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Site Investigation

What is a contaminated site?

Who does what?

Why is it important?

What is risk management?

Risk assessment fundamentals

Risk assessment methods

Limitations of risk assessment

What are RA tiers?


Problem Identification

Site Characterisation

Site Investigation

Receptor Characterisation

Exposure Assessment

Toxicity Assessment

Risk Characterisation

RM Decisions





Site Investigation

The gathering of information through a site investigation is a fundamental task of a RA. It may be performed for all or any stages of the RA (e.g. Receptor Characterisation, Toxicity Assessment, or Exposure Assessment) or for any tier of the RA.

Careful planning is required to ensure that the results obtained from a site investigation will be valid and defensible.  A site investigation may involve:

  • sampling of media such as soil, water or air
  • sampling of receptor tissue or body fluids
  • biological surveys of receptor characteristics
  • behavioural analyses, or
  • habitat surveys.

At tier 2 or 3 it may involve:

  • undertaking direct toxicity assessments of key receptors;
  • sampling of receptor tissue or body fluids; or
  • undertaking behavioural assessments of key species .

Planning for Site Investigations:

What will be the level of effort applied to this level of RA site investigations? What are the logistical boundaries and constraints to this investigation?

It is prudent to take account of the practical considerations of the site investigation to ensure that all parties are informed of the boundaries of the exercise. Whether the constraints are related to financial, time or resource issues, they should be factored into the design and methodology early in the process. It may also be apparent due to the characteristics of the site (e.g. size, likelihood of contamination, priority, etc.) that the level of effort assigned to the site investigation should be greater or lesser relative to the effort assigned to other sites.

What are the spatial and temporal boundaries for this Tier of RA?

You will need to determine the appropriate time scale and spatial scale over which this investigation will be carried out. While a Tier 1 investigation may only require a one-off sampling of various media.

What design, methods and data quality will be used?

New Zealand guidance documents provide good information on the design and implementation of site investigations.  Some more general information on site investigation  design is also provided in Australian Standard AS4482.1 1997 Guide to the sampling and investigation of potentially contaminated soil Part 1: Non-volatile and semi-volatile compounds. 

What further information is required about the site conditions?

Some site information (e.g. site history) has probably already been collected during the Initiation stage. This information now needs to be systematically re-evaluated and confirmed. The use of a site checklist often helps to identify key features at an early stage in the investigation process.

This checklist , which is based on the Alaskan document, may provide useful guidance on obtaining information at this stage

Which analyses will be required?

If you are unsure which specific analyses will be required, discuss your objectives with a consultant or the laboratory manager to whom you intend to send your samples. Your advisor will need to know what kinds of chemicals you are interested in (e.g. timber treatment chemicals) and what media will be sampled (e.g. soil, water, vegetation). He/she will be able to advise you of the appropriate sampling procedure and sample storage/transport requirements for the analysis.

Which media (e.g. soil, water, etc.) will be sampled?

This will be determined by conditions at the site and the contaminants of concern. Samples of soil are usual especially in the initial stages of an ERA. They may be sampled from the ground surface, from varying depths below the surface, from test pits or boreholes, or from underneath concrete or asphalt. Groundwater and surface water samples may be taken if a bore or water body is present on or near the site. Water from effluents, runoff, stormwater pipes, puddles and other sources may also be sampled. Dusts or other media such as vapour may be sampled or measured as appropriate for the contaminant of concern.

How many samples will be taken?

Refer to the Australian Standard AS4482.1 – 1997. You will need to decide whether you will take a number of individual samples or whether composite samples would be more appropriate for each level of the ERA.

Where will the samples be taken from?

To an extent this will depend on practical considerations. However, sample locations may be chosen based on:

  • a grid pattern across the site
  • locating samples around likely areas of contamination
  • locating samples around sensitive receptors
  • locating samples to better define the extent of contamination indicated in previous levels of ERA investigations
  • locating samples to fill information gaps indicated in previous Levels of ERA investigations.
What documentation will be required?

Chain of custody documentation is the standard requirement for transporting samples to the laboratory, even if you are delivering them yourself. Refer to Appendix H of AS4482.1 - 1997. The following are some additional recommended documentation requirements:

  • Health & Safety Plan
  • Site sampling plan
  • Sample labels with a unique identifier for each sample
  • Sample location and site photographs
  • Site entry authorisation (for the primary site, neighbouring properties, etc.)
  • If you intend to drill a borehole, a resource consent and borehole logs may be required
An example of how a site investigation plan might work is shown here.

Health & Safety 

Protection of the health and safety of site investigators is paramount. Due to the nature of the work, a site investigator could be exposed to contaminants on site at much higher levels than those of site residents or workers.

Health and safety procedures must be put in place to minimise the exposure of hazards for people (including staff, clients, service people, contractors, consultants and the general public) in all places of work.

The types of hazards that can be encountered include chemical, noise, electrical, temperature, biological and physical. Physical hazards include instability from subsidence, settlement, erosion, and around excavations, sharps, and the presence of site services such as live electricity cables and gas mains.

A primary requirement of the Health and Safety in Employment Act (1992) is to identify potential hazards, and identify the procedures that must be followed to eliminate, isolate or minimise those hazards. These procedures should be set out in a health and safety plan.



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Page last updated: 01 May 2007

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