Ageing bridges cause ‘huge challenge’ as funding falls short

Nicole Mathewson Reporter from The Press

By David Hill, Local Democracy Reporter

Ageing bridges across North Canterbury will cost millions to replace, but councils can't afford to do the work alone.

Hurunui District Council chief executive Hamish Dobbie said his district alone has 286 bridges and culverts, with around one-third needing to replaced over the next 30 years.

‘‘We probably need about about $3 million a year just for bridges,’’ he said.

‘‘At the moment we get $200,000 a year for bridge maintenance.’’

The bridges in need of upgrades include Conway River bridge on Inland Road, estimated to cost around $20 million, to smaller bridges and culverts expected to cost less than $1 million.

The Conway River bridge replacement has been listed in the Canterbury Regional Land Transport Plan with a fourth equal priority ranking with several projects, including the Pages Road bridge in Christchurch.
But no date has been set.

The Hurunui District Council’s entire 2024/25 roading programme was $14 million, which included a $5 million Waka Kotahi New Zealand Transport Agency subsidy.

The ratepayer was footing the remaining $9 million.

‘‘As a country we need to have a mature conversation about infrastructure funding and some of those conversations will be a bit more confronting,’’ Dobbie said.

He said most of the bridges and culverts around New Zealand were built in the 1950s to 1970s, meaning they were starting to come to the end of the life.

But there has been significant underfunding in infrastructure since then, with councils left to pick up the slack, he said.

The Conway River bridge was on an important route, with oversized vehicles having to use Inland Road if they were unable to use the State Highway 1 tunnels south of Kaikōura.

‘‘It is a local bridge we fund for the benefit of the country,’’ Dobbie said.

He said he would like the ability to loan fund bridge replacement work, provided Waka Kotahi contributed its 52% share.

Waka Kotahi director regional relationships James Caygill said the agency was aware of the problem.

‘‘It is a huge challenge. Every council has bridges they want to work on.’’

He said bridge replacement was funded separately from maintenance, but it was a matter of establishing how urgent the work was.

A Waka Kotahi spokesperson said the agency managed 4751 bridges and large culverts on the country’s state highways (based on 2023 numbers).

The agency has an ‘‘end-of-life’’ bridge replacement programme, with nine state highways bridges being replaced in the 2024-27 National Land Transport Programme, including two in Canterbury.

‘‘It is extremely difficult to predict the exact ‘end-of-life’ dates for a bridge for a variety of factors, and hence predictions in the 10, 20 and 30 year ranges often come with significant margins of error,’’ the spokesperson said.

Waka Kotahi has a bridge inspection process to ensure state highway bridges and culverts were inspected every two years.

‘‘In some cases this may mean placing speed or weight restrictions on some bridges, at which point operators of over-weight vehicles may have to use alternative routes better suited to them.’’

Speed and weight restrictions were only employed as a last resort, the spokesperson said.

■ LDR is local body journalism co-funded by RNZ and NZ On Air.