Part 2: Engineering Assessment 4 Engineering Description 4.1 Introduction 4.2 North Corridor Option 1 4.3 North Corridor Option 2 4.4 South Corridor Option 1 4.5 South Corridor Option 2 4.6 References

Part 2: Engineering Assessment

4 Engineering Description

4.1 Introduction

4.1.1 This chapter presents the engineering assessment of the DMRB Stage 2 route corridor options for the Forth Replacement Crossing.

4.1.2 In the preparation of options for DMRB Stage 2 assessment, each corridor has over its full length been designed to current standards utilising the technical guidance provided by the Design Manual for Roads and Bridges (DMRB). Shorter improvements within each corridor are feasible and will be considered at the next stage of the study. The following documents have been referenced in the development of both the northern route corridor options and southern route corridor options:

  • TD 9/93 Highway Link Design
  • TD 27/05 Cross-Sections and Headrooms
  • TD 22/06 Layout of Grade Separated Junctions
  • TD 39/94 The Design of Major Interchanges
  • TD 40/94 Layout of Compact Grade Separated Junctions
  • TD 42/95 Geometric Design of Major/Minor Priority Junctions
  • TD 50/04 The Geometric Layout of Signal-Controlled Junctions and Signalised Roundabouts

Design Considerations

4.1.3 In addition to the implementation of best practise through the use of the relevant design standards, the following physical features have been considered:

  • Existing topography, the vertical geometry of each route corridor option being designed to achieve the best cut-fill balance possible, minimising the transportation of acceptable material.
  • Headroom clearance requirements to road, rail and watercourse crossings.
  • Connections to the proposed replacement bridge; and
  • Requirements in the vicinity of local communities where screening or depressed vertical geometry may be required to minimise the visual impact of the corridor.

4.1.4 The design of the northern and southern route corridor options for DMRB Stage 2 assessment has been undertaken using a ground survey contour model. Produced from LiDAR Survey, this model does not recognise all of the features associated with the existing topography of the area.

4.1.5 In the preparation of design work for DMRB Stage 3 assessment, a new topographical survey model in the form of a detailed ground survey will be utilised. This will enable the horizontal and vertical geometry of the selected route corridor options to be further refined, confirming any departures from standard or geotechnical solutions which might be required.

4.1.6 For the purposes of DMRB Stage 2 assessment, the route corridor options discussed within this report have been considered over the full extents of the Forth Replacement Crossing study area. The preferred corridor identified need not be implemented in full as a single scheme. As a part of the next stage of design and assessment, further detailed consideration shall be given to the form and function of the junctions required and the extent and timing of the road infrastructure improvements provided within the preferred corridors. The developing design shall also reflect future consideration of the use of the Forth Road Bridge.

Junctions

4.1.7 The junction configurations provided in association with each of the northern and southern route corridor options are indicative layouts at this stage, capable of maintaining/improving access between local and strategic connections. The level of service and form of junction provided is subject to ongoing development. A more detailed assessment of junction provision will be included within the DMRB Stage 3 Report relative to the northern and southern route corridor options identified for further assessment.

Drainage

4.1.8 No detailed drainage design has yet been undertaken however the design shall incorporate Sustainable Drainage Systems (SUDS) which may include the provision of swales and filter trenches. The intention of such systems is to limit the amount of surface water discharging from the carriageway into existing watercourses in all but extreme weather situations. This will be achieved through the provision of attenuation ponds and/or lagoons at frequent intervals, containing the surface water runoff generated by the corridor.

4.1.9 The design of drainage systems to complement the roads infrastructure associated with the proposed replacement bridge will be undertaken as part of the DMRB Stage 3 assessment process.

4.1.10 The extents of the drainage provided as part of the Forth Replacement Crossing project will be based upon a predetermined storm return frequency, the drainage design being tailored to the topography of the area.

4.1.11 A thorough consultation process will be instigated with Scottish Environment Protection Agency (SEPA), Scottish Natural Heritage (SNH) and other relevant consultees to ensure that water quality targets are met.

Earthworks

4.1.12 A detailed earthworks design has not yet been undertaken, however features likely to be required include: cuttings with mid-slope and/or rockhead berms, rock slope stabilisation measures, embankments, ground stabilisation measures to accommodate construction over soft deposits and minimise settlement, treatment of abandoned mineworkings, and appropriate associated surface and in-slope drainage measures to tie-in with the carriageway drainage systems.

4.1.13 A suitable design for the earthworks associated with the proposed roads infrastructure will be developed as part of the DMRB Stage 3 assessment process.

4.1.14 In the initial development of the northern and southern route corridor options, earthworks slopes of 1:2 (vertical:horizontal) for embankment and 1:2.5 for cuttings have been implemented. The geotechnical assessment of each route corridor option provides guidance on the earthworks slopes which may be implemented through design development.

4.1.15 This assessment is based on the preliminary data from the 2008 ground investigations, together with pre-existing historical borehole information where relevant. The assessment of soil / rock types is based on the log descriptions, to BS5930:1999, as they stand at present, however these have not been finalised. No checking of soil descriptions against laboratory testing has been undertaken to confirm the soil type / classification. The co-ordinates and ground levels for the exploratory holes are preliminary and unchecked at present.

Pavement Design

4.1.16 The provision of a detailed pavement design has not been considered as a part of this DMRB Stage 2 assessment, a broad based assessment having been undertaken for cost estimate purposes only. The pavement design will be considered as a part of the DMRB Stage 3 assessment, taking account of any existing pavement which might be utilised following a detailed analysis of its condition.

4.1.17 The pavement design for new and reconstructed sections of carriageway shall be either of fully flexible or flexible composite construction, the pavement thickness being designed to suit the predicted traffic flow. Pavement surfacing materials promoting reduced traffic noise and reduced surface spray in wet conditions shall be considered. Rigid pavements are unlikely to be specified for the roads infrastructure connecting the proposed replacement bridge to the existing trunk road/local road network.

Road Restraint Systems

4.1.18 Given the extent of the options being considered as part of this DMRB Stage 2 assessment, a detailed design considering road restraint systems has not been developed. Taking into account the requirement for land acquisition, a broad-based assessment has been undertaken for cost estimate purposes only.

4.1.19 Hazard locations in accordance with TD 19/06 – Requirements for Road Restraint Systems will be identified and assessed, a suitable design being provided for the route corridor options taken forward to DMRB Stage 3 assessment.

Traffic Signs / Carriageway Finishes

4.1.20 The detailed design of traffic signs, delineation and road markings has not been considered as part of the DMRB Stage 2 assessment, a broad-based assessment having been undertaken for cost estimate purposes only. The provision of such details will be considered as part of the DMRB Stage 3 assessment process with reference paid to relevant design standards including The Traffic Signs Regulations and General Directions 2002 and the Traffic Signs Manual.

Structures

4.1.21 Each of the route corridor options under consideration requires significant structural provision. Whilst the widening of existing structures can be considered in some instances, new structures will be required for new and improved junctions, major side road crossings, railway crossings, private rights of way and drainage features.

4.1.22 Where possible, all structures shall be designed to minimise their impact on the surrounding landscape. The maintenance requirement applicable to each structure shall be examined to ensure minimum disruption to the surrounding environment whilst ensuring the effective operation of the proposed corridor.

High Occupancy Vehicle (HOV) Lanes

4.1.23 Each of the northern and southern route corridor options under consideration as part of this DMRB Stage 2 assessment is capable of practically providing for a high occupancy vehicle lane in each direction only if the improvement is carried out over the full length of the corridor. They may not be feasible for a more limited corridor upgrade.

4.1.24 The location of such provision is dependant on the carriageway cross section implemented. The requirement exists to maintain two lanes of general traffic in addition to any HOV lane provided, in each direction at all times.

4.1.25 In the provision of North Corridor Option 1, South Corridor Option 1 and South Corridor Option 2, an HOV lane can be accommodated, running in the outer of the three trafficked lanes provided on the mainline carriageway.

4.1.26 In the implementation of North Corridor Option 2, only two trafficked lanes are provided, requiring a compromise solution to be considered. In this instance general traffic and HOV provision would be split between the proposed North Corridor Option 2 mainline and the existing A90/M90.

4.2 North Corridor Option 1

4.2.1 Table 4.1 read in conjunction with Figure 4.1 (Volume 2) provides a description of the North Corridor Option 1 mainline carriageway design.

Table 4.1: Engineering Description of North Corridor Option 1 Mainline

Corridor

Mainline Description

North Corridor Option 1

Design Details

  • Route Corridor Length: 7.1km
  • Design Speed: 120kph
  • Dual three lane motorway (D3M) encompassing:
    • 11m running carriageway
    • 3.6m hard shoulders (where practicable for future hard shoulder running)
    • 0.7m hardstrips
    • 3.1m central reserve
    • 1.5m verge

Design Geometry

  • Minimum Horizontal Radius = 600m
  • Minimum Vertical Gradient = 1.1%
  • Maximum Vertical Gradient = 4%
  • Minimum Sag Curve Radius = 5500m
  • Minimum Crest Curve Radius = 5500m

Engineering Constraints

4.2.2 The design of North Corridor Option 1 takes into consideration the following physical engineering constraints.

  • Existing topography
  • A90/M90 route corridor
  • Junction provision and side roads connectivity
  • Side road crossings
  • Adoption of existing structures
  • Railway crossings at Ferrytoll Junction and Masterton Junction
  • Environmentally significant areas (refer to Part 3)
  • Possible future multi-modal developments (LRT, BRT, guided buses or trams)

Mainline Features

4.2.3 A full improvement to North Corridor Option 1 consists of the online upgrading of the existing A90/M90 to dual three lane motorway standard. South of Ferrytoll Junction, the mainline shall be implemented as an all purpose carriageway with hard shoulder to maintain cross-Forth access for non-motorway traffic.

4.2.4 Departing the proposed replacement bridge northwards at St Margaret’s Hill, the corridor descends on a vertical gradient of 3.5% towards Dunfermline Waste Water Treatment Works and Ferrytoll Junction.

4.2.5 To facilitate connection between the proposed replacement bridge and the A90/M90 route corridor, a R720 metre left hand horizontal curve is provided sweeping the alignment along the eastern perimeter of St Margaret’s Marsh. The horizontal and vertical tie in to the existing carriageway is coincidental with Ferrytoll Junction, a junction which is to be reconstructed as part of this option.

4.2.6 Mirroring the horizontal geometry of the existing A90/M90, the corridor continues north on a gentle incline of 1.1% requiring the widening of significant cut slopes to accommodate the dual three lane motorway cross section. Passing to the west of Ferrytoll Park and Ride on a R690 metre right hand horizontal curve the corridor then climbs Muckle Hill at 3.3% cresting to the east of Castlandhill in close proximity to Dunfermline Wynd Overbridge.

4.2.7 The corridor then descends at 4% towards a revised Admiralty Junction, its low point situated west of Belleknowes Industrial Estate. Continuing north through Admiralty Junction on a R600 metre right hand curve, the corridor then rises at a gradient of 3.5% towards Masterton Junction.

4.2.8 On approach to Masterton Junction, the corridor is carried on viaduct, crossing the Fife Circle Railway Line and link roads providing access to the A823(M). Passing through Masterton Junction itself, the corridor turns northeast through an R650 metre horizontal right hand curve passing to the south of the properties at Middlebank. Situated on embankment, the corridor then returns to a northerly bearing, a R960 metre left hand curve facilitating this.

4.2.9 North of Middlebank, the dual three lane motorway continues to climb towards Halbeath Interchange, requiring the widening of cutting and embankment slopes. At Halbeath Interchange itself, a lane drop/lane gain arrangement is provided to the A92, facilitating a cross section transition to the dual two lane motorway standard associated with the existing M90.

Departures from Standard

4.2.10 Incorporating much of the A90/M90 route corridor, North Corridor Option 1 inherits the horizontal and vertical geometry associated with the existing corridor. Whilst many of the substandard characteristics of the mainline carriageway can be eliminated through the implementation of improvements at detailed design stage, substandard geometry elements are likely to remain.

4.2.11 The existing R600 metre right hand curve located at Admiralty Junction and the R650 metre right hand curve located within the junction area at Masterton represent relaxations of 2 design speed steps below desirable minimum. Whilst permissible in isolation, their provision in combination with a reduction in stopping sight distance is not and hence it is likely that Departures from Standard will be required. A coincidental relaxation of this nature is only permitted up to 1 design speed step below desirable minimum.

4.2.12 Initial discussions have been held with Transport Scotland’s Standards Branch as to the suitability of the design work undertaken to date. Should this option be taken forward to DMRB Stage 3 assessment, the development of the design shall be discussed further with Standards Branch, any departures from standard being highlighted at an early stage.

Junction Provision

4.2.13 Table 4.2 read in conjunction with Figures 4.2 and 4.3 (Volume 2) gives an overview of the indicative junction arrangements developed for North Corridor Option 1.

