The jury is still out on the new CLEA guidelines for assessing contaminated land.
Geotechnical and geoenvironmental engineers and consultants involved in the assessment of contaminated land will have spent the past few weeks digesting the recently published and long awaited Contaminated Land Exposure Assessment (CLEA) guidelines.
The new guidelines replace the much maligned ICRCL 59/83 and relate to the assessment of risk to human health arising from long term exposure to soil contamination. They are intended for use in conjunction with, for example, an assessment of risks to groundwater.
'It was generally hoped that the CLEA model would allow consultants and engineers to exercise a far greater degree of judgement in their assessment of risk. Unfortunately, this may not be the case, ' says Steve Branch, managing director of geoenvironmental specialist LBH Wembley.
The CLEA documents present Soil Guideline Values (SGVs) for the relevant contaminants on the basis of four land use categories:
residential with and without plant uptake, allotments and commercial/industrial. In general, the guidelines provide a single SGV concentration of each contaminant for each land use scenario.
Not so different then to the old ICRCL 'trigger values'. Branch says: 'It is likely that local authorities will use the SGVs in the same way as the former ICRCL trigger levels and leave little scope for judgement on the part of the geoenvironmental consultant.'
Paul Nathanail of Land Quality Management at the University of Nottingham also sounds a note of caution: 'We are all in for a bit of heavy reading to understand the technical basis of the CLEA guideline values and avoid repeating the misuse of the ICRCL values.'
One area of encouragement, says Branch, is the acknowledgement that naturally occurring contaminants in the ground, can be assessed on their 'bioavailability'.
Bioavailability testing, he explains, essentially attempts to replicate the way in which the particular contaminant is broken down in the human body.
'Acceptance of bioavailability testing will allow the use of the method in situations where an initial screening of total concentrations reveals exceedance of one or more SGV, ' says Branch 'including sites where the contamination is not from natural sources'.
The hope is that use of such testing, supported by a proper assessment of the risks in accordance with the new CLEA model, may at last allow geoenvironmental engineers to adopt a more informed approach to the effects of soil contamination.