Case Study - Tidal - Bleadon STW
Project: Bleadon STW
Project Location: Bleadon Sewage Treatment Works
River System: River Axe
Client: Wessex Water plc
Date of Installation: May 2006
Project Brief
Arrest the escalating tidal erosion associated with a temporary outfall pipe from the STW.
The installation breached the vegetated transitional zone, creating an aggressive erosion path between the lower mudflats and the upper salting SSSI.
Ebbing flows resulted in a deep incision which migrated into a gully of worrying proportions.
Arresting this process and protecting the SSSI were key project objectives.
Solution
An urgent and effective response was required, so Cain Bio-Engineering installed a contoured brushwood wedge, anchored with hardwood stakes.
Suspended sediment, deposited during each tidal cycle, will accrete in the brushwood mattress over time, thus ensuring the long-term integrity of the structure.
Brushwood marginal matresses were installed where severe block failure on the intertidal saltmarsh have caused steep erosional cliffs to form. These sloping matresses will fill with sediment during each tidal cycle reinstating a smooth transition between lower mudflats and the saltmarsh preventing any further serious erosion.