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Our industrial legacy has caused many problems. Sites that are now being redeveloped for industry and housing hold many hidden dangers, and it is vital that a site investigation is completed (and possible remediation performed) before it can be reused. An environmental consultant should carry out a desk study to determine the probable extent of any contamination before conducting an intrusive investigation.
There are a number of factors that should be investigated, including:
• The former use(s) of the site • The type of chemicals and materials used on the site • How long the site was in use • How long ago the activity finished • Whether there are fuel or other underground storage tanks • Whether other materials are likely to be buried there • How deeply the contamination is likely to permeate • How far the buildings/activities extended on the site • Whether the contaminants moved with groundwater flow • The preparation of a Conceptual Site Model (CSM)
Legislation and guidance
Legislation and guidance change according to our UK government and EU directives, but the most seriously contaminated sites are covered by Part IIA of the Environmental Protection Act in the UK, dating back to the early 1990s. This allows a site to be determined as contaminated by a Local Authority, and if this happens, the site must be remediated. Unfortunately, if the original polluter/owner of the site is no longer in business, this may be termed an ‘orphan site’ and the cost of remediation is then carried by the local authority/taxpayer. The current government has allocated very little money for this and determinations for Part IIA sites are now rare.
Most sites will be reviewed under planning, and a Local Authority must be satisfied that an application meets the criteria set out in the National Policy Planning Framework (NPPF) published in 2013, where the critical requirement regarding contamination is that the site, after remediation, should not be capable of being determined (as contaminated) under Part IIA. The previous document, PPS 23, was far more prescriptive and was used very successfully for a number of years, but it was replaced with the much shorter NPPF as part of the government’s Red Tape Challenge.
The NPPF
The following paragraphs are taken from section 11 of the NPPF, which concerns conserving and enhancing the natural environment, and are relevant to land affected by contamination.
Enhance natural and local environment [109]
The planning system should:
• Prevent new and existing development from unacceptable risk from unacceptable levels of soil, air, water and noise pollution • Remediate and mitigate despoiled, degraded, derelict, contaminated and unstable land where appropriate
Risk prevention and responsibility [120]
To prevent unacceptable risks from pollution, policies and decisions should:
• Ensure new development is appropriate for location • Take into account sensitivity of the area and development and the effects of pollution on health, environment and amenity • Where a site is affected by contamination, secure safe development – this responsibility rests with the developer/ landowner
Suitability, standards and competence [121]
Policies and decisions should ensure:
• The site is suitable for new use • After remediation, as a minimum, the land is not capable of determination under Part IIA • Adequate site investigation information prepared by a competent person is presented
So this is all rather generic, and practical detail must be sought from other guidance documents such as CLR 11 – an Environment Agency publication: Model Procedures for the Management of Land Contamination (first published in 2004, last updated in 2014), which provides technical guidance, including how to investigate, assess, and manage the risks. It also includes references to the most common industries and the materials likely to be associated with them. Some site usages are very well documented, such as gasworks/coal carbonisation sites, but others may be more obscure and require more research.
The main standard used for site investigation is BS 10175:2011 Investigation of Potentially Contaminated Sites – Code of Practice, published in March 2011. This is a comprehensive document that will guide practitioners through the requirements and various stages of a site investigation.
The EU has attempted to implement a Soil Framework Directive for a number of years, but the various iterations of this were always blocked by one or two member states (the UK being one of them). The requirement for a directory of all potentially contaminated sites was seen as a problem and a possible hindrance to development. The Commission is currently discussing a revised Soil Strategy that will be more flexible and risk based, but it is at a very tentative stage.
Range of contaminants
Many of these are well documented and will always appear in a testing suite, but others should be determined based on the risk assessment of the site. Typical lists include:
• pH • Asbestos • Heavy metals – As, Cd, Hg, Cu, Cr, Ni, Pb, Zn, Se, B, V, Be • Anions – chloride, sulphate, phosphate, nitrate, nitrite • Petroleum hydrocarbons • Volatile organic compounds – BTEX, chlorinated solvents • Semi-volatile organic compounds – PAHs, pesticides, PCBs, organo-metals, phenolics • Cyanide, sulphide and ammoniacal nitrogen
The range of inorganic contaminants (metals etc) has not changed significantly, but the organic compounds are updated on a regular basis. The list of Priority Pollutant compounds consisted of 33 compounds for some years, but in 2013, a further 12 were added (driven primarily by the Water Framework Directive), plus an additional 10 specific pollutants.
These are in the process of being added to testing suites within the UK (initially the monitoring of River Basin Systems), but some are included in soil testing suites. There is also a Watch List, whereby other chemicals are being monitored in EU member states (e.g. endocrine disruptors), and if they are routinely detected, then these may also be added to the Priority Pollutant list.
Changes in methodology
Progress within the laboratory continues with improved instrumentation or a response to a change in legislative requirements.