Table 4.2: Engineering Description of North Corridor Option 1 Junctions

Corridor

Junction Description

North Corridor Option 1

Ferrytoll Junction

  • New Grade Separated Junction arrangement providing local and non-motorway access.
  • Northbound, new roundabout provided for strategic/local connectivity.
  • Northbound interaction between mainline and local roads through new slip road arrangements.
    • Mainline Diverge to Ferrytoll Junction
    • Mainline Merge from Ferrytoll Junction
    • Access maintained to B980, B981 & Ferry Toll Rd
  • Southbound, existing roundabout adapted allowing interaction between mainline, local roads and Ferrytoll Park & Ride through new slip road arrangements.
    • Mainline Diverge to Ferrytoll Junction
    • Mainline Merge from Ferrytoll Junction
    • Access maintained to B980, B981 & Ferry Toll Rd
  • Bus priority functionality provided through hard shoulder running on slips.
  • Junction future-proofed for future transport modes i.e. LRT, BRT, guided buses or trams.
  • Connection to the Forth Road Bridge to be maintained through the provision of new links.

Admiralty Junction

  • Existing Grade Separated Junction retained.
  • South facing slip road provision reconfigured for implementation of D3M mainline cross section.
  • North facing slip roads closed, improving operational safety of mainline.
  • Through access maintained between A985 & A921.

Masterton Junction

  • New free flow all movements junction
  • Northbound merge/diverge movements between mainline & A823(M) retained with some reconfiguration.
    • Mainline Diverge to A823(M)
    • Mainline Merge from A823(M)
  • Southbound links reconstructed, including provision of loop arrangement, improving operational safety.
    • Mainline Diverge to A823(M)
    • Mainline Merge from A823(M) – Simple Loop
  • New roundabout provided connecting to A921 & B981, compensating for loss of north facing slip roads at Admiralty.
    • Southbound slip road to A921 abutted to A823(M) Mainline Diverge. .
    • Northbound link connects A921 and B981 between new roundabout and Mainline Merge from A823(M).

Topography & Land use

4.2.14 North Corridor Option 1, utilising much of the A90/M90 route corridor, passes through a mixture of residential, commercial and agricultural land.

4.2.15 To the south, the coastal flats of the Firth of Forth are a prominent feature with pockets of woodland and St Margaret’s Marsh dominating the northern shoreline. To the east, the village of North Queensferry is situated upon coastal hills. To the west the former Naval Dockyard at Rosyth signifies the area’s maritime heritage. Closed as an operational naval base in 1994, the facility is now being re-developed for private sector use with the provision of ferry and cargo terminal facilities and a new business park.

4.2.16 Continuing north, the coastal flats associated with the Firth of Forth give way to a more rugged landscape, the terrain steepening to the south of Rosyth where Castlandhill, a prominent coastal hill, is situated. The corridor passes to the east of Castlandhill, the rugged landscape of the area requiring the widening of existing cut slopes so to accommodate the increased dual three lane motorway cross section.

4.2.17 North of Castlandhill, the corridor descends into a valley dominated by residential and commercial properties. The town of Rosyth, situated to the west of the corridor, has a distinct industrial history having been developed as a garden city to house the workers from the neighbouring dockyard. To the east is situated the town of Inverkeithing. Like Rosyth, Inverkeithing is also associated with maritime activities, its ship-breaking yard being situated in Inverkeithing Bay (Inner Bay). Industry continues to be a prominent feature in the area with significant commercial premises still present. East of the corridor and to the north of Inverkeithing, Belleknowes Industrial Estate contains a number of industrial premises. Network Rail property is also a prominent feature with the Fife Circle Railway Line passing beneath the mainline south of Masterton Junction, linking Rosyth and Inverkeithing.

4.2.18 Beyond Masterton Junction, agricultural land becomes a prominent feature, the topography of the area rising towards Crossgates and Halbeath. To the east, areas of woodland intersperse farm properties. To the west, agricultural properties are bounded by long established woodland and historical quarrying sites bearing limestone and sandstone. Beyond lies the town of Dunfermline.

Geotechnical Summary

4.2.19 North Corridor Option 1 utilises much of the existing A90/M90 corridor, however to accommodate the widened carriageway, junctions and tie-ins to the proposed replacement bridge, construction or modification of cuttings and embankments will be required.

4.2.20 Until the completion of the ground investigations and associated testing, an assessment of the likely slope angles will not be undertaken. The general design assumptions for slopes at present are that they will not be steeper than 26.6o (1V:2H) for both embankments and cuttings. However, in certain cases these may have to be relaxed to satisfy the stability of the slope. Steeper angles of 60o to 80o (2V:1H - 5V:1H) may be possible in rock depending on rock type, discontinuity orientations, spacing and type/extent of infill material, and groundwater.

4.2.21 The cuttings are likely to be formed partially within superficial deposits and partially within rock. Rock slope drainage measures such as raking drains and relief drains may be required, as well as standard rock slope stabilisation treatment.

4.2.22 A limit of around 7 metres has been assumed in terms of maximum height/depth of a feature before an interim berm is required. This is for improved stability as well as maintenance access. A berm at the soil/rock contact will also be required for slope stability and drainage.

4.2.23 Soft alluvial deposits are recorded in the vicinity of Masterton Junction. Where these deposits are encountered within the footprint of the road embankment, consideration must be given to the avoidance of residual settlement (post construction). This may take the form of ground treatment; including pre-loading with or without band drains and replacement of soft deposits, or programming of construction to allow for settlement to occur. Artesian groundwater conditions were encountered in association with these deposits; they will require to be taken into consideration during design and construction in this area.

Geotechnical Summary

4.2.24 Table 4.3, in association with Figure 4.4 (Volume 2), provides an indication of the geotechnical features and anticipated earthworks associated with North Corridor Option 1. Where minimal alteration is proposed to the vertical alignment of the centreline, an indicative dimension of the existing earthworks has been derived from the earthwork interface drawings. Modification of the existing earthworks may be required to accommodate the additional carriageway width.

Table 4.3: Geotechnical Summary of North Corridor Option 1

Chainage
(m)

Anticipated Critical Section

Height at Critical Section*

Likely Design Angle

Ground Conditions at Critical Section

Groundwater Encountered (bgl)

Remarks

6800m to 7200m

6850m

41.87m

Structure

GL to 1.2m

Topsoil

None

  

1.2m+

Bedrock (Dolerite)

7200m to 7400m

7250m

24.8m

Structure

GL to 5.3m

Made Ground

>2.0m

  

5.3m+

Bedrock (Sandstone)

7400m to 7500m

7450m

8.59m

Structure / (Embankment 1V:2H)

GL to 1.8m

Made Ground

>3.2m

High embankment, intermediate berms and slope drainage will be required.

1.8m to 12m

Dolerite Boulders

12m to 33.7m

Soft silty clay

33.7m+

Bedrock (Mudstone)

7500m to 7800m

7800m

9m

Structure / (Embankment 1V:2H)

GL to 8.0m

Made Ground / Glacial Sands and Gravels

None Encountered

  

8.0m+

Bedrock (Dolerite)

7800m to 8150m

8050m

N/A
15m (Cutting)

At Grade (East)

Cutting (West) 1V:2H

GL to 2.0m

Made Ground

13.1m

  

2.0m to 4.00m

Alluvium

4.0m+

Bedrock (Dolerite)

8150m to 8700m

8450m

23m (Cutting)

7m (Embankment)

Cutting (East)

Embankment (West)

1V:2H

East Side of Existing Road

2.80m

Heavy Strike at 14.30m

Problems may arise with settlement of soft deposits and differential settlement due to variable rockhead.

GL to 2.0m

Weathered Glacial Till

2.0m+

Bedrock (Dolerite)

West Side of Existing Road

GL to 1.8m

Made Ground

1.8m to 6.70m

Alluvium

6.70m to 8.0m

Peat

8.0m to 14.3m

Alluvium

14.3m to 19.65m

Glacial Till

19.65m to 20.15m

Weathered Bedrock

20.15m+

Bedrock (Mudstone)

8700m to 9150m

8900m

26m

Cutting

1V:2H

West Side of Existing Road

15.4m

Deep cutting with groundwater anticipated towards the base of the cutting. Berms will be required at regular intervals, with soil/rock berm. Rock slope drainage and surface drainage.

Rock cut angle to be confirmed.

GL to 10.2m

Glacial Till

10.2m+

Bedrock (Mudstone)

East Side of Existing Road

East Side of Existing Road

GL to 3.0m

Weathered Glacial Till

3.0m 30.1m

Glacial Till

30.1m + Bedrock (Sandstone)

30.1m + Bedrock (Sandstone)

Bedrock was only found at Ch 8900

9150m to 9400m

9150m

5m

Embankment 1V:2H

GL to 2.2m

Made Ground

None

Encountered

Low height embankment. Strength of Glacial Till may decide capping thickness for majority of embankment.

2.2m to 20.5m

Glacial Till

20.5m+

Bedrock (Dolerite), Mudstone to North

9400m to 9700m

9500m

7m

Embankment / Structure

GL to 12.7m

Weathered Glacial Till/Glacial Sands & Gravels

2.0m

 

12.7m+

Bedrock (Dolerite)

9700m to 10100m

-

N/A

At Grade

General Ground Conditions

1.8m

 

GL to 9.0m

Weathered Glacial Till

9.0m to 15.2m

Glacial Sands and Gravels

15.2m to 16.3m

Weathered Bedrock

16.3m+

Bedrock (Sandstone)

10100m to 10400m

10400m

11.7m

Embankment/ Structure

GL to 21.0m

Glacial Till and Glacial Sands & Gravels

10.0m

High embankment will require intermediate berms.

21.0m+

Bedrock (Mudstone)

10400m to 10700m

10450m

10.1m

Embankment

GL to 3.4m

Weathered Glacial Till

None Encountered

High embankment will require intermediate berms.

3.0m+

Bedrock (Sandstone)

10700m to 11100m

11050m

12.6m

Embankment

GL to 3.0m

Weathered Bedrock

None Encountered

High embankment will require intermediate berms.

3.0m+

Bedrock (Mudstone)

On East side of existing road;

Bedrock is interbedded mudstone and siltstone

BHN 1047m:

  

GL to 2.20m

Weathered Glacial Till

2.20m to 2.80m

Bedrock (Mudstone)

2.80m to 3.40m

Coal

3.40m +

Mudstone

11100m to 11900

11500m

5m, locally 15m (Cutting)

2m (Embankment)

Cutting (W)

Embankment (E)

1V:2H

GL to 2.0m

Weathered Glacial Till

3m

 

2.0m+

Bedrock (Sandstone)

11900m to 12500

12100m

2m

Embankment 1V:2H

West Side of Existing Road

2.5m

 

GL to 2.5m

Weathered Glacial Till

2.5m+

Bedrock (Mudstone)

East Side of Existing Road

GL to 2.0m

Weathered Glacial Till

2.0m to 7.0m

Glacial Till

7.0m +

Bedrock (Sandstone)

occasional shallow rockhead of mudstone in this area

* - Cutting Depths are based on the centreline long section and the earthworks interface drawings, Figures 4.4a and 4.4b (Volume 2).

Mineworkings

4.2.25 Ten designated mineral holes were undertaken during the 2008 ground investigation in proximity to the M90 north of Masterton Junction. Intact coal was encountered in nine of the boreholes with the remaining borehole, located adjacent to proposed cutting at approximate Chainage 10,900 metres, recording broken ground. Broken ground was encountered at a depth corresponding to the anticipated level of the coal seam in this borehole (between 14.7 metres and 16.2 metres below ground level) and is considered to be associated with the workings that are recorded on the mine abandonment plan in the vicinity of the borehole.

4.2.26 In most boreholes, the intact coal is considered to represent the thin coal seam underlying the Charlestown Main Limestone, due to the presence of a prominent limestone horizon within the sequence immediately overlying the coal in some of the deeper boreholes. The stratigraphical sequence and the location and depth of the coal are generally consistent with available geological information.  Two of the positions encountered coal at or around its subcrop at a level of 2.8 metres below ground level, with a further borehole to the southeast in proximity to the new southbound diverge link encountering coal at subcrop at a deeper level of 8 metres below ground level. The thickness of the coal was found to vary between 0.2 and 1.0 metres thick. A deeper intact coal seam with a thickness of 0.5 metres was encountered north of the A823(M) to M90 northbound slip road, at a level of 17.6 metres below ground level.

4.2.27 Outwith the designated mineral holes area, intact coal has also been encountered at one borehole further northeast along the existing M90.  It is not apparent from the geological plans with which seam this can be stratigraphically correlated as there are no coal subcrops shown in the vicinity of this location.  The coal was recorded to be 0.7 metres thick with the top of the coal at a level of 8.45 metres below ground level. A further assessment of mineworkings would be necessary should this option be taken forward.

