BACKGROUND

As part of the maintenance dredging programme for Lyttelton Port, sections of the Lyttelton Inner Harbour are dredged to maintain suitable depths for access to berths. Although the Port's maintenance dredging is effectively an annual programme, the partially enclosed nature of the Inner Harbour means that siltation rates are lower than the main Port approaches in the outer Harbour and dredging is required less frequently.

In 2013, Lyttelton Port of Christchurch (LPC) identified the need for dredging of the No.3 west (No. 3 W) berth pocket and a section of the swing basin offshore from the No.2 to No.7 wharves in the Inner Harbour. In order to characterise the sediments to be dredged in terms of their contaminant status, Cawthron Institute (Cawthron) was contracted to implement pre-dredging benthic sampling and a sediment analysis plan (SAP).