A465 Heads of the Valleys Dualling Sections 5 and 6: Dowlais Top to Hirwaun PROOF OF EVIDENCE: Highways Engineering Document WG 1.3.

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1 A465 Heads of the Valleys Dualling Sections 5 and 6: Dowlais Top to Hirwaun PROOF OF EVIDENCE: Highways Engineering Document WG By Jonathan Thirkettle March 2018

2 PROOF OF EVIDENCE: Highways Engineering CONTENTS Page No. 1 Personal Statement Scope and Proof of Evidence Existing Conditions Development of the Scheme Proposed Scheme Differences from the made Line Order Conclusions Declaration... 45

3 1 Personal Statement 1.1 My name is Jonathan Thirkettle. 1.2 I have 34 years experience in the design, procurement and construction supervision of civil engineering works. I specialise in the design of highway schemes. My recent experience includes delivering the designs for the M4 widening north of Cardiff, A470 Cwmbach to Newbridge-on-Wye, M4 J32 and J33 pinch point schemes and, Second Forth Crossing approach infrastructure. 1.3 I am currently a Consultant at the Cardiff office of Jacobs UK Ltd and I am responsible for advising and directing multi-disciplinary design teams on a variety of major highway schemes. I am also the Technical Excellence lead for Jacobs in Wales and provide advice and support to colleagues in other offices throughout the UK. 1.4 Albeit not continuously, I have been involved with the development of the preferred route of the A465 Heads of the Valleys Scheme since In September 2015 I was appointed as the Highways Design Team Leader for the development of the A465 Heads of the Valleys Dualling Section 5 and 6 Dowlais Top to Hirwaun. I have led the development of the Scheme through this period to publication of draft Orders in July I am responsible for managing and coordinating the engineering design teams involved in the project, namely: highway geometry and alignment. I have worked with my colleague, Wendy Bateman, the Environmental Coordinator, to ensure coordination between the engineering design and environmental disciplines. 1.5 In preparing the draft Orders design I have been supported by my team of engineers. They have worked to my instruction and I adopt their work as my own. The evidence which I have prepared and provide in this Proof of Evidence is true and I confirm that the opinions expressed are my true and professional opinions. Jonathan Thirkettle/ March of 45

4 2 Scope and Proof of Evidence 2.1 My evidence will address the engineering design aspects for the Scheme: The Heads of the Valleys Dualling Section 5 and 6 Dowlais Top to Hirwaun (hereafter referred to as the Scheme). 2.2 The objective of this evidence is to demonstrate that due regard has been taken of the physical characteristics and constraints imposed by the topography and local features and that the proposed alignment accords with the relevant standards and meets the objectives of the proposed dualling. 2.3 My evidence is presented in the following structure: 1. Personal Statement; 2. Scope of Proof of Evidence; 3. Existing Conditions; 4. Development of the Scheme; 5. Proposed Scheme; 6. Differences from the made Line Order 1999; 7. Conclusions; and, 8. Appendices. Jonathan Thirkettle/ March of 45

5 3 Existing Conditions Existing Road 3.1 The overall form and extents of the existing road are described briefly by Mark Dixon in his proof of evidence (WG 1.1). A more extensive description can be found in the Environmental Statement (ES) (DD 1.7.1). 3.2 Highway improvements were made to the A465 in the 1960s, straightening out the route and widening the then two lane single carriageway to its current three lane configuration. Generally, the road now has two lanes in the uphill direction and one lane downhill. 3.3 This section of the A465 contains fourteen at-grade junctions of which four are roundabouts and the remainder are T-junctions or staggered crossroads. 3.4 Existing constraints on this section of the A465 are listed by Mark Dixon and my colleague David Sallis in their proofs of evidence (WG 1.1 and 1.2.1). 3.5 At its westerly extent, the proposed Scheme would tie in to the existing A km west of the current Hirwaun roundabout. To the east, the proposed Scheme ties into the existing A km west of the Rhymney grade-separated junction constructed as part of Section 4 of the wider A465 dualling Scheme. Existing Drainage 3.6 The existing A465 road between Dowlais Top and Hirwaun is drained using a kerb and gully closed drainage system. 3.7 There is no infrastructure for pollution control, spillage containment or attenuation of discharges to watercourses. Jonathan Thirkettle/ March of 45

6 Existing Lighting 3.8 The existing lighting on the A465 consists of high pressure sodium lamps and is generally provided only at junctions and roundabouts. 3.9 The lamps provide full lighting at all times from dusk until dawn, expending electricity unnecessarily during quiet hours of the night when traffic flow is low. Existing Structures 3.10 Existing structures have been described by David Sallis in his proof of evidence (WG 1.2.1). Existing Geological Conditions 3.11 Existing geological conditions have been described by David Sallis in his proof of evidence (WG 1.2.1). Existing Environmental Conditions 3.12 My colleague Wendy Bateman will present a separate proof of evidence for the environment (WG 1.7.1). Existing Traffic Conditions 3.13 My colleague Dudley Morell will present a separate proof of evidence for traffic (WG 1.4.1). Jonathan Thirkettle/ March of 45

