APPENDIX C - ASSESSMENT OF CORRIDOR B
C1 DESCRIPTION OF CORRIDOR
Corridor B is the second of the options to be assessed (taken in order from the west). It is shown in Drawing Number. 49550/G/02, and an extract is given below showing the corridor. It is defined at its western boundary by the oil pipeline which crosses the Firth between Bo’ness and Torry Bay. The eastern boundary of this corridor is formed by the gas pipelines which cross the Firth between the area west of Blackness Bay and Ironmill Bay
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C2 INFLUENCE OF GEOLOGY
East of Grangemouth, between Preston Island to the north and Bo'ness to the south, it is suggested that rockhead plunges to an anticipated depth of 190m in the middle of the Forth. The maximum depth to rockhead is anticipated to decrease eastwards, although conjectural depths have not been mapped.
The log of one borehole in Corridor B, near the northern edge of the current shipping channel, was extended to over 100m without reaching rockhead. This suggests that in this area there is generally a considerable depth of sediment. In this corridor the overlying sediments are also classified as ranging from fair to unpredictable. In the absence of more detailed information, the sediments are judged unsuitable as founding strata for the main towers of a large suspension bridge. A cross section of the Firth of Forth within this corridor has been prepared to illustrate the approximate geology. This has been done using available information and is shown in Figure C.1 below. Figure: C.1 Geological Cross-Section at Alignment BB1
C3 TRANSPORT PLANNING
A test of Corridor B’s operational performance has been undertaken using the TMfS. This test is representative of both potential tunnel and bridge options in this corridor. In this test the crossing is connected to the M9 at Junction 3 (Linlithgow). On the north side of the Forth, it connects to the A985 to the west of Cairneyhill. At this point options are available for the subsequent connection to the M90 corridor.
Two options have been considered for the connection to the strategic road network in Fife. The first involves upgrading the A985 eastwards to the junction with the A823(M) as was assumed for Corridor A. The other option creates a new bypass around the north of Dunfermline joining the M90 at Hill of Beith. For the purposes of the modelling tests the former option was used as it was considered that this would meet the demands of the expected users better.
This test has been run in two different scenarios. The first assumes that the new crossing is simply added to the existing network and, working with the existing Forth Road Bridge, there are, consequently, two crossings available to vehicles.
The performance of Corridor B in this instance is relatively poor. Although this corridor is closer to the existing Forth Road Bridge than Corridor A, it is still some distance from the existing Forth Road Bridge. Once again the results from the TMfS reflect this. In the first model scenario around eight per cent of traffic diverts from the existing Forth Road Bridge in each of the three forecast years.
The second scenario modelled assumes that the existing Forth Road Bridge is closed to all traffic and therefore only the new crossing is available for cross Forth trips. This latter case is representative of the situation that might exist should the existing bridge be closed for maintenance purposes. This test has been run for 2012 only.
In the scenario when only this new corridor is available, there is an increase of one per cent total daily vehicle hours and four per cent increase in daily vehicle kilometres across the network. This increase is unsurprising given the extra distance that all vehicles are forced to travel and the additional time incurred as a consequence.
It is considered, as a consequence of these results, that Corridor B would have little value in providing support to the Forth Road Bridge during periods of major maintenance. As such it would not satisfy some of the key objectives identified for the study.
The origins of southbound peak hour traffic on the existing bridge showed that 19 per cent came from the M90 north of Junction 3 (Halbeath) 23 per cent came from the A92 East Fife Distributor Road, 29 per cent came from Dunfermline town, 20 per cent came from the south Fife coastal routes and five per cent from Rosyth. More importantly the destinations of this traffic saw only three per cent heading for the M9 corridor and 19 per cent for the M8 corridor. It is therefore not surprising that this corridor does not adequately cater for traffic movements.
