Involving the upgrade of the motorway network through widening of existing three lane carriageway to four lanes over a length of 25km, this Highways Agency Early Contractor Involvement (ECI) contract was the first where the target cost came in below scheme budget. It is also notable for being the first UK motorway widening scheme to be constructed using a moveable steel barrier traffic management system instead of a contra flow.
Scope of the widening scheme
The scope of the M1 widening scheme covered a 25km section of motorway, bringing it up to dual four-lane standard. The scope of works included the replacement of overbridges, the widening of underbridges, extensive lengths of cutting and embankment retaining walls, 47 new overhead sign & signal gantries were provided at up to 57 metre span, new lighting and communications, and landscape works. 120,000 trees were also planted including 30,000 hardwood trees grown from locally sourced seeds in order to reduce the carbon footprint for this part of the works. Our road engineers worked on the main contract with co-designers WSP. The environmental team liaised closely with WSP to assess all available information, design and coordinate any necessary additional works and incorporate protection and mitigation measures into the overall scheme.
The contract was the first where the target cost came in below scheme budget. This saving was due to the following design innovations:
- Provision of a reduced cross section design -0.75 metres narrower than a standard four lane section
- Revised widening solutions at underbridges, allowing the retention of existing wingwalls with reduced material quantities and reduced disruption to residents
- Analytical design of pavements to retain as much existing construction as possible.
This project is the first UK motorway widening scheme to be constructed without contra flow. Instead it used a moveable steel barrier traffic management system. The benefit in using this system was that three traffic lanes were operational between 6am and 8pm, while a reduced lane capacity overnight increased the available working area.
All works were designed to fit within the existing highway boundary, producing a particular challenge for the drainage design. Without the space available for attenuation ponds, additional storage capacity was gained by using up to 1,200mm dia pipes within the verge.
Environmental assessment, protection and mitigation
Our environmental consultants coordinated with all the various disciplines to ensure that the necessary levels of environmental assessment, protection and mitigation were incorporated into the project. Specifically, they focused on:
- Ecology - extensive species-specific surveys were carried out over several seasons to evaluate the local ecology
- Mitigation measures were undertaken to limit the impact of the works, such as the provision of bat and bird boxes and vegetation clearance for reptiles.
- Surface water quality testing was done along the length of the site and we also carried out a detailed review of the need to provide otter ledges.
- Expected waste arisings were audited and a site waste management plan produced, offering strategies to quantify, analyse and monitor arisings with the aim of limiting waste. In particular:
- DMRB assessments were carried out and strategies devised to deal with spillage containment and pollution control.
- Environmental risks were evaluated for potential contamination from soil or gases, and soil waste classification assessment was also carried out to support disposal planning.
Production of NEWT (Not Environmentally Worse Than) assessments was critical to the project to ensure that deviations from the scheme as outlined in the Environmental Statement did not degrade the environment and jeopardise project approval and completion. Along the way, extensive negotiation and consultation with sub-consultants, the Highways Agency, Natural England and the Environment Agency were undertaken.
Summary of Ramboll responsibilities
- Concept design development during Phase 1B in order to achieve scheme budget
- Highways Design Check of alignment, drainage, safety fencing, lighting, signs, lines and pavement
- Geotechnical design of 50 kilometres of soil retention systems including soil nailing, select earthwork zonation, piled retaining walls and anchored retaining walls
- Design of 3 kilometres of new piled and anchored retaining wall
- Design of 47 new gantries, utilising standard Ramboll Gantry System designs
- Design of modifications to over 44 other existing structures including demolition and replacement of one overbridge and widening to two railway underbridges
- Site design support and examination of the works
- Undertaking or managing all Environmental/Ecological and landscaping works.
ICE Yorkshire and Humber Regional Awards 2011 – Smeaton Trophy, Certificate of Excellence
Collaboration with WSP
Ramboll and WSP have collaborated and worked with Contractors on major highway design for over 40 years and have been at the forefront of motorway widening since the first design and build contract on the M25 between junctions 8 and 10 in 1997. Collaboration has continued with ECI contacts for widening the M1 between junctions 6a and 10 and between junctions 25 and 28 and the M25 between junctions 12 and 15. The M25 DBFO Section 4 was the most recent for this relationship bringing the total length of widened motorway to over 100 km.