Managing the downstream impact of silt removal (dredging and desilting) projects can pose a challenge to our clients.
Suspended sediments are a significant source of pollution that can degrade habitat, reduce oxygen in the water column and spread contaminated materials.
However, silt removal is also essential to the upkeep of a waterway, whether preserving important heritage and habitat features or maintaining commercially important navigations. Bubble Tubing has demonstrated that it can significantly reduce the harmful impacts when doing this essential management work.
The Penllergare Trust faced this challenge when planning the restoration and management of their estate, a landscape rich in natural beauty. The lakes created within the River Llan are an important heritage and biodiversity feature of the valley woods. However, the lakes also act as a natural silt trap and require periodic dredging in order to maintain them.
frog environmental has been working with The Penllergare Trust and Natural Resources Wales on in-channel silt mitigation to help restrict the movement of silt plumes downstream. A bubble barrier, incorporating two lines of Bubble Tubing® was deployed in the River Llan. The resultant turbulent flow currents were estimated to have held back 80% of suspended material, only releasing the finer silt particles.
Geo-textile curtains were then positioned downstream to the bubble barriers to increase the retention of very fine silt.
Downstream receptors include a trout farm as well as other sensitive sites; managing the movement of silt plumes was therefore an important aspect of this project.
One of the benefits of using Bubble Tubing on site is the ease of deployment, with no technical expertise required for installation. No regulatory approval was required ahead of deployment; in fact having the bubble barrier as mitigation supported the attainment of a Flood Risk Activity Permit for the project
The Penllergare Trust and Natural Resource Wales were happy with the results of the silt mitigation. The bubble barrier system using Bubble Tubing, originally on hire has now found a permanent home with the Trust.
Bubble Barriers are regularly used in both permanent and temporary installations to control silt plumes, hold back litter, debris and floating weed and provide intensive aeration to improve the health and amenity value of water bodies.