THERE was speculation earlier this summer that the implementation of the EU Landfill Directive would have a near-paralysing effect on the construction industry, and the foundation sector in particular.
But, against expectations, the world did not stop turning on July 14. Is it too early to tell or did the sector overstate the problem? What has been the impact of the Landfill Directive?
Certainly the cost of disposal of hazardous waste has increased dramatically.Whereas previously the disposal costs of hazardous and nonhazardous wastes were similar, since July hazardous waste disposal costs have increased by a factor of four.Disposal of non-hazardous waste, in contrast, has remained broadly the same.
Jim de Waele, operations director at Stent, puts the issue into perspective.'We only come across four or five sites a year where there is a bad contamination issue - that is about 1 per cent of our sites, ' he says.
So, for the vast majority of sites, the specific impact of the Landfill Directive is a bit of a non-issue. But set against a general background of high landfill disposal costs and the gathering momentum of sustainable construction, the shape of the geotechnical industry is changing.The assumption is that displacement methods which reduce the quantity of spoil have the advantage.
Martyn Singleton, marketing director of Keller Ground Engineering, certainly believes this to be the case.'There has been increasing pressure over the last 18 months to minimise the volume of spoil removed from site, ' she explains.
Although the Landfill Directive may not have made that much difference to the economics of most projects, John Chantler of Pell Frischmann says that spoil disposal has become more of an issue since July.
'It has certainly concentrated minds in terms of how much spoil is generated and how you dispose of material off site, ' he says.
Mr De Waele points out that there is one important exception where the directive's impact is significant.
The directive precludes disposal of liquid wastes, such as bentonite slurries, which now have to be pre-treated - a costly and time-consuming process.
This, for instance, makes boring large-diameter piles under bentonite particularly problematic and Mr De Waele predicts that the landfill directive will accelerate the switch to biodegradable polymer muds, which (following very simple treatment) can be disposed of into sewers.
Stent, he reports, has now moved over entirely to polymer muds.'It's a steep learning curve, ' he says, 'but once you understand how to use it, it offers geotechnical advantages over bentonite.'
Chris Thomas, business development manager for Bachy Soletanche, says recent market analysis has shown no perceivable change in favour of one foundation method over another since the summer.
The fact is that other issues come into play and these typically override the spoil disposal problem.
'Concerns about noise and vibration are absolutely critical in city sites, ' says Tim Chapman, associate director at Arup.'Restrictions on working hours imposed by environmental health officers mean that if work is not done by the quietest practical means, then the construction programme will be severely compromised.'
And it's not just about noise.'In London, most construction work tends to be too close to sensitive buildings for driven piling to even be an option, 'he adds.
Back in June, there was even concern that basement construction jobs may become uneconomical. But Mr Chapman insists that this is not the case, so far.
'I haven't come across any project yet where the basement size and depth have been affected by the new landfill regulations, ' he says.
'Generally the costs of installing basements in London is already high, so an increase in spoil disposal rates is more of a marginal effect than it would be elsewhere.'
Pell Frischman's Mr Chantler agrees that London is a special case, adding that there is not an obvious alternative choice; you simply have to pay the price.
'We haven't hit a brick wall yet, where the spoil disposal costs kill the job, but we can see it coming, ' he says.
THERE are three main types of displacement piling: precast driven, helical or auger displacement piling, and driven cast-in-situ piling.
In terms of market share, driven piling is by far the most significant lowspoil technique. It presently accounts for about 20 per cent of the UK piling market.This compares with the most common piling technique, continuous flight augering, which accounts for approximately half of the piling sector.Auger displacement and driven cast-in-place methods are still highly specialised niches.
Precast driven piling PRECAST concrete piles are essentially the modern equivalent of driving timber tree trunks into soft ground - a process that dates back at least to the Roman Empire.
Until the development of larger-diameter bored piling in the 1950s and 1960s, most foundation piling was some kind of driven displacement method. But, as building loads started increasing, bored methods swung to prominence.
Perhaps the pendulum is poised to swing back in favour of driven methods, and not just because installation is essentially spoil-free. Precast driven piles are manufactured in a factory-controlled environment; quality control is much greater and material wastage is significantly less than castin-place piling methods.
Because of the factory environment, precast piles can carry higher stresses than cast-in-place methods. Consequently, the dimension of the pile is determined wholly by the geotechnical conditions, rather than its ability to transfer the loads.
The big problem with driven methods is noise and vibration, and this is an area that the industry needs to address if the method is going to take significant market share from bored methods.Nevertheless, a number of equipment manufactures and contractors have found some impressively effective ways of reducing noise during pile driving.
Helical or auger displacement piling THIS is the new kid on the block, at least to the UK market. Belgian professor Willie Van Impe is the godfather of the method.He developed the original Atlas screw pile and then the Omega pile, arguably the first (almost) no-spoil auger displacement system.
May Gurney Geotechnical introduced the Omega pile to the UK in the early 1990s and since then a number of other UK contractors have developed variations on the helical auger displacement theme. But market share is modest, because it is expensive compared with continuous flight auger piling.
There are technical constraints, too.The method needs very high-energy rigs to displace the ground, and wear on tools and equipment is greater than with other techniques.
The system is probably most appropriate when moderately high loads are needed on contaminated sites.
When May Gurney first got involved in the system, director Chris Heath wondered why, despite quite similar soils, over 90 per cent of the auger piles in Belgium and The Netherlands were formed by displacement methods, pushing the soil sideways, while in the UK over 90 per cent were formed by conventional augered methods - primarily continuous flight augering.
He observed, at the time, that 'the root cause is the cost of disposal of spoil.Once it has been established that spoil is not desirable, the rest follows' If this assertion proves correct, then auger displacement piling could well be about to have its day.
Driven cast-in-place piling sacrificial steel toe plate) into the ground and filling it with concrete from the top. But what was once 'crude' is now considered 'robust', and rising spoil costs have unquestionably given the method a new lease of life.
Landfill directive ANY SITE with hazardous waste is a big problem.The cost of disposal has shot up fourfold in the past couple of months, with 'gate prices' of between £60 and £100 per tonne being bandied about.
The EU Landfill Directive put a stop to the practice of co-disposal, in which landfills accepted both hazardous and nonhazardous wastes. Since July, landfill operators have had to decide whether they take one or the other.
Unsurprisingly, most landfills have gone for the nonhazardous option and there are now just a dozen or so sites across England and Wales that can take hazardous waste.
Little wonder that their gate prices have gone up.
Haulage costs have shot up too.Not only are the haulage distances much greater but it seems the hauliers recognise an opportunity when it presents itself and have hiked up rates for carrying hazardous waste.
Non-piling alternatives There is an argument that the spoil disposal issue is encouraging groundimprovement techniques such as dynamic compaction, vibro compaction and deep soil mixing.'With the exception of organic materials like peat, most problem soils are competent materials in a loose state, ' explains Martyn Singleton, business development director at Keller.'If you can make them denser, you improve their engineering characteristics.We should be thinking about using soil more creatively than bypassing the problem with piles.'