Use of recycled and secondary aggregates in the construction of the Newport Southern Distributor Road

Morgan Vinci Ltd were appointed by Newport City Council to design, build, finance and operate the Newport Southern Distributor Road (SDR). The SDR is the biggest local authority Private Finance Initiative (PFI) scheme in Wales. The new 9.5 km road will run from Duffryn on the west side of Newport to the Coldra roundabout (M4 Junction 24) in the east. It includes a new bridge to span the River Usk and the upgrading of existing roads to dual carriageway.

The SDR scheme is designed to improve the environment in the city centre, taking traffic away from residential areas, improving access to industrial areas in the east and south of the city and providing a new river crossing. Construction started during the summer of 2002 and it is anticipated that motorists will be using the road by the autumn of 2004.

During the pre-commencement phase, the construction, design, environmental and procurement teams combined to maximise the use of project derived excavated materials. Opportunities were also sought to utilise locally available secondary aggregates: by-products of the heavy industry historically located in the area. As well as complying with a high technical specification, the materials used had to meet strict environmental guidelines. The environmental considerations were imposed as conditions of the planning permission from the Local Planning Authority to protect the local environment, in particular the ecologically sensitive River Usk: a Site of Special Scientific Interest and Candidate Special Area of Conservation.

The cost savings per tonne in using the locally available recycled and secondary aggregates, compared to the costs of primary aggregates as delivered, is shown in the table below. The average cost is based on the material that was used on site.

The direct savings in using the recycled and secondary aggregates, compared to the costs of primary aggregates, for the total project is shown in the table below.

Savings

Indirect savings were made through and the avoidance of waste disposal charges and Landfill Tax. Savings from the Landfill Tax, for the material generated on site, are given in the table below.

The table below shows the total savings of using recycled and secondary aggregates for the Newport SDR.

Costs

No significant additional costs of using the recycled and secondary materials on site have been identified.

Indirect benefits

In addition to the significant benefits for the construction project in using locally available recycled and secondary aggregates, a number of other benefits are also accrued:

• Reduced demand for conventional aggregates, reducing the environmental impact for the community;

• Fewer long distance haulage movements reducing the environmental impact in the local community;

• Demonstrable proof that, through the use of risk assessments, recycled and secondary aggregates are environmentally acceptable and can be used in the vicinity of environmentally sensitive areas without adverse impacts;

• Encouraging innovation within Morgan Vinci;

• Promoting environmental beneficial practices, namely sustainable waste management, within the construction industry.

Overall, 95% of all aggregates used in the Newport SDR are recycled and secondary materials. This success can be attributed to the geographical location of the principal stockpiles of recycled and secondary aggregates, the ingenuity of the site team, together with a favourable specification. However, not surprisingly, the costs associated with transportation, particularly of the dense steel slags, would probably make their use uneconomic other than within South Wales. It should be noted that primary aggregates have been used on the project. Natural stone was required for the Armourstone to meet Environment Agency requirements and specifications restricted the use of recycled and secondary aggregates for use as the pipe bedding material and the drainage blanket.

The engineering fill material was tested against physical and environmental specifications to ensure suitability. Recycled asphalt was recycled on site for the capping layer. For the sub-base, blastfurnace slag and spent railway ballast was stabilised with cement to exceed the specification.

All materials were tested to ensure they complied with the Specification for Highways Work (May 2001) and chemical thresholds agreed with the Environment Agency.