7 4 Development of the Scheme Overview 4.1 The development of the Scheme from route selection through to publication of the made Line Order 1999 is described by Mark Dixon in his proof of evidence (WG 1.1). 4.2 The Scheme draft Orders proposals are a development of the made Line Order 1999 (DD 2.1.1). 4.3 The Scheme proposals follow the principles and junction strategy of the made Line Order 1999 (DD 2.1.1). 4.4 A supplement to the draft Side Road Order and Compulsory Purchase Order was published by the Welsh Government on March 7th 2018 as described by Mark Dixon in his evidence (WG 1.1). Design options Considered 4.5 Highway design options considered during the period between the publication of the made Line Order 1999 (DD ) and the July 2017 draft Amendment Line Order proposals are described in the Design Options Report (DD 6.2.4). 4.6 I will outline in my evidence any changes that have been made to the highway engineering aspects of the Scheme that result in differences to those presented in the made Line Order In summary, the principal areas of change are: A) Slight relocation of the Hirwaun roundabout due to the presence of an existing gas main; B) Provision of a new full movement grade separated junction at Croesbychan; Jonathan Thirkettle/ March of 45

8 C) Introduction of a split alignment at Nant Hir; D) Updated junction layout at Baverstock; E) Removal of climbing lane westbound between the A470 merge slip road and the Baverstock junction diverge slip road. F) Removal of split junction at Gurnos; G) Provision of a new full movement grade separated junction at Prince Charles Hospital, Gurnos; H) Updated slip road provision at Dowlais; and, I) Additional NMU provision throughout the Scheme. Scheme Consultation 4.8 Mark Dixon has presented the Scheme consultation history as part of his proof of evidence (WG 1.1). Safe by Design 4.9 The Construction (Design and Management) Regulations 2015 (DD ) have been followed during the development of the Scheme Hazard risk registers have been prepared which document where hazards have been avoided and risks reduced as well as identifying residual risks. Additionally, a CDM Design Gateway Statement has been produced summarising key risks and outstanding issues that need to be addressed. Jonathan Thirkettle/ March of 45

9 5 Proposed Scheme Scheme Overview Summary 5.1 The proposed Scheme comprises of approximately 17.7km of primarily on-line dualling. Proposals allow for the upgrading of the existing three-lane single carriageway to rural all-purpose dual carriageway (D2AP) standard. There would be a section of off-line construction west of Hirwaun (approximately 1.4km) and a short section (approximately 0.8km) immediately east of Taf Fechan. 5.2 General arrangement drawings of the Scheme are included in Appendix (DD ). Junctions 5.3 The Scheme includes six full movement grade separated junctions, as follows (from west to east): A) Hirwaun; B) Croesbychan; C) Baverstock; D) A470; E) Prince Charles Hospital; and, F) Dowlais Top. Jonathan Thirkettle/ March of 45

10 Detrunking 5.4 As a result of the proposed Scheme, the following areas of the existing A465 trunk road have been identified as having the potential for reclassification. Under such a scenario, it is likely that ownership of these assets would be transferred from the Welsh Government to the local authorities (i.e. detrunked) covered as follows: A) A465 trunk road from the existing Rhigos Road roundabout to Hirwaun Road/Brecon Road roundabout: a 1km length of trunk road crossed by five structures. Continued access between the two existing roundabouts is required post-scheme to provide local homeowners and businesses with access in and around Hirwaun; B) A465 Nant Melyn viaduct structure: a new structure is proposed to the south of the existing bridge. The existing A465 structure is proposed to be used as part of a nonmotorised user (NMU) provision; and, C) A section of the existing A465 east of the Taf Fechan viaduct is to be replaced by the proposed A465 to the south. It is proposed to remove the existing road at this location. Design Speeds 5.5 The main line design speed of the Scheme has been selected in accordance with the requirement of DMRB (Design Manual for Roads and Bridges) TD 9/93 (UK DMRB 6.1.1) (Incorporating Amendment No. 1) Highway Link Design (DD ). A design speed of 120B kph, which is applicable to dual carriageways subject to the national speed limit of 70mph, has been applied for the full length of the Scheme. Jonathan Thirkettle/ March of 45

11 5.6 In common with the other sections of the A465 adjoining Section 5 and 6, the Scheme would be signed at the national speed limit. 5.7 The design speeds for connector roads, which encompass all interchange links, slip roads, link roads and dumb-bell link roads, have been assessed in accordance with DMRB TD 22/06 (UK DMRB 6.2.1) Layout of Grade Separated Junctions (DD ) and can be summarised thus: A) Interchange link roads 85 kph (50 mph); B) Slip Roads 70 kph (40 mph); C) Link Roads 120 kph or 100A kph (70 mph or 60mph); and, D) Dumb-Bell Link Road 70 kph (40 mph). Cross-Sections 5.8 The main line highway cross section would be a rural all-purpose dual 2-lane carriageway (D2AP) in accordance with Figure 4-3a, DMRB TD 27/05 (UK DMRB 6.1.2) Cross Sections and Headrooms (DD ). On curved alignments and approaches to junctions verge and central median widening is proposed where it is necessary to achieve the appropriate visibility and Stopping Sight Distance (SSD) requirements. Highway Geometry 5.9 Due to the online nature of the Scheme and the constraints imposed, I have sought to challenge design standards in order to mitigate the impact of the proposed design on the natural and built environment. Jonathan Thirkettle/ March of 45