Hydrology

4.2.28 Figure 8.1 (Volume 2) details the watercourses within the study area of the Forth Replacement Crossing Project. Further information on hydrology is provided in Part 3, Chapter 8 of this report.

4.2.29 Brankholm Burn flows west to east through the town of Rosyth and traverses the M90 south of Masterton Junction. During the construction phase, an extension or replacement of the existing culvert will be required.

4.2.30 Pinkerton Burn traverses the M90 north of Masterton Junction. The condition of the existing structure at this crossing point will determine whether it needs to be extended or replaced.

4.2.31 In the provision of a link to the A921 from the reconstructed Masterton Junction, a new culvert crossing to the northeast of Inverkeithing Railway Junction is likely to be required.

Structures

4.2.32 The following paragraphs read in conjunction with Figure 4.5 (Volume 2) detail the structural requirements associated with North Corridor Option 1.

Structures 177-4 and 177-5

4.2.33 Structures 177-4 and 177-5 carry the existing A90 over Ferrytoll Junction. Both structures will require widening to accommodate the dual three lane motorway. The widening comprises precast beam and slab integral construction founded on spread footings.

Structures 177-10, 177-11 and 177-12

4.2.34 Structure 177-10 is the existing Ferrytoll railway tunnel under the existing A90 and the new mainline and its slip roads. It is a single span structure with an overall length of approximately 95 metres comprising a maximum span of 4.95 metres at a varying skew.

4.2.35 Structure 177-11 is an existing structure which carries the B980 over the Inverkeithing South Junction – Rosyth Dockyard Branch Line Railway close to the entrance/exit to the tunnel. It is a single span structure with a maximum span of 5.88 metres at a skew of 23°.

4.2.36 Both Structures 177-10 and 177-11 are concrete arch structures of integral construction. Bridge 177-10 is founded on spread footings; however the foundation type for structure 177-11 is unknown.

4.2.37 Structure 177-12 is located adjacent to structure 177-11. It is a single span structure with a span of 20.5 metres at a skew of 23°. It is a precast beam and slab structure of integral construction founded on spread footings and was built circa 2006.

4.2.38 The intention is that all structures shall be retained for use with North Corridor Option 1.

Structures 177-1, 177-2, 177-3 and 177-8

4.2.39 Structure 177-1 will carry the mainline from the new crossing to Ferrytoll. Structure 177-2 will carry the slip road from the proposed replacement bridge to Ferrytoll. Structure 177-3 will carry the link road from the Forth Road Bridge to the new mainline at Ferrytoll and Structure 177-8 will carry the link road from the M90 southbound to the Forth Road Bridge.

4.2.40 Structure 177-1 consists of eight spans with an overall approximate length of 625 metres with a maximum span of 90 metres. Structures 177-2, 177-3 and 177-8 are also multiple span structures with overall approximate lengths of 550 metres, 570 metres and 550 metres respectively. All four structures comprise steel/concrete composite construction founded on either bored concrete piles or spread footings. Structure 177-1 is on a very high skew, has bifurcations on the road and a varying road width. Access to Structures 177-1, 177-2 and 177-3 is very difficult due to the location and steep gradient of the surrounding land. Structure 177-8 will be of complex construction as it is curved in plan and crosses existing side roads. The construction of these bridges will require major traffic management.

Structures 177-6, 177-7 and 177-9

4.2.41 Structures 177-6 and 177-7 will carry the northbound diverge slip road from the proposed replacement bridge over the existing Ferrytoll Junction. Structure 177-9 will carry the slip road over the Inverkeithing South Junction – Rosyth Dockyard Branch Line Railway, north of the existing Ferrytoll roundabout.

4.2.42 Structures 177-6, 177-7 and 177-9 comprise single span structures with spans of 10 metres, 15 metres and 15 metres respectively. All three structures comprise of precast beam and slab integral construction founded on spread footings.

4.2.43 Structures 177-6 and 177-7 will be constructed over the existing Ferrytoll roundabout which will require significant traffic management. Structure 177-9 will require stringent measures during construction over the railway with disruptive possessions likely to be required.

Structure 170-1

4.2.44 The reconstructed Dunfermline Wynd Overbridge will carry Dunfermline Wynd over the new mainline. It is a three span structure with an overall approximate length of 90 metres with two end spans of 25 metres and a central span of 40 metres. It comprises of steel/concrete composite integral construction founded on spread footings.

Structure 182-8

4.2.45 Structure 182-8, an existing retaining wall at Admiralty Junction, is no longer required and is to be demolished.

Structures 182-9 and 182-11

4.2.46 The rebuilt Structure 182-9 and new Structure 182-11 will be cantilever retaining walls on the southeast and southwest sides of the Admiralty Junction respectively, built to accommodate the new dual three lane motorway. The walls will have a maximum retained height of 8 metres and an overall length of 120 metres. Both will be constructed using reinforced concrete and founded on spread footings.

Structures 182-6 and 182-7

4.2.47 Existing Structures 182-6 and 182-7 carry the M90 over Admiralty Junction. They will be widened with the widening in the form of a precast beam and slab deck supported on extended sections of the existing abutments. New wingwalls will be provided where required.

Structure 182-5

4.2.48 Structure 182-5 is an existing concrete arch culvert carrying the Brankholm Burn under the new road. The existing concrete arch culvert requires to be extended by approximately 8 metres to accommodate the road widening from a dual two lane motorway to dual three lane motorway.

Structures 182-12 and 182-15

4.2.49 Structure 182-12 will carry a new link road to the M90 northbound over Masterton Viaduct and the A823(M). Structure number 182-15 will carry the A823(M) over the M90 at Masterton Viaduct.

4.2.50 Structure 182-12 comprises a ten span structure with an overall approximate length of 410 metres consisting of four spans of 40 metres, three spans of 50 metres, two spans of 35 metres and one span of 30 metres. It is curved in plan.

4.2.51 Structure 182-15 comprises a three span structure with an overall approximate length of 120 metres consisting of two spans of 35 metres and one span of 50 metres.

4.2.52 Both structures comprise of steel/concrete composite construction founded on bored concrete piles. Constructed over the existing Masterton Viaduct, major traffic management will be required.

Structure 182-10

4.2.53 Structure 182-10 will carry Masterton Road over the M90 southbound off slip road at Masterton Junction. It consists of a single span with an approximate length of 15.3 metres at a skew of 20°. It comprises of precast beam and slab integral construction founded on spread footings.

Structure 171-2

4.2.54 The reconstructed Duloch Overbridge, Structure 171-2, will carry Aberdour Road over the new mainline. It consists of a three span structure with an overall approximate length of 66 metres consisting of two shorter spans of 15.5 metres and a maximum span of 35 metres at a skew of 10°. It comprises of steel/concrete composite integral construction founded on bored concrete piles.

Structure 000-1

4.2.55 The reconstructed Calais Muir Overbridge, Structure 000-1, will carry a side road over the new mainline. It consists of a three span structure with an overall approximate length of 65 metres consisting of two shorter spans of 15 metres and a maximum span of 35 metres. It comprises of steel/concrete composite integral construction founded on bored concrete piles.

Structure 182-1

4.2.56 Structure number 182-1, Masterton Viaduct, carries the M90 over the A823(M)

4.2.57 To incorporate the existing Masterton Viaduct as part of North Corridor Option 1, the following recommendations shall be considered:

  • where required, widen the existing railway spans with either precast prestressed concrete beam and infill or steel filler beam type construction;
  • where required, widen the existing concrete spans with either a reinforced concrete slab or precast prestressed concrete beam and infill type construction;
  • in order to remain outwith the required railway clearance envelope for the southbound carriageway, consider carrying the A823(M) eastbound to M90 southbound on-slip on a separate structure, tying back into the M90 south of the existing south abutment;
  • north of the structure, provide a link from the M90 southbound carriageway onto a new southbound on-slip to carry the abnormal SV196 load over a new southbound on-slip structure; and
  • ensure the effect of the abnormal load from the widened section onto the existing structure is no more severe than current capacity.

4.2.58 Further details for the possible inclusion of the existing Masterton Viaduct will be considered further as part of the DMRB Stage 3 assessment process.

Structure 182-2

4.2.59 Structure 182-2, an existing single span structure carrying the M90 northbound off slip road to the A823(M) over the Fife Circle Railway Line is to be retained for use.

Structure 182-13

4.2.60 Replacement Structure 182-13 comprises a single span with a maximum length of 25 metres at a skew of 15°. It consists of precast beam and slab integral construction founded on bored concrete piles. The structure will require stringent measures during demolition and re-construction over the railway with disruptive possessions likely to be required.

Structure 182-14

4.2.61 Structure 182-14, an existing structure under the A823(M) is no longer required and will be demolished.

Structure 182-3

4.2.62 Structure 182-3, an existing structure carrying the A823(M) over the M90 is no longer required and will be demolished.

Structure 182-4

4.2.63 Replacement Structure 182-4 will carry Masterton Road over the M90. It comprises a single span with a span length of 28 metres. It consists of a steel/concrete composite integral construction founded on bored concrete piles.

Public Utilities

4.2.64 North Corridor Option 1 is likely to impact the following public utilities plant :

  • 18no. Crossings of high voltage electric cables at 33Kv (overhead)
  • 10no. Crossing of high voltage electric cable at 11Kv (underground)
  • 2no. Crossings of intermediate pressure gas main (2 to 7 bar pressure)
  • 7no. Crossings of medium pressure gas main (0.75 to 2 bar pressure)
  • 7no. Crossings of trunk water mains

4.2.65 In addition to the above, other small-scale plant is affected such as telecommunication cables, street lighting cables, low-pressure gas pipes and small diameter water supply pipes.Constructability

4.2.66 Whilst online widening of the existing A90/M90 makes best use of the existing corridor, its implementation is not without difficulty. As detailed, a widening of the carriageway cross section to dual three lane motorway will require a significant re-engineering of existing earthworks, embankments and cut slopes so to accommodate a continuous hard shoulder and an additional running lane. To implement such a proposal, a continuous traffic management system would be required on the mainline throughout the construction period so to maintain two lanes of traffic in each direction. Should this option be taken forward to DMRB Stage 3 assessment, significant thought shall be given to construction phasing and the maintaining of access between local and national routes during the construction period.

4.3 North Corridor Option 2

4.3.1 Table 4.4 read in conjunction with Figure 4.6 (Volume 2) provides a description of the North Corridor Option 2 mainline carriageway design.

Table 4.4: Engineering Description of North Corridor Option 2 Mainline

Corridor

Mainline Description

North Corridor Option 2

Mainline

Design Details

  • Route Corridor Length: 7.0km
  • Design Speed: 120kph
  • Dual two lane motorway (D2M) encompassing:
    • 7.3m running carriageway
    • 3.6m hard shoulders (where practicable for future hard shoulder running)
    • 0.7m hardstrips
    • 3.1m central reserve
    • 1.5m verge

Design Geometry

  • Minimum Horizontal Radius = 1020m
  • Minimum Vertical Gradient = 0.7%
  • Maximum Vertical Gradient = 2.4%
  • Minimum Sag Curve Radius = 3700m
  • Minimum Crest Curve Radius = 3700m

Engineering Constraints

  • Existing topography
  • Connection to A90/M90 route corridor
  • Junction provision and side roads connectivity
  • Side road crossings
  • Railway Crossings at Ferrytoll and Inverkeithing
  • Proximity of Rosyth and Inverkeithing
  • Environmentally significant areas (refer to Part 3)
  • Possible future multi-modal developments (LRT, BRT, guided buses or trams)

Mainline Features

4.3.2 A full improvement to North Corridor Option 2 consists of an offline dual two lane motorway connecting the proposed replacement bridge to the M90 north of Masterton Junction. South of Ferrytoll Junction, the mainline shall be implemented as an all purpose carriageway with hard shoulder to maintain cross-Forth access for non-motorway traffic.

4.3.3 Interfacing with the proposed replacement bridge at St Margaret’s Hill, the corridor descends to the west of the existing A90/M90 route corridor at 3% passing through St Margaret’s Marsh on a R1020 metre left hand horizontal curve before crossing Ferry Toll Road, west of Dunfermline Waste Water Treatment Works.

4.3.4 The provision of offline geometry requires a new junction arrangement to be constructed at Ferrytoll, catering for all traffic movements between the mainline and the local road network. A new structural crossing of the Rosyth Dockyard Branch Line Railway will be required in its implementation. The section of the A90/M90 severed by the provision of this route corridor option will continue to be of service as a local distributor road for west Fife, the new junction arrangement at Ferrytoll providing access and egress.

4.3.5 Continuing north, the corridor runs parallel to the existing A90/M90 between Ferrytoll Junction and Castlandhill. The earthworks associated with this section transition from embankment to cutting, with significant cut slopes being required on approach to Castlandhill itself, the corridor climbing at a gradient of between 0.7% and 3%. Passing to the east of Castlandhill Woods the corridor turns northeast by way of a R1440 metre right hand horizontal curve.

