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It's a dirty job . . . The Environment Agency could do more to help bring brownfield land back into use, says David Bennett.

COVER STORY

As the Urban Task Force recognised, conversion from brownfield to clean land is progressing too slowly to meet demand for the 4 M new homes needed by the year 2016.

Owners of brownfield sites and their engineers would be delighted to clean them of contamination and recycle the land for development but give up trying to remediate the contaminated soil in situ, the most practical solution, because of the restrictions that are applied to remedial treatment.

The most common complaint is that legislation operated by the Environment Agency relating to brownfield land is currently biased in favour of disposal to tip - regardless of the cost and long term impact on the environment.

Pushing the problem onto another landfill backyard fails to recognise that soon we will have only landfill backyards left to build on.

And, as the cost of removing all contaminated land off site could well exceed the likely revenues from the cleaned land, it makes development uneconomic and perpetuates the brownfield problem.

Technologies like lime stabilisation and cement encapsulation exist to treat and reuse contaminated soil in situ but contractors have huge problems persuading the Environment Agency and its consultants to accept that they work. When on site remediation is permitted, contractors and landowners find that they have to apply for a licence as if they operated a contaminated landfill tip with all the extra cost and paperwork that entails.

May Gurney remediation specialist Chris Wallace sums up the dilemma for specialist contractors trying to work with the current legislation. 'We are essentially carrying out in-situ treatment of contaminated land and not carting contaminated land off site. Yet we have to apply for a licence to run and manage a waste operation that requires a two year training course for supervisors as would be required by any landfill operator or a sewage treatment works. It is wholly inappropriate.'

According to a senior Environment Agency spokesman, any well engineered, long term solution for dealing with contaminated land is given serious consideration. But the onus must be on the vendor to demonstrate that the process and scheme it intends to adopt and manage will adequately contain and encapsulate the contamination and eliminate any risk of leakage. Will the scheme function effectively for 100 years, for example, if the contamination remains?

Often the structure of cut-off walls can only be guaranteed for a 40 year design life, so the two timescales may be incompatible

'There can be no risk taking when dealing with remediation treatment of contaminated land. The potential harm to water courses, aquifers and arable land in the long term cannot be tolerated,' the Agency says.

The Urban Task Force last week called on the Environment Agency to harmonise its regulation and licensing of remediation techniques and companies; the EA should resolve conflicts and inconsistencies between different environmental regulation systems covering contaminated land, water and waste, and produce a single set of standards, it said.

The difficulties that currently exist may ease when overdue guidance notes on remediation of contaminated land from the Department of Transport Environment and the Regions are published - hopefully at the end of the year - and the1995 Environment Act is amended to recognise in situ remediation.

Tannery tale

The Environment Agency did relax its approach and allow on site remediation without demanding that the project acquire a landfill tip licence at Gomshall Tannery in Surrey on land for new houses being built by Fairview New Homes.

The four acre former tannery site was contaminated to a depth of up to 5m in localised areas by hydrocarbon solvents, degreasing agents, acid waste and chromium salts. Drainage trenches were installed along the river boundary to intercept seepage of any contaminants and the oil-based pollutants

were drawn off. Soil on the site was checked for contamination during excavations and all clean material stockpiled to be re-used, while localised areas of contaminated hot spots were excavated and carted away.

'Essentially we created a 3m layer of clean material over the site, capped by a 1.5m layer of compacted clay and then 500mm of topsoil over the garden areas,' says consultant Dr Geoff Card of Card Geotechnics.

'We estimate the cost of remediation was 80% less than disposal costs and that excludes the cost of importing fill.'

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