With both crossings available (the first scenario) the daily traffic flow on the Forth Road Bridge is envisaged to be around 67,000 in 2012, rising to 74,000 in 2022. Given these levels of increase, it is clear that the objective of maintaining cross Forth transport links to at least the level of service offered in 2006 would not be met should a new crossing be provided in Corridor B.
The increase in total distance travelled and extra travel time incurred during closure of the Forth Road Bridge would also result in additional economic costs. In addition, there would be consequential environmental impacts resulting from the additional distance travelled.
Furthermore, although this corridor is closer to the Forth Road Bridge and the Forth Bridge than Corridor A, it is still remote from the main public transport routes across the Forth. The opportunity to integrate enhanced public transport services into a new crossing on Corridor B would be reduced as a consequence. There would be little prospect of new LRT modes being usefully incorporated into a crossing in this corridor. As with all the corridors public transport services could be given priority on the existing Forth Road Bridge.
In summary, therefore, Corridor B performs poorly against the transport planning objectives for this study. It is not recommended for further consideration.
C4 BRIDGE CROSSING OPTIONS
C4.1 Detailed Summary of Constraints
Along the north shore within Corridor B, the Fife coast is dominated by large areas of mudflats extending east from Preston Island through Torry Bay. This area is a SSSI and also a SPA. Given their designations, these environmental features represent a major constraint to construction. A firing range protected area adjacent to Crombie Jetty is also located on the north shore. This extends well into the Firth and areas of land in possession by the MOD. These areas also represent a major constraint to construction.
Along the south shore, the town of Bo’ness occupies the potential landing sites in the western part of the corridor. East of Bo’ness, the mudflats which exist along the shore are designated as a SSSI and a SPA. Immediately inland of Bo’ness and the mudflats are several Scheduled Ancient Monuments (SAMs) including the Roman Fort at Carriden, Muirhouses Roman Temporary Camp and Carriden Fort. These mark parts of the Antonine Wall, which runs east-west through the area. It is possible that the Antonine Wall will be listed as a World Heritage site, with consequent changes in its status and protection. The combination of urban, environmental and historic buildings represent major constraints to construction in the area to the southern end of Corridor B.
Within the Firth, the main navigational channel is located closer to the north shore. Information received from the Forth Ports PLC indicates that the width of the channel in this area is 450m. Within the navigation channel the water depth is a maximum of 14 metres. From admiralty charts, it can be seen that there are six mooring circles located near the middle of the Firth. These represent potential constraints to any crossing in this location.
The location of the oil and gas pipelines around the line of Corridor B has been determined using the current admiralty charts. The accuracy of the locations of these pipelines is not absolutely known and it has been assumed that constructing foundations close to the pipelines would not be permitted due to the high risk of damage. Therefore, these pipelines are considered to be major constraints on the location of a bridge crossing in this corridor.
C4.2 Bridge Option (Refer to Drawing 49550/B/02)
Several bridge alignments have been reviewed to determine if it is possible to construct a bridge crossing within Corridor B.
The alignment was initially selected as it represented a relatively short crossing of the Firth. It had the advantage of avoiding the eastern extremity of Bo’ness. This alignment also had a minimum likely impact on the SSSI and SPAs on both sides of the Firth. On the southern landfall, the alignment of the bridge approach viaduct is located between Muirhouses and the Fort at Carriden. At the north landfall the crossing passes close to Crombie Point.
Although the alignment avoids the SAMs and minimises the impact on the SSSI and SPA, it was considered that the environmental impact during construction and operation would not be acceptable due to the damage that would occur. It is possible to provide curved alignments for the approach viaducts such that the viaduct avoids the SAMs but this will increase the complexity and cost.
Possible schemes for the bridge superstructure were initially considered on the assumption that ground conditions would be adequate to support piers and other structural elements. Following consideration, it was concluded that a possible construction form for this alignment would consist of a suspension bridge with a main span of approximately 1500m. This would offer the potential of spanning over the navigation channel and the mooring circles. It has been assumed, at this stage, that it would not be permissible to construct bridge piers within the mooring circle zone. The remainder of the crossing would consist of multi-span approach viaducts built over the mudflats and curved as appropriate to avoid or minimise impact on the SAMs.
