Beneficial use of dredged sediment
Dredged sediment was used along the fronting Trimley foreshore and also within the Trimley Managed Realignment site over separate campaigns.
Along the adjacent foreshore in 2003, a gravel bund and silt were placed. Approximately 22,000 m³ of gravel was placed to create the bund (1.4 km in length) running parallel to the seawall and approximately 50 to 60m seaward of it and silt was placed behind it. This was done to protect the wall and the protected habitat behind it as well as to create/restore new shingle and intertidal habitat.
The foreshore was raised by around 2m in height and, due to its tidal elevation, the silt that was pumped behind the shingle barrier remained as mudflat habitat.
In the realignment site, 35,000m³ of fine mud was placed in 1998 and 2001. These were retained using clay bunds.
The sediment was pumped via a floating pipeline through the breach to a floating pontoon from where it was discharged onto the site. This was done using maintenance dredgings (fine mud) from the channel in the lower Orwell estuary which were pumped into the site to provide a suitable substratum for colonisation of estuarine flora and fauna.
The material was deposited in four locations at high water, from where it was spread out over the site.
The dredged material formed a layer approximately 30 to 50cm deep above the underlying soil.