access to flood defence bund from southern and northern approaches – consultation required. Additional construction of the New Dairy Farm access bridge.

Buildability Improved buildability through reduction of number and size of girders. Less reinforcement to fix and concrete to pour.

Interface of west abutment and flood defence bund requires additional consideration. Additional




Sub-Option Number: S1c

Benefits Detriments

construction of the New Dairy Farm access bridge.

6.15.5 Design option S1c would deliver cost savings in relation to the River Ebbw structure and would have associated benefits in terms of buildability and minimising environmental impact. The addition of the New Dairy Farm bridge would provide more direct access to New Dairy Farm and would avoid a permanent diversion of the Wales Coast Path. Additional land would be required from SSSI in order construct embankments for approaches the New Dairy Farm access bridge. Consultation would be required with NRW to confirm their acceptance of the proposal to divert their access via New Dairy Farm Overbridge. Subject to future NRW consultations, it is recommended that design option S1c is accepted and incorporated in to the scheme.




6.16 Geotechnical Option G1: Chainage 5+100 to 19+200 – Embankments on Gwent Levels

6.16.1 Along the Gwent Levels there would be approximately 11km of low rise embankment (typically 1.5m to 2.5m high), of which approximately 8.8km would be sitting on land designated as Site of Special Scientific Interest (SSSI). The conceptual design for all embankments throughout scheme is a 1 vertical to 2 horizontal side slope (1:2).

6.16.2 Design option G1b has been developed to consider means of reducing the land required from the SSSI by considering steeper side slopes of 1:1.5, which would reduce the footprint of the embankments.

6.16.3 The key considerations for design option G1 are:

a) Land required from the SSSI

b) Earthworks stability within the embankment.

c) Embankment foundation stability in underlying ground due to greater

concentrated load.

d) Construction complexity

e) Costs and programme implications.




6.16.4 Appraisal

Table 6.13: Option G1: Chainage 5+100 to 19+200 – Embankments on Gwent Levels

Sub-Option Number: G1b

Benefits Detriments

Weltag Economy None identified. Increased construction and maintenance costs.

Environment Reduces the land required from the SSSI.

From a visual perspective slopes of 1:1.5 will have more of a causeway appearance.

Social Equivalent to the conceptual design

Engineering Long term None identified. Increased basal reinforcement and select fill required in order to mitigate stability issues.

Short term None identified. Specially selected granular fill would be required on the shoulders of the embankments to form the 1:1.5 slopes.

Traffic Long term Equivalent to the conceptual design

Short term Equivalent to the conceptual design

Safe by Design

Long term None identified. Steeper side slopes result in greater risk of falls and plant instability during maintenance.

Short term None identified. Steeper side slopes result in greater risk of falls and plant instability during construction.

Deliverability

Cost Reduction in land purchase costs. Increase in cost due for geogrid, imported fill, construction complexity and programme duration.

Risk None identified. Higher potential for earthworks failures

Buildability Reduces the volume of import fill required

More complex and will take longer to build.

6.16.5 Steepening up the side slopes to 1:1.5 would increase the complexity of the construction, and require slope stabilisation techniques, resulting in programme and cost increases. Based on the increased risks and associated costs for option G1b, it is recommended to reject the alternative option.

6.17 Drainage Option D1: Chainage 9+000 – 11+200 – River Usk Bridge Drainage

6.17.1 The conceptual design for dealing with surface water over the River Usk bridge was based on the principle of outfalling into the Newport docks and the River Usk. It involved the collection of the highway surface water via a system of combined kerb drainage and carrier pipes beneath the central reserve of the bridge deck. This system would convey the water from the high point of the River Usk crossing in a westerly and easterly direction. On the west, this drainage would outfalls into Newport docks. On the east, the drainage outfalls to a dock, which could potentially be dry, and would then discharge into the River Usk, with treatment being via a petrol interceptor.

6.17.2 Design option D1c has been developed an alternative solution which involves the discharge of the highway surface water between the high point of the River




Usk crossing and chainage 11+120 via a pollution treatment lagoon and water treatment area to the River Usk via a purpose built ditch. On the west side of the River Usk bridge, the highway surface water would be discharged to the River Ebbw via a petrol interceptor. There is no change to SSSI land required for the scheme with this option D1.

6.17.3 The key considerations for option D1 are:

a) Drainage discharge interfaces with third parties

b) Impact on Newport Docks

c) Water quality and treatment of water prior to discharge in to water courses




6.17.4 Appraisal

Table 6.14: Option D1 - Drainage Appraisal Ch 8+600 – 11+200m River Usk Crossing

Sub-Option Number: D1c

Benefits Detriments

Weltag Economy Equivalent to the conceptual design

Environment Reduces contamination risk from outfalling water in dock which could potentially be dry.

Outfalling into the River Usk SAC requires a high level of control of water quality. The risks of pollution would be mitigated through the provision of pollution control and flood storage lagoon, and discharge into ditch.

Social No requirement to outfall in to Newport docks.

None identified.

Engineering Long term Pipe does not have to cross ABP land, which has significant amount of existing utilities.

Land required for pollution control and flood storage lagoon on the eastern bank of the River Usk

Short term New WTA could be used during construction for temporary drainage, minimising land take

None identified.



Safe by Design

Long term Maintenance of east outfall into dock requires operative to work adjacent to water’s edge and at height. Revised proposal of outfall to ditch mitigates this risk.

Movement joint in pipe between deck and pier requires maintenance at height.

Short term Similar to long term in respect of construction stage risks.

Similar to long term in respect of construction stage risks.

Deliverability

Cost None identified. Increased land and construction for lagoon.

Risk No risk of dock owners refusing license to discharge. More acceptable water quality design for NRW, reducing risk of rejection.

Indirect outfall into SAC has risk associated with approvals

Buildability Similar to points noted for Safe by Design.

Similar to points noted for Safe by Design.

6.17.5 Design option D1c improves the water treatment facilities for drainage in to the River Usk SAC and removes the need to use third party infrastructure as a discharge location. There is no change to the land required for the scheme from the SSSI. It is therefore considered that, with sufficient measures to treat the highway runoff, the design option D1c for dealing with surface water runoff from the River Usk bridge should be accepted and incorporated in to the scheme.

6.18 Drainage Option D8: Chainage 20+300 – 22+000 Water Treatment Area 11

6.18.1 The conceptual design for drainage in this region involves routing surface water runoff from the new and existing M4 carriageways from a high point adjacent to the Knollbury Lane overbridge in a westerly direction towards Junction 23A and then along the new M4 in a south westerly direction to a Water Treatment Area (WTA) located immediately to the south of the South Wales Mainline railway. The surface water runoff would be collected via a




system of concrete channels, catch pits and carrier pipes. Due to carriageway alignments the carrier pipes would need to be in excess of 10m deep to achieve a discharge to the proposed WTA 11. WTA 11, in the conceptual design, is in the SSSI land.

6.18.2 A major risk associated with the conceptual design relates to the need for the drainage to discharge into WTA 11, which is located south of the South Wales Mainline railway. As such, a new 1.5m diameter pipe would be required to be installed beneath the live railway to provide an outfall to this WTA. The ground conditions in this vicinity are considered variable, as the location is at the interface between the Gwent Levels (very poor ground) and the rock associated with the Magor area. Construction of this pipe is considered a risky operation in terms of both physical construction to minimise impact to the live railway, but also is a potential programme constraint.

6.18.3 Design option 8d has been developed which involves raising the alignment of the B4245 (Newport Road), allowing the majority of the M4 between Ch20+400 and 21+000 to drain in an easterly direction into the catchment of the St Brides Brook/Mill Reen. The amended alignment of the road to the west of Ch20+400 would allow runoff to flow over the rail link thus avoiding the need to lay large diameter pipes below the main railway line. The WTA 11 in the conceptual design would no longer be required as flow could be conveyed along the line of the new motorway south into the catchment area for WTA 10. The locations proposed for WTAs for design option D8d are outside the SSSI land.

6.18.4 The area between the existing Junction 23A and the new M4, adjacent to the proposed low spot in the highway would be utilised to accommodate a WTA. Outflows from this WTA would discharge to reed beds located either side of St Brides Road, which would ultimately discharge to Mill Reen to the east.

6.18.5 To prevent the requirement for pipes to be constructed through the bridge structure at St. Brides Road in order to transfer flow from the east of St. Brides Road, a third pond located to the north east of St. Brides Road would be constructed.

6.18.6 The key considerations for design option D8 are:

a) Constructing a new 1.5m diameter pipe under the South Wales Railway Mainline is a high risk construction operation

b) Potential programme impacts associated with Network Rail interface

c) Deep drainage installation

d) High cost associated with the above

e) Land required for the scheme from the SSSI




6.18.7 Appraisal

Table 6.15: Option D8 – Drainage Appraisal Ch 21+000m Water Treatment Area 11

Sub-Option Number: D8d

Benefits Detriments

Weltag Economy Reduction in scheme cost None identified

Environment The proposed pond locations are outside the SSSI.

Proposed WTA to the north of the M4, adjacent to St Bridge Road, is difficult to landscape

Social Equivalent to the conceptual design.

Engineering Long term Avoids the maintenance of a 1.5m diameter pipe under a live railway embankment.

Short term Avoids the need for a new pipe under railway embankment which would be extremely difficult to build, and be difficult to achieve the necessary approvals. Avoids the risk to construction programme.

Traffic Long term Equivalent to the conceptual design.


Safe by Design

Long term Avoids the need for deep drainage excavations, which would make maintenance difficult

Two separate locations for maintenance.

Short term Avoids the need for tunnelling under the railway

None identified

Deliverability

Cost Less expensive than pipe crossing under railway line

None identified

Risk Avoids the need for tunnelling under the railway; eliminates risk of programme and approvals.

None identified

Buildability Deep drainage and crossing of railway line avoided

None identified

6.18.8 Design option 8d would remove the problems associated with deep excavation for the longitudinal drainage runs, and remove the high programme and cost risks associated with installing a new 1.5m diameter pipe under the live railway. The option moves water treatment area 11 entirely out of the SSSI. It is therefore recommended that the design option 8d is accepted an incorporated in to the scheme.




6.19 Drainage Option D9: Chainage 4+300 – 20+000 Reen Mitigation Strategy

6.19.1 The conceptual design for reen mitigation across the Gwent Levels was to provide reens along on both sides of the proposed new motorway to mitigate lengths of reen which are filled as they cross the mainline. These replacement reens would connect to existing reens. The length of reen that would be filled in is 2,755m, and the replacement length is 7,600m.

6.19.2 NRW have expressed concern regarding the ongoing maintenance requirements for this increased length of reens, and requested a rationalisation. They requested that the reen connectivity is provided on one side of the mainline.

6.19.3 Design option D9b provides a combination of reens and smaller field ditches that reflects the existing historic landscape. The solution has compensatory reens along the north side of the highway to allow conveyance of rainfall flows in a flooding event, but smaller field ditches to the south of the mainline. Where existing ditches run adjacent to the proposed embankment, the new field ditches are omitted. The revised length of compensatory reen is approximately 2,826m.

6.19.4 The key considerations for option D9 are:

a) Providing adequate reen connectivity across the levels

b) Minimising scheme footprint

c) Land required from the SSSI

d) Reducing scheme cost

e) Gaining NRW approval




6.19.5 Appraisal

Table 6.16: Option D9 – Drainage Appraisal Ch 4+300 – 20+000 Reen Mitigation

Sub-Option Number: D9b

Benefits Detriments

Weltag Economy Rationalisation of compensatory reens reduces cost of scheme

None identified.

Environment Long length of additional compensatory reens added to the scheme to provide additional habitat. Reduction of reens reduces the land take from the SSSI for ditches, although the overall effect on land required is not significant.

None identified.


Engineering Long term Reduced lengths of compensatory reens (2500m) means that future maintenance liability on NRW is reduced

None identified.




Safe by Design

Long term Reduced lengths of compensatory reens (2500m) means that future maintenance liability on NRW is reduced

None identified.

Short term None identified.

Deliverability

Cost Cost is reduced due to reduction in the number and length of replacement reens.

None identified.

Risk NRW’s preference. Flood Consequences Appraisal still needs to be undertaken. This could potentially change the length and locations of reens required

Buildability Reen construction is challenging – they are steep sided which can cause stability issues. Reduction in the length required is beneficial

None identified.




6.19.7 Design option D9b proposes an alternative reen mitigation strategy which has been requested by NRW. The option has benefits in terms of cost and risk and the amount of land required from the SSSI for reen construction. It is recommended that design option 9b is accepted and is incorporated in to the scheme.




6.20 Drainage Option D10: Edge of highway drainage channel options

6.20.1 Across the Gwent Levels, the proposed M4 mainline vertical alignment is very flat. Surface water drainage for the motorway would be achieved using open channels adjacent to the hard shoulders of each carriageway. The open channels would be virtually flat and act as initial runoff storage, but would pass through water treatment areas (WTA) located along the Levels, located at low points along the mainline. From the WTAs, the surface water would outfall into the reens in the Levels. The Levels are SSSI designated, therefore thorough treatment of the highway runoff before entry into the reen system is very important.

