Remediation on Track at Former
'Dirtiest Site in Europe' ALcontrol Group Head Office
Units 7 & 8 Hawarden Business Park Manor Road, Hawarden, Deeside Flintshire CH5 3US UK
Tel: +44 (0) 1244 528 700
Email:
hawarden.sales@
alcontrol.com Website:
www.alcontrol.com
The Avenue former coking works located 3km south of Chesterfield, Derbyshire, England is a prominent site known internationally by the remediation and civil engineering sectors. Much has changed both on the site and in waste management / environmental permitting since Construction News, in July 2006, described The Avenue as 'The dirtiest site in Europe.’
www.theavenueproject.co.uk
Exceeding 80 hectares, the site operated for 36 years as a coking works and had a long and varied industrial history prior to this use. In addition to the production of smokeless fuels the site also processed the by-products from this process and as well as receiving wastes from other National Coal Boards sites in the region. As such, the site possibly lives up to the Construction News tag by being contaminated with a range of sulphur compounds, creosote, blended fuel wastes, benzoles, tars, asbestos and spent oxides.
The last charge of coke was processed in September 1992 with the works closing shortly after in
the October. Ownership passed through English Partnerships (now the Homes and Communities Agency – HCA) to East Midlands Development Agency (emda) which is managing the remediation and landscape works that are being funded by the HCA as part of their National Coalfields Regeneration Programme.
VSD - a joint venture consortium comprising DEC (DEME Environmental Contractors – the Belgian based Environmental Contractor), Sita Remediation (a Dutch based thermal desorption specialist) & Volker Stevin (the civil engineering contractor) were awarded the £82million remediation and landscaping contract in July 2009 and works commenced in earnest during the summer of 2010.
The analysis of environmental samples is being undertaken by ALcontrol using a web-based system known as '@mis' which enables the scheduling of analytical work and provides live access to laboratory results.
Remediation strategy
The key objective of the remediation is to remove the existing site contamination through onsite treatment and to deliver a restored landform which will provide significant benefits for the local
community along with the provision of environmental enhancement and a flood alleviation scheme protecting areas of Chesterfield from future flooding. The restored landform will include a development platform and significant areas of public open space including sports pitches, public footpaths and other public amenity facilities. This new landform has been designed to be sympathetic to the surrounding environment and to create habitats that will further encourage a diverse wildlife population including many protected species which will be encouraged to make the restored site their new home. The remediation and landscaping packages will be completed in 2014.
Before the remediation works commenced, a large amount of enabling works were carried out. As well as works to divert existing services within the site, one of the most visible elements of works has been the construction of a large coffer dam and a temporary river crossing in the floodplain area of the River Rother at the northern end of the site.
The volumes and types of contamination associated with the project have not previously been seen in the UK - over two million cubic metres of material are being excavated with a significant volume of this having to be processed. The majority of the material requiring processing arises from the two contaminated settlement lagoons and the formerly licensed waste-tip.
The lagoons alone require over 200,000m³ of very heavily contaminated sediments to be excavated and processed. To add to the complexity of this activity, the lagoons were not only built either side of the river Rother, but the waste tip had also been formed above one of the lagoons.
Due to the toxic nature of the contaminants present in the material from both the lagoons and the waste tip, thermal desorption has been identified as the most appropriate treatment method. This sees the sediments put through a kiln at temperatures of up to 500°C to remove contaminants, which volatilises the contaminants of concern. The off-gases are further oxidised, scrubbed and filtered to comply with stringent emission limits.
The thermal desorption plant is the largest ever used in the UK. Due to the high temperatures associated with operating the plant, it operates 24 hours a day and will run until the autumn of 2012, only stopping for maintenance.
The windrowing of a further 75,000m³ of hydrocarbon contaminated material has commenced and will operate for the majority of the project.
Groundwater on the site is contaminated with phenols, thiocyanates, benzene and ammonia; where this presents at surface it is treated on site using a bespoke water treatment facility which uses a combination of chemical dosing, active filtration and biological treatment. This ensures that the contaminated waters that are collected can be discharged safely.
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www.pollutionsolutions-online.com • February / March 2011
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