From a review of the geological data available (summarised in Figure C.1), it is possible that the rockhead is approximately 80 metres below water level at the location of the proposed main towers. It is considered impractical to found on the bedrock at this level, as limits reached on other construction schemes have not attained these depths. As noted in section C2, in the absence of more detailed information, the overlying sediments have been judged unsuitable as founding materials for the main towers of a suspension bridge of the size required in this corridor. It is considered extremely unlikely that such a bridge could be provided without incurring major cost and risk.
Optionally it may be preferable to increase the main span to about 2000m. This would offer the possibility of placing the tower foundations on bedrock at depths of about 30m. However, some form of ground investigation would be required to obtain detailed information regarding bedrock depths and the nature of the sediments in this
locality. A span of 2000m would make any suspension crossing on this corridor the longest suspension bridge in the world.
Multi-span cable stay options were also considered for this alignment. The maximum spans of this envisaged crossing would be 750m. However, for such a crossing the central pier would need to be founded near the middle of the Firth, where the deepest water is likely to be encountered. Lengthening the span, even towards the practical limit of cable stayed structures would not overcome the need to site the central pier in deep water.
For a central pier located in the middle of the Firth, it has been concluded that bedrock level would be in excess of 100m. Therefore, it is considered both uneconomic and unfeasible to construct a pier that would be sufficiently robust to support the bridge spans and to withstand ship impact at this location.
C4.3 Risks Associated with Bridge Crossing in Corridor B
The risks associated with the bridge option in Corridor B are as follows:
• The depth to bedrock level is not known. However, it is likely that the bedrock level is excessively deep (over 100m), so ruling out any central pier. In addition, the overlying sediments are likely to be too soft to support foundations adequate to permit the construction of a large span suspension bridge; • Proximity to MOD land near Crombie Point. An allowance has been made in the selection of this alignment to avoid the MOD land, although it may be necessary to move the alignment further to the west. This would increase the length of the approach viaducts, increase the cost and lead to an increased impact on the SSSI; • Proximity to Scheduled Ancient Monuments (SAMs) on the south shore, in particular, the Antonine Wall, which would limit potential bridge landing sites and connections to the wider transport network. • Proximity to the eastern edge of Bo’ness. This could lead to objections from residents and local businesses possibly resulting in relocating the bridge landfall further east. This, in turn, would lead to longer approach viaducts, increased impact on the SSSI and increased cost; • Aerodynamic stability of a large span. This risk could be eliminated at the design stage through wind tunnel testing and analysis. There is a small risk that the design would lead to an increase in the width of the bridge deck and hence an increase in the cost over that likely to be economic for the benefits gained;and • The presence of the oil pipeline on the south shore between Kinneil and Dalmeny represents a risk to construction. The exact location would need to be determined and adequately protected on site for all envisaged loads during and after construction.
C4.5 Costing
Given the very considerable difficulties of providing a cable stayed bridge in this corridor, a preliminary comparative costing exercise has been carried out for the suspension bridge option. A bridge crossing of this type would be approximately 1.6 times that of the cheapest crossing option.
C5 TUNNEL CROSSING OPTIONS
Tunnelling in Corridor B would use the bored method. Tunnelling beneath Bo’ness would be undesirable as it is both unclear what the ground conditions under the town are like and what the impact on the overlying structures might be. The potential for settlement and other forms of impact cannot be assessed. Tunnelling under the MOD facility south of Crombie is also considered undesirable, both from a consent stand point and considering the potentially hazardous nature of the site.
A tunnel alignment could cross the Firth east or west of the MOD facility. To cross the Forth to the west, the alignment would have to cross the shore at Crombie Point, go under the mid-channel anchorages and enter the south shore at Carriden, heading for Junction 3 of the M9.
