Emergency dredging is clearing Lyttelton port’s choked shipping channel from a build-up of marine mud brought in by big storms. The Lyttelton Port Company began dredging late last month to clear seabed silts and clays in the harbour’s main navigation channel for ships. Nearly one million cubic metres of sediment was swept into the channel since the port’s maintenance dredging programme last November, compared with a typical yearly amounts of 600,000-800,000cu m. Chief customer and supply chain officer Simon Munt said the dredging campaign was progressing as planned and remained on track. ‘‘This is part of our annual maintenance dredging programme, which has been brought forward this year due to earlier-than-usual infill.’’ He said sediment removed during dredging was being disposed of at a consented offshore maintenance disposal ground, in line with the port company’s resource consent requirements.…