Concrete wash water should I be concerned

The Short Answer

Yes — concrete wash water is something to be concerned about, particularly if it is allowed to enter a drain, stream, river, soil or groundwater untreated.

The concern is not simply that it looks like dirty water. Fresh concrete wash water can have several significant pollution characteristics:

• Very high alkalinity: concrete wash water can have a very high pH and can be corrosive. A sudden release into a watercourse can seriously affect aquatic organisms.

• Suspended solids: cement and fine particles can settle on the bed of a stream, affecting habitats and aquatic insects.

• Water pollution: the Environment Agency identifies concrete slurry as a substance capable of causing pollution and advises that contaminated water from concrete activities should be contained and treated or recycled.

How concerned should a construction site be?

Think of concrete wash water as a high-risk pollution source that is relatively easy to control.

A sensible hierarchy is:

1. Prevent escape

2. Collect in a contained washout facility

3. Separate the solids from liquid, dispose of the solidified wastes

4. Monitor and correct the pH of the liquid phase

5. Allow solids to de-water/solidify

6. Reuse/recycle where permitted/appropriate

7. Lawfully dispose of any remaining water, assign the correct EWC code

For England, the current Environment Agency RPS 287 specifically covers storing, treating and using concrete-containing wastewater at construction sites. It permits certain activities without enforcement action for the underlying waste-permit requirement, provided all its conditions are met. These include secure containment, a 10% freeboard, a maximum of 30 m³ at a single location, pH monitoring and specified treatment methods.

Importantly, RPS 287 does not give a general right to discharge concrete wash water to a river, surface water or ground. The Environment Agency says that appropriate permitting/consent is required for those routes.

What about workers?

There is also a health and safety issue. Wet cement/concrete and concrete wash water is strongly alkaline and can cause skin and eye burns. Therefore, washout arrangements should control both environmental release and worker exposure.

The key message

For a construction site, consider untreated concrete wash water as being a:

• A controlled waste stream requiring containment and appropriate treatment — not ordinary site water that can be poured down a drain or onto the ground.

• If you are disposing of the wash water, it should be treated as a waste material in accordance with the duty of Care for Waste Management. For information on assigning the correct EWC code for treated and untreated concrete wash water CLICK HERE

• The environmental and health and safety risk associated with concrete wash water can eaisly be managed and mitigated, provided due care and attention to the hazardous nature and pollution poptential associated with the waste material.

Concrete Wash Water Working Group

The Concrete Wash Water Working Group brings together industry professionals and stakeholders with an interest in improving the management of concrete wash water on construction sites.

The purpose of the group is to promote best practice in the treatment, storage and management of concrete wash water, helping construction projects to reduce environmental risks and maintain high standards of health and safety.

For more information on the Concrete Wash Water Working Group CLICK HERE