ENV/Water Pollution/TBT-ENV-017

Surface Water Drainage Protection

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Surface Water Drainage Protection

Toolbox Talk Record

Ref: TBT-ENV-017  |  Issue: 1  |  Date: March 2026
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What?

  • Surface water drains on and around construction sites often discharge directly into rivers and streams.
  • Unlike foul sewers, surface water drains have no treatment — pollutants reach watercourses untreated.
  • Silt, cement, fuel, and chemicals entering surface water drains cause serious environmental pollution.
  • The Environmental Permitting Regulations 2016 make it an offence to pollute controlled waters.
  • Drain covers must be identified and protected to prevent pollutants entering the surface water system.
  • Construction sites should have a drainage plan showing which drains are surface water and which are foul.
  • Silt fences, straw bales, and settlement ponds help prevent sediment reaching surface water drains.
  • Concrete washout water is highly alkaline and must never be discharged to surface water drains.
  • A single pollution incident can result in unlimited fines and criminal prosecution.
  • Protecting surface water drainage is a condition of most planning permissions and environmental permits.

Why?

Protect watercoursesSurface water drains flow directly to rivers and streams — any pollutant entering them causes immediate environmental harm.
Legal consequencesPolluting controlled waters is a criminal offence carrying unlimited fines and potential imprisonment.
Ecological damageSilt, cement, and chemicals kill fish, invertebrates, and plants, sometimes taking years for ecosystems to recover.
Do Don't
  • Identify all surface water drains on site and mark them on the drainage plan
  • Protect surface water drain inlets with covers, neoprene mats, or drain guards
  • Install silt fences and settlement ponds to intercept sediment before it reaches drains
  • Direct concrete washout water to designated containment areas only
  • Store fuel, oil, and chemicals on bunded hard standings away from drains
  • Brief all site workers on the location of surface water drains and protection measures
  • Inspect drain protection measures daily and after heavy rainfall events
  • Report any spill or discharge to a surface water drain immediately
  • Use spill kits promptly to contain and clean up any accidental releases
  • Keep a site drainage plan in the site office for reference by all personnel
  • DON'T discharge any liquid into surface water drains without authorisation
  • DON'T wash out concrete, mortar, or plaster into surface water drains
  • DON'T store chemicals or fuels where spills could reach surface water inlets
  • DON'T remove drain protection measures without replacing them immediately
  • DON'T assume a drain goes to foul sewer — check the drainage plan first
  • DON'T allow site vehicles to track mud and silt into surface water gullies
  • DON'T pour paint, solvents, or cleaning agents into any drain on site
  • DON'T ignore blocked or damaged drain protection — repair it straight away
  • DON'T pump silty water from excavations directly into surface water drains
  • DON'T wait to report a pollution incident — early response limits the damage

See also: Pollution Incident Reporting | Silt and Sediment Control
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