Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.

Your browser appears to have cookies disabled. For the best experience of this website, please enable cookies in your browser

We'll assume we have your consent to use cookies, for example so you won't need to log in each time you visit our site.
Learn more



Air quality initiatives to reduce engine emissions go way beyond existing European standards and the impact on contractors could be significant.

Environmental issues continue to grow in importance. The treatment of contaminated land, recycling of materials, minimisation of material going off site to landfi ll and the reduction of noise are all issues with which ground engineering and piling contractors are familiar.

But there is one issue on the environmental agenda whose impact is less widely appreciated - engine emissions.

The European framework is well known (see box). These directives are in line with leading international standards, such as the US Environmental Protection Agency (EPA) Tier 3 requirements.

Any contractor buying a new machine could be forgiven for thinking that it complies with the latest, toughest regulations. This may no longer be enough and change is in the air. The EU has published air-quality objectives for 2010 and many big cities - notably London, which is at the bottom of the European league table on air quality - are heading for failure.

In a bid to avoid this, mayor of London, Ken Livingstone has developed an air-quality strategy. On the back of this, in November 2006 the Greater London Assembly and the London borough councils published Best practice guidance: The control of dust and emissions from construction and demolition.

The guidance will be used to inform the planning process within London boroughs; assisting developers in understanding methods available to them and what London boroughs may expect. It sets out conditions planning officers may wish to consider when granting consent to projects.

Most of the measures are already widely used, such as provision of wheel-washing facilities and other dust-suppression measures. Possibly onerous for many plants owners is the requirement that all diesel-powered machinery should meet the latest European standards. No old machines, thank you.

It also states that 'ultra-low sulphur diesel equivalent fuel should be used at all sites whenever possible'.

There is also a requirement that 'non-road mobile machinery with power outputs of over 37kW should be fi ted with suitable after-treatment devices', which means diesel particulate fi ters (DPFs), selected from an approved list.

What this means is that to use a pre-Euromot III (the European Association of Internal Combustion Engine Manufacturers) machine in London, it will probably have to change its engine and put an approved DPF on it. Even the latest shiniest rig will still need a retro-fi tted DPF. As far as London is concerned, the European standards may not go far enough.

This zeal might be justified by estimates produced in 1999 showing that nitrogen oxide (NOx) emissions from diesel off-highway plant in the UK were 71,000t (about 8% of all road transport emissions) and 7000t of total particulate matter (PM) emissions (16% of road transport emissions).

According to the Construction Plant Hire Association (CPA) DPFs cost anything from £1500 to £6500 per machine for a basic ceramic monolith fi lter with cordierite filter material. More sophisticated filter systems can cost up to £10,000.

While it will be up to each local authority to decide whether to impose this requirement, the Olympic sites and Thames Gateway projects will require compliance with the new guidance.

The CPA lobbied hard but unsuccessfully against adoption of the guidance. It argued that, aside from the cost, a key practical problem with DPFs is keeping them working effectively. They need to be 'regenerated' at least once a shift.

This involves stopping work, taking apart the fi lter and burning off the carbon deposits. Equipment needs to be available for this procedure and operators need the necessary training. It is possible to add controls that warn when the filter needs regenerating or even to shut off the engine at the required time, but this will only add extra cost.

There are other practical difficulties. Each DPF needs to be specifi cally designed for the make and model of the machine it will be fitted to. Also, warranties will be made void by fi tting DPFs unless it is done in co-ordination with the original manufacturer.

Environmentalists point out that retrofi ting DPFs has proved successful on projects in other countries, such as in Switzerland and on Boston's Big Dig project in the US.

However, in both cases there were grants made available to plant owners to help cover costs. This is not happening in London.

A report by Euromot and the Engine Manufacturers Association into the Swiss experience was less than reassuring: 'The experience of Switzerland's contractors and equipment owners has not been satisfactory to date.

'They report many problems related to the use of particulate filters in retrofit applications including premature failures, high installation and operating costs. . . it is important for legislators, equipment operators, engine and emission control equipment manufacturers to work together to provide proven and feasible solutions to PM reduction.'

There is a similar rumpus going on in California, where the California Air Resources Board is proposing banning all machines over 10 years old and ordering a mass retrofi t programme. Other parts of the US write air quality requirements into specifi c contracts, including the $6.6bn (£3.3bn) O'Hare Modernisation Programme in Chicago and contracts let by New York City.

What is happening in London might soon become adopted by other UK local authorities with a green agenda. Some contractors have already worked on sites requiring special measures. Keller had to fi t catalytic converters to its rigs when it worked on London's O2 Arena (formerly the Millennium Dome) recently.

Several piling contractors have only a vague awareness of the London Best Practice Guidance, believing it would be suffi cient to deploy new rigs with Euromot III engines.

This may not go far enough for clients demanding the strictest compliance with best practice guidance.

'We are aware of the issue, ' says Graham Hall, contracts manager of sheet piling specialist Fussey Piling.

'All we can do is buy the most modern plant available.

'If they ask us to put catalytic converters or diesel particulate filters on, there could be issues in altering the specifi ation and voiding the warranty. But if we, as a company, need to do it, we shall do it.'


A 1997 Directive set out Stages I and II of engine emission levels.

A 2004 Directive requires Stage IIIA to reduce nitrogen oxide (NOx) levels by December 2005 to December 2007 depending on engine size. This reduction is being achieved by engine manufacturers modifying their designs.

Stage IIIB requires reduced particulate levels by December 2010 to December 2012 and will require diesel particulate filters (DPFs) to be added to engine exhaust systems.

Stage IV requires a further significant reduction of NOx emissions by December 2013 to 2014 and will be achieved by further developments of exhaust systems.

Have your say

You must sign in to make a comment

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Please note comments made online may also be published in the print edition of New Civil Engineer. Links may be included in your comments but HTML is not permitted.