Last month Roger Braithwaite looked at issues around strategy formulation for the new contaminated land regime. This month he looks at the complex processes necessary to decide whether or not land should be declared statutorily contaminated

Following publication of the formal contaminated land strategy, each local authority will need to survey its district to identify potentially contaminated sites. Prioritisation must be employed to ensure resources are concentrated in areas where contaminated land is most likely to be found. Surveying the district will be a long and time-consuming task, with the results invariably digitised and held on geographical information systems. When priorities have been confirmed and the local authorities have access to sufficient resources, the first on-site investigations will begin.

The draft guidance(2) makes it clear that the local authority must consult fully with all parties who may have information on the condition of the land and the potential for impact on known receptors.(4) One of the principal aims of the act is to protect water resources. In the UK a significant proportion of potable water is drawn from ground sources. Each time an aquifer becomes contaminated it may become unusable for generations. New protocols being devised over the next few months will provide guidance on how local authorities and the agency will work together to identify land which may affect groundwater, inland freshwater, the sea and coastal waters within 3 miles (controlled waters).(3) Information held by previous or present owners, potential developers and other authorities (where contamination may cross boundaries) may also be sought in an attempt to minimise the impact of the investigation process.

When it comes to on-site investigation, this may include walk over surveys, on-site testing, geophysical analysis, and ultimately intrusive work such as boreholes or trial pits. If a single pollutant linkage(1) is established and the land declared contaminated, the local authority is advised to stop there and commence the enforcement process. There may be many more pollutant linkages but further investigation may be required as part of a remediation notice.

Who Should Undertake Investigations?
Investigation must be carried out by "suitable persons". This is not defined in the draft guidance and there are no plans to define the term in future, or to prepare a list of approved consultants and contractors. Local authority and Environment Agency officers will have to work closely together to ensure no embarrassing misunderstandings occur.Local authority strategies will have considered whether the authority's own officers are "suitable", or whether training and experience may be needed. Selection criteria for outside contractors should also be included in the strategy.

With regard to sites which, if contaminated, would be declared special sites(5), the local authority must authorise a suitable Environment Agency officer to investigate on its behalf. For example, where an authority is aware that part of its district overlies lower Permian basal breccias, conglomerates and sandstones, and that these may be affected by substances on the land which possess carcinogenic, mutagenic or teratogenic properties, they should notify the agency immediately.(6) If, like many, you would have trouble in telling your Permian breccias from your Jurassic corallians, there may be a temptation to seek to hand over large areas of investigative work to the agency. If that is the case, be warned - it won't work. The agency will have its work cut out investigating legitimate enquiries, and the local authority must take part in and manage all contaminated land investigations as it must make informed decisions on whether land is statutorily contaminated, regardless of who carries out the site work, and regardless of whether it may be a special site or not.

Where the local authority wishes to authorise a third party to undertake investigations, it has powers under section 108 of the Environment Act 1995 to do so (statutory powers of entry). This can involve entering premises (includes land), taking samples or related activities for the purpose of enabling the authority to determine whether land is contaminated. It should be noted that the agency does not have this power, so, where both agree that there is a potential for a pollutant linkage to exist, and where the land may then be declared a special site, the agency must apply to the local authority to appoint a third party.

How should investigations be undertaken?
Local authorities must follow appropriate technical procedures and take all reasonable precautions to avoid creating pollutant linkages during that process. Specifications for investigative work must be prescriptive and unambiguous and require adherence to a quality assured procedure which will bear scrutiny in the event of dispute (such as an appeal). Local authorities may devise their own site specific procedures, or require compliance with approved guidance such as British Standards(7) or Contaminated Land Research Reports.(8) It should be remembered though that the guidance itself is, by necessity, open to considerable interpretation.

