Three bridges that cross the Rangitata Diversion Race (RDR) on Inland Scenic Route 72 (Arundel Rakaia Gorge Road) will be closed from Monday 5 October as new bridges are built that can withstand heavy vehicles over 44 tonnes.

Work to demolish and replace the three RDR bridges is expected to take two months, with work wrapping up before Christmas.

Bridges 233 and 234 south of Staveley as well as Bridge 232 south of Mt Somers will be closed to traffic while they are demolished and replaced, however all local roads will remain open with detours in place. Route 72 will be open and traffic will have access to the two townships.

All three bridges are due for replacement and the Council is using this opportunity to upgrade their weight capacity which would allow trucks carrying 44 tonnes or more to cross them. Currently, heavy vehicles this size cannot use the bridges and are unable to access roads west of the bridges.

Council Infrastructure Services Group Manager, Neil McCann says the $1.8 million upgrades will make a significant difference for heavy vehicle operators and the businesses who rely on them in this area of the district.

"Feedback from our road reference groups and transport operators over the years has highlighted the impact these current weight restrictions have on their productivity, and we are really pleased to be delivering a solution that will open up this area and support growth.

"The new bridges will be a fantastic upgrade for our community but we understand the detours will create some disruption. We are doing everything we can to minimise this as much as possible and appreciate residents' patience throughout this time," Mr McCann adds.

To mitigate disruption, the Council has designed the construction programme in a way that reduces the duration and length of closures as much as practicable, meaning the bridges will all close and reopen on different dates.

The closures and detours (for cars and light vehicles) for each bridge are:

• ​Bridge 234 (Staveley Bridge) - Expected closure 5 October - 13 November

Detour via Springburn Bushside Road, Ashburton Staveley Road and vice versa.

• ​Bridge 233 (Prices Road Bridge) - Expected closure 12 October - 6 November

Detour via Tramway Road, Gates Road, Lochheads Road and vice versa

• ​Bridge 232 (Surrey Hills Bridge) - Expected closure 19 October - 4 December

Detour via Anama Station Road, Anama Valetta Road, Anama Cavendish Road and vice versa.

Heavy vehicles will be detoured via Mayfield Valetta Road, Thompsons Track and Ashburton Staveley Road and vice versa from 12 October until 4 December.

Detours will be signposted.