6.20.2 The conceptual design proposed a grass lining for the impermeable channels either side of the motorway. The requirements for a grassed channel are set out in HA119/06. The grass within the channels would provide an initial pollution treatment to the surface water before it entered the WTA, and would also act to slightly reduce the velocity of surface water, reducing entry rates into the WTAs. The grass lined channel would have to be cut three times a year to achieve the recommended length in the DMRB.

6.20.3 Design option D10c provides an alternative solution which replaced the grass lined impermeable channel with a rockfill channel. This solution would not require grass to be cut, reducing the maintenance cost. It would also trap sediments in the rockfill layer, giving an element of water quality improvement. This detail would require a departure from standards.

6.20.4 It is noted that both options of channel treatment would need regular maintenance in pollution spillage events, but the rockfill channel would require less regular maintenance compared with the grass lined channel (grass cutting, etc).

6.20.5 Issues:

a) Minimise project cost

b) Protect the environmental integrity of the Levels SSSI (water quality)

c) The level of maintenance required

d) Mitigate visual impact of channel




6.20.6 Appraisal

Table 6.17: Option D10 - Drainage Appraisal Ch 4+300 – 20+000m Edge of Carriageway Drainage Detail

Sub-Option Number: D10c

Benefits Detriments

Weltag Economy Provides a less maintenance intensive solution, reduced costs

None identified

Environment None identified Reduction of pollution treatment compared to grass.


Engineering Long term No precedent for rockfill channel in highway drainage




Safe by Design

Long term Less maintenance required than conceptual design

Risk of stone scatter


Deliverability

Cost Equivalent to the conceptual design

Risk None identified May not be plausible due to lack of precedent

Buildability Installation of rockfill is more simple than planting of topsoil with vegetation

None identified

6.20.7 Even though the conceptual design proposal of grass lined channels would incur additional maintenance requirements (grass cutting, etc), the alternative proposal for rockfill channels along the motorway for the open channels does not provide the environmental benefits of the grass-lined option. There is little difference in the capital cost. It is therefore recommended that the original conceptual design should be taken forward for the scheme and the alternative option rejected.




6.21 Highway Boundary Treatment Option H1: Chainage 5+100 to 19+200 – Embankments on Gwent Levels

6.21.1 The highway boundary fence line has been typically shown at a 3.0m offset from the toe of the embankment or cut off ditch on highway schemes. This is not a DRMB requirement but generally considered standard practice for highway schemes in order to provide a safe access and working area for maintenance purposes.

6.21.2 Design option H1b provides an alternative solution which provides the highway boundary fence closer to the toe of the embankment in order to reduce land taken from the SSSI. Refer to File Note ‘Review of fence line location along Gwent Levels’ contained within Appendix C for full details on the appraisal leading to the alternative solution which was adopted for the scheme. No appraisal summary table is provided in this part of the report because the file note explains the appraisal. Design option H1b is recommended to be accepted and incorporated in to the scheme.

6.22 Non-Motorised Users Option N1: Chainage 5+700 – 6+100 – Green Lane/Percoed Lane

6.22.1 In the vicinity of Green Lane, the conceptual design alignment would rise up on embankment to pass over the South Wales to London Mainline railway. However, a National Grid high voltage overhead electricity pylon line passes over the proposed motorway in this location, which has required the new motorway embankment to be lowered. The conceptual design envisaged that Green Lane would be diverted to the west of its current alignment and pass beneath the proposed M4 via a new underpass.

6.22.2 For the conceptual design, the Newport-Cardiff Cycle route, running along Percoed Lane, would be connected into Green Lane, and users diverted from the current alignment along Percoed Lane, and use the new underpass for Green Lane, before being diverted back along the toe of the highway embankment to return to the alignment of Percoed Lane.

6.22.3 Design options for N1 present an alternative arrangement with Percoed Lane being diverted over the M4 mainline on an overbridge to the east of its current alignment. Green Lane would then be connected into Percoed Lane and have shared use of the new overbridge. This arrangement would provide NMU-only access across the M4..

6.22.4 The key considerations for design option N1 are:


b) The capital cost of the scheme

c) The diversion of NMUs from the desire line running along Percoed Lane

d) Vertical clearance to high voltage overhead power cables, avoiding expensive diversion costs.




6.22.5 Appraisal

Table 6.18: Option N1 – NMU Appraisal Ch 5+700 – 6+100 Green Lane/ Percoed Lane

Sub-Option Number: N1h

Benefits Detriments

Weltag Economy Design option is linked to savings for avoidance of overhead electricity diversions.

A bridge over the motorway would cost more than an underpass.

Environment A bridge would not require lighting to be provided during daylight hours, reducing the energy consumption; an underpass would require lighting.

A bridge above the M4 motorway embankment would have a visual impact on the landscape.

Social Reduced diversion of the Newport-Cardiff Cycle route would mean that the route would remain attractive for users. The use of a bridge would improve users’ sensation of personal security compared to an underpass, where fears of violence or crime may have impacted users’ choice to use the route.

None identified.

Engineering Long term Providing a bridge means the vertical alignment of the M4 can be lowered, reducing land take, and quantity of earthworks being deposited. Avoids impact on high voltage overhead power cables.

None identified.


Traffic Long term None identified. Direct PMA access across the M4 is not available; indirect access to severed land to the north of the railway


Safe by Design

Long term None identified. Additional maintenance requirements associated with a footbridge compared to an underpass.

Short term None identified. Working at height is increased.

Deliverability Cost Overall, with the avoidance of diverting o/head cables and reducing the height of the embankment, the proposal is likely to deliver reduced costs.

Risk Overall reduced risk through avoiding overhead electricity diversions.

Buildability Overall, with the avoidance of diverting o/head cables and reducing the height of the embankment, the proposal is less complex to build.

6.22.6 The alternative proposal for Green Lane/ Percoed Lane would deliver benefits for users of the Newport to Cardiff Cycle route, delivering a substantial reduction in the length of diversion from the existing corridor compared to the conceptual design. The offline route proposal allows the construction to be completed with minimal impact to current users of the route, and would allow the route to be maintained during construction. Both options are within the SSSI and there is no material difference in the amount of land taken from the SSSI for these options. These benefits outweigh the potential negative impacts that may be associated with the proposal, and it is therefore




recommended that design option N1h is accepted and the scheme progresses with the alternative proposed.




6.23 Non-Motorised Users Option N2: Chainage 8+400 – Wales Coast Path

6.23.1 The conceptual design envisaged that the Wales Coast Path and the private means of access (PMA) along Heol Pont-y-Cwcw would be diverted alongside the toe of the embankment of the proposed M4, to the east, and pass beneath the proposed River Ebbw structure which would carry the new motorway over the river, before returning westwards alongside the toe of embankment to its original alignment.

6.23.2 Design option N2c offers an alternative arrangement which would provide for the Wales Coast Path and PMA route to cross the M4 using an overbridge provided along the current alignment of Heol Pont-y-Cwcw, the existing NMU and PMA route over the proposed New Dairy Farm Overbridge.

6.23.3 This design option is inter linked with design option S1 and the appraisal in section 6.15 applies. It is recommended that option N2c is accepted and incorporated in to the scheme.




6.24 Non-Motorised Users Option N3: Chainage 20+220 – Green Moor Lane

6.24.1 Green Moor Lane provides access to land and allotments on the eastern side of the A4810, adjacent to Magor. The conceptual design envisaged that Green Moor Lane would be diverted south to cross the proposed M4 underneath the proposed Llandevenny railway bridge. This would require the proposed railway bridge to be designed for a wider span to accommodate Green Moor Lane running parallel to the railway under the bridge.

6.24.2 Vehicular access along Green Moor Lane is currently subject to a headroom restriction with the existing lane passing under the A4810, the associated underbridge has a restricted headroom. Vehicular access restrictions would therefore remain as existing.

6.24.3 Design option N3d proposes an alternative arrangement whereby the conceptual design proposal would be provided, but be reduced in scale to accommodate only non-motorised users. This would then be supplemented by a new vehicular access to the land and allotments on the eastern side of the Steelworks Access Road from Blenheim Close in Magor. This option is associated with providing exchange land for allotments to the south side of Green Moor Lane, close to the retained portion of the existing allotments. This exchange land replaces the north section of the existing allotments which would be lost beneath the footprint of the proposed new motorway. The allotments and all access route options are outside the SSSI land.

6.24.4 The key considerations for option N3 are:


b) The cost of the scheme

c) Provide vehicular access to the land and allotments on the eastern side of the A4810.

d) Continuity of NMU access.




6.24.5 Appraisal

Table 6.19 Option N3 – NMU Appraisal Ch 20+200 Green Moor Lane

Sub-Option Number: N3d

Benefits Detriments

Weltag Economy Reduced construction cost None identified

Environment Reduced land take, as a route suitable for NMUs only would require a narrower track between the Steelworks Access Road and proposed M4, and smaller radii would be required with smaller visibility envelopes to allow safe passage of traffic.

None – SSSI land is not affected.

Social Maintains full NMU and vehicular access to the land and allotments

Vehicular access is now provided from Magor only, although there is no land between the proposed new motorway and the A4810 to which any access would be required.

Engineering Long term With only NMU access required under Llandevenny Railway bridge, the span of the structure could be reduced, possibly replaced with a separate underpass.

None identified.

Short term Avoids impacts on services in existing Green Moor Lane.

None identified.

Traffic Long term None identified. Longer diversion for vehicles wishing to access land and allotments, now required to travel via Blenheim Close, Magor. Additional traffic along Blenheim Close.


Safe by Design

Long term Removal of motor vehicles from bridge underneath the M4 increases safety for NMUs. In addition, removes the issues associated with cars travelling immediately adjacent to a live railway (headlights blinding train drivers, loss of control vehicles entering the tracks)

None identified.

Short term Simpler construction. None identified.

Deliverability Cost Reduced construction cost, as a route suitable for NMUs only would requires a narrower track between the Steelworks Access Road and proposed M4, and smaller radii would be required with smaller visibility envelopes to allow safe passage of traffic.

None identified

Risk Reduced construction complexity. Risk of objection from residents of Blenheim Close

Buildability Reduced construction complexity.

Programme Equivalent to the conceptual design

6.24.6 The proposed alternative for Green Moor Lane would minimise land required for the scheme and deliver a cost saving for the scheme. It would enable full vehicular access to be provided to the land and allotments to the east of the A4810. It is therefore recommended that the proposed alternative option N3d




is accepted into the scheme. The allotments and all access route options are outside the SSSI land.




7 Summary

7.1.1 Following a detailed review of the Key Stage 2 (KS2) design for the M4 Corridor around Newport scheme, a range of design options were developed which sought to improve the design, further mitigate impacts, and/or reduce the capital cost of the scheme.

7.1.2 The design options were appraised against the original KS2 design proposal and based upon their comparative performance, using a multi-criteria appraisal, recommendations have been made which advise on changes to the KS2 design in certain areas.

7.1.3 It is proposed that the recommendations of this report are taken forward and developed to create the draft orders which are planned to be issued in March 2016.

7.1.4 The options recommended are listed as follows in Table 7.1.

Table 7.20 List of options recommended for acceptance

Note: Chainages referred to are from the conceptual design drawings in Volume 2. The chainages will be different for the final draft Orders design.

Option No.

Brief Description Change to the Conceptual Design?

Effect on environmentally designated sites

Mainline

M1 Location along scheme: Chainage 4+400 – 5+000m.

M1b Mainline lowered and Church Lane side road raised. Mainline passes under Church lane side road.

Yes Would not require any additional SSSI land. This part of the proposed new motorway is outside the SSSI, which is entered at Ch 5+100.


M2b Mainline vertical alignment utilises a 4% gradient with no climbing lane



M3b Vertical alignment over Duffryn Rail Crossing providing a headroom clearance of 5.5m

Yes This part of the scheme lies within the SSSI from Ch 5+100 to 8+500. There would be a small increase in the land required by the scheme from the SSSI due to the increased embankment height.





Option No.



M4a Horizontal alignment positions the mainline to cross the South Wales Railway 350m east of Green Lane. Results in a high skew crossing of the M4 over the railway – the Conpetual design

No No change from the conceptual design. This part of the scheme lies within the SSSI from Ch 5+100 to 8+500.


M5b Horizontal alignment altered to introduce a straight alignment on the main span and back span. Realignment to reduce the skew to the River Usk, reducing the length of the crossing.

Yes There is no change to SSSI land taken by the scheme for option M5b and the positioning of the bridge in relation to the River Usk SAC is equivalent to the conceptual design.


M6b Mainline horizontal shift to the north by tightening up geometry to avoid impact upon pylon

Yes This part of the scheme lies within the SSSI from Ch 13+070 to 14+950.There is a slight benefit to the SSSI by moving the alignment further north.


