What is Contaminated Soil and How Do You Remediate It?

Occasionally, you’ll hear about soil contamination. It can be harmful to health and dangerous for children and pets—so how can you fix the problem?

If you’re buying, building, or repairing your home or commercial property, you need to ensure the land hasn’t been used for any hazardous activities or has been contaminated in any way.

What is land contamination?

Land contamination is when hazardous chemicals, metals, or hydrocarbon compounds are stored, used or disposed of on a property. These chemicals leach, are spilled or dumped onto the land and can make the land unsafe. These substances could also migrate to soil from a spill close by, often carried by groundwater.

These contaminants could include:

  • Petrol/ diesel/ fuel
  • Chemicals from power stations or gasworks
  • Insecticide/ fungicide etc from agricultural or horticultural use
  • Sheep dipping from farming
  • Timber treatment chemicals
  • Industrial facility discharge
  • Mining operation residues
  • A range of outcomes from a HAIL (Hazardous Activities or Industries List) organisation

The soil contaminants commonly found in NZ include things like:

  • Asbestos
  • Lead
  • Arsenic
  • Mercury
  • Cadmium
  • Pesticides
  • Mercury
  • Polycyclic aromatic hydrocarbons
  • Chemicals from methamphetamine creation

Why is land contamination so bad?

Soil contamination exposes humans and animals to harmful chemicals and metals. The exposure can be from:

  • Inhaling dust
  • Direct skin contact
  • Ingesting the soil from eating unpeeled or unwashed produce
  • Sometimes eating the produce itself

The type of harm depends on the amount ingested/ inhaled, the length of time you are exposed to the contaminant, your body size, and the type of chemical or metal. Many of these harmful substances accumulate over time (this is called bioaccumulation), making them highly toxic over time, even with trace amounts in the soil itself.

Children in particular can suffer more than adults because of their smaller body size, and also their habits; a baby crawling on the ground will have more contact with soil contaminants.

Short term exposure can cause:

  • Headaches
  • Chest pain
  • Coughing
  • Nausea
  • Skin and eye irritation

These problems typically resolve once the soil contaminant is removed.

Long term, prolonged exposure results in considerably more serious problems:

  • Nervous system depression
  • Neuromuscular blockages
  • Damage to internal organs such as kidneys and liver
  • Cancer, such as leukaemia after exposure to benzene

These effects can be difficult or impossible to reverse.

How to reduce exposure to soil contaminants

If you have soil contamination on your property, there are some things you can do to reduce your exposure. Adding a layer of soil and grass/ ground cover plants over the contaminated soil will reduce the dust and remove the immediate threat of direct contact soil. As well as this:

  • Do not let children play (or eat) contaminated soil
  • Wash your hands after soil contact and before eating
  • Wash children’s hands regularly
  • Wash outdoor toys and family pets regularly
  • Remove footwear when coming inside
  • Mop/ dust often with a damp cloth
  • Use a vacuum with a HEPA filter
  • Have doormats at each entrance to the house
  • If you grow produce in the contaminated soil, wash it thoroughly and peel all root vegetables before eating. Growing vegetables and fruit in contaminated soil is not advised.

When to get the professionals involved

There are a number of scenarios where getting professional soil decontamination is advised. 

  • If levels of contamination are high
  • If you wish to grow produce
  • If you need resource consent for a build/ repairs
  • You intend to subdivide the land or change the type of land use

Contact your local soil decontamination business and speak to them about the options available to you.

Initially, there should be thorough sampling and tests, to see the type of contaminant and how extensive the problem is. They may advise that topsoil/ gravel/ grass addition is enough to protect you and the family from any dangerous metals or chemicals. If the contamination is bad, they could recommend removal of the toxic soil, but this just means there are two places with contaminated soil.

There are also soil cleaner products which may be able to be used that can accelerate the remediate of spill sites. As well as this, depending on the type of contamination and site, they could recommend wall systems, bioremediation, or air sparging. 

If you are unsure, if you face penalties from the local governing bodies if you decontaminate incorrectly, or if you are concerned about the health and wellbeing of your family, call the professionals. There is no substitute for thorough testing, work being carried out in a skilled way, and the peace of mind that using a professional brings.

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