A more direct route would be to cross the north shore at Aberlyn. The gas pipelines in the area make settlement an issue to be managed, however, at this point, a bored tunnel would be fairly deep and is likely to be in rock.
The northern shoreline is relatively flat towards the A823(M). A portal, worksite and toll plaza area could be established between Leckerstone and the A823(M) junction at St. Margaret’s Stone. On the south shore the ground rises steeply from the Forth. To reach Junction 3 of the M9, the alignment must climb to approximately 60m AOD. This may require extra lengths of tunnelling at three per cent or require a local gradient increase. There would be limited space for a tolling facility on the south shore. Bi-directional or single-way tolling could probably be positioned closer to the A823(M) at St. Margaret’s Stone.
The length of tunnel required for this alignment would be approximately 10km, depending on local ground conditions at the portal locations.
C6 NETWORK LINKAGES
C6.1 Bridge Crossing Option (Refer to Drawing 49550/N/01)
The southern landfall for Corridor B lies to the east of Bo’ness. The proposed link road would head south to connect with the M9 at Junction 3 (approximately 2.75km away). It would cross the A904 to the east of its junction with the A993. A new interchange could be constructed at this location, to serve Bo’ness and the existing minor roads (B903, B9109 and the A904 to the east), in combination with a new all movement junction at the site of Junction 3. This latter junction would replace the current eastbound facing half-diamond junction with the M9. However, the interchange at the A904 could be omitted at the expense of a more complicated arrangement based on a remodelled Junction 3 which would provide for local and trunk road connections.
Whilst the new interchange at Junction 3 would serve both east and west bound motorway traffic, non-motorway traffic would use the existing A904 to the east. Westbound non-motorway traffic would be required to travel through Bo’ness on the A993/A905 route or alternatively route through Linlithgow using the A904/A803.
The northern landfall lies to the south-east of Torryburn. Tying into the motorway network from this location would prove to be expensive due to the length of new or improved carriageway required to reach the M90.
One solution to allow traffic to travel towards Kincardine to the west and Rosyth/Dunfermline to the east would be to provide a new interchange close to the location of the existing roundabout at the A985/A994/B9037 near Cairneyhill. Although the presence of the railway close to this location would make this problematic, it is likely that a satisfactory solution can be provided. It is considered that this interchange, together with the existing A985, would result in adequate provision for westbound traffic.
For traffic heading to the north and east the existing road network would be inadequate, with new build or significant upgrading being required to provide adequate capacity. This could be achieved by substantial upgrading of the existing single carriageway A985 for a distance of 10km to M90 Junction 1 or a 9km upgrade to the junction with the B980. Traffic could then use the two lane dual B980 to access the A823(M) and hence Junction 2 of the M90.
Alternatively, a link road could be constructed to tie into the M90 north of Junction 3. It is likely that this link would be in excess of 12km in length and would require the additional expense of a new junction on the M90. However, it could relieve some pressure on the existing routes in the Dunfermline/Rosyth area. There is, in principle, sufficient distance between Junctions 3 and 4 on the M90 to achieve acceptable weaving lengths between the existing and new junctions. Interchanges could also be provided where the new link road crossed the A907 and A823 if this was shown to be of benefit to traffic and cost effective. Alternatively, the link road could cross these routes and provide no direct linkage to either.
There is a high voltage electricity line running approximately parallel to the A907 where the proposed link road would cross. It should be possible to avoid this and, if the road could be aligned to be in sufficient cutting to provide adequate headroom, there may be no need to divert the transmission line.
Traffic heading west would use the existing A985. Further traffic modelling would identify if the A985 requires upgrading to cope with the expected traffic volumes.
The estimated construction cost includes new junctions on the M9, the A985 and the M90 and excludes the upgrade of the A985 and junctions on the A904, A907 and A823.
