The outer banks of the closed landfill in Otautau are at risk of being eroded due to the position of the Aparima River and the potential for more intense river flows due to future climate change events.
Environment Southland does not actively manage aggregates or fairways on this river, and the cost to relocate the potential hazardous landfill from the river environment to an approved landfill was cost prohibitive to Southland District Council.
The initial costing exercise by e2Environmental found that the cost to remove land fill material to an approved landfill near Winton was tens of millions of dollars compared to a few million to protect in place.
e2Environmental was engaged to develop a hydraulic model of the river to review maximum design flow velocities and scour depths in several flood scenarios to assess and recommend preliminary designs for revetment extent, depth and size. This modelling also looked at side streams that cross the site and assessed the potential for these streams to scour the landfill.
We then assisted the Selwyn District Council in selecting a source of suitable rock to meet their budgets.
Detailed design considered the potential for contaminated soils, staging of works, fish passage, and consenting requirements of Environment Southland’s Land and Water Regional Plan.
Project manager(s)
Daniel McMullan
Services involved:
