Contaminated land

Contaminated sites

Contaminated sites pose a threat to both the environment and our health. They also limit land use and reduce land values. It is important that a contaminated site is investigated and managed to reduce this risk.

The ARC has the responsibility, under section 15 and section 30 of the Resource Management Act 1991 (RMA) to:

• investigate land for the purpose of identifying and monitoring contaminated sites
• control discharges to the environment, such as discharges from a contaminated site to soil, air, groundwater or surface water.

The RMA defines the term 'discharge' as 'to emit, deposit and allow to escape. This includes the ongoing discharges that may be emitted from contaminated soil and or groundwater.

Paint pollution in stream

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What is a contaminated site?

A site is contaminated when hazardous substances are present in the soil and/or groundwater above background levels (at concentrations higher than would naturally occur).

What are background levels?

A background level is the level of a substance that occurs naturally within the environment.

How can a site become contaminated?

There are a number of activities that may cause contamination on a site, including:

• use of agricultural chemicals
• disposal of wastes, controlled and uncontrolled
• accidental spillage or leakage of chemicals
• storage or transportation of raw materials, finished products or wastes
• migration of contaminants into a site from neighbouring land.

For a comprehensive list of activities that carry a contamination risk take this link to the Hazardous Activities and Industries List (HAIL), compiled by the Ministry for the Environment (MfE).

How do I assess if my site is contaminated?

Contaminants such as diesel and household refuse are easy to identify (they discolour the soil or are odorous), but many contaminants cannot be seen or smelt (like arsenic, lead, DDT), so it's important the site history is known before starting works.

We require that any site that has the potential to be contaminated, either from past or present land use, be investigated. This should be carried out by an experienced environmental consultants, with all sampling of soil and groundwater undertaken before earth working or development begins.

The type of information and level of investigation required is site-specific, so you should refer to the MfE's guidelines or talk to our team direct.

The following fact sheet 'Is this a contaminated site?' provides information for land owners, developers, earthworking crews, contractors and consultants about contaminated sites, including the causes and effects of contamination as well as what to look out for.