12 5.10 In light of the constraints imposed, in general the highway alignment design rationale applies a permissible reduction in geometrical standards throughout the full length of the Scheme. This strategy has been adopted in order to provide consistency for the road user and to ensure clarity of driver perception Aside from a general relaxation in geometrical standards, Departures from Standards (DfS) have also been identified. These are currently being considered by Welsh Government via the informal application process The general design rationale can be summarised thus: A) Horizontal radius where below the desirable minimum, cross-sectional widening provided to coincide with a maximum one design step reduction in SSD.; B) Vertical radius within the vicinity and immediate approach to junctions, vertical geometry aims to be fully compliant to avoid coincidental reduction in vertical SSD.; C) Gradient - where possible <4%, in difficult circumstances 6%, in exceptional circumstances up to 8%.; and, D) SSD - for the majority of the Scheme, no more than one design speed reduction below desirable minimum, with the exception of localised pinch points A significant length of the proposed Scheme also falls within the immediate approach to a junction as defined in DMRB TD 9/93, which minimises the potential to introduce permissible Relaxations within these prohibited zones. Any such Relaxations would effectively constitute a Departure from Standard Highway geometry drawings are included in Appendix (DD ). Jonathan Thirkettle/ March of 45

13 NMU Provision 5.15 A segregated NMU path would be provided adjacent to sections of the Scheme. Refer to David Sallis evidence for further details (WG DD 1.2.1). Applicable Design Standards 5.16 The Scheme has been designed by reference to the standards as contained in the Design Manual for Roads and Bridges (DMRB) (DD 6.4.6). The following are the principal DMRB standards used in preparation of the draft Orders Scheme: A) TD 9/93 (UK DMRB 6.1.1) (Incorporating Amendment No. 1) Highway Link Design (DD ); B) TD 27/05 (UK DMRB 6.1.2) Cross Sections and Headrooms (DD ); C) TD 22/06 (UK DMRB 6.2.1) Layout of Grade Separated Junctions (DD ); D) TD 16/07 (UK DMRB 6.2.3) Geometric Design of Roundabouts (DD ); E) TD 69/07 (UK DMRB 6.3.3) The Location and Layout of Lay-bys and Rest Areas (DD ); F) TA 57/87 (UK DMRB 6.3.3) Roadside Features (DD ); and, G) TA 90/05 (UK DMRB 6.3.5) The Geometric Design of Pedestrian, Cycle and Equestrian Routes (DD ) A number of departures from DMRB highway and geometry standards are proposed that would benefit the Scheme. These departures from standards relate to the preliminary design and are currently being reviewed via the informal application process. The Jonathan Thirkettle/ March of 45

14 formal application would be carried out by the Contractor when the Scheme proposals are developed in more detail at the next stage during detailed design The alignment and Junctions Strategy report (DD 6.2.1) presents the design parameters used in the geometric design of the highway, correct at that point in the development of the design. Scheme Description Highway Alignment 5.19 The proposed alignment is described in the following thirteen sections. Table 1 - Section locations on the Scheme Section Start End Chainage (m) Chainage (m) Hirwaun Junction Hirwaun Junction to Trewaun Junction Trewaun Junction Trewaun Junction to Croesbychan Junction Croesbychan Junction Croesbychan Junction to Baverstock Junction Baverstock Junction Baverstock Junction to A A470 Junction A470 to Prince Charles Hospital Junction Prince Charles Hospital Junction Prince Charles Hospital Junction to Dowlais Top Dowlais Top Junction The commentary within each of the following sections runs from west to east in order of increasing Scheme chainage. Hirwaun Junction (Ch. 0 to Ch. 2500) 5.21 The existing Rhigos roundabout would be replaced with a grade separated junction referred to as Hirwaun Junction. The proposed roundabout would be larger than the existing and would be located Jonathan Thirkettle/ March of 45

15 approximately 50m to the south of the existing junction. It would provide links to the A4059 and the existing A465 route, which would become a local road linking the new A465 alignment to Hirwaun The road would be on embankment, approximately 10m above the existing road level at its maximum height. The new roundabout would be at a similar level to existing ground level The west facing slip roads would start to deviate from the main line at approximately Ch with the main roundabout between Ch and The east facing slip roads would link to the main line at approximately Ch Hirwaun Junction to Trewaun Junction (Ch to Ch. 3200) 5.24 From the Hirwaun junction the proposed Scheme would be routed off-line for approximately 1.4km with a section of new carriageway. The alignment would pass to the south of the recreational ground and to the south of the existing A465 between Hirwaun and Trewaun roundabout The main line from the Hirwaun Junction Underbridge would be on embankment, returning to existing ground level at Ch From this point onwards the road would be in cutting, which would be at its deepest at Trewaun (covered in the subsequent section) Access to the Tower Colliery site along Tower Road would be stopped up, with a new access provided from the Hirwaun Junction. Access to the Pen y Cymoedd Wind Farm would be maintained from the existing A465 with an overbridge to take traffic over the new alignment Provision for NMUs would be incorporated into the wind farm access bridge to reconnect footpath routes severed at Hirwaun. The National Cycle Network (NCN) Route 46, currently connecting to the A465 via an overbridge at Tower Road, would be stopped Jonathan Thirkettle/ March of 45

16 up and realigned through Hirwaun junction and Trewaun via the new realigned carriageway. Horizontal Alignment 5.28 The proposed alignment is predominantly online to the west of the proposed roundabout (i.e. follows the alignment of the existing road). However, it rises in level from approx. Ch to provide a full movement grade separated junction at Hirwaun. East of Hirwaun junction, the alignment diverts to the south of the existing A465, skirts the southern perimeter of playing fields on a 720m left-hand radius curve and re-joins the alignment of the existing A465 at Trewaun The proposed 720m radius constitutes a relaxation of one design speed step but is required to avoid impact on Hirwaun Recreational Grounds to the north and special areas of interest to the south Two new underbridges are proposed at Hirwaun junction to accommodate the roundabout gyratory, parts of which would pass underneath the main line. The proposed gyratory is offset southeast from the existing gyratory to align with the shift of the main line and to avoid a high pressure gas main located at Ch The junction slip roads have been optimised to minimise land take requirements but remain compliant with DMRB TD 22/ Direct access on to the A465 is effectively removed. This eliminates safety issues associated with weaving, merging of traffic and visibility on approach to and surrounding the junction based on a 720 m left hand curve Two new overbridges are proposed at Trewaun to retain connectivity between both the existing A465 and Brecon Road with Aberdare. The side roads would be at existing carriageway level with the proposed main line below Existing Ground Level (EGL), Jonathan Thirkettle/ March of 45

17 between retaining walls. Earthworks for the main line carriageway would spread into the housing development to the north of the A465, requiring demolition of three Welsh Government owned properties at Johnson Park. This land take is also required to accommodate the proposed diversionary route required to enable construction of the A465 to take place at this location It is proposed to include a four arm roundabout offset to the southeast of the existing Trewaun junction to provide connectivity between the side roads. It includes a private access for a residential property situated to the south of the junction. Its footprint and resulting perpendicular alignment of the north-eastern overbridge creates open space in front of residential properties and facilitates future maintenance requirements. Vertical Alignment 5.34 Vertical curvature throughout Hirwaun and Trewaun is fully compliant with DMRB TD9/ To provide a full movement grade-separated junction at Hirwaun the main line is raised above EGL by approximately 10m. East of the junction, desirable minimum curvatures are employed to replicate the existing levels at Nant y bwlch, before cutting into existing ground on a 182K hog curve to facilitate the proposed wind farm access design, and for the design strategy through Trewaun. This would result in large cuttings with depths of up to approximately 11.2m, and side slopes graded back to EGL between 1:2 and 1:3. Cross Section 5.36 East of Hirwaun, on the 720m left-hand radius curve, central reserve and verge widening is proposed to provide a minimum SSD of 215m where possible. A desirable minimum cross section Jonathan Thirkettle/ March of 45

18 is provided through Trewaun to limit the potential impact on the residential areas surrounding the corridor. Side Roads 5.37 At Hirwaun, the current A465 alignment is retained for access between Rhigos and Trewaun. Remaining side roads, including private access roads, are to be realigned to the proposed junction minimising land-take and improving the safety of road users To the east of Hirwaun junction a new access road retains connectivity around the Rugby Club and playing fields. This facilitates a number of maintenance requirements, in particular access to the telephone mast situated to the west Tower Road has been stopped up to the north and south of the A465. To the south, a gravel track is proposed as a temporary measure, as per Tower Colliery comments, to maintain connectivity to the quarry and farmland To the west of Trewaun, the access track serving the Pen y Cymoedd Wind Farm is being severed by the southerly shift of the main line. A new structure and alignment for the access track have been agreed in principle with Pennant Walters Group with the aim of retaining as much of the existing alignment, access and layout as possible. Trewaun Junction (Ch to Ch 3300) 5.41 The existing Trewaun roundabout links the A465 with Brecon Road and Hirwaun Road. This link to the realigned A465 would be removed with the detrunked A465 and Brecon Road crossing above the new A465 on two bridges before linking to Hirwaun Road at a roundabout, which would be located slightly south of its current location. Jonathan Thirkettle/ March of 45

19 5.42 The proposed A465 would be in cutting at this location at a maximum depth of approximately 10.5m with localised reinforced concrete retaining walls to the north and south of the road. Trewaun Junction to Croesbychan Junction (Ch to Ch. 4450) 5.43 From Trewaun, the proposed Scheme would involve the widening of the existing carriageway for a distance of approximately 1.9 km. A new overbridge for NMUs (the Pentwyn Cynon footbridge) would be provided to link Tramway with existing footpaths along the Afon Cynon (which also form part of Route 46) towards Penywaun Two lay-bys would be provided (one eastbound and one westbound), located to the west of the Afon Cynon. Horizontal Alignment 5.45 The Scheme continues from Trewaun (Ch. 3300) to Court Lodge as an online improvement. The proposed horizontal curvature comprises a 720m left hand radius at Trewaun followed by a 1020m right hand radius, a straight across Afon Cynon and Court Farm, and a 720m left hand radius at Court Lodge. Less than desirable minimum radii are required to minimise or eliminate impact on the built environment located primarily to the north of the main line. The route follows the line of the existing carriageway as much as possible and also keeps the alignment of the structures consistent with existing. The final 720m curve facilitates the inclusion of a junction at Croesbychan. Vertical Alignment 5.46 The alignment is predominantly in cutting between Ch m and Afon Cynon Underbridge as per the design strategy for Trewaun. Several elements of retaining structures are required to reduce the corridor footprint and to avoid impact on existing infrastructure, in particular the pylon located at Ch.3500, west of the Afon Cynon. The alignment is then raised in order to meet Jonathan Thirkettle/ March of 45

20 Network Rail s clearance requirements over the Vale of Neath railway and to provide a new full movement grade separated junction at Croesbychan To achieve the design principles through this section the curvature utilised is the desirable minimum value as quoted in DMRB TD9/93. Cross Section 5.48 Immediately east of Trewaun, central reserve widening is proposed on the 1020m radius to provide a minimum of 215m SSD. Through the straight section of alignment, a desirable minimum cross section has been provided to avoid unnecessary structural widening. At Court Lodge, central reservation and verge widening is applied to provide a minimum SSD of 215m on approach to the proposed junction. Verge widening is restricted by local side road infrastructure and residential dwellings situated adjacent to Keepers Lane. Croesbychan Junction (Ch to Ch. 5550) 5.49 A new grade separated junction would replace the existing staggered junction at Croesbychan. Through this junction the A465 main line would be on embankment above the junction roundabouts, which would be arranged in a dumbbell arrangement, below the carriageway in order to minimise the visual impact of the junction on the wider landscape Access from the eastern residential areas of Hirwaun to Croesbychan junction would be provided by a side road that ties into the local road network at Swansea Road in Hirwaun close to the existing Vale of Neath rail bridge Croesbychan junction would have two roundabouts, configured in a dumb-bell arrangement. One roundabout would be located to the north of the A465 at Ch and one to the south of the A465 at Jonathan Thirkettle/ March of 45

21 Ch The southern roundabout would then link to a third roundabout located on the alignment of the existing road to Llwydcoed Crematorium Public Rights of Way (PRoWs) that cross the existing A465 at grade would be diverted through the junction with a new NMU bridge across the Vale of Neath railway being provided The centre line of the road would vary from being at the level of the existing A465 road at the railway bridge up to 10m above the existing ground level between the railway and Nant Melyn viaduct. Croesbychan Junction to Baverstock Junction (Ch to Ch. 7200) 5.54 From Croesbychan the proposed Scheme would continue to the Baverstock roundabout. The A465 alignment would be slightly south of its existing alignment as it heads east to Baverstock, with a new bridge across the Nant Melyn being constructed The road would be on embankment from Nant Melyn to the Nant Moel underbridge. The embankment would vary in height depending on the surrounding topography and would be 10.5m at its highest. From Nant Moel to Nant Hir reservoir the road would be in a 5m deep cutting from the north, and 9.5m embankment to the south. Horizontal Alignment 5.56 The proposed alignment deviates southerly from the existing A465 at approx. Ch and comprises an offline proposal to Ch It ties back in to the existing alignment from Ch to Nant Hir as an online improvement The proposed horizontal alignment comprises a 720m left hand radius curve followed by a 720 m right hand radius curve, both being one design speed step below desirable minimum, which is permitted by DMRB TD 9/93. Subsequently there would be a Jonathan Thirkettle/ March of 45

22 straight alignment on the approach to Nant Hir. At Ch the carriageways split to be carried on separate structures crossing Nant Hir Reservoir. The eastbound carriageway transitions into a relaxed horizontal radius of 720m. The westbound carriageway curvature reduces further to 680m radius, constituting a two-step Relaxation, which is required to follow the existing alignment and utilise the existing structure over the reservoir From Nant Hir, the alignment deviates from the existing line, north immediately east of Nant Hir, and to the south at Baverstock East of Nant Hir, the horizontal curvature comprises fully compliant radii on approach to and through Baverstock junction. Vertical Alignment 5.60 The vertical curvature includes several desirable minimum K values (of 182 K crest and 37 K sag) so the appropriate levels to the structure and through the junction can be achieved. This allows the side roads and east-facing slip roads to be at or below existing ground level which reduces the footprint of the main line, visual impact for nearby residents and significantly reduces the amount of design non-compliances associated with vertical curvature and SSD The alignment is predominantly at grade or on embankment throughout this section. Cross Section 5.62 Central reservation and verge widening is proposed throughout this section to ensure a minimum SSD of 215m, in particular on approach to junctions and structures where the horizontal radius employed is desirable minimum or less Cross sectional widening is restricted by local infrastructure at the junction (Keepers Lane) and to avoid unnecessary structural widening at Nant Moel and Nant Hir. Jonathan Thirkettle/ March of 45

23 Baverstock Junction (Ch to Ch. 8550) 5.64 The proposed Baverstock junction would be located approximately 610m west of the existing crossroads. The junction would take the form of a grade separated dumb-bell roundabout with two roundabouts, one to the north and one to the south of the A The existing junction with Crematorium Road from the westbound carriageway would be closed. The northern roundabout would connect to the eastbound carriageway and also provide links to the gas works, the Jah Jireh residential home and under the A465 to the southern roundabout. The southern roundabout would connect to the westbound carriageway as well as to Crematorium Road Links for pedestrians, cyclists and equestrians would be provided through the junction linking to local roads and the existing Route 46. Access would also be provided to the informal tracks that lead north from the existing Baverstock junction through the plantation past the gas works into plantations within the Brecon Beacons National Park (BBNP) Sections of rock cutting are required on both sides of Baverstock Junction between Ch and Ch The main line throughout this section has been modified in order to achieve optimal cut/ fill volumes whilst considering requirements for potential retaining structures or strengthened earthworks between the main line and slip-roads The largest section of rock cutting is on the northern side of the link-road providing connectivity to the gas-works and Jah Jireh residential home Each rock cutting lift would be 6.0m high and graded at 1:1. The final rock lift would vary in height depending upon the level of rock Jonathan Thirkettle/ March of 45

24 at that specific chainage. 2.0m berms separate each rock lift to intercept water run-off. A 2.0m berm separates the rock cutting from the 1:3 soil cutting slopes interfacing with the existing ground. Maximum required rock cutting depth is approximately 16m Rock traps have also been included within the design, with the width dependent on a number of factors, but mainly height and number of lifts of rock cut immediately adjacent to them. Baverstock Junction to A470 Junction (Ch to Ch. 9800) 5.71 From Baverstock junction the road would continue east for 3 km as an on-line widening to the A470 junction From Baverstock junction the landscape would continue to fall away. In order to accommodate this, the road would be on embankment to the north (up to 2.5m in height) and cutting to the south (up to 6.5m in depth) through to Ch Horizontal Alignment 5.73 The Scheme continues from Baverstock to the A470 primarily as an online improvement. On approach to the A470, the horizontal curvature transitions from fully compliant radii to a less than desirable minimum radius of 720m (one design speed step relaxation). This is to realign the main line to the north of the existing gyratory and existing A465 which are to be retained. This facilitates the provision of a grade-separated junction between the A470 and A465 as described below. It also allows for the most efficient crossing of the main line and eastbound merge over the Taf Fawr valley and ensures tie-in with the existing alignment ahead of High Street Overbridge. Vertical Alignment 5.74 At Ch.8650 the alignment meets EGL and transitions from a onestep relaxation constituting a departure in vertical curvature (100 K Jonathan Thirkettle/ March of 45

25 hog) on to a 6% downhill gradient to stay as close to the existing ground as possible. It transitions into a constant 4.8% downhill gradient for the crossing of the Nant Ffrwd watercourse and through to the A470 / A465 interchange. This alignment provides desirable minimum headroom at the interchange whilst also limiting the earthwork profile of the main line and height of structures on approach to the junction. Cross Section 5.75 Immediately east of Baverstock Junction, central reserve widening is proposed to ensure a minimum of 215 m SSD. This constitutes a Departure from Standard as it is within the prohibited junction zone (1.5 x SSD from back of nose). Further widening is restricted by the lack of space due to the extension of Swansea Road and the location of the access track providing connection to Tyn y Coedcae On approach to the A470 the cross section is again constrained by residential properties to the south and BBNP to the north. It is also restricted by the crossings of the Nant Ffrwd watercourse required by the main line, eastbound diverge and westbound merge. SSD is again reduced to 215m in a prohibited junction zone, constituting a departure from standard A470 Junction (Ch to Ch ) 5.77 The A470 junction would be a grade separated junction, with the A465 main line passing over the A470 on a single span bridge and with the main line being approximately 12m higher than the existing road at its highest point. The existing A470 roundabout would be realigned slightly and provide access to and from the westbound A465 carriageway. There would be a new roundabout to the north of the A465 which would provide access to the eastbound A465 carriageway. Jonathan Thirkettle/ March of 45

26 5.78 The west-facing slip roads to/from the A470 junction would connect to the A465 approximately 800 m to the west of the roundabout. The A465 would cross the Nant Ffrwd via two new bridges (for the main line and the eastbound diverge) and use of the existing Nant Ffrwd structure for the westbound merge In order to minimise the visual impact on the BBNP, within which the junction of the A465 / A470 would lie, the eastbound diverge off the A465 would be in a cutting, which would have a maximum depth of 24m The realigned A465 main line would be routed 70m north of its existing alignment at this location. Subsequently, the route of the east-facing on-slip and amendments to the existing A470 would result in the loss of land from the southernmost section of the Cefn Coed Cemetery and Jewish Burial Ground. In order to minimise the land-take from the Cefn Coed Cemetery a 130m long retaining wall would be constructed, which would have a maximum height of 10m The A465 currently crosses the Taf Fawr on a single structure, which would be retained and utilised for the westbound diverge. The main line A465 and eastbound merge would be routed across the Taf Fawr on a separate three span bridge Central reserve and verge widening is proposed on the Taf Fawr main line viaduct to provide a minimum SSD of 215m Retaining walls (typically 160m long and up to 8.5m high) would be constructed to the north and south of the A465 through Cefn Coed. Rock slopes at approximately 70 degrees would be present between High Street bridge and the new Taf Fechan bridge. Jonathan Thirkettle/ March of 45

27 A470 Junction to Prince Charles Hospital Junction (Ch to Ch ) 5.84 The existing Taff Trail footbridge would be replaced by a new 37m span over the A465 suitable for pedestrians, cyclists and equestrians The junction to Lower Vaynor Road would be closed Taf Fechan Viaduct would be symmetrically widened, with steel arches tied to the existing viaduct. This would enable future maintenance of the existing structure to take place while allowing traffic to divert around the existing structure under traffic management on the widened sections of the viaduct It is proposed to construct the viaduct from the top of the gorge with some works required to the rock faces of the gorge. However, it is not proposed to undertake any works on the viaduct from the base of the gorge due to its environmentally sensitive nature and in order to minimise potential impacts on the Cwm Taf Fechan Woodlands SSSI, Gurnos Quarry Tram road and Leat SAM A new multi-span bridge 12 m long would be provided for NMU to the south of the main carriageway to connect Lower Vaynor Road and Gurnos Road, providing safer routes for pedestrians and cyclists from Cefn-coed-y-cymmer, Prince Charles Hospital and Pen-Y-Dre High School East of Taf Fechan the proposed Scheme would involve a short off-line section (approximately 800m); due to the topography of the area a series of cuttings and embankments would be required. The deepest cutting would be 290m long and up to 16m deep A new underpass from Gurnos Road would provide access to attenuation ponds and Gurnos Farm. Jonathan Thirkettle/ March of 45

28 Horizontal Alignment 5.91 The main line utilises desirable minimum radii over the valley to tie in with the eastbound merge at Ch before reaching High Street Overbridge and the major pinch-point on the Scheme corridor. From High Street Overbridge to Taf Fechan the proposal is exclusively an online improvement due to the number of constraints to the north and south of the main line. The horizontal curvature is fully compliant throughout A retaining wall is required at approximate Ch in order to minimise works in the vicinity of an existing electricity pylon. Vertical Alignment 5.93 A gradient of 4.8% coupled with desirable minimum vertical curvature allows for the headroom requirements between the A465 main line, slip roads and A470. The alignment passes through a section of cut, beneath High Street and on approach to Taff Trail footbridge to retain Finished Road Level (FRL) of existing infrastructure, some of which is environmentally protected (Gurnos Quarry Tram Road and Leat). It is brought back up to existing ground level on approach to Taf Fechan by employing desirable minimum vertical curvature. This is to ensure the alignment is at FRL on the existing Taf Fechan structure which is being widened Due to the southerly realignment of the main line carriageway large sections of cut and fill are required on approach to the Gurnos Farm Underpass. Less than desirable minimum vertical curvature requiring a departure is employed to limit volume of cut i.e. keeping the proposed carriageway as close to EGL as possible, whilst also following design rationale. On approach to Prince Charles Hospital junction, desirable minimum vertical curvature coupled with a 2.45% straight gradient aligns the carriageway to meet existing ground level. This limits the junction Jonathan Thirkettle/ March of 45

29 footprint and height of the retaining walls supporting the side roads. Cross Sections 5.95 Throughout Cefn Coed, the cross section has been reduced to desirable minimum to mitigate impact on residential areas to the north and south of the main line, and to reduce required span of proposed structures. Due to the constrained nature of the Cefn Coed corridor and to minimise potential land take a 70 rock cutting is proposed to the east of the High Street overbridge on the approach to Taf Fechan The design proposal would however impact on properties to the south of the main line Similarly, central reservation and verge widening is limited between Taf Fechan and Gurnos Farm Underpass due to the location of an existing pylon (Ch m approximately) on the inside of the bend and to reduce impact to local infrastructure to the south. This results in SSD being relaxed to 215 m on approach to the proposed Prince Charles Hospital Junction, which constitutes a departure due to the proximity of the junction Prince Charles Hospital Junction (Ch to Ch ) 5.98 A new grade separated junction is proposed to the north of Pen-y- Dre High School. This junction would replace the existing left-off/ left-on, at-grade junctions adjacent to the Pant Industrial Estate, which would be closed. It would also provide enhanced access from the A465 to Prince Charles Hospital Access to the Pant Industrial Estate would also be provided from this junction via a new link road running to the north of the A465 main line. A new link to the Gurnos Ring Road would also be provided to the south for local residential traffic. Jonathan Thirkettle/ March of 45

30 5.100 The main line of the road would be in cutting with the proposed slip roads being retained through the junction. Similarly retaining walls up to 9.5m high are proposed to the north and south of the A465 as it passes underneath the proposed junction and Bryniau Road NMU links for pedestrians and cyclists would be provided through the junction. Existing public right of ways (PRoWs) across the A465 linking Rocky Road with Pant Industrial Estate are proposed to be stopped up. However, there is a replacement NMU provision for pedestrians and cyclists across the proposed Bryniau Road overbridge. Prince Charles Hospital Junction to Dowlais Top Junction (Ch to Ch ) This section would be predominantly an on-line improvement, though the local access road below the existing Pant Viaduct would be realigned The road would be mainly on embankments: the first, which is located west of Pant Road, would be up to 5m in height; and the second, to the east of Pant Road, would be up to 9.7m in height. Horizontal Alignment From Gurnos Farm Underpass through to Penywern (Jones Street) the alignment is predominantly online. This is achieved by applying desirable minimum horizontal curvature up to Prince Charles Hospital junction To mitigate impact on residential properties and business units to the north and south of the main line, a two-step Relaxation in horizontal curvature (510m) is required through Prince Charles Hospital junction to follow the existing alignment as much as possible. This also aligns the corridor for the approach on to Bryniau Overbridge, maintaining the skew of the existing structure. Jonathan Thirkettle/ March of 45

31 5.106 Due to the alignment and cross section of the main line carriageway, Trade Centre Wales is proposed to be demolished Curvature is provided at desirable minimum standards (1020m radius) to follow the existing alignment once again, on the approach to Pant viaduct and Pen Y Wern overbridge On the approach to the Dowlais Top junction the horizontal alignment transitions from desirable minimum radii (1020m) to a straight for approximately 740m The existing gyratory element of the current Dowlais junction would be retained but the junction is proposed to be re-configured as a grade-separated junction. The eastbound carriageway becomes the eastbound diverge, albeit shifted slightly north, and the westbound carriageway is eclipsed by the D2AP main line, requiring a new westbound merge The alignment continues over the Dowlais junction on a one design speed step reduction radius (720m). The proposed main line lies between the existing eastbound and westbound main line carriageways which would be utilised as the eastbound merge and westbound diverge respectively. It then transitions into a desirable minimum 1020m radius in order to interface with the Fochriw Road Underbridge where the Scheme ends The existing eastbound and westbound lay-by situated between Fochriw Road Underbridge and Rhymney Junction would be removed. Departmental design standards state a minimum distance of one kilometre must be present between a merge/ diverge and lay-by. Hence this existing lay-bys would not comply once the new grade-separated junction at Dowlais has been completed. Jonathan Thirkettle/ March of 45

