The SPOSH test in Part 2A contaminated land decisions

Part 2A of the Environmental Protection Act 1990 defines contaminated land partly by reference to a phrase that practitioners shorten to SPOSH: a significant possibility of significant harm being caused. It is the legal threshold at which a local authority can determine land as contaminated, with all the consequences that follow, and it sits a long way above the level of risk that planning conditions deal with every day.

Developers meet the phrase most often when a consultant's report uses it to explain why something is not a problem. Understanding why the test is set so high explains why almost all land contamination in England is handled through the planning system instead.

Where the phrase comes from

Part 2A was inserted into the 1990 Act by the Environment Act 1995 and creates a duty on local authorities to inspect their areas to identify contaminated land. Land qualifies where it appears to the authority to be in such a condition, by reason of substances in, on or under it, that harm is being caused or there is a risk of harm at the statutory level, or that pollution of controlled waters is being caused or is likely.

The words carry a deliberate weight. Harm has a statutory meaning covering harm to human health, to property in the form of crops, livestock and buildings, and to specified ecological systems. Possibility is about likelihood. Both have to reach the level the statutory guidance describes before a determination can be made.

The Defra statutory guidance supporting the regime sets out categories for assessing whether the test is met, running from cases where the authority should determine the land through to cases where it clearly should not. The intent is that only the more serious end of the spectrum is caught.

The statutory regime compared with planning

Two systems deal with contaminated land and they operate on different premises.

Part 2A is retrospective and remedial. It looks at land as it is, asks whether it poses unacceptable risk in its current use, and if so identifies who must pay to fix it. It is used sparingly, because determination is resource intensive and triggers liabilities that authorities are careful about.

The planning system is prospective and preventive. National policy places responsibility on the developer to ensure land is suitable for its proposed use, and authorities discharge that through conditions requiring investigation, remediation and verification. The standard is that after development, the land should not be capable of being determined under Part 2A for its new use.

That second point is the one to hold onto. Planning does not aim to remove all contamination. It aims to break the pollutant linkages that matter for the intended use, which is why a car park and a nursery garden on the same ground attract entirely different requirements.

Source, pathway and receptor

The regime works on pollutant linkages. A linkage needs three elements present and connected: a contaminant source, a pathway by which it can reach something, and a receptor capable of being harmed.

Break any one of the three and the linkage is broken. That is what most remediation actually does. Capping breaks the pathway. Removing hotspots removes the source. Changing the layout so that gardens sit away from a former works removes the receptor from the route.

Conceptual site models exist to set out those linkages explicitly, and a model that lists substances without connecting them to receptors is not doing its job. The contaminated land assessment is the document where that model lives, and it should be legible to a planning officer who is not a chemist.

Categories used in a determination

The statutory guidance groups cases into four categories for human health risk. The clearest cases at one end should be determined, the clearest at the other should not, and the two middle categories carry the judgement. Only the first two categories support a determination.

Assessment uses published screening values where they exist, including generic assessment criteria derived for particular land uses, alongside site-specific risk assessment where the generic values are too blunt. Exceeding a screening value does not by itself mean the test is met. It means more work is needed, which is a distinction consultants sometimes state clearly and clients sometimes miss.

For controlled waters the analysis runs differently, looking at whether pollution is being caused or is likely, with the Environment Agency taking the lead on the more serious cases.

A determination also has consequences beyond remediation. The land goes on the authority's public register, which lenders and insurers read, and the stigma outlasts the clean-up by years. Sites designated as special sites, including some former defence and chemical works, pass to the Environment Agency as the enforcing authority. None of that is a reason to hide a problem, but it is a reason to deal with contamination through a planning condition and a verification report while you still control the timetable.

Why a planning condition is the usual route

Three practical reasons authorities prefer conditions.

The first is timing: a condition bites before people move in, whereas Part 2A bites years after. The second is liability: under Part 2A the appropriate person may be the original polluter, or, where none can be found, the current owner or occupier, which is a fight authorities would rather avoid. The third is proportionality: a condition can require an investigation proportionate to the risk, and can be discharged in stages.

The familiar condition sequence is a desk study and preliminary risk assessment, then intrusive site investigation and risk assessment, then a remediation strategy, then a verification report confirming what was done. Each stage is submitted for approval before the next begins, and the last one is the stage most often forgotten until a purchaser's solicitor asks for it.

Ground conditions work for foundations runs alongside this and often uses the same boreholes. Combining the intrusive investigation for a geotechnical assessment with the contamination sampling saves a mobilisation and produces a coherent ground model.

What a Phase 1 report should conclude

A desk study should end with a conceptual site model and a clear statement of whether potentially unacceptable pollutant linkages may exist for the proposed use, and therefore whether intrusive investigation is needed.

What it should not do is declare the site clean. A desk study cannot do that, because it involves no sampling. Reports that conclude "no contamination is present" on the strength of historic maps alone get rejected by environmental health officers, and rightly.

Where the answer is that investigation is needed, the report should scope it: which substances, which media, how many locations, and what the analytical suite should cover. That scope is what the authority approves, and a vague scope produces a vague investigation.

Land contamination reports at both phases are expected to be prepared in accordance with the recognised investigation standard by suitably qualified and experienced persons. This is one of the areas where a licensed or competent professional is legally expected and an AI-assisted draft is a starting point for that professional rather than a substitute for them.

This is general guidance rather than legal advice, and contaminated land determinations carry serious liabilities, so check the position with your local authority or a qualified contaminated land specialist before relying on it.

If you are working out which ground-related documents your scheme needs, the report index groups them by category. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.