DD(draft for development) 175 - 1988, the British Standards Institution Code of Practice for the Investigation of Potentially Contaminated Sites, will be a familiar document to those working in the field. The new draft published in September 19989 supercedes this. The publication of the fully fledged code of practice was timed to coincide with the introduction of Part IIA but, like most of the guidance, it has been called in again and will not be available until the summer at the earliest. At this stage, significant technical changes are not anticipated. Although the new draft replaced DD175, it is emphasised that the document should not be regarded or used as a British Standard.

Clear objectives must be set for each investigation. The most straightforward will arise where there is only one potential receptor. Complexity will increase as other receptors and exposure routes are identified, eg land contaminated by sewage sludge which could affect property (crops or livestock), groundwater, surface water, ecosystems, or humans. Local authorities should identify all potential pollutant linkages and consider conceptual models which will justify the investigation process. The specification must require the investigator to obtain data incrementally and terminate the process if it becomes clear that pollutant linkages do not exist. It would not be appropriate to extend the process to consider the impact of the site on future receptors; that should be undertaken at the town planning stage.

A simple example of an investigation would be a closed petrol station suspected to have lost fuel from underground tanks. The preliminary desktop survey may have identified the area underlain by mudstone, which should be relatively impermeable. At depths of 180 to 200 feet a minor sandstone aquifer exists, but contamination of this by light non-aqueous phase liquids (LNAPLs) is declared "unlikely" by the agency. The most significant receptors are property in the form of underground services, which are known to run through the site, and human, via pvc water mains.
The objectives of any investigation may be to:
1. identify subterranean structures and pathways
2. identify all potential receptors
3. create an accurate conceptual model of the site
4. identify contaminants in the soil, their spacial distribution and concentration.

Some local authorities may choose to present contractors with a list of objectives like this and ask them to produce a quality assured investigation strategy. If so, officers must ensure they have the time and ability to evaluate proposals carefully. Ideally they should produce detailed specifications, considering the potential pollutant linkages in detail, the contaminants of most concern, sampling methods, frequency and techniques, and laboratory analysis. It is important that there should be a high level of confidence in the data produced before the next process commences.

RISK ASSESSMENT
Once the quality assured data has been obtained and hazards identified, it must be assessed in respect of each pollutant linkage. The local authority has the sole responsibility for determining whether any land appears to be contaminated. Having identified hazards in the form of contaminants,(11) specified receptor(s) and ways the two may come together, a basic risk assessment has already been undertaken. This does, however, need to be extended to produce a formal assessment(12) that will satisfy the needs of the act.
Some of the difficulties inherent in the process can best be demonstrated by simple examples.

1. Is broken glass contamination?
It is a substance(13), it is on land, and it may undoubtedly cause harm to known specified receptors (human beings). It is the duty of the risk assessor to decide whether the harm, if it occurred, would be significant and whether the potential for such an effect would also be significant.
Significant harm to a human being includes death or serious injury; a child running and falling on glass could easily sustain serious lacerations, which could result in rapid loss of blood and potentially, death. The potential for significant harm is therefore confirmed.
With glass we are not considering toxic effects, but "other human health effects", which must be taken into consideration. These relate particularly, but not exclusively, to fire and explosion, so could it be appropriate to consider lacerations? Assessments must be made on authoritative and scientifically based information consistent with providing appropriate protection from the risk. If the assessor considers the chances of the significant harm occurring are significant, the land must be declared contaminated. If not it may be declared "land in a contaminated state", which is defined as, "land where harm is being caused or there is possibility of harm being caused". Such land is then exempt from statutory nuisance action.

2. Are yew berries contamination?
Yew berries are extremely toxic to animals, including humans, they also look like sweets. They are substances as defined14 and could cause significant harm (including death) to humans or property (includes livestock). If a large yew tree in the village churchyard deposited hundreds of toxic berries on the land next door, placing known receptors at significant risk, could the land be declared contaminated?

