Options for shoring up an old landfill site that is slowly being eroded will be considered by Christchurch City Councillors next week.
The Bexley Landfill operated for nearly 30 years before it was closed in 1984 and capped.
The earthquakes though have damaged the capping material and caused an area of the landfill, near the Bridge Street bridge,to subside by up to a metre.
Due to the subsidence, some of the old landfill material is gradually being exposed by erosion along the western side of the Avon-Heathcote Estuary edge.
About 600 metres of the foreshore now requires remediation to prevent the old landfill material being washed into the estuary in a big storm event.
On Wednesday, 26 February, the Three Waters Infrastructure and Environment Committee will consider a report which recommends the Council spends nearly $1.5 million on containing the landfill by layering different size rocks over the area.
The rocks would form a natural beach, containing landfill material and protecting the foreshore. The smaller size rocks would keep waste in and water out, while the large outer layer rocks would provide protection from waves.
Staff favour this option because the work can be done quickly and with minimal disturbance to the sensitive coastal environment.
They did, at the request of elected members, look at the possibility of using steel sheetpiling to contain the landfill. However, they ruled that option out because of the cost, installation challenges and the sensitive nature of the foreshore area.
Staff say the only other practicable option would involve spending approximately $3.4 million on constructing robust bank edge protection. This would provide protection to the landfill site edges for the next 50 years but has a higher initial cost.