KIER PROPERTY is one of the UK’s top commercial property developers. As leaders in brownfield development it is no stranger to contaminated land and strives to ensure its sites are effectively and efficiently remediated.
The introduction of The Landfill Directive is having a huge impact on the way in which the construction industry is disposing of its waste.

The technique of “dig and dump” once provided a cheap, quick and easy way for contractors to remove contaminated land from a site to a landfill. The new legislation heralded a rapid decrease in the number of landfill sites licensed to dispose of hazardous waste. This decrease meant that dig and dump was suddenly an expensive option with increasing gate prices and associated transportation costs.

The Landfill Directive aims to reduce the environmental impact of landfills by avoiding the disposal of raw, untreated wastes, which may produce hazardous leachates. It also reduces biodegradable wastes that produce methane and ensures that landfill sites are engineered, monitored and controlled.

The Hazardous Waste Directive has resulted in the cessation of a practice known as codisposal of hazardous wastes in which the hazardous waste is mixed with non-hazardous waste to dilute it.

Now there are vastly reduced numbers of landfill sites that are licensed to take hazardous waste and there are none in London or Wales.

As a result this has cost implications with rising charges at the gate and increased transportation costs. Such increases have made dig and dump uneconomical with respect to other treatment methods.

With this in mind, property developers and contractors are keen to find new ways in which to treat contaminated land quickly and costeffectively on site. Kier Property purchased the former gasworks site in Uxbridge for redevelopment and is committed to meeting exacting environmental targets. The company deems it important that it uses an environmentally-friendly method of remediation on their sites.

Kier Construction and Kier Property, both part of the Kier Group, look for specialists in the remediation field to provide them with a technology that is safe, effective and reaches risk assessment targets in a specified timescale.

Kier Construction has excavated approximately 22,500m3 of contaminated soil, which it moved to the treatment pads for remediation company Biogenie to undertake onsite bioremediation.

Kier Construction and Biogenie worked closely together at the excavation face to ensure that the differing contaminated areas and materials where identified and sent to the appropriate treatment pad, so avoiding any cross contamination.

The bioremediation treatment process relies on natural micro-organisms in the soil breaking down the hydrocarbon contaminants. Soil is treated in four dedicated biopiles where the environmental conditions are controlled and optimised to stimulate microbial activity and effect rapid breakdown of even the most complex hydrocarbons.

Control of available oxygen, carbon to nitrogen ratios, humidity and pH within the biopile are crucial to achieving risk assessment targets in sensible timescales. Emissions from the biopile are also controlled and regularly monitored to ensure that the biopile has a low environmental impact.

The contaminated soil once treated to risk assessment targets can then be re-used on the site as the bioremediation process employed by Biogenie does not affect the soil’s structural integrity. Kier Construction aims to maximise the amount of soil re-used in the development and this will generate estimated savings of approximately £2m – by eliminating landfill disposal, transportation and imported material costs.

Dr Graham Holtom, general manager of Biogenie Site Remediation, says: “Our experience of operating biopiles across the world allows us to accurately assess what types of contamination can be treated and predict the timescales required to achieve set risk assessment targets.

“We have had many years of experience and have treated many millions of tonnes of contaminated soil from over 1,000 sites across the world, so we were confident about offering fixed prices and performance guarantees to Kier construction.

“In addition, on such a small site it is important that we work closely with Kier to ensure that our treatment fits their excavation and build programme.

“We believe that a good remediation contractor should be able to use technologies that minimise disruption to the build programme while delivering to risk assessment targets within a specific timeframe.”

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