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A38 Dobwalls Bypass ECI

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Interserve was awarded the project for the design development of the A38 Dobwalls Bypass scheme, followed by detailed design and construction of the 4km dual carriageway bypassing Dobwalls village, with earthworks of 1 million cubic metres balanced in cut and fill, associated structures and drainage, lighting, signing and traffic management.

A38 Dobwalls Bypass, CornwallThe project was combined with the A30 Merrymeet ECI, and these were managed as a single package to maximise efficiency and economies of scale. The scheme was procured though the Early Contractor Involvement (ECI) procedure, which has resulted in time savings and improved value to the Highways Agency. Construction commenced in February 2007 and was completed two months ahead of schedule in April 2009.

Main project features

  • The mainline A38 comprised 3.2km of dual two lane all-propose carriageway
  • The new A390 Link Road, the Moorswater Collector Distributor Road and other amendments to the local roads total 5km of single carriageway
  • A roundabout at the junction of the A38 and A390
  • Composite over bridges at Havett Road and Looe Mills Junction
  • A pre-cast concrete arch structure to take the A390 over the London – Penzance railway thus avoiding the existing low bridge
  • The excavation and placement on site of 900,000 cu m of material
  • The diversion of the apparatus of six utility companies
  • Mitigation for bats, including the provision of two structures (bat bridges) that bats will follow to replace the hedges used by the bats to navigate between roosts and foraging areas
  • Further environmental mitigation features including bat boxes, mammal tunnels, otter fencing and ledges

The scheme has provided an important new connection to the busy A390 County road to St Austell and the south Cornwall coast and crosses the main Penzance to London rail line. The new road is expected to boost the South West’s tourism and business economy by improving journey time reliability for vehicles travelling across Cornwall.

The bypass has reduced 90 per cent of traffic from the village centre making a safer and quieter environment. It has improved road safety, which was worse than the national average, reduced significantly community severance, and improved the air quality and traffic noise impact of trunk road traffic.

Following the opening of the A38 Dobwalls Bypass, Interserve undertook an element of the detrunking works to the east and west of the village.

Achievements

Value management of the A38 Dobwalls Bypass has resulted in the original estimated price for these structures reducing by 40 per cent.

  • The new roundabout, a temporary road for the A390 and the A38 Dobwalls Bypass are now operational.
  • The relocation of 900,000 cu m of excavated material had to be transported across the existing A38 and A390 using plant crossings which were operated to minimise delays to the traffic on the A38. This was achieved by close working between the Highways Agency and Cornwall County Council.
  • Close liaison with Network Rail, designers, Cat 3 Checkers, contractors, suppliers and CDM Coordinator to identify the design, construction, operation and maintenance risks associated with the structure. Actions were put in place to mitigate those risks as well as review progress and programme, health, safety and environmental performance, possession management and safe systems of work.
  • Stakeholder involvement:
    • Site visits attended by local schools and the ICE, showing details of the scheme and its construction
    • Information on roadworks, incidents, events and alternative routes
    • Developed close relationships with all the landowners and other stakeholders, such as the Utilities companies
  • Paraslim equipment from our formwork and falsework specialist business, RMD Kwikform, was successfully used to construct temporary works frames. They used a combination of Steel Soldiers, Alsec aluminium backing members, Superslim Soldier Turnbuckles and telescopic Paraslim Tube. Dedicated Paraslim C-Hooks enabled modules weighing up to 1.5 tonnes to be readily crane handled during erection and dismantling.
  • Early Site Clearance was undertaken under the direction of the specialist bat, dormouse and reptile ecologists and meant that road construction works could commence earlier.

Teresa Frost, ICE D&C Joint Chair and ICE Truro City Club Chair, thanked us: “Please can you pass on my most grateful thanks to all of the people involved in the preparation and execution of the visit…It was a most excellent site visit and the certificate presentation was a lovely conclusion”.

When students from Liskeard School and Community College visited the site, Mr Forbes, Construction Teacher, commented that the students were talking enthusiastically about the visit and the many different occupations that they could follow in the future: "We would like to thank Interserve for its efforts in organising the visit and for the generous donation of site safety helmets and high visibility vests ...It is crucial for the success of the many different vocational courses that are offered here at the school that we are able to engage with employers to bring learning into a real work context, as well as providing students with opportunities to think about their future careers”.

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