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Contaminated land

The government's new plan to build 60% of new houses on brownfield land means the remediation of contaminated land may become more of an issue for contractors. Developers should not be fearful of dealing with contaminated land, it can often be easily and quickly cleared. However ignoring contamination, or aiding or causing the spread of contaminated land can carry severe penalties.

Why is contaminated land good practice important?

If contamination is likely to be encountered the construction contract should define the methods of dealing with it. The contract will usually refer to the guidance issued by statutory authorities on how to deal with contamination.

Figure: Stakeholder groups involved in contaminated land

Ground contamination may result in the following problems:

• Health and safety impacts on staff and surrounding community through exposure to contaminants.
• Liability for the cost of disposal or remediation of contamination (depending on contract conditions).
• Liability for costs arising from unexpected spreading or making existing contamination worse.
• Delays to the programme through unexpected or accidental contamination.
• Pollution of groundwater and surface water courses.
• Pollution of surrounding land.

There are two key requirements in managing ground contamination:

• Do not cause it or spread it.
• Deal with it appropriately.

Key issues include

• Generally, ground contamination is present as a result of previous uses of the site (or adjacent land), for example industrial land use or waste disposal. Be aware that incidents during construction may also cause ground contamination.
• Further contamination may be caused by handling or excavating contaminated ground -for example where impermeable ground is penetrated and therefore creates a pathway for contaminants to enter an aquifer below.
• Disturbing unexpected archaeological finds, such as burial grounds, may pose a health risk to the workforce.
• Initially, the responsibility lies with the client for carrying out a site soil survey and deducing the risks from any contamination that may be present. However, the contractor is advised to check whether this has been done satisfactorily.

How to avoid further contamination

Checklist - avoiding causing or spreading

• Do not stockpile contaminated soil unless it cannot be avoided. If it is necessary, stockpile only on a hardstanding area to prevent contamination of underlying ground. It may be necessary to cover over stockpile material, either to prevent windblown dust or to prevent ingress of rainwater.
• Control surface drainage from stockpiled area. Water draining from a stockpile may be contaminated and need controlled, off-site, disposal.
• Prevent the spread of contaminated dust.
• Be careful when handling, storing and using oils and chemicals.

Figure: The pollutant linkage controlling contaminant movement

What to do if contamination is encountered

During boring, digging, excavating and similar operations, observe the uncovered ground and watch out for visual signs of contamination. The release of noxious fumes (petrol, oils, solvents, chemical residues) and smells may also indicate contamination (eg a smell of bad eggs may mean that hydrogen sulphide contamination is present).

A major housebuilder and two other defendants were ordered by the Crown Court to clear 270 lorry-loads of waste containing PCBs and oil that had been dug out from a redundant gasholder and illegally dumped on farmland

Checklist - visual signs

• Discoloured soil (eg chemical residues).
• Fibrous texture to the soil (eg asbestos).
• Presence of foreign objects (eg chemical/oil containers).
• Evidence of previous soil workings.
• Evidence of underground structures and tanks.
• Existence of waste pits.
• Made ground (ie artificial ground where ground level is raised by man’s activities and not due to a natural cause).
• Old drain runs and contamination within buildings; tanks, flues etc.
• Topsoil adjacent to motorways can be contaminated by traffic emissions.

Examples of good practice

Covering up problems permanently does not get rid of them! When contamination is suspected do the following:

• Stop work immediately seal off the area.
• Report the discovery to the site manager the site manager should seek expert advice.

If asbestos is uncovered re-cover it temporarily to prevent its release to the atmosphere. If there is a risk of spreading contaminated dust, temporarily cover the source or dampen it down.

Key references:

• BSI Draft for Development DD 175: 1988 Code of Practice for the Identification of Potentially Contaminated Land and its Investigation.
• CIRIA R132 A guide for safe working on contaminated sites.
• CIRIA C578 Brownfields, managing the development of previously developed land. A clients guide.
• HSG66 Protection of Workers and the General Public during the Development of Contaminated Land, HSE.
• Link to CIRIA Contaminated Land Web.

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