Council chooses fix over replace for sewer system

17/03/2017 9:00 a.m.

​At its March meeting, Opotiki District Council voted to undertake a significant rehabilitation programme on the town's sewers in order to address the ongoing issues with an aging and worn out system. 

Opotiki​ Mayor, John Forbes said that the discussion and decision marked the end of a long and thorough process and he was pleased to have an outcome to service Opotiki residents for the long term.

"Council is well aware that the sewers under the Opotiki township are not working as they should. They were first installed in the 1950s and I understand that a lot of them were brought in second hand from Auckland at the time. So even just a couple of years ago, when we had a big downpour or a few days of storms, we had port-a-loos out in some streets to deal with the fact that people couldn't even flush their toilets. That's clearly not okay so we have been working on a solution for several years now.

"This process and its outcomes have been part of our long term plans and annual plans. We have invested heavily in the investigation because we knew we would need the right information and all the facts before we had to make the hard, and expensive, decision we made at Council this week," Mr Forbes said.

The investigation work has been carried out in a number of phases including CCTV and smoke investigations and physical inspections, recording of rainfall, river levels and associated flows through the sewer network.

It became very clear that there are a number of issues with the system including ground movements and the build-up of sediment in pipes, but one of the biggest contributors is direct inflow into the sewer system. The project team undertook a pilot scheme in the area north of Elliot Street, to 'find and fix' some of the defects to see what happens to the overflow problem in that area.

Initial estimates indicate that the work done reduced inflow by up to 70% which is 17% of the total sewer flow generated.

Extrapolating these repairs (along with some necessary replacement work and other costs) was compared to the cost of replacement using one of two alternative sewerage solutions – Pressure Sewer Systems and Vacuum Systems.

Both the full replacement options were significantly more expensive, one almost double and the other almost triple the cost of a renewal and rehabilitation option.

"Council talked through not just the costs, but some of the other factors that made our current system the preferred option such as maintenance and ongoing operation, how it may impact on our treatment system, what changes would be needed at each address that would have to be done by landowners, and all those factors.

"We are very aware that ratepayers will carry this burden for many years to come so we wanted to make the responsible choice for this and future generations.

"We have elected to do a thorough renewal of our current gravity sewer system which will include repairs, relining and replacement as necessary over the next few years. We are looking at how we spread that cost through our long term plan," Mr Forbes said.

The 2015-2025 Long Term Plan identified an expenditure of $12.5m from 2015/16 to 2019/2020. Approximately $0.5m has been spent to date on investigations and the Find and Fix programme. The total estimate at this stage, subject to final CCTV results will be $12.8m which is very close to initial budgets. At the meeting Council agreed to the $4.1m expenditure with the remaining $8.2m to go through the Long Term Plan process.

Read more on the history of the Sewerage Project.

Page reviewed: 05 Jun 2019 1:07pm