Best Practice for Pollution Prevention Part 2: Drain Protection
In Part 1 of our Best Practice Guide to Pollution Prevention, we looked at spill control which deals with hydrocarbons. In Part 2, we consider another common contaminant – sediment or silt – and why drain protection is a necessity.
Sediment disrupts freshwater and marine ecosystems leading to a reduction in biodiversity. Consequently, it is illegal in most cases to discharge silt-laden water directly into the environment.
Flawed Drain Protection
When it rains, mud is washed from your site into the nearest surface water drains. This water may also be contaminated with oil and fuel from equipment and vehicles. Additionally, you may pump muddy water from excavations straight into the drains on your site.
Surface water drains run straight into natural waterways like rivers or the sea, so any silt or hydrocarbons in the water directly impact water quality. A build-up of sediment can also block drains leading to localised flooding and expensive clean-up costs.
So what’s the best way to protect drains?
Drain covers and mats prevent anything getting into the drain but they just pass the problem down the road, depositing silt as it goes. This is a skid risk for cyclists and motorists, a slip risk for pedestrians and unsightly for local residents. There are more responsible approaches.
Another approach involves wedging a drain bag inside the gully pot. This allows water to flow through but traps sediment. A common complaint is that the weight of sediment can cause the bag to fall to the bottom of the gully pot rendering it ineffective and making it difficult to remove. Removing the bag often causes it to split shedding the polystyrene pellets inside. We’ve visited construction sites where split bags have been left near the drains with the wind dispersing the polystyrene.
Best Practice Drain Protection
In order to protect drains in a more responsible and effective way, a drain filter is widely considered to be the best approach. This is suspended inside the gully pot and filters out sediment and debris as run-off passes through.
The big advantage of drain filters is that they can be easily emptied and reused if they fill up. The Green Rhino EnviroHorn™ Drain Filter is a robust and long-lasting approach popular with leading housebuilders and civil engineering companies. A new drainage system is often installed early in a housebuilding project and muddy site roads can lead to a high volume of silt-laden water so a reliable and reusable solution is highly advantageous.
Balfour Beatty has listed EnviroHorn on the Considerate Constructors Best Practice Hub. Find more information on EnviroHorn here.
Click here for Part 3: Dewatering and our tips on how to get best practice adopted across all your sites.