C7 ENVIRONMENT
C7.1 Introduction
In this section the environmental constraints have been identified for this corridor. These are based on international, national and local designations, which are shown in Figure C 2. In addition, potential environmental effects that are not related to designations in this area, such as air quality and community impacts (incorporating visual amenity and noise) are discussed briefly. Comparisons between corridors have been undertaken on a qualitative basis, concentrating mainly on whether any designated sites are likely to be affected by the proposals. These various designations are listed within Tables C.1 to C.2.
The corridor is assessed for its impact on each of:
• ecology;
• landscape;
• archaeology and cultural heritage;
• communities;
• air quality; and
• planning designations.
C7.2 Ecology
The northern landfall of this corridor lies within the Firth of Forth SPA (also Ramsar and SSSI) and is also designated as Torry Bay LNR. The southern end of the corridor includes a small area of the Firth of Forth SPA/Ramsar/SSSI at the western edge of Blackness Bay. Areas of mudflat and rocks are present on both landfalls with strandline vegetation. There are also small beds of eelgrass (Zostera species) on the soft mud.
The viaduct required to approach the possible bridge crosses the intertidal zone and the designated mudflats on the northern shore of the Firth. This would result in loss of habitat. However, on the southern shore, such direct loss of habitat within the SPA may be avoided by detailed positioning of the route. This may still lead to indirect impacts on the SPA such as disturbance.
Townhill Country Park lies on the northern outskirts of Dunfermline and is within 100m of the likely route corridor. The Country Park has a purpose built water ski centre on the loch and is a focus for outdoor recreation. The connecting route to the M90 may have indirect impacts upon the setting of the Country Park. Mitigation may be possible by locating the route further northwards and by landscape planting between.
Non-statutory sites within the corridor include a number of woodlands listed on the Ancient Woodland Inventory. Detailed positioning of the connecting route may be able to avoid most of these, thus eliminating direct impact. However, the ancient,
semi-natural Shore Wood straddles the corridor. This reduces the potential for avoidance of these woodland areas. Inzievar Wood lies near the village of Oakley and it falls within the 1km zone of route corridor. Part of this site is a Woodland Trust Reserve and it has high level of public access and community involvement. The final position of the route would determine the level of impact and potential for mitigating indirect impacts.
The extended link road into the motorway to the north increases the potential impact of this route on non statutory sites, in particular on the local woodland resource listed in the Ancient Woodland Inventory. The potential impact on protected species also needs to be considered with regard to the fragmentation and isolation of habitat of red squirrel, badger and otter in particular. The careful design of bridges and other structures on the link road is, in principle, possible. This offers some opportunity to maintain the continuity of river corridors and wildlife bridges.
C7.3 Landscape
Nationally Protected Sites
Inventory of Gardens and Designed Landscapes: There are no sites on the Inventory Gardens and Designed Landscapes (GDLs) within Corridor B.
Locally Protected Sites
Areas of Great Landscape Value / Areas of Outstanding Landscape Quality: There are no AGLVs / AOLQs within Corridor B.
Greenbelt: Areas of Greenbelt can come under considerable pressure as economic growth demands more land to be released for housing other forms of development. The southern end of Corridor B crosses an area of Greenbelt located to the south east of Bo’ness.
C7.4 Archaeology and Cultural Heritage
Scheduled Ancient Monuments
There are a number of SAMs within the route corridor and these are listed in Table C.1 below.
Table C.1: Corridor B - Scheduled Ancient Monuments
Council Area Scheduled Ancient Monuments
Fife Enclosed settlement and souterrain NE of Glenmoy
Fife Tuilyies, stone setting, Torryburn, Fife
Fife Crombie Old Parish Church, Craigflower Estate, Torryburn
Falkirk Antonine Wall, Carriden House, Roman Fort
Falkirk Church and burial ground 20m sw of Carriden House
Falkirk Mound 300m ssw of Carriden House
Falkirk Muirhouses, Roman camp 270m nw of Antonine Wall
Falkirk Palisaded homestead 350m ssw of Bonhard House
Falkirk Enclosure 500m ssw of Bonhard House
Falkirk Enclosure 250m wsw of Stacks
Falkirk Enclosure 650m ne of Walton
Listed Buildings
Within Corridor B there are 56 listed buildings, most of which are within urban centres although there are some spread throughout the countryside. However, there are two listed buildings that fall beneath the centre line of the route corridor as listed on Table C.2.
