Land contamination: risk management

Site investigation

How to plan for a site investigation.

You may need to plan, design and carry out an appropriate intrusive site investigation.

You must record your findings in your site investigation report.

Intrusive site investigation

For a site investigation, you will collect and analyse soil, surface water, groundwater, soil gas and other media. To do this you will need to excavate trial pits, drill exploratory boreholes and construct groundwater monitoring wells.

Use the information you collect and the results to refine the conceptual model, the risk assessment, options appraisal and remediation stages.

You may do a site investigation in a single or a number of phased stages. It may be simple or detailed, depending on the complexity of your site.

The information you collect must be representative of all relevant aspects of the site. It must be:

  • from the right locations
  • at appropriate time periods

Your data collection procedures must meet quality management standards. When you present data, its origin and meaning must be transparent.

You must use the Environment Agency’s monitoring certification scheme (MCERTS).

Find detailed information in these information sources for site characterisation on the CL:AIRE Water and Land Library (WALL) - see:

You can find further detailed information in these British Standard Institute (BSI) publications:

You can use this guidance for the number of monitoring points required, duration of monitoring programme and information on gas risk assessment:

Consider practicability, cost, effectiveness and benefits

When you collect site information you will need to consider the practicability, cost, effectiveness and benefits.

Practicability factors include:

  • on-site or off-site access
  • timeframe and phasing requirements
  • regulatory, health and safety and other management requirements
  • identifying site services and making sure you can avoid them during intrusive investigation
  • weather conditions

When you consider the cost of site investigation you must take into account:

  • the total cost against available budget
  • whether you can justify it against the level of risk present
  • potential delays while information is collected
  • that better quality information could reduce costs
  • that poor quality information could increase costs

Doing a site investigation needs to be effective and of benefit. You need to consider if:

  • the information you collect will be useful and relevant
  • the extent of information will match the requirements for certainty in decision making
  • there are any advantages or disadvantages of using additional or alternative methods, such as non-intrusive geophysical surveys
  • there are any implications of making wrong decisions in the absence of information - for example, failure to establish particular areas of contamination

Check the quality of the site investigation information

The information you collect must be relevant, sufficient, reliable and transparent.


It must match the site’s parameters, particularly the:

  • contaminant type
  • characteristics of pathways and receptors
  • soil type


It’s important that:

  • the appropriate number of samples have been taken for measuring against the assessment criteria
  • groundwater flow direction and the number of groundwater samples needed to characterise the groundwater regime at the site have been considered
  • sample points have been located and spaced so they’re sufficient to define zones


It must reflect true or likely conditions. You must use MCERTS.


It’s important that:

  • the information you collect is unambiguous
  • any uncertainty is recorded and dealt with
  • the origin of the information is clear

Monitoring certification scheme (MCERTS)

MCERTS is the Environment Agency’s monitoring certification scheme. It provides a framework to meet our quality requirements.

You must use MCERTS. We will only accept laboratory data from methods that have been accredited to the MCERTS standard.

When you submit chemical test data on potentially contaminated soils and water to the Environment Agency you must:

  • ensure that chemical analysis results submitted conform to MCERTS requirements
  • check that the laboratory carrying out the analysis has MCERTS accreditation for all parameters requested
  • work with the laboratory to make sure there are complete audit trails of samples and that these are available

Contact us for advice if you cannot find a suitable laboratory.

To find out more about MCERTS see monitoring emissions to air, land and water (MCERTS).

For soil see the brief guide for procurers of analytical services: MCERTS: performance standard for laboratories undertaking chemical testing of soil.

This performance standard does not directly cover sampling. You must ensure that sampling procedures, preservation and transportation are appropriate.

You can find further detailed information in BS 10175: Investigation of potentially contaminated sites - code of practice

The regulatory decisions we make are based on the data you submit.

Using MCERTS will provide confidence that your results are acceptable and reliable.