APPENDIX 2
Memorandum submitted by Dr Colin Hills,
University of Greenwich
HAZARDOUS WASTE
INQUIRY AND
"ON SITE"'
TREATMENT OF
CONTAMINATED SOILS
BY CEMENT/BINDER-BASED
STABILISATION/SOLIDIFICATION
(S/S)
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.
INTRODUCTION
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.
ANOMALY
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.
CONSEQUENCES FOR
SUSTAINABILITY
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."
SOLUTION
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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