4.3.6 Upon reaching Castlandhill, the significant level difference encountered between the proposed vertical geometry and existing ground level requires consideration to be given to a cut and cover solution, minimising as best as possible the visual impact of the corridor on the surrounding area.

4.3.7 Exiting the cut and cover section northeast of Castlandhill, the corridor passes beneath Castlandhill Road before crossing the existing A90/M90 on a structure. Having traversed the A90/M90, the corridor then descends at 3.5% passing over the A921 northwest of Inverkeithing.

4.3.8 The topography of the area through this section transitions from the rugged landscape of coastal hills to a shallow valley in which Belleknowes Industrial Estate and the Fife Circle Railway Line are located. To cater for this sharp change in landscape, the construction of a new viaduct is required carrying the corridor over the A921, through Belleknowes Industrial Estate and over the railway line.

4.3.9 In achieving a connection to the existing M90, the corridor climbs out of the valley at a gradient of 4% turning on a R2800 metre left hand horizontal curve to achieve the necessary approach bearing required to generate a suitable tie in. Passing to the west of The Dales Farmhouse, the provision of a tie in to the M90 at the B916 Aberdour Road requires a significant length of cutting on approach.

4.3.10 Coincidental with the tie in to the existing M90, a simple slip road arrangement facilitates access to the redundant section of the A90/M90 carriageway, providing connectivity to Rosyth, Inverkeithing and Dalgety Bay through the use of the existing Admiralty and Masterton Junctions.

Departures from Standard

4.3.11 At present, no mainline departures from standard have been identified in the development of North Corridor Option 2. A number of existing departures are inherent within the A90/M90 however which would be retained. In addition, there are potential departures within the vicinity of junctions.

4.3.12 Initial discussions have been held with Transport Scotland’s Standards Branch as to the suitability of the design work undertaken to date. Should this option be taken forward to DMRB Stage 3 assessment, the development of the design shall be discussed further with Standards Branch, any departures from standard being highlighted at an early stage.

Junction Provision

4.3.13 Table 4.5 read in conjunction with Figures 4.7 and 4.8 (Volume 2) gives an overview of the indicative junction arrangements developed for North Corridor Option 2.

Table 4.5: Engineering Description of North Corridor Option 2 Junctions

Corridor

Description

North Corridor Option 2

Junction Provision

Ferrytoll Junction

  • New Grade Separated Junction arrangement providing local and non-motorway access.
  • Northbound, new roundabout provided, enabling northbound interaction between the mainline and local roads through new slip arrangements.
    • Mainline Diverge to roundabout and local routes
    • Mainline Diverge to existing A90/M90
    • Mainline Merge – Fork merge arrangement to A90/M90
    • Access maintained to B980, B981 & Ferrytoll Rd through new link roads
  • Southbound, existing roundabout utilised allowing interaction between the mainline, local roads and Ferrytoll Park & Ride through new slip arrangements.
    • Mainline Diverge: Local access taken from M90 via new slip road arrangement sited north of Masterton Junction. Existing A90/M90 access arrangements utilised.
    • Mainline Merge: New link provided to new mainline from existing A90/M90.
    • Access maintained to B980, B981 & Ferry Toll Rd via existing road network and new link road beneath mainline.
  • Bus functionality provided through hard shoulder running on slips.
  • Junction future proofed for the provision of additional transport modes i.e. LRT, BRT, guided buses or trams.
  • Access to Forth Road Bridge maintained through the provision of additional slip road arrangements at Ferrytoll Junction.

Admiralty Junction

  • Existing junction functionality retained between the A90/M90, A985 and A921

Masterton Junction

  • Existing junction functionality retained between the A90/M90 and A823(M)

A90/M90 Link to North Corridor Option 2

  • North facing slip roads provided north of Masterton Junction providing connectivity between existing A90/M90 and North Corridor Option 2.

Topography & Land use

4.3.14 The topography encountered in the provision of North Corridor Option 2 is similar to that experienced in the implementation of North Corridor Option 1, with a mixture of residential, commercial and agriculture land use being prevalent.

4.3.15 To the south, the coastal flats of the Firth of Forth are again the prominent feature with pockets of woodland and St Margaret’s Marsh dominating the northern shoreline.

4.3.16 Continuing north, as the corridor ascends Castlandhill, significant cut slopes and the provision of a cut and cover solution will be required to establish the corridor. The construction of such measures will, require significant excavation to implement.

4.3.17 The route will be on viaduct over Belleknowes Industrial Estate and the construction of the viaduct will impact the A921 and the Fife Circle Railway Line.

4.3.18 The rugged topography associated with the north of Inverkeithing will also be affected with significant earthworks being required in the routing of this option to the east of the existing A90/M90 corridor.

4.3.19 Continuing north where agricultural land use is more prevalent, a further permanent change in topography will occur, the corridor requiring the provision of a significant length of cutting so to tie into the existing M90 north of Masterton Junction.

Geotechnical Summary

4.3.20 North Corridor Option 2 is situated offline from the existing A90/M90 corridor. Therefore, to accommodate the proposed vertical alignment, more extensive earthworks would be required than for North Corridor Option 1.

4.3.21 Until the completion of the ground investigations and associated testing, an assessment of the likely slope angles will not be undertaken. The general design assumptions for slopes at present are that they will not be steeper than 26.6o (1V:2H) for both embankments and cuttings. However, in certain cases these may have to be relaxed to satisfy the stability of the slope. Steeper angles of 60o to 80o (2V:1H - 5V:1H) may be possible in rock depending on rock type, discontinuity orientations, spacing and type/extent of infill material, and groundwater.

4.3.22 The cuttings are likely to be formed predominantly within rock. The excavation of cuttings will produce considerable quantities of excavated material, some of which may be appropriate for re-use within the project earthworks. Rock slope drainage measures such as raking drains and relief drains may be required, as well as standard rock slope stabilisation treatment.

4.3.23 A limit of around 7 metres has been assumed in terms of maximum height/depth of a feature before an interim berm is required. This is for improved stability as well as maintenance access. A berm at the soil/rock contact will also be required for slope stability and drainage.

4.3.24 Where soft alluvial deposits or large thicknesses of glacial till are recorded beneath the footprint of proposed embankments, consideration must be given to avoidance of residual settlement (post construction). This may take the form of ground treatment; including pre-loading with or without band drains and replacement of soft deposits, or programming of construction to allow for settlement to occur.

Geotechnical Summary

4.3.25 Table 4.6, in association with Figure 4.9 (Volume 2), provides an indication of the anticipated earthworks associated with North Corridor Option 2.

Table 4.6: Geotechnical Summary of North Corridor Option 2

Chainage
(m)

Anticipated Critical Section

Height at Critical Section*

Likely Design Angle

Ground Conditions at Critical Section

Groundwater Encountered (bgl)

Remarks

7200m to 7400m

7250m

30.9m

Structure

GL to 5.3m

Made Ground

>2.5m

  

5.3m+

Bedrock (Sandstone)

7400m to 7500m

7400m

28.4m

Embankment 1V:2H / Structure

GL to 1.8m

Made Ground

>3.2m

High embankment, intermediate berms and slope drainage will be required.

1.8m to 12m

Dolerite ‘boulders’

12m to 33.7m

Soft silty clay

33.7m+

Bedrock (Mudstone)

7500m to 7800m

7550m

15.1m

Embankment (West), Cutting (East) 1V:2H

GL to 2.0m

Made Ground

None Encountered

Soil/Rock bench required.

2.0m to 4.00m

Weathered Glacial Till/Glacial Sands and Gravels

4.0m+

Bedrock (Dolerite)

7800m to 8000m

7900m

6.7m

Embankment 1V:2H

GL to 2.0m

Made Ground

13.1m

Majority of embankment low height, where strength of alluvium may decide capping thickness.

2.0m to 4.00m

Alluvium

4.0m+

Bedrock (Dolerite)

8000m to 8400m

8300m

25m

Cutting 1V:2H

GL to 1.2m

Weathered Glacial Till

None Encountered

Steeper cut angle probable in rock.

Intermediate berms.

Rock slope drainage; surface drainage. Rock slope stabilisation measures.

1.2m+

Bedrock (Dolerite)

8400m to 9050m

8700m

26.7m

Cutting 1V:2H

GL to 2m

Weathered Glacial Till

10.5m

Deep cutting will require intermediate berms and slope drainage.

2m to 33.1m

Glacial Till

33.1m +

Bedrock (Mudstone)

Locally at Ch8800 bedrock is present at 6m and 13m

9050m to 9300m

9250m

16.2m

Embankment 1V:2H

GL to 25m

Glacial Till

2.50m

Issues may arise with settlement of deep Glacial Till deposits beneath the embankment.

25m+

Bedrock (Mudstone)

9300m to 9500m

9300m

20m

Embankment 1V:2H

GL to 0.2m

Topsoil

20.1m

0.2m+

Bedrock (Dolerite)

9500m to 9650m

9550

21m

Cutting 1V:2H

GL to 1.0m

Topsoil

None Encountered

Intermediate berms and slope drainage

1.0m+

Bedrock (Sandstone)

9650m to 11100m

9900m

23m

Embankment 1V:2H

GL to 9.80m

Weathered Glacial Till/Glacial Sands and Gravels

Artesian

0.3m above GL

Issues may arise with settlement of the Weathered Glacial Till deposits beneath the embankment.

9.80m+

Bedrock (Dolerite)

11100m to 12100m

11600m

17.8m

Cutting 1V:2H

GL to 2.0m

Weathered Glacial Till

None Encountered

Steeper cut angle probable.

Intermediate berms.

Rock slope drainage; surface drainage.

2.0m to 4.0m

Glacial Till

4.0m+

Bedrock (Limestone/Mudstone/

* - Cutting Depths are based on the centreline long section and the earthworks interface drawings, Figures 4.9a and 4.9b (Volume 2).

Mineworkings

4.3.26 One previously unrecorded coal seam was encountered to the east of Masterton Junction during the ground investigation. The boreholes did not suggest that these seams had been worked at these locations. No mineworkings are recorded to occur beneath North Corridor Option 2. A further assessment of mineworkings would be necessary should this option be taken forward.

Hydrology

4.3.27 Figure 8.1 (Volume 2) details the watercourses within the study area of the Forth Replacement Crossing Project. Further information on hydrology is provided in Part 3, Chapter 8 of this report.

4.3.28 Through the implementation of North Corridor Option 2, Pinkerton Burn flowing north to south from Middlebank, and Brankholm Burn, flowing west to east through Rosyth will require to be re-routed through new structures beneath the proposed mainline carriageway. Both watercourses are tributaries of Keithing Burn.

Structures

4.3.29 The following paragraphs read in conjunction with Figure 4.10 (Volume 2) detail the structural requirements associated with North Corridor Option 2.

Structures 178-1 and 178-2

4.3.30 Structures 178-1 and 178-2 carry the mainline and northbound diverge slip road from the proposed replacement bridge over local access roads and Ferrytoll Junction. Structure 178-1 comprises an eight span structure with an overall approximate length of 950 metres with a maximum span of 90 metres at a varying skew. Structure 178-2 comprises an overall approximate length of 560 metres at a varying skew. Both are proposed as steel/concrete composite construction founded on bored concrete piles. Both structures have very difficult access on side long ground and Structure 178-1 is also highly skewed with bifurcations and varies in width.

Structure 178-5 and 178-6

4.3.31 Structures 178-5 and 178-6 carry the existing A90 over the Ferrytoll Junction. Both structures will be demolished as they are no longer required.

Structures 178-4, 178-7 and 178-12

4.3.32 Structures 178-4 and 178-7 will carry the A90 link road to the proposed replacement bridge over the realigned B981 and the new Ferrytoll roundabout link respectively. Structure 178-12 carries the new mainline over the new Ferrytoll roundabout link. All structures comprise single spans with Structure 178-4 having a span of 30 metres at a skew of 40° and Structures 178-7 and 178-12 having spans of 25 metres at skews of 25°. All structures comprise precast beam and slab construction with structure 178-4 being non-integral and Structures 178-7 and 178-12 being of integral construction. All structures are founded on spread footings.

Structure 178-3

4.3.33 Structure 178-3 will carry the B981 over the Inverkeithing South Junction – Rosyth Dockyard Branch Line Railway from the relocated Ferrytoll roundabout. It is proposed as a single span structure with a span of 15 metres at a skew of 10°. It comprises precast beam and slab integral construction founded on spread footings. The structure will require stringent measures during construction over the railway with disruptive possessions likely to be required.

Structure 178-8

4.3.34 Structure 178-8 will carry a link road from the proposed replacement bridge to the existing A90 northbound over the new mainline. It is proposed as a four span structure with an overall approximate length of 140 metres comprising two spans of 40 metres and two spans of 30 metres at a skew of 60°. It comprises steel/concrete composite construction founded on spread footings. The structure will be of complex design and construction as it is highly skewed, curved in plan and is to be constructed over the existing M90.

