GUIDELINE / SCREENING VALUES FOR CONTAMINATED SOILS

On these pages you will find three sets of values, the UK ICRCL and ‘Kelly’ guideline values, together with the Dutch intervention values

*The UK ICRCL have been augmented with suggested action levels for the metals*

PLEASE NOTE
IT IS EXTREMELY IMPORTANT TO READ ALL THE NOTES WITH THE LISTS

UK ICRCL

In 1976 the United Kingdom Interdepartmental Committee for the Redevelopment of Contaminated Land (ICRCL) was set up to consider the problems associated with the development of contaminated sites. In a few years the committee published comprehensive guidance documents on:

• The development and after use of landfill sites - ICRCL 17/78
• The redevelopment of gasworks sites - ICRCL 18/79
• The redevelopment of sewage works and farms - ICRCL 23/79
• The redevelopment of scrap yards and similar sites - ICRCL 42/80
• The assessment and redevelopment of contaminated land - ICRCL 59/83
• Fire hazards of contaminated land - ICRCL 61/84
• Asbestos on contaminated sites - ICRCL 64/85
• The restoration and aftercare of metalliferous mining sites for pasture and grazing - ICRCL 70/90

These were continually under review with some having as many as eight editions in only twelve years. They were, and still are, very useful documents, and have formed the main stay of UK contaminated land guidance over two decades.

One difficulty has always been the quantification of contaminants in soils and the concentration at which the chemical forms a risk to known targets. This is no less a difficult question now as it was twenty years ago. To assist in the risk assessment process the committee developed TENTATIVE Trigger Concentrations for 19 contaminants plus pH. These contaminants were chosen as those most likely to form a risk from seven identified hazards (ref: table 2 of ICRCL 59/83). The trigger values define three possible concentration zones:

1. Below the ‘threshold’ value, the site can be regarded as uncontaminated.

2. Above the ‘action’ value, the presence of the contaminant has to be regarded as undesirable or even unacceptable, so some kind of remedial action is unavoidable.

3. Between the two values, there may be a need to consider the contamination and take action where circumstances demand it. The decision to do so should be based on "informed judgement".

Clearly the use of the trigger values requires considerable skill and judgement on the part of the ‘expert’ using them. Unfortunately this has not always been the case and they have been used in an arbitrary fashion as target values. This problem has been exacerbated by the fact that, despite promises, ‘action’ values have never been developed for 10 of the metals, so some advisors and enforcement authorities have chosen to use ‘threshold’ values instead.

The links below provide full lists for the three references mentioned above

BUT INCLUDED IN THE ICRCL LIST ARE SUGGESTED ACTION VALUES FOR THE METALS

THE UK ‘KELLY’ TABLE

In October 1979 Mr R T Kelly, the then scientific advisor to the Greater London Council (GLC) delivered a paper entitled, Site Investigation and Material Problems, to the Society of Chemical Industry Conference on the reclamation of contaminated land. In this paper he considered the risks to several recognised targets. He produced several useful lists, but only one is regularly reproduced which is entitled:

"Guidelines for Contaminated Soils - Suggested Range of Values (mg per kg) on air dried soils - except for pH"

Used initially by the GLC this was quickly adopted by many waste regulation authorities in the UK as well as the Health & Safety Executive. In the link below we have reproduced not only this table but a typical list of staged determinations and an example of the range of results that may be obtained from a single site.

THE DUTCH INTERVENTION VALUES

The UK Government have always believed that a site should be in a fit state for its purpose. So, if land was derelict and not in use, it should merely not pose a risk to water resources or other known targets. That is to say, it should not be in such a state as to be prejudicial to health or a nuisance (part III of the Environmental Protection Act 1990). In Holland, however, the Government sought to improve contaminated land so it would be suitable for any potential use. This lead to the development of guideline values for a range of 57 contaminants (including 11 PAHs) known as the, ‘ABC Values’. These were subsequently refined to form the, ‘Target and Intervention Values’, for 67 contaminants, but this time the PAHs were summed.

The interpretation of the values is very similar to that of the UK ICRCL values.

1. The TARGET VALUE is the baseline concentration value below which compounds and/or elements are known or assumed not to affect the natural properties of the soil.

2. The INTERVENTION VALUE is the maximum tolerable concentration above which remediation is required. This occurs if one or more compounds in concentrations equal to or higher than the intervention value is found in more than 25 m³ of soil or 1000 m³ of ground water.

3. The MIDDLE VALUE - (target value + the intervention value) x 0.5. This is regarded as a threshold value for further investigation.

ADJUSTMENTS TO VALUES FOR DIFFERENT SOIL TYPES

Target and intervention values vary according to the clay and organic matter content of the soil. The formulae for these has been included with the notes on the table.

Click here for the ICRCL tables
Click here for the Kelly Tables
Click here for the Dutch Tables