M4 Corridor around Newport

RPS was appointed as lead environmental consultant to support the Costain Vinci Joint Venture who were contracted to progress the M4 Corridor around Newport. The project is the largest highway scheme to be commissioned by the Welsh Government since devolution in 1998 and involves the proposed construction of a new 23 km section of three-lane motorway to the South of Newport, between Magor and Castleton.


The proposed new section of motorway will cross the northern part of the Gwent levels Sites of Special Scientific Interest (SSSI), pass over the Newport Docks and the southern boundaries of the Docks Way landfill sites and the former Llanwern Steelworks site. In addition, an elevated section would cross the River Usk with a new 440m span cable-stayed bridge.

RPS managed the preparation of the Environmental Statement providing specialist environmental teams including eight expert topic witnesses for the Public Local Inquiry.

Key details

Project name
M4 Corridor around Newport

Costain Vinci Joint Venture

Newport, South Wales, UK

Services provided

  • Environmental coordination
  • EIA management
  • Environmental surveys
  • Ground investigation
  • Expert witness at public inquiry
  • Environmental permitting
  • Archaeology
  • Ecology
  • Noise
  • Contaminated land
  • Cultural heritage
  • Waste management
  • GIS
  • Agriculture, land use and community assets
  • Health Impact Assessment


The first stage of the project had to be delivered within extremely demanding project programme of 12 months. The timescale was particularly challenging due to the sheer scale of the estimated £1bn project construction cost which required preliminary design proposals to be prepared, environmental surveys undertaken across over 12,000 hectares and an environmental impact assessment, ultimately leading to the issue of draft land orders and an Environmental Statement, all within less than 12 months.

Over 50% of the proposed motorway route crosses brownfield land, some of which has potential and known land contamination legacies, including several landfills, steelworks land and chemical works.

In addition, the proposed scheme crosses four sensitive Sites of Special Scientific Interest (SSSI’s) comprising the Gwent Levels. The primary feature of which is the intricate network of surface water ‘reens’ and field ditches with their associated freshwater ecology. A variety of protected species and habitats were identified including otters, badgers, reptiles, birds, great crested newts, bats and dormouse.

M4 Corridor Around Newport - project image (shutterstock_308968301).jpg


Throughout the project, we have worked closely with the design and contractor team, often with our staff embedded with the integrated contractor and designer delivery teams. This has enabled us to quickly overcome problems and develop solutions to mitigate risks and potential delays. RPS delivered the Environmental Statement in 11 months in line with the Welsh Governments programme

We designed the land contamination management strategy which included a comprehensive review of over 40 potentially contaminated sites. To minimise materials being disposed of off-site to landfill we also designed, managed and supervised a detailed ground investigation to support the geotechnical design and the land contamination remedial strategy. Ultimately our remediation and strategy objective, which was agreed in principle with the local authorities and NRW, was to re-use 100% of all contaminated soils within the scheme.

The details of the project and engineering design changed regularly in response to consultee comments and the requirements of the project. Our staff were embedded within the design and engineering team to provide input into decisions and modifications as well as advising on the knock-on implications affecting the wider team.

As lead environmental consultant, our involvement has included ecological surveys and environmental monitoring of this highly sensitive setting for over three years. We have also been undertaking surface water and groundwater monitoring to provide an extensive baseline dataset to be used to design an appropriate surface water management protection plan.

Project Statistics

highway scheme to be commissioned by the Welsh Government since devolution in 1998
estimated project construction cost
new section of three-lane motorway
Over 40
potentially contaminated sites reviewed
Over 590,000m3
contaminated materials to be remediated for reuse in the scheme
Over 10,000
hours of environmental surveys undertaken by RPS
Over £5m
of ground investigations carried out by RPS

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