Structures 178-9, 178-10, 178-11

4.3.35 Structure 178-9 is the existing Ferrytoll railway tunnel under the existing A90 and the new mainline and its slip roads. It is a single span structure with a span of 4.95 metres and an overall length of approximately 95 metres. Structure 178-10 is an existing structure which carries the B980 over the Inverkeithing South Junction – Rosyth Dockyard Branch Line Railway close to the entrance/exit to the tunnel. It is a single span structure with a maximum span of 5.88 metres.

4.3.36 Both structures 178-9 and 178-10 are of concrete arch integral construction. Structure 178-9 is founded on spread footings; however the foundation type for structure 178-10 is unknown.

4.3.37 Structure 178-11 is a widened section of Structure 178-10. It is a single span structure with a span of 20.5 metres at a skew of 23°. It is of precast beam and slab integral construction founded on spread footings and was built circa 2006.

4.3.38 The intention is that all structures shall be retained for use with North Corridor Option 2.

Structure 135-8

4.3.39 Structure 135-8 will comprise a tunnel from approximately Ch 8550 metres to 8950 metres. Twin tunnels will be constructed, one for southbound and one for northbound traffic with a clear separation of at least 20 metres between them. A tunnel boring machine type excavation would not be appropriate and hence a sequential excavation will be employed. Sprayed concrete, lattice girders and mesh reinforcement will be used for the primary tunnel lining with a cast insitu concrete lining constructed to complete the tunnel lining. Construction operations will need to take cognisance of potential surface settlement during excavation.

Structure 135-1

4.3.40 Structure 135-1 will carry the B980 over the new mainline. It is proposed as a three span structure with an overall approximate length of 91 metres comprising a maximum span of 42 metres at a skew of 40°. It comprises a steel/concrete composite structure founded on bored concrete piles. The structure is on a very high skew which would result in complex design and construction.

Structure 135-2

4.3.41 Structure 135-2 will carry the new mainline over the existing A90. It is proposed as a three span structure with an overall approximate length of 130 metres with a maximum span of 62 metres at a skew of 60°. It comprises a steel/concrete composite structure founded on bored concrete piles. The structure is on a very high skew which would result in complex design and construction.

Structure 136-3

4.3.42 Structure 136-3 will carry the new mainline over the A921 Admiralty Road, Belleknowes Industrial Estate and Inverkeithing Railway Junction. It is proposed as a nine span structure with an overall approximate length of 550 metres with a maximum span of 75 metres. It comprises a steel/concrete composite structure founded on bored concrete piles. The structure may possibly be constructed by incremental launching to minimise disruption to facilities at ground level.

Structure 136-4

4.3.43 Structure 136-4 will be an underpass carrying the new mainline over Masterton Road. It comprises a single span structure with an overall approximate length of 45 metres between headwalls and a clear span length of 9 metres at a skew of 30°. It is proposed as a portal structure with a precast beam deck founded on spread footings.

Structure 179-1

4.3.44 Structure 179-1 will carry the M90 southbound connection to the proposed replacement bridge. It is considered as a five span structure with an overall approximate length of 225 metres comprising three spans of 45 metres and two spans of 40 metres curved in plan. It comprises a steel/concrete composite structure founded on bored concrete piles. The structure will be of complex construction as it is curved in plan and is to be constructed over the existing M90.

Structure 179-2

4.3.45 The reconstructed bridge, Structure 179-2, will carry the B916 over the M90 and new slip roads. It is proposed as a single span structure with a span of 50 metres and comprises a steel/concrete composite integral structure founded on bored concrete piles.

Structures 135-5 and 000-1

4.3.46 Structure 135-5 Dunfermline Wynd Overbridge carries Dunfermline Wynd over the existing A90. It is a three span structure with an overall length of 71.8 metres between abutment centres with a maximum span length of 32.2 metres. It comprises a haunched concrete deck with a voided suspended main span. The piers are founded on spread footings and the abutments on piles. It will be retained.

4.3.47 Structure 000-1, Calais Muir Overbridge, carries a side road over the existing M90 close to Calais Muir Wood. It is a four span structure with an overall skew length of 52.3 metres (between abutment centres) with a maximum span length of 14.8 metres. It is an insitu reinforced concrete slab structure founded on leaf piers and bankseat abutments, all founded on piles. It will be retained.

Public Utilities

4.3.48 North Corridor Option 2 is likely to impact the following public utilities plant:

  • 8no. Crossings of high voltage electric cables at 33Kv (7no. overhead/1no. underground)
  • 12no. Crossing of high voltage electric cable at 11Kv (underground)
  • 1no. Crossings of intermediate pressure gas main (2 to 7 bar pressure)
  • 10no. Crossings of medium pressure gas main (0.75 to 2 bar pressure)
  • 3no. Crossings of trunk water mains

4.3.49 In addition to the above, other small-scale plant is affected such as telecommunication cables, street lighting cables, low-pressure gas pipes and small diameter water supply pipes.

Constructability

4.3.50 Constructed offline, the North Corridor Option 2 mainline does not generate the traffic management issues associated with North Corridor Option 1. For long periods traffic would be able to run unhindered on the existing A90/M90, the new corridor being constructed in isolation. Sustained periods of traffic management would only become a factor where structural crossings and new junction arrangements are required. The construction of Ferrytoll Junction would require significant traffic management over a sustained period.

4.3.51 In the construction of North Corridor Option 2, significant impacts would be experienced to the A921, Belleknowes Industrial Estate and Network Rail’s property located to the north of Inverkeithing. Should this option be taken forward to DMRB Stage 3 assessment, further detailed consideration of this area will be necessary taking into consideration the requirement for significant earthworks and structural provision.

4.4 South Corridor Option 1

4.4.1 Table 4.7 read in conjunction with Figure 4.11 (Volume 2) provides a description of the South Corridor Option 1 mainline carriageway design.

Table 4.7: Engineering Description of South Corridor Option 1 Mainline

Corridor

Description

South Corridor Option 1

Mainline

  • Route Corridor Length: 2.75km
  • Design Speed: 120kph
  • Dual three lane motorway (D3M) cross-section operated as all purpose road
    • 11m running carriageway
    • 3.6m hard shoulders (where practicable for future hard shoulder running)
    • 0.7m hardstrips
    • 3.1m central reserve
    • 1.5m verge

Design Geometry

  • Minimum Horizontal Radius = 720m
  • Minimum Vertical Gradient = 0.5%
  • Maximum Vertical Gradient = 3.0%
  • Maximum Sag Curve Radius = 3700m
  • Minimum Crest Curve Radius = 3700m

Engineering Constraints

  • Existing topography
  • Connection to existing A90 south of the Forth Road Bridge
  • Utilisation of existing roads infrastructure associated with Forth Road Bridge
  • Junction provision and side roads connectivity
  • Location of BP Pipeline
  • Proximity of residential areas
  • Environmentally significant areas (refer to Part 3)
  • Possible future multi-modal developments (LRT, BRT, guided buses or trams)

Mainline Features

4.4.2 A full improvement to South Corridor Option 1 consists of a dual three lane carriageway to motorway standard connecting the proposed replacement bridge to the A90, a strategically important piece of roads infrastructure which currently connects the Forth Road Bridge to Edinburgh and the central Scotland motorway network. The new carriageway will be operated as an all purpose road facilitating cross-Forth access for non-motorway traffic.

4.4.3 The horizontal and vertical geometry of the South Corridor Option 1 has been carefully designed to minimise the number of crossings of the BP Pipeline required in the provision of the corridor.

4.4.4 The BP Pipeline, passing through the fields to the south of the A904, is also situated in close proximity to the northbound verge of the A90. Consultation with BP Oil UK Ltd is ongoing with regards to their requirements for pipeline protection. The required protection measures shall be fully implemented with any route corridor option taken forward for future consideration as part of the DMRB Stage 3 assessment process.

4.4.5 Tying into the A90 east of the A8000 overbridge, South Corridor Option 1 provides enhancements to the existing Scotstoun Junction whilst maintaining northbound access to South Queensferry for traffic on the A90 and the M9 Spur. In addition, an upgrade of M9 Junction 1a is also proposed, with new free flow links providing all movements in all directions between the M9 and the M9 Spur.

4.4.6 The South Corridor Option 1 mainline departs the A90 in a westerly direction, to the south of the A904. Within this area, it is proposed that a new junction be constructed connecting local communities such as Newton and South Queensferry to the proposed replacement bridge, Edinburgh and the central Scotland motorway network.

4.4.7 Beyond this new junction, the corridor swings north towards the Firth of Forth and the proposed replacement bridge. Utilising a R720 metre right hand horizontal curve and a vertical gradient of 3% gradient, the corridor passes beneath the A904 to the west of South Queensferry. In achieving this, significant cut slopes are necessary, a new overbridge being required to carry the A904 over the new mainline carriageway.

4.4.8 On approach to the proposed replacement bridge the horizontal geometry of the corridor straightens, a shallow incline being implemented to facilitate connection to the bridge approach structure.

Departures from Standard

4.4.9 Considering the engineering constraints associated with this corridor, the horizontal and vertical geometry implemented is subject to a number of relaxations from standard for a 120kph design speed.

4.4.10 In general these relaxations are associated with the vertical geometry of the corridor, R10000 metre crest curves being implemented to form an appropriate tie in with the existing A90 and to provide sufficient clearance to the BP Pipeline.

4.4.11 The R720 metre right hand curve located on approach to the crossing of the A904 and the proposed replacement bridge represents a horizontal relaxation of one design speed step below desirable minimum. Whilst permissible in isolation, its provision in combination with a relaxation in vertical curvature, required in the provision of headroom clearance to the A904, results in a Departure from Standard.

4.4.12 Initial discussions have been held with Transport Scotland’s Standards Branch as to the suitability of the design work undertaken to date. Should this option be taken forward to DMRB Stage 3 assessment, the development of the design shall be discussed further with Standards Branch, any departures from standard being highlighted at an early stage.

Junction Provision

4.4.13 Table 4.8 read in conjunction with Figures 4.12 and 4.13 (Volume 2) gives an overview of the indicative junction arrangements developed for South Corridor Option 1.

Table 4.8: Engineering Description of South Corridor Option 1 Junctions

Corridor

Description

South Corridor Option 1

Junction Provision

Echline/Scotstoun Combination Junction

  • Existing Scotstoun Junction utilised with additional functionality provided.
    • Northbound connectivity to A904 and South Queensferry maintained with provision of new link road between M9 Spur and existing Echline Roundabout.
    • Northbound, diverging slip road from A90 to new link northbound provides connection between north of Edinburgh and A904.
    • Reconnection of Forth Road Bridge northbound achieved through forking of proposed link road on approach to existing Echline Junction.
    • Southbound, new link road at Scotstoun Junction provides connection between Forth Road Bridge, M9 Spur and A90.
  • New Grade Separated Echline Junction in combination with Scotstoun Junction improvements maintains all movement functionality south of proposed replacement bridge.
    • Northbound, slip road provided between new roundabout on A904 and mainline, maintaining local cross Forth links.
    • Southbound, simple merge and diverge slip roads provided between mainline and new A904 roundabout facilitating local access for departing bridge traffic.
  • Dedicated HOV lane provided from new Echline Junction to proposed replacement bridge, allowing safe transition between new mainline and the existing dual three lane all purpose A90 where no such functionality exists.

M9 Junction 1a

  • New free flow, all movements junction linking M9 with M9 Spur.
  • East facing functionality retained:
    • Existing loop, facilitating access between M9 Westbound and M9 Spur replaced with simple link, improving junction operation and safety.
    • Existing M9 Spur to M9 Eastbound slip road utilised with localised improvements to entry/exit tapers and nosings.
  • West facing functionality added:
    • New link road provided from M9 Spur to M9 Westbound serving traffic to West Lothian and beyond.
    • New link road provided from M9 Eastbound to M9 Spur serving traffic from West Lothian, relieving pressure on A904.

Topography & Land use

4.4.14 The topography of the area surrounding South Corridor Option 1 encompasses a mixture of residential and agricultural property.

4.4.15 Passing to the south of the A904, the corridor is situated within lowland hill and valley farmland and crosses Dundas Estate.

4.4.16 To the north, situated on the shoreline of the Firth of Forth lies the town of South Queensferry. Sited close to the Forth Road Bridge and the Forth Rail Bridge, South Queensferry is a popular tourist destination and commuter town for Edinburgh, residential property being the predominant land use.

4.4.17 Whilst the topography of the area generally falls towards the Firth of Forth, the fields affected by the corridor to the south of the A904 gently rise from south to north, the A904 being situated on embankment. North of the A904, the land falls sharply towards the Firth of Forth, a steep change in gradient being experienced between Inchgarvie House and Port Edgar.

