a180 eastbound diverge and westbound merge layout … igem/td/1 edition 5 (2008) - steel pipelines...

Planning Act 2008

Infrastructure Planning (Applications: Prescribed Forms and Procedure)

Regulations 2009

Regulation Number: n/a

Author: Highways Agency & Jacobs

Document Reference: TR010007/EX/R17/006

Revision Date Description

0 4 July 2014 For consultation with interested parties.

A180 Eastbound Diverge and Westbound Merge Layout Alteration

A160/A180 Port of Immingham Improvement

A160/A180 Port of Immingham Improvement A180 Eastbound Diverge and Westbound Merge

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Contents

1 Introduction ............................................................................................................. 1

2 National Grid Transmission Feeder 9 .................................................................... 1

2.1 Previous Engagement ............................................................................................... 1

2.2 Pipeline Design Standards......................................................................................... 1

2.3 Recent Developments ............................................................................................... 3

3 Design Development ............................................................................................... 3

3.1 A180 Eastbound Diverge ........................................................................................... 3

3.2 A180 Westbound Merge ............................................................................................ 4

4 Environmental Impact Assessment ....................................................................... 4

5 Conclusion ............................................................................................................... 6

Appendices

Appendix A A180 Eastbound Diverge and Westbound Merge Layouts


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1 Introduction

1.1.1 The design of the A160/A180 Port of Immingham Improvement project includes a new junction to replace the existing Brocklesby Interchange. This new junction would include a new roundabout, which is proposed to allow all movements to and from the A160 and A180 via two new on-slip roads and two new off-slip roads. The layout of the proposed Brocklesby Interchange is shown on the Engineering Drawings (document reference: TR010007/APP/23.1(B and C) within the Development Consent Order (DCO) application which was submitted in January 2014.

1.1.2 Previous liaison between the Highways Agency and National Grid Transmission (NGT) has highlighted the presence of a high pressure gas pipeline in the vicinity of Brocklesby Interchange. This pipeline, referred to as Feeder 9, runs north/south, and crosses the existing A180 approximately 330m west of the existing overbridge at Brocklesby Interchange. This lies directly beneath the proposed A180 eastbound diverge and A180 westbound merge, both of which were proposed to be improved as part of the project design as proposed within the DCO application.

1.1.3 This report describes the alterations proposed to the A180 eastbound diverge and A180 westbound merge layouts at Brocklesby Interchange since the submission of the DCO application, in order to mitigate the potential issues associated with the NGT Feeder 9 pipeline.

2 National Grid Transmission Feeder 9

2.1 Previous Engagement

2.1.1 Liaison is ongoing with the relevant service utility providers affected by the project. Enquiries were made in 2010 in accordance with the New Roads and Street Works Act, which recommended that the NGT Feeder 9 pipeline would require only protection due to the works associated with the A160/A180 project, but no diversion works would be necessary.

2.1.2 Following recommencement of the project in late 2012, the Highways Agency (HA) met with representatives from National Grid Gas in March 2013. The HA understood from this meeting that, as the pipeline has not changed since the previous engagement with National Grid, it would only require protection, and not diversion, where directly affected by the proposed widening of A180.

2.2 Pipeline Design Standards

2.2.1 Engagement with NGT following the submission of the DCO application highlighted that current pipeline design standards (IGEM/TD/11, published in 2008 and adopted by NGT in 2010) may now result in a requirement for the NGT Feeder 9 pipeline to be diverted.

1 IGEM/TD/1 Edition 5 (2008) - Steel Pipelines for High Pressure Gas Transmission – Institution of Gas Engineers & Managers


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Requirements for High Density Traffic Routes

2.2.2 This potential change is as a result of a clause (6.10.4 as extracted below) introduced into Edition 5. Therefore, in the situation where an existing traffic route is to be upgraded where it currently crosses a high pressure pipeline, then the pipeline should be modified to meet the requirements of Edition 5 as appropriate. An extract of clause 6.10.4 is included below:

6.10.4: Changes to traffic routes (roads and railways)

Where the addition of a new traffic route or construction work to upgrade an existing traffic route impacts upon the design of a pipeline, the pipeline shall be modified to meet the requirements of clauses 6.10.2 to 6.10.3.

