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Swimming in sediment: Unveiling the murky world of pollution and its fishy consequences

Naturally Compliant delves into the impacts of sediment laden water finding its way from construction sites into watery habitats populated with fish. We also provide advice on how to ensure the message about the potential environmental impacts is heard by the people that matter.

For an Environmental Clerk of Works (ECoW) working on a construction site, one of the greatest challenges is preventing the escape of silty water into aquatic environments such as streams, rivers and lakes. However, the status of dirty water as a pollutant, and the ecological damage it can cause, is not always fully understood on construction sites.

A common misconception is that because silt and silty water is non-toxic, non-corrosive and non-flammable it will do little harm to the ecology of a water body. This simply isn’t the case, and examples of the harm it can cause include:

  • The suffocation of fish by blocking gills

  • Blinding of gravel beds causing disruption to spawning fish or failure to spawn

  • Visual impairment of fish disrupting their escape from predators

  • Smothering of aquatic invertebrates and loss of habitat

  • educed dissolved oxygen if the silt contains significant organic material (that biological oxygen demand)



What is pollution in water, and why does it matter?

Legally, pollution in relation to the water environment means the direct or indirect introduction of substances (including bacteria and other pathogens), or heat into the water environment, which may give rise to harm because of human activity such as construction activities. Therefore, in addition to the physical impacts, sediment entering the water environment meets this definition and should be treated as such.

A conscientious site operative who has been trained in emergency response is likely to react quickly and appropriately to a serious pollution incident such as an oil spill. But that same operative may not respond in the same way to a silt pollution incident, because they lack the knowledge and understanding of its potential to cause harm.

Engaging courses and toolbox talks (TBTs) can be used to raise awareness of the impacts of silty water. By making the connection between silty water and the negative effect it has on fish populations, and therefore fishing, is one way of presenting the challenge in context of a widely practiced sport.

A serious challenge made easy to navigate

Silt pollution is a serious environmental challenge on a construction site and Naturally Compliant knows exactly what can be done to improve communication and introduce effective mitigation strategies. For more information on successful water management planning, please contact Simon Knott at,


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