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Difficult ground: the biggest excuse in the book Large cost overruns due to insufficient site investigation still dog the construction industry. Matthew Jones asks why.

QUESTION:What is the definition of a tunnel?

ANSWER:A long hole in the ground with an optimistic engineer at one end and two or three lawyers rubbing their hands at the other.

That is the level of humour when ground engineers get together. But judging by the report in last week's NCE which highlighted that England's seven largest road projects are a staggering £516M over budget - largely due to 'unforeseen ground conditions' - the joke actually seems to reflect construction quite fairly.

The variability of ground conditions has been known about as long as civil engineering has been recognised as a discipline. Yet on project after project it seems, civil engineers launch deep into the unknown with only so much as a cursory look at what lies below the surface.

Transport Research Laboratory senior project manager Dr John Temporal co-ordinated the last study into the efficiency of site investigation practices in 1994. He found that outturn costs on half of the 21 road schemes examined exceeded tender value by more than 23% - and half of these increases were due to geotechnical factors.

While Temporal feels that there has been a steady reduction in cost overruns due to poor ground investigations since, he adds: 'I don't see a revolutionary change - we've still got a long way to go.'

He claims that there are still many designers who give scant regard to the importance of establishing what is below the surface and says that all too often little effort is put into using site information which is already available.

This view is backed up by research carried out in 1991 for the Institution of Civil Engineers by Professor Stuart Littlejohn. He found that the amount of money spent on ground investigations tends to depend on the discipline of the professional leading the work and the type of client. Typically the amount ranged from 0.3% of the tender value for government clients to as little as 0.1% for developers and builders.

Seven years later, Littlejohn now claims that inadequate site investigations are still occurring due to lack of geotechnical expertise, inadequate focus of finance and too little time being spent at the start of the project.

He adds: 'I'm not saying that we should be necessarily throwing more money at this, just that we should be thinking more carefully about how ground investigations are carried out.'

Littlejohn says that rather than sinking one or two boreholes to get a micro-view of the ground conditions, it is better to carry out a thorough desk study to find out the history of a site. But because of fierce competition for contracts, consultants often minimise the amount spent on this work.

He also reckons that too few clients understand the importance of site investigation, and that designers and contractors should be urging them not to skimp on up-front costs.

'We should be saying that the cost of the site investigation could be up to 1% of the scheme value so that clients are fully prepared and understand the logic,' he says.

Less adversarial forms of contract and partnering arrangements should help this process.

Christiani & Nielsen managing director and deputy chair of the Construction Confederation Alan Crane believes that the sooner traditional contracts such as the ICE 5th edition drop out of circulation the better. And he believes that more opportunity should be given to allow contractors to do ground investigation once a contract has been awarded.

'This may mean that the client has to pay more, but it should provide more certainty and better value for money,' he says.

A more sensible philosophy already exists in the offshore industry where poor site investigations can prove not just costly, but catastrophic. Clients are much more tuned in to the construction risks, and consequently no project gets beyond the drawing board without a rigorous risk analysis.

How to apply this approach to construction will be the subject of a new research project being launched by the ICE next month. Called Managing geotechnical risk, it is part-funded by the DETR and will focus on early planning and contract management procedures, as well as risk analysis techniques.

Project director Neil Trenter explains: 'Insufficient site investigation is the biggest single factor which contributes to cost overruns. If you take a main works contract, many millions of pounds are often at stake, yet civil engineers carry out a fraction of the back-up and risk analysis undertaken for a finance or insurance deal.'

He claims that risk analysis should not just be reserved for mega-projects, but should be applied to all construction schemes - add up the cost increases on a dozen small schemes and you have a large amount of money.

The project team will hope to draw lessons from high risk industries such as banking and finance by conducting a series of meetings to find out what kind of risk analysis techniques they use. One useful spin-off may be that the meetings will give bankers a forum to voice concerns over the industry's ability to control risks - judging by construction's past record it will be a dialogue worth having.

Too many large infrastructure schemes have foundered in the past because civil engineers failed to convince those holding the cash that such risks were under control. It is perhaps high time that the industry swallowed its pride, listened to the money men and stopped taking a leap in the dark.

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