WATCHING THE WASTELINE

Real lives
Can you really design out waste? Looking for a fundamental change of approach, Aedas tried it on two magistrates’ courts and its verdict is encouraging. Yasser el Gabry reports

In conjunction with Her Majesty’s Courts Service (HMCS), Aedas has been working with Wrap (Waste & Resources Action Programme) for over a year to begin making Designing out Waste a fundamental part of how we do business. The best example of where we have reduced waste through design is on the £26m development of two new magistrates’ courts in Chelmsford and Colchester for HMCS. Both are of reinforced concrete frame and floor slab construction. Colchester has three floors with a first floor mezzanine and Chelmsford is two floors with first floor and second floor mezzanines.  The courthouses are designed to the HMCS Design Guide 2007, and set to achieve BREEAM excellent and other specific targets from the government’s Framework for Sustainable Development.

The process
At an initial project team workshop, we used the five principles set out in Wrap’s Designing out Waste: A Design Team Guide for Buildings to identify opportunities to reduce waste.

The design opportunities identified had to meet a series of criteria. These included reducing the extent of construction site waste without increasing the project cost, having a significant negative effect on the design or construction programme, or compromising the original design intent. They also had to have the collective buy-in of the design team.

We could then investigate alternative methods of construction, not only with regard to the customary evaluation criteria, but also in terms of waste reduction. This resulted in our making four changes to the original design:

> Pre-fabricated reinforced concrete stairwells instead of an in-situ traditional construction;
> Post-tension flat slab construction instead of in-situ ribbed slab
> Use of paired displacement auger piles instead of single flight auger piles
> Reuse of excavated car park material in piling mat.

The savings
The next stage was to quantify the potential savings of making these design changes. The cost, waste and environmental impact of a notional base design and optimised solution were calculated by taking into account the total construction cost of the design, the quantity of waste produced, the cost of waste disposal and the value of materials wasted. Combined, the four waste alternatives were assessed as saving £166,625 and diverting 2,610 tonnes of waste from landfill. Additional benefits included 142 fewer lorry trips – either delivering material or removing waste from site – and savings in the embodied CO2 of wasted materials. HMCS has now incorporated the procedures across its estate.

As a business, we found that Wrap’s process enabled us to consider the implications of design on waste production and assesses this in an objective, measurable and comparable way. If our experience is anything to go by, securing buy in from our clients and peers is one of the most challenging aspects of DoW, and using tools like WRAP’s design detailing sheets and the new Outline Design Tool for Buildings (www.wrap.org.uk/designers)  can help us quantify the potential cost and environmental savings on offer via design decisions.

Yasser el Gabry is regional director at Aedas