M7a Horizontal alignment passing through Tata Steel slurry lagoons – the conceptual design

No No change from the conceptual design. This part of the scheme lies within the SSSI from Ch 13+070 to 14+950.


M8b Mainline was realigned to the south-east, which provided separation between the proposed M4 and the SAR.

Yes There is no change to SSSI land taken by the scheme for option M8b. This part of the scheme lies within the SSSI from Ch 16+650 to 20+100.


M9b The proposed M48 to existing M4 link dual carriageway road cross-section is modelled as a dual 2 lane all purpose road (D2AP)

Yes Would not require any additional SSSI land. This part of the proposed new motorway is outside the SSSI.


M10a Mainline cross-section incorporating a 1.6m wide central reserve with a vertical concrete barrier (VCB). Includes

No There is no change to SSSI land taken by the scheme.




Option No.



a departure.

Side Roads

SR1 Location along scheme: Chainage 4+630m - Church Lane

SR1b Church Lane passing over the proposed M4 as an overbridge


SR2 Location along scheme: Chainage 7+400m - Lighthouse Road

SR2b Lighthouse Road as an overbridge over the proposed M4, with the side road alignment offline and to the west of the existing Lighthouse Road

Yes This part of the scheme lies within the SSSI from Ch 5+100 to 8+500. Option SR2b would take more land from the SSSI to the west of the existing Lighthouse Road.

SR3 Location along scheme: Chainage 12+250m – Nash Road/Meadows Road

SR3d Replacement side road provided to the east of Nash Road, connecting Nash Road on the southern side of the proposed motorway to Meadows Road on the northern side of the motorway. The alignment is placed to the east of the commercial property on Meadows Road. The Meadows Road/Nash Road junction on the northern side of the motorway is stopped up. A connection is provided through the industrial estate between Nash Mead and Nash Lane.

Yes Whilst the proposed new motorway at this location is not within SSSI land, the southern end of the route of Nash Road for option SR3d would take more land from the SSSI than the existing Nash Road alignment for a length of 175m.

SR4 Location along scheme: Chainage 18+000m – North Row

SR4c Existing North Row stopped up, and realigned to the west of its current alignment to avoid impacting upon existing electricity pylon

Yes This part of the scheme lies within the SSSI from Ch 16+650 to 20+100. This option does require additional land from the SSSI due to the realignment of the side road.

Junctions and Interchanges

J1 Location along scheme: Chainage 1+500 – 4+400m – Castleton Motorway Interchange

J1b Mainline stays on-line but replaces existing motorway carriageway before crossing

Yes Would not require any additional SSSI land. This part of the proposed new




Option No.



over A48 and south-eastwards towards Duffryn. Eastbound links are located to the north of the proposed motorway corridor with the A48(M) merging with the eastbound diverge slip to form new A48(M), whilst the westbound links remain to the south.

motorway is outside the SSSI, which is entered at Ch 5+100.

J2 Location along scheme: Chainage 7+800 – 9+800m – Docks Way Motorway Junction

J2d Grade-separated roundabout junction on the proposed motorway connecting a new dual carriageway link road between the motorway and the SDR. The roundabout is located 200m further to the east in an effort to reduce the interface between the east-facing slip roads and the cable-stayed structure. A new link road would be aligned along the eastern edge of the Docks Way landfill site, connecting into a new roundabout in the northern side of the M4. From this roundabout, the link road connects into the new Docks Way junction on the northern side.

Yes This part of the scheme lies within the SSSI from Ch 5+100 to 8+500. Option J2b would take more land from the SSSI on the west bank of the River Ebbw.

J3 Location along scheme: Chainage 14+200 – 15+900m – Glan Llyn Motorway Junction

J3b Grade-separated roundabout junction on the proposed motorway connecting a new dual carriageway link road between the motorway and the SAR. Main junction roundabout positioned to the west of Monks Ditch.

Yes This part of the scheme lies within the SSSI from Ch 13+070 to 14+950. Option J3b would take more land from the SSSI.

J4 Location along scheme: Chainage 20+850m – Newport Road/ Steelworks Access Road Junction

J4a Newport Road/ Steelworks Access Road junction is provided as an at-grade roundabout with an inscribed circle diameter of 58m

No This part of the scheme lies within the SSSI from Ch 16+650 to 20+100.

J5 Location along scheme: Chainage 23+600m – M48 Roundabout

J5c At grade signalised ‘hamburger’ Yes Would not require any




Option No.



style through-about roundabout, with dedicated link for east-bound traffic from the reclassified M4 to the new M4

additional SSSI land. This part of the proposed new motorway is outside the SSSI.

J6 Location along scheme: Chainage 23+600m – Junction 23

J6c Grade separated M4 junction, with westbound free-flow link road between M4 and D2AP link to existing Junction 23A. New signalised junction and roundabout on B4245 to provide access to M4. Eastbound off, eastbound on and westbound on slip roads connected to M48 “through-about” (Westbound on slip makes use of existing M48 to M4 link road.)

Yes Would not require any additional SSSI land. This part of the proposed new motorway is outside the SSSI.

Structures

S1 Location along scheme: Chainage 8+400 – 8+600m – River Ebbw Structure

S1c Reduced length River Ebbw bridge with a span of 169m, which only spanned the River Ebbw. The sea wall reen was provided in a separate culvert adjacent to the bridge. Add New Dairy Farm overbridge to the west of the River Ebbw. Divert access track over new overbridge and do not provide the underpass.

Yes This part of the scheme lies within the SSSI from Ch 5+100 to 8+500. Option S1c would take more land from the SSSI.

Geotechnical

G1 Location along scheme: Embankments on Gwent Levels

G1a Embankments designed with 1 vertical to 2 Horizontal (1:2) side slopes.

No No change to the land required from the SSSI.

G2 Location along scheme: Castleton interchange cutting

G2a Designed with 1:3 side slopes due to lack of ground investigation during early design stages and poor nature of rock.


G3 Location along scheme: Castleton interchange embankment

G3a Embankments designed with 1:2 side slopes.


Drainage

D1 Location along scheme: Chainage 8+600 – 11+200m – River Usk Crossing Drainage Solution




Option No.



D1c Collect and carry all surface water from the R Usk bridge to new pollution treatment lagoon and WTA on the eastern side of the R Usk, and discharge into the R Usk through a new ditch

Yes There is no change to the land required for the scheme from the SSSI.


D2b Remove pond to avoid OH pylons and redesign the drainage network to accommodate drainage elsewhere.

Yes Would not require any additional SSSI land. This part of the proposed scheme is outside the SSSI.


D3b Move pond to chainage 5+800 and split into separate ponds either side of the M4 mainline to allow sufficient falls to the drainage network

Yes This part of the scheme lies within the SSSI from Ch 5+100 to 8+500. Option D3b would take more land from the SSSI.


D4b Relocate WTA to adjacent to Dyffryn Rail line

Yes This part of the scheme lies within the SSSI from Ch 5+100 to 8+500. The proposed and original location are within SSSI land and is of a similar area so there is no material net change to the land required from the SSSI.


D5b Pond moved to the north of carriageway

Yes Both the original and proposed location of the WTA are outside the SSSI.


D6b WTA moved east to avoid impacting upon the Tata reed bed area

Yes The proposed location is within SSSI land and is of a smaller area so there is net reduction to the land required from the SSSI.


D7b WTA remains on southern side of M4, but is moved to the east by approximately 400m

Yes The proposed and original location are within SSSI land and is of a similar area so there is no material net change to the land required from the SSSI.





Option No.



D8d Utilise the area between the existing Junction 23A and the new M4 as a secondary WTA. Locate the reed bed immediately to the north east of St Brides Road. This option would mean the WTA (and corresponding pipework) would be considerably smaller. 11a flows can be conveyed south into the catchment area for WTA10.

Yes The option moves water treatment area 11 entirely out of the SSSI.

D9 Location along scheme: Chainage 4+300 – 20+000 – Development of Reen Mitigation Strategy

D9b Provide compensatory reens along the whole of the Levels on the north side of M4 motorway carriageway with field ditches on south. Where possible use existing ditches instead of placing new ones on the south of highway to fit within the historical landscape

Yes Reduction of reens reduces the land take from the SSSI for ditches, although the overall effect on land required for the scheme is not significant.

D10 Location along scheme: Chainage 4+300 – 20+000 – Edge of Carriageway Drainage Detail

D10a Grass-lined channel No No change.

Highway Boundary Treatments

H1 Location along scheme: Embankments on Gwent Levels

H1b Move highway boundary fence closer to the toe of embankment to reduce impact on SSSI

Yes The land required from the SSSI is reduced compared with the conceptual design.

NNon-Motorised Users (NMU)

N1 Location along scheme: Chainage 5+700 – 6+100 – Green Lane/Percoed Reen

N1h Percoed Lane diverted over M4 mainline on an overbridge to the east. Green Lane connected into Percoed Lane, providing NMU only access across the M4 (lightweight structure).

Yes Both options are within the SSSI and there is no material difference in the amount of land taken from the SSSI.

N2 Location along scheme: Chainage 8+400 – Wales Coastal Path

N2c Provide for the Wales Coast Path and PMA route to cross the M4 using an overbridge provided online to the existing NMU and PMA route.

Yes This part of the scheme lies within the SSSI from Ch 5+100 to 8+500. Option S1c would take more land from the SSSI.

N3 Location along scheme: Chainage 20+220 – Green Moor Lane




Option No.



N3d Maintain Green Moor Lane, diverting alignment under Llandevenny Rail bridge. Access under M4 provided for NMUs only. Alternative vehicular access to allotments provided from Blenheim Close.

Yes This part of the scheme lies wholly outside the SSSI. No change.




7.1.5 The effects of the options on the land required for the scheme from the SSSI is summarised as follows:

Table 7.2 Summary of effects on land required from the SSSI

Category of Comparison to the Conceptual Design

No. of changes in Category

List of changes

As the conceptual design

8 M4a, M7a, M10a, J4a, G1a, G2a, G3a, D10a.

No change to the land required

17 M1b, M2b, M5b, M8b, M9b, SR1b, SR4c, J1b, J5c, J6c, D1c, D2b, D4b, D5b, D7b, N1h, N3d.

Benefits or reduction to the land taken from the SSSI

5 M6b, D6b, D8d, D9b, H1b,

More land required from the SSSI

8 M3b, SR2b, SR3d, J2d, J3d, S1c, D3b, N2c.

7.1.6 The impacts of the scheme on SSSI land are described in the Environmental Statement.

7.1.7 In respect of carbon and TPO 10, the options recommended principally relate to the detail of construction of the scheme and thus to the construction carbon. None of the recommended options materially affect the overall proposals for the scheme (a three lane new motorway to the south of Newport with reclassification of the existing M4 to the north of Newport and other complementary measures), which could have a material effect on the user carbon emissions of the scheme. The options are thus all considered neutral, when compared to the conceptual design, in respect of reducing user carbon emissions and achieving TPO 10.

7.1.8 Carbon was considered in the draft Plan stage of development of the M4 Corridor Around Newport in the Strategic Environmental Assessment. A detailed carbon calculation for the developing scheme has not been undertaken at this stage but is due to be completed as part of the Environmental Statement, due to the published in March 2016.

7.1.9 From experience of carbon calculations from other road schemes, the contribution of construction carbon to the overall lifetime carbon emissions of the scheme is very low (<5%). Any changes to the construction detail, such as options presented in this report, are thus




considered to have negligible effect on the overall lifetime carbon emissions for the M4CaN.

7.1.10 Following the design presentation to the Welsh Government on September 2 2015, the recommended options presented in this report were accepted by the Welsh Government as the scheme to take forward to prepare draft Orders and the Environmental Statement.



