Across Europe, the management of contaminated soils by landfilling is being replaced by recovery/reuse. This is due amongst other things to the Landfill Directive and its waste treatment and acceptance criteria (WAC; EU Council Decision 2003/33/EC), the limited number of hazardous landfills, and the taxing of landfilling.
Site owners and their consultants now pay more attention to the reduction in waste soil volumes and the classification of waste soils to minimise the quantity of waste (some of which may be hazardous), but not always to good effect. Misclassification of waste is still ongoing and methodologies to deal with soil classification are misunderstood. However, soil re-use can be well managed in countries with practical legislation such as the Flanders VLAREBO Decree, which allows re-use as building material. More recent waste guidance documents such as those issued by the UK EA (2004a) allow logical characterisation of soils and assessment for re-use. Nevertheless, the management of land contamination and its contaminated soils, either in the ground, or excavated as a stockpile, are made more difficult by the debate arising from the ‘Van de Walle’ case ECJ (C-1/03).
These aspects, the EU Thematic Strategy for Soil Protection and the new CEN series of European Standards for aggregates, may form a new framework for soil recovery - and may provide opportunities to use treated processed contaminated soil as secondary aggregate.
Contaminated soils - are they a waste?
Currently there is uncertainty regarding the handling of contaminated soils, both in the ground or excavated onto a site, in their transport as a waste, and also their ultimate home. The ECJ (European Court of Justice) in Luxembourg delivered an unexpectedly firm judgement on un-excavated contaminated soils - in the case of Van de Walle 1 and Texaco Belgium SA. It determined that hydrocarbons which are unintentionally spilled and cause soil and groundwater contamination are waste, and that the soil contaminated by hydrocarbons is also a waste even if it has not been excavated. Further, the Landfill Directive determines that putting excavated material back into the ground can be construed as waste disposal, and will be subject to a landfill licence.
This is particularly relevant to the process of treating contaminated soils by thermal/physical/biological processes on-site and re-internment. More specifically EA (2004a) guidance considers that any soil taken off site is a waste and subject to the requirements of the Waste Framework Directive (WFD).
Under present circumstances, commentary from regulator colleagues considers that the WFD would be applied as soon as one tried to do anything to excavated material if it is contaminated, such as treat it on the site, or put it back in another part of the site untreated, or move it off site for action elsewhere. Everything except excavation is probably regarded as a waste management operation in the terms of the WFD, and is subject to waste management control (a licence, or authorisation, or registration of an exempt activity). WRAP (2005) considers that once a substance or object has become waste, it will remain waste until it has been fully recovered and it no longer poses a potential threat to the environment or human health - i.e. under the terms of risk assessment the waste can no longer form a link to the receptor or pathway.
In association, the EA considers that, as a starting point, waste which is used as aggregate/construction material will only cease to be waste when it is incorporated into a structure such as a road or building, even if it has been through a recovery process such as screening or crushing.
The Thematic Strategy for Soil Protection [COM (2006) 232 final] is also having an impact on matters of land contamination and is often discussed by the Brownfield professionals through the pages of Brownfield Briefing 2 . Issue no. 76 reports that MEPs on 16 July 2007, recommended deletion of the existing “recitals” 22-34 which proposed a list of contaminating activities, a national inventory of contaminated sites, seller contamination reports, remediation action, national strategies, orphan site proposals, public awareness measures, public participation, harmonised risk assessment and data exchange.
Until recently, across Europe, it was cheaper, and regulations made it easier, to dispose of contaminated soils at landfill with limited assessment and paperwork. However, a combination of recent date specific criteria in the Landfill Directive - its pre-treatment requirements, its landfill tax, and its conservative waste acceptance criteria at the gate (WAC; EU Council Decision 2003/33/EC), have pushed the handling of soils into the arena of physical treatment on-site or treatment hub off-site.
Widespread treatment has triggered a new waste product, the recycled or secondary aggregate to be reused within the development; to be exported for re-use at a specific receiving site; or to be soil stabilised on-site by cement/bentonite mix. Alternatively, contaminated soils which cannot be realistically treated due to high contaminant loads and hazardous designation has pushed the sector in Ireland to deal with the issue in another way; in 2002, around 140,000 tonnes of contaminated soil (including hazardous soils) were exported (under EU TFS Regulation 259/93) from Ireland to Germany, Belgium, and the Netherlands, for recovery. The arising Irish aggregate has supplied Dutch roads with fill.
Overall, under the present circumstances of EU waste law, it is difficult to determine when treated soil material ceases to be a waste. Rulings by the European Court of Justice have provided some guidance on how the definition of waste should be interpreted and applied by Member States and have led to the conclusion that more things are waste and remain waste for longer (WRAP 2005).
However relief may soon be on the way; the European Commission wishes to revise the 1977 Waste Directive and, interestingly in the context of Van de Walle, specifies “unexcavated contaminated soil” is to be excluded from the revised Directive, allowing sites to handle contaminated soil hotspots at their own pace provided there is no environmental pollution occurring 3 . It is hoped that the revised Waste Directive will provide the clarity the construction industry is seeking.
Contaminated soils - their assessment
The handling of contaminated soils pre or post-treatment is not simple; their management requires a two-phased approach both (1) hazard-based and (2) risk-based; where the hazard assessment is founded in waste law, and the risk assessment is founded on the concepts of the precautionary principle, and the probability of receptor exposure, and the now well documented source - pathway - receptor philosophy.
