Drain Tracing

& Mapping Surveys

Understanding your drainage system isn't just good practice, it's essential for environmental compliance, spill response planning, and protecting your site from costly pollution incidents.

Drain Tracing & Mapping Surveys

Site Drainage

A thorough understanding of your sites drainage system is a fundamental aspect of pollution prevention. A well-designed and properly maintained drainage system plays a critical role in preventing pollutants - such as oils and chemicals - from entering nearby watercourses or contaminating groundwater supplies. When spills are allowed to enter the drainage network and pollute controlled waters or groundwater, the environmental impact can be significant, and the associated clean-up costs substantial.

Drainage systems can serve as pathways to various environmental receptors:

Controlled waters: Spills entering the surface water drainage system may discharge directly into controlled waters - such as rivers, lakes, and streams - or via a public surface water drainage system.
Groundwater: Surface water drainage can lead to groundwater contamination through soakaways or damaged drainage infrastructure, allowing pollutants to percolate into the soil.
Sewage Treatment Works: Spills that enter foul or combined drainage systems typically flow to local sewage treatment facilities. If the spill disrupts the biological treatment process by harming essential bacteria, the polluter may be held financially responsible for the restoration of the system.

Given these risks, it is crucial to have a clear understanding of your drainage layout. This knowledge enables quick identification of potential discharge points in the event of a spill and ensures timely notification of the appropriate regulatory authorities:

For surface water or groundwater spills: Environment Agency (EA), Scottish Environment Protection Agency (SEPA), Natural Resources Wales (NRW), or the Northern Ireland Environment Agency (NIEA).
For foul or combined drainage spills: The local sewerage undertaker.

A comprehensive drain plan should include detailed information on:

Drainage routes
Potential pollutant sources and associated site activities
Existing control measures
Discharge points

To support this, our drain mapping survey provides an accurate assessment of your sites drainage infrastructure. The survey identifies surface water, foul drainage, and effluent pathways, along with interceptors, separators, and control devices such as drain closure mechanisms. The process involves lifting inspection covers and visually inspecting each chamber to trace and document drainage routes.

Drain Tracing Surveys

We offer expert drain mapping to provide a complete drainage overview. Our process includes:

Collating and studying all existing drainage plans
Establishing connectivity of all site drainage (through visual inspection and dye testing)
Measuring invert levels and pipe diameters
Investigating outfalls/off-site discharge of storm and foul systems
Identifying any environmental control measures e.g. interceptors
Delivering data on a colour-coded CAD site plan, with an index of all drains and drainage features
Providing recommendations for remedial action
Optionally marking drain covers in accordance with their usage (red = foul, blue =storm) enabling easy identification in the event of an incident

Why Drainage Awareness Matters

In addition to the clear environmental advantages, maintaining an accurate and up-to-date drain plan can also offer significant financial benefits.

In the UK, water companies calculate sewerage charges based on estimated volumes of wastewater directed to sewage treatment works. If your site’s stormwater drainage discharges - either partially or entirely - into a natural watercourse (such as a river, stream, or soakaway) rather than the public sewer system, you may be overpaying for sewerage services.

By verifying the actual discharge routes through a detailed drain survey, you may be able to demonstrate that these charges are inaccurate and potentially reduce your ongoing costs.

All sewerage undertakers in England and Wales offer a surface water rebate scheme, allowing businesses and homeowners to claim refunds for past overpayments or to lower future sewerage charges. These rebates are available where it can be shown that surface water does not enter the public sewer system.

While each water provider has its own specific application process, all require an accurate and up-to-date drainage plan as supporting evidence. Our professional drain mapping surveys are designed to provide this documentation, enabling you to: