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Executive Summary

This guideline on Site Investigation and Analysis of Soils is the fifth document in the Contaminated Land Management Guidelines series produced by the Ministry for the Environment. It is aimed at contaminated land practitioners and regulatory authorities, but may also be of use to owners, potential owners or occupiers of sites where hazardous substances are present or suspected in the soil. The purpose of the document is to promote a nationally consistent approach to the investigation and assessment of contaminated land.

We cover the principles of how to plan and conduct investigations, and set out best practice that should be followed for sampling and analysing soils on sites where hazardous substances are present or suspected. We do not cover the collection of other media for site investigations, such as soil gas, groundwater, sediments or surface waters.

The guideline highlights four areas of an investigation:

  • the principles of site investigation
  • soil sampling
  • laboratory analysis
  • the basics of data interpretation.

Each of these areas has its own section, following the Introduction.

We also set out recommendations for:

  • the approach to site investigations
  • setting the objectives for the investigation
  • undertaking the preliminary site study and inspection
  • planning a detailed site investigation
  • practical issues to be considered before undertaking fieldwork
  • how to conduct an investigation - including the process of planning the soil-sampling strategy, sample collection and handling, and quality assurance requirements
  • the minimum number of samples to collect
  • selecting a laboratory
  • analytical methods to use
  • ways of ensuring the data produced are reliable
  • applying common statistical methods for data analysis
  • assessing the significance of results that are close to guideline values, dealing with outliers and data review steps.