The EA (2004) concisely confirms the distinction:
‘The investigation and remediation of land contamination is risk-based, whereas the assessment of contaminated soil as waste is hazard-based. This means that the assessment of contaminated soil to determine whether it is hazardous waste is dependant on the presence of “dangerous substances” exceeding particular thresholds, and is not dependant on site specific risk assessment factors such as the source or disposal point of the waste’... ’It is important to remember that hazardous waste classification is hazard not risk based. Therefore, it is necessary to consider the full range of contaminants likely to be present, and not only those that pose a risk to particular receptors e.g. human health or groundwater’.
This needs to be kept in mind when dealing with the construction industry where time and budget constraints, and the waste law, push the issue of soils handling directly into hazard assessment - but of a limited nature. The associated implementation of an environmental risk assessment to determine if environmental pollution is ongoing at the site to be cleaned, or at the receiving site needs consideration also. It is particularly important to determine that the receiving site and surrounds will not be put to disadvantage on receipt of pre or post treated contaminated soils.
Any construction project where soils require excavation and movement off-site, particularly if the tonnages are big, should invoke both types of assessment. In Ireland, this tends to occur in projects where the tonnages to be moved are in excess of 10,000T, and where the soils cannot be recycled within the development.
As with any waste classification process, the hazard assessment approach can be onerous with much soil analysis and eluate testing required under the terms of the EWC code and hazardous waste list (2000/532/EC) EU Commission Decision and the sister WAC tool (EU Council Decision 2003/33/EC). Various paper tools have been issued by regulatory agencies to help implement both procedures, and streamline the hazard assessment with common decision boxes.
The aggregate solution
The production of aggregates from recovered soil waste post treatment is now becoming more common and will assist in identifying the point at which the soil waste has been fully recovered - i.e. when it ceases to be a waste and becomes a product. Aggregate salvage has a strong basis, enabled by the CEN European Standards for aggregates, effective from 1 January 2004. Critically, for the construction sector, the CEN standards accept secondary/recycled materials on an equal basis with natural aggregates, hence facilitating a standardised recovery process throughout Europe.
The CEN series of European Standards for aggregates are:
- EN 12620 Aggregates for concrete
- EN 13043 Aggregates for bituminous mixtures and surface treatments for roads, airfields and other trafficked areas
- EN 13055 Lightweight aggregates
- EN 13139 Aggregates for mortar
- EN 13242 Aggregates for unbound and hydraulically bound materials for use in civil engineering work and road construction
- EN 13383 Armourstone
- EN 13450 Aggregates for railway ballast
The implementation of the new CEN standards has been rapid in the UK, and the UK WRAP Aggregates Programme has much useful guidance on the issues via the internet. WRAP (2005) provides guidance to facilitate the classification of inert waste as a usable aggregate based on the ISO protocols discussed above.
The Flemish region of Belgium has had a specific decree on soil remediation regulated by the ‘Flemish Regulation on Soil Remediation’ or VLAREBO, applicable since October 1996. To avoid irregular use of excavated soil, the VLAREBO was revised in 2004 to establish a protocol for the management of excavated soil where stockpiles are larger than 250 m 3 or, where the soil is expected to be contaminated, a technical report is required with soil analysis. Depending on the degree of contamination the VLAREBO allows soil reuse for building material. However, where the contamination exceeds specified levels, the soil must be treated in a soil remediation centre.
The way forward
With the proper implementation of hazard assessment on the excavated soils and the move towards classifying the waste as an aggregate, there is no reason why treated contaminated soils cannot be widely used as secondary aggregate if the outputs meet the new CEN standards.
Doak, M., 2005. The Future for Excavated Contaminated/Brownfield Site Materials: New Policy and Practice across the EU. Journal of Land Contamination & Reclamation. EPP Publications, London, UK.
Doak, M., 2004. Risk Assessment and its Communication in the EU (Ireland). Groundwater and Public Health: Making the Connection. Washington DC USA.
Doak, M., 2004. Contaminated Land and Risk Assessment: The Basics. Necessary Steps Prior to Remediation and Development. IAH Annual Conference Tullamore 2004 - Groundwater Challenges of the National Development Plan.
Doak, M, & Carty, G., 2003. The Remediation of Contaminated Land in Ireland. CIWEM Annual Lecture. Nov 2003.
Doak, M., Carty, G., & Lynott, D., 2003. The Remediation of Contaminated Land in the Republic of Ireland. Proceedings Sardinia 2003, 9th International Waste Management and Landfill Symposium. Cagliari, Italy.
Doak, M., 2003. Calculation of Weight of Waste Deposited at an Unauthorised Landfill. Guidance - Waste Management (Landfill Levy) Regulations 2002.
EA, 2004a. Framework for the Classification of Contaminated Soils as Hazardous Waste. Version 1, July 2004
EA, 2004b. Model Procedures for the Management of Land Contamination. CLR 11.
NICOLE, 2005. The Interaction between Soil and Waste Legislation in 10 European Union Countries. NICOLE Secretariat, TNO, Appeldoorn, the Netherlands.
NICOLE, 2007. Discussion Paper Concerning European Commission Contaminated Soils Communication “Thematic Strategy for Soil Protection” COM(2006)231 final; & Proposal for Directive of the European Parliament and of the Council establishing a framework for the protection of soil and amending Directive 2004/35/EC (“directive”). NICOLE Secretariat, TNO, Appeldoorn, the Netherlands.
WRAP 2005. [Waste & Resources Action Programme]. Quality protocol for the production of aggregates from inert waste, revised edition. ISBN 1-84405-217-6. September 2005.
Published: 10th Sep 2007 in AWE International