One example is the increase in physiological based extraction tests, rather than more conventional (and aggressive) acid digestion techniques, particularly for metals. These are described as bioaccessibility tests, and give a measure of the likely uptake by the human body. For more detail on these tests, please reference my article in the November 2013 edition of AWE. Using these techniques can save large sums of money on remediation, as local authorities may not require such stringent clean up criteria if it can be proven that the contamination is unlikely to be absorbed by the human body.
The requirement for lower detection limits can be achieved through improved instrumentation; for example, the updated Skalar spectrophotometric systems for cyanide, phenol and total organic carbon can be up to a factor of 20 times better than existing instrumentation.
A recent technique starting to gain ground in laboratories is two dimensional gas chromatography/mass spectroscopy. This is particularly useful in the analysis of complex mixtures such as petroleum hydrocarbons or pesticides, where many similar compounds coelute and are difficult to identify and quantify due to the interference of overlaying peaks. This software splits the chromatogram into two directions, rather than the normal linear trace of time along the bottom axis, making it easier to define a peak (or compound) and then accurately quantify it.
Loss on ignition
Another example of change is Loss on Ignition (LoI). Although not a new test, as it has been used for many years as a rough indicator of the organic matter content of a waste or soil, it has recently become important in the waste industry and for contaminated soil if being removed off site as waste. Trommel fines are the fine residues separated from waste (including grit and screenings), and they are often used to provide a protective layer between a landfill cap and the main body of the waste (top fluff). They were usually assumed to be inert, but HMRC concluded this was not a valid assumption and some form of testing should be required. The repercussions are significant, as the difference between disposal of inert (£2.50 per tonne) and non-inert (£80 per tonne) will cause problems for many operators.
The debate over what exactly constitutes inert waste and what can be reused has intensified recently since a treasury statement in March 2014, listing Loss on Ignition as a proposed test to measure the biodegradable element in the Trommel fines. The test involves heating a dry sample of the fines in an oven at 440°C, recording the weight before and after and calculating the percentage loss. If this value is <10% of the original weight, then the material can be classified as inert for tax purposes only.
This test has generated much discussion, and as an interim measure HMRC agreed that from April 2015 the limit would be <15%, reducing to <10% in 2016.
It should be noted that waste producers still need to undertake further chemical testing to classify whether or not waste is hazardous, and which category of landfill it should be sent to.
Asbestos update
The issues surrounding asbestos in soil are now widely acknowledged, since the Environmental Industries Commission (EIC) set up an asbestos in soil subgroup back in 2010. Following this, and a number of conferences and workshops, CIRIA published a document in March 2014, titled Asbestos in Soil and Made Ground: a guide to understanding and managing the risks (C733). This comprehensive document gives a very good survey of the history and current situation, with details of asbestos regulations relating to air monitoring and demolition issues, but also highlighting many areas where there was a shortfall in knowledge or data.
Waste material containing > 0.1% asbestos is classified as hazardous waste, but human health risk from soils and associated materials is still based on the < 0.001% asbestos in soil value expressed as potentially producing > 0.1 fibres/ml (current control limit), in a small study performed by Addison et al working at the IOM in 1996. This figure has never been ratified by any regulator.
Still in progress is the Joint Industry Working Group (JIWG), with CL:AIRE running the secretariat, and a Project Steering Group (PSG) consisting of representatives from all sectors affected by this issue, including the EA, HSE and UKAS, and chaired by Steve Forster of IEG Technologies. The PSG are in the process of writing a Code of Practice (CoP) that will build on the CIRIA document and provide detailed guidance for practitioners, including:
• Background levels of asbestos in 400 soils • Information on fibre release rates from a wider range of soil types and asbestos concentrations • An algorithm helping to predict risk from any particular site • A recommended method for the identification and quantification of asbestos in soils
The method, which must cover both gravimetric analysis of Asbestos Containing Material (ACM) and free fibre counting, is being written by the Standing Committee of Analysts (SCA) and will be published as a Blue Book by the Environment Agency. This method is currently in use by some laboratories that are accredited, but it is imperative that users of laboratory data ensure their selected laboratory is following the full method, as some laboratories only provide gravimetric data.
Both the method and the Code of Practice are expected to be complete by the end of 2015.
A further method due to be available in October this year, is a modified version of the fibre release test. This is the only practical way of assessing the likely release rate of airborne free fibres from an asbestos containing soil. Until recently this has only been available as a very expensive and time consuming test, but will now become more affordable.
In Summary
The monitoring of contaminated soil continues to evolve as legislative requirements and technology change. These changes, however, do not negate the need for careful sampling, correct storage of samples, representative subsampling in the laboratory, or accredited fit-for-purpose analyses. Underlying all of these changes must be a robust quality system to ensure correct handling of all samples and full traceability of data. It is important that users of laboratories fully understand the nature of the testing, what is and isn’t possible, and that they supply good quality samples for the laboratory to test. A good laboratory should always help and advise their clients and spend time ensuring the tests selected are exactly what the client needs.
Published: 16th Sep 2015 in AWE International
