Concrete wash water, a byproduct of cleaning concrete mixing equipment, (i.e. concrete mixers, concrete batching plant, delivery lorries, chutes, pump lines, drums and wheelbarrows) contains high pH levels and various contaminants.
The regulatory position statement (RPS) 287 from the Environment Agency – ‘Treating and using water containing concrete at construction sites: RPS 287’ reduces the need for transporting wash waters containing concrete off-site and allows for its immediate reuse on site.
That is a good thing.
However, concrete water can be highly polluting if released into the aquatic environment.
Typically, it has a high pH (11-12) due to calcium hydroxide (derived from the cement), high suspended solids, and other trace materials.
Some of this originates from cement, others from additives or from the mixing equipment.
Operating under the RPS will not absolve an operator if the activity causes or is likely to cause pollution of the environment or harm to human health.
Please be aware that the RPS does not apply to water containing grouts!
The use of concrete wash water must not:
- Cause a risk to water, air, soil, plants or animals
- Cause a nuisance through noise or odours
- Adversely affect the countryside or places of special interest
However, proper management and reuse of concrete wash water can offer environmental and economic benefits.
Potential uses of concrete wash water
So, which of the following uses of concrete wash water are allowed under the RPS?
Dust suppression
- This is not allowed under the RPS due to environmental and human health risks associated with Chromium VI.
Washing plant and equipment
- Yes, provided the wastewater is treated.
Concrete mixing
- Treated or untreated wash water can be reused in the concrete mixing process. This not only conserves water but also reduces the need for fresh water, making the process more sustainable. The storage, treatment and use of waste water containing concrete for producing new concrete is an activity expressly authorised by the RPS.
Curing Concrete
- Wash water can be used for curing concrete, maintaining moisture in the concrete to ensure proper hydration and strength development. Be aware that the RPS does not specifically mention this activity, so it is advisable to check first with your local Environment Agency office as to whether this activity is acceptable and whether the wash water needs to be treated.
Steps for using concrete wash water without a permit under the RPS
To use concrete wash water without a permit, certain best practices and guidelines must be followed to ensure environmental safety and compliance with regulations.
These steps are explained in the RPS (applies to England only) published by the Environment Agency on 23.10.2024.
A copy of the RPS can be downloaded from here.
The RPS applies only to situations where the use of the concrete wash water is on the actual construction site.
Otherwise, the concrete wash water must be disposed of in compliance with legal requirements.
This may involve discharging it to a sewer with the sewerage undertaker’s consent, directing it to surface water under a water discharge activity permit, or managing it under a groundwater activity permit.
Alternatively, it can be transported off-site for appropriate treatment.
The compliance requirements under the RPS are as follows:
Method statement
A method statement must be followed which minimises the risk of pollution, including but not limited to control measures, monitoring and inspection, staff training and incident response planning.
Records
Records must be kept for two years from the date of last use of the RPS to demonstrate compliance with the RPS.
You must keep detailed records of the amount of wash water collected, treated, and reused.
You must regularly monitor the quality of the treated water to ensure its PH meets the required standards for use.
Likewise, you must keep detailed records demonstrating lawful discharge of waste waters to groundwater, surface water, sewer or transfer.
Training and awareness
You must train all personnel involved in handling and treating wash water on best practices and safety measures.
Ensure they understand the importance of proper management to prevent environmental contamination.
Containment
Wash water containing concrete must be stored in designated, leak-proof containers to prevent it from entering waterways or soil.
Ensure containers are covered to avoid overflow from rainfall.
A freeboard of 10 per cent of the capacity of the tank, engineered lagoon or leakproof skip must be maintained.
A maximum of 30m3 of wastewater containing concrete washings can be stored at any time in a single location on the construction site.
Authorised On-Site Treatment:
- pH Adjustment – Prior to use for washing you must treat the wash water to adjust its pH to a neutral level (around 7-8). This can be done using pH adjusters like acids or carbon dioxide.
- Solids Separation and filtration – Use mechanical filtration methods, such as filter presses, to remove suspended solids and aggregates from the wash water. This step is crucial to prevent clogging and ensure the water is suitable for reuse.
- Using products that solidify water containing concrete prior to use (but not flocculants or other chemicals for any other purpose)
The activities associated with storing, treating or using water containing concrete must not be carried out within 10m of any watercourse or within 50m of:
- Sites of special scientific interest
- Special Areas of Conservation (SACs) including proposed SACs
- Special Protection Areas (SPAs) including potential SPAs
- Ramsar sites – wetlands of international importance (both listed and proposed)
- Marine Conservation Zones
- Other nature conservation sites, such as ancient woodlands and local and national nature reserves
- Local wildlife sites
By following the steps set out in the RPS, construction sites can effectively manage and reuse concrete wash water, minimising environmental impact and adhering to regulatory guidelines without the need for a permit.
The Environment Agency has stated it will review its RPS by 30 June 2027.
It can withdraw or amend an RPS prior to its review date so it is important to review the Government website from time to time to check the RPS still applies or has not been modified.
Set concrete/solid residues may be suitable for construction uses around the site but a permit or exemption (e.g. U1) would be needed.
If you require further information or guidance on the safe application of concrete wash water, Please contact John Dyne today.