1 Scope
This British Standard gives recommendations for, and guidance on, the investigation of land potentially affected by contamination and land with naturally elevated concentrations of potentially harmful substances, to determine or manage any risks. In order to obtain scientifically robust data on soil, groundwater, surface water and ground gas contamination it covers:
setting the objectives of an investigation;
developing a strategy for the investigation;
designing the different phases of the investigation;
sampling and field testing;
laboratory analysis; and
reporting.
Emphasis is placed on the importance of developing a conceptual site model (CSM) early in the investigation process and to review and update this as work progresses.
The relevant recommendations and guidance within this standard are intended to ensure that the objectives of an investigation are achieved and that appropriate data for risk assessment are obtained. However, it is not feasible to provide detailed guidance for every possible investigation scenario.
NOTE 1 For simplicity of expression, unless qualified in some way (e.g. ecological risk assessment), “risk assessment” in this document embraces all identifiable risks to identified receptors relevant to the task in hand, i.e. the context of its use.
This British Standard does not give:
guidance on certain constraints or problems that can affect a site, such as geotechnical aspects (which are covered by BS 5930:2015+A1:2020);
-
detailed guidance for the investigation and assessment of radioactively contaminated sites (see Note 2);
-
procedures for the formal assessment of the potential risks posed by land potentially affected by contamination (see Note 3);
NOTE 3 See the guidance published for England by Defra and the Environment Agency in LCRM [1] and by the respective ministries and environment agencies for the other UK jurisdictions.
-
guidance on sampling from stockpiles (see Note 3); and
NOTE 4 Guidance on sampling stockpiles is given in BS ISO 18400‑102 and BS ISO 18400‑104.
-
detailed guidance on investigations for ground gases, i.e. VOCs and permanent gases such as methane and carbon dioxide (these are dealt with in BS 8576).
NOTE 5 Guidance on the investigation of natural, near-natural and cultivated sites, for example, for contamination or to determine factors relevant to assessment of potential productivity, is provided in BS ISO 18400‑205.
NOTE 6 Further guidance on assessment of soil quality in relation to particular purposes can also be found in BS EN ISO 11504, BS EN ISO 15175, BS ISO 15176, BS EN ISO 15799, BS ISO 15800 and BS EN ISO 19258. Guidance is also available on the assessment of soil quality in relation to climate change, e.g. BS ISO 23400.
7 Scope and application of investigations
7.1 Preliminary investigation (desk study and site reconnaissance)
The first phase in the overall investigation process should always be a preliminary investigation in accordance with the guidance in Clause 8, and as appropriate, in BS ISO 18400‑202.
The purpose of the preliminary investigation is to obtain a suitable understanding of the site history, setting and potential to be affected by contamination, and fully inform and support preliminary risk assessment (8.3.2) and development of strategies for further exploratory and/or detailed investigations.
The preliminary investigation should include reference to historical records (8.2.1) and other sources of information (8.2.1), consultation with relevant sources (8.2.1.3) and a site reconnaissance (8.2.2).
The objectives might not require all the elements recommended in 8.1, in which case the strategy should identify what elements of the preliminary investigation are essential and those that do not need to be addressed.
Where elements of a preliminary investigation described in 8.1 are not to be included, these should be documented in the report, and any limitations on the final assessment arising from their omission should be made known to all parties involved and stated in the report.
The strategy should provide for a review of the information obtained at the conclusion of the preliminary investigation to determine if the objectives have been achieved (and are still appropriate) and whether there is a need to carry out an exploratory investigation and/or detailed investigation (7.2 and 7.3).
It should be decided whether the site should be divided into zones (see 6.4) if this has not already been done. Separate CSMs should be developed for each zone that is identified.
The output from the preliminary investigation should include the initial CSM (3.1.5) and a preliminary risk assessment (8.3.2) based on the information available.
NOTE 1 Preparation of a preliminary risk assessment requires interpretation of the information gathered during the preliminary investigation. Although a preliminary risk assessment will usually be an essential prerequisite for the design of further phases of investigation, guidance on how to do this is outside of the scope of this standard, so reference needs to be made to LCRM [1] and guidance, if any, in the individual UK jurisdictions.
NOTE 2 It is likely that there will be different requirements for further investigation of each zone.
NOTE 3 For sites where it is anticipated ground gases might be present and requires an investigation, additional guidance on preliminary investigations is provided in BS 8576.
NOTE 4 Further guidance on preliminary investigations is provided in BS ISO 18400‑202 which provides guidance on the design and execution of preliminary investigations comprising desk studies and site reconnaissance, and where appropriate, preliminary risk assessment. It is applicable whenever sampling exercises or investigations are to be carried out to determine soil quality. For example, specific guidance is provided about the possible contamination of cultivated sites and wooded sites. Annex A tabulates possible contamination/industry linkages.
NOTE 5 BS 5930:2015+A1:2020, Clause 10 to Clause 14 provide comprehensive guidance for desk studies and field reconnaissance (the equivalent of the preliminary investigation here) for geotechnical ground investigations. BS 5930:2015+A1:2020, Annex B gives general guidance for desk studies and BS 5930:2015+A1:2020, Annex C provides information about sources of information.
7.2 Exploratory investigation
An exploratory investigation is a limited investigation and should be designed to:
reduce uncertainty in knowledge of the site, including determining the accuracy or otherwise of contamination-related and other hypotheses developed in the preliminary investigation, thereby enabling the initial CSM to be refined; and
provide information that helps the design of any subsequent detailed investigation.
NOTE 1 Depending on the objectives of the investigation, and such other considerations as site access, land ownership and project programme, a decision might be taken to not carry out an exploratory investigation, but to proceed directly with a detailed investigation (7.3).
Where an exploratory investigation is undertaken, it should comprise non-intrusive and/or intrusive elements as appropriate. The intrusive element should include as appropriate collection and analysis of soil (9.7.2 and 10.3.3), surface water (9.7.3 and 10.3.7), groundwater (9.7.3 and 10.3.7) and ground gas (10.3.8) samples, monitoring of ground gas including VOCs (9.7.4 and 10.3.8) and certain groundwater parameters and groundwater levels, and application of on-site methods of soil and groundwater analysis when appropriate (see 10.4 and Annex E).
NOTE 2 A non-intrusive investigation technique (see 9.6.2, 10.2.2 and Table 4) can be used, for example, as an aid to locating below-ground structures or other features of the site.
Whether to apply a particular non-intrusive technique before or after some or all intrusive works have been carried out should be decided, justified and recorded, with the input of any necessary expert advice as appropriate.
Where the CSM output from the preliminary investigation identifies the likelihood of localized sources of contamination, and there is inadequate information to confirm the direction of groundwater flow, an appropriate strategy should be developed to investigate contamination at the suspect locations, the water table at several (triangulated) positions and groundwater quality. In this situation, the use of targeted sampling locations is likely to be most appropriate (see 9.7.2.2).
The information obtained from the exploratory investigation should be used to refine the CSM and in the design of any subsequent investigation(s).
NOTE 3 An exploratory investigation is not intended to provide sufficient data to permit a site-wide detailed quantitative risk assessment (DQRA). It might, however, provide sufficient data for a DQRA on a particular part or zone of the site or on a specific element if the investigation is specifically designed with this intent in mind. It might also be sufficient (depending on the objectives and uncertainty reduction required) to fulfil a regulatory requirement.
NOTE 4 The exploratory investigation could indicate that the contamination pattern is more complex or the concentrations and/or the extent of contamination are greater than anticipated. In such situations it is likely that further investigatory work will be necessary in order to refine the CSM and provide adequate robust information for the risk assessment.
7.3 Detailed investigation
COMMENTARY ON 7.3
The amount and nature of the information required from the detailed investigation will vary according to the nature of the site and the possible requirements for remedial action. The implications of the decisions on what actions need to be implemented will vary from site to site. The amount and quality of information available will dictate the degree of confidence that can be attributed to the decision-making process.
When an exploratory investigation has not been carried out, detailed investigation could be necessary to test contamination-related and other hypotheses as would be done during an exploratory investigation.
The scope of a detailed investigation will depend on the objectives of the investigation but should comprise, as far as is practical, collection of:
all information necessary to test the accuracy or otherwise of contamination-related and other hypotheses developed in earlier phases of the overall investigation;
all information necessary for the assessment of risks to all potential receptors; and
information relevant to the selection, design and costing of remedial works.
Any required permits and/or licences should be in place prior to starting the investigation (see Annex I).
The investigation should include the use of non-intrusive investigation methods, as well as intrusive methods, as necessary. Expert advice should be obtained as to whether it is best to apply a particular non-intrusive technique before or after some or all of any intrusive works have been carried out.
The investigation should include, as appropriate, collection and analysis/testing of soil (9.7.2 and 10.3.3), surface water (9.7.3 and 10.3.7), groundwater (9.7.3 and 10.3.7) and ground gas including VOCs (9.7.4 and 10.3.8) samples, and the in-situ monitoring of ground gas, certain groundwater parameters and groundwater levels.
The design of the investigation should take into account all the information and hypotheses developed in the earlier phases of investigation and the objectives for this phase of the work.
Particular attention should be paid to the sufficiency and quality of the data, taking full account of the historical and current use(s), likely heterogeneity and underlying stratigraphy.
In a detailed investigation, the greater proportion of sampling locations should be non- targeted to aid the reliability of interpretation (see 9.7.2.3) and the use of statistical methods for assessment of the data. However, targeted sampling should also be employed as necessary, for example, to delineate or confirm an area of contamination detected during an exploratory investigation.
The relative density of sampling in each zone should take into account the findings of earlier phases of investigation, including the uncertainty associated with each zone.
During the subsequent review of the CSM and assessment of risks and hazards, all possible migration pathways relevant to the contamination should be taken into account, and an appreciation in space and time of the contamination established. The possible migration pathways should inform the design of the detailed investigation, since detailed knowledge of physical and chemical soil properties, and the local hydrology including the hydrogeological regime, is essential for reaching defensible conclusions.
The risk assessment should also take into account the risks of making incorrect decisions based on the amount and quality of information available.
All parties involved in the decision-making process should be fully informed as information is produced, to confirm that the information is sufficient for the purpose intended.
7.4 Supplementary investigations
A review of the outcome of the detailed investigation should be carried out in order to identify aspects and areas where an unacceptable level of uncertainty or deficiency of information remains. Where such uncertainties or deficiencies are identified, a supplementary investigation should be carried out. This should be designed to produce specific information. It should use targeted and/or non-targeted sampling as appropriate.
NOTE 1 A supplementary investigation could be required, for example:
to provide additional information to design and cost remedial works, for example, to delineate volumes of soil requiring remediation, or to carry out specific tests to evaluate the suitability of specific remedial treatment techniques;
to provide additional information on the groundwater regime;
to provide chemical testing information for the classification of wastes;
to monitor groundwater quality and levels, and/or ground gas conditions, after completion of the detailed investigation to determine any changes in site conditions and to provide additional data to assess risks and aid design of protective measures; and
to monitor groundwater and ground gas conditions during and after construction or remediation to determine whether there have been any adverse changes in site conditions.
NOTE 2 Specific information on standard rules and bespoke permits for using, treating and storing waste can be found here: https://www.gov.uk/guidance/waste-environmental-permits
7.5 Specific strategies for field investigations
When a field investigation (exploratory, detailed or supplementary) is to be carried out, decisions should be made and recorded (e.g. in an investigation and/or sampling plan (see 6.5, Note 4) regarding:
the objectives of the investigation;
the form of the investigation [non-intrusive and/or intrusive (see 9.6, 10.2 and Table 4 and Table 5)] necessary to obtain appropriate, suitably robust and defensible data in accordance with the objectives;
the purposes for which samples are required (e.g. for chemical analysis or other tests);
the locations from which samples are to be collected and the number of locations required (see sampling strategy in 9.7);
the number and type of samples to be collected (i.e. soil, water, gas) from each location, the depths at which they are to be collected (see 9.7.3), whether replicate samples are to be taken [for example, to allow assessment and reporting of sampling uncertainty (see Annex D)], and any monitoring requirements (see sampling strategy in 9.7);
the techniques to be used to collect the samples (see Figure 2, Table 5, BS ISO 18400‑102:2017, Table 3 and BS ISO 18400‑102:2017, Table 4, and 10.3), taking into account: the soil types, groundwater conditions, topography, services and access (e.g. soft landscape, tarmac, presence of buildings, etc), the quality of reinstatement necessary, the depths at which samples are to be collected (9.7.3), whether a ground gas investigation is included (9.7.4), whether water samples are to be collected (9.7.5), and the monitoring installations required (9.7.3 and 9.7.4) (see Note 1);
how samples are to be taken to avoid or minimize cross-contamination (10.2.3.3);
what provisions are to be made for cleaning field equipment between sampling points (10.2.3.3);
quality assurance procedures to provide an auditable process to enable confirmation that sampling has been carried out in a satisfactory manner (9.9);
the analyses and tests to be carried out on each sample, and whether these are to be carried out in a laboratory or in the field (see 9.7, 10.4, 11.4 and 11.6), and the analytical and testing strategy (see Note 3);
selection of a laboratory which can employ analytical and other test methods appropriate for the planned risk assessment process to the required standard and accommodate the anticipated workload (see Clause 11);
how samples are to be handled, stored, preserved and transported to the laboratory so as to minimize alteration prior to analysis or testing (10.6);
the process for dispatch of samples to the laboratory, issue of instructions to the laboratory and the date by which the results are required; and
requirements for field testing (e.g. methods and instrumentation) (10.4).
Decisions should also be made about the programme for the fieldworks and the logistics of the site investigation, including the availability of relevant machinery and personnel, permission for site access, liaison with regulatory authorities, completion of health and safety and environmental risk assessments.
NOTE 1 Attention is drawn to the Construction Design and Management Regulations [6].
NOTE 2 The selection of the sampling technique might involve some compromise, for example, due to access, headroom, underground services or other constraint. If samples are only required from 2 m to 3 m below ground level (bgl) and the location of buried services is known with sufficient certainty, trial pits might be regarded as the most appropriate technique. However, where there is over-site concrete which is still in use and a good standard of reinstatement is necessary in order, for example, to minimize disruption of the site and allow satisfactory reinstatement, coring through the concrete followed, for example, by use of a dynamic sampling tool could be the more appropriate approach (see Table 5 in this standard; BS ISO 18400‑102:2017, Table 3; and BS ISO 18400‑102:2017, Table 4).
NOTE 3 Whilst decisions about the type of analyses and testing can usually be made during formulation of the investigation strategy, final decisions about what samples to analyse or test are often deferred until the samples have been obtained. This permits field observations including the results from on-site methods of analysis/testing to be taken into account.
NOTE 2 Guidance on the investigation and assessment of radioactivity in soils is given in BS EN ISO 18589‑1 and BS EN ISO 18589‑2.