During the construction of the Transmission Gully, the earthworks will generate additional sediment, which has the potential to cause adverse effects in the freshwater and marine receiving environments. As part of the conceptual design of the Transmission Gully project for consenting purposes, erosion and sediment control devices have been proposed to mitigate the potential effects of additional sediment on the freshwater and marine receiving environments. As part of the assessment of effects for the project, the effectiveness of the proposed erosion and sediment control devices at intercepting additional sediment has been estimated. The method that has been used, to undertake this assessment, has been to establish an existing case for sediment yield and then to modify this to reflect the proposed earthworks including the mitigation measured. For this, the Suspended Sediment Yield Estimator (SSYE) has been used.
SKM, 2011. Transmission Gully Project Assessment of Water Quality Effects. Technical Report 15. Sinclair Knight Merz, Wellington. 29 July 2011.