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The project was completed on time in 28 weeks. However, Asda is now consulting a private building control agency to standardise substructure design after problems identified in the management of substructure work. It expects to reduce substructure costs 22% and knock at least a week off the usual four-week substructure programme.

The project was finished for £8m – 8.5% less than its projected budget. It cost Asda £75 000 to implement the ImPACT monitoring system.

John Connaughton is a partner at Davis Langdon Consultancy and is chair of the Innovation and Research Committee of the Construction Industry Council

Information technology has a key role to play in providing rapid and detailed analyses of site processes as they happen. The ºÚ¶´ÉçÇø Research Establishment's Calibre system and the ºÚ¶´ÉçÇø Services Research and Information Association's productivity measurement tool both use IT in this way. These systems concentrate on feeding information back to the site management team so that it can take prompt action to resolve poor performance.

ImPACT goes further by incorporating the professional advice of the management consultants operating it. Whatever the system, it is important to note that they are labour-intensive: two construction managers on site full time is a big monitoring resource. And, although I think they should be considered for all major projects, the choice of system should be carefully evaluated in terms of its merit and cost.

At Mansfield, it is important to distinguish between the benefits that arose from monitoring and those that resulted from more general lessons about design management and co-ordination. Clashes between trades as a result of late design information, for example, are among the oldest problems in the book. Fall-outs can be avoided by planning rather than by monitoring.

Martyn Jones is principal lecturer in construction management at the Faculty of the Built Environment at the University of the West of England

Superstore construction has improved substantially over the past few years. Teams have cut times from inception to completion and reduced defects and cost, but the Mansfield project team and GDG Management have shown that there is scope for still better performance.

Looking behind the cost reductions and other improvements on this project, there is evidence of good practice to support continuous improvement. For example, close and effective monitoring provided robust measures of performance. Also, clear and challenging improvement targets were set and tools were put in place for identifying and weeding out barriers to improvements – on site and upstream in the project.

But how transferable is this good practice? Clearly, as a frequent user of construction services, Asda can build and sustain ongoing and stable relationships with partners. These relationships can support continuous improvements in reducing waste, adding value, sharing learning, reshaping processes and developing mutual advantage. However, there are difficulties that need to be taken into consideration when applying this approach in other sectors of the industry – most notably, who leads improvement in the case of less experienced and irregular clients?

Colin Gray is head of the University of Reading's Department of Construction Management and Engineering

All the supermarket groups have been undertaking improvement programmes over the past few years. Some have progressed further than others. This store seems to be at the beginning of the process, but others, such as the Sainsbury's Ecostore in Leigh, Lancashire, have achieved radical change. Sainsbury's has already reduced costs on mainstream stores by 35% and cut construction times to 15 weeks. At the Ecostore, costs were reduced by a further 32% (details of how are given in Reading Construction Forum's Seven Pillars of Partnering).

Work study analysis is a very useful basic tool for productivity measurement. Simpler, although less precise, tools are also available. These show up delays and their causes very effectively, and in a timescale that allows management to take action. However, site problems are largely the result of failures in the supply chain, and it is here where most effort should be made.

To attempt this level of change within a traditional set of relationships between parties is optimistic. If the same firms are used for the next project, their experience will be transferable. But if the programme expands and new partners are introduced, the lessons learned may be lost.

Impacting productivity levels

The £8m Asda store, designed by Chesterfield-based WCEC Architects, was completed for £600 000 less than the budgeted cost. GDG Management claims the savings were inspired by its time-and-motion study. The savings also include the cost of GDG's monitoring.

GDG employed two full-time staff on site every day to monitor contractors. These two construction managers, who cost about £400 a day, used GDG's ImPACT system for measuring productivity.

Consultants time specific tasks with a stopwatch and record the resources used for the quantity of work on a clipboard. They also record the factors that slow progress down.

Initially, the consultants simply attempt to establish a baseline by monitoring. They measure the performance of several shifts, then identify the productivity of the best. The difference between the best shift and the baseline is the achievable best and should be, says GDG director Graham Clarkson, about 50% of the theoretical ultimate. This hypothetical productivity is when workers don't take statutory breaks, always have the correct materials to hand, and never have to chase design information.

Once the consultants have established what the contractors can achieve, they start feeding back their findings. And as construction professionals, they can identify technical and management problems, and talk to workers about them with authority.

For instance, says Clarkson, GDG found the groundworks contractor could save a week and a half from a four-week programme and cut costs by 22% by adopting two measures.

The best day's groundworks productivity resulted in a cost for excavating foundation bases of £6.16/m³. But the worst day's productivity was £39.46/m³. ImPACT showed that the best day's levels were not achieved because of poor building control management and poor design information management.

The groundworks contractor was prevented from pouring concrete foundations until the local authority building control inspector visited the site to approve the excavations. The inspector only visited once a day, restricting the amount of foundations that could be laid, said Clarkson. Contractors also ended up reworking excavations that fell in because they were left too long between inspections, he added. As a result of ImPACT, Asda is now employing a private building control consultant who will be on site constantly during the substructure works.

Finalising the foundation design also hindered progress on the groundworks. It was the first time Laing had worked on an Asda project and finalisation problems are expected to diminish as understanding grows. "We established that by tackling these two issues, the works could have been completed for £8.85/m³," says Clarkson.

In the excavation and construction of underground drainage to food preparation areas, Clarkson catalogued errors that seriously eroded productivity. The landscape contractor also clashed with the design team. By the time it had started on site, the drainage contractor had already set out its blocks and sent workers to another site, rather than waiting. When design modifications were received later this led to a stand-off until the blocks were moved again.

And that is not all. The drainage contractor suggested design changes that would have reduced waste, but the designer refused to alter the detail. After two days' work, the designer changed a detail that meant all the work had to be removed and reworked.