Structures

The purpose of structures, including bridges, large culverts and retaining walls, is to provide continuous all-weather road access over rivers, streams and uneven terrain, supporting vehicles and ensuring the safety of road users. Structures form a crucial part of Council’s road network, facilitating the movement of people and goods through the district, contributing to an economically productive district. They also serve a key function in environmental and/or emergency events where access around the district is crucial, especially for isolated communities with limited access to the rest of the network.

Tararua District Council has more than 1,800 structures associated with the road network. This includes 394 bridges, 110 large culverts, 1,297 retaining walls, and one pedestrian underpass.

Important activities include:

• Structure inspections; identification, assessment and recording of defect information to enable robust maintenance programming.
• Cyclic patrols; remedying minor structure defects such as blocked deck drains in conjunction with the road patrol.
• Programmed proactive maintenance; completion of maintenance activities to minimise future maintenance costs and extend the life of the asset. This includes; restoring protective coatings, restoring or cleaning deck expansion joints, cleaning around bearings, etc.
• Programmed reactive maintenance; remedying asset defects such as concrete spalling, damaged rails, corroded fastenings, debris build-up, and scour to ensure the asset is maintained in a safe and serviceable condition, while maximising its life and realising the investment made in it.
• Component renewal; replacement of part of the structure, either when damaged beyond effective repair or when assessed to be at the end of its useful life, to extend the life of the structure and/or to minimise future repair costs.
• Full renewal; replacement of the entire structure, either when damaged beyond effective repair or when assessed to be at the end of its useful life.
• Structural strengthening; improvements carried out to increase the structural capacity of the structure (typically a bridge) and ensure the road can accommodate the appropriate vehicle demand.

Bridge Capacity Assesments

Due to the changing vehicle dimension and mass rules, resulting in larger and heavier trucks on the road network, an increasing number of bridge capacity assessments are being completed. This is likely to result in restrictions being applied to additional bridges being limited.

There are currently two Class 1 capacity restricted bridges on Council’s road network. These are posted in accordance with the Heavy Motor Vehicle Regulations 1974, Regulation 11 Protection of Bridges.

Heavy Motor Vehicle Regulations 1974, Regulation 11 Protection of Bridges.

Many of Council’s bridges are nearing the end of their life. A significant number of these bridges are located on low volume roads where alternative routes exist and the economic viability of their replacement needs to be considered. Detailed structural inspections and impact assessments will be completed to inform community discussion regarding the shape of the road network in the future.