Paekākāriki Hill Road culverts

A culvert is typically a structure that facilitates water flow under some form of obstruction to keep a stream connected. Here, the culverts connect two streams to the Pāuatahanui inlet under Paekākāriki Hill Road.

We became aware of structural concerns to these culverts within the road lanes in late 2022. Subsequent inspections by structural engineers identified there was no immediate safety issues with the road across either culvert. But, they recommended work be carried out to the culverts within three years.

We want to strengthen the resilience of the road and ensure the streams continue to feed into Pāuatahanui Inlet, which is the largest relatively unmodified estuarine in the southern North Island.

One of our key community outcomes and a strategic priority is having a healthy harbour and catchment.

We’re aiming to carry out the physical work for one culvert this financial year, and the remaining culvert in the next. The order is yet to be confirmed. This is to minimise disruption to residents and the wider community.

Contract for design and investigation

We awarded the contract for the investigation and design for the two culverts to our preferred contractor in December 2024.

Our contractor will be providing the following over the course of this project:

• Gap analysis – to review current data and any further information that may be required
• Investigation report - summarising any missing data or recommendations for additional work such as inspections
• Investigation recommendations – outlining the recommended additional work to be completed to assist with progressing the design work
• Recommendation report – outlining various options for repair or replacement of the culverts including high-level costs for each option.
• Concept design to provide a high-level design solution that will be further refined in the later design stages
• Detailed design – development of the concepts into a final design solution
• Construction drawings and documentation
• Consenting submitted to relevant regulatory agencies
• Construction tender documents for physical works.

Over the course of the project these deliverables may change.

As of March 2025, we've received:

• Gap analysis report, which informs of any missing data from previous investigations
• Investigation report detailing further investigation options
• Further investigation report, which outlines the additional investigation work we need to conduct to progress the design.
• Hydrological assessments that confirm water volume and flow speed through the culverts to inform the design.
• Concept designs, which are high-level design drawings which will be developed during the detailed design phase.

Once the work to culvert A has been completed, we should be able to remove the orange “hit sticks” and the speed humps. These are in place to ensure there isn’t any further exacerbation to this culvert.