That is the conclusion of wastewater solutions manufacturer Siltbuster, which said clarification set out by the EA in its regulatory position statement (RPS) “provides clear guidance on the environmental permitting treatment needs for the disposal of wash water generated from rinsing truck mixer chutes”.

Under the new guidance to improve washwater disposal practices at construction sites, sites are classified as small, medium, large or very large depending on the number of concrete deliveries received per week and the resultant amount of high pH water generated.

It recommends that where possible washwater is reused, or when this is not possible it is disposed into a foul sewer, which presents the smallest environmental risk. Meanwhile, the disposal to ground or surface water should be used as a last resort.

However, Siltbuster managing director Dr Richard Coulton said that while the guidance is a “step forward” that it fails to address the issue of high pH water generated from washing other equipment used to handle wet concrete, such as concrete pumps and batch plant.

This, he claimed could lead to a miscalculation on the number of truck movements, causing site managers to significantly underestimate the risk posed to the surrounding environment. Furthermore, he warned that time-pressured site managers may be tempted to ignore the advice and risk fines or prosecution.

He said: “Construction managers need to understand how this affects their sites and plan ahead to ensure the treatment and disposal of concrete washwater is managed professionally.”

A failure to dispose of washwater correctly can lead to a sewer blockage – an issue utility companies and the EA are keen to tackle.

In order to overcome this problem, Dr Coulton recommends categorising each site on the total volume of high pH water generated, rather than the number of concrete truck movements, adding that water must also be appropriately treated prior to discharge into sewer to tackle the “common misconception on many sites that the pH can be reduced by simply flushing the concrete washwater down the sewer together with copious amounts of mains water”.

Additionally, he said it is important to confirm that the discharge point is connected to the foul sewerage network and not a storm water drain, which simply discharges to the nearest surface water course.

Currently, all discharges to the environment are covered by the control of pollution legislation and may not require an environmental permit, depending on the site of the concreting operations, while discharges to ground or surface water from small to medium sites do not require environmental permitting by the EA, provided they meet certain criteria and that an appropriate risk assessment has been carried out to demonstrate that pollution will not occur.

“The underlying message is clear,” concluded Dr Coulton, “the EA now recognises that the uncontrolled release of high pH concrete washwater can be a major hazard to the environment and must be treated as such.”

Carys Matthews

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