Beneficial use of dredged sediment
Orwell Estuary (Suffolk)
This was an early trial beneficial use project which ended up paving the way for much larger initiatives in the estuary in later years. The main aim of this work was to monitor the behaviour of fine silts placed within the protective gravel bund. The work was done in 1997/98 as a joint venture between Harwich Haven Authority and the Environment Agency. In total around 22,000m3 of maintenance dredged sediment (mostly silt of 20µm in size) was placed on site. These were retained using 75,000m3 retaining bund of coarse, poorly sorted, gravel. The mud was pumped over 450m of the foreshore and across a maximum width of 70m to an initial elevation of between 1.0 and 1.3m above Ordnance Datum (OD). In 2004 areas of existing gravel was topped up with silts and another scheme constructed based on bunds created using in-situ material backfilled with 0.3m of silts.