Sustainable civil engineering construction – is 95% recycled material achievable?

Most developments in the UK consider the carbon impact of the building construction and ongoing operational energy impact. Yet few address the whole carbon and environmental impact of development of developments, to include the civil engineering elements. Perhaps this is an arrogance that “the building” is seen as so more important that the infrastructure that supports it. Or perhaps it is because the UK consultants can often lack the expertise in civil engineering design sustainability and fail to communicate the benefits.

One thing that is clear, is that Buildings need infrastructure. A building without car parking, or access to public transport, or one that floods, or doesn’t have access to water, or sewerage – is essentially worthless, no matter how fancy it looks.

So if civil engineering infrastructure is criticall to a complete development, why is the sustainability rarely properly considered. One could argue that part of the problem is BREEAM and such schemes barely touch on the civil / environmental issues.

Following considerable progress in energy conservation, many argue the next big, potentially easy gain is in civil infrastructure design.Sustainable recycling

Sustainable civil engineering design and construction at Mt Vernon Hospital. Design by Wilsham Consulting Director – Stephen Gibson

So what is sustainable civil engineering design and construction?

There are many elements to sustainable civil engineering design, including the carbon, use of virgin aggregates, water quality and quantity. They often include the following:

  • External highway surfacing design
  • Highway subbase design
  • Clean water design
  • Sewerage option sustainability appraisal
  • Sustainable drainage design
  • Water masterplanning
  • Flood mitigation

 An example of sustainable civil engineering design. Is 95% recycling possible?

It is time for a practical example, to show what is possible and what the benefits are for a client.

Mount Vernon Hospital Boulevard and treatment centre, for the Hillingdon NHS Hospital.

This was a £13 million new major treatment facility with an associated new public transport facility, with staff and visitor parking. Spending on civil infrastructure by hospitals is often limited, yet it is also critical to providing access to the facility to those working and visiting hospitals. Hillingdon NHS Trust looked to create a new welcoming main hospital entrance boulevard, bus compound and car park as cost effectively and as sustainably as possible.

civil engineering sustainability

Mt Vernon Hospital public transport interchange during construction.

The site contained a legacy of World War 2 preformed concrete ward buildings. To minimise costs and environmental impact, approximately 95% of the existing buildings and foundations were recycled on site, with only hazardous or surplus materials removed from site.

I produced a bespoke material performance criteria and design which was both achievable using a conventional mobile crushing and screening system and would provide the appropriate standard of hydraulic and structural performance. There is no UK approved design standards for such design.

says Stephen Gibson, Wilsham Consulting Director.

Research was done into risks and performance, with advise from CIRIA and ongoing visual assessment of performance.

What recycling of material was achieved?

–    100% of the capping material used was site won.

–    100% of the “Type 3” sub-base for the car park was site won

–    60% of the aggregate in the slab paving composed recycled material.

–    100% of the plastic in the drainage kerbs was from recycled sources.

–    100% of the silts from the screened sub-base used in site landscaping.

As such 95% of the total material used was from recycled sources.

What were the project outcomes for the NHS hospital?

This leading example of innovative civil engineering design achieved the following:

  • Client savings of around £200,000 against original budget.
  • 80% reduction in the carbon effect of the development, when compared to traditional construction.
  • Reduce peak surface water discharge and flood mitigation for the local community.
  • Reduced total surface water flows discharged.
  • Improved water quality discharge.
  • Increased use of public transport and approved parking areas.