Beneficial use of dredged sediment
Blackwater Estuary (Essex)
At Pewit Island sand/shingle was placed using material from Harwich which was 'rainbowed' onto the site via the Sospan Trailing suction hopper dredger. This eased the rapid erosion and provided a very successful nesting site for little tern (60 pairs in year 1). This pumped Harwich shingle was after year 1 backed with a brushwood fence to ease migration of that material onto the salting. The shingle washed against it, raised itself to HAT and stabilised (the same method was used on the shingle recharge on Cob Marsh and Old Hall Point). In 1992 and 1995, a total of 2,529m3 & 2,646m3 respectively of dredged fine muddy sediment was pumped on site. No retaining devices were used as the sediment is allowed to dissipate. The sediment is generally placed on the western point of the island. The more regular silt sediment recharge work is done by pumping marina dredgings through a pipe from Bradwell. The silts are pumped onto the top of the salting and formed a stable marsh out of what was an eroding system. This work is ongoing.