32 Vertical Alignment East of Prince Charles Hospital junction, desirable minimum vertical curvature ensures alignment is as close to EGL as possible, before transitioning in to a 4.25% gradient across Pant Viaduct, maintaining existing finished road level To facilitate a full movement grade separated junction at Dowlais the carriageway departs EGL on approach to Jones Street underbridge via a continuation of the 4.25% gradient. It transitions to a desirable minimum hog curve (182 K) to limit volume of fill but still provide compliant headroom between the main line and junction underbridge which connects the side roads. This also ensures the new main line is at or near EGL through sections of hilly terrain to the east of the proposed junction. To match the FRL of Fochriw Road Underbridge, desirable minimum vertical curvature is employed throughout. Cross Section On approach to the proposed Pant Road bridge, both the central reserve and verge have been widened to provide a minimum SSD of 215m From the Jones Street underbridge to Dowlais junction the main line cross section would be set at standard minimum values in accordance with DMRB TD27/05, as this is a straight section of road and has fully compliant SSD (295 m) Through the junction, central reserve widening is proposed to improve a restricted SSD to a minimum of 215 m. Verge widening of up to 13.5m has been incorporated on the eastbound carriageway to maximise visibility (requiring significantly large span structures) up to the tie-in of the eastbound merge At the junction itself, cross sectional widening is limited by the residential areas to the south and Asda car park to the north. Jonathan Thirkettle/ March of 45

33 Dowlais Top Junction (Ch to Ch ) A new grade separated junction would be provided at Dowlais, with much of the infrastructure for this already in place having been constructed in 2004 as part of the A465 HoV Dualling Section 4 - Tredegar to Dowlais Top Scheme The existing alignment of the A465 would form the eastbound merge and westbound diverge from where the main line would join the dual carriageway road constructed as part of the Section 4 Scheme. The main line would be constructed over the existing Dowlais roundabout. West of the junction the road would be on embankment, which would be 11m high at its highest point. To the east of the roundabout the road would use the existing embankment constructed as part of the adjacent Section 4 Scheme. Main Line Junctions All proposed main line junctions have been designed as grade separated Proposed main line junctions are summarised in Table 2. Jonathan Thirkettle/ March of 45

34 Table 2 - Scheme Main Line Junction Proposals Junction Junction Location Junction Form Purpose Hirwaun Ch Existing junction has been skewed slightly in a southeasterly direction to facilitate proposed main line alignment and avoid an existing high pressure gas main. Croesbychan Ch Situated to the east of Mineral Railway and to the west of Nant Melyn. Baverstock Ch Situated some 610 m to the west of the existing Baverstock Junction. A470/A465 Ch Existing A470/A465 junction. Grade separated full movement circulatory with two structures over the main line. DG1C diverge layout and MG1C merge layout proposed for eastbound and westbound slip roads. Grade separated full movement dumbbell junction with a single underbridge carrying the main line. DG2E westbound diverge layout and MG1C eastbound parallel merge layout. Other slips: DG1C and MG1C. Grade separated full movement dumbbell junction with a single underbridge carrying the main line. DG1C diverge layout and MG1C merge layout proposed for eastbound and westbound slip roads. Grade separated full movement dumbbell junction with a single underbridge carrying the main line. DG2E (eastbound) and DG1C (westbound) diverge layouts; and MG1C merge layout (parallel merge for westbound) proposed To separate main line and side road traffic. Junction maintains connectivity to all existing side roads, including the existing A465 main line carriageway. Provides connectivity between local roads and A465. Local infrastructure has been altered due to main line proposals; this encompasses a new underbridge (at Court Lodge) to reconnect Swansea Road and Keepers Lane to Llwydcoed Road. Potential to connect the Aberdare Bypass (Cynon Gateway) Scheme when constructed. To remove direct access on to the A465 and to separate local and main line traffic. New link road serves business to the north. Swansea Road has been extended to tie in with the southern gyratory together with Llwydcoed Road. Merthyr Road connects to Swansea Road via a new T-type junction. To separate high-speed traffic between two major trunk roads. Junction allows for full movement of traffic between A470 and A465 in all directions. Jonathan Thirkettle/ March of 45

35 Junction Junction Location Junction Form Purpose Prince Charles Hospital Ch Situated some 900 m west of the existing junction. for slip roads. Existing viaduct utilised as westbound diverge. Grade separated full movement junction with two structures over the main line carriageway. DG1C diverge layout and MG1C merge layout proposed for eastbound and westbound slip roads. Dowlais Top Ch Grade separated full movement circulatory with two bridges carrying the main line. Side roads remain untouched. DG1C diverge (DG2E for westbound) layout and MG1C merge layout proposed for eastbound and westbound slip roads. Removes half-junctions at Gurnos and Galon Uchaf and eliminates weaving issues. Junction allows direct access to the industrial estate from the A465 via a single link road to the north. This option removes HGVs and reduces volume of traffic on local roads improving the safety of local residents. Gurnos Ring Road maintained and ties in with the proposed junction. Access to industrial units throughout Pant maintained via minor junctions. To separate main line and side road traffic. Existing eastbound and westbound carriageways have been utilised as the merge and diverge respectively. Side Roads and Local Highway Connections The Scheme would be connected to the local highway network by the six junctions referenced in Table 2. Modifications to the local highway network would also be required where the Scheme main line crosses the local network. Highways Drainage The Scheme highway drainage systems have been designed in accordance with the relevant sections of Volume 4 of the DMRB. Jonathan Thirkettle/ March of 45