A470 Cwmbach to Newbridge-on-Wye

Excellent

 

83.3%

Whole Project

Project Team
Client: Welsh Government
Design: Jacobs Engineering UK Ltd
Construction: Alun Griffiths Contractors Ltd

The Project

The A470 Trunk Road runs from Cardiff to Glan Conwy, connecting North and South Wales and serving local communities. The existing A470 between Builth Wells and Newbridge-on-Wye ran generally parallel to the River Wye on a meandering and, in places sharply undulating vertical alignment. It included single lane traffic signal control operation at the Pont-ar Ithon Bridge and a headroom restriction of 13ft 6in where it passes beneath the Heart of Wales Railway line at Cwm-bach.

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The aims of the project were to improve safety, reduce journey times, enable two way traffic flow and provide a road suitable for use by all classes of vehicle.

The project was an ECI Contract comprising construction of 5.7km of new 7.3m wide, single carriageway with 3.5m wide verges either side (including 1m hard strips, between Cwm-bach and Newbridge-on-Wye). The Welsh Government was the client with Atkins acting as their agents. Alun Griffiths Contractors Ltd was appointed as Principal Contractor with Jacobs Engineering UK Ltd acting as their Designer. Under this form of contract the ECI Team is responsible for the detailed design, publishing the draft orders, undertaking a Public Local Inquiry and construction.

The scheme included two major structures, a bridge over the Dulas Brook and the Heart of Wales Railway and a bridge over the River Ithon Valley. Both of these watercourses are tributaries of the River Wye SSSI SAC. A further portal arch bridge was constructed across the existing A470 to allow this to remain open for local traffic and use as a cycle/bridal way.
Major earthworks comprised some 400,000m3 cut to fill.

Drainage from the new road was controlled by a series of attenuation ponds and an attenuation tank, to control the rate of flow into the local watercourse network. Large diameter culverts with mammal ledges were constructed on watercourses crossing the route.
The new road is not lit; however, LED footway lighting has been included at the southern end of the route.

Challenges faced:

Project Management – The use of the Early Contractor Involvement form of contract, ensured that the project received input from all parties (i.e. Client, Clients Agent, Designer and Contractor) during the detailed design and planning phases of the project (Key Stages 3 and 4).

Land Use & Landscape Issues – Landscape issues played a key role during the life-cycle of the scheme and formed one of the key challenges, not just in terms of integrating the scheme into the landscape, but also maximising the experience of driving through this high quality rural landscape.

Slackening of cutting slopes, retention and management of existing vegetation, establishment of viewpoints and early mitigation planting were all techniques adopted in the development of the scheme. During the construction phase, the project team made a huge effort to fine tune the design to ensure that where possible, every existing feature of value was incorporated into the scheme.

Ecology and Biodiversity – The most sensitive ecological issue encountered during the scheme was the need to cross the River Wye and Tributaries SAC, twice, namely the Dulas Brook and River Ithon. Several protected species were confirmed as being present, including:

  • Badgers
  • Bats (pictured below)
  • Invertebrates
  • Lichen communities (including the rare lecanora sublivescens)
  • Otters
  • White clawed crayfish.

 

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Throughout the construction phase an Environmental Clerk of Works was present on site to ensure best practice was used and to oversee the implementation of environmental mitigation. Ecological mitigation included extensive ecological surveys and mitigation for protected species, the provision of 87 bat boxes, 19 hibernacula and invertebrate log piles, 6 swift and dipper boxes, 10 mammal / bat crossings. The long-term effectiveness of these mitigation measures will be monitored during the 5 year aftercare period, but early results are exceptionally promising with high usage levels on the majority of mitigation features.

The Historic Environment – Prior to construction, a series of archaeological evaluations were undertaken including the excavation of land around the Cwrt Llechryd Scheduled Ancient Monument (SAM). These evaluations did not record any significant finds. An Archaeologist was present during site clearance and topsoil strip activities to monitor for the presence of potential features of interest.

Water Resources and the Water Environment – The new road drainage accords with all current standards and incorporates measures that protect the surrounding watercourses, including the Special Area of Conservation, from contamination and pollution in the event of an incident involving potentially harmful spillages.

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Sustainable Urban Drainage Systems (SUDS) principals have been incorporated into the works. These included 7 attenuation ponds, which hold water and control the outflow comparable with the pre-scheme situation. In accordance with Environment Agency guidelines, the ponds were installed prior to any construction work in each area, in order to control the rate and quality of discharge from the site during construction. Extensive pollution control systems were installed including a Silt Mitigation Plan, use of silt fences, bales, geotextile filters, flocculent dosing systems and Lamella Clarifiers.

