Select Committee on Environment, Food and Rural Affairs Appendices to the Minutes of Evidence


Memorandum submitted by Dr Colin Hills, University of Greenwich


Waste Management Licensing anomaly in the UK

Executive summary

  There is an anomaly in the way that the EA currently implements "enforcement positions" under its "Guidance on the application of waste management licensing to remediation". The lack of an "enforcement position" for the "ex-situ" process of binder-based stabilisation/solidification of contaminated soils poses both an unnecessary threat to HMG's targets for the re-use of brownfield land and to the scarce landfill resource. The CCLR at the University of Greenwich submits and requests that the enforcement position that is justifiably applied to the use of the "in-situ" process should be widened to include the ex-situ process.


  Contaminated soils can be remediated by mixing with cementitious binders that chemically stabilise contaminants and create a matrix that solidifies the soil thus physically trapping pollutants whilst improving engineering properties. This technology can be applied using two on site treatments referred to as "in-situ" and "ex-situ"; these are generic terms as there are no definitions under current legislation. Generally in-situ treatment is undertaken by mixing the soil with binders in the ground whereas ex-situ treatment consists of temporarily excavating the soil, mixing with binders in equipment such as a pug mill and then replacing the treated soil. Both technologies are subject to Mobile Plant Licensing (MPL) requirements.


  Currently, the in-situ treatment, when performed under an MPL, is subject to an enforcement position under "Guidance on the application of waste management licensing to remediation", Version 2, January 2001 from the Environment Agency, which allows the treated soil to remain on site without the site being subject to a Waste Management Licence. This enforcement position does not apply to ex-situ treatments when carried out under an MPL, consequently a site to be remediated by this method will be subject to a Waste Management Licence. This additional requirement places ex-situ technologies at an unjustifiable disadvantage to in-situ processes and will, the CCLR submits, hinder rather than assist HMG in meeting its policy objectives for the reuse of brownfield land.

  In fact, assuring the quality of ex-situ treatments is far more demonstrable than for in-situ treatments. Mixing can be easily observed and the mixing equipment employed can produce better more homogeneous mixes. In addition, samples for analysis for process quality control can be taken easily and quickly. Conversely, treatment of soils in-situ is less easy to assess and may be less effective, whereas it is the more robust ex-situ methods that are currently penalised by the lack of an enforcement position.

  As an indication of the potential for the regeneration of brownfield sites using ex-situ processes, it was found under the USEPA Federal Superfund initiative, 1982 to 1999, that 25 per cent of all the sites were remediated using stabilisation/solidification; of these sites, 24 per cent employed in-situ technology with the majority, 76 per cent, using ex-situ technology.


  In the UK, the construction sector has active enquiries for the regeneration of brownfield sites using ex-situ methods, however, it is likely that the volume of soil so implicated will be disposed of to landfill, instead of being remediated on site, because of the lack of an enforcement position for the ex-situ process.

  If evidence were needed that disposal to landfill is not a sustainable solution in the longer term, then the Royal Commission's report on Environmental Pollution "Sustainable Use of Soil" has provided it. The Report concludes that "removal to landfill is unsatisfactory from the environmental point of view, not only because it does not eliminate the contaminants, but because it spreads contamination from the existing site to a fresh site and adds to environmental costs by creating a new demand for transport."


  The CCLR at the University of Greenwich requests that the EA's enforcement position be widened to cover ex-situ s/s treatments in order to assist both the construction sector and HMG in meeting the latter's targets for the re-use of brownfield land and in minimising unnecessary disposal to the scarce landfill resource. Qualifying conditions to the enforcement position could include:

    —  a requirement that the process has a Mobile Plant Licence;

    —  an assurance that work will be performed to current good practice;

    —  a requirement that treatability studies be undertaken and a robust risk assessment agreed with the regulator.

  To promote good practice, the Environment Agency has commissioned CASSST (Codes and Standards for Stabilisation/Solidification Technologies, led by the CCLR at the University of Greenwich) to produce guidance to cover both in-situ and ex-situ technologies, which is due to be published during winter 2002/spring 2003.

Colin Hills

University of Greenwich

May 2002

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