This case study explains the management strategy that Breheny Civil Engineering employed to deliver an environmentally sustainable 2.4km road scheme that was delivered 6 months ahead of schedule.
Bedford Western Bypass is a long awaited improvement link to the west of Bedford Town Centre. The new bypass links the A6 Paula Radcliffe Way with the A4280 Bromham Road and enables vehicles to avoid the Town Centre when travelling in the north west of the town.
Breheny Civil Engineering were appointed in 2014 to construct the 2.4 kilometre single lane road, build 3 new roundabouts, a new bridge over the Midland Mainline Railway and realign part of the A6 Paula Radcliffe Way Roundabout.
- Location: Bedford
- Cost: £18.6m
- Year of completion: April 2016
- Duration: 18 months
- Client: Bedford Borough Council
- Main Contractor: Breheny Civil Engineering
A sustainable earthworks solution
Breheny Civil Engineering set a project goal for the Bedford Western Bypass that no bulk materials be taken from site. The design of the bypass included 128,000m^3 of bulk earthworks cut and fill which included 22,000m^3 of archaeologically excavated material that had been identified as unsuitable for engineered fill (Class 4). A phased strategy was developed by the team that allowed the earthworks to advance on two fronts, working towards the railway that divided the site. This had the potential to offer massive programme savings as productivity could be doubled.
Fill was transported to the eastern embankment via road vehicles whilst the western embankment was constructed simultaneously using articulated dump trucks. Each team were given production targets which were monitored and reviewed daily. This kept the operation efficient and minimised the duration of the export operation and impact on the local road system. A wheel wash was deployed at each site entrance and supplemented with road sweepers to keep mud off the roads.
The largest of the attenuation ponds was yielding class 1A material so a methodology was developed to borrow additional material within the lateral footprint of the pond and replace with the archaeological arisings. Without this exercise the unsuitable materials would have been required to be taken to tip and new material imported.
Benefits of our approach:
The calculation of the reduced impacts of this decision reduced the following:
- 4,400 vehicle (lorry) movements
- 50 tonnes CO2 (0.35kg/km)
- 22,000m^3 of natural resources
- Earthworks programme reduced by 3 months
- Overall programme reduced by 6 months as 2 no. work fronts were maintained.
In addition, approximately 2,000m^3 of hard breakout material was processed on site into 6F2 capping and utilised in the works, this came from the removal of existing hard landscaped areas.
Fig 3 - A view from eastern embankment looking east towards Paula Radcliffe Way in July 2015. The first stage of embankment filling has been completed and the bridge abutment has just started. Stockpiles of hard breakout ready for processing can be seen on southern boundary of the site.
This proactive solution to dealing with the earthworks on the project offered a sustainable solution which dramatically reduced the need for lorry movements from the site, this not only directly reduced CO2 emissions from the site traffic it also reduced the number of lorries on the surrounding roads, reducing CO2 and potential congestion to local traffic.
Protecting, preserving and improving local biodiversity
The Great Ouse river corridor is not only a stunning part of the Bedfordshire landscape but is also home to a wide variety of native flora and fauna. The scheme was developed to not only protect existing wildlife in the area but to also create new habitats for amphibians, birds, badgers and otters. As part of drainage improvements to areas of sedge adjacent to the Great Ouse, new ditches and widening of existing ditches were to be installed. Timber weirs were constructed to create areas of wetland.
The original scheme involved creating access tracks to complete the works in the County Wildlife site using crushed concrete as the foundation and running surface. Breheny looked at this situation as planning restrictions forbade rubber tired vehicles in the area as they would destroy the sensitive topsoil.
It was calculated that this method of excavating the topsoil and importing crushed concrete would have involved:
- Excavating 5,000m^2 of sedge, 800m^3 of wetland soils.
- Importation and deposition of 800m^3 of crushed concrete in the Wildlife area to form access tracks
- At the completion of the works the excavation and disposal of 800m^3 of the crushed concrete used as access tracks to be taken to tip
Instead the Breheny team investigated and chose to use aluminium track mats which allowed the work to be carried out without any destructive temporary measures (none of the above was required). The sedge under the track mats recovered within a matter of weeks and thus didn’t require any replanting or disturbance. There was some sedge material excavated in the re-profiling of ditches, this was re-used in the attenuation ponds and is now thriving in a new area.
As part of the scope of work we built a new badger sett and otter holt. With previous badger activity in the area a badger tunnel with badger fencing alongside the bypass were constructed to encourage badgers into the wildlife site.
A programme of surveys and monitoring was undertaken during the scheme. Bird, bat, newt, otter, badger and vole surveys before entering new areas of the site to ensure that none were disturbed during construction works.
As part of the scope of work we built a new badger sett and otter holt. Under the bypass we built a Badger tunnel with badger fencing alongside the bypass.
We undertook weekly noise monitoring and carried out vibration monitoring during the works to ensure 75dB ambient noise levels were adhered to during working hours.
Benefits of our approach included:
- Impact on existing habitats was dramatically reduced by using track mats
- Track mats were cheaper, cleaner and easier to manage than a traditional haul road
- Cleared wetland vegetation was re-planted
- Additional new habitats for animals created
- Preventative measures employed to minimise wildlife incursions onto road
- Monitoring and timing works to reduce impact on wildlife
With careful planning and consideration for the existing biodiversity of the site, the Breheny team were able to deliver a scheme that was both environmentally sustainable and beneficial to the local area.
Bedford Bypass Project videos:
- Progress Summer 2015
- Bridge construction including the beam lift over the Midland main line Railway May-Oct 2015
- Completion April 2016
Simon Andrews, Project Manager, J Breheny Civil Engineering (scheme enquiries)
e: [email protected]
m: +44 (0) 7967 835 090
Steve Dighton, Business Development, J Breheny Civil Engineering (other enquiries)
e: [email protected]
m: +44 (0) 7967 487 228