Geotechnical Summary

4.4.18 The earthworks associated with South Corridor Option 1 comprise relatively shallow embankment to the south of South Queensferry, descending into cutting to pass beneath the A904.

4.4.19 Until the completion of the ground investigations and associated testing, an assessment of the likely slope angles will not be undertaken. The general design assumptions for slopes at present are that they will not be steeper than 26.6o (1V:2H) for both embankments and cuttings. However, in certain cases these may have to be relaxed to satisfy the stability of the slope. Steeper angles of 60 o to 80 o (2V:1H - 5V:1H) may be possible in rock depending on rock type, discontinuity orientations, spacing and type/extent of infill material, and groundwater.

4.4.20 The cutting is likely to be partially formed within glacial deposits, and partially within rock. Rock slope drainage measures such as raking drains and relief drains may be required, as well as standard rock slope stabilisation treatment.

4.4.21 A limit of around 7 metres has been assumed in terms of maximum height/depth of a feature before an interim berm is required. This is for improved stability as well as maintenance access. A berm at the soil/rock contact will also be required for slope stability and drainage.

4.4.22 Where large thicknesses of glacial till are recorded beneath the footprint of proposed embankments, consideration must be given to avoidance of residual settlement (post construction). This is of particular importance in the vicinity of the BP Pipeline, and appropriate pipeline protection measures will be accommodated within the design should this option be taken forward for further assessment.

Geotechnical Summary

4.4.23 Table 4.9, in association with Figure 4.14 (Volume 2), provides an indication of the anticipated earthworks associated with South Corridor Option 1.

Table 4.9: Geotechnical Summary of South Corridor Option 1

Chainage
(m)

Anticipated Critical Section

Height at Critical Section*

Likely Design Angle

Ground Conditions at Critical Section

Groundwater Encountered (bgl)

Remarks

0m to 200m

200m

1.6m

Embankment 1V:2H

GL to 1.7m

Weathered (Cohesive) Glacial Till

14m

Existing A90. Rock not encountered in ground investigation.

1.7m to 3.2m

Granular Glacial Till

3.2m to 23.7m

Cohesive Glacial Till

23.7m

Bedrock (Sandstone)

200m to 475m

400m

2m

Embankment 1V:2H

GL to 3.4m

Weathered Glacial Till

3.2m

Depth to rockhead near Chainage 300m is 30.4mbgl.

3.4m to 10m+

Cohesive Glacial Till

10m+

Anticipated Bedrock (Likely Sandstone)

475m to 575m

500m

0.4m

Cutting 1V:2H

GL to 2.1m

Weathered Glacial Till

2.2m

Depth to rockhead very variable, varies between 1.2mbgl and >33mbgl within 60m.

2.1m to 33m+

Cohesive Glacial Till

33m+

Anticipated Bedrock (Likely Sandstone)

575m to 1000m

700m

3.8m

Embankment 1V:2H

GL to 1.9m

Weathered Glacial Till

4.6m

Rockhead only encountered offline.

1.9m to 4.6m

Cohesive Glacial Till

~4.6m

Anticipated Bedrock (Siltstone)

1000m to 1530m

1300m

5.2m

Embankment 1V:2H

GL to 2.5m

Weathered Glacial Till

14.7m

2.5m to 14.7m

Cohesive Glacial Till

14.7m

Bedrock (Mudstone)

1530m to 1800m

1750m

2.3m

Cutting 1V:2H

GL to 1.5m

Weathered Glacial Till

1.5m

Depth to rockhead very variable. Soft deposits may affect the stability of the cut slopes locally.

1.5m to 8.0m

Cohesive Glacial Till

8.0m

Bedrock (Sandstone)

1800m to 2350m

2100m

11.4m

Cutting 1V:2H

GL to 2.3m

Weathered Glacial Till

1.5m

Depth to rockhead very variable. In-slope drainage and surface drainage may be required. Cohesive Glacial Till present at north end of chainage range. Soft deposits may affect the stability of the cut slopes locally.

Localised perched water anticipated at Ch 2250m. Intermediate berms will be required at 7m height as well as soil / rock contact.

2.3m

Bedrock (Sandstone)

2350m to 2600m

2400m

5.6m

Cutting 1V:2H

GL to 1.9m

Weathered Glacial Till

2.5m

Soft and granular deposits may affect the stability of the cut slopes locally.

1.9m to 7.4m

Cohesive Glacial Till

7.4m to 8.2m

Gravel

8.2m

Bedrock (Dolerite)

2600m to 3150m

-

-

Bridge Approach

GL to 1.5m

Weathered Glacial Till

2.1m

Approach to bridge.

1.5m to 4.5m

Granular Glacial Till

4.5m +

Bedrock (predominantly Sandstone and Dolerite)

* - Cutting Depths are based on the centreline long section and the earthwork interface drawing, Figure 4.14 (Volume 2).

Mineworkings

4.4.24 The majority of the extractable mineral deposits recorded to the south of the Firth of Forth comprise seams of oil shale; however, one coal seam, the Houston Coal, is recorded to occur close to the tie-in between South Corridor Option 1 and the existing A90 near Scotstoun.

4.4.25 No mine-workings are recorded to occur beneath the South Corridor Option 1, either in the coal seam or the oil shales, and the deep boreholes undertaken to date to investigate the recorded seams have not suggested that they have been worked beneath the corridor.

4.4.26 Workings within the Broxburn Shales are recorded in the vicinity of the tie-in between the A90 and M9 Spur close to Dalmeny, and should the proposed junction improvements be required in this area, it is likely that further investigation of the condition of these seams, and possible ground treatment would be required. Some grouting works were undertaken as part of the construction for the M9 Spur Extension; however it is unlikely that the treated zone extends over the area which would be necessary for the junction improvements. A further assessment of mineworkings would be necessary should this option be taken forward.

Hydrology

4.4.27 Figure 8.1 (Volume 2) details the watercourses within the study area of the Forth Replacement Crossing Project. Further information on hydrology is provided in Part 3, Chapter 8 of this report.

4.4.28 Niddry Burn, situated to the south of M9 Junction 1a, crosses the M9 from west to east through an existing culvert. Through the provision of a new junction at this location, it is possible that an extension of this culvert may be required to cater for the provision of the new slip road connecting the M9 westbound carriageway to the M9 Spur.

4.4.29 Swine Burn, located to the north of the M9, flows from west to east with a culvert carrying the watercourse through the area of M9 Junction 1a. It will be necessary for an additional culvert to be constructed beneath the new slip road from the M9 eastbound carriageway to the M9 Spur, requiring a diversion of the watercourse during construction.

4.4.30 Dolphington Burn, located to the south of Scotstoun Junction, will require the provision of an additional watercourse crossing to complement that provided in the construction of the M9 Spur Extension. The new crossing, situated upstream of the existing structure will require a diversion of the watercourse during construction.

4.4.31 Linn Mill Burn, situated to the west of the corridor, is the likely outfall point for the drainage system associated with South Corridor Option 1. Flowing northwards, Linn Mill Burn’s point of source is situated at Totleywells, its outfall to the Firth of Forth being situated at Port Edgar.

Structures

4.4.32 The follow paragraphs read in conjunction with Figure 4.15 (Volume 2) detail the structural requirements associated with South Corridor Option 1.

Structure 167-9

4.4.33 Structure 167-9 is an existing culvert carrying the Niddry Burn under the existing M9. The structure is required to be extended to accommodate the increased width of the road. No information is currently available for the existing culvert at this stage however it is assumed that it can be retained.

Structure 167-10

4.4.34 Structure 167-10 is an existing structure which carries the link road from the westbound carriageway of the M9 to the M9 Spur. This existing structure is no longer required as part of the scheme and will be demolished.

Structure 167-6

4.4.35 Structure 167-6 will carry the M9 Spur southbound, over the M9 and new M9 to M9 Spur link road, providing access to the M9 westbound carriageway. A six span structure is proposed with an overall approximate length of 200 metres comprising two 25 metre spans, two 40 metre spans and two 35 metre spans, curved in plan. It comprises a continuous steel/concrete composite deck with piers founded on bored concrete piles.

Structures 167-8

4.4.36 Structure 167-8 is an existing culvert carrying the M9 eastbound link from the M9 Spur over the Swine Burn. It is a twin barrel rectangular culvert that will be retained for use on the new road network.

Structures 187-5 and 187-8

4.4.37 Structure 187-5 will be a new culvert carrying the Dolphington Burn under a new M9 Spur Extension link road at Scotstoun Junction. A single span structure is proposed with an overall approximate length of 25 metres and a clear span of 3 metres. The culvert shall consist of a precast box type structure.

4.4.38 Structure 187-8 is an existing culvert which carries the existing M9 Spur over Dolphington Burn. This structure requires to be lengthened by approximately 60 metres to accommodate the new link road to the spur. The proposed extension comprises a precast box type structure.

Structures 167-1, 167-3 and 167-5

4.4.39 Structures 167-1, 167-3 and rebuilt structure 167-5 will carry: the M9 westbound to M9 Spur northbound link road under the M9 mainline, M9 westbound to M9 Spur northbound link road over the B9080 and the M9 Spur over the B9080 respectively. They comprise of three single span structures with spans of 30 metres and are of precast beam and slab integral construction. Structures 167-1 and 167-5 will require staged construction and major traffic management as both are being constructed under the existing M9 and M9 Spur respectively. The demolition of 167-5 will also require staged construction and major traffic management.

Structures 167-2 and 167-4

4.4.40 Structures 167-2 and 167-4 will take the form of culverts carrying the Swine Burn under the new link roads at M9 Junction 1a. Both structures will be single span with 167-2 and 167-4 having overall approximate lengths of 22 metres and 40 metres respectively. Each structure has a clear span of 3 metres. The culverts shall consist of precast box type structures.

Structure 167-7

4.4.41 Structure 167-7 will carry the M9 Spur slip road tapers over an existing side road west of M9 Junction 1a. It is an existing two hinged portal single span structure with a span of 10 metres at a skew of 18°.

The existing structure requires to be widened by 10 metres to the south and 5 metres to the north in order to accommodate the increase in road width.

Structure 167-11

4.4.42 Existing structure 167-11, Humbie Railway Bridge, carries the M9 Spur over the Falkirk-Fife Railway Line. It is a single span bridge and has an approximate span of 17 metres at a skew of 40°. It is a prestressed beam and slab structure founded on piles. This structure will be retained for use on the new road network.

Structure 265-4

4.4.43 Structure 265-4 will carry a new link from the existing crossing to the M9 Spur southbound over the existing A90. It comprises a seven span structure with an overall approximate length of 300 metres comprising one span of 60 metres, two 50 metre spans, two spans of 40 metres and two spans of 30 metres on a curved alignment. It consists of steel and concrete composite construction founded on bored concrete piles.

Structures 239-5 to 239-10

4.4.44 Structures 239-5 to 239-10 are pipeline protection structures of similar construction to a culvert, built in order to protect a BP Pipeline which runs adjacent to the proposed location of the new mainline and below a number of slip roads. All of the structures are proposed as single spans with numbers 239-5 to 239-10 having approximate lengths of 80 metres, 190 metres, 90 metres, 150 metres, 225 metres and 40 metres respectively. All structures are proposed as precast concrete portal construction founded on spread footings.

4.4.45 The structural details provided in the protection of the BP Pipeline are indicative at this stage and subject to the approval of BP Oil UK Ltd. Further detailed requirements shall be provided as a part of the DMRB Stage 3 Report should this option be progressed.

Structures 239-1 and 239-2

4.4.46 Structures 239-1 and 239-2 will carry on and off slip roads respectively over the new mainline. Both are three span steel/concrete composite structures founded on spread footings. Structure 239-1 has an overall length of approximately 130 metres comprising a main span of 60 metres and two shorter spans of 35 metres at a skew of 40° and Structure 239-2 has an overall length of approximately 145 metres comprising a main span of 65 metres and two shorter spans of 40 metres at a skew of 50°.

Structure 239-3

4.4.47 Rebuilt structure 239-3 will carry the A8000 over the new mainline and slip roads and will replace the existing structure which is to be demolished. It consists of four spans with an overall length of approximately 155 metres comprising spans of 35 metres, 50 metres, 40 metres and 30 metres at a skew of 10°. It is proposed as a steel/concrete composite construction. Traffic management will be required on the existing A90 during construction and the A8000 is likely to be subject to a significant temporary diversion or a temporary structure may be required.

Structure 187-4

4.4.48 Structure 187-4 is an existing structure which carries Echline Junction over the existing A90. It is a single span structure with a span of 30 metres with no skew. It is an insitu concrete slab structure founded on spread footings. The existing bridge is considered adequate to accommodate new A90 northbound link tie in.

