Reports obtained by the Otago Daily Times show the Dunedin City Council remains in the dark about the condition of key parts of the Three Waters network and a significant, detailed assessment will be needed.
The council has requested proposals for a comprehensive assessment programme of its highly critical pipelines.
Packages of work will cover assessment of about 74km of water supply pipes, 9km of wastewater pipes, 9km of stormwater pipes and 3km of water supply reservoir tunnels and pipes.
The work would be aimed at determining when key pipes should be replaced and identifying high-level remedial action to be undertaken to prevent premature pipeline failures, the council said when it invited tenders.
This could provide evidence to influence strategic direction or spending, the council said.
It also highlighted there were gaps in its knowledge.
The condition of much of the council’s piped network was ‘‘not well understood and there is limited historical condition assessment data available for some of the pipelines’’.
Engineering consultancy WSP also pointed this out in 2022.
‘‘The actual condition is not well understood,’’ the firm said.
‘‘A comprehensive and planned condition-assessment programme has not been developed or implemented.’’
The council started with a top-10 list of pipelines considered highly critical.
There were then discussions and workshops and the number ended up at 13.
Each was assigned an average priority score, based on age-based condition grades and a multi-criteria assessment of how critical the assets were considered to be.
A pipeline connecting Taieri bores to the Wingatui tank water supply was at the top of the priority list.
Parts of the line were made of asbestos cement and much of the line was assessed as priority 1 for inspection.
The ODT has previously reported the asbestos did not pose a health risk to consumers.
The line was installed in 1956.
A water pipeline from the Silver Stream to the Wingatui tank, installed in 1950, was almost entirely assessed as priority 1.
The line mainly consists of asbestos cement or concrete.
The original pipeline for the Dunedin main interceptor sewer was installed in 1903.
Parts of the line were replaced or added to until the year 2000.
An original pipeline for the Portobello Rd stormwater pump station catchment was installed in 1900.
It is intended a comprehensive condition-assessment programme will be implemented by the end of June 2027.