Energy and Carbon – A Carbon Footprint calculation was undertaken during design to identify the principal carbon emitting activities and materials. This was then used to feed back into the design process to eliminate as many of these activities as possible. Other initiatives employed were:

  • advanced driver training to ensure efficient use of fuel, vehicle trackers to monitor plant efficiency and identify improvement opportunities fitted to all plants;
  • earthworks balance and sequencing to minimise double handling, minimising road haulage, import and export, adverse environmental impacts.

Material Use – because of the location both geographically and from a landscape perspective, material use was important for the project. It was imperative that materials should be aesthetically pleasing, durable, able to withstand the harsh climate and local to the site to enable easy transport on a rural road network. To achieve all of these criteria, the following materials and methods were utilised on the project:

  • Weathering steel was used in bridge construction, commended by the Design Commission for Wales, improving visual impact and reducing maintenance.
  • Precasting of concrete products wherever practicable to optimise site deliveries and reduce environmental risk.
  • Use of innovative surfacing materials to optimise carriageway construction depths. Bituminous layers of the carriageway utilised 35mm of thin surface course; 65mm of HMB35 binder course and 130mm of HMB35 base course, which brought considerable savings in cost, time and carbon usage.
  • Extensive earthworks remodelling to minimise the need for import of primary quarried aggregate or disposal of surplus material.
    A steel concrete composite bridge was redesigned and replaced by a pre-cast concrete portal arch structure, which reduce the volumes of steel and concrete used and decreases the construction time.
  • Use of recycled plastic drainage products, precast concrete products optimising site delivery and reducing environmental risk, reuse on site of all felled timber.

Waste Management – A detailed Site Waste Management Plan was prepared for the project which utilised the WRAP SWMP to predict waste volumes, plan re-use/disposal strategies and monitor actual waste arisings. Waste segregation and recycling areas were established in site compounds, offices and canteens. Training was given on efficient use of materials, waste segregation and recycling. No timber felled during site clearance, entered the waste stream. Timber with commercial value was processed by an adjacent sawmill, brash was baled and used as biomass for bio-energy. Some of the arisings were retained on site and used for the construction of habitat piles and hibernacula.

Transport – Due to the rural nature of the scheme transport of personnel and materials was a major consideration. The Heart of Wales Railway, runs through the site and the possibility of using this for project transport was investigated. It was not possible to transport materials as there was no rail head and it was not practicable to form one. Transport of personnel was also difficult by rail due to a limited timetable and difficult connections. A Sustainable Transport Plan was prepared. Orders for materials were placed with local suppliers, loads were rationalised to combine deliveries, the site compound was located in the centre of the scheme with localised compounds and laydown areas at major structures. Parking was restricted with a minibus service to transport personnel from the central compound. On site accommodation was provided to personnel to reduce the requirement for commuting.
A Traffic Liaison Group was formed to optimise traffic management for the scheme. The construction process was phased to minimise impacts on the existing highways network. A steel / concrete composite bridge was substituted for a pre-cast concrete portal arch to reduce the transport of materials, construction time and the need for road closures.

Effects on Neighbours – Extensive noise surveys were undertaken during the development of the scheme. These surveys established existing noise levels and formed the basis for calculations of projected noise levels following the construction of the scheme. In locations where post construction noise levels increased beyond acceptable levels, mitigation measures were designed to reduce them to acceptable levels. Mitigation measutres include close boarded fencing and earth bunds.

Relations with the Local Community and other Stakeholders – Stakeholders relations and Customer Care were priorities with the project and the following initiatives were employed to mitigate these:

  • Use of innovative Public Information Exhibition on a Welsh trunk road scheme, to establish stakeholder input early in the scheme development. This approach is now common practice on all Welsh Government highway projects.
  • Retention of the existing A470 to service the local community – conversion to ‘Quiet Lanes’ facility, a dedicated offline provision for non-motorised users.
  • Use of gateway features and public art within the project.
  • Education: working with Careers Wales and Powys to deliver key curriculum elements around Science and Maths in the workplace; supporting Young Enterprise Programme, over 500 school pupils attended events highlighting H&S on construction sites, use of the ICE Building Bridges to Construction scheme.
  • Community support: During extreme weather of December 2010, we used our site 4x4’s to maintain vital links for Community Nurses and local social services departments and deliver hot meals to elderly residents cut off by snow.
  • Sponsorship: large number of sports, local interests and community groups supported and £15,000 raised.
  • Legacy sculpture and village gateway features designed by local school children.

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To what extent did the use of CEEQUAL influence your project?

Environment and Sustainability were very much headline issues for the scheme due to the sensitivity of the scheme corridor. The use of CEEQUAL further emphasised and structured the project approach to sustainability. Alun Griffiths Contractors have aligned their Environmental Management System with the 12 sections of the CEEQUAL Version 4.1 Assessment.