M4CaN-DJV-GEN-ZG-GEN-RP-CX-0001 | | 1October 2015

Appendix A

Initial, High Level Sift of Options – Appraisal Matrix

M4 CORRIDOR AROUND NEWPORT M4CaN-DJV-GEN-ZG_GEN-RP-CX-0002

HIGH LEVEL OPTION REVIEW - FULL ASSESSMENT (DESIGN OPTIONS REPORT: VOLUME 1 - APPENDIX A)

Option

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Mainline

M_1a

Church Lane - chainage 4+400 -

5+000 Mainline passes over Church Lane side road

M_1b Mainline passes under diverted Church Lane side road 0 0 0 N/A 0 1 0 N/A N/A 1 -1 1 2 0 0 1 0 0 1 0 0 0 0 0 0 0 0 0 0 2 0 1 0 0 1 5

M_2a

Duffryn - Chainage 3+700 to

5+000m 3% mainline vertical gradient (specimen)

M-2b 4% mainline vertical gradient (with no climbing lane) 0 N/A 0 N/A N/A 0 0 0 0 1 0 0 1 0 0 0 -1 -1 0 0 0 0 0 0 0 0 0 0 0 -2 0 1 0 0 1 0

M_2c 4% mainline vertical gradient (with climbing lane) 0 N/A 0 N/A N/A -1 0 0 0 1 0 0 0 0 0 0 -1 -1 0 0 0 0 0 0 0 0 0 0 0 -2 0 0 0 0 0 -2

M_3a

Levels - Chainage 5+900 to

7+130m Duffryn Railway Bridge - 4.78m headroom

M_3b Duffryn Railway Bridge - 5.5m headroom 0 N/A 0 1 0 -1 0 N/A N/A 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 N/A -1 0 0 -1 -1

M_4a


8+000m Alignment crosses railway 350m east of Green Lane (high skew)

M_4b Alignment crosses railway 250m west of Green Lane 0 N/A 0 1 0 1 0 N/A N/A 0 0 1 3 0 0 0 0 0 0 -1 0 0 0 0 0 0 0 -1 0 -2 0 0 -1 0 -1 0

M_4c

Relocate alignment to the north to cross Lighthouse Road and railway

simultaneously 0 N/A -1 -1 0 -1 0 N/A N/A 0 -1 -1 -5 0 0 -1 -1 -1 -1 1 0 0 0 0 0 0 0 -1 0 -4 0 -1 -1 -1 -3 -12

M_5a

Usk Crossing - Chainage 8+800

to 11+400m Conceptual design horizontal alignment passing over the River Usk crossing

M_5b Alignment alteration to straighten bridge and reduce skew -1 0 0 0 N/A 1 N/A 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 3 4

M_6a


14+000m Conceptual design horizontal alignment passing Solutia

M_6b Horizontal shift to the north to avoid impact upon pylon at CH 12+675 0 0 -1 N/A 0 0 0 N/A N/A 0 1 1 1 0 -1 0 0 0 0 0 0 0 0 0 0 0 0 -1 0 -2 0 1 1 1 3 2

M_7a


15+350m Conceptual design alignment passing through Tata Steel slurry lagoons

M_7b

Shifting the mainline alignment north into the contaminated land at Tata

Steel 0 -1 0 N/A 0 0 0 0 0 -1 -1 -1 -4 0 0 0 0 0 0 0 0 0 -1 0 0 0 0 0 0 -1 0 -1 -1 -1 -3 -8

M_8a

Magor - Chainage 19+000 to

20+300m Conceptual design alignment in the vicinity of Llandevenny rail bridge

M_8b Horizontal alignment shift south-east to avoid clash with the SAR 0 N/A 1 0 1 0 0 N/A N/A 1 1 1 5 0 0 0 0 0 0 -1 0 0 0 0 0 0 0 0 0 -1 0 1 1 1 3 7

M_9a

Magor - Chainage 21+000 to

23+600m

Conceptual design, utilising a D2M cross section for new M48 - reclassified

M4 link

M_9b Cross section reduction to D2AP 0 0 0 0 1 1 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 -1 0 1 0 0 0 0 0 1 0 0 1 3

M_10a

Whole scheme - Chainage

0+000 to 23+600m D3M, with 1.6m wide central reserve (except Usk crossing)

M_10b

Narrow central reserve of 1.2m wide, 10.5m carriageways, 3.0m hard

shoulder (except Usk crossing) -1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 1 0 -1 0 1

M_10c Compliant TD27 cross section design 1 0 0 0 0 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 -1 0 0 0 0 0 0 0 0 0 -1 0 -1 0 1 0 -1

Side Roads

SR_1a

Church Lane - Chainage

4+630m Church Lane passing under the M4CaN - Church Lane remains in-situ

SR_1b Church Lane overbridge - Church Lane realigned 1 N/A 0 N/A 0 1 0 0 0 1 -1 -1 1 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 2 0 1 0 0 1 4

OtherEngineering WelTag

Economy Environment Social



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SR_2a

Lighthouse Road - Chainage

7+400m Online alignment, overbridge over M4CaN

SR_2b Offline alignment to the west, overbridge over M4CaN 1 N/A 0 N/A 0 0 0 N/A 0 0 1 1 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 4 7

SR_2c Offline alignment to the east, overbridge over M4CaN 1 N/A 0 N/A 0 0 0 N/A 0 0 1 1 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1 0 -1 1 -1 -1 0 -1 1

SR_3a

Nash Road/Meadows Road -

Chainage 12+250m Conceptual design diverting Nash Road to the west

SR_3b Alignment to the west to connect to Nash Mead 0 N/A 0 N/A 0 0 0 N/A N/A 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1 0 0 -1 -1

SR_3c Alignment to the east, but west of IAC, to connect to Meadows Road -1 N/A 0 N/A 0 0 0 N/A N/A 0 0 0 -1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 2 0 1 0 -1 0 1

SR_3d Alignment to the east, and east of IAC, to connect to Meadows Road 0 N/A 0 N/A 0 0 0 N/A N/A 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0 -1 0 1 0 1 0 0 1 2

SR_4a

North Row - Chainage

18+000m Conceptual Design - minor realignment parallel to the east

SR_4b

North Row diverted to the east, avoiding pylon - high skew crossing of

M4CaN -1 N/A 0 N/A 0 -1 0 N/A N/A 0 1 1 0 0 0 0 0 0 0 -1 0 0 0 0 0 0 0 0 0 -1 0 1 1 1 3 2

SR_4c Alignment to the west to avoid pylon diversions -1 N/A 0 N/A 0 0 0 N/A N/A 0 1 1 1 0 0 0 0 0 0 -1 0 0 0 0 0 0 0 0 0 -1 0 1 1 1 3 3

SR_4d Stop up North Row and divert through Bareland Street 0 N/A 0 N/A -1 1 0 N/A N/A 0 1 1 2 0 0 0 0 0 0 -1 0 0 0 0 0 -1 0 0 0 -2 -1 1 1 1 2 2

Junctions

J_1a

Castleton Interchange -

Chainage 1+500 to 4+400m Conceptual Design - freeflow links, reduced scheme footprint, minimum cut

J_1b Reconfigured link arrangement, wider scheme footprint 0 0 0 N/A 0 1 0 0 0 -1 1 1 2 0 0 0 0 0 -1 -1 0 0 0 0 0 0 0 -1 0 -3 0 1 1 1 3 2

J_1c

2006 TR111 Castleton interchange design - much wider scheme footprint,

much larger cutting 0 0 0 N/A 0 -1 0 0 0 -1 0 0 -2 0 0 0 0 0 -1 -1 0 0 0 0 0 0 0 0 0 -2 0 -1 1 1 1 -3

J_1d M4 - reclassified M4 eastbound early diverge link 0 0 0 N/A 0 1 0 0 0 -1 0 0 0 0 0 0 0 0 -1 -1 0 0 0 0 0 0 0 0 0 -2 0 -1 1 1 1 -1

J_2a

Docks Way Grade Separated

Junction - Chainage 7+800 to

9+800m

Conceptual design - providing a grade-separated roundabout junction and

new dual carriageway link road to connect back to SDR

J_2b

Relocate the Docks Junction to the west and loop the link road to the south.

New underbridge required. -1 0 0 N/A 0 -1 0 0 0 0 0 -1 -3 0 0 0 0 0 0 0 0 0 0 -1 0 0 0 -1 0 -2 0 1 -1 0 0 -5

J_2c

Relocate the Docks Junction to the west and connect the link road to the

south via a new roundabout to reduce land loss at Newport Dock 0 0 0 N/A 0 -1 0 0 0 0 0 -1 -2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1 0 -1 -1 1 -1 0 -1 -4

J_2d

Relocate the Docks Junction to the west and connect the link road to the

north via a new roundabout with a shorter eastbound merge slip 0 0 0 N/A 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1 1 0 0 0 0

J_3a

Glan Llyn Grade Separated

Junction - Chainage 14+200 to

15+900m

Conceptual design - New grade-separated roundabout junction with dual

carriageway link to connect with SAR

J_3b Relocate junction to the west to avoid pylon diversion 0 0 0 N/A N/A 0 0 0 0 0 1 1 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 3 5

J_3c Dumbbell junction arrangement to required reduce number of structures 0 0 0 N/A N/A 1 0 0 0 1 0 1 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1 1 1 1 2 5

J_4a

Newport Road/ Steelworks

Access Road Junction -

Chainage 20+850m Conceptual design - At grade roundabout, ICD 58m

J_4b Signalised crossroads 0 N/A 0 N/A 1 N/A 0 0 0 0 0 1 2 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 -1 1 0 0 0 3

J_5a

M48 roundabout - Chainage

23+600m Conceptual design - at grade roundabout, ICD 100m

J_5b

Partially signalised at-grade roundabout, ICD of 100m with segregated free

flow left turn lanes 0 0 1 N/A N/A N/A 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1 -1 0 0 -2 -1



Option


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J_5c

At grade signalised ‘hamburger’ style throughabout roundabout, with

dedicated link for east-bound traffic from the reclassified M4 to the new M4 0 1 1 N/A N/A N/A 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 -1 0 0 0 2

J_6a

M4 Junction 23 - Chainage

23+600m Conceptual design - Grade-separated roundabout junction, ICD 100m

J_6b

Grade-separated signalised roundabout motorway junction, comprising a

two-bridge elongated roundabout, ICD of 90m. Solution utilised the existing

B4245 underbridge (under existing M4) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1 -1 0 0 -2 -2

J_6c

Grade separated junction, with westbound free-flow link between M4 and

D2AP link to J23A. New signalised junction and roundabout on B4245 to

provide access to M4. Eastbound off, eastbound on and westbound on slip

roads connected to M48 “throughabout”. 0 1 1 0 1 -1 -1 -1 0 -1 0 -1 -2 0 0 -1 0 0 -1 -1 -1 0 0 1 0 1 0 0 0 -2 1 -1 0 0 0 -4

J_6d

As J6c, but including an additional eastbound free-flow link road between

D2AP and M4 eastbound. M48 junction no longer “throughabout”, but

conventional signalised roundabout. 0 1 1 0 1 -1 -1 -1 0 -1 0 -1 -2 0 0 -1 0 0 -1 -1 -1 0 0 1 0 1 0 0 0 -2 1 -1 0 0 0 -4

Structures 0 0

S_1a

River Ebbw Structure -

Chainage 8+400 to 8+600m Conceptual design - 193m long span over Ebbw 0

S_1b Shortened bridge span (169m) and provide an underpass and culvert 0 0 0 N/A 0 0 0 0 0 0 0 1 1 0 0 0 0 0 1 -1 0 0 0 1 0 0 0 0 0 1 0 1 0 0 1 3

S_1c

Shortened bridge span (169m). Add New Dairy Farm overbridge, remove

underpass. Divert access track over new overbridge 0 0 0 N/A 0 0 0 0 0 0 0 1 1 0 0 0 0 0 -1 -1 0 0 0 1 0 0 0 0 0 -1 1 0 0 0 1 1

Geotechnical

G_1a

Embankments on Levels -

Chainage 5+100 to 19+200m Embankment side slopes - 1V : 2H side slopes.

G_1b Steepen side slopes to 1:1.5 to reduce earthworks and land take 0 0 0 0 0 1 0 0 0 -1 0 -1 -1 0 0 0 0 0 -1 1 0 0 0 0 0 0 0 0 0 0 0 -1 0 -1 -2 -3

G_1c

Slacken side slopes to 1:2.5 to reduce earthworks risk with soft underlying

ground 0 0 0 0 0 -1 0 0 0 1 0 0 0 0 0 0 0 0 0 -1 0 0 0 0 0 0 0 0 0 -1 0 -1 0 1 0 -1

G_2a

Castleton interchange cutting -

Chainage 2+500 to 3+600m

Cutting designed with 1V : 3H side slopes due to lack of GI in early stages

and the nature of the rock.

