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Drainage Arrangements: Common Mistakes

This blog will cover some of the mistakes discovered during site assessments, maintenance and mapping visits that we see and explain why they can cause problems.

Vehicle Wash Arrangements

Whether an automated vehicle wash or simply an area where windscreens are washed off, they should always be serviced by foul water drainage to ensure the contaminated effluent does not escape to the environment (surface water drains lead directly into the environment whereas foul water drains go to water treatment works). Any vehicle wash effluent, even if it is generated from a quick rinse of a windscreen must go down a foul drain. Common issues are wash-down areas leading to surface water drains or overflow of effluent into surface water drainage (even if the area itself is connected to the foul system).

Floor Wash Effluent

If you carry out floor washing, you will create effluent that needs to be disposed of. As with all effluent, this must be discharged to a foul drain. We often see floor wash effluent being discharged to surface water drains or to an unmarked drain where it is unclear whether it goes to the foul or surface drainage system.

Trade Effluent Licencing

Any liquid waste generated from your activities such as vehicle, floor or tray washing is classified as a trade effluent and must be discharged to a foul drain with permission. This would be a valid Trade Effluent Licence from the Water Company responsible for the foul drainage system and will include limits that must be adhered to. There may be limits on the quantity you can discharge, the times of discharge and what the effluent can contain. Issues with trade effluent licencing on sites include the absence of a trade effluent consent, the conditions of the consent not being followed (e.g. if monitoring is required, or the discharge exceeds the limits imposed) or the licence not covering all discharging activities from site.

Drain Confusion

In order to effectively control your pollution pathways, you must be aware of the accurate drainage arrangements on your site but we sometimes visit sites where the drainage arrangements are not transparent. Some sites do not have a drainage plan at all, while others may have inaccurate or hard to understand plans. This can lead to effluent being discharged to the wrong system and drains being painted incorrectly (if at all). In some cases, there may be a misconnected drain that carries sewage but leads to surface, rather than foul drainage, which is illegal. You have a responsibility to ensure that pollution does not escape your site and cause environmental damage. Part of that obligation is to be aware of your drainage arrangements and manage them correctly. This includes ensuring any liquid waste is discharged to the foul drainage and having the correct permissions in place for this and having full knowledge of your drainage system and correcting any issues.