3. Is asbestos contamination?
A more conventional example; an old scrap yard, that has taken all types of metals and scrap over decades, has been left abandoned in a residential area. The public has open access and youths use it as a BMX and motorcycle scrambling track. Residents have complained of the dust blowing off the site, especially when the scramblers are racing.
Initial investigations reveal the yard took a lot of steel fire protected with friable asbestos. The men used to scrape this off by hand and "dispose of it". Exploratory soil samples reveal significant counts of blue, white and brown asbestos fibres at the surface.
Again, you have one contaminant, one receptor, clear pathways, an undoubted pollutant linkage. There is masses of authoritative and scientifically based information on the human health effects of airborne asbestos, but no safe limit. It must be contaminated land, but are there circumstances when it may not be? Would it be possible to suggest that significant harm could occur, but that it was so unlikely it presented an insignificant risk?
There will be a temptation to employ costly modelling processes in an attempt to deliver accurate scientific judgements. Where, however, there are several dozen potential contaminants on one site, accuracy may have to be sacrificed to sound judgement due to a shortage of reliable human toxicity and exposure data.
The same applies to water and "eco" risks where expertise on hydrogeology, leaching potential, soil chemistry and environmental fate and impact, is at a premium. Local authorities will consult their partners such as MAFF, the Forestry Commission, the National Parks authorities, English Nature and the Environment Agency etc, but few will have specialist risk assessors to help.

CONCLUSIONS
Risk assessment for contaminated land is a confusing mix of concepts and methods borrowed from sociological, psychological and technical disciplines. No single process provides all the answers, and often there are none. As a result, when it comes to judging a risk, most people would rather trust the opinion of a friend than take the word of a scientist(15).

Scientific risk assessment is slow, cumbersome and expensive. It attempts a degree of precision that is invariably unachievable and often unnecessary. The results are at best suspect, at worst, dangerously wrong. Ultimately, the long-suffering but, hopefully, pragmatic local authority officer will have to use the wisdom of Solomon to make the final decision on whether the site is statutorily contaminated. The outcome could on the one hand blight a whole housing estate in perpetuity, on the other, leave a generation of children at significant risk.
What price a friend now?

References
References to the 'Circular' relate to Draft DETR Circular - Environmental Protection Act 1990: Part IIA Contaminated Land, September 1999
1. Pollutant linkage is defined in the Circular as the relationship between a contaminant, pathway and a receptor.
2. The Circular, Annex 3.
3. Water Resources Act 1991 section 104.
4. Receptor is defined in the Circular at Annex 3, Chapter A, Part 3.
5. Special Sites defined in Reg 2, Contaminated Land (England) Regulations 1999.
6. Reg 3 and schedule 1 of the draft Contaminated Land (England) Regulations 1999 describes when pollution of controlled waters requires Special Site designation.
7. British Standard 1377: 1990, Method of test for soils for civil engineering purposes; British Standard 5930: 1981, Code of practice for site investigations; British Standard 6068: (several), Water quality; British Standard 7755: 1995, Part 3 Pre treatment of samples for physico-chemical analysis.
8. DETR Contaminated Land Research Reports: CLR 1 A framework for assessing the impact of contaminated land on ground and surface water; CLR2 Guidance on preliminary site inspection of contaminated land; CLR4 Sampling strategies for contaminated land. Available from DETR publications unit Rotherham.
9. Draft code of practice for the investigation of potentially contaminated sites, 1998.
10. After Ferguson C et al 1998 - Risk Assessment for Contaminated Sites in Europe, Volume 1, Scientific Basis, Published by LQM Press Nottingham.
11. Contaminants are defined in the Circular as substances in, on or under the land which have the potential to cause harm or to cause pollution of controlled waters.
12. Risk is defined in the Circular as the combination of: a) the probability, or frequency, of occurrence of a defined hazard (eg exposure to a property of a substance with the potential to cause harm); and b) the magnitude of the consequences.
13. Substance is defined in the Circular as any natural or artificial substance, whether in solid or liquid form or in the form of a gas or vapour.
14. New Scientist 28th September 1996.