G_2b Steepen side slopes to 1:2 to reduce earthworks and land take 0 0 0 0 0 1 0 0 0 -1 0 -1 -1 0 0 0 0 0 -1 0 0 0 0 0 0 0 0 1 0 0 0 1 0 -1 0 -1

G_3a

Castleton interchange

embankment - Chainage 3+700

to 4+300m Embankment side slopes of 1V : 2H

G_3b Steepen side slopes to 1:1.5 to reduce earthworks and land take 0 0 0 0 0 1 0 0 0 -1 0 -1 -1 0 0 0 0 0 -1 0 0 0 0 0 0 0 0 1 0 0 0 -1 0 -1 -2 -3

Drainage

D_1aRiver Usk Crossing Drainage -

Chainage 8+600 to 11+200m

Conceptual design - Drainage to outfalls in existing dock area (both sides of

the Usk)

D_1b

Discharge into an existing pond and secondary waterway on the eastern

bank of the River Usk. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1 0 0 0 0 0 0 0 -1 0 1 -1 0 0 -1

D_1c

Discharge into Usk via ditch, after treatment in pollution treatment lagoon

and Water Treatment Area. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 -1 0 0 -1 0

D_2aLocation of WTA No. 3 -

Chainage 4+700m

Water treatment area located to north of Church Lane to provide

attenuation lagoon for underbridge

D_2bRemove pond, as underbridge has become overbridge, and pond located in

area with OH pylons0 0 1 0 0 0 0 0 0 0 1 1 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 3 6



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D_3a

Location of WTA No. 4 -

Chainage 6+000mWTA is located adjacent to All Saints Church

D_3b Move pond to new location, and split to north and south of carriageway 0 0 0 0 0 0 0 0 0 0 1 1 2 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 2 0 1 0 0 1 5


Chainage 7+200mPond south of M4CaN located between Pont-y-Cwcw and River Ebbw Sea

Wall Reen

D_4b Pond repositioned to west of Lighthouse Road, adjacent to Dyffryn Rail line

0 0 0 0 0 0 0 0 0 0 1 1 2 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 1 0 0 1 4

D_5a


Chainage 12+900mPond located to the east of Nash Road, to the west of Julians Reen on the

southern side of the M4CaN

D_5b Pond moved to the north side of the M4CaN 0 0 0 0 0 0 0 0 0 0 1 1 2 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 1 0 0 1 4

D_6a


Chainage 14+200mPond located to north of M4CaN carriageway in Tata secondary reed bed

D_6b

Pond moved east to avoid taking the reed bed area used as a secondary

treatment area by Tata. 0 0 0 0 0 0 0 0 0 1 0 1 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2

D_6cPond moved into the Tata 'ecological' area

0 0 0 0 0 0 0 0 0 0 0 -1 -1 0 0 0 0 0 -1 -1 0 0 0 0 0 0 0 0 0 -2 0 0 0 0 0 -3

D_6d Pond moved to south of Glan Llyn Junction 0 0 0 0 0 0 -1 0 0 1 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1 0 0 -1 0

D_7a


Chainage 19+200mPond located on the south side of the M4CaN, opposite the Europark

D_7b Pond moved to east of the conceptual design location 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0


Chainage 21+000m

Route surface water runoff from the new M4 adjacent to junction 23A in a

south westerly direction to a WTA located immediately to the south of the

rail link.

D_8b

Raise the alignment of the B4245, (Newport Road) which would allow the

majority of the M4 between Ch 20400 and 21000 to drain in an easterly

direction into the catchment of the St Brides Brook/Mill Reen.

0 0 0 0 0 -1 0 0 0 -1 0 0 -2 0 0 0 0 0 0 0 0 -1 0 0 0 0 0 0 0 -1 0 0 0 0 0 -3

D_8c

Utilising the area between the existing Junction 23A and the new M4 as a

secondary WTA. Locate the reed bed immediately to the east of St Brides

Road. This option would mean the original WTA (and corresponding

pipework) would be considerably smaller.

0 0 0 0 0 -1 0 0 0 -1 0 0 -2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -2

D_8d

Same as D_8c but with a third pond located to the north east of St. Brides

Road. This pond would again be formed from a borrow area . WTA 11a

flows can be conveyed south into the catchment area for WTA10. 0 0 1 1 0 0 1 0 0 -1 0 0 2 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 3



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D_9a

Development of Reen

Mitigation Strategy - Chainage

5+100 to 19+200m

Provide compensatory reens along the whole of the Levels, on both sides

where possible.

D_9b

Provide compensatory reens along north side of carriageway with field

ditches on south. Where possible use existing ditches to instead of placing

new ones on the south of highway to fit within the historical landscape. 0 0 0 0 0 0 1 0 0 1 0 1 3 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 2 0 1 0 0 1 6

D_10a

Edge of carriageway drainage

detail Grass lined channel

D_10b Concrete lined channel 0 0 0 0 0 0 1 0 0 -1 0 0 0 0 0 0 0 0 -1 -1 0 0 0 0 0 0 0 0 0 -2 0 0 0 0 0 -2

D_10c Rockfill channel 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 -1 -1 0 0 0 0 0 0 0 0 0 -2 0 0 0 0 0 -1

Highway Boundary Treatment Options

H_1a

Embankments on Gwent Levels

- Chainage 5+100 to 19+200m

Highway boundary fence offset 3m from the toe of the embankment/ cut off

ditch.

H_1b

Move highway boundary fence closer to the toe of embankment to reduce

impact on SSSI 0 0 0 0 0 0 0 0 0 -1 0 0 -1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 1 0 -1 0 0

Complementary Measures Options

Refer to Complimentary measures Options Report

NMU

N_1a

Green Lane/ Percoed Cycle

Track - Chainage 5+700 to

6+100m

Green Lane diverted under M4 mainline in an underbridge to the west.

Percoed Lane diverted into same underbridge to maintain connectivity.

Resultant solution provides for NMU and Private Means of Access (PMA)

N_1b

Green Lane and Percoed Lane both stopped up. No connectivity provided

across M4 for NMUs or PMA at this location. 0 0 -1 0 -1 1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 -1 -1 -1 0 -1 0 -4 0 1 0 1 2 -2

N_1c

Green Lane diverted over M4 mainline across an overbridge to the west.

Percoed Lane diverted onto same overbridge to maintain connectivity.

Resultant solution provides for NMU and PMA access across the M4. 0 0 0 0 0 -1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 2 0 0 0 -1 -1 1

N_1d

Green Lane diverted over M4 mainline on an overbridge to the west.

Percoed Lane diverted onto same overbridge to maintain connectivity.

Resultant solution provides for NMUs only (lightweight structure) 0 0 0 0 -1 -1 0 0 0 1 0 0 -1 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 2 0 -1 0 -1 -2 -1

N_1e


Percoed Lane diverted into same underbridge to maintain connectivity.

Resultant solution provides for NMUs only (reduced headroom structure) 0 0 0 0 -1 -1 0 0 0 0 0 0 -2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 -1

N_1f

Percoed Lane diverted over M4 mainline on an overbridge to the east. Green

Lane connected into Percoed Lane, providing NMU and PMA access across

the M4 0 0 0 0 0 -1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 2 0 -1 0 -1 -2 0

N_1g

Percoed Lane diverted under M4 mainline through an underbridge to the

east. Green Lane connected into Percoed Lane, providing NMU and PMA

access across the M4 0 0 0 0 0 -1 0 0 0 0 0 0 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1

N_1h

Percoed Lane diverted over M4 mainline on an overbridge to the east. Green

Lane connected into Percoed Lane, providing NMU only access across the

M4 (lightweight structure) 0 0 0 0 0 -1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 2 0 -1 0 -1 -2 0

N_1i


east. Green Lane connected into Percoed Lane, providing NMU only access

across the M4 (reduced headroom structure) 0 0 0 0 0 -1 0 0 0 0 0 0 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0

N_1j


east. Green Lane stopped up. NMU only access across the M4 (reduced

headroom structure) 0 0 -1 0 0 -1 0 0 0 0 0 0 -2 0 0 0 0 0 0 0 0 0 0 0 0 -1 0 -1 0 -2 0 1 0 0 1 -3

N_1k

Percoed Lane diverted over the M4 mainline over an overbridge to the east.

Green Lane stopped up. NMU only access across the M4 (lightweight

structure) 0 0 -1 0 0 -1 0 0 0 1 0 0 -1 0 0 0 0 0 0 0 0 0 0 1 1 -1 0 -1 0 0 0 -1 0 -1 -2 -3



Option


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N_1l


Percoed Lane stopped up. Resultant solution provides for NMUs only

(reduced headroom structure) 0 0 -1 0 -1 -1 0 0 0 0 0 0 -3 0 0 0 0 0 0 0 0 0 0 0 0 -1 0 -1 0 -2 0 1 0 0 1 -4

N_1m

Green Lane diverted over M4 mainline on an overbridge to the west.

Percoed Lane stopped up. Resultant solution provides for NMUs only

(lightweight structure) 0 0 -1 0 -1 -1 0 0 0 1 0 0 -2 0 0 0 0 0 0 0 0 0 0 1 1 -1 0 -1 0 0 0 -1 0 -1 -2 -4

N_2a

Wales Coastal Path - Chainage

8+400m

Provide for the Wales Coast Path to cross M4 through the Ebbw River

structure. Diverting PMA and NMU route alongside the proposed motorway

from the point where the motorway would cross the existing alignment of

the NMU and PMA route.

N_2b

Provide for the Wales Coast Path to cross M4 through a separate structure

behind the abutment of the Ebbw River structure. Diverting PMA and NMU

route alongside the proposed motorway from the point where the

motorway would cross the existing alignment of the NMU and PMA route. 0 0 0 0 0 -1 0 0 0 0 0 0 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1 0 0 -1 -2

N_2c

Provide for the Wales Coast Path and PMA route to cross the M4 using an

overbridge provided online to the existing NMU and PMA route. 0 0 0 0 1 -1 0 0 0 -1 0 0 -1 0 0 0 0 0 -1 0 0 0 0 0 0 0 0 0 0 -1 0 -1 0 0 -1 -3

N_3a

Green Moor Lane - Chainage

20+220m

Maintain Greenmoor Lane, diverting alignment under Llandevenny Rail

bridge. Maintain vehicular access across the M4 (existing reduced headroom

under SAR bridge)

N_3b Stop up Greenmoor Lane, do not provide access across the M4 0 0 -1 0 -1 0 0 0 0 0 0 0 -2 0 0 0 0 0 0 0 0 0 0 -1 0 -1 -1 -1 0 -4 -1 1 0 1 1 -5

N_3c


bridge. Access provided for NMUs only. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1 0 0 0 -1 -1

N_3d


bridge. Access under M4 provided for NMUs only. Alternative vehicular

access to allotments provided from Blenheim Close. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

N_3e

Maintain Greenmoor Lane on its current alignment, passing over the M4 on

overbridge, or via an underbridge. -1 0 0 0 0 0 0 0 0 0 0 0 -1 0 0 0 0 0 -1 0 0 0 0 0 0 0 0 0 0 -1 0 -1 0 0 -1 -3

N_3f

Stop up existing Greenmoor Lane. Divert to the north, connecting into

existing SAR roundabout. New Greenmoor Lane alignment passing over M4

on overbridge. -1 0 0 0 0 0 0 0 0 0 0 0 -1 0 0 0 0 0 -1 0 0 0 0 0 0 0 0 0 0 -1 0 -1 0 0 -1 -3




Appendix B

Lighthouse Road Options Development File Note

File Note

Prepared by Page 1 of 1

Date of circulation

Project title M4CaN

cc File reference

Prepared by Andrew Jones Date

14/01/2016

Subject Lighthouse Road Option Development

DOCUMENT CHECKING (not mandatory for File Note)

Prepared by Checked by Approved by

Name Andrew Jones Andy Keen Stephen Hall

1 Introduction

1.1 This File Note has been prepared to document the development of the layout and

alignment of the Lighthouse Road side road, where it crosses the proposed M4 corridor

around Newport (M4 CaN) alignment.

1.2 The note provides an overview of the current alignment of Lighthouse Road, identifying

the key features, and presents the options considered in the development of the

preferred option.

1.3 Details relating to vehicle swept paths have been added at the request of the Welsh

Government in response to queries raised at the public information exhibition. Also

details of alternative junction layouts into Fair Orchard Farm are included.

File Note

Project title Job number Date of Meeting

M4CaN

\\AWSPWOICS03\ICSJOB_WORKINGDIR\12806\7857_34\M4CAN-DJV-HSR-Z2_GEN-FN-CH-0001.DOCX

2 Existing Layout

2.1 Lighthouse Road in the vicinity of the M4 CaN is a single carriageway road of

approximately 5.6m paved width. It is lined with hedgerows behind a narrow verge and

has the characteristic of a meandering country lane.

2.2 There is an 11KV overhead powerline in the west verge of Lighthouse Road in this

location. There is also a medium pressure gas main and foul sewer in the carriageway.

Figure 1- Existing Lighthouse Road

White Cross Farm

Fair Orchard Farm

Ty-Hir

Proposed M4CaN CL

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2.3 There is a high voltage power line which crosses Lighthouse Road in a north east

orientation. This western power utility will be diverted further away from Lighthouse

Road with a new pylon placed to the north of the mainline. This diversion is therefore

not a key consideration in the evaluation of options discussed in this note.

2.4 Over this section of Lighthouse Road, the existing horizontal alignment comprises a

series of straight tangents and tight curves as low as 70m in radius. There is a

residential property situated between the South Wales Railway mainline and

Lighthouse Road called White Cross Farm, and Fair Orchard Farm is located directly

adjacent to the east (see Figure 1). Both of these properties are accessed directly from

Lighthouse Road. There is a property called Ty-Hir on the west of Lighthouse Road

south of the proposed M4 CaN, also directly accessed from Lighthouse Road.

2.5 The centreline of the proposed M4 CaN alignment is illustrated on Figure 1.

2.6 To the north of the proposed M4 CaN, Lighthouse Road crosses over the South Wales

Mainline railway on structure. The bridge deck, which has been replaced recently,

crosses over the railway with tight approach radii of approximately 70m either side of

the bridge.