Structures 128-1 and 128-2

4.4.49 Structures 128-1 and 128-2 will carry Builyeon Road and the A904 respectively over the new mainline. Both are three span steel/concrete composite structures of integral construction founded on spread footings. Structure 128-1 will have an overall length of approximately 80 metres comprising a maximum span of 41.5 metres, at a skew of 20°. Structure 128-2 will have an overall length of approximately 72.4 metres comprising a maximum span of 39 metres.

Proposed Replacement Bridge Approach Viaduct – South Corridor Option 1

4.4.50 The approach viaduct structure required in the connecting of the proposed replacement bridge to South Corridor Option 1 shall be designed in tandem with the proposed replacement bridge itself. Details of this structure shall be made available within future reports to be produced by the Jacobs Arup Main Crossing Team, the team responsible for the design of the proposed replacement bridge.

Public Utilities

4.4.51 South Corridor Option 1 is likely to impact the following public utilities plant:

  • 6no. Crossings of BP Pipeline (1370m of protection required)
  • 10no. Crossings of high voltage electric cables at 33Kv (overhead)
  • 13no. Crossing of high voltage electric cable at 11Kv (4no. overhead/9no. underground)
  • 5no. Crossings of medium pressure gas main (0.75 to 2 bar pressure)
  • 7no. Crossings of trunk water mains
  • Possible impact on fibre optic cable at M9 Junction 1a

4.4.52 In addition to the above, other small-scale plant is affected such as telecommunication cables, street lighting cables, low-pressure gas pipes and small diameter water supply pipes.

Constructability

4.4.53 Situated offline, the South Corridor Option 1 mainline will have little impact on the operation of the A90 during the construction period, traffic management only being required in the connection of the new corridor to the existing road network. In the provision of new junction arrangements at M9 Junction 1a and Echline/Scotstoun, appropriate construction phasing will be required to ensure through flow of traffic at all times. Additionally, traffic management and diversionary measures on the A904 may be required whilst a new structure is provided, enabling the South Corridor Option 1 mainline to pass beneath.

4.4.54 With respect to the BP Pipeline, consultation meetings shall continue to be held with BP Oil UK Ltd so that suitable mitigation measures can be encompassed within the design should it be progressed to DMRB Stage 3 assessment.

4.5 South Corridor Option 2

4.5.1 Table 4.10 read in conjunction with Figure 4.16 (Volume 2) provides a description of the South Corridor Option 2 mainline carriageway design.

4.5.2 Table 4.10: Engineering Description of South Corridor Option 2 Mainline

Corridor

Description

South Corridor Option 2

Mainline

  • Route Corridor Length: 5.1km
  • Design Speed: 120kph
  • Dual three lane motorway (D3M)
    • 11m running carriageway
    • 3.6m hard shoulders (where practicable for future hard shoulder running)
    • 0.7m hardstrips
    • 3.1m central reserve
    • 1.5m verge

Design Geometry

  • Minimum Horizontal Radius = 1020m
  • Minimum Vertical Gradient = 2.4%
  • Maximum Vertical Gradient = 2.4%
  • Maximum Sag Curve Radius = 4500m
  • Minimum Crest Curve Radius = 4500m

Engineering Constraints

  • Existing topography
  • Connection to existing M9 east of Winchburgh
  • Junction provision and side roads connectivity
  • Location of BP Pipeline
  • Environmentally significant areas (refer to Part 3)
  • Possible future multi-modal developments (LRT, BRT, guided buses or trams)

Mainline Features

4.5.3 A full improvement to South Corridor Option 2 consists of an offline dual three lane motorway providing a direct connection between the proposed replacement bridge and the central Scotland motorway network via the M9. In providing this connection, a new junction is required providing traffic movements in all directions between the M9, M9 Spur and the proposed replacement bridge. In addition, existing roads infrastructure is upgraded to complement the new provision, Scotstoun Junction being reconstructed to provide access/egress to the west of Edinburgh via the A90.

4.5.4 From the new junction arrangement, situated east of Winchburgh, the corridor departs the M9 on a R1020 metre horizontal curve, requiring new crossings of the B9080 and the Falkirk–Fife Railway Line. To provide sufficient headroom clearance, a gradient of 2.4% is implemented on approach.

4.5.5 Passing to the west of Humbie Reservoir, the corridor is situated on significant embankment. The requirement for structural crossings of existing local roads dictates the vertical geometry through this section.

4.5.6 Continuing north, the corridor crests to the south of its first crossing of Builyeon Road, descending at 2.4% on approach to Westmuir Riding Centre.

4.5.7 Passing to the west of Dundas Estate, the corridor transitions from embankment into cutting, cut slopes in excess of 10 metres being implemented to ensure that sufficient headroom clearance can be generated prior to the second crossing of Builyeon Road. The horizontal geometry of the corridor is fairly straight through this section, matching the bearing of the proposed replacement bridge.

4.5.8 Proceeding north in cutting, the corridor passes beneath the A904. At this point motorway restrictions shall cease allowing non-motorway traffic and local traffic to access the proposed replacement bridge. This will be achieved through a new junction arrangement to the A904, providing north facing slip roads only. Beyond the new junction, the corridor exits cutting to the west of South Queensferry, a gentle incline facilitating connection to the bridge approach structure.

4.5.9 In considering the location of the BP Pipeline, significant changes to the vertical geometry of this corridor would be required in the vicinity of Builyeon Road, with changes in structural provision required. The implementation of such a change would require consideration to be given to the vertical geometry of existing side roads in the area, with Builyeon Road and the A904 most likely to be affected.

Departures from Standard

4.5.10 At present, no mainline departures from standard have been identified in the development of South Corridor Option 2. However, a number of departures may be required in the vicinity of the M9 Junction encompassing Junction 1a.

4.5.11 Initial discussions have been held with Transport Scotland’s Standards Branch as to the suitability of the design work undertaken to date. Should this option be taken forward to DMRB Stage 3 assessment, the development of the design shall be discussed further with Standards Branch, any departures from standard being highlighted at an early stage.

Junction Provision

4.5.12 Table 4.11 read in conjunction with Figures 4.17, 4.18 and 4.19 (Volume 2) gives an overview of the indicative junction arrangements developed for South Corridor Option 2.

Table 4.11: Engineering Description of South Corridor Option 2 Junctions

Corridor

Description

South Corridor Option 2

Junction Provision

M9 Junction

  • New free flow all movements junction provided to M9.
  • West facing slip roads provided facilitating access between the proposed replacement bridge, West Lothian and beyond.
    • Mainline Diverge to M9 Westbound.
    • Mainline Merge from M9 Eastbound.
  • The provision of west facing slip roads to the mainline generates D3M cross section through lane drop/lane gain arrangement.
  • East facing slip roads connecting the corridor to the M9 are provided in tandem with improvements to the existing M9 Junction 1a arrangement.
    • Mainline Diverge to M9 Eastbound.
    • Mainline Merge from M9 Westbound – Link road with forking arrangements to/from M9 Spur.
    • M9 Eastbound Diverge to M9 Spur.
    • M9 Westbound to M9 Spur – Link road generated through fork diverge arrangement associated with South Corridor Option 2 Mainline connection.
    • M9 Spur to South Corridor Option 2 Mainline – Slip Road connected through fast lane merge South Corridor Option 2 mainline interchange link.
    • M9 Spur to M9 Westbound – Slip Road generated through fork diverge of M9 Spur to South Corridor Option 2 Mainline connection.
  • No M9 Spur to M9 Eastbound connection is provided for with this option, traffic wishing to access Newbridge roundabout from South Queensferry/Dalmeny being re-routed via the A8000/B800 and A89.

Scotstoun Junction

  • New free flow, all movements junction.
  • M9 Spur to A90 Eastbound becomes priority traffic route.
  • New M9 Spur to A90 Westbound connectivity provided through new slip arrangements.
    • M9 Spur to A90 Westbound Link
    • A90 Eastbound to M9 Spur Link
  • The existing A90 connections severed by the change in traffic priority are reconnected through the utilisation of the new interchange links proposed.
    • A90 Westbound – Reconnected through new M9 Spur Link.
    • A90 Eastbound – Reconnected through slip road diverge from A90 Eastbound to M9 Spur Link.

A904 Junction

  • New dumbbell roundabout junction arrangement situated at grade with existing A904.
  • Junction required to provide access and egress facility for non-motorway bridge traffic, hence only north facing slip roads are provided.
  • Junction will act as a strategic link for bus traffic.
  • LRT catered for with any future implementation on proposed replacement bridge

Topography & Land use

4.5.13 The topography of the area surrounding South Corridor Option 2 is of an agricultural and residential nature.

To the southeast, the M9 is bounded by disturbed farmland, encompassing oil shale bings at Niddry Castle, Greendykes and Faucheldean. Beyond this lies the village of Winchburgh. To the east and situated on high embankment lies the M9 Spur beyond which lies the town of Kirkliston. To the south of M9 Junction 1a lies Newliston Estate where arable and livestock farming is the predominant land use.

4.5.14 Continuing north, the corridor climbs passing to the west of Humbie Reservoir, impacting upon the long established woodland at Swineburn and Muiriehall. Situated in significant cutting to the east of Westmuir Farm, the corridor then descends towards the Firth of Forth passing to the west of Dundas Estate.

4.5.15 Throughout, the corridor is predominantly situated in lowland hill and valley farmland. South Queensferry is situated to the east on approach to the location of the proposed replacement bridge. On approach to the southern shoreline of the Firth of Forth the rolling hills previously associated with the corridor give way to a more rugged landscape, a steep change in gradient being experienced between Inchgarvie House and Port Edgar.

Geotechnical Summary

4.5.16 The earthworks associated with South Corridor Option 2 comprise an embankment to carry the corridor from the tie-in to the M9, and a long, relatively deep cutting which extends to the tie-in to the proposed replacement bridge approach. This cutting also passes beneath the existing A904.

4.5.17 Until the completion of the ground investigations and associated testing, an assessment of the likely slope angles will not be undertaken. The general design assumptions for slopes at present are that they will not be steeper than 26.6 o (1V:2H) for both embankments and cuttings. However, in certain cases these may have to be relaxed to satisfy the stability of the slope. Steeper angles of 60 o to 80 o (2V:1H - 5V:1H) may be possible in rock depending on rock type, discontinuity orientations, spacing and type/extent of infill material, and groundwater.

4.5.18 A limit of around 7 metres has been assumed in terms of maximum height/depth of a feature before an interim berm is required. This is for improved stability as well as maintenance access. A berm at the soil/rock contact will also be required for slope stability and drainage.

4.5.19 The cutting is likely to be partially formed within glacial deposits, and partially within rock. The excavation of the cutting will produce considerable quantities of excavated material, some of which may be appropriate for re-use within the project earthworks.

Geotechnical Summary

4.5.20 Table 4.12, in association with Figure 4.20 (Volume 2), provides an indication of the anticipated earthworks associated with South Corridor Option 2.

Table 4.12: Geotechnical Summary of South Corridor Option 2

Chainage
(m)

Anticipated Critical Section

Height at Critical Section*

Likely Design Angle

Ground Conditions at Critical Section

Groundwater Encountered (bgl)

Remarks

0m to 700m

300m

~2.0m

Embankment / Cutting 1V:2H

GL to 2.2m

Weathered Glacial Till

None Encountered

No exploratory holes undertaken on existing M9 embankment. Indicative ground conditions of adjacent area provided.

2.2m to 4.2m

Cohesive Glacial Till

4.2m

Bedrock (Mudstone)

700m to 2500m

950m

11.70m

Embankment 1V:2H

GL to 1.5m

Weathered (Cohesive) Glacial Till

5.0m

Many structures within this embankment. Settlement issues may arise due to thick cohesive deposits.

1.5m to 3.5m

Cohesive Glacial Till

3.5m to 5.0m

Granular Glacial Till

5.0m +

Anticipated Bedrock

700m to 2500m

2050m

15.5m

Structure

GL to 1.7m

Granular Deposits

None Encountered

Many structures within this embankment. Thick deposit of cohesive deposits will lead to increased time required for substantial completion of settlement even if amount of total settlement is low.

1.7m to 28.3m

Cohesive Glacial Till

28.3m

Bedrock (Sandstone)

2500m to 4600m

3050m

18.1m

Cutting* 1V:2H

GL to 2m

Weathered Glacial Till

1.1m

23m

Large cutting, will require intermediate berms to aid stability. Gas pocket at rockhead to north at Ch. 3400m. Slope drainage (V-channels) on berms with connecting S-channels.

2m to 20/25m

Cohesive Glacial Till

20/25m

Bedrock (Mudstone/Sandstone)

2500m to 4600m

3800m

14.42m

Cutting* 1V:2H

GL to 2m

Weathered Glacial Till

1.5m

Rock cutting. Will require berms. Rock likely to consist mostly of mudstone, siltstone, and some basalt. Water encountered between 1.5m bgl and exploratory holes being dry. Raking drains and relief drains may be required, plus rock slope stabilisation measures. Steeper angles should be possible.

