Environmental guidance for your business in Northern Ireland & Scotland

Using bentonite on construction sites

Bentonite clay on construction sites

Bentonite can be highly polluting to water if it is released into the environment.

What you must do

Storing bentonite, mixing areas and supply lines

If you are using bentonite, ensure that it is contained within your working area and does not enter any watercourses or surface water drains.

Ensure that storage silos are bunded.

Surround areas where bentonite is mixed with a small wall or contain them within a bund. This will help to control the slurry produced and prevent it from entering surface water drains or watercourses.

Position bentonite storage silos and supply lines as far as possible from surface water drains or watercourses.

Using bentonite

Keep a record of the amount of bentonite that you use. If you are tunnelling and you find that you are using larger quantities of bentonite than you anticipated it is possible that these materials are escaping into the ground and potentially polluting groundwater.

Screening plants and centrifuge systems

Screening plants used to remove sands or gravels from bentonite, or centrifuge systems used to remove water from slurry, can be extremely noisy. Position these systems as far away as possible from the nearest housing.

Disposing of bentonite

You must not dispose of liquid wastes to landfill. It can be difficult to determine whether slurry is a liquid or not.

Liquid waste can be defined as:

  • any waste that near instantaneously flows into an indentation void made in the surface of the waste
  • any waste (load) containing free draining liquid substance in excess of 250 litres or 10%, whichever represents the lesser amount.

Before you dispose of bentonite, you must check with your waste contractor where the material will be taken and how it will be treated. There are a limited number of licensed waste disposal sites that can accept slurries for treatment prior to disposal.

Duty of care - your waste responsibilities

Hazardous / special waste

Clean, unused bentonite is classed as non hazardous waste.

You must dispose of any waste that contains hydrocarbon, for example hydraulic oils or diesel, as hazardous/special waste.

This can include tunnel spoil and bentonite that have been in close contact with leaking equipment. You will need to test this material in a laboratory to find out whether it is suitable for landfill and whether the site that you intend to take the waste to is allowed to accept it.

SEE ALSO: dewatering during construction, Settlement tanks

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