2.7 As Lighthouse Road passes over the railway bridge, no central intermittent white

‘hazard warning’ lines are provided and ‘SLOW ARAF’ (see Figure 2) warning markings

are used on either approach. The vertical alignment over the railway comprises ramps

either side leading to a flat deck (i.e. instantaneous changes in gradient on both

approaches).

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Figure 2 - Bend on Lighthouse Road (Looking South)

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3 Option 1 - Conceptual Design

3.1 Overview

3.1.1 Option 1 is the conceptual design (developed during Key Stage 2) for dealing with the

impact to Lighthouse Road as a result of the M4CaN scheme.

3.1.2 This option consisted of taking Lighthouse Road over the proposed motorway on a new

overbridge, using a horizontal alignment largely utilising the corridor of the existing

road. Option 1 is presented in Figure 3.

3.1.3 Horizontally, the alignment would connect into the existing road at southern end of the

existing SWM railway bridge. Radii used are relatively large resulting in a good

horizontal alignment over the length of the improvement.

3.1.4 From the SWM railway bridge, the vertical alignment would provide the new road on

embankment from the railway to the new overbridge over the M4CaN before dropping

back down to meet the existing road levels to the south of the M4CaN. The M4CaN is

on a low embankment in this location, which results in the Lighthouse Road overbridge

requiring embankments of up to 10m high.

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Figure 3 - KS2 Layout in Plan

3.2 Assessment

3.2.1 In relation to the existing alignment of Lighthouse Road, the conceptual design would

improve the tight horizontal curve in the road at the southern extent of the existing

railway bridge, but the tight horizontal radius on the northern side of the railway bridge

would remain.

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3.2.2 Option 1 would impact upon the existing 11kv overhead power lines, the medium

pressure gas main and foul sewer along the existing road. As a result, these would be

required to be diverted twice - once for the construction of the approach embankments

(into a temporary location during the construction phase), and a second time when they

would be replaced to their permanent location. A double-diversion of utility services

would be expensive, have an impact upon programme, and would increase the health

and safety risk of working with utilities.

3.2.3 The provision of access to residential properties, farms and field accesses would be

problematic with Option 1. The existing access to the residential property of White

Cross Farm on the western side of Lighthouse Road would be severed by the new

embankment for Lighthouse Road, and the elevation difference between the residential

property and the new road would result in gradient problems, meaning longer access

ramps would be required to maintain direct access onto the road. Providing a ramp with

acceptable gradients would require additional landtake from the property. In addition,

providing access during the construction phase would be complex.

3.2.4 Similarly, providing access to the farm land to the north of the M4 CaN corridor would

be challenging due to the level differences and pose similar access difficulties.

3.2.5 The online nature of the conceptual design would mean that keeping the road open

during the construction phase would require a temporary diversion of the road, or a

complete closure. This would be disruptive to local traffic.

4 Option 2 - Alignment to the East

4.1 Overview

4.1.1 Option 2 comprises an alignment to the east of the existing Lighthouse Road, as

illustrated on Figure 4. From the tie-into the existing alignment of Lighthouse Road, on

the southern side of the SWM bridge, horizontally, Option 2 would align Lighthouse

Road straight off the existing SWM bridge (improving the geometry on the approach to

the bridge), would incorporate a single curve turning onto another straight to cross over

the M4CaN on a skewed crossing before connecting back into Lighthouse Road near

Fair Orchard Farm.

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Figure 4 - Option 2

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4.2 Assessment

4.2.1 Option 2 would provide a reasonable horizontal alignment, but would have a significant

impact upon the farm buildings of Fair Orchard Farm which lies to the east of the

existing Lighthouse Road.

4.2.2 Given the scale of impact upon the farm Option 2 would have, and the fact other, less

impacting options exist, Option 2 was rejected.

5 Option 3 - Offline to the West

5.1 Overview

5.1.1 Option 3 considers an offline design to the west of the existing Lighthouse Road, see

Figure 5.

5.1.2 Horizontally, Option 2 connects into the existing Lighthouse Road 110m to the south of

the SWM railway bridge. The alignment comprises a minimum curve of 100m radius,

which is similar to the existing alignment, and is in keeping with the current nature of

Lighthouse Road.

5.1.3 The vertical alignment results in approach embankments of up to 10m high on either

side of the bridge. These connect to a minimum standard crest curve over the M4 CaN,

and tie in to the existing road, minimising the extent of the footprint.

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Figure 5 - KS3 Lighthouse Road (Plan View)

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5.2 Assessment

5.2.1 The Option 3 horizontal alignment results in an improvement in comparison to the

existing layout, resulting in a longer straight section between the back to back curves

between the overbridge over the M4 CaN and the railway bridge. This would provide

improved forward visibility in both directions, and constitute an improvement in driver

safety. This would be further enhanced with the provision of 2.5m wide verges being

incorporated into the design, further optimising forward visibility around the curves.

5.2.2 At the northern end, the tie-in with the existing Lighthouse Road is further south when

compared with Option 1. This has the benefit of not affecting the existing access to

White Cross farm to the south of the railway.

5.2.3 The Option 3 layout would have no direct impact upon the boundary of Ty-Hir which is

the property on the south west of the existing road.

5.2.4 The residual carriageway would be utilised as access roads for Fair Orchard Farm, and

for field access to the north of the proposed M4. These accesses would be located at

either end of the approach embankments of the proposed side road diversion.

5.2.5 Option 3 would enable the overhead and buried utilities currently within the existing

road corridor to be diverted once into the verge of the proposed side road diversion.

This would represent a significant cost-saving for the project and is in direct contrast to

Option 1.

5.2.6 Realigning Lighthouse Road offline would mean that the existing Lighthouse Road

could remain open during the construction phase, while the new offline road is

constructed. This would provide minimum disruption to local traffic, and minimise

programme risks.

5.2.7 With the residual existing road being used as access roads for Fair Orchard Farm (to

the south of the M4CaN) and to serve as access to fields to the north of the M4CaN,

this would result in two new junctions with Lighthouse Road.

5.2.8 The new junction which provides access to Fair Orchard Farm has been tested to

ensure large vehicle access can be provided. A conservative approach has been

taken by considering the suitability of a 15.5m long Freight Transport Association (FTA)

Design Articulated Vehicle in the swept path analysis.

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5.2.9 As a starting point we have analysed the two existing entrances to Fair Orchard Farm

from Lighthouse Road. The swept path for the northern access, the larger of the two,

is shown in Figure 7.

Figure 7 – Swept path from Existing Lighthouse Road into the north entrance to Fair

Orchard Farm

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5.2.10 It can be seen that the vehicle can enter the Farm, however would completely block

Lighthouse Road to other traffic during this event which would only be safe using banks

men. It is unlikely therefore, that this vehicle would visit fair Orchard Farm on a regular

basis, however we feel it is appropriate to consider compliance with this vehicle as an

objective in the design of the proposed layout.

5.2.11 In the proposed layout the 15.5m vehicle can make the turn into the remaining section

of Lighthouse Road as seen in Figure 8. This will require some adjustment to the

levels in order to create a suitable planar turning surface.

Figure 8 – Swept path for proposed Lighthouse Road

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5.2.12 Alternatively the vehicle could reverse in and out, and use the lane network to the

south to change direction and exit the levels.

5.2.13 Consultation will be required with the owner of the Farm to ascertain their requirement

for access.

5.2.14 An alternative access layout is presented in Figure 9 below. This layout is more like a

standard T junction layout and would be easier for HGV’s to negotiate than the existing

accesses due to the inclusion of standard entry and exit radii. However this requires

construction of a new access and into the south yard of Fair Orchard Farm. A short

culvert would be required as there is a watercourse running parallel to the east of

lighthouse road. A gate feature could be provided as accommodation works. The

existing section of lighthouse road to remain with the same alignment and would serve

as a short link between the existing access points to the farm. This solution will likely

require an amendment to the orders proposed as of Jan 2016.

Figure 9 – New Access Location

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5.2.15 A second alternative access layout is presented in Figure 10 below. This layout

provides a left in / right out movement and uses the footprint of the existing Lighthouse

Road to provide the left out movement. A triangular shaped area of landscaping would

be provide in the middle to enhance the appearance of the layout. This solution can be

provided within the orders as of January 2016. However this solution relies on

modifications to the vertical alignment of the existing section of Lighthouse Road

directly outside of Fair Orchard Farm.

Figure 10 – New Access Location

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6 Summary and Conclusion

6.1 Three layout options were considered for the Lighthouse Road side road diversion,

required as a result of the M4 Corridor around Newport scheme.

6.2 The conceptual design (Option 1) was assessed to result in significant earthworks,

removed any usable sections of the existing road (making construction traffic

management difficult), impact upon existing utilities (increased cost and risk) and

provide difficulties maintaining access for local properties. For these reasons, Option 1

has been rejected.

6.3 Option 2, an offline design to the east of the existing Lighthouse Road, resulted in

significant impacts to Fair Orchard farm and was rejected as other, less impacting

options existed.

6.4 Option 3, an offline design to the west of the existing Lighthouse Road, minimised

disruption to existing traffic during construction, minimised impacts to residential

properties along the route, provided an improvement upon the existing horizontal

alignment, and represented the lowest cost and risk option. For these reasons, Option

3 was the preferred option within the Key Stage 3 design.

6.5 A conservative vehicle swept path analysis was undertaken to test if a 15.5m long

articulated vehicle could access Fair Orchard Farm via the new proposed junction

arrangement. Results show that this vehicle can be accommodated, although with

some difficulty not to dissimilar to the existing situation. Smaller vehicles would be able

to access the farm as before.

6.6 Alternative access layouts have been identified to provide easier and safer access

particularly for HGV’s (refer to 5.2.14 and 5.2.15). These can be developed in

conjunction with the requirements of the landowner.




Appendix C

Review of Fence Line Location File Note

/

File Note

Page 1 of 9

Project title M4 CaN

cc File reference

Prepared by Kyla Nunn, Huw Richards, Tom

Edwards, Peter Ireland Date

01/03/16

Subject Review of fence line location along Gwent Levels



Name Kyla Nunn/ Tom Edwards/ Huw Richards

Peter Ireland Stephen Hall

1. Introduction and Background This technical note presents a review of the location of the highway boundary fence line along the

Gwent levels in order to reduce potential impact on the Sites of Special Scientific Interest (SSSIs).

This review discusses the land acquisition, design, environmental, safety and construction impacts for

a boundary fence offset (See Figure 1) originally considered to be 3.0m from the toe of highway

embankment/ cut off ditch, and considers a potential reduction in offset to 1.0m.

Section 28 of the Wildlife and Countryside Act 1981 (“the 1981 Act”) gives statutory powers to

Natural Resources Wales (NRW) to designate land as a SSSI, by reason of any of its flora, fauna, or

geological or physiological features. The protection of such designated sites was further increased by

the Countryside and Rights of Way Act 2000 (“the 2000 Act”) which, by section 75 and Schedule 9,

inserted new sections 28A-28R into the 1981 Act. For example, development of designated land now

requires the consent of the NRW (section 28E); although, if an owner is refused consent, he may

appeal to the Welsh Ministers (section 28F). Importantly for this claim, in exercising any of their

functions, the Welsh Ministers have a duty, set out in Section 28G(2), to take reasonable steps to

further the conservation and enhancement of the features (such as flora or fauna) which have led to

the designation.

The Gwent Levels SSSIs, through which the new section of M4 to the south of Newport would pass,

comprise a network of interconnecting watercourses comprising primary and secondary reens and

smaller field ditches, all of which act as wet fences enclosing fields of grazing marsh. Water levels in

the reens and associated field ditches are controlled by sluices and other mechanical/physical means

for agricultural and water storage purposes during summer and winter.

The levels are designated as SSSI for the aquatic invertebrate interest in the reens and the presence

of Shrill cader bee. The invertebrate interest is dependent on the aquatic macrophtye habitat within

the reens which in turn is dependent on water quality. The cleaning out of the reens is the

responsibility of the former Internal Drainage Board which is now part of NRW under the Land

Drainage Act, on a seven year maintenance cycle. Mowing of the banks is undertaken biannually

with one bank cleared one year, the other bank the following year.

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Maintenance of the grazing marsh and the field ditches is the responsibility of the riparian land

owner/farmer. For the most part, little maintenance is undertaken by riparian owners such that the

smaller watercourses are often in a poor state.

Whilst the new highway across the Levels would sever field ditches and fields of grazing marsh,

culverts incorporated into the highway design would convey flows within the existing reens under the

new motorway and maintain the primary connectivity within the Levels. Additional watercourses

would be constructed to provide further connectivity between truncated reens and field ditches to

enable water levels across the Levels affected to continue to be managed throughout the year. This

design thus enables truncated areas of grazing marsh to continue to function as such, provided they

remain viable (in respect of size and access) and are not adversely affected by construction activities

(e.g. soil compaction leading to waterlogging).