2m to 6m

Cohesive Glacial Till

6m

Bedrock (Basalt, Siltstone)

(Localised granular deposits, to 4m depth)

4575m to 5050m

-

-

Bridge

GL to 1.5m

Weathered Glacial Till

At Rockhead

Approach to bridge

1.5m to 3.6/7.2m

Cohesive Glacial Till

3.6 to 7.2m

Bedrock (Sandstone, Mudstone, Dolerite)

(Localised granular deposits)

* - Cutting Depths are based on the centreline long section and earthworks interface drawings, Figure 4.20a and 4.20b (Volume 2).

Mineworkings

4.5.21 The majority of the extractable mineral deposits recorded to the south of the Firth of Forth comprise seams of oil shale; however one coal seam, the Houston Coal, is recorded to occur close the existing A90 near Scotstoun.

4.5.22 No mine-workings are recorded to occur beneath the South Corridor Option 2, either in the coal seam or the oil shales, and the deep boreholes undertaken to date to investigate the recorded seams have not suggested that they have been worked beneath the corridor.

4.5.23 Workings within the Broxburn Shales are recorded in the vicinity of the tie-in between the A90 and M9 Spur close to Dalmeny, and should the proposed junction improvements be required in this area, it is likely that further investigation of the condition of these seams, and possible ground treatment would be required. Some grouting works were undertaken as part of the construction for the M9 Spur Extension; however it is unlikely that the treated zone extends over the area which would be necessary for the junction improvements. A further assessment of mineworkings would be necessary should this option be taken forward.

Hydrology

4.5.24 Figure 8.1 (Volume 2) details the watercourses within the study area of the Forth Replacement Crossing Project. Further information on hydrology is provided in Part 3, Chapter 8.

4.5.25 The implementation of new junction arrangements in the vicinity of M9 Junction 1a and Scotstoun Junction may require the extension or replacement of existing culverts / structures at Niddry Burn, Swine Burn and Dolphington Burn. New culverts / structures may also be required.

4.5.26 As outlined with South Corridor Option 1, Linn Mill Burn, situated to the west of the corridor, is a likely outfall point for the drainage system associated with South Corridor Option 2. Flowing northwards, the Linn Mill Burn’s point of source is situated at Totleywells, its outfall to the Firth of Forth being situated at Port Edgar.

Structures

4.5.27 The following paragraphs read in conjunction with Figure 4.21 (Volume 2) detail the structural requirements associated with South Corridor Option 2.

Structure 163-14

4.5.28 Structure 163-14 is a culvert carrying the existing M9 over the Niddry Burn. The structure is required to be extended to accommodate the increased width of the road. No information is currently available for the existing culvert at this stage however it is assumed that it can be retained.

Structure 163-17

4.5.29 Structure 163-17 carries the M9 to M9 Spur slip road over the M9. This existing bridge is not required in the new road layout and as such is to be demolished.

Structure 163-18

4.5.30 Structure 163-18 is an existing culvert carrying the M9 Spur to the M9 eastbound slip over the Swine Burn. It is a single span structure with an overall length of 142 metres with a clear span length of 4.3 metres. It is a twin barrel rectangular culvert that will be retained for use on the new road network.

Structure 163-19

4.5.31 Structure 163-19, Humbie Railway Bridge, carries the M9 Spur over the Falkirk-Fife Railway Line. It is a single span bridge and has an approximate span of 17 metres at a skew of 40°. It is a prestressed beam and slab structure founded on piles. This structure will be retained for use on the new road network.

Structures 94-4, 162-1, 162-2 and 163-13

4.5.32 Structures 94-4, 162-1, 162-2 and 163-13 each consist of seven spans with overall lengths of 270 metres, 240 metres, 280 metres and 282.5 metres respectively. Each structure comprises:

  • 94-4: two spans of 35 metres and five spans of 40 metres
  • 162-1: one span of 20 metres, two spans of 30 metres and four spans of 40 metres
  • 162-2: two spans of 30 metres, three spans of 40 metres and two spans of 50 metres
  • 163-13: two spans of 30 metres, two spans of 40 metres and three spans of 47.5 metres

4.5.33 The structures are of steel/concrete composite construction founded on bored concrete piles and all are curved in plan. Structures 162-2 and 163-13 will require construction over live M9 carriageways.

Structures 162-4, 162-16 and 163-9

4.5.34 Structures 162-4, 162-16 and 163-9 are new single span underpass structures with overall approximate lengths between headwalls of 20 metres, 45 metres and 27 metres respectively. Each structure has a clear span length of 9 metres with 162-4 at a skew of 20° and 162-16 and 163-9 being perpendicular to the carriageway. All three are proposed as portal structures founded on spread footings.

Structure 163-10

4.5.35 Structure 163-10 will carry the M9 mainline over the M9 westbound to M9 Spur northbound link road. It is proposed as a single span structure with a span of 30 metres at a skew of 10°. It comprises precast beam and slab integral construction founded on bored concrete piles. The structure will be built below the existing M9 and will therefore require staged construction and major traffic management.

Structures 163-7, 163-8 and 130-1

4.5.36 Structures 163-7 and 130-1 will carry the M9 westbound to M9 Spur northbound link road and the mainline to the proposed replacement bridge respectively over the B9080. These structures and replacement structure 163-8 are proposed as single span precast beam and slab structures supported on spread footings. Structure numbers 163-7 and 163-8 have spans of 30m and skews of 25° and 0° respectively. Structure 130-1 has a span of 14.3m and a skew of 45°.

4.5.37 Structure 163-8 will require staged reconstruction which will require significant traffic management on the M9 Spur.

Structures 162-5, 163-12 and 163-15

4.5.38 Structures 162-5, 163-12 and 163-15 will take the form of culverts carrying the Swine Burn under new sections of road. All three are proposed as single span structures with overall approximate lengths of 110 metres, 22 metres and 40 metres respectively. Each structure has a clear span length of 3 metres with 162-5 at a skew of 5° and 163-12 and 163-15 at skews of 10°. Precast box type construction is proposed.

Structure 163-11

4.5.39 Structure 163-11 requires to be widened by 10 metres to the south and 5 metres to the north in order to accommodate new slip road arrangements.

Structure 163-6

4.5.40 Structure 163-6 will carry the M9 westbound to the northbound carriageway of the South Corridor Option 2 mainline link over the M9. It comprises a four span structure with an overall approximate length of 180 metres over two spans of 40 metres and two spans of 50 metres at a varying skew. It is proposed as a steel/concrete composite structure founded on bored concrete piles. This structure will require complex design and construction as it is curved in plan and has a very high skew over the existing M9.

Structures 94-7, 94-10, 130-2 and 162-3

4.5.41 Structures 94-7, 94-10, 130-2 and 162-3 are all railway bridges required as part of the scheme.

4.5.42 The reconstructed Structure 94-7 comprises a two span structure with an overall length of 60 metres comprising two spans of 30 metres at a varying skew. It is proposed as a steel/concrete composite structure founded on bored concrete piles.

4.5.43 Structure 94-10 will carry the A90 westbound over the Falkirk–Fife Railway Line and comprises a four span structure with an overall length of 110 metres over two spans of 25 metres and two spans of 30 metres at a varying skew. It is proposed as a steel/concrete composite structure of integral construction founded on bored concrete piles. As the bridge is curved in plan it will add complexity to the design and construction.

4.5.44 Structure 130-2 will carry the mainline over the Falkirk–Fife Railway Line. It consists of a single span structure with a span of 16 metres at a skew of 30° and comprises a precast beam and slab integral structure founded on spread footings.

4.5.45 Structure 162-3 will carry the M9 westbound merge slip road over the Falkirk–Fife Railway Line. It consists of a single span structure with a span of 15 metres at a skew of 30° and comprises a precast beam and slab integral structure founded on bored concrete piles.

4.5.46 All structures will require stringent measures during construction (and demolition of 94-7) over the railway with disruptive possessions likely to be required.

Structures 94-11, 94-12, 94-13 and 130-6

4.5.47 Structures 94-11 to 94-13 and 130-6 are pipeline protection structures of similar construction to a culvert, built in order to protect a BP Pipeline which runs under the South Corridor Option 2 mainline and below Scotstoun Junction. All of the structures are considered as having single spans of 5m with approximate overall lengths of 80 metres, 35 metres, 42 metres and 100 metres respectively. All structures are proposed as precast portal construction founded on spread footings.

4.5.48 The structural details provided in the protection of the BP Pipeline are indicative at this stage and subject to the approval of BP Oil UK Ltd. Further detailed requirements shall be provided as a part of the DMRB Stage 3 Report should this option be progressed.

Structures 130-3, 130-4 and 213-1

4.5.49 Structures 130-3, 130-4 and 213-1 will carry side roads and the A904 over the mainline to the proposed replacement bridge respectively. All three structures comprise three spans with maximum span lengths of 35.7 metres at a skew of 15°, 57.3 metres at a skew of 53° and 38.6 metres at a skew of 25° respectively. The bridges are proposed as steel/concrete composite structures with structures 130-3 and 213-1 being of integral construction and structure 130-4 of non-integral construction. All three structures are founded on spread footings.

Structures 94-1, 94-2 and 94-3

4.5.50 Structures 94-1, 94-2 and 94-3 will take the form of culverts carrying the Dolphington Burn under the Scotstoun Junction. All three are proposed as single span structures having overall approximate lengths of 30 metres, 53 metres and 55 metres respectively. Each structure has a clear span length of 3 metres at a skew of 20°. All structures are proposed as precast boxes founded on spread footings.

Structure 94-5

4.5.51 Structure 94-5 carries the M9 Spur link road over the A90 westbound. This is an existing structure that was constructed as part of the M9 Spur Extension contract. No information is available for this bridge at this stage however it is assumed that it can be retained.

Structure 94-6

4.5.52 Structure 94-6 will carry the M9 Spur southbound link road over the M9 Spur mainline. It is proposed as a three span structure with an overall length of 125 metres comprising two spans of 37.5 metres and one span of 50 metres. It comprises a steel/concrete composite structure founded on bored concrete piles. The proposed structure is likely to require complex design and construction as it is curved in plan.

Structure 94-8

4.5.53 Existing structure 94-8 carries the A90 over Standingstane Road. It is an insitu slab structure with a span of 32.4 metres at a skew of 10° founded on spread footings. Very little record information is available for this structure and however it is assumed that the bridge will be retained for use in the new road network.

Structure 94-9

4.5.54 Structure 94-9 will carry the A90 westbound slip road over Standingstane Road and will effectively widen the existing adjacent A90 bridge (Structure 94-8). It is proposed as a single span structure with a span of 20 metres. It comprises a precast beam and slab structure of integral construction founded on bored concrete piles.

Proposed Replacement Bridge Approach Viaduct – South Corridor Option 2

4.5.55 The approach viaduct structure required in the connecting of the proposed replacement bridge to South Corridor Option 2 shall be designed in tandem with the proposed replacement bridge itself. Details of this structure shall be made available within future reports to be produced by the Jacobs Arup Main Crossing Team, the team responsible for the design of the proposed replacement bridge.

Public Utilities

4.5.56 South Corridor Option 2 is likely to impact the following public utilities plant:

  • 5no. crossings of BP Pipeline (1370m of protection required)
  • 5no. crossings of high voltage electric cables at 33Kv (4no. overhead/1no. underground)
  • 9no. crossing of high voltage electric cables at 11Kv (6no. overhead/3no. underground)
  • 12no. crossings of high pressure gas main (7 bar pressure)
  • 2no. crossings of medium pressure gas main (0.75 to 2 bar pressure)
  • 4no. crossings of trunk water mains
  • Possible impact on fibre optic cable at M9 Junction 1a

4.5.57 In addition to the above, other small-scale plant is affected such as telecommunication cables, street lighting cables, low-pressure gas pipes and small diameter water supply pipes.

Constructability

4.5.58 Situated offline, the South Corridor Option 2 mainline will have little impact on the operation of the M9 during the construction period. Traffic management and diversionary measures will be required in the continued operation of local roads such as the A904 and Builyeon Road during construction. In the provision of the new junction arrangements, appropriate construction phasing and traffic management will be required, ensuring that the through flow of traffic can be maintained at all times. In addition, alternative means of access may require consideration insuring that connectivity is maintained between Edinburgh, the Lothians and Fife.

4.5.59 With respect to the BP Pipeline, consultation meetings shall continue to be held with BP Oil UK Ltd so that suitable mitigation measures can be encompassed within the design should it be progressed to DMRB Stage 3 assessment.

4.6 References

The Highways Agency. The Design Manual for Roads and Bridges (May 2008)

Transport Scotland. Structures As-Built Record Information

The City of Edinburgh Council. Structures As-Built Record Information

Fife Council. Structures As-Built Record Information

Public Utilities Information sourced in accordance with New Roads and Street Works Act (NRSWA 1991)