Table C.2: Corridor B – Listed Buildings
Council Listed Building Category Area
Fife Torryburn, Craigflower Estate, Stripeside Category B House
Fife Crombie Point House Category C(S)
Conservation Areas / Heritage Conservation
Provision for conservation areas is also defined by the Planning (Listed Buildings and conservation areas) (Scotland) Act 1997 and although there are Conservation Areas in the vicinity (e.g. at Linlithgow) there are none immediately within the corridor.
C7.5 Community Impacts
Effects on communities and scattered dwellings could take the form of impacts on visual amenity, noise impacts and changes in land use or land take. This section identifies the settlements and scattered dwellings that are located on the centre line of Corridor B and any other significant settlements or properties within the corridor.
Significant settlements and dwellings located within Corridor B include:
• The outskirts of Bo’ness;
• East Bonhard Farm
• Bankhead Farm;
• Torryburn;
• Cairneyhill;
• Carnock; and
• The outer fringes of Dunfermline
There are significant populations on both sides of the corridor particularly on the north as a result on the length of the road network tie in, which is the longest of all of the options discussed in this report. As such there is significant potential for permanent impacts associated with noise and visual amenity, including the direct loss of dwellings, for example at Muirhouses by Bo’ness.
C7.6 Air Quality
Construction of a new crossing of the Firth of Forth will have local and global air quality impacts. Introducing a new road into an area is likely to increase the amount of traffic emissions and therefore cause a localised decrease in air quality. In addition, increasing capacity of the road network by construction of an additional crossing is likely to encourage increased road travel, and this, in combination with the length of new road that this option requires, means that there is likely to be an increase in global CO2 emissions
However the inclusion of the Complementary Measures such as improved public transport services and HOV within the overall strategy will assist in minimising the overall increase.
C7.7 Planning Designations
There are no housing proposals close to the centre line of the corridor. There are some proposals within Torryburn and Cairneyhill at the northern end of the corridor, in addition to some proposals within Bo’ness.
C7.8 Environmental Conclusions
This section of the report summarises the potential environmental constraints present within Corridor B. The baseline study undertaken has found a wide variety of designations, some of which pose more of a constraint to the proposed crossing than others.
The Firth of Forth SPA (which is also a Ramsar site and a SSSI) represents an overriding constraint on the northern and, to a lesser degree, southern fringes of the Firth. It is afforded the highest level of protection in the UK and there is a presumption against causing adverse impact unless the development is of over riding public interest and there are no alternatives. In addition, any impacts to the qualifying bird species using the Firth outwith the SPA may impact on the ecological integrity of the SPA.
Other significant constraints comprise the SAMs in the vicinity of the Antonine Wall at the southern end of the corridor. In addition, some areas of Ancient Woodland and listed buildings would be affected by this corridor.
Construction of a bridge in this area would impact on local communities and on visual amenity as well as introducing a new noise source to the area. A bridge is also likely to reduce local air quality as well as contributing to increased global CO2 due to overall increases in traffic across the Forth.
C8 CONCLUSION
Corridor B has performed in a broadly similar manner to Corridor A. It generally performs poorly when assessed against the objectives.
A suitable structure can be provided in the form of a suspension bridge with a main span of 1500m. However, the cost is likely to be 1.6 times the cheapest crossing
option considered. In addition, this crossing is likely to have significant environmental impacts on people and the natural and built environment.
A tunnel option in this corridor would be around 10km long. This has not been costed or assessed for its environmental impact due to the poor performance against the objectives.
Figure C.2 – Corridor B – Bridge Option