Location: Pakiri Coast, New Zealand
Type of Project: Biological Review
Client: Kaipara Limited, New Zealand
The “Jumbo” trailer hopper dredger (33,000 m3 capacity), Vasco Da Gama.
Kaipara Limited commissioned ASR Ltd to undertake a review of the biological impacts and recovery times due to trailer-suction dredging, shellfish dredging (e.g. scallops, oysters), and trawling.
Kaipara Limited have applied for a coastal permit to suction dredge up to 2 million cubic metres of sand from the sea floor over an area of approximately 480 km2 in the upper Hauraki Gulf. The dredging has been undertaken between 25 and 50 m depth in the general vicinity of the Pakiri Coast. The permit application allowed extraction of sand over a 35 year period. Detailed studies of the ecological effects of the proposed dredging have been undertaken for the consent application. The review presented considered international studies of the effects of dredging and trawling to provide supplementary information on the biological impacts and seabed recovery time that would be expected due to the suction dredging proposed by Kaipara Limited.
The brief included shellfish dredging and trawling because the impacts of trailer suction dredging have been previously been likened to these practices. The penetration depths of dredging and trawling equipment were similar to those expected during sand extraction off Pakiri. In addition, there was an abundance of international literature related to these type of fishing techniques compared to that pertaining to suction dredging – the majority of biological investigations pertaining to sediment dredging focused on dredge disposal or on cases where far greater volumes were removed from the seabed in comparison to the technique proposed by Kaipara Limited.« Download Project PDF