Godwits and worm mounds: successful pipeline consenting

The Nelson Regional Sewerage Business Unit’s (NRSBU’s) decision to proceed with a 2.6km, 800mm diameter HDPE pipeline crossing the Waimea Inlet to their Bell Island wastewater treatment plant faced significant consenting hurdles due to the sensitive estuarine environment and cultural concerns for the estuary crossing. This paper describes the consultative approach taken to accommodate these issues and concerns, to achieve a pragmatic and cost effective consent outcome. Technical aspects of the project are also described.

Submissions to the consent application covered a wide range of issues. Key concerns included Iwi cultural objections to the laying of a sewer pipeline under the estuary, the potential disturbance to five bird species of international importance and ecologically significant areas of worm mounds, eel grass and sponge gardens traversed by the pipeline. Submissions sought to restrict the construction season from May through to August to avoid disruption to the bird’s breeding season and the Summer/Autumn fattening of the Bar-tailed Godwit, before its annual migration to Alaska. Submitters expressed a strong desire for trenchless construction, by directional drilling, as this was perceived to present the lowest environmental impact. The studies and technical considerations that lead to acceptance by all of the NRSBU’s preferred and lower cost open trenching methodology are described.