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Ground Engineering: Contamination conundrum

Remediation technologies have advanced in the last 20 years, but the classification of what levels of contaminants are actually harmful to health is still very much a grey area.

Development of brownfield sites in the UK over the last 20 years has helped to allow major developments to go ahead that would not have been permitted on virgin ground. This process of regeneration has led to the development of innovative remediation techniques that have helped to reduce the legacy of contamination from historic use.

But issues regarding what levels of contaminant are deemed acceptable are now coming to light and are leading many industry experts to question if this clean-up work has actually been cost effective. Although the contaminated land industry should be reaching maturity, there are still too many questions about what levels are actually harmful to health and whether current guidelines are too strict.

A long way

“We have come a long way in 20 years in terms of our understanding, but it is disappointing that we are this far on but are not able to clarify what we are trying to do,” says Peter Brett Associates partner Richard Puttock.

“By that I mean that the government has gone to consultation on updating the Part 2A of the Contaminated Land Regime of the Environmental Protection Act from 1990, which was updated in 2006, but there is still no understanding of what it means in terms of contaminant levels that are acceptable for planning purposes.”

The Contaminated Land Exposure Assessment (CLEA) model as part of the technical guidance developed by Colin Ferguson for the government was published in 1997 and is still used as the main reference for contamination decisions. Before the CLEA model, the UK used a mix of the figures from the Inter-Departmental Committee on the Redevelopment of Contaminated Land (ICRCL) report, published in 1983, and the Dutch Standards that gave target and intervention levels.

“Various parties want to define what we need which may include defining specific values”

The publication of the CLEA model was expected to resolve the issues of acceptable contamination levels with soil guideline values (SGVs), but Puttock says this was not the panacea the government had hoped it would be. “We are not really any further forward than when the ICRCL report was published in 1983,” he says.

Puttock says the problem with Part 2A is that a large part of it comes down to the toxicology which is based on providing absolute safety and using this doesn’t fit with the levels that pose significant possibility of significant harm. “It also still doesn’t give the values you need to base planning decisions on as they are generally too conservative for this as well,” he adds.

Clearer guidance

It is clear that local authorities and regulators need figures on which they can base decisions and developers also need clearer guidance on what is and isn’t viable so they can plan investments. “Various parties like the Environmental Industries Commission, Society of Brownfield Risk Assessment and local authorities want to define what we need which may include defining specific values,” says Puttock. “A lot of work in producing the missing SGV-type numbers is being repeated and, as everyone is using similar data, the results they are getting are also similar but this is still not the data that is necessary for planning or Part 2A.”

“The UK government seems to fear a legal challenge but this is at odds with the way it handles similar issues in other industries”

According to Puttock, part of the problem centres around that lack of understanding of background levels of contamination. “Take, for example, the natural higher levels of arsenic in Cornwall,” he says. “If the CLEA guidelines were used for arsenic there then the whole of Cornwall would need to be remediated.

“It is only recently that the limitations of the 1997 guidance are starting to be fully understood.” Puttock also points to the issue of benzoapyrene, which is formed when organic material, such as food on barbeques, is burned. “The SGV levels for benzoapyrene are too conservative and if applied strictly then a large part of the UK would be classed as contaminated,” he says. “So either the whole nation is being poisoned by benzoapyrene or the levels have been set too low.”

Risk assessment

The UK is not alone on the issue of tackling contaminated land but other nations that have also taken a risk assessment based approach have actually adopted numbers to judge what is acceptable. “The UK government seems to fear a legal challenge if it takes the same route but this is at odds with the way it handles similar issues in other industries - the use of pesticides in the food industry and the air quality values are an example,” says Puttock.

“The real challenge is for science to give answers on the toxicology of contaminants, the uptake and also the impact that other sources may have on individuals”

Nonetheless, Puttock believes that academia, industry and the regulators can solve the problem, although there are a number of policy issues that also need to be addressed to make this successful. “There needs to be some determination of what level of expenditure on remediation is acceptable, maybe in context of the site value but also in terms of actual impact on health,” he says.

“It would have to be an iterative process where a standard is established, the costs are looked at and then the aims can be revised. Take lead as an example - it is known to have an adverse effect on IQ so it was removed from petrol to prevent ongoing pollution but how much should be spent on cleaning up sites? Where is the epidemiological evidence to show health effects from a certain level of contamination in the soil?”

“It is possible for industry to help define parameters, but government funding is needed to achieve this and it is frustrating that there is a resistance to go down this route.”

Puttock believes that by looking at the CLEA model the results could easily be changed by a factor of two, three or four and maybe by as much as 10, which isn’t enough. By looking at the toxicology and considering other inputs and epidemiology, then factors of 100 or 1,000 may be acceptable without impact on human health. “The real challenge is for science to give answers on the toxicology of contaminants, the uptake and also the impact that other sources may have on individuals,” he says.

“It is possible for industry to help define parameters, but government funding is needed to achieve this and it is frustrating that there is a resistance to go down this route. This goes against history such as the use of BSI to establish other standards where the organisation - both before and after privatisation - has always drawn on the knowledge of practitioners to lead standard development.”

Difficult times

The lack of progress since 1997 on the issue leads Puttock to wonder how much remediation has been undertaken that was not really needed and how much material has been sent to landfill that actually could have safely remained on site.

“The result is a high cost to the UK as a country,” he says. “In difficult economic times you still want to keep people safe, but by making the right decision for the right reasons but I wonder to what extent an over-cautious approach to contamination is stalling development in some areas that could help improve the economy.”

Puttock says engineers have always helped protect society with health improvements to offer better protection in the future, but he wonders whether it would be better to spend the money on providing better healthcare and ready access to fresh food in deprived areas instead of on intensive remediation. “We are a long way from understanding the true health benefits of cleaning up contamination,” he says.

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