Construction or other activities, such as dredging in aquatic environments, can have negative impacts on water bodies from the disturbance of sediment in the riverbed. Runoff from wet weather can also be a serious issue, resulting in fine sediment pollution entering the water. This is one of the most common forms of pollution in watercourses.
Fine sediment entering the water body can impact resident wildlife, especially sensitive species, and affect turbidity causing issues for water quality.
This is where silt mitigation comes in. Using silt curtains can help to minimise the impact of development work or runoff on a water body.
How silt mitigation methods work
Silt curtains, also known as silt barriers or silt screens, can be used to enable activity such as dredging, piling or construction to occur in sensitive freshwater or marine locations, keeping the water free from potential pollutants and excess sediment.
A silt curtain is a structure made from permeable or impervious materials that is placed suspended in the waterbody. It acts as a barrier that captures sediment being carried within the moving water current. It can contain disturbed silt up to a couple of metres in depth.
As the contained sediment cannot disperse, it ensures the suspended fine sediment can drop back to the bottom. This approach provides the necessary conditions for the suspended sediment to settle where it will no longer disrupt the water body.
When to use this approach
Sediment control and mitigation is often required for the following projects:
- Bridge construction or repair
- Rock wall construction or repair
- Jetty construction or repair
- Civil works in or adjacent to waterways
- Coastal or marine dredging
- Sediment pond management
- Tailings dams dredging
There are legal obligations that must be followed to prevent sediment causing disruption to aquatic environments and resident wildlife. Silt mitigation ensures that development and other damaging activities are compliant with the Water Framework Directive that seeks to protect these environments.
How APEM can help
APEM is experienced at supervising desilting operations having undertaken them for water companies on numerous sites across the UK.
Our team of field scientists are able to monitor river conditions, such as dissolved oxygen and ammonia concentrations, and then implement the necessary mitigation measures to control fine sediment, including silt curtains and sediment traps. The field team can safely capture and relocate wildlife that may be at risk from sediment disturbance.
APEM has pioneered the use of satellite imagery and high-resolution aerial imagery to identify sources of pollution by fine sediments across whole river catchments.
We provide practical advice and ongoing support as part of our Ecological Clerk of Works (ECoW) service which includes:
- Protected species surveys
- Virtual ECoW advice (by phone and video calls)
- Legislation and practical advice
Other sediment services we offer include identification of catchment sources of rural and agricultural diffuse pollution, and expert advice on fine sediment management and associated diffuse pollution.
Get in touch to find out more about how APEM can support you with sediment mitigation services.