2.2.3 The requirements of clauses 6.10.2 and 6.10.3 relate to whether the traffic route in question is defined by IGEM/TD/1 as either a High Density Traffic Route (covered by 6.10.2), or an Other Traffic Route (covered by 6.10.3). A High Density Traffic route is defined by IGEM/TD/1 Edition 5 as:

‘All roads that carry a volume of traffic totally, in both directions, 2000 vehicles per hour and above, for periods of at least 10 hours per week. The 10 hours may be spread evenly over the week or may be concentrated into set periods. On dual carriageway roads which carry less than this number, consideration needs to be given to future growth’

2.2.4 Calculations based on current and forecast future traffic flows have highlighted that the A180 is currently a High Density Traffic Route. The pipeline design criteria where crossing a High Density Traffic Route are as set out in the relevant sections of IGEM/TD/1 Edition 5, which are extracted below:

6.10.2: High density traffic routes (roads and railways)

A pipeline which either crosses, or encroaches within, the appropriate minimum proximity distance of a high density traffic route, shall:

• have a nominal wall thickness of not less than 11.9 mm

• have a design factor not exceeding 0.3, or 0.5 for pipelines of nominal wall thickness not less than 19.1 mm.

Any additional wall thickness shall be extended beyond the edge of the carriageway, or hard shoulder if present, or railway track. This extension shall ensure that no part of the unmodified pipeline is closer than the minimum proximity distance derived from Figures 5 or 6, as appropriate to the design conditions of the unmodified pipeline. The distance shall be measured from the edge of the carriageway or the outer edge of the hard shoulder, or the outer rail of railway track.

Minimum Proximity Distances

2.2.5 The concept of proximity distance (as referred to above in IGEM/TD/1 clause 6.10.2) is to ensure that the heavy wall pipe is extended beyond the boundary of a High Density Traffic Route such that, in the event of catastrophic failure, the impact on the population (in this case the traffic on the A180) would be minimised.

2.2.6 The minimum proximity distance is determined based on the specifics of the pipeline in question (pipe diameter, operating pressure, etc.). For the NGT Feeder 9 pipeline, NGT have confirmed that the minimum proximity distance at the crossing with the A180 is 92m. The existing proximity distances have


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been assessed as approximately 63m on the northern side of the A180. The proximity distance is approximately 99m on the southern side, assuming the measure is taken to the edge of carriageway at the back of merge nose. This is based on the current extents of heavy wall pipeline as provided by NGT.

2.2.7 The existing NGT pipeline, the limits of heavy wall section, and the associated minimum proximity distance are shown on drawing IMM-JAC-BRINT-SK-D-0000-0008 within Appendix A.

2.3 Recent Developments

2.3.1 The HA met with representatives from NGT in June 2014 to discuss the interactions between the A160/A180 project and the NGT Feeder 9 pipeline and agree a way forward. NGT confirmed that clauses 6.10.2 and 6.10.4 of IGEM/TD/1 Edition 5 would apply if works to upgrade the A180 (now confirmed as a High Density Traffic Route) were undertaken within the minimum proximity distance away from the current extents of heavy wall pipeline.

2.3.2 The design of the A180 eastbound diverge and A180 westbound merge as proposed within the DCO application are considered by NGT to represent an upgrade of a High Density Traffic Route within the minimum proximity distance of the A180. The view of NGT is that these proposed works would therefore necessitate a diversion, in accordance with the requirements of IGEM TD/1 Edition 5, to extend the length of heavy wall pipe beyond its current limits until such a point that the minimum proximity distance is achieved.

2.3.3 In response to this new information, design work has been undertaken to provide acceptable merge and diverge layouts in this location, whilst ensuring that no new road carriageway construction associated with the A160/A180 project would occur within the minimum proximity distance of the existing limit of heavy wall pipe on Feeder 9.

3 Design Development

3.1 A180 Eastbound Diverge

3.1.1 The A180 eastbound diverge as proposed within the DCO application is shown in blue on Plan A of drawing IMM-JAC-BRINT-SK-D-0000-0008 within Appendix A. This shows a two lane parallel diverge. Downstream of the diverge, the slip road would be two lanes, with a single lane joining the proposed roundabout and a single lane joining the A160 via a segregated left turn lane.

3.1.2 The proposed alternative layout is a taper diverge as shown in red on Plan B of drawing IMM-JAC-BRINT-SK-D-0000-0008 within Appendix A. The alternative diverge nose (demarked by hatched road markings to separate traffic on the A180 and slip road) is proposed to be located further east which would allow much of the existing diverge layout to be retained. This would ensure that no amendments to the existing A180 carriageway (relocation of kerb lines) would be made within the minimum proximity distance of the extent


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of heavy wall pipeline. All new road carriageway construction associated with the A160/A180 project would be outside the minimum proximity distance.

3.1.3 East of the diverge nose, the slip road would follow a similar alignment as that proposed within the DCO application design. The two lanes on the slip road would split to allow a single lane to join the proposed roundabout, and a single lane to join the A160 via a segregated left turn lane.

3.1.4 The modelled traffic flows (forecast to 2031, 15 years after the proposed road would open) have been checked against current standards included within the Design Manual for Roads and Bridges. This exercise shows that the proposed alternative option would operate to an acceptable standard over the design life of the project.

3.1.5 The alternative layout would reduce the footprint of the proposed diverge and therefore can be accommodated within the current DCO boundary.

3.2 A180 Westbound Merge

3.2.1 The A180 westbound merge as proposed within the DCO application is shown in blue on Plan A of drawing IMM-JAC-BRINT-SK-D-0000-0008 within Appendix A. This shows a single lane taper merge with two lanes on the slip road which would reduce to one lane before the merge nose).

3.2.2 The proposed alternative layout is a taper diverge as shown in red on Plan B of drawing IMM-JAC-BRINT-SK-D-0000-0008 within Appendix A. The proposed alternative layout is also a single lane taper merge but with an elongated and thinner merge nose. The alternative layout of the on-slip road requires the use of a tighter horizontal left hand curve on the approach to the merge nose than previously proposed in the DCO application design. This tighter curve remains compliant with design standards, and is required to tie the slip road into the alternative merge nose.

3.2.3 The proposed changes would ensure that no amendments to the existing A180 carriageway (relocation of kerb lines) would be made within the minimum proximity distance of the extent of heavy wall pipeline. All new road carriageway construction associated with the A160/A180 project would be outside the minimum proximity distance.

3.2.4 The alternative layout would reduce the footprint of the proposed diverge and therefore can be accommodated within the current DCO boundary. The temporary land that is currently proposed along the northern and southern sides of the A180, beyond the limits of the permanent works, would still be required in order to allow construction materials to be hauled from the proposed borrow pit areas to the east of Brocklesby Interchange.

4 Environmental Impact Assessment

4.1.1 Consideration has been given to whether any of the environmental impacts arising from the construction or operation of the project would change from those reported in the Environmental Statement (ES) and the second addendum to the ES, as a result of the proposed changes to the design of the slip roads to the west of Brocklesby Interchange.


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4.1.2 The assessment reported in the ES and the second addendum to the ES has considered the worst case scenario. This is because there is now the potential for a reduction in construction activities in this area as a result of the design change, but there is no potential for the activities in this area to increase. It is also important to note that the proposed design change would not remove any of the proposed environmental mitigation measures from the project.

