Contaminated Land Site Investigation: Code of Practice Updated


BS10175, the code of practice for the investigation of potentially contaminated sites, was substantially revised in March 2011. Most commentators regard the revised British Standard as a significant improvement on the earlier 2001 version. The standard is a code of practice, rather than a legally binding standard. Nevertheless, non-adherence to the standard can still have legal implications, and any practitioner seeking to lay aside the provisions of the standard should be prepared to justify their actions in court if necessary.

Changes to the definition of contamination

In the revised British standard, contamination is defined as, ?Presence of a substance or agent, as a result of human activity, in, on, or under land, which has the potential to cause harm or pollution.? The phrase ?as a result of human activity? is new, and makes it clear that substances that occur naturally at a locality are not to be classed as contamination. A crucial point is that actual harm or pollution does not have to occur, it merely suffices that the potential is there.

Changes to the preliminary investigation

Good practice in site investigation requires a desktop study site investigation to be conducted before any on site activities, such as soil sampling. This should include a preliminary risk assessment, taking into account the site?s history, geology, hydrology, ecology and archaeology. The presence of harmful invasive plant species, such as Japanese knotweed, should also be noted, as should the presence of protected species, such as bats or great crested newts. In the revised British Standard various extra considerations are added to those detailed in the previous version. These include considering any foreseeable changes to the site, such as potential flooding, changes in groundwater levels, or changes of use to nearby sites. The updated standard states that the possibility of unexploded ordnance (UXO) should now to be considered. The history of a site is a crucial factor in deciding which contaminants may be present, and the history of the surrounding properties should also be examined.

The preliminary risk assessment should also include an initial site reconnaissance, carried out by a suitably qualified person. The revised guidelines state that there is a duty to promptly report anything that poses an immediate threat to human health and safety, or the environment, to whoever is in charge of the site. By the end of the preliminary investigation there should be an awareness of which contaminants are likely to occur on the site, so that analysis can be directed towards these.

The standard mentions the use of map and aerial view sites from the internet. It states that they can be useful, but points out that they are often undated, and that much may have happened on the site in the time since the initial photographs were taken. They are no substitute for a detailed site reconnaissance.

The standard emphasizes the importance of constructing a conceptual model of a site, the uncertainties in which are to be removed by investigation and sample analysis.

Changes to the main site investigation and sample analysis

Following the preliminary risk assessment, field investigations and sampling should be planned and carried out. The new guidelines contain updated methods for both intrusive and non-intrusive sampling techniques. It is stated that analytical methods should be appropriately validated, and that MCERTS accreditation should be in place where possible. MCERTS is the monitoring certification programme of the Environment Agency. Details of sampling and analysis are given in various appendices (referred to as annexes, see below).

BS10175 should be used in conjunction with ISO10381, the standard concerned with soil sampling. Development of a scientifically robust sampling regime is vital, since incorrect sampling techniques can lead to erroneous conclusions. The ISO5667 standard deals with the sampling of groundwater. Appropriate statistical methods should be employed to ensure that representative samples are taken. The updated standard addresses the issues of both analytical uncertainty and sub-sampling uncertainty. ISO11464 and ISO14507, which are concerned with the treatment of soil samples prior to analysis, are also relevant, and are referred to in BS10175. ISO11464 is concerned with treatment preceding the determination of inorganic components or a soil?s physico-chemical characteristics, whereas ISO14507 is concerned with treatment prior to the analysis of organic contaminants.

Changes to reporting requirements for contaminated sites

The updated BS10175 contains various changes to reporting requirements. The need for clarity of presentation is emphasized. It is stated that all correspondence with regulatory authorities should be attached to the main report, which should also contain all relevant regulatory requirements. Reports should always contain factual observations on the specific results, such as a comparison with regulatory limits or a particular assessment criterion.

Changes to the technical appendices for BS10175

There are substantial changes to the technical appendices for BS10175. Four new appendices (referred to as ?annexes?) are introduced. Annexe D details the assessment and control of the uncertainty of sampling. Annexe F is concerned with methods for rapid field measurement. It gives a useful overview, covering soil, water and vapour analysis. Annexe G focuses on laboratory analysis; it reflects current good practice, providing advice on quality assurance and modern methods. Annexe I deals with land contamination regulation. It gives a useful outline of the different regulatory requirements, concerning both England and the devolved administrations.

Overall effect of the changes

The revised version of BS10175 is clearer than the previous version. It aligns itself well with current ISO standards, giving a consistent ?bundle? of instructions for dealing with site investigations of contaminated land.

However, the importance of choosing competent practitioners for site investigations remains. Writing on the AGS (Association of geotechnical and geoenvironmental specialists) website, Ann-Marie Casserly states that reports are still being produced that would have been regarded as poor three decades ago, their authors obviously not being aware of current regulations. She also comments that poor sampling, without regard to statistical methods, is still carried out by some geotechnical specialists. It is vital that those commissioning contaminated site reports ensure that they choose competent professionals.?

Useful Links

Owen, R., SOCI website, ?BS10175: 2011, Investigation of potentially contaminated sites ? Code of practice. What has significantly changed - Part 2?.

BSI shop, BS10175: 2011.

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