Given the current maintenance regime for the Levels it is anticipated that the construction of

replacement reens and ditches incorporating a combination of translocated aquatic macrophytic

vegetation and natural colonization, together with maintaining the existing water quality in the overall

local reen network will enable replacement reens and ditches to attain SSSI quality in a relatively

short time. The grazing marshes by themselves are not the reason for the SSSI designation.

2. Engineering Design 2.1 Background to original concept design

The highway boundary fence line has been typically shown at a 3.0m offset from the toe of the

embankment or cut off ditch on highway schemes (as shown in Figure 1 below). This is not a DRMB

requirement but generally considered standard practice for highway schemes in order to provide a

safe access and working area for maintenance purposes, if required from the toe of the embankment.

On the Gwent Levels there are three main types of boundary fence solutions required. These are

presented on Figure 1 as follows:

• Cut off ditches (Figure 1a)

• Field ditches (Figure 1b)

• Reens (Figure 1c)

The current Key Stage 3 drainage design has resulted in cut off ditches as the drainage solution over

approximately 30% of the Gwent Levels, 50% to have field ditches and the remaining 20% to have

replacement reens.

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Figure 1: Typical edge of carriageway details for cut off ditch, field ditch and reen

Engineering Design Strategy

A key concern with the engineering design for the M4 Corridor around Newport (M4CaN) is that the

embankments on the Gwent Levels will be constructed on very poor, soft ground conditions, with

potential for large scale deep seated failures which would have a significant impact on the highway.

The key characteristics of these deep-seated failures are that:

I. they are likely to occur in the relatively short term, in response to changes in ‘loading’ or ‘un-loading’ of the ground;

II. the incorporation of basal ‘geo-grid’ of requisite strength within the embankment can be used to ‘reinforce’ against failure.

In terms of the planned construction works the key stages that these deep-seated failures need to be

designed for are:

I. during the period when the embankments are ‘surcharged’ (to cause ground consolidation and limit long term highway movements);

II. following removal of the ‘surcharge’ when compensatory reens/ditches are to be excavated as part of the planned works.

As well as the planned construction of compensatory reens/ditches, the design needs to consider

possible un-planned excavations adjacent to the highway. Such unplanned excavations at any time in

the future could potentially trigger ‘deep-seated’ slope failures.

Drainage Design Strategy

The drainage strategy and reen mitigation strategy over the Levels has two functions. The first is to

ensure that where reens and field ditches are severed by the new section of M4, these are replaced

(a)

(b)

(c)

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to maintain hydraulic continuity within the existing drainage network. This is to ensure that all the

existing reens and ditches can respond to the water level management strategy being implemented

within the Gwent Levels, i.e. high penning levels in summer to support agriculture and lower penning

within the winter to increase storage.

The new reens and ditches will also assist with managing flood risk to the north of the new section of

motorway. Such reens and ditches will collect water which accumulates on land to the north and

direct flows towards a number of the culverts to be built through the motorway embankment as part of

the highway design.

The current proposals represent the extent of the infrastructure required to maintain hydraulic

continuity within the existing drainage systems. These are currently being tested within a 1D/2D

hydraulic model to determine whether there is sufficient conveyance within the systems to mitigate the

impacts of a loss of flood plain conveyance.

Land Requirements Strategy

The proposed CPO requirements are also presented for the different solutions on Figure 1. The cut

off ditches are required to be in Title as they form part of the highway drainage network. The field

ditches and replacement reens form part of the Levels mitigation and will therefore be included in the

Compulsory Purchase Order (CPO) as Essential Mitigation, which will be acquired under Welsh

Government Title. As with the field ditches, the reens will be under Welsh Government ownership and

therefore, they will be legally protected from landowners inadvertently disrupting the essential

drainage system (for example filling in the ditches). The intention is for NRW to maintain the reens

and field ditches. It is not possible to obtain Easements for a third party through the CPO process. A

section 250 right (Easement) will be provided to allow for the maintenance of the reens and field

ditches by the Welsh Government as it is essential to the scheme that these drainage measures are

maintained in the event that NRW do not maintain them or cannot arrange their own access. The

easement will also provide access to Culvert headwalls and other drainage assets.

2.2 Consideration of alternative fence line offsets

The following sections discuss the implications on the engineering design of reducing the boundary

fence line offset for each drainage solution. Note field ditches/ replacement reens are considered

similar and therefore, discussed together.

Cut off Ditches

For cut off ditches (as with field ditches/ replacement reens) the largest project risk, in relation to

engineering design, is the potential for failures in the embankment due to unplanned excavation

outside the boundary fence. Based on preliminary geotechnical assessment, an embankment height

of 3.5m and an unplanned excavation immediately outside the boundary fence would result in a factor

of safety of 1.1 for a 3.0m offset and reduces to 0.9 for a 1.0m offset. On this basis it recommended

that the minimum offset of the boundary fence line from the toe of the embankment is at least 3.0m in

order to prevent unplanned excavation and potential deep seated failure as a result. An alternative

could be to move the fence line to 1.0m and design the embankment for unplanned excavation.

However, this would result in additional reinforcement of the highway embankment and increase costs

to the project.

It should also be noted that if there are any variations during detailed design which result in realigning

the embankment out from its current position, then a small retaining wall may be required at the toe of

the embankment to remain within the fence line. An example of this would be if locations of gantries

are moved or additional local infrastructure is required which results in widening the verge locally.

Field Ditches/ Replacement Reens

For the field ditches/ replacement reens the main engineering risk is if the fence line is moved from

3.0m to 1.0m then the field ditches/ replacement reens are closer to the embankment and will impact

the embankment stability. Based on preliminary geotechnical assessment, a typical increase of 50%

tensile strength in basal geogrid is required to mitigate this. This will increase costs to the project.

File Note

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Similarly to the cut off ditches there is also a risk for the potential for failures in the embankment due

to unplanned excavation outside the boundary fence. However as the land adjacent to the fence line

is also ‘title for essential mitigation’ it is owned by the WG and maintained by SWTRA/ NRW (IDB)

which means that more control is in place for unplanned excavations and this is deemed a lower risk.

3. Environmental Aspects 3.1 Background It should be noted that in reality it is unlikely that the current SSSI boundaries will be redrawn if and

when the new section of motorway across the SSSIs is built. Based on developments, including

highways elsewhere in Wales within SSSIs it is most likely that all of the footprint of the new section of

motorway will remain within the designated area.

Of greater concern is the perception by the regulator, non-statutory environmental organisations and

the general public, of the loss of SSSI land and loss of SSSI functionality due to the footprint of the

new road. The footprint is defined as the area enclosed by the highway boundary fence and any

obviously associated highway infrastructure outside of the highway boundary fence line (e.g. water

treatment areas). Loss of SSSI functionality is defined as a measure of the loss of, or reduction in,

the reasons for the site being designated as a SSSI.

In accordance with Section 28G of the Wildlife and Countryside Act 1981 (as amended) the Welsh

Government is under a duty to take reasonable steps to further the conservation and enhancement of

the features (such as flora or fauna) which have led to the designation. One aspect of that duty is to

minimise the loss of SSSI land.


Cut off Ditches

Cut off ditches are an essential part of the highway drainage system and therefore all land that is

required to construct, operate and maintain them will be within Welsh Government ownership (by

Title).

From a PLI and environmental perspective having the highway boundary fence 3.0m from the outer

edge of the cut off ditch is excessive. Clearly the cut off ditch itself must be within the fence line but

having the highway boundary fence 3.0m from the outer edge of the cut off ditch does not

demonstrate adherence to Section 28G and the minimization of loss of SSSI land.

To deliver a minimal loss of SSSI land, the highway boundary fence could be located only 1.0m from

the outer edge of the cut off ditch. This would reduce the width of SSSI land lost by 2.0m on either

side of the motorway (4.0m in total) which would equate to an overall reduction of affected SSSI land

by approximately 3.72ha across the scheme.

Reducing the offset below 1.0m, or even placing the fence line at the top of the embankment, would

not be practical. Across the Levels the land is used to graze livestock (cattle) as stock would be able

to graze on the highway embankments.

In the scenario described above, the land in Welsh Government ownership would remain as shown in

Figure 1 above. The embankments would be laid to flower rich grassland for the benefit of the shrill

cader bee and the 2.0m beyond the highway boundary fence would remain as grazing marsh, but in

the ownership of Welsh Government.


A similar philosophy to that described above for cut off ditches could be adopted for field ditches and

replacement reens for the same reason whereby, in both cases, the highway fence line could be

located 1.0m from the toe of the embankment.

In both cases, moving the fence line would provide an opportunity to reduce the essential mitigation

land between the fence line and the watercourse. The taking of that area, it could be argued, would

File Note

Page 6 of 9

result in a direct loss of SSSI land and functionality as from a grazing/land management point of view

it is isolated from the main part of the SSSI by a watercourse designed as a wet fence. Consideration

should therefore be given to removing or reducing the essential mitigation land requirement between

the highway boundary fence and a field ditch of replacement reen.

Taking land for essential mitigation and/or Section 250 rights on the far side of the field ditch or

replacement reen should not result in a loss of SSSI land or functionality.

4. Safe by design 4.1 Background

The 3.0m offset from the toe of the embankment was originally considered to provide a safe working

area for maintenance of the embankment and fences. In addition, SWTRA have stated that a 3.0m

offset provides an area essential for safe access and maintenance operations (refer to Attachment 1

for email from Kevin Price dated 1st July 2015). Therefore, reducing the offset from 3.0m would need

to be agreed with SWTRA to ensure they can access and maintain the motorway in a safe manner.

Whilst there is potential for vehicular access along this 3.0m maintenance strip, it should be noted that

there has never been any intention to provide a surfaced track and there is no continuity of access

throughout the length.


Cut off Ditches

For this cross section the 3.0m strip is offset from the edge of the cut off ditch as the ditch is

considered a hazard itself and if vehicular access is required along the maintenance strip, clearance

from the ditch would be essential.

Consideration has been given to utilising a filter drain instead of a cut off ditch to capture surface

water run-off from the road embankment. This could reduce the overall footprint of the motorway,

however utilising a filter drain would be problematic in that pipework would have a shallow gradient

and would be likely impacted by the overall settlement of the embankment. The pipe would be

difficult to maintain and would be highly susceptible to siltation and blockage. At ground level, without

regular maintenance, the surface of the filter material would became blocked and embankment run-off

would ‘jump’ the drain, resulting in highway runoff entering third party land.

Whilst there are obvious benefits (reduced land take) to utilising a filter drain, there would be

serviceability issues and maintaining functionality of the filter drain would be difficult as discussed

above.

A 3.0m strip is deemed necessary for maintenance purposes however, if vehicular access could be

provided outside the fence line, then the fence line could be moved to 1.0m from the cut off ditch.

However, this would result in the fence being required to be temporarily removed when access is

required and it is likely that the fence line would be required to be mammal proof meaning this would

not be a simple exercise. However, it should be noted that during early discussions with SWTRA they

stated that general inspections and maintenance of the embankment slope is typically undertaken

from the verge and man access is feasible down the slope if necessary (as the slope is 1:2).

Maintenance that is required from the toe of the embankment slope (e.g to maintain the fence) is rare

and likely to be due to unusual circumstances and therefore on this basis it is deemed reasonable to

remove the fence to gain access in these circumstances.


As per the cut off ditches, a 3.0m strip is deemed necessary for maintenance purposes however, as

suggested above if vehicular access could be provided outside the fence line then the fence line could

be moved to 1.0m and the field ditches/ replacement reens remain in the same position to provide the

minimum offset for stability reasons as discussed in Section 2 and provide maintenance access.

However, this would result in the fence being removed when access is required

File Note

Page 7 of 9

Note the above approach is likely to result in additional costs to the maintenance regime and it also

would need to be agreed with SWTRA. This alternative is only feasible as the land within the field

ditches/ replacement reens are ‘title for essential mitigation’ and therefore, owned by the WG and

therefore, there is more control over unplanned excavations as discussion in Section 2.

5. Construction The location of the permanent fence line does not have any implications on the construction of the

scheme.

6. Recommendations The recommendations for the offset for the fence line for the cut off ditches, field ditches and

replacement reens are discussed in the following sections.

Cut off Ditches

Based on the above, it is recommended that for cut off ditches the fence line remains a minimum of

1.0m from the cut off ditch and easement is provided for maintenance access outside of this fence

line. This is shown in Figure 2 below.

Figure 2: Revised typical edge of carriageway details for cut off ditch, field ditch and reen with

fenceline 1.0m from toe of embankment


File Note

Page 8 of 9

Due to the CPO requirements for ‘essential mitigation’ then as long as the field ditches/ replacement

reens are a minimum of 4.0m from the embankment (for stability purposes) the location of the

highway boundary fence is not relevant and could be located anywhere within the CPO area (See

Figure 2).

