ICRCL Guidelines

N.B. 14/01/2003  DEFRA have now formally withdrawn the guidance on the health effects of contaminated land given in ICRCL Guidance Note 59/83 (2nd edition). The source information is still available from DEFRA on request to aid understanding of historical decisions on the remediation of contaminated sites but it should not be used in the assessment of new sites. All new decisions should be based on CLEA 2002.

The United Kingdom Interdepartmental Committee for the Redevelopment of Contaminated Land (ICRCL) was set up in 1976 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 mainstay 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 a range of inorganic contaminants and substances associated with coal carbonization works 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 judgment".

INTERPRETATION OF ICRCL "TRIGGER CONCENTRATIONS"

ICRCL TENTATIVE "TRIGGER CONCENTRATIONS" FOR SELECTED INORGANIC CONTAMINANTS

CONDITIONS

1. This Table is invalid if reproduced without the conditions and footnotes.

2. All values are for concentrations determined on "spot" samples based on an adequate site investigation carried out prior to development. They do not apply to analysis of averaged, bulked or composited samples, nor to sites which have already been developed. All proposed values are tentative.

3. The lower values in Group A are similar to the limits for metal content of sewage sludge applied to agricultural land. The values in Group B are those above which phytotoxicity is possible.

4. If all sample values are below the threshold concentrations then the site may be regarded as uncontaminated as far as the hazards from these contaminants are concerned and development may proceed. Above these concentrations, remedial action may be needed, especially if the contamination is still continuing. Above the action concentration, remedial action will be required or the form of development changed.

NOTES:

* Action concentration will be specified in the next edition of ICRCL 59/83

1. Soluble hexavalent Cr extracted by 0.1M HC1 at 37°C; solution adjusted to pH 1.0 if alkaline substances present.

2. The soil pH value is assumed to be about 6.5 and should be maintained at this value. If the pH falls, the toxic effects and the uptake of these elements will be increased.

3. Determined by standard ADAS method (soluble in hot water).

4. Total concentration (extractable by HN₃/HC10₄)

5. The phytotoxic effects of copper, nickel and zinc may be additive. The trigger values given here are those applicable to the ‘worst-case’: phytotoxic effects may occur at these concentrations in acid, sandy soils. In neutral or alkaline soils phytotoxic effects are unlikely at these concentrations.

6. Grass is more resistant to phytotoxic effects than are most other plants and its growth may not be adversely affected at these concentrations.

ICRCL TENTATIVE "TRIGGER CONCENTRATIONS" FOR CONTAMINANTS ASSOCIATED WITH FORMER COAL CARBONIZATION SITES

CONDITIONS

1. This Table is invalid if reproduced without the conditions and footnotes.

2. All values are for concentrations determined on "spot" samples based on an adequate site investigation carried out prior to development. They do not apply to analysis of averaged, bulked or composited samples, nor to sites which have already been developed.

3. Many of these values are preliminary and will require regular updating. They should not be applied without reference to the current edition of the report "Problems Arising from the Redevelopment of Gas Works and Similar Sites". 

4. If all sample values are below the threshold concentrations then the site may be regarded as uncontaminated as far as the hazards from these contaminants are concerned and development may proceed. Above these concentrations, remedial action may be needed, especially if the contamination is still continuing. Above the action concentration, remedial action will be required or the form of development changed.

NOTES:

NL. No limit set as the contaminant does not pose a particular hazard for this use

1. Used here as a marker for coal tar, for analytical reasons. See "Problems Arising from the Redevelopment of Gas Works and Similar Sites" Annex 1

2. See "Problems Arising from the Redevelopment of Gas Works and Similar Sites" for details of analytical methods

3. See also BRE Digest 250: Concrete in sulphate-bearing soils and ground water