4.1.3 The following table considers each environmental topic in turn:

Environmental Topic

Impact Assessment

Air Quality There would be no significant change to the residual impacts identified in the ES. The project would continue to cause no significant residual effects.

Heritage None of the residual effects identified in the ES would be caused by the construction or operation of these slip roads. Therefore, there would be no change to the significance of residual effects reported in the ES.

Landscape and Visual Amenity

The design changes are slight and there are no visual receptors close enough for their views to be affected by the design change. Therefore, there would be no change to the significance of residual effects reported in the ES.

Ecology and Nature Conservation

The ES concluded that there would be no significant residual effects. This remains the case with the proposed design change.

Materials The assessment reported in the ES identified minor adverse impacts relating to the depletion of natural resources. There would be a slight reduction the requirement for materials as a result of the design change, but the overall significance of the impact for the project as a whole would not be affected.

Soils and Geology

The ES concluded that there would be no significant residual effects. This remains the case with the proposed design change.

Noise and Vibration

The sensitive receptors identified in the assessment are at considerable distances from the location of this proposed design change. Therefore, there would be no change to the significance of residual effects reported in the second addendum to the ES.

All Travellers The ES identified that the improved road layout at Brocklesby Interchange would lead to reductions in drivers’ stress. Overall, with the project would reduce driver stress levels from high to low. The proposed design change would create a shorter off-slip road, but would be in line with design standards and so the change is not considered to be significant. Overall, low driver stress levels would be achieved.


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Community and Private Assets

The only impacts arising in this area of the project relate to agricultural land-take. The change in design would not affect the land-take requirements. Therefore, there would be no change to the significance of residual effects reported in the ES.

Road Drainage and the Water Environment

The proposed design change would reduce the area of impermeable carriageway to be drained. This would reduce the amount of runoff during a rainfall event, and would also reduce the dilution of carriageway runoff. However, as the runoff would be attenuated and settled in an attenuation pond, there would be no change to the neutral and slight beneficial impacts reported in the ES.

5 Conclusion

5.1.1 The existing NGT Feeder 9 pipeline crosses the A180 approximately 330m west of the existing overbridge at Brocklesby Interchange. The pipeline passes beneath the existing A180 eastbound diverge and westbound merge layouts, both of which would form part of the project.

5.1.2 The Highways Agency had previously understood that the existing pipeline would only require protection works, and not diversion.

5.1.3 NGT are of the opinion that current design standards now suggest that the pipeline would need to be diverted. This requirement is triggered as a result of the improvements to the A180 that were proposed in the DCO application design at the pipeline crossing where within the minimum proximity distance of 92m (as defined in IGEM/TD/1 Edition 5). This diversion would be required in order to extend the current length of heavy wall pipeline outwards until such a point where the minimum proximity distance is achieved to the A180, which is currently a High Density Traffic Route (as defined by IGEM/TD/1 Edition 5).

5.1.4 These proposed alternatives set out in this report would ensure that no amendments to the existing A180 carriageway (relocation of kerb lines) would be made within the minimum proximity distance of the extent of heavy wall pipeline. All new road carriageway construction associated with the A160/A180 project would be outside the minimum proximity distance. Therefore, as it is not proposed to upgrade the A180 carriageway (an existing High Density Traffic Route) within the minimum proximity distance, IGEM/TD/1 is not considered to be applicable in this case, and no diversion is required.

5.1.5 The proposed alternative A180 eastbound diverge layout would still remain operationally acceptable over the design life of the project.

5.1.6 The proposed design changes are considered to be minor on the scale of the project as a whole, and it is not considered to affect the significance of any of the residual impacts reported in the ES or the second addendum to the ES.

5.1.7 The alternative layouts can be accommodated within the current DCO boundary with temporary land still required to allow a haul route for construction materials.


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Appendix A A180 Eastbound Diverge and Westbound Merge Layouts

a180 eastbound diverge and westbound merge layout … igem/td/1 edition 5 (2008) - steel pipelines...

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