File Note

Page 9 of 9

Attachment 1 – Email from Kevin Price (SWTRA) dated 1st

July 2015

From: Price, Kevin (ES&T - Transport) [mailto:[email protected]] Sent: 01 July 2015 09:24 To: Kambiz Ayoubkhani; David Leak Cc: 'David Chan'; 'Geraint Phillips' Subject: RE: M4 CaN SWTRA Drainage

Kambiz, Following our meeting earlier in the month regarding the above I have now received some feedback from SWTRA’s area staff and their various maintenance contractors and others with ‘sharp end’ experience of dealing with the maintenance aspects of motorway drainage systems. It will take me a day or so to collate and tidy up their information to formalise it to you with further details. But in outline they agreed with the points I put forward at the time in our meeting:-

The 3m access strip is seen as being essential for safe access and maintenance operations, ideally it should be capable of taking light vehicles.

Self propelled or remote control mowers are the likely method of grass cutting in the channels rather than strimming, hence access requirements for machinery off the network.

Pull in areas to avoid VRS temporary dismantling for plant access Hardening the area under the VRS will eliminate ‘strimming operations Methods to eliminate the potential for ‘grass kerb’ build up will be essential due to

virtually non existent longitudinal falls and flow ‘concentration’ areas in the verge. Any proposals that result in the reduced need for TM provision or running lane

removal for maintenance activities will be essential The liner system in the grass lined channels will need to be adequately covered with

fill to protect it from future maintenance clearance works Outfall areas will have to be hardened or paved Space needs to be incorporated into the proposals to deal with clearance arisings

from maintenance activities to drainage systems Ultimately safety, costs and network availability disturbance can all be massively

benefitted if these measures are incorporated into the proposals now! In terms of formally reporting back this information I’m not sure if this should be sent via yourself or Huw or Kyla, can you confirm please? Detailed info to follow when available and via the formal route that you request and the necessary email info. Regards Kevin

Kevin Price

Uwch Beiriannydd - Draenio Daeardechnegol - Senior Engineer - Drainage and Geotechnical Is-adran Rheoli'r Rhwydwaith - Network Management Division

Trafnidiaeth - Transport

Adran yr Economi, Gwyddoniaeth a Thrafnidiaeth - Department for Economy, Science and Transport Llywodraeth Cymru - Welsh Government

Ffon - Tel 0300 025 3067 e-bost - e-mail: [email protected] [email protected]

-----------------------------------------------------------------------------------------------------------

mailto:[email protected]






Appendix D

Levels Drainage Design File Note

File Note

M4CAN-DJV-HDG-ZG_GEN-FN-CD-0004

Page 1 of 4

Project title M4 Corridor around Newport Job number

M4CaN

cc Kambiz Ayoubkhani File reference

Projectwise\M4CaN\DJV\

Prepared by Huw Richards

David Leak

Date

1 July 2015

Subject i

Levels Drainage Design Options Assessment

1 Introduction

The purpose of this note is to examine the different drainage design options with respect to

maintenance. The areas which are considered were the focus of a meeting with SWTRA held on 1st

June 2015.

The area under consideration is the edge of carriageway drainage options. It will focus on the

maintenance, construction and health and safety aspects of the drainage design.

It should be noted that the drainage design in the Gwent Levels area is particularly challenging due to the environmentally sensitive nature of the Site of Special Scientific Interest (SSSI) and the virtually flat nature of the existing ground.

2 Channel Options Assessment

The current proposed design for the edge of carriageway drainage is a grass lined channel. This was originally proposed during Key Stage 2 and has been adopted for development into Key Stage 3. The reason for grass lined channels being chosen is that:

• They allow conveyance of water at very low longitudinal gradients, allowing a reduction in earthworks height

• They reduce the need for pipework in areas where we need to utilise very low pipe gradients and the ground is liable to consolidation settlements from the proposed earthworks.

In the light of comments made by SWTRA at the meeting, we have reviewed our proposals and looked at other options that could be used which may reduce the maintenance burden of the carriageway drainage.

2.1 Option 1 – Grass lined Channel

The current design for the highway drainage is a grass lined channel. This would be a maximum of 0.75m depth and 3m width with a 0.6m base width and 1 in 1.5 side slopes. The channel would be lined with a geosynthetic clay liner in order to provide a seal to avoid contaminated run-off from being lost from the system.

File Note

M4CaN 1 July 2015


Page 2 of 4Arup | F0.15

2.1.1 Advantages

• Grass lined channels are traditionally used in areas where the longitudinal gradient is very low as they can utilise the head of water to provide velocity to convey water to an outfall.

• They are efficient at removing sediments and pollutants from water due to the slow nature of the flow. However our research indicates that there are currently no analytical methods of quantifying these benefits. We have currently not accounted for these advantages within the sizing of the reed bed areas within the Water Treatment Areas.

• They provide a landscape advantage as they reduce the visual impact of a hardened highway.

• They form part of the Sustainable Drainage System (SuDS) which are encouraged as part of new developments.

• The grass lined channels on the project can be designed to provide capacity for a 1 in 100 year storm return period event with 30% for climate change. This minimises the risk of channels overtopping into the compensatory reens which run along the toe of the embankment.

• The channels mitigate the need for a kerb and gully drainage system and can therefore reduce the maintenance requirements. This however would need to be offset against the additional maintenance required to cut the grass in the swale.

2.1.2 Disadvantages

• The use of grass lined channels provides large areas of grass which need to be maintained in order to retain the hydraulic performance. DMRB HA119/06 recommends that the grass is cut three times a year in order to maintain a typical height of 75mm. The methods for trimming the grass to be used by SWTRA have not been finalised, but could comprise either hand strimmers or remote control cutters.

• Debris can also build up in the channel and impact conveyance. This will need to be removed without impacting on the geosynthetic liner underneath. A recognition layer underneath could provide indication of the geosynthetic liner before impact.

• Removal of debris and silts will impact on the grass lining to the invert of the channel.

• Localised differential settlement could result in areas of ponding softening the invert and potentially inhibiting the development of a good grass cover to the invert

2.2 Option 2 – Concrete Channel

A linear extruded concrete channel could be used along the length. This could be of a reduced width compared to the grass lined channel and would be of a similar depth.

2.2.1 Advantages

• This option would not require the cutting of grass, reducing maintenance.

• The risk of penetration of the geosynthetic clay liner during de-silting operations would be removed.

File Note

M4CaN 1 July 2015



• It would also be able to convey the 1 in 100 year + CC flows, similar to the grass lined channels.

2.2.2 Disadvantages

• A concrete channel would not provide any of the pollution and sediment trapping

advantages.

• The channel base would silt up, requiring regular maintenance. The frequency of de-silting

would be similar to the grass lined channel.

• Due to the high level of settlement expected across the Gwent Levels, the concrete channel

would also be prone to settlement damage. This could be mitigated by utilising pre-cast

channel units with flexible joints. It can be expected that a geo synthetic liner would also

be required to ensure water does not leak from the channel.

• The concrete channel would have an adverse visual impact on the overall appearance.

2.3 Option 3 - Stone lined Channel

This would be a channel of the same profile as the grass lined ditch, but would be lined with a 10-20mm graded rock aggregate to 300mm below the ground level.

2.3.1 Advantages

• This option has the same hydraulic performance as the grass lined channel.

• No requirement for grass-cutting.

• The channel would be resilient to the effects of localised differential settlement..

• The channel will be more robust than a grass channel. Removal of silts and debris from the channel will be a simple operation. There is unlikely to be an impact to the integrity of the invert of the channel and the geosynthetic liner.

• In low flow situations, flows can percolate through the filter material without causing visible pooling, unlike the grass lined channel.

2.3.2 Disadvantages

• Potential adverse visual impact, although this will be offset by retaining a grass verge below the safety barrier.

• Channel does not have the same pollution trapping capabilities as a grass channel.

• We are unaware of this type of solution being used in this situation and therefore no case studies or guidance can be used.

File Note

M4CaN 1 July 2015



• There is a risk from stone scatter from the ditch reaching the highway. However as the ditch is located behind the safety barrier this risk is considered to be low.

• Although this option would not require the cutting of grass, appropriate methods of weed suppression will be required. The use of weed killers may be problematic within the SSSI.

3 Summary

Either a grass or stone lined channels can be used on this project. Each option has both advantages and disadvantages. These are summarised below:

Grass lined Channel

• The grass channel has the advantage of being able to remove sediments and pollutants from highway runoff. However to date our research has not found any analytical methods of quantifying these benefits. Here it is noted that shoaling and ponding could reduce grass cover within the invert reducing its environmental benefits.

• This channel is less visually intrusive but is more maintenance intensive.

Stone lined Channel

• Less maintenance due to the avoidance of grass cutting and is a more robust construction than grass lined channel.

• The stone lined channel will impact on the visual appearance of the scheme and it does not have the same environmental benefits.

It is important for the scheme to minimise any adverse effect on the environment. As a consequence the grass lined channel is the preferred solution. It has pollution control and environmental benefits and is less visually intrusive.



Name Huw Richards Huw Richards Kyla Nunn




Appendix E

Gradient of Mainline East of Castleton File Note

File Note

Page 1

Project title M4 Corridor around Newport

cc File reference

M4CaN-DJV-HML-Z1_GEN-FN-CH-0001

Prepared by AK Date

11/05/2015

Subject Gradient of Proposed New Section of Motorway east of Castleton



Name Author AK Checked SH Approved

Design decision relating to gradient east of Castleton and associated Climbing Lane

This File Note has been prepared to document the design decisions around the 3% / 4% gradient to the east of Castleton Interchange between Chainages 3+700 and 5+000. The KS2 specimen design issued as part of the tender information included a 3% gradient in this area which is in line with TD9/93 of the DMRB which states

4.1 Maximum Gradients: The desirable gradient for design shall be:

Motorways 3%

AP Dual Carriageways 4%

AP Single Carriageways 6%

However, in hilly terrain steeper gradients will frequently be required, particularly where

traffic volumes are at the lower end of the range.

Further on in TD9/93 it states

4.2 Effects of Steep Gradients: In hilly terrain the adoption of gradients steeper than Desirable

Maximum could make significant savings in construction or environmental costs, but would also

result in higher user costs, ie by delays, fuel and accidents. Whilst on motorways the disbenefits

associated with the consequently high traffic volumes indicate that 4% should normally be

regarded as the Absolute Maximum, on all purpose roads an economic assessment of the effects

File Note



Page 2

of adopting a steeper gradient should be carried out to determine the economic trade-off

between construction/environmental cost savings and disbenefits to traffic…

During tender, it was therefore decided to take advantage of section 4.2 and increase the gradient in this location to 4%. The effect of this change was to reduce the fill volume by 230,000m3, reducing the maximum embankment height from 17m to 11m and reducing the footprint through the woodland affected by the alignment. TD9/93 also sets out details where Climbing Lanes should be considered

5.8 Definitions: For the purposes of this document, a climbing lane is defined as an

additional lane added to a single or dual carriageway in order to improve capacity

and/or safety because of the presence of the steep gradient.

5.9 On single carriageways, a climbing lane can be considered if it can be justified (see

paras 5.11 to 5.27) on hills with gradients greater than 2% and longer than 500m.

5.10 On dual carriageways, gradients of 3% over a distance of 500m would be expected to

be the minimum that would justify an additional lane.

The document then goes on, in Chapter 5, to describe the process of carrying out an economic assessment to provide justification for provision of a climbing lane where significant safety or environmental benefits are likely to be achieved. It is anticipated that the highest benefits will be realised for single lane roads where an additional lane provides critical overtaking opportunities at locations where slow moving vehicles are likely. Benefits are also sometimes significant on dual carriageways where high HGV flows can result in slow moving traffic in both lanes. It is generally more difficult, however, to generate enough benefit to justify an additional lane on a three lane motorway where HGVs are already restricted from Lane 3. The fact that the M4CaN is proposed as a D3M with the anticipated traffic flows relatively low for a road of this standard and percentage HGVs on this section not excessive, it has been assessed that the cost and environmental impact of introducing a climbing lane over the length of the 4% gradient would far outweigh any safety or economic benefits achieved. A table showing the results of a qualitative assessment of the Welsh Impact Areas into the provision of a climbing lane compared to the baseline of not providing a climbing lane is included on the next page. It has therefore been concluded that a climbing lane will not be incorporated into the design in this location.

File Note



Page 3

Qualitative Assessment of Welsh Impact Areas

Appraisal Criteria No Climbing Lane

(Baseline) Climbing Lane

Economy

Transport Economic Efficiency (Cost/Benefit)

0 -1

EALI (wider economics) 0 1

Environment

Noise 0 -1

Local Air Quality 0 -1

Greenhouse Gas Emissions 0 0

Landscape and Townscape 0 -1

Bio-diversity 0 -1

Heritage 0 -1

Water Environment 0 -1

Soils 0 -1

Society

Transport Safety 0 1

Personal Safety 0 0

Physical Fitness 0 0

Social Inclusion 0 0

Equality, Diversity and Human Rights

0 0

Total assessment Score 0 -6

Key +3 Major benefit +2 Moderate benefit +1 Minor benefit

0 Neutral -1 Minor disbenefit -2 Moderate disbenefit -3 Major disbenefit

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