Understanding the Ground Contamination Assessment Process

Sep 23, 2021 — Geotechnical Engineering, Environmental

Ground contamination assessments are governed by the Ministry for the Environment’s Contaminated Land Management Guidelines and local authority requirements. The procedure follows a defined 5-stage process, with each stage determining whether the next stage is needed and if so, what the scope of it should be.

Not all sites require a contamination assessment, however, there are formal triggers that councils can use to require an assessment. Or we might recommend an assessment based on information we find during our research of the land’s current and historical use.

If a site requires a contamination assessment, it will go through these five stages:

  • Stage 1 - preliminary site investigation report (PSI)
  • Stage 2 - detailed site investigation report (DSI)
  • Stage 3 - site remedial action plan (RAP)
  • Stage 4 - site validation report (SVR)
  • Stage 5 - ongoing monitoring and management plan (MMP)

We are often contacted by clients who require a PSI or a DSI but it’s important to understand that each stage is part of a wider assessment process. However, not all assessed sites require all 5 stages, and many assessments don’t need to continue after the completion of the PSI or DSI.

Ultimately, a ground contamination assessment is intended to ensure any contamination risks to humans and the environment are appropriately identified, assessed, and managed throughout a project’s timeline.

What to expect from a Ground Contamination Assessment:

The unexpected discovery of contamination can lead to significant unplanned costs and delays for a project, leading to additional assessments, consent requirements and site management and disposal measures. A properly planned and coordinated contamination assessment will ensure:

  • The health and safety of site workers, site maintenance personnel, adjacent property owners, and end-users.
  • The proper management of any contaminated soil
  • Proper disposal of contaminants
  • Time and money are saved during construction by minimising surprises

The adoption of good contamination assessment practices in the industry helps mitigate site development risks, but does not eliminate those risks, which is why we always recommend an Accidental Discovery Protocol be incorporated in a site’s Construction Management Plan.

If your site requires geotechnical investigation, it is usually possible to combine the contamination assessment and the geotechnical assessment to provide an optimised and more cost-effective package of work than commissioning the two assessments separately.

Get in touch to discuss your site’s specific development proposal so we can help you optimise the assessment work required.