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Unsealed Roads

Hurunui District has a large Roading network of circa 1,500km, around two thirds of which are unsealed. This section highlights how council maintains the unsealed network and what to expect on unsealed roads.

Please refer to the Unsealed Roads Policy for full information.

There are approximately 843.8 km of unsealed roads in the Hurunui District.

Maintenance is carried out by two graders operating permanently across the network, including regular grading at frequencies dependent on the traffic volumes and/or the road topography. When material levels are low, new material is applied to provide a good surface for traffic to run on.

By their nature, unsealed roads cannot be kept in a steady state. Because they are made up of stones mixed with clay or silt fines, just how well they last between grading is very much dependent on the weather. Roads which carry heavy traffic such as logging trucks and milk tankers can also suffer increased wear.

The indicative grading schedule is regularly updated. Prior to the road being graded it will be inspected and a decision will be made whether the road is graded in line with the schedule or not. It is worth noting that grading is more of an art than a science, knowing what type of grading needs to happen and when. The techniques used can be very different, conditional on the weather and ground conditions at the time.

Different roads require grading at different frequencies dependent on their use and overall condition. Roads are assessed regularly, those with less traffic are graded less frequently and those with more traffic may require more frequent grading. The road surface should remain in good condition for about a week and a half after grading depending on weather conditions, traffic volumes and driver behaviour.

Optimum Grading conditions

The best time to restore the shape of the road by heavy maintenance grading is when the road is damp as it will compact the road to a dense surface. Spring and autumn are ideal times. Grading in winter is avoided where possible as it often results in slushy conditions that are unsafe for motorists and take a long time to dry out. Grading in mid-summer is avoided as cutting into a dry hard surface leaves a layer of loose material that reduces to dust and can be blown away or get thrown off by traffic.

Most of our unsealed roads carry fewer than 100 vehicles per day.

Dust and a loose surface can be part of the lifecycle for unsealed roads. Precluding sealing or dust suppression, little can be done to combat this especially during hot summer days. Used engine oil is not permitted under Ecan’s Canterbury Land and Water Regional Plan (CLWP) s5.18. Dust Suppressants

HDC Policy :

  1. Council does not provide dust suppression for unsealed roads, but will provide a pathway for property owners to fund and undertake dust suppression.
  2. Council will only seal gravel roads in accordance with the approved Road Operations and Renewals programs, but will consider applications for seal extensions on unsealed roads, where:
    a. The costs of sealing, including design and process costs, are met by the applicant;
    b. The design and physical works meet Council standards;
    c. The seal extension is appropriate in the surrounding environment; and
    d. Traffic volumes.

Please refer to the full policy document

YOU’VE SEEN THEM AND HATE THEM, BUT HOW ARE CORRUGATIONS MADE?

One of the most frustrating characteristics of unsealed roads is the occurrence of corrugations. These are typically formed when drivers abruptly accelerate or brake.

Corrugations occur when vehicles travel at speed over a soft surface. The speed of travel is important because this can and does cause a ripple in the surface. When vehicles pass over this ripple, they might experience a bounce. As the vehicle lands, the impact causes compression on the surface of the road. The next wheel will follow that pattern and the problem keeps growing.

Corrugations also tend to form on the inside of uphill corners where drivers accelerate.

Once established, corrugations run deep, perhaps as far down as 4 to 5 metres, so Council’s contractor can grade out some of the corrugations, but grading too deep can also affect the substructure of the road, allowing water to seep in, causing large potholes, soft areas and loose shingle, really all the contractor can do is a short-term fix to grade them over.

There’s no real fix to corrugations other than slowing down, and running lower tyre pressures.

Potholes are more common in the damp weather where the road is flat, or there is a hollow or corrugation. Vehicle tyres splash the “fines” out and potholes develop.

The Council’s contractor works within the available budget to keep roads shaped with a high camber to allow water to run off to the sides of the road.

In some areas the water cannot run off the road and we’d like these to be reported so that a list can be created and addressed as budget becomes available.

Contact Council, or Snap Send Solve it.

Unsealed roads are inspected regularly by Council staff as well as the Council’s Road Maintenance Contractor, to determine whether additional maintenance is required.

Priority is given to the existing maintenance programme and areas the Council has agreed require extra attention. Council staff monitor the contracts and audit the standard of work.

Contact Council, or Snap Send Solve it, if you have a concern about the state of any unsealed road.

Three simple rules for driving on unsealed roads:

Accelerate slowly

Do not spin your wheels, especially through gear changes when entering onto unsealed roads from a driveway or another road. Ease off the accelerator where there are already corrugations.

Slow down

You will find less dust and less loose shingle. This will also help to reduce dust nuisance for adjacent residents.

Avoid hard braking

This will reduce potholes and intersection corrugations. Report any intentional damage to the Council or Police.

Unsealed Roads policy

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