Award-winning A34 bypass reduces congestion in Alderley Edge

The A34 Alderley Edge and Nether Alderley Bypass was a challenging public sector project, designed to divert traffic away from the picturesque village of Alderley Edge and significantly reduce congestion. Intended as a rural bypass, the project’s design aimed to complement the surrounding environment and integrate the needs of the local area, showcasing the best in engineering innovation.

Meeting the needs of the rural community through design

Located in the Cheshire countryside, it was essential that the bypass design complemented the surrounding pastoral environment. Key design features of the rural bypass included:

• Construction of the road within several cuttings to avoid intrusive embankments, particularly where the bypass crosses the main London-to-Manchester railway line

• Choosing low-noise surfacing material to minimise invasive noise pollution

• Construction of landscape mounds to shield the local community from additional noise and air pollution

• Extensive landscaping and habitat creation, including grasslands, wildflower meadows and conifer plantations

The works comprised the construction of a new 5km single carraigeway bypass, with:

• 1km of bentonite slurry wall up to 20m deep

• Three road bridges, two with cast in-situ decks and one with pre-cast concrete beams

• A footbridge with pre-fabricated steel deck

• Modifications to an existing roundabout

• New roundabout off-line to tie in with the existing A34

• Bored pile retaining wall

• Upgrades to side roads and existing junctions

• Nine pre-cast culverts

• 20,000m of drainage

Improved safety and reduced inefficiencies

Early on in the design stage, the team identified that pre-casting many of the project’s structures would offer an enhanced end product, improve safety, reduce inefficiencies and provide greater cost programme certainty.

Consequently, over 70 culverts and headwalls were pre-cast on the project. In addition, pre-stressed beams and fabricated steel footbridge deck were also manufactured off-site. To ensure the highest quality of workmanship and finish, the team regularly visited the manufacturing facilities.

Following visits to the footbridge manufacturer, the design was amended to allow painting work to be completed more efficiently. These changes will also help with future maintenance of the footbridge.

Improved resource efficiency

To improve resource efficiency and minimise off-site disposal, the team developed strategies to reuse excavated peat and deal with the large volumes of wet material generated on the project.

The team implemented the following measures to manage the additional wet material:

• Around 28,000m3 of peat was excavated during the driest period of weather. The majority was combined with a mixture of class 2 and 4 material and buried in the landscape area to avoid removal off-site. Around 8,000m3 was laid out to dry, then mixed with topsoil and spread over areas of the site requiring most planting. This further enhanced the nutrient value of the soil

• Dried areas using lime stabilisation

• Dried wet unsuitable material out insitu by forming sumps and ditches adjacent to the material to allow the water to run out and reduce the moisture content

• Mixed wet cohesive material with drier, class 2 and 4 material to create an enhanced quality material for use in landscape areas

Diverting traffic away from the village

By diverting traffic away from the centre of Alderley Edge, the new bypass has restored the character of the village. The works have:

• Removed an estimated 26,000 vehicles a day from Alderley Edge and improve the attractiveness of the village centre

• Improved road safety and reduced casualties

• Relieved traffic congestion on the A34

• Improved facilities for cyclists, with 11,000m of new cycle lanes constructed as part of the works

• Reduced congestion, air pollution, noise and nuisance caused by through traffic on the A34

• Enhanced the quality of life of those who live in, work or visit the area

• Contributed to an efficient economy and to support sustainable economic growth and regeneration

• Improved the efficiency, quality and longevity of the local transport network

Award-winning design and construction

Through extensive public consultation, commitment to environmental issues and partnership working, Cheshire East Council and Birse Civils have delivered a project which demonstrates industry-leading performance in all aspects of its design and construction. This is highlighted by the project’s key headline achievements:

• ~£3m of project savings, through value engineering and innovation

• Delivery ahead of programme

• Gold Award from the Considerate Constructors Scheme (CCS)

• 90% average customer satisfaction score

• 126,000 tonnes of recycled content materials sourced for use on site

• Zero off-site disposal, with over 475,000 tonnes of material diverted from landfill

• 350,000 man-hours worked with no RIDDOR accidents.

Reusing surplus material to avoid off-site disposal

Constructing the road within three cuttings resulted in over 150,000m³ of surplus material, requiring disposal off-site to landfill. Instead, the team designed landscape mounds to absorb this excess material.

Reusing this material on site avoided 17,000 wagon movements on local roads. This substantially reduced the project’s carbon footprint, disruption to the local community and resulted in a £1.8m cost saving.

Reduced carbon emissions

In addition to the 150,000m³ of surplus material reused in landscape mounds, the team developed further strategies to achieve their ambitious target of zero off-site disposal for the whole project. Over 475,000 tonnes of material has been diverted from landfill in total, resulting in a saving of over 800 tonnes of carbon emissions.

This included reusing:

• All topsoil on site, totalling 130,000 tonnes

• 2,000 tonnes of road planings

• 7,500 tonnes of material from an adjacent contractor

• All site clearance material from an area of over 26 hectares

Industry-leading use of recycled materials to improve sustainability

The project team engaged with Envirolink Northwest to procure 126,000 tonnes of recycled materials for use on site. This represents the single highest tonnage of recycled materials used on any scheme that Envirolink have monitored or been involved in.

Recycled materials used on the project include:

• 120,000 tonnes of recycled capping

• 12,000m of concrete and plastic pipes

• 100% recycled plastic Envirokerbs

Encouraging local employment to further reduce emissions

83% of the construction works were carried out by local subcontractors based within a 40-mile radius of the site. This greatly reduced the scheme’s carbon footprint, while also helping to sustain the local economy.

Using the specialist expertise of ecological consultants, Biota, the design has incorporated extensive habitat creation. Throughout construction, the team implemented measures to protect local wildlife and enhance existing habitats. Landscape areas have been designed to replicate natural features and ensure that habitat creation exceeds what was removed to accommodate the works.

This has included:

• Planting 50,000 new trees and bushes, far exceeding the numbers lost to the scheme

• Constructing a new badger sett and re-locating an existing sett

• Creating five new freshwater ponds for nature conservation and to protect endangered great-crested newts

• Planting new grassland areas and wildflower meadows

• Installing precast mammal ledges within culverts

• Erecting 10,000m of newt fencing

• Installing new bird boxes

• Introducing flood attenuation and ecological enhancement plans

During the ECI phase, the team designed landscape mounds to be built alongside the new bypass. As well as allowing the reuse of surplus material, these natural features also act as noise and pollution bunds for the local community. Following consultation with residents, the team revised the design to amend vertical and horizontal levels to provide further screening.