Solids in discharge water at mines and quarries; removing silt and sediments

You must manage solids at your mine or quarry so that they do not cause water pollution. If you discharge excessive solids to a watercourse you could smother the aquatic life, or cause flooding by blocking channels.

Your run-off may contain solids from:

  • extractive operations that use water, e.g. hydraulic processes to extract China clay
  • mineral washing and processing activities
  • water removed from your excavations, e.g. during dewatering
  • spoil heaps and stock piles
  • washing vehicles, work areas and equipment.

What you must do

If your business has a permit, licence or exemption you must comply with its conditions, including any conditions about solids. If you do not comply with conditions, you can be fined or sent to prison.

Does your mining or quarrying business need a permit, licence or exemption?

You may need a permit or permission from your regulator if you discharge water from settlement ponds to the public sewer, surface water or groundwater. For further information, see our guidance on discharges to water and sewer.

You must comply with any requirements in your waste management plan about managing solids at your site.

Good practice

Design your mine or quarry so that contaminated run-off is prevented from leaving your site.

Minimise the amount of ground you expose and stockpiles you use at your site.

Cover or screen stockpiles, tips and mounds, plant vegetation or use retaining fences to prevent solids from being washed or blown away.

Do not remove vegetation from your site until you need to work in that area.

Divert clean water and prevent water from entering your excavations by using cut off ditches around your working area.

Use settlement ponds, tanks or lagoons to collect run-off from your site and let suspended solids settle so you can remove them from the water. You must make sure that you:

  • design your settlement pond carefully so it can take the amount of water that will flow through it
  • can stop discharges from your pond if the water becomes contaminated
  • do not cause water pollution from any flocculants you use, such as polyelectrolytes or alum
  • treat water entering your settlement pond if it is contaminated by pollutants other than suspended solids.

Use sustainable drainage systems (SuDS) to control surface water run-off at your site, such as grass swales, ponds or infiltration trenches. SuDS deal with run-off close to the source by slowing and holding back the run-off from your site and allowing natural processes to break down pollutants. For further information, see our SuDS guidance.

Collect run-off from your roads by using ditches and build bridges to cross watercourses.

Clean your site roads regularly and keep them free from dust and mud.

Use designated vehicle washing areas and collect contaminated water in a sump. For further information, see our vehicle cleaning guidance.

Consider whether you need to build any flood attenuation ponds and spillways upstream of your site to prevent your settlement ponds from overflowing and causing pollution after heavy rain.

Further Information

DAERA: Guidance for the Wise Use of Water in the Aggregates and Quarry Producers Industry

SEE ALSO: Mining and quarrying sector guidance

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