17.8 Integrated investigations

COMMENTARY ON 17.8

The main source of guidance on investigation of potentially contaminated sites is BS 10175. However, it is common practice to run both geotechnical and contaminated land investigations together in an integrated investigation. Integrated investigations may also include investigations for ground gas or archaeological or other types of investigation.

Integration of ground investigations can often result in lower costs and greater efficiency when compared to undertaking separate field investigations owing to the following factors:

• a) simplified project management;
• b) common use of equipment and procedures;
• c) exploratory holes can be used for more than one purpose;
• d) joint health and safety procedures established and implemented;
• e) joint environmental and/or archeological protection procedures established and implemented;
• f) integrated consideration of resultant data; and
• g) reduced project duration.

However, depending on the circumstances, site management operations might be more complicated, the sharing of resources could result in delays if not properly managed and increased activity on site might present safety issues.

The degree of integration should be based upon the findings of the desk study and preliminary investigation. Integrated field investigations should be designed so that the requirements of each part of the investigation do not compromise any other part. For example, sampling locations for contamination should not be moved from a selected grid pattern (see BS 10175:2011+A1:2013, 7.7.2) in order to accommodate geotechnical requirements, which might necessitate additional investigation points.

NOTE 1 Further information on integrated investigations is provided in Annex G.

Samples that might be contaminated or contain chemical or physical hazards should be identified on site; this is informed by the desk study and the findings on site.

NOTE 2 Identification of hazards on site is the preferred approach so that appropriate geotechnical test samples are sent to the geotechnical laboratory. However, the alternative is that the geotechnical laboratory manager is made fully aware of the situation before the laboratory consents to receive the samples and as part of the project contract prior to hazardous material testing.

The assessment of the hazard should be carried out by a laboratory specializing in the type of testing which is appropriate to the nature of the likely hazard. The findings should be used by the geotechnical laboratory supervisor to identify those samples that are not suitable to be tested in the geotechnical laboratory or that require further health and safety assessment over and above the standard risk assessment.

Designers should also take into account the extent to which laboratory tests can impact on the health of those conduting the testing and should look for alternatives where significant hazards are foreseeable.

17.9 Contaminated ground

The possibility of contaminated ground being present should be taken into account for all ground investigations to ensure the safety and protection of site staff, the public and the environment including water courses and groundwater. Investigations for contamination should be carried out in accordance with BS 10175.

NOTE 1 Guidance on safe working on contaminated sites can be found in BS 10381-3 and CIRIA R132 [1]. Where asbestos might occur, more specific advice is given in the AGS guidance [4].

Ground investigations for geotechnical purposes should only be undertaken following evaluation of whether, in the absence of information on contamination or ground gas, the potential risks to human health and safety or the environment are acceptable.

Geotechnical investigations that have not been designed primarily to investigate contaminated ground might provide an opportunity to obtain information on contamination, either incidentally, or as part of an integrated investigation (see 17.8); however, incidental sampling should never be regarded as a substitute for a proper investigation for contamination.

Samples that might be contaminated should be tested in a laboratory specializing in the type of testing appropriate to the nature of the likely hazard to identify if they are suitable for geotechnical laboratory testing.

NOTE 2 Contamination, if present, can have implications for undertaking geotechnical laboratory testing. These implications might range from the adoption of appropriate precautions to ensure the safety of the laboratory staff to a decision about whether the particular test scheduled is viable at all (see Clark and Keeton, 1995 [15]).

A protocol for screening to identify any contamination should be established. While the detailed procedures might vary on a project specific basis, the overriding principle should be that the geotechnical advisor has the responsibility for the information flow.

Any changes to the geotechnical laboratory testing regime should be discussed with the geotechnical advisor.

When establishing the extent of the ground investigation for developments on ground that has been contaminated by former use, the design of remedial ground treatment and the geotechnical design of foundations and services should be taken into account. The type, spacing and depth of investigation points should be determined by the objectives of the investigation, as well as the geological conditions, the nature and extent of the contamination, and the proposed end use.

NOTE 3 With these types of investigation there are likely to be further special requirements regarding sampling, sample containers, sample transport, sample storage and time elapsed between sampling and testing (see BS 10175).

NOTE 4 BS 10175 provides 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.

17.10 Ground gas

The possibility of ground gas being present should be taken into account and the likelihood of ground gas affecting the ground investigation should be identified as a part of the desk study and field reconnaissance. If the site is likely to be affected by ground gas, an assessment of the hazard should be carried out in accordance with BS 8576.

NOTE 1 For information on carbon monoxide, see the HSE publication Position statement, carbon monoxide [16]; the CIRIA publication The VOCs handbook [17] for information on volatile organic compounds (VOCs) and Wilson, Card and Haines, 2008 [18] for information on ground gas in general.

NOTE 2 Low oxygen content air might occur in deep excavations and during tunnelling operations with or without raised carbon dioxide levels and/or methane concentrations.

NOTE 3 For information on radon, see BS 8576:2013, Annex B. The Building Research Establishment has published guidance on the protection of buildings against radon.⁹⁾