Tired and tested technology
The majority of land reclamation schemes in the UK still rely heavily on straightforward excavation or encapsulation to clean up contaminated sites. Innovative Treatment Technologies (ITTs) apply chemical, biological or physical processes to destroy, change or remove contaminants from soil or water to render them immobile. Whilst such technologies have gained much wider acceptance in other EU countries and in the US, their acceptance within the UK has been restricted. Mike Dinsdale and Tim O'Hare of Mayer Environmental Services Ltd examine some of the reasons why.
Conventional excavation techniques are 'certain' (at least that is the received wisdom): a once-and-for-all solution. A developer can quantify the cost of removing contaminated material and the time it will take. And since contaminated material is removed from site to landfill there is no issue of residual liability.
Developers are often, therefore, naturally reluctant to apply new or unproven techniques when treatment costs and timescales cannot be accurately defined and residual liabilities remain unquantified.
UK remediation practice enshrines the concept of 'fitness for purpose'. Land is only required to be remediated to the extent that it is sufficiently clean for the intended use of the site. This philosophy has been reaffirmed by the Government and looks set to form the basis of site remediation practice into the millennium, with the resultant implications for the application of ITTs.
Over the last 10 years or so there has been a rapid introduction of a raft of substantial environmental legislation. Much has not been tested in the courts to establish legal precedents. The practical result of this can be confusion and contradiction. Developers may be unwilling to apply new techniques because again the issue of residual liability is unclear. Where an ITT is considered suitable it may be impossible to obtain a Waste Management Licence for on-site treatment within the timescales of a development contract.
In the context of land reclamation, the principal regulators are the Environment Agency and (Local) Planning Authority. Perhaps because of the gaps in legislation and precedent, regulatory interpretation is often inconsistent and rarely takes full account of the commercial pressures a developer may be under. As UK land reclamation largely occurs via redevelopment, it is surely sensible for regulation to take account of the practical realities of developing a brownfield site. Timescale is a critical cost factor and a four-month delay in receiving a response to a licence application or an overly strict interpretation of legislation or current guidance will not encourage the application of ITTs. A developer will revert to tried and trusted methods where timescales can be predicted and costs determined up front.
By definition, ITTs are not established technologies, and many developers and funding institutions are cautious about relying upon techniques which are 'unproven' and which leave or treat contaminants in situ. In many cases such concerns are unfounded, as technologies such as bioremediation, soil vapour extraction and soil washing are now established both in the UK and overseas and have a proven, successful track record.
Received wisdom suggests that if you dig out contaminated soil from a site and dump it in a landfill, then there is no question of any residual liability either as a result of new legislation, legal precedent or a different interpretation of existing legislation.
Whilst this may be largely true, it does reflect the emphasis the industry has traditionally placed on soil contamination and the 'fitness for purpose' philosophy. UK guidance on the redevelopment of contaminated land has historically been limited. This situation has changed in the recent past with the publication of an array of DOE (now DETR) sponsored research reports including Contaminated Land Research (CLR) and specific industry profiles.
However, increasing emphasis on wider environmental issues has clouded the issue. Digging out contaminated soil may well render a site fit for the intended end use, but it may not address other issues which could affect future liability. For example, contaminated groundwater may be left in situ which, without treatment, could migrate and pollute a local aquifer. Such wider considerations, particularly in connection with groundwater pollution, may provide some much needed impetus for adoption of new clean-up techniques.
It is still relatively cheap to landfill in the UK, and comparative costs represent a significant barrier to the introduction of new clean-up techniques. The introduction of landfill tax affords a fiscal control and could provide an incentive to discourage landfilling contaminated soil. However, the current regime exempts much of the soil likely to arise on a contaminated site from the tax a measure designed to encourage re-use of contaminated land and release pressure on greenfield developments.
It seems unlikely, therefore, that current Government policy on taxation will swing the economic balance away from landfill towards treatment of contaminated soils.
An area where Landfill Tax has bitten is in the treatment of soil wastes which would not be exempted or which would be classed as inert and attract the lower rate of tax (currently £2/tonne). In these cases developers actively seek to retain material on site and therefore some forms of treatment to create a growing medium from inert substrate can provide an attractive and cost effective reclamation solution. Examples of this would include blending green waste, bio-gran or other organic waste products with inert soil or colliery spoil to produce an in situ growing medium. Whilst purists might argue that these techniques are not strictly Innovative Treatment Technologies, they nevertheless play an important role in land reclamation and as a category probably represent the largest volume of treated soil which is re-used rather than landfilled.
Most would agree that the current practice of hauling contaminated soil from a reclamation site is not a sustainable option. Hence, despite the barriers to introduction of Innovative Treatment Technologies it seems inevitable that their application in land reclamation will increase. Development of the technologies themselves has shown that, particularly for larger reclamation projects, cost comparisons with landfilling can be favourable.
Implementation of the proposed Landfill Directive may well alter the economic balance between treatment and landfilling by restricting the landfilling of certain wastes or imposing requirements on pre-treatment.
The new framework for contaminated land should remove some of the uncertainties from the current regime and will hopefully result in more consistent and pragmatic regulation. Risk assessment will allow informed judgements to be made about actual (rather than perceived or theoretical) threats from contamination. This should help to mitigate the 'let's dig it all out just to be sure' philosophy and encourage novel and innovative techniques to be applied.
Where ITTs do score is in larger reclamation projects such as the Greenwich Millennium site where the up-front costs of mobilisation and capital can be offset against a large treatment volume. Many ITTs are also ideal for gradual remediation of contamination where excavation is not practical and site disruption is required to be minimal.
Whilst the future for ITTs within the UK market may not yet be rosy, one can
at least detect a distinct pinkish tinge.