Work on permanent fix for MacKays Crossing
TRANSIT NEW ZEALAND WELLINGTON REGIONAL OFFICE
2 April 2008
Work underway on permanent fix for MacKays Crossing
Transit has begun work on a permanent fix for ongoing pavement problems at MacKays Crossing on State Highway 1 north of Wellington.
Wellington Regional Manager Graham Taylor says the contractor began laying an asphalt surface over the two-lane section of the highway south of the overbridge last night, where recent repair work did not withstand heavy rain last weekend.
Two different layers of asphalt will provide a level, waterproof road surface. Mr Taylors ays he expects the work will be completed by the end of next week, depending on the weather.
“The end result of this asphalting will be that once we have finished, we don’t anticipate any further work will be required over this section of the highway. It will then become part of our regular maintenance and resealing programme and, because it is asphalt, this maintenance and resealing can be carried out overnight when there is the least disturbance to motorists.”
He says the sealing work is being carried out at night between 7.00pm (or later if traffic is still heavy) and 5.30am. The current speed restriction is 70km/h.
Further north, some additional repairs are required on the four-lane section, which can be completed without interruption to the traffic. No further work is then anticipated until next year when Transit will carry out some minor shape correction to an area affected by peat settlement. This is something that was anticipated in the design of the project and was provided for in the construction contract.
Mr Taylor says he expects conditions at MacKays Crossing will have vastly improved already and further problems at the two lane section will no longer be an issue.
QUESTIONS AND ANSWERS
Why did potholes appear in new seal at the weekend?
Transit believes that the potholes occurred because the new seal proved not to be waterproof. The end result was that the chip came away from the bitumen, which was not expected. We are still investigating why the seal wasn’t waterproof, but one possibility is that there was an issue with the chip used in the seal, which meant it didn't adhere to the surface.
What was done last night?
Last night, the contractor began putting a thin layer of asphalt down over the pavement at the southern end of MacKays Crossing. This is a levelling layer of asphalt to provide a smoother, even surface, which is waterproof. Once this first layer is finished then a final layer of asphalt will be laid over the top.
Was the work finished?
Fifty metres in the northbound direction will be laid this evening after 7.00pm. The rest of the area was asphalted overnight.
What was done on Monday (temporary work)?
Work to temporarily repair the potholes was undertaken on Monday to address the problems on the road until work providing a full solution could be undertaken.
What about the shape correcting work?
The reason shape correction work is required is because the project is built on peak soil. There is an area where the approach to the bridge is settling slightly, causing the road to lose shape. This was something we anticipated in the design of the project and provision for correcting this was made in the construction contract. This is why the contract does not actually conclude until 2009. This work is likely to take place between October 2008 and March 2009 and will be undertaken overnight to minimise any potential delay to traffic.
How much was sealed last night?
A section of 1km on either side of the SH1 was sealed with asphalt last night.
Is that the end of the work??
All work at the southern end of the project (the two-lane section) is likely to be completed by the end of next week. Further work is required for the northern end, including the shape correction area. Repairs will be carried out in areas where there is loose chip at the northern end of the project, with a final coat of seal for this section likely to be done next sealing season, which runs from October 2008 until mid-March 2009. The shape correction work is likely to be carried out at the same time.
Why did we use asphalt?
Asphalt has now been used across the two-lane section in this instance because it could level the road surface, waterproof it, is driveable within an hour of being laid and could be laid overnight when traffic volumes are much lower causing no further inconvenience to road users.
This said, chip seal was chosen for the site because it was the most flexible for the peat soil the project was built on. However, high traffic volumes and significant heavy rain combined to created unexpected problems at MacKays.