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NOBEL GESTURE

CONTAMINATED LAND

An old landfill site in the West Midlands is taking the first steps towards recovery, after a geotechnical investigation paid for by the current owner of the firm that operated it 30 years ago.

Things are finally looking up for an old landfill at the junction of the Coventry and Oxford canals in the West Midlands. Blighted by derelict buildings and fly-tipping of asbestos among other materials, the former Hawkesbury Tip had a high profile with the local community for all the wrong reasons.

Set up in 1935, the site was owned and run by Courtaulds which used it for waste from its viscose rayon works in Coventry. Courtaulds sold the site in 1973 and it was used as a commercial landfill until 1979.

The landfill was in poor condition, with exposed automotive and other industrial waste, potentially unstable slopes and standing water in a 2000m2 lagoon. Ownership changed frequently after closure and the site deteriorated. Buildings became structurally unsound and fly-tipping took place. Access was uncontrolled and locals began using it as an unofficial amenity area.

Among those worried by the state of affairs were Nuneaton and Bedworth Borough Council, the Environment Agency and Bob Ainsworth, MP for Coventry North East.

Particular problems were the potential health hazard posed by asbestos, organic and inorganic components of surface waste and the potential for structural failure of the tip. This could have damaged the canals or discharged leachatecontaminated water into the nearby Wyken Slough nature reserve.

Meanwhile international coatings, healthcare and chemicals company Akzo Nobel, which had acquired Courtaulds in 1998, many years after the sale of the Hawkesbury Tip, became aware of concern about the site. In 2004 it contacted Ainsworth and the regulatory authorities, offering to support a geotechnical investigation to evaluate the stability of the site and any risks it might pose.

Key aims were to determine whether immediate action was needed and develop a set of data and understanding of the site that would help decision-making on its long-term future.

Akzo Nobel appointed Environmental and Remediation Services to manage an investigation team. This included Euro Dismantling Services as principal contractor, Environmental Simulations International (ESI) as lead soil and groundwater environmental firm and geotechnical consultancy Edge Consultants.

Work was worth over £750,000.

The main site investigation began in May 2005. Electrical conductivity and resistivity surveys were carried out before most of the intrusive investigation work, providing information about the thickness and nature of the waste.

Trial pits, cable percussion boreholes and geoprobes were put down across the site. Three rotary boreholes were sunk to about 18m on the perimeter to determine the nature of the natural superficial geological deposits and bedrock at the site boundaries.

Ground conditions were up to 3.7m of made ground, underlain in landfilled areas by a 6-12m thick waste layer. Natural ground comprised a 5-16m layer of glacial till, predominantly stiff clay, over Sherwood Sandstone - sandstones and mudstones. Regionally, the Sherwood Sandstone is 10-40m thick and underlain by Carboniferous Coal Measures.

Surface water, sediment and groundwater sampling and landfill gas monitoring were used to build up a detailed picture of contaminants and identify any potential pathways to receptors.

To allow safe investigation work, large quantities of illegally tipped materials were removed to licensed landfill and dangerous structures demolished. The team also reprofiled a terraced slope along one side of the lagoon to improve its stability and reduce the risk of people or animals falling into the water.

The investigation and risk assessments finished in December. Further groundwater monitoring will be carried out this winter and spring to determine seasonal changes in ground and surface water levels.

The team found that except for the slopes around the lagoon, there was no significant risk of the landfilled mass failing. The environmental risk posed to the canals, the nature reserve, other surface waters and groundwater is also low, because of the geology and differential water levels between the landfilled area and elsewhere.

For use as informal amenity land, the team demonstrated the risk to human health was small because contaminants detected were of low mobility and site users would receive very limited exposure to them.

Similarly, rapid dispersion of landfill gases on the open site and the absence of gas migration pathways to